High-nickel ternary precursor as well as preparation method and application thereof

Abstract

The invention relates to a high-nickel ternary precursor and a preparation method and application thereof.The high-nickel ternary precursor is a secondary particle formed by whiskers, the secondary particle comprises an inner core, a middle layer and an outer layer which are sequentially arranged in the direction from the center to the outer surface, the average distance between the whiskers in the inner core is a, and the average distance between the middle layer and the outer layer is a. The average distance between the whiskers in the middle layer is b, the average distance between the whiskers in the outer layer is c, and a, b and c meet the following conditions: b is smaller than a, and b is smaller than c. The surface of the high-nickel ternary precursor is free of cracks, when the high-nickel ternary precursor is used as a raw material to prepare the high-nickel ternary layered material and the high-nickel ternary layered material is applied to the lithium ion battery, the high-nickel ternary layered material has excellent structural stability, and the lithium ion battery has excellent rate capability and cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery positive electrode materials, and in particular to a high-nickel ternary precursor and a preparation method and application thereof. Background Art

[0002] High nickel ternary layered materials have shown significant application potential in the field of automotive power batteries due to their high specific capacity, low cost and good safety. High nickel ternary layered materials are made from high nickel ternary precursors. By combining large-particle high nickel ternary precursors with small-particle pure high nickel single crystal materials, a synergistic conductive network can be formed, which can simultaneously improve the tap density and energy density. However, in the preparation of large-particle high nickel ternary precursors, such as the preparation of D 50 When the high nickel ternary precursor is larger than 10μm, the high nickel ternary precursor is prone to cracking under high rotation speed and high solid content conditions, and the mechanical stress in the subsequent lithium mixing process will aggravate the risk of cracking of the high nickel ternary precursor. This structural damage not only destroys the stability of the material, but also accelerates the consumption of the electrolyte and the collapse of the positive electrode structure, ultimately leading to capacity decay. In order to avoid the generation of cracks, the traditional approach is to reduce the stirring intensity or reduce the synthesis time. However, reducing the stirring intensity will lead to poor sphericity of the high nickel ternary precursor, incomplete reaction or adhesion; shortening the synthesis time will reduce the tap density of the high nickel ternary precursor and reduce production capacity, which is not conducive to industrial production. Summary of the Invention

[0003] Based on this, it is necessary to provide a high-nickel ternary precursor and its preparation method and application to address the above problems. The whiskers inside the high-nickel ternary precursor are arranged in an orderly manner and there are no cracks on the surface. When the high-nickel ternary precursor is used as a raw material to prepare a high-nickel ternary layered material and applied to lithium-ion batteries, the high-nickel ternary layered material has excellent structural stability, and the lithium-ion battery has excellent rate performance and cycle stability.

[0004] The present invention discloses a high-nickel ternary precursor, which is a secondary particle formed by whiskers. The secondary particle includes an inner core, an intermediate layer, and an outer layer arranged in sequence from the center to the outer surface. The average distance between the whiskers in the inner core is a, the average distance between the whiskers in the intermediate layer is b, and the average distance between the whiskers in the outer layer is c. A, b, and c satisfy the following conditions: b is less than a, and b is less than c.

[0005] In one embodiment, the ratio of the radius of the inner core to the thickness of the intermediate layer is 1:1.33-1:2.66;

[0006] And / or, the ratio of the radius of the inner core to the thickness of the outer layer is 1:2.33-1:4.33.

[0007] In one embodiment, the D of the high nickel precursor 50 15μm-20μm.

[0008] In one embodiment, the half-maximum width of the (001) crystal plane of the high-nickel ternary precursor is less than or equal to 0.5.

[0009] In one embodiment, the molecular formula of the high nickel ternary precursor is Ni x Co y Mn z M w (OH)2, wherein M represents a doping metal element, 0.8≤x<0.95, 0.01<y≤0.1, 0.01<z≤0.15, w≤0.01, wherein x+y+z+w=1.

[0010] In one embodiment, the high nickel ternary precursor satisfies at least one of the following conditions:

[0011] (1) The high nickel precursor is spherical, and the sphericity is greater than or equal to 98%;

[0012] (2) The tap density of the high nickel precursor is 1.85 g / cm 3 -2.05g / cm 3 ;

[0013] (3) The specific surface area of ​​the high nickel precursor is 8.0 m 2 / g-18.0m 2 / g.

[0014] In the high nickel ternary precursor provided by the present invention, the whiskers have a directional and orderly arrangement in the high nickel ternary precursor, thereby not only being able to well reduce the internal stress of the high nickel ternary precursor and avoid cracks in the high nickel ternary precursor due to the increase in particle size, but also being able to shorten the distance of lithium ion transmission and reduce the resistance of lithium ion transmission across grain boundaries; at the same time, the high nickel ternary precursor presents the characteristics of a loose and porous core, a dense middle layer, and a loose and porous outer layer. The looseness and porosity of the core and the outer layer can enable the high nickel ternary precursor to better contact active substances such as lithium ions, and the high density of the middle layer can not only well undertake the inner layer, but also reduce the risk of lithium ion transmission. The material transfer between the core and the outer layer can also increase the tap density of the high-nickel ternary precursor and enhance the particle strength, thereby further improving the lithium ion transmission efficiency and avoiding the generation of cracks on the surface of the nickel ternary precursor. When the high-nickel ternary precursor is used as a raw material to prepare a high-nickel ternary layered material and applied to lithium-ion batteries, the high-nickel ternary layered material has excellent structural stability and is not prone to expansion and contraction due to anisotropy during the cycle. This not only helps to reduce the internal stress of the lithium-ion battery during the charge and discharge process, but also significantly alleviates the particle breakage and pulverization problems caused by electronic short circuits and electrolyte penetration. Ultimately, the lithium-ion battery exhibits excellent rate performance and cycle stability.

[0015] The present invention also discloses a method for preparing the high-nickel ternary precursor as described above, comprising the following steps:

[0016] adding a metal salt solution, a complexing agent solution, and a precipitant solution into a first base solution to perform a first coprecipitation reaction to obtain crystal nuclei, wherein the first base solution includes a complexing agent and a precipitant;

[0017] mixing the crystal nuclei, complexing agent solution, precipitant solution and solvent to obtain a second base solution;

[0018] A metal salt solution, a complexing agent solution, and a precipitant solution are added to the second base liquid to perform a second coprecipitation reaction to obtain a pre-product, and the pre-product is post-treated to obtain a high-nickel ternary precursor. In the step of performing the second co-precipitation reaction, the pH of the second base liquid is X, the ammonia concentration is Y, and X and Y satisfy the following conditions: Y=k×Xb, k is 4.7-5.3, and b is 49-50.

[0019] In one embodiment, X=10-11, Y=1.5 g / L-6.5 g / L.

[0020] In one embodiment, the step of adding the metal salt solution, the complexing agent solution, and the precipitant solution to the first base solution for the first coprecipitation reaction satisfies at least one of the following conditions:

[0021] (1) The metal salt solution includes nickel salt, cobalt salt and manganese salt;

[0022] (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3;

[0023] (3) the complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate;

[0024] (4) The metal liquid flow rate is 10L / h-35L / h, the bottom liquid ammonia value is 2.0-5.0g / L, and the bottom liquid pH is 11.10-11.90;

[0025] (5) The concentration of the metal liquid is 60-150g / L, and the precipitant is prepared with a mass concentration of 20% to 35%, and the complexing agent is prepared with a mass concentration of 5% to 15%.

[0026] (6) The temperature of the first coprecipitation reaction is 50°C-60°C and the time is 30h-40h;

[0027] (7) D of the crystal nucleus 50 4μm-6μm.

[0028] In one embodiment, the second base liquid satisfies at least one of the following conditions:

[0029] (1) The amount of the bottom liquid crystal core added is 10kg-20kg, the bottom liquid ammonia value is 1.5g / L-5.0g / L, and the bottom liquid pH is 10.00-10.80;

[0030] (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3;

[0031] (3) The complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate.

[0032] In one embodiment, the step of adding the metal salt solution, the complexing agent solution, and the precipitant solution to the second base solution for a second coprecipitation reaction satisfies at least one of the following conditions:

[0033] (1) The metal salt solution includes nickel salt, cobalt salt and manganese salt;

[0034] (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3;

[0035] (3) the complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate;

[0036] (4) The metal liquid flow rate is 15L / h-40L / h, the bottom liquid ammonia value is 1.5g / L-5.0g / L, and the bottom liquid pH is 10.00-10.80;

[0037] (5) The temperature of the second coprecipitation reaction is 50°C-70°C, and the time is 40h-70h.

[0038] In the preparation method of the high-nickel ternary precursor of the present invention, first, by controlling the pH and ammonia value of the first base liquid, a crystal nucleus with orderly arrangement of whiskers and loose and porous structure is obtained, and then the pH and ammonia value in the second co-precipitation reaction are made to meet certain linear conditions, thereby controlling the nucleation rate and growth rate, so that the whiskers grow radially, which not only realizes the orderly arrangement of the whiskers, but also increases the size of the whiskers, thereby reducing the internal structural stress of the crystal, thereby inhibiting cracking, and realizing the simple preparation of the high-nickel ternary precursor provided by the present invention. In addition, the preparation method has a simple preparation process and eliminates the pulping step, which can greatly improve production capacity and reduce the alkali consumption and water consumption of the subsequent washing process, saving costs and achieving cost reduction and efficiency improvement.

[0039] The present invention also discloses a high-nickel ternary layered material prepared by using the high-nickel ternary precursor as described above.

[0040] A method for preparing the high-nickel ternary layered material as described above comprises the following steps:

[0041] Providing the high-nickel ternary precursor as described above; and mixing the high-nickel ternary precursor with a lithium source in proportion, and performing solid-phase sintering to obtain a high-nickel ternary layered material.

[0042] A positive electrode sheet prepared using the high-nickel ternary layered material as described above.

[0043] A lithium-ion battery comprising the positive electrode sheet as described above.

[0044] The high-nickel ternary layered material provided by the present invention uses the above-mentioned high-nickel ternary precursor as raw material. Since the whiskers inside the raw material high-nickel ternary precursor are orderly arranged and the surface is crack-free, the high-nickel ternary layered material has excellent structural stability and is not prone to expansion and contraction due to anisotropy during the cycle. When the high-nickel ternary layered material is applied to lithium-ion batteries, it is beneficial to reduce the internal stress during the charge and discharge process of the lithium-ion battery, and can also significantly alleviate the problems of particle breakage and pulverization caused by electronic short circuits and electrolyte penetration. Ultimately, the lithium-ion battery exhibits excellent rate performance and cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 A schematic structural diagram of the high-nickel ternary precursor provided by the present invention;

[0047] Figure 2 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Example 1;

[0048] Figure 3 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Example 2;

[0049] Figure 4 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Example 3;

[0050] Figure 5 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Example 4;

[0051] Figure 6 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Comparative Example 1;

[0052] Figure 7 This is a scanning electron microscope image of the high-nickel ternary precursor prepared in Comparative Example 1.

[0053] In the figure, 10, inner core; 20, middle layer; 30, outer layer; 40, whiskers. DETAILED DESCRIPTION

[0054] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0056] The first aspect of the present invention provides a high nickel ternary precursor disclosed in the present invention, such as Figure 1As shown, the high nickel ternary precursor is a secondary particle formed by whiskers. The secondary particles include a core, a middle layer and an outer layer arranged in sequence from the center to the outer surface. The average distance between the whiskers in the core is a, the average distance between the whiskers in the middle layer is b, and the average distance between the whiskers in the outer layer is c. a, b, and c meet the following conditions: b is less than a, and b is less than c.

[0057] In one embodiment, the molecular formula of the high nickel ternary precursor is Ni x Co y Mn z M w (OH)2, wherein M represents a doping metal element, 0.8≤x<0.95, 0.01<y≤0.1, 0.01<z≤0.1, w≤0.01, wherein x+y+z+w=1, including but not limited to, M is selected from Al, Zr or Ti, x=0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93 or 0.9 4, y=0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, z=0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, w=0.01, 0.009, 0.008, 0.007, 0.006, 0.005, 0.004, 0.003, 0.002 or 0.001.

[0058] In the high-nickel ternary precursor provided by the present invention, the whiskers have a directional and orderly arrangement in the high-nickel ternary precursor. Therefore, it can not only effectively reduce the internal stress of the high-nickel ternary precursor and avoid cracks in the high-nickel ternary precursor due to increased particle size, but also shorten the distance of lithium ion transmission and reduce the resistance of lithium ion transmission across grain boundaries.

[0059] At the same time, the high-nickel ternary precursor has the characteristics of loose and porous inner core, dense middle layer, and loose and porous outer layer. The loose and porous inner core and outer layer enable the high-nickel ternary precursor to better contact active substances such as lithium ions, and the high density of the middle layer can not only well undertake the material transfer of the inner core and outer layer, but also increase the tap density of the high-nickel ternary precursor and enhance the particle strength, thereby further improving the transmission efficiency of lithium ions and avoiding the formation of cracks on the surface of the nickel ternary precursor.

[0060] In one embodiment, the ratio of the radius of the inner core to the thickness of the intermediate layer is 1:1.33-1:2.66, including but not limited to 1:1.33, 1:1.43, 1:1.53, 1:1.63, 1:1.73, 1:1.83, 1:1.93, 1:2.03, 1:2.13, 1:2.23, 1:2.33, 1:2.43, 1:2.53, 1:2. 63 or 1:2.66; the ratio of the radius of the inner core to the thickness of the outer layer is 1:2.33-1:4.33, including but not limited to 1:2.33, 1:2.53, 1:2.73, 1:2.93, 1:3.13, 1:3.33, 1:3.53, 1:3.73, 1:3.93, 1:4.13 or 1:4.33, thereby effectively improving the strength of the particles and reducing cracking.

[0061] In one embodiment, the D of the high nickel precursor 50 is 15μm-20μm; it should be noted that D 50 It is the characteristic value determined by the cumulative particle size distribution function, that is, the particle size parameter corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%. This parameter characterizes the middle distribution position of the powder particle size, where the particle size is larger than D 50 The particles account for 50% and the particle size is smaller than D 50 As an important characterization index of powder materials, D 50 Often used to quantify the average particle size characteristics of a material.

[0062] In one embodiment, the radius of the inner core is 1.5 μm to 3.5 μm, including but not limited to 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm or 3.5 μm.

[0063] In one embodiment, the thickness of the intermediate layer is 4 μm-8 μm, including but not limited to 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm or 8 μm.

[0064] In one embodiment, the thickness of the outer layer is 7 μm-13 μm, including but not limited to 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm or 13 μm.

[0065] The cracking of the surface of the high nickel ternary precursor is closely related to the internal structure of the high nickel ternary precursor. If the whiskers of the high nickel ternary precursor grow disorderly, the stress of the internal structure of the high nickel ternary precursor will be greatly increased, the particle strength will be reduced, and cracks will be generated. Since the surface energy of the crystal plane (001) is lower, growth and stacking are carried out rapidly along the (001) crystal plane. Therefore, the present invention finds that the half-peak width of the (001) crystal plane can be used to evaluate whether the surface of the high nickel ternary precursor is cracked. The half-peak width of the (001) crystal plane is small, indicating that the peak width is narrow, the whisker arrangement is well ordered, and the surface of the high nickel ternary precursor has few cracks or even no cracks. On the contrary, it means that the whisker arrangement is poorly ordered, the high nickel ternary precursor particle strength is poor or there are stress or defects, and the surface cracks are more. In one embodiment, the (001) crystal plane half-peak width of the high nickel ternary precursor is less than or equal to 0.5, including but not limited to 0.5, 0.4, 0.3, 0.2, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02 or 0.01.

[0066] In one embodiment, the high nickel precursor is spherical, so that when mixed with a lithium source and solid-phase sintered, lithium can more evenly penetrate into the high nickel precursor. Preferably, the sphericity of the high nickel precursor is greater than or equal to 98%.

[0067] In one embodiment, the tap density of the high nickel precursor is 1.85 g / cm 3 -2.05g / cm 3 , including but not limited to 1.85g / cm 3 、1.90g / cm 3 , 1.95g / cm 3 , 2.00g / cm 3 or 2.05g / cm 3 .

[0068] In one embodiment, the specific surface area of ​​the high nickel precursor is 8.0 m 2 / g-18.0m 2 / g, including but not limited to 8.0m 2 / g, 9.0m 2 / g, 10.0m 2 / g, 11.0m 2 / g, 12.0m 2 / g, 13.0m 2 / g, 14.0m 2 / g, 15.0m 2 / g, 16.0m 2 / g, 17.0m 2 / g or 18.0m 2 / g,.

[0069] When high-nickel ternary layered materials are prepared using this high-nickel ternary precursor as raw material and applied to lithium-ion batteries, the high-nickel ternary layered materials exhibit excellent structural stability and are less susceptible to expansion and contraction due to anisotropy during cycling. This not only helps reduce internal stress during the charge and discharge process of lithium-ion batteries, but also significantly alleviates the problems of particle breakage and pulverization caused by electronic short circuits and electrolyte penetration. Ultimately, the lithium-ion battery exhibits excellent rate performance and cycling stability.

[0070] A second aspect of the present invention provides a method for preparing the high-nickel ternary precursor as described above, comprising the following steps:

[0071] S101, adding a metal salt solution, a complexing agent solution, and a precipitant solution to a first base solution to perform a first coprecipitation reaction to obtain crystal nuclei, wherein the first base solution includes a complexing agent and a precipitant;

[0072] S102, mixing the crystal nuclei, the complexing agent solution, the precipitant solution, and the solvent to obtain a second base solution;

[0073] S103, adding the metal salt solution, the complexing agent solution, and the precipitant solution to the second base liquid for a second co-precipitation reaction to obtain a pre-product, and post-treating the pre-product to obtain a high-nickel ternary precursor. In the step of performing the second co-precipitation reaction, the pH of the second base liquid is X, the ammonia concentration is Y, and X and Y satisfy the following conditions: Y = k × Xb, k is 4.7-5.3, and b is 49-50.

[0074] In the preparation method of the high-nickel ternary precursor of the present invention, each step cooperates with each other to achieve the simple preparation of the above-mentioned high-nickel ternary precursor. In addition, the preparation method has a simple preparation process and eliminates the pulping step, which can greatly improve production capacity and reduce the alkali consumption and water consumption of the subsequent washing process, saving costs and achieving cost reduction and efficiency improvement.

[0075] In step S101, the pH and ammonia value of the first base liquid are controlled to obtain a crystal nucleus with orderly arrangement of whiskers and loose and porous structure. In one embodiment, the crystal nucleus is equivalent to the inner core. 50 4 μm-6 μm, including but not limited to 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm.

[0076] In one embodiment, the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3; preferably, the precipitant solution is selected from a sodium hydroxide aqueous solution with a mass fraction of 20%-35%, and the pH of the first base solution is 11.10-11.90, including but not limited to 11.10, 11.20, 11.30, 11.40, 11.50, 11.60, 11.70, 11.80 or 11.90.

[0077] In one embodiment, the complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate. Preferably, the complexing agent solution is selected from an ammonia solution with a mass fraction of 5%-15%, and the bottom liquid ammonia value is 1.5g / L-5.0g / L, including but not limited to 1.5g / L, 2.0g / L, 2.5g / L, 3.0g / L, 3.5g / L, 4.0g / L, 4.5g / L or 5.0g / L.

[0078] In one embodiment, the first base liquid is obtained by mixing water, a complexing agent solution, and a precipitant solution. In order to prevent the reactants from being oxidized by air during the synthesis process, nitrogen is introduced into the first base liquid after mixing for replacement, and the temperature of the first base liquid is controlled at 50°C-60°C, including but not limited to 50°C, 52°C, 54°C, 56°C, 58°C or 60°C.

[0079] In one embodiment, the metal salt solution includes nickel salts, cobalt salts and manganese salts, including but not limited to, nickel salts selected from nickel carbonate salts, nickel nitrate salts, nickel sulfate salts, and halogen nickel salts, cobalt salts selected from cobalt carbonate salts, cobalt nitrate salts, cobalt sulfate salts, and halogen cobalt salts, and manganese salts selected from manganese carbonate salts, manganese nitrate salts, manganese sulfate salts, and halogen manganese salts.

[0080] In one embodiment, the temperature of the first coprecipitation reaction is 50°C-60°C, including but not limited to 50°C, 52°C, 54°C, 56°C, 58°C or 60°C, and the time is 30h-40h, including but not limited to 30h, 32h, 34h, 36h, 38h or 40h.

[0081] In step S102, the pH and ammonia value of the second base liquid meet certain linear conditions, thereby controlling the nucleation rate and growth rate of the second coprecipitation reaction in step S103, so that the whiskers grow radially, which not only achieves the orderly arrangement of the whiskers, but also increases the size of the whiskers, thereby reducing the internal structural stress of the crystal and inhibiting cracking, thereby inhibiting cracking.

[0082] The types of the complexing agent solution and the precipitant solution in step S102 are selected with reference to step S101 and can be the same or different, as long as the pH and ammonia concentration of the second base solution meet the following conditions: Y = k × Xb, k is 4.7-5.3, including but not limited to 4.7, 4.8, 4.9, 5.0, 5.1, 5.2 or 5.3, and b is 49-50, including but not limited to 49, 49.5 or 50; preferably, k = 5, b = 49.5, that is, the pH and ammonia concentration of the second base solution meet the following conditions: Y = 5X-49.5.

[0083] In one embodiment, X=10-11, Y=1.5 g / L-6.5 g / L.

[0084] In one embodiment, the solvent is selected from water.

[0085] In one embodiment, the second base liquid is obtained by mixing a solvent, crystal nuclei, a complexing agent solution, and a precipitant solution. In order to prevent the reactants from being oxidized by air during the synthesis process, nitrogen is introduced into the second base liquid after mixing for replacement, and the temperature of the second base liquid is controlled at 50°C-70°C, including but not limited to 50°C, 55°C, 60°C, 65°C or 70°C.

[0086] In one embodiment, the amount of bottom liquid crystal core added is 10kg-20kg, the bottom liquid ammonia value is 1.5g / L-5.0g / L, including but not limited to 1.5g / L, 2.0g / L, 2.5g / L, 3.0g / L, 3.5g / L, 4.0g / L, 4.5g / L or 5.0g / L, and the bottom liquid pH is 10.00-10.80, including but not limited to 10.00, 10.10, 10.20, 10.30, 10.40, 10.50, 10.60, 10.70 or 10.80.

[0087] The types of the metal salt, complexing agent solution, and precipitant solution in step S103 are selected with reference to step S101 and may be the same or different.

[0088] In one embodiment, the temperature of the second coprecipitation reaction is 50°C-70°C, including but not limited to 50°C, 55°C, 60°C, 65°C or 70°C, and the time is 40h-70h, including but not limited to 40h, 45h, 50h, 55h, 60h, 65h or 70h.

[0089] In one embodiment, the step of post-processing the pre-product comprises: aging, washing, drying, screening and de-ironing the pre-product in sequence.

[0090] Since the high-nickel ternary precursor prepared by the preparation method provided by the present invention has no cracks on its surface, it is not necessary to add alkali solution or other repair agents to repair cracks during the aging process, and the aging time is 1h-3h.

[0091] In one embodiment, the pre-product is washed with alkaline water and water in sequence, the concentration of the alkaline water is 80 g / L-150 g / L, and the washing time with the alkaline water is 20 min-50 min.

[0092] In one embodiment, the sieving is performed using a sieve with a mesh size of 200-400.

[0093] In one embodiment, the drying temperature is 80° C.-120° C., and the drying time is 8 h-12 h.

[0094] The third aspect of the present invention provides a high-nickel ternary layered material prepared using the high-nickel ternary precursor as described above.

[0095] A fourth aspect of the present invention provides a method for preparing the high-nickel ternary layered material as described above, comprising the following steps:

[0096] S201, providing the high nickel ternary precursor as described above;

[0097] S202, mixing the high-nickel ternary precursor and the lithium source in proportion, and performing solid-phase sintering to obtain a high-nickel ternary layered material.

[0098] In one embodiment, the sintering temperature is 700°C-900°C.

[0099] In one embodiment, in the step of performing solid phase sintering, the sintering time is 8 hours to 10 hours.

[0100] A fifth aspect of the present invention provides a positive electrode sheet prepared using the high-nickel ternary layered material as described above.

[0101] In a sixth aspect of the present invention, a lithium-ion battery comprising the positive electrode sheet as described above is provided.

[0102] The high-nickel ternary layered material provided by the present invention uses the above-mentioned high-nickel ternary precursor as raw material. Since the whiskers inside the raw material high-nickel ternary precursor are orderly arranged and the surface is crack-free, the high-nickel ternary layered material has excellent structural stability and is not prone to expansion and contraction due to anisotropy during the cycle. When the high-nickel ternary layered material is applied to lithium-ion batteries, it is beneficial to reduce the internal stress during the charge and discharge process of the lithium-ion battery, and can also significantly alleviate the problems of particle breakage and pulverization caused by electronic short circuits and electrolyte penetration. Ultimately, the lithium-ion battery exhibits excellent rate performance and cycle stability.

[0103] Hereinafter, the high nickel ternary precursor and its preparation method and application will be further described through the following specific examples.

[0104] Example 1

[0105] Using pure water, nickel sulfate, cobalt sulfate, and manganese sulfate are prepared into a metal salt solution with a concentration of 135 g / L, wherein the molar ratio of nickel, cobalt, and manganese is 83.0:5.0:12.0; a sodium hydroxide solution with a concentration of 320 g / L is used as a precipitant solution; an ammonia solution with a mass concentration of 8% is used as a complexing agent solution; water, the complexing agent solution, and the precipitant solution are added to a reactor to prepare a first bottom solution, nitrogen is introduced for displacement, stirring is started, and the temperature is kept constant at 50° C. The stirring speed of the reactor is set to 400 rpm; the pH of the first bottom solution in the reactor is adjusted to 11.80 and the ammonia concentration is 1.7 g / L; a first coprecipitation reaction is carried out to prepare crystal nuclei, and the crystal nucleus particle size D is 0.04. 50 The reaction was stopped when the particle size was 5.3 μm.

[0106] Crystal nuclei, water, and a complexing agent solution were added to a reactor to prepare a second bottom liquid, nitrogen was introduced for displacement, stirring was started, and the temperature was maintained at 55° C. after heating. The stirring speed of the reactor was set to 360 rpm. The pH of the second bottom liquid was X, and the ammonia concentration was Y. The pH value and ammonia concentration of the second bottom liquid were adjusted so that X and Y satisfied the following conditions: Y = 5X - 49.5, where X was 10.30 and Y was 2.0 g / L.

[0107] The metal salt solution, complexing agent solution, precipitant solution and nitrogen are introduced into the second bottom liquid to carry out the second coprecipitation reaction. 50 The reaction was stopped when the particle size was 19.50 μm to obtain a pre-product, which was then aged, washed, dried, sieved, and iron removed to obtain a high-nickel ternary precursor. The obtained high-nickel ternary precursor was characterized by SEM. The results are as follows: Figure 2 As shown, from Figure 2 It can be seen that the primary particle whiskers of the high-nickel ternary precursor are arranged in an orderly manner, and there are no fine impurity crystals; the secondary particles have good sphericity, the inner core is loose and porous, the middle layer is dense, the outer layer is loose and porous, and there are no cracks on the outer surface, and the particle size distribution is uniform.

[0108] Example 2

[0109] Example 2 was carried out in accordance with Example 1, except that the temperature of the second base solution was 63°C. The obtained high nickel ternary precursor was characterized by SEM. The results are shown in FIG. Figure 3 As shown, from Figure 3 It can be seen that the primary particle whiskers of the high-nickel ternary precursor are arranged in an orderly manner, and there are no fine impurity crystals; the secondary particles have good sphericity, the inner core is loose and porous, the middle layer is dense, the outer layer is loose and porous, and there are no cracks on the outer surface, and the particle size distribution is uniform.

[0110] Example 3

[0111] Example 3 was carried out in accordance with Example 1, except that the pH of the second base solution was X, the ammonia concentration was Y, X and Y satisfied: Y = 5X-49.5, X was 10.50, and Y was 3.0 g / L. The obtained high nickel ternary precursor was characterized by SEM, and the results were as follows: Figure 4 As shown, from Figure 4 It can be seen that the primary particle whiskers of the high-nickel ternary precursor are arranged in an orderly manner, and there are no fine impurity crystals; the secondary particles have good sphericity, the inner core is loose and porous, the middle layer is dense, the outer layer is loose and porous, and there are no cracks on the outer surface, and the particle size distribution is uniform.

[0112] Example 4

[0113] Example 4 was carried out in accordance with Example 1, except that the pH of the second bottom solution was X, the ammonia concentration was Y, X and Y satisfied: Y = 5X-49.5, X was 10.60, Y was 3.5 g / L, and during the second coprecipitation reaction, D 50 The reaction was stopped when the particle size was 17.00 μm. The SEM characterization of the prepared high nickel ternary precursor was carried out, and the results were as follows: Figure 5 As shown, from Figure 5 It can be seen that the primary particle whiskers of the high-nickel ternary precursor are arranged in an orderly manner, and there are no fine impurity crystals; the secondary particles have good sphericity, the inner core is loose and porous, the middle layer is dense, the outer layer is loose and porous, and there are no cracks on the outer surface, and the particle size distribution is uniform.

[0114] Comparative Example 1

[0115] Comparative Example 1 was carried out in accordance with Example 1, except that the temperature of the first base solution was 55°C, the pH of the second base solution was 10.80, and the ammonia concentration was 5.5 g / L. The obtained high nickel ternary precursor was characterized by SEM. The results are shown in FIG. Figure 6 As shown by Figure 6 It can be seen that since the pH and ammonia value of the second base liquid in Comparative Example 1 do not meet the following conditions: Y=k×Xb, k is 4.7-5.3, and b is 49-50, the primary particle whiskers of the high-nickel ternary precursor are disorderly, the whiskers have poor consistency and are of different sizes, and there are obvious cracks on the outer surface of the secondary particles.

[0116] Comparative Example 2

[0117] Comparative Example 2 was carried out in accordance with Example 1, except that the temperature of the first base solution was 55°C, the pH of the second base solution was 10.50, and the ammonia concentration was 4.2 / L. The obtained high nickel ternary precursor was characterized by SEM, and the results were as follows: Figure 7 As shown by Figure 7It can be seen that since the pH and ammonia value of the second drop of liquid in Comparative Example 2 do not meet the following conditions: Y=k×Xb, k is 4.7-5.3, and b is 49-50, the primary particle whiskers of the high-nickel ternary precursor are disorderly, the whiskers have poor consistency and are of different sizes, and there are obvious cracks on the outer surface of the secondary particles.

[0118] Test Example 1

[0119] The (001) crystal plane half-width and (101) crystal plane half-width, specific surface area and tap density of the high-nickel ternary precursors prepared in Examples 1-4 and Comparative Examples 1-2 were tested. The specific testing methods are shown below, and the test results are shown in Table 1. The high-nickel ternary precursors prepared in Examples 1-4 and Comparative Examples 1-2 were further made into high-nickel ternary layered materials, and the cyclic stability and electrochemical properties of the high-nickel ternary layered materials were tested. The preparation methods and testing methods are shown below, and the test results are shown in Table 2.

[0120] (001) and (101) crystal plane half-peak width: X-ray diffractometer

[0121] Specific surface area (SSA): measured by low-temperature nitrogen adsorption method.

[0122] Tap density: BT-303 tap density meter

[0123] Preparation method of high nickel ternary layered material:

[0124] Cycle stability: capacity retention after 30 cycles.

[0125] Discharge capacity: first discharge capacity

[0126] First coulombic efficiency: first discharge capacity / first charge capacity.

[0127] Table 1

[0128]

[0129]

[0130] Table 2

[0131]

[0132] From the data in Table 1, it can be seen that at the same main content and D 50 When the half-peak width of the (001) crystal plane is greater than 17.0 μm, the cracking of the high-nickel ternary precursor is related to the half-peak width of the (001) crystal plane. When the half-peak width of the (001) crystal plane is less than 0.5, the high-nickel ternary precursor has no cracking; when the half-peak width of the (001) crystal plane is greater than 0.55, the high-nickel ternary precursor has obvious cracking; combined with Table 1, Figure 1、 Figure 5 、 Figure 6 It can be seen that the larger the value of the half-peak width of the (001) crystal plane is, the more the number of secondary particle cracking balls increases, and the corresponding cracks are obviously deepened; combined with Table 1, Figure 4 、 Figure 5 and Figure 6 It can be seen that the half-peak width of the (101) crystal plane of Example 4 is significantly larger than that of Example 1, Example 2, and Example 3, and is close to that of Comparative Example 2, indicating that the half-peak width of the (101) crystal plane cannot be used to evaluate the cracking of the high-nickel ternary precursor.

[0133] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A high nickel ternary precursor, characterized in that: The high-nickel ternary precursor is a secondary particle formed by whiskers, and the secondary particle includes an inner core, an intermediate layer, and an outer layer arranged in sequence from the center to the outer surface. The average distance between the whiskers in the inner core is a, the average distance between the whiskers in the intermediate layer is b, and the average distance between the whiskers in the outer layer is c. a, b, and c satisfy the following conditions: b is less than a, and b is less than c.

2. The high nickel ternary precursor according to claim 1, characterized in that The ratio of the radius of the inner core to the thickness of the intermediate layer is 1:1.33-1:2.66; And / or, the ratio of the radius of the inner core to the thickness of the outer layer is 1:2.33-1:4.

33.

3. The high nickel ternary precursor according to claim 2, characterized in that The high nickel precursor D 50 15μm-20μm.

4. The high nickel ternary precursor according to claim 1, characterized in that The half-peak width of the (001) crystal plane of the high-nickel ternary precursor is less than or equal to 0.

5.

5. The high-nickel ternary precursor according to any one of claims 1 to 4, characterized in that The molecular formula of the high nickel ternary precursor is Ni x Co y Mn z M w (OH)2, wherein M represents a doping metal element, 0.8≤x<0.95, 0.01<y≤0.1, 0.01<z≤0.15, w≤0.01, wherein x+y+z+w=1.

6. The high-nickel ternary precursor according to any one of claims 1 to 4, characterized in that The high nickel ternary precursor satisfies at least one of the following conditions: (1) The high nickel precursor is spherical, and the sphericity is greater than or equal to 98%; (2) The tap density of the high nickel precursor is 1.85 g / cm 3 -2.05g / cm 3 ; (3) The specific surface area of ​​the high nickel precursor is 8.0 m 2 / g-18.0m 2 / g.

7. A method for preparing a high-nickel ternary precursor according to any one of claims 1 to 6, characterized in that: The following steps are involved: adding a metal salt solution, a complexing agent solution, and a precipitant solution into a first base solution to perform a first coprecipitation reaction to obtain crystal nuclei, wherein the first base solution includes a complexing agent and a precipitant; mixing the crystal nuclei, complexing agent solution, precipitant solution and solvent to obtain a second base solution; A metal salt solution, a complexing agent solution, and a precipitant solution are added to the second base liquid to perform a second coprecipitation reaction to obtain a pre-product, and the pre-product is post-treated to obtain a high-nickel ternary precursor. In the step of performing the second co-precipitation reaction, the pH of the second base liquid is X, the ammonia concentration is Y, and X and Y satisfy the following conditions: Y=k×Xb, k is 4.7-5.3, and b is 49-50.

8. The method for preparing a high-nickel ternary precursor according to claim 7, characterized in that: X=10-11, Y=1.5g / L-6.5g / L.

9. The method for preparing a high-nickel ternary precursor according to claim 7 or 8, characterized in that: The step of adding the metal salt solution, the complexing agent solution, and the precipitant solution to the first base solution to perform the first coprecipitation reaction satisfies at least one of the following conditions: (1) The metal salt solution includes nickel salt, cobalt salt and manganese salt; (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3; (3) the complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate; (4) The metal liquid flow rate is 10L / h-35L / h, the bottom liquid ammonia value is 2.0-5.0g / L, and the bottom liquid pH is 11.10-11.90; (5) The concentration of the metal liquid is 60-150g / L, and the precipitant is prepared with a mass concentration of 20% to 35%, and the complexing agent is prepared with a mass concentration of 5% to 15%. (6) The temperature of the first coprecipitation reaction is 50°C-60°C and the time is 30h-40h; (7) D of the crystal nucleus 50 4μm-6μm.

10. The method for preparing a high-nickel ternary precursor according to claim 7 or 8, characterized in that: The second base liquid satisfies at least one of the following conditions: (1) The amount of the bottom liquid crystal core added is 10kg-20kg, the bottom liquid ammonia value is 1.5g / L-5.0g / L, and the bottom liquid pH is 10.00-10.80; (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3; (3) The complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate.

11. The method for preparing a high-nickel ternary precursor according to claim 7 or 8, characterized in that: The step of adding the metal salt solution, the complexing agent solution, and the precipitant solution to the second base solution for a second coprecipitation reaction satisfies at least one of the following conditions: (1) The metal salt solution includes nickel salt, cobalt salt and manganese salt; (2) the precipitant solution includes at least one of NaOH, KOH, Na2CO3 or NaHCO3; (3) the complexing agent solution includes at least one of ammonia water, ammonium carbonate or ammonium bicarbonate; (4) The metal liquid flow rate is 15L / h-40L / h, the bottom liquid ammonia value is 1.5g / L-5.0g / L, and the bottom liquid pH is 10.00-10.80; (5) The temperature of the second coprecipitation reaction is 50°C-70°C, and the time is 40h-70h.

12. A high-nickel ternary layered material prepared using the high-nickel ternary precursor according to any one of claims 1 to 6.

13. A method for preparing the high-nickel ternary layered material according to claim 12, characterized in that: The following steps are involved: Providing a high-nickel ternary precursor as described in any one of claims 1 to 6; and mixing the high-nickel ternary precursor with a lithium source in proportion, and performing solid-phase sintering to obtain a high-nickel ternary layered material.

14. A positive electrode sheet prepared using the high-nickel ternary layered material according to claim 12.

15. A lithium ion battery comprising the positive electrode sheet according to claim 14.

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