A nickel-cobalt-aluminum ternary positive electrode material precursor, a preparation method and application thereof

Abstract

The application discloses a nickel-cobalt-aluminum ternary positive electrode material precursor and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The preparation method of the nickel-cobalt-aluminum ternary positive electrode material precursor comprises the following steps: (1) adding a nickel source, a cobalt source and an aluminum source into deionized water to prepare a mixed solution, adding a complexing agent and a precipitating agent into the mixed solution, carrying out a reaction, carrying out solid-liquid separation, drying, and obtaining a solid product; (2) adding the solid product into modified graphene slurry, carrying out first ball milling, carrying out a hydrothermal reaction, carrying out second ball milling, drying, and crushing to obtain the nickel-cobalt-aluminum ternary positive electrode material precursor; the modified graphene slurry comprises the following components: a fluorine-containing silane coupling agent, a soluble boron-containing compound, a surfactant, graphene and anhydrous ethanol. The prepared nickel-cobalt-aluminum ternary positive electrode material precursor has good structural stability and consistency, and can significantly improve the electrical performance and cycle performance of a lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a nickel-cobalt-aluminum ternary cathode material precursor, a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in aerospace, intelligent devices, security products and electric vehicles due to their high energy density, long cycle life and low environmental pollution. The cathode, as the most critical component, determines the electrochemical performance of lithium ion batteries.

[0003] Nickel-cobalt-aluminum (NCA) ternary battery material as a new type of cathode material has been considered as a new generation of cathode active material for future power lithium batteries due to its advantages in resource occupation, cost performance and safety. At present, the nickel-cobalt-aluminum ternary cathode material is usually prepared by co-precipitation and solid-phase sintering method. The nickel-cobalt-aluminum ternary cathode material synthesized by the above method usually has poor rate performance and cycle life.

[0004] CN107799749A discloses a spherical nickel-cobalt-aluminum precursor and a preparation method thereof, comprising the following steps: (1) simultaneously adding a nickel-cobalt salt mixed solution and an ammonium oxalate solution into water to obtain a spherical oxalate precursor solution, and adjusting the pH value of the reaction system to 8.0-8.5 with concentrated ammonia water; (2) adding an aluminum salt solution and a strong alkali solution into the spherical oxalate precursor solution obtained in step (1) to obtain a spherical nickel-cobalt-aluminum precursor. The 1C discharge specific capacity of the cathode material prepared therefrom is only about 160 mAh / g, and the cycle retention rate is only about 85% after 50 cycles.

[0005] CN110127777A discloses a wet method of doping zirconium concentration gradient nickel-cobalt-aluminum ternary precursor and a preparation method thereof. The method adopts complexing control crystallization co-precipitation method, and the soluble salt aqueous solution of nickel-cobalt-zirconium and the sodium hydroxide solution are co-precipitated in the presence of ammonia complex in a reaction kettle to prepare small particle size zirconium-doped nickel-cobalt binary hydroxide. Then, the sodium metaaluminate solution is added into the reaction kettle to obtain the zirconium-doped nickel-cobalt-aluminum ternary precursor, and the proportion of the inner core to the outer layer metal changes uniformly. Increasing the solid-liquid ratio of the solution in the reaction kettle can obtain a ternary precursor with narrow particle size distribution and good particle morphology. Although the cycle performance is good, the 1C discharge specific capacity is only about 186 mAh / g, which still needs to be improved. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a nickel-cobalt-aluminum ternary cathode material precursor, a preparation method and application thereof. The prepared nickel-cobalt-aluminum ternary cathode material precursor has good structural stability and consistency, which can significantly improve the electrical performance and cycle performance of lithium ion batteries.

[0007] To achieve the above object, the technical scheme adopted herein is:

[0008] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor, comprising the following steps:

[0009] (1) adding a nickel source, a cobalt source, and an aluminum source into deionized water to prepare a mixed solution, adding a complexing agent and a precipitating agent into the mixed solution, reacting, solid-liquid separation, drying, and obtaining a solid product;

[0010] (2) adding the solid product into a modified graphene slurry, first ball milling, hydrothermal reaction, second ball milling, drying, and crushing to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor;

[0011] The modified graphene slurry comprises the following components: a fluorine-containing silane coupling agent, a soluble boron-containing compound, a surfactant, graphene, and anhydrous ethanol.

[0012] In this paper, the nickel-cobalt-aluminum precursor is coated in the modified graphene slurry, and then first ball milling, hydrothermal reaction, and second ball milling are performed, which can uniformly coat the nickel-cobalt-aluminum precursor, effectively avoid graphene agglomeration, thereby avoiding uneven coating, effectively improving the structural stability and consistency of the material, and significantly improving the electrical conductivity and cycle life.

[0013] Through the above-mentioned graphene slurry containing fluorine and boron, and through specific first ball milling, hydrothermal reaction, and second ball milling, part of the fluorine and boron can be doped into the nickel-cobalt-aluminum precursor, which can inhibit polarization during use, reduce impedance, and improve the diffusion rate of lithium ions, while the other part of the fluorine and boron plays a role in stabilizing the structure, thereby significantly improving the electrical conductivity and cycle life.

[0014] In this paper, the elements are doped in the form of modified graphene slurry coating, which has the advantages of simple preparation method and low cost.

[0015] The inventors found in further exploration and research that if graphene is used for coating alone (that is, the slurry does not contain other substances), on the one hand, it is difficult to uniformly coat the nickel-cobalt-aluminum precursor, and it cannot effectively inhibit the agglomeration of graphene, and on the other hand, the use of single graphene coating has limited improvement in electrical performance and cycle performance of the material.

[0016] The inventors further explored the influence of the doped elements on the performance, and found that in the specific system of this paper, if boron elements or fluorine elements are doped alone, the improvement in electrical performance and cycle performance is limited, and the doping of double elements can simultaneously play the doping role of both elements, thereby significantly improving the electrical performance and cycle performance.

[0017] In an embodiment, the molar ratio of Ni:Co:Al in step (1) is (70-85):(8-20):(4-10).

[0018] In an embodiment, the molar ratio of Ni:Co:Al in step (1) is 78:15:7.

[0019] In an embodiment, the nickel source is one of nickel sulfate, nickel nitrate, nickel chloride, nickel acetate, and nickel oxalate.

[0020] In an embodiment, the cobalt source is one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt oxalate.

[0021] In an embodiment, the aluminum source is one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate, and aluminum oxalate.

[0022] In an embodiment, the complexing agent is an aqueous ammonia solution.

[0023] In an embodiment, the precipitating agent is a sodium hydroxide solution.

[0024] In an embodiment, the reaction conditions in step (1) are: pH value is 10.5-13, reaction temperature is 45-60°C, ammonia value is 10-18 g / L.

[0025] In an embodiment, the hydrothermal reaction conditions in step (2) are: temperature is 120-180°C, reaction time is 2-10 h.

[0026] In an embodiment, the modified graphene slurry includes the following components in mass parts: 0.1-0.6 parts of a fluorine-containing silane coupling agent, 0.2-1 parts of a soluble boron-containing compound, 1-4 parts of a surfactant, 3-10 parts of graphene, and 30-50 parts of anhydrous ethanol. In particular, when the components in the graphene slurry are combined in the above specific mass parts, the improvement in electrical performance and cycle performance is more significant.

[0027] In an embodiment, the modified graphene slurry includes the following components in mass parts: 0.1-0.4 parts of a fluorine-containing silane coupling agent, 0.4-1 parts of a soluble boron-containing compound, 1-3 parts of a surfactant, 3-8 parts of graphene, and 35-50 parts of anhydrous ethanol.

[0028] In an embodiment, the soluble boron-containing compound is boric acid.

[0029] In an embodiment, the surfactant is polyvinylpyrrolidone.

[0030] In an embodiment, the fluorine-containing silane coupling agent is one of 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane.

[0031] In an embodiment, the method for preparing the modified graphene slurry is as follows:

[0032] S1, graphene and a surfactant are added to anhydrous ethanol and stirred uniformly to obtain a graphene mixture;

[0033] S2, the graphene mixture is heated to 55-70℃, a fluorine-containing silane coupling agent and a soluble boron-containing compound are added, and ultrasonic treatment is performed at 300-800W for 25-50min to obtain a modified graphene slurry.

[0034] In an embodiment, the first ball milling is performed at a speed of 400-800rpm for 0.5-2h, and the ball-to-material ratio is (3-8):1.

[0035] In an embodiment, the second ball milling is performed at a speed of 400-800rpm for 4-10h, and the ball-to-material ratio is (8-15):1.

[0036] The present disclosure also provides a nickel-cobalt-aluminum ternary cathode material precursor prepared by the above method.

[0037] The present disclosure also provides a nickel-cobalt-aluminum ternary cathode material prepared by mixing and sintering a lithium source and the above nickel-cobalt-aluminum ternary cathode material precursor.

[0038] The present disclosure also provides a use of the nickel-cobalt-aluminum ternary cathode material in the preparation of lithium batteries.

[0039] The beneficial effects of the present application are as follows: (1) The present application can uniformly coat the nickel-cobalt-aluminum precursor by adding the nickel-cobalt-aluminum precursor to the modified graphene slurry, and then performing the first ball milling, hydrothermal reaction and second ball milling, which can effectively avoid the agglomeration of graphene, thereby avoiding uneven coating, effectively improving the structural stability and consistency of the material, and significantly improving the conductivity and cycle life; (2) The part of fluorine and boron can be doped into the nickel-cobalt-aluminum precursor by coating the solid product with the graphene slurry containing fluorine and boron, and then performing the specific first ball milling, hydrothermal reaction and second ball milling, which can inhibit the polarization during use, reduce the impedance value, and improve the diffusion rate of lithium ions, while the other part of fluorine and boron plays a role in stabilizing the structure, thereby significantly improving the conductivity and cycle life; (3) The present application has the advantages of simple preparation method and low cost by incorporating elements in the form of modified graphene slurry coating; (4) In the present application, if the graphene is used for coating alone (that is, the slurry does not contain other substances), on the one hand, it is difficult to uniformly coat the nickel-cobalt-aluminum precursor, and cannot effectively inhibit the agglomeration of graphene, on the other hand, the use of single graphene coating has limited improvement on the electrical performance and cycle performance of the material, and the double-element doping can simultaneously play the role of two-element doping, thereby significantly improving the electrical performance and cycle performance. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below in conjunction with specific examples and comparative examples, which are intended to understand the content of the present application in detail, rather than limiting the present application.

[0041] In the present application, the specific dispersion and stirring treatment method is not particularly limited.

[0042] In the present application, unless otherwise specified, the parts are all weight parts.

[0043] The reagents or instruments used in the present application are not specified by the manufacturer, and are all conventional products that can be obtained by purchase.

[0044] Example 1

[0045] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor, comprising the following steps:

[0046] (1) 0.3 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.6 parts of boric acid, 2 parts of polyvinylpyrrolidone, 6 parts of graphene, 41.1 parts of anhydrous ethanol are weighed;

[0047] (2) graphene, polyvinylpyrrolidone are added to anhydrous ethanol, stirred uniformly, to obtain a graphene mixture, the graphene mixture is heated to 60℃, 3,3,3-trifluoropropyl trimethoxysilane and boric acid are added, and ultrasonic treatment is carried out at 500W for 40min to obtain a modified graphene slurry;

[0048] (3) nickel nitrate, cobalt nitrate and aluminum nitrate are used as raw materials, and the molar ratio of Ni:Co:Al is 78:15:7; the nickel nitrate, cobalt nitrate and aluminum nitrate are added to deionized water, wherein the water material ratio is 4:1, and a mixed solution is prepared; 10wt% sodium hydroxide solution is added, and the pH is adjusted to 11; 10wt% ammonia solution is added to adjust the ammonia value to 15g / L; the reaction is carried out at 50℃ for 12h; solid-liquid separation is carried out; and drying is carried out to obtain a solid product;

[0049] (4) the solid product is added to the modified graphene slurry, wherein the mass ratio of the solid product to the modified graphene slurry is 1:5; first ball milling is carried out; hydrothermal reaction is carried out at 150℃ for 6h; second ball milling is carried out; drying is carried out; and crushing is carried out to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor.

[0050] In this embodiment, the ball milling speed of the first ball milling is 600rpm, the ball milling time is 1h, and the ball material ratio is 5:1.

[0051] In this embodiment, the ball milling speed of the second ball milling is 600rpm, the ball milling time is 6h, and the ball material ratio is 10:1.

[0052] Example 2

[0053] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor comprises the following steps:

[0054] (1) 0.1 parts of 3,3,3-trifluoropropyl methyl dimethoxysilane, 1 part of boric acid, 1 part of polyvinylpyrrolidone, 10 parts of graphene, and 37.9 parts of anhydrous ethanol are weighed;

[0055] (2) graphene, polyvinylpyrrolidone are added to anhydrous ethanol, stirred uniformly, to obtain a graphene mixture, the graphene mixture is heated to 60℃, 3,3,3-trifluoropropyl trimethoxysilane and boric acid are added, and ultrasonic treatment is carried out at 500W for 40min to obtain a modified graphene slurry;

[0056] (3) taking nickel nitrate, cobalt nitrate and aluminum nitrate as raw materials, adding the nickel nitrate, cobalt nitrate and aluminum nitrate into deionized water in a molar ratio of Ni:Co:Al being 70:20:10, wherein the water-material ratio is 4:1, preparing a mixed solution, adding 10wt% sodium hydroxide solution, adjusting the pH to 11, then adding 10wt% ammonia solution to adjust the ammonia value to 15g / L, reacting at 50℃ for 12h, solid-liquid separation, drying to obtain a solid product;

[0057] (4) adding the solid product into modified graphene slurry, wherein the mass ratio of the solid product and the modified graphene slurry is 1:5, first ball milling, hydrothermal reaction at 150℃ for 6h, second ball milling, drying, crushing to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor.

[0058] In this embodiment, the first ball milling speed is 400rpm, the ball milling time is 2h, and the ball-material ratio is 8:1.

[0059] In this embodiment, the second ball milling speed is 400rpm, the ball milling time is 10h, and the ball-material ratio is 8:1.

[0060] Example 3

[0061] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor, comprising the following steps:

[0062] (1) taking 0.6 parts of tridecafluorooctyltrimethoxysilane, 0.2 parts of boric acid, 4 parts of polyvinylpyrrolidone, 3 parts of graphene, 42.2 parts of absolute ethanol

[0063] (2) adding the graphene and polyvinylpyrrolidone into absolute ethanol and stirring uniformly to obtain a graphene mixed solution, heating the graphene mixed material to 55-70℃, adding tridecafluorooctyltrimethoxysilane and boric acid, and ultrasonic treating at 700W for 30min to obtain modified graphene slurry;

[0064] (3) taking nickel nitrate, cobalt nitrate and aluminum nitrate as raw materials, adding the nickel nitrate, cobalt nitrate and aluminum nitrate into deionized water in a molar ratio of Ni:Co:Al being 85:8:7, wherein the water-material ratio is 4:1, preparing a mixed solution, adding 10wt% sodium hydroxide solution, adjusting the pH to 11, then adding 10wt% ammonia solution to adjust the ammonia value to 15g / L, reacting at 50℃ for 12h, solid-liquid separation, drying to obtain a solid product;

[0065] (4) adding the solid product into modified graphene slurry, wherein the mass ratio of the solid product and the modified graphene slurry is 1:5, first ball milling, hydrothermal reaction at 150℃ for 6h, second ball milling, drying, crushing to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor.

[0066] In the embodiment, the first ball milling speed is 800 rpm, the ball milling time is 0.5 h, and the ball-to-material ratio is 3:1.

[0067] In the embodiment, the second ball milling speed is 800 rpm, the ball milling time is 4 h, and the ball-to-material ratio is 15:1.

[0068] Embodiment 4

[0069] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor comprises the following steps:

[0070] (1) 0.1 parts of 3,3,3-trifluoropropyltrimethoxysilane, 1 part of boric acid, 1 part of polyvinylpyrrolidone, 8 parts of graphene, and 39.9 parts of anhydrous ethanol are weighed;

[0071] (2) The graphene and the polyvinylpyrrolidone are added to the anhydrous ethanol and stirred uniformly to obtain a graphene mixture liquid. The graphene mixture is heated to 60°C, and the 3,3,3-trifluoropropyltrimethoxysilane and the boric acid are added. The mixture is ultrasonically treated at 500 W for 40 min to obtain a modified graphene slurry;

[0072] (3) Nickel nitrate, cobalt nitrate, and aluminum nitrate are used as raw materials, and the nickel nitrate, the cobalt nitrate, and the aluminum nitrate are added to deionized water in a molar ratio of Ni:Co:Al of 78:15:7. The water-to-material ratio is 4:1. A 10wt% sodium hydroxide solution is added to adjust the pH to 11. A 10wt% ammonia water solution is added to adjust the ammonia value to 15 g / L. The mixture is reacted at 50°C for 12 h. The solid-liquid separation and drying are performed to obtain a solid product;

[0073] (4) The solid product is added to the modified graphene slurry, and the mass ratio of the solid product to the modified graphene slurry is 1:5. The first ball milling is performed at 150°C for 6 h. The second ball milling is performed. The drying and crushing are performed to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor.

[0074] In the embodiment, the first ball milling speed is 600 rpm, the ball milling time is 1 h, and the ball-to-material ratio is 5:1.

[0075] In the embodiment, the second ball milling speed is 600 rpm, the ball milling time is 6 h, and the ball-to-material ratio is 10:1.

[0076] Embodiment 5

[0077] A preparation method of a nickel-cobalt-aluminum ternary positive electrode material precursor comprises the following steps:

[0078] (1) 0.4 parts of 3,3,3-trifluoropropyltrimethoxysilane, 0.4 parts of boric acid, 3 parts of polyvinylpyrrolidone, 3 parts of graphene, 43.2 parts of anhydrous ethanol;

[0079] (2) The graphene and polyvinylpyrrolidone were added to anhydrous ethanol and stirred uniformly to obtain a graphene mixture. The graphene mixture was heated to 60°C, and 3,3,3-trifluoropropyltrimethoxysilane and boric acid were added. Ultrasonic treatment was performed at 500 W for 40 min to obtain a modified graphene slurry.

[0080] (3) Nickel nitrate, cobalt nitrate, and aluminum nitrate were used as raw materials, and the molar ratio of Ni:Co:Al was 78:15:7. The nickel nitrate, cobalt nitrate, and aluminum nitrate were added to deionized water, with a water material ratio of 4:1, to prepare a mixed solution. A 10wt% sodium hydroxide solution was added to adjust the pH to 11. A 10wt% ammonia solution was then added to adjust the ammonia value to 15g / L. The reaction was carried out at 50°C for 12h. Solid-liquid separation and drying were performed to obtain a solid product.

[0081] (4) The solid product was added to the modified graphene slurry, with a mass ratio of solid product to modified graphene slurry of 1:5. First ball milling was performed at 150°C for 6h. Second ball milling was performed, followed by drying and crushing to obtain a nickel-cobalt-aluminum ternary positive electrode material precursor.

[0082] In this embodiment, the first ball milling was performed at a speed of 600rpm for 1h, with a ball material ratio of 5:1.

[0083] In this embodiment, the second ball milling was performed at a speed of 600rpm for 6h, with a ball material ratio of 10:1.

[0084] Comparative Example 1

[0085] Comparative Example 1 differs from Example 1 in that the raw material ratio of the modified graphene slurry is different, and other aspects are the same.

[0086] In this comparative example, the modified graphene slurry preparation method comprises the following steps:

[0087] (1) 0.05 parts of 3,3,3-trifluoropropyltrimethoxysilane, 1.2 parts of boric acid, 2 parts of polyvinylpyrrolidone, 2 parts of graphene, 44.75 parts of anhydrous ethanol;

[0088] (2) The graphene and polyvinylpyrrolidone were added to anhydrous ethanol and stirred uniformly to obtain a graphene mixture. The graphene mixture was heated to 60°C, and 3,3,3-trifluoropropyltrimethoxysilane and boric acid were added. Ultrasonic treatment was performed at 500 W for 40 min to obtain a modified graphene slurry.

[0089] Comparative Example 2

[0090] Comparative Example 2 differs from Example 1 in that the raw material ratio of the modified graphene slurry is different, and the others are the same.

[0091] In the present comparative example, the preparation method of the modified graphene slurry comprises the following steps:

[0092] (1) take 0.7 parts of 3,3,3-trifluoropropyl trimethoxysilane, 0.1 parts of boric acid, 2 parts of polyvinylpyrrolidone, 11 parts of graphene, 36.2 parts of absolute ethanol;

[0093] (2) add graphene and polyvinylpyrrolidone to absolute ethanol, stir uniformly to obtain a graphene mixture, heat the graphene mixture to 60°C, add 3,3,3-trifluoropropyl trimethoxysilane and boric acid, and ultrasonic treat at 500W for 40min to obtain a modified graphene slurry.

[0094] Comparative Example 3

[0095] Comparative Example 3 differs from Example 1 in that Comparative Example 3 uses graphene slurry instead of modified graphene slurry, and the others are the same.

[0096] The graphene slurry comprises 8 parts of graphene and 42 parts of absolute ethanol.

[0097] Comparative Example 4

[0098] Comparative Example 4 differs from Example 1 in that Comparative Example 4 uses an equal amount of 3,3,3-trifluoropropyl trimethoxysilane instead of boric acid in the modified graphene slurry, and the others are the same.

[0099] In the present comparative example, the preparation method of the modified graphene slurry comprises the following steps:

[0100] (1) take 1.1 parts of 3,3,3-trifluoropropyl trimethoxysilane, 1 part of polyvinylpyrrolidone, 8 parts of graphene, and 39.9 parts of absolute ethanol;

[0101] (2) add graphene and polyvinylpyrrolidone to absolute ethanol, stir uniformly to obtain a graphene mixture, heat the graphene mixture to 60°C, add 3,3,3-trifluoropropyl trimethoxysilane, and ultrasonic treat at 500W for 40min to obtain a modified graphene slurry.

[0102] Comparative Example 5

[0103] Comparative Example 5 differs from Example 1 in that Comparative Example 5 uses an equal amount of boric acid instead of 3,3,3-trifluoropropyl trimethoxysilane in the modified graphene slurry, and the others are the same.

[0104] In the present comparative example, the preparation method of the modified graphene slurry comprises the following steps:

[0105] (1) 1.1 parts of boric acid, 1 part of polyvinylpyrrolidone, 8 parts of graphene, 39.9 parts of anhydrous ethanol were weighed;

[0106] (2) The graphene, polyvinylpyrrolidone was added to anhydrous ethanol and stirred uniformly to obtain a graphene mixture. The graphene mixture was heated to 60°C, boric acid was added, and ultrasonic treatment was carried out at 500W for 40min to obtain a modified graphene slurry.

[0107] Test Example

[0108] 1. The precursors described in Examples 1-5 and Comparative Examples 1-5 were respectively dosed with lithium hydroxide according to a Li / (Ni+Co+Al) molar ratio of 1.04:1, and heated to 800°C in an oxygen atmosphere furnace, and then cooled with the furnace, crushed and sieved to obtain the corresponding positive electrode materials. The positive electrode materials, carbon black and PVDF were prepared into a slurry according to a mass ratio of 88:7:5, coated on an aluminum foil to form a positive electrode sheet, and a lithium ion battery was prepared in an argon-filled glove box with a lithium sheet as the negative electrode. The 1C discharge specific capacity and 1C rate cycle retention rate (%) were tested at room temperature with a current of 3.6A. The test results are shown in the table.

[0109] Table 1

[0110]

[0111] As can be seen from Table 1, the nickel-cobalt-aluminum ternary positive electrode material precursor described herein can significantly improve the electrochemical performance and cycle performance.

[0112] As can be seen from Comparative Examples 1-5, different preparation parameters can affect the performance of the nickel-cobalt-aluminum ternary positive electrode material precursor within a certain range, wherein the ratio of the modified graphene slurry has the greatest impact on the performance, and Example 1 is the best embodiment herein.

[0113] As can be seen from Comparative Example 1 and Comparative Example 1, the modified graphene slurry described herein can significantly improve the electrochemical performance and cycle performance compared to a single graphene slurry.

[0114] As can be seen from Comparative Example 1 and Comparative Examples 2-3, different ratios of modified graphene slurry result in different performances of the prepared precursor. By controlling the ratio of the modified graphene slurry within the range herein, the electrochemical performance and cycle performance can be significantly improved.

[0115] As can be seen from Comparative Example 1 and Comparative Examples 4 and 5, in this text, if a single fluorine-containing silane coupling agent or a soluble boron-containing compound is added, the prepared precursor cannot achieve the effect, and the addition of both significantly improves the electrochemical performance and cycle performance, which also shows that the combination of the two has a certain synergistic effect.

Claims

1. A method for preparing a nickel-cobalt-aluminum ternary cathode material precursor, characterized in that, Includes the following steps: (1) Add nickel source, cobalt source and aluminum source to deionized water to prepare a mixture, add complexing agent and precipitant to the mixture, react, separate solid and liquid, dry to obtain solid product; (2) The solid product was added to the modified graphene slurry, ball milled for the first time, hydrothermal reaction was performed, ball milled for the second time, dried and pulverized to obtain the nickel-cobalt-aluminum ternary cathode material precursor. The modified graphene slurry comprises the following components in parts by weight: 0.1 to 0.6 parts of fluorinated silane coupling agent, 0.2 to 1 part of soluble boron-containing compound, 1 to 4 parts of surfactant, 3 to 10 parts of graphene, and 30 to 50 parts of anhydrous ethanol.

2. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, In step (1), the molar ratio of Ni:Co:Al is (70~85):(8~20):(4~10).

3. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, In step (1), the molar ratio of Ni:Co:Al is 78:15:

7.

4. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, At least one of the following (a) to (e): (a) The nickel source is one of nickel sulfate, nickel nitrate, nickel chloride, nickel acetate, and nickel oxalate; (b) The cobalt source is one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt oxalate; (c) The aluminum source is one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate, and aluminum oxalate; (d) The complexing agent is an aqueous ammonia solution; (e) The precipitant is a sodium hydroxide solution.

5. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, The reaction conditions in step (1) are: pH value of 10.5-13, reaction temperature of 45℃-60℃, and ammonia value of 10-18g / L; The conditions for the hydrothermal reaction in step (2) are: temperature of 120~180℃ and reaction time of 2~10h.

6. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, The modified graphene slurry comprises the following components in parts by weight: 0.1-0.4 parts of fluorinated silane coupling agent, 0.4-1 parts of soluble boron-containing compound, 1-3 parts of surfactant, 3-8 parts of graphene, and 35-50 parts of anhydrous ethanol.

7. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 6, characterized in that, The soluble boron-containing compound is boric acid; The surfactant is polyvinylpyrrolidone; The fluorinated silane coupling agent is one of 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane.

8. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 6, characterized in that, The preparation method of the modified graphene slurry is as follows: S1. Add graphene and surfactant to anhydrous ethanol and stir until homogeneous to obtain graphene mixture; S2. Heat the graphene mixture to 55~70℃, add a fluorinated silane coupling agent and a soluble boron-containing compound, and ultrasonically treat with 300~800W for 25~50min to obtain modified graphene slurry.

9. The method for preparing the nickel-cobalt-aluminum ternary cathode material precursor according to claim 1, characterized in that, The ball milling speed for the first ball milling is 400~800 rpm, the ball milling time is 0.5~2 h, and the ball-to-material ratio is (3~8):1; The second ball milling process involves a milling speed of 400-800 rpm, a milling time of 4-10 hours, and a ball-to-material ratio of (8-15):

1.

10. A nickel-cobalt-aluminum ternary cathode material precursor, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

11. A nickel-cobalt-aluminum ternary cathode material, characterized in that, It is formed by mixing and sintering a lithium source with the nickel-cobalt-aluminum ternary cathode material precursor as described in claim 10.

12. The application of the nickel-cobalt-aluminum ternary cathode material according to claim 11 in the preparation of lithium batteries.

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