A high specific surface area high tap density small particle ternary precursor, a preparation method thereof, a positive electrode material and a lithium ion battery

Abstract

This application provides a high specific surface area, high tap density small-particle ternary precursor, its preparation method, cathode material, and lithium-ion battery, relating to the field of lithium-ion batteries. It includes a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core; the core is a secondary particle formed by the stacking of multiple primary particles; the first and second coating layers are each independently formed by alternating layers of sheet-like primary particles; the sheet-like primary particles of the first coating layer are shorter than those of the second coating layer. The high specific surface area, high tap density small-particle ternary precursor exhibits a porous morphology with a loose interior and a relatively dense exterior, increasing porosity and specific surface area. Simultaneously, the relatively dense surface structure improves the tap density of the precursor. This morphology, when sintered into a cathode material, is beneficial for lithium-ion electron transport.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a high specific surface area, high tap density small particle ternary precursor and its preparation method, cathode material and lithium-ion battery. Background Technology

[0002] Currently, ternary precursors are mainly prepared using the discontinuous method, which offers better uniformity of primary and secondary particles compared to continuous methods. However, in the discontinuous process, specific surface area and tap density exhibit opposite trends; increasing the tap density inevitably reduces the specific surface area. Existing research indicates that the energy density and charge-discharge performance of ternary lithium-ion batteries are insufficient because it is difficult to simultaneously increase the tap density and specific surface area of ​​ternary precursor materials. Therefore, improving the specific surface area while maintaining a high tap density presents a significant challenge.

[0003] Therefore, there is an urgent need to provide a method for preparing ternary precursors to solve the above problems. Summary of the Invention

[0004] The purpose of this application is to provide a high specific surface area, high tap density small particle ternary precursor and its preparation method, cathode material and lithium-ion battery, so as to solve the above problems.

[0005] To achieve the above objectives, the first aspect of this application provides a high specific surface area, high tap density, small particle ternary precursor, comprising a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core;

[0006] The core is a secondary particle formed by the stacking of multiple primary particles;

[0007] The first coating layer and the second coating layer are each independently composed of alternating sheet-like primary particles;

[0008] The sheet-like primary particles of the first coating layer are shorter than the sheet-like primary particles of the second coating layer;

[0009] The general structural formula of the high specific surface area, high tap density, small-particle ternary precursor is Ni. x Co y Mn z (OH)2, where x+y+z=1, 0.50≤x≤0.80, 0.05≤y≤0.20, 0.10≤z≤0.30.

[0010] Optionally, the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0011] (1) The particle size of the high specific surface area and high tap density small particle ternary precursor is 2.75-3.75 μm;

[0012] (2) The tap density of the high specific surface area, high tap density small particle ternary precursor is 1.55-1.75 g / cm³. 3 ;

[0013] (3) The particle size of the kernel is 1.5-2.0 μm;

[0014] (4) The thickness of the first coating layer is 0-0.7 μm, and the thickness is not 0;

[0015] (5) The length of the primary particles in the first coating layer is 0.1-0.4 μm;

[0016] (6) The thickness of the second coating layer is 0.1-0.5 μm;

[0017] (7) The length of the primary particles in the second coating layer is 0.3-0.6 μm;

[0018] (8) The specific surface area of ​​the high specific surface area, high tap density, small particle ternary precursor is 12-20 m². 2 / g.

[0019] A second aspect of this application provides a method for preparing the high specific surface area, high tap density small particle ternary precursor described above, comprising:

[0020] Under an inert atmosphere, a nickel-cobalt-manganese mixed metal salt solution, precipitant, and complexing agent are introduced into a base solution containing a precipitant and a complexing agent to carry out a first coprecipitation reaction to obtain seed crystals;

[0021] Continue to pass in a mixed metal salt solution of nickel, cobalt and manganese, a precipitant and a complexing agent to carry out a nucleation reaction to obtain a secondary particulate slurry, and control the pH value of the nucleation reaction to be lower than that of the first coprecipitation reaction;

[0022] Under an oxygen-containing atmosphere, a nickel-cobalt-manganese mixed metal salt solution, a precipitant, and a complexing agent are introduced into the secondary particle slurry, and a second coprecipitation reaction and a third coprecipitation reaction are carried out sequentially to obtain a ternary precursor with high specific surface area and high tap density small particles; wherein, the pH value of the second coprecipitation reaction is higher than that of the third coprecipitation reaction, and the color L value of the second coprecipitation reaction is lower than that of the third coprecipitation reaction.

[0023] Optionally, the preparation method of the high specific surface area and high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0024] (1) The precipitant includes sodium hydroxide and / or potassium hydroxide;

[0025] (2) The complexing agent includes ammonia;

[0026] (3) The concentration of the precipitant is 6-12 mol / L;

[0027] (4) The concentration of the nickel-cobalt-manganese mixed metal salt solution is 1.5-2.5 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 0.50-0.80:0.05-0.20:0.10-0.30.

[0028] Optionally, the preparation method of the high specific surface area and high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0029] (1) The alkalinity of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 7-12 g / L independently;

[0030] (2) The temperatures of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 50-70℃.

[0031] Optionally, the preparation method of the high specific surface area and high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0032] (1) The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction is 2.2-2.6:1;

[0033] (2) The pH of the first coprecipitation reaction is 11.70-12.00;

[0034] (3) The time for the first coprecipitation reaction is 40 min to 120 min.

[0035] Optionally, the preparation method of the high specific surface area and high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0036] (1) The pH at the endpoint of the nucleation inhibition reaction is 11.5-11.7;

[0037] (2) The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction is 0.8-1.5:1;

[0038] (3) The particle size of the particles in the secondary granular slurry is 1.5-2.0 μm.

[0039] Optionally, the preparation method of the high specific surface area and high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0040] (1) The pH value of the second coprecipitation reaction is 11.5-11.7;

[0041] (2) The color L value of the second coprecipitation reaction is 34-40;

[0042] (3) The pH value of the third coprecipitation reaction is 11.0-11.4;

[0043] (4) The color L value of the third coprecipitation reaction is 39-45;

[0044] (5) The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the second coprecipitation reaction is gradually increased from 60-200 mL / min to 180-450 mL / min;

[0045] (6) The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the third coprecipitation is 300-600 mL / min;

[0046] (7) The particle size of the material at the end of the second coprecipitation reaction is 2.0-2.9 μm.

[0047] A third aspect of this application provides a cathode material prepared from the aforementioned high specific surface area, high tap density, small-particle ternary precursor.

[0048] A fourth aspect of this application provides a lithium-ion battery, including the aforementioned positive electrode material.

[0049] Compared with the prior art, the beneficial effects of this application include:

[0050] The high specific surface area and high tap density small particle ternary precursor provided in this application exhibits a porous morphology with a loose interior and a relatively dense exterior. This increases the porosity of the surface of the high specific surface area and high tap density small particle ternary precursor, thereby increasing its specific surface area. At the same time, the relatively dense surface of the high specific surface area and high tap density small particle ternary precursor simultaneously increases its tap density. This morphology, when sintered into a cathode material, is beneficial for the transport of lithium electrons.

[0051] The method for preparing a high specific surface area and high tap density small-particle ternary precursor provided in this application involves, firstly, forming seed crystals through nucleation. After nucleation, a nucleation inhibition reaction is initiated by rapidly decreasing the pH, resulting in the aggregation of primary and secondary particles, increasing the core size, and improving the specific surface area of ​​the product. Then, a high pH is used to change the growth direction of the primary particle crystal faces, forming shorter plates. Simultaneously, a staged oxidation method is used to increase the oxidation degree (reducing the color L value), thereby refining the primary particles and forming densely packed, short-plate primary particles arranged in an alternating pattern as secondary spherical particles. Finally, the pH is decreased, and the oxidation degree is simultaneously reduced (increasing the color L value), resulting in a high specific surface area and high tap density small-particle ternary precursor with an outermost layer composed of coarse and wide long-plate primary particles (relative to the inner primary particles) arranged in an alternating pattern. This method is simple to operate and the raw materials are readily available.

[0052] The cathode material and lithium-ion battery provided in this application have high energy density, excellent rate performance and long cycle life. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0054] Figure 1 A 30kx cross-sectional SEM image of the high specific surface area, high tap density, small particle ternary precursor provided in Example 1;

[0055] Figure 2 A 5kx cross-sectional SEM image of the high specific surface area, high tap density, small particle ternary precursor provided in Example 1;

[0056] Figure 3 A 1000x SEM image of the surface of the high specific surface area, high tap density, small particle ternary precursor provided in Example 1;

[0057] Figure 4 A 5000x SEM image of the surface of the high specific surface area, high tap density, small particle ternary precursor provided in Example 1;

[0058] Figure 5 The surface SEM image of the high specific surface area, high tap density, small particle ternary precursor provided in Example 1 is magnified 20,000 times. Detailed Implementation

[0059] First, the solution provided in this application will be explained in more detail as follows:

[0060] The first aspect of this application provides a high specific surface area, high tap density, small particle ternary precursor, including a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core;

[0061] The core is a secondary particle formed by the stacking of multiple primary particles;

[0062] The first coating layer and the second coating layer are each independently composed of alternating sheet-like primary particles;

[0063] The sheet-like primary particles of the first coating layer are shorter than the sheet-like primary particles of the second coating layer;

[0064] The general structural formula of the high specific surface area, high tap density, small-particle ternary precursor is Ni. x Co y Mn z (OH)2, where x+y+z=1, 0.50≤x≤0.80, 0.05≤y≤0.20, 0.10≤z≤0.30.

[0065] Optionally, in the general structural formula of a ternary precursor with high specific surface area and high tap density small particles, x can be any value between 0.5, 0.6, 0.7, 0.8 or 0.5-0.8, y can be any value between 0.05, 0.1, 0.15, 0.2 or 0.05-0.2, and z can be any value between 0.1, 0.2, 0.3 or 0.1-0.3.

[0066] In some embodiments, the high specific surface area, high tap density, small particle ternary precursor satisfies at least one of the following conditions:

[0067] (1) The particle size of the high specific surface area and high tap density small particle ternary precursor is 2.75-3.75 μm;

[0068] Optionally, the particle size of the high specific surface area and high tap density small particle ternary precursor can be any value between 2.75 μm, 3 μm, 3.25 μm, 3.5 μm, 3.75 μm, or 2.75-3.75 μm;

[0069] (2) The tap density of the high specific surface area, high tap density small particle ternary precursor is 1.55-1.75 g / cm³. 3 ;

[0070] Optionally, the tap density of the high specific surface area, high tap density small-particle ternary precursor can be 1.55 g / cm³. 3 1.6 g / cm 3 1.65 g / cm 3 1.7 g / cm 31.75 g / cm 3 Or 1.55-1.75 g / cm³ 3 Any value between;

[0071] (3) The particle size of the kernel is 1.5-2.0 μm;

[0072] Optionally, the kernel particle size can be any value between 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm or 1.5-2μm;

[0073] (4) The thickness of the first coating layer is 0-0.7 μm, and the thickness is not 0;

[0074] Optionally, the thickness of the first coating layer can be 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, or any value greater than 0μm and less than or equal to 0.7μm;

[0075] (5) The length of the primary particles in the first coating layer is 0.1-0.4 μm;

[0076] Optionally, the length of the primary particles in the first coating layer can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, or any value between 0.1 and 0.4 μm;

[0077] (6) The thickness of the second coating layer is 0.1-0.5 μm;

[0078] Optionally, the thickness of the second coating layer can be any value between 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or 0.1-0.5 μm;

[0079] (7) The length of the primary particles in the second coating layer is 0.3-0.6 μm.

[0080] Optionally, the length of the primary particles in the second coating layer can be any value between 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, or 0.3-0.6 μm;

[0081] (8) The specific surface area of ​​the high specific surface area, high tap density, small particle ternary precursor is 12-20 m². 2 / g.

[0082] Optionally, the specific surface area of ​​the high specific surface area, high tap density small particle ternary precursor can be 12 m². 2 / g、14m 2 / g、16 m 2 / g、18 m 2 / g、20 m 2 / g or 12-20 mg 2 Any value between / g.

[0083] A second aspect of this application provides a method for preparing the high specific surface area, high tap density small particle ternary precursor described above, comprising:

[0084] Under an inert atmosphere, a nickel-cobalt-manganese mixed metal salt solution, precipitant, and complexing agent are introduced into a base solution containing a precipitant and a complexing agent to carry out a first coprecipitation reaction to obtain seed crystals;

[0085] Continue to pass in a mixed metal salt solution of nickel, cobalt and manganese, a precipitant and a complexing agent to carry out a nucleation inhibition reaction to obtain a secondary particulate slurry, and control the pH value of the nucleation inhibition reaction to be lower than that of the first coprecipitation reaction;

[0086] Under an oxygen-containing atmosphere, a nickel-cobalt-manganese mixed metal salt solution, a precipitant, and a complexing agent are introduced into the secondary particle slurry, and a second coprecipitation reaction and a third coprecipitation reaction are carried out sequentially to obtain a ternary precursor with high specific surface area and high tap density small particles; wherein, the pH value of the second coprecipitation reaction is higher than that of the third coprecipitation reaction, and the color L value of the second coprecipitation reaction is lower than that of the third coprecipitation reaction.

[0087] In some embodiments, the oxygen-containing atmosphere includes oxygen and / or air; the flow rate of the oxygen-containing atmosphere is increased synchronously with the time point of the increase in the flow rate of the mixed metal salt solution, so that the slurry color is yellowish-brown or brownish-yellow.

[0088] It is important to note that the oxygen-containing atmosphere can adjust the L value of the slurry color. The greater the amount of air introduced, the smaller the L value of the slurry color becomes. If the amount of air introduced is too large, the oxidation of the system will be more severe, and if the amount of air introduced is too small, the oxidation of the system will be less severe. Both of these situations will affect key indicators such as product compaction, specific surface area, and morphology.

[0089] In some embodiments, 2-5 mL of the reaction system slurry is placed in a cuvette and measured using a colorimeter, and the L value is read from the colorimeter.

[0090] In some embodiments, the method for preparing the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0091] (1) The precipitant includes sodium hydroxide and / or potassium hydroxide;

[0092] (2) The complexing agent includes ammonia;

[0093] (3) The concentration of the precipitant is 6-12 mol / L;

[0094] Optionally, the concentration of the precipitant can be 6 mol / L, 8 mol / L, 10 mol / L, 12 mol / L or any value between 6 and 12 mol / L;

[0095] (4) The concentration of the nickel-cobalt-manganese mixed metal salt solution is 1.5-2.5 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 0.50-0.80:0.05-0.20:0.10-0.30.

[0096] Optionally, the concentration of the nickel-cobalt-manganese mixed metal salt solution can be any value between 1.5 mol / L, 2 mol / L, 2.5 mol / L, or 1.5-2.5 mol / L, and the molar ratio of nickel, cobalt, and manganese can be any value between (0.5:0.2:0.3), (0.8:0.05:0.15), (0.6:0.2:0.2), (0.7:0.2:0.1), or 0.50-0.80:0.05-0.20:0.10-0.30.

[0097] In some embodiments, the method for preparing the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0098] (1) The alkalinity of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 7-12 g / L independently;

[0099] Optionally, the alkalinity of the first coprecipitation reaction, the nucleation barrier reaction, the second coprecipitation reaction, and the third coprecipitation reaction can be independently set to 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, or any value between 7 and 12 g / L.

[0100] In some embodiments, the basicity of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction, and the third coprecipitation reaction is the same;

[0101] (2) The temperatures of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 50-70℃.

[0102] Optionally, the temperatures for the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction, and the third coprecipitation reaction can each be independently set to 50°C, 60°C, 70°C, or any value between 50°C and 70°C.

[0103] In some embodiments, the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction, and the third coprecipitation reaction are carried out at the same temperature.

[0104] In some embodiments, the method for preparing the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0105] (1) The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction is 2.2-2.6:1;

[0106] Optionally, the feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction can be any value between 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, or 2.2:2.6:1;

[0107] It is important to note that when the molar ratio of the precipitant to the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction is too small, the pH of the reaction system will decrease during nucleation, reducing the number of nuclei, shortening the cycle, and consequently lowering key indicators such as product compaction. Conversely, when the molar ratio of the precipitant to the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction is too large, the pH of the system will rise significantly, increasing the number of nuclei, lengthening the cycle, and reducing the core size, thereby lowering key indicators such as product specific surface area.

[0108] (2) The pH of the first coprecipitation reaction is 11.70-12.00;

[0109] Optionally, the pH of the first coprecipitation reaction can be 11.70, 11.8, 11.9, 12, or any value between 11.70 and 12;

[0110] (3) The time for the first coprecipitation reaction is 40 min to 120 min.

[0111] Optionally, the time for the first coprecipitation reaction can be any value between 40 min, 60 min, 80 min, 100 min, 120 min, or 40-120 min.

[0112] In some embodiments, the method for preparing the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0113] (1) The pH at the endpoint of the nucleation inhibition reaction is 11.5-11.7;

[0114] Optionally, the pH at the endpoint of the nucleation inhibition reaction can be 11.5, 11.6, 11.7, or any value between 11.5 and 11.7;

[0115] It is important to note that when the pH of the nucleation inhibition reaction is too low, it can lead to severe agglomeration of secondary particles, shorten the cycle time, and potentially alter the crystal growth pattern of the secondary particles, resulting in longer plate-like secondary particles and changes in the morphology, tap, and specific surface area of ​​the product. When the pH of the system is too high, the number of nuclei increases, and small particles may even emerge, leading to a longer cycle time. Simultaneously, it can reduce the core size, affecting key indicators such as the specific surface area and tap of the product.

[0116] (2) The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction is 0.8-1.5:1;

[0117] Optionally, the feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction can be 0.8:1, 1:1, 1.2:1, 1.5:1 or any value between 0.8 and 1.5:1;

[0118] It is important to note that when the feed molar ratio of the precipitant to the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction is too small, the pH of the reaction system drops rapidly during the nucleation inhibition period, resulting in severe secondary particle agglomeration, a shortened cycle, reduced product compaction and other key indicators, and an impact on product sphericity. Conversely, when the feed molar ratio of the precipitant to the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction is too large, the pH of the system drops more slowly, the number of nuclei increases, the cycle lengthens, and the core size decreases, thereby reducing key indicators such as product specific surface area.

[0119] (3) The particle size of the particles in the secondary granular slurry is 1.5-2.0 μm.

[0120] Optionally, the particle size of the particles in the secondary granular slurry can be any value between 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm or 1.5-2μm.

[0121] In some embodiments, the method for preparing the high specific surface area, high tap density small particle ternary precursor satisfies at least one of the following conditions:

[0122] (1) The pH value of the second coprecipitation reaction is 11.5-11.7;

[0123] Optionally, the pH value of the second coprecipitation reaction can be 11.5, 11.6, 11.7 or any value between 11.5 and 11.7;

[0124] (2) The color L value of the second coprecipitation reaction is 34-40;

[0125] Optionally, the color L value of the second coprecipitation reaction can be any value between 34, 36, 38, 40, or 34-40;

[0126] (3) The pH value of the third coprecipitation reaction is 11.0-11.4;

[0127] Optionally, the pH value of the third coprecipitation reaction can be 11.0, 11.1, 11.2, 11.3, 11.4 or any value between 11.0 and 11.4;

[0128] (4) The color L value of the third coprecipitation reaction is 39-45;

[0129] Optionally, the color L value of the third coprecipitation reaction can be any value between 39, 40, 41, 42, 43, 44, 45, or 39-45.

[0130] It is important to note that controlling the pH of the second coprecipitation reaction to 11.5-11.7 primarily controls the morphology of the primary particles. Under these conditions, combined with system oxidation, shorter, interlaced primary particles can be formed, resulting in porous surfaces on the secondary particles and a loose, porous core. This allows the precursor product to simultaneously achieve high specific surface area and high tap density. Controlling the pH of the third coprecipitation reaction to 11.0-11.4 primarily aims to allow subsequent primary particles to intercalate and grow within the pores of the earlier secondary particles after the formation of the smaller, shorter primary particles. Simultaneous system oxidation allows the pores on the secondary particle surface to gradually become denser, ultimately generating secondary spheres with a loose, porous core and a relatively fine outer core. These spheres simultaneously possess high specific surface area and high tap density.

[0131] It should also be noted that in the first and second coprecipitation reactions, the main synergistic effect is that the high alkalinity and high pH system combined with the gradient oxidation method can produce a precursor with a loose and porous core and a relatively dense outer core. This precursor also has the characteristics of high specific surface area and high tap.

[0132] (5) The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the second coprecipitation reaction is gradually increased from 60-200 mL / min to 180-450 mL / min;

[0133] Optionally, the initial flow rate of the nickel-cobalt-manganese mixed metal salt solution in the second coprecipitation reaction can be any value between 60 mL / min, 80 mL / min, 100 mL / min, 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min, 200 mL / min, or 60-200 mL / min, and the endpoint flow rate can be any value between 180 mL / min, 200 mL / min, 250 mL / min, 300 mL / min, 350 mL / min, 400 mL / min, 450 mL / min, or 180-450 mL / min.

[0134] (6) The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the third coprecipitation is 300-600 mL / min;

[0135] Optionally, the flow rate of the nickel-cobalt-manganese mixed metal salt solution in the third coprecipitation can be any value between 300 mL / min, 400 mL / min, 500 mL / min, 600 mL / min, or 300-600 mL / min;

[0136] (7) The particle size of the material at the end of the second coprecipitation reaction is 2.0-2.9 μm;

[0137] Optionally, the particle size of the material at the end of the second coprecipitation reaction can be any value between 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, or 2-2.9μm.

[0138] A third aspect of this application provides a cathode material prepared from the aforementioned high specific surface area, high tap density, small-particle ternary precursor.

[0139] A fourth aspect of this application provides a lithium-ion battery, including the aforementioned positive electrode material.

[0140] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0141] Example 1

[0142] The first aspect of this embodiment provides a high specific surface area, high tap density small particle ternary precursor, including a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core;

[0143] The core consists of secondary particles formed by the accumulation of multiple primary particles. The first and second coating layers are each independently composed of alternating plate-like primary particles. The plate-like primary particles in the first coating layer are shorter and finer than those in the second coating layer. A 30kx cross-sectional view of this high specific surface area, high tap density, small-particle ternary precursor is shown below. Figure 1 As shown, a 5kx cross-sectional SEM is as follows: Figure 2 As shown.

[0144] The second aspect of this embodiment provides a method for preparing a ternary precursor with high specific surface area and high tap density small particles. The concentration of the precipitant sodium hydroxide is 10.8 mol / L, and the concentration of the nickel-cobalt-manganese mixed metal salt solution is 2.2 mol / L. The nickel-cobalt-manganese mixed metal salt solution is prepared from nickel sulfate, cobalt sulfate, and manganese sulfate, wherein the ratio of Ni:Co:Mn is 69.8:7.4:22.8.

[0145] The specific preparation steps are as follows:

[0146] S1: Under a nitrogen atmosphere, inject water into the reactor to fill 60% of the total volume of the reactor. Turn on the stirring (43Hz) and heating (55℃). Simultaneously add concentrated alkali as a precipitant to make its concentration in the reactor 0.05mol / L. After the system stabilizes, introduce ammonia as a complexing agent to make the alkalinity in the reactor 8.5g / L. Maintain constant temperature and alkalinity during the subsequent reaction process.

[0147] S2: Under a nitrogen atmosphere, a nickel-cobalt-manganese mixed metal salt solution with a flow rate of 90 mL / min and a concentrated alkali with a flow rate of 46 mL / min are introduced into the reactor to make the molar ratio of concentrated alkali to mixed metal salt 2.5:1 (pH 11.70-11.90, pH will gradually increase). Ammonia water is introduced simultaneously and concurrently to carry out the first coprecipitation reaction for 1.25 h to complete the nucleation reaction.

[0148] S3: After the nucleation reaction is completed, adjust the flow rate of concentrated alkali to 20 mL / min, so that the molar ratio of concentrated alkali to mixed metal salt is 1.1:1, rapidly reduce the pH of the system to about 11.65 and maintain it, so that the particles agglomerate into spheres and complete the nucleation inhibition reaction. Ammonia water is introduced throughout the process.

[0149] S4: After nucleation inhibition is completed, the growth stage begins (the second coprecipitation reaction occurs before 50 hours, and the third coprecipitation reaction occurs after 50 hours). Mixed metal salts are introduced in stages, with the following flow rates: 0-10 hours: 90 mL / min, 10-20 hours: 135 mL / min, 20-35 hours: 200 mL / min, 35-50 hours: 300 mL / min; 50 hours until the target particle size is achieved: 450 mL / min. After 3 hours of feeding, air is introduced into the system at a specific flow rate for staged oxidation, as follows: During 3-10 hours, the slurry color L value is maintained at 40-48; during 10-30 hours, the slurry color L value is maintained at 35-38; during 30-50 hours, the slurry color L value is maintained at 38-40; and at 50 hours until the target particle size of 3.25 μm is achieved, the slurry color L value is maintained at 41-45. Meanwhile, the pH of the system was controlled in stages by adjusting the flow rate of concentrated alkali. Specifically, the pH of the system was maintained between 11.55 and 11.65 from the end of nucleation inhibition to 50 hours; after 50 hours, the pH of the system was maintained between 11.20 and 11.40 until the particle size was achieved.

[0150] S5: After the slurry particle size reaches 3.25um, the slurry is aged and washed using a centrifuge. After washing until pH < 8.2, it is dehydrated. The slurry is then dried at 140℃ to obtain a high specific surface area and high tap density ternary precursor with loose and porous interior and relatively fine exterior.

[0151] Among them, the surface SEM of the high specific surface area, high tap density, small particle ternary precursor at 1000x magnification is as follows: Figure 3 As shown; 5000x surface SEM Figure 4 As shown; 20,000x surface SEM Figure 5 As shown.

[0152] Example 2

[0153] The difference from Example 1 is that in step S4, the pH is 11.55-11.70 before 50 hours (second coprecipitation reaction) and 11.10-11.30 after 50 hours (third coprecipitation reaction).

[0154] Example 3

[0155] The difference from Example 1 is that in step S4, the flow rate of the mixed metal salt before 50 hours (second coprecipitation reaction) is gradually increased from 135 mL / min to 450 mL / min; and the flow rate of the mixed metal salt after 50 hours (third coprecipitation reaction) is 600 mL / min.

[0156] Example 4

[0157] The difference from Example 1 is that in step S4, the slurry color L value before 50 hours (second coprecipitation reaction) is 34-38; and the slurry color L value of the mixed metal salt after 50 hours (third coprecipitation reaction) is 39-42.

[0158] Comparative Example 1

[0159] The difference from Example 1 is that step S3 is not performed, that is, the nucleation inhibition reaction is not performed.

[0160] Comparative Example 2

[0161] The difference from Example 1 is that the second coprecipitation reaction is not carried out, and the parameters of the third coprecipitation reaction are directly used to prepare the sample until the target particle size is obtained.

[0162] Comparative Example 3

[0163] The difference from Example 1 is that the third coprecipitation reaction is not performed; instead, the parameters of the second coprecipitation reaction are used directly to prepare the sample until the target particle size is obtained.

[0164] Comparative Example 4

[0165] The difference from Example 1 is that the order of the second coprecipitation reaction and the third coprecipitation reaction is changed, that is, the order of the first coating layer and the second coating layer is changed.

[0166] Comparative Example 5

[0167] The difference from Example 1 is that in step S4, the pH is kept constant throughout the process, between 11.55 and 11.65.

[0168] Comparative Example 6

[0169] The difference from Example 1 is that in step S4, the flow rate of the mixed metal salt is kept constant at 450 mL / min throughout the process.

[0170] Comparative Example 7

[0171] The difference from Example 1 is that in step S4, the L value of the slurry color is controlled to remain constant at 35-38.

[0172] The relevant parameters of the ternary precursors prepared in the above embodiments and comparative examples are shown in Table 1.

[0173] Table 1 Relevant Parameters

[0174]

[0175] Lithium hydroxide was mixed with the precursors prepared in all examples and comparative examples at a molar ratio of 1.06:1 in a high-speed mixer to obtain a positive electrode material using a three-stage sintering process. The electrochemical performance of this positive electrode material was tested using a button cell. The above-mentioned positive electrode material, conductive carbon black, and binder PVDF (polyvinylidene fluoride) were mixed in a ratio of 8.5:1.5:1.5 to form a slurry, which was then coated onto aluminum foil to form a positive electrode sheet. A lithium metal sheet was used as the negative electrode sheet, and a 1 mol / L LiPF6 / EC:DMC electrolyte (volume ratio 1:1) was used. The battery casing, positive and negative electrode sheets, separator, spring contacts, and gaskets were assembled into a button cell in a vacuum glove box. Electrochemical performance was tested using a Blue Electric testing system under conditions of 2.8–4.4 V and 25 °C, including 1C / 1C charge / discharge capacity, initial coulombic efficiency, and powder resistivity. Specific test results are shown in Table 2.

[0176] Table 2 Electrochemical Performance Tests

[0177]

[0178] analyze:

[0179] The results above show that Examples 1-4 produced precursors with high specific surface area and high tap density due to their porous internal structure and relatively dense external structure. The porous internal structure provides abundant interfaces for lithium-ion insertion / extraction reactions, significantly reducing the resistance to lithium-ion transport within the particles and facilitating lithium-ion diffusion. The relatively dense external structure forms a "protective layer," effectively reducing the direct contact area between the cathode material and the electrolyte, mitigating interfacial side reactions, and thus resulting in high initial coulombic efficiency. Comparative Examples 2 and 6 produced precursors with long, coarse, and densely packed particles with high tap density and low specific surface area, which is detrimental to lithium-ion diffusion. Comparative Examples 3, 4, and 7 all had porous external structures. During sintering, the porous structure resulted in uneven lithiation, and some areas may have formed lithium-deficient phases or excessive residual alkali. These phases have little or no electrochemical activity, leading to low initial charge / discharge efficiency. Comparative Example 1 continuously produced nuclei, and the precursor particle size was substandard, so it was not fed into the system. In Comparative Example 5, due to the high pH control during the later stage of the reaction, a small number of small particles re-emerged, resulting in a wide particle size distribution. After sintering, these small particles react with lithium salt more easily and rapidly, which may lead to local overburning and the formation of inactive rock salt or spinel phases. Large particles may have incomplete reactions (underburning), resulting in poor consistency of the cathode material, which prevents the overall capacity from being fully utilized and leads to low initial charge and discharge efficiency.

[0180] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0181] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A high specific surface area, high tap density, small-particle ternary precursor, characterized in that, It includes a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core; The core is a secondary particle formed by the stacking of multiple primary particles; The first coating layer and the second coating layer are each independently composed of alternating sheet-like primary particles; The sheet-like primary particles of the first coating layer are shorter than the sheet-like primary particles of the second coating layer; The general structural formula of the high specific surface area, high tap density, small-particle ternary precursor is Ni. x Co y Mn z (OH)2, where x+y+z=1, 0.50≤x≤0.80, 0.05≤y≤0.20, 0.10≤z≤0.30; The preparation method of the high specific surface area, high tap density small particle ternary precursor includes: Under an inert atmosphere, a nickel-cobalt-manganese mixed metal salt solution, precipitant, and complexing agent are introduced into a base solution containing a precipitant and a complexing agent to carry out a first coprecipitation reaction to obtain seed crystals; Continue to pass in a mixed metal salt solution of nickel, cobalt and manganese, a precipitant and a complexing agent to carry out a nucleation inhibition reaction to obtain a secondary particulate slurry, and control the pH value in the nucleation inhibition reaction to be lower than that in the first coprecipitation reaction; Under an oxygen-containing atmosphere, a nickel-cobalt-manganese mixed metal salt solution, a precipitant, and a complexing agent are introduced into the secondary particle slurry, and a second coprecipitation reaction and a third coprecipitation reaction are carried out sequentially to obtain a high specific surface area and high tap density small particle ternary precursor; wherein, the pH value of the second coprecipitation reaction is higher than that of the third coprecipitation reaction, and the color L value of the second coprecipitation reaction is lower than that of the third coprecipitation reaction. The pH of the first coprecipitation reaction is 11.70-12.00; the endpoint pH of the nucleation inhibition reaction is 11.5-11.7; the pH of the second coprecipitation reaction is 11.5-11.7; and the pH of the third coprecipitation reaction is 11.0-11.

4. The precipitant includes sodium hydroxide and / or potassium hydroxide; The complexing agent includes ammonia; The concentration of the precipitant is 6-12 mol / L; The concentration of the nickel-cobalt-manganese mixed metal salt solution is 1.5-2.5 mol / L, wherein the molar ratio of nickel, cobalt and manganese is 0.50-0.80:0.05-0.20:0.10-0.30; The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the first coprecipitation reaction is 2.2-2.6:1; The feed molar ratio of the precipitant and the nickel-cobalt-manganese mixed metal salt solution in the nucleation inhibition reaction is 0.8-1.5:1; The color L value of the second coprecipitation reaction is 34-40; The color L value of the third coprecipitation reaction is 39-45; The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the second coprecipitation reaction was gradually increased from 60-200 mL / min to 180-450 mL / min; The flow rate of the nickel-cobalt-manganese mixed metal salt solution in the third coprecipitation is 300-600 mL / min.

2. The high specific surface area, high tap density, small particle ternary precursor according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The particle size of the high specific surface area and high tap density small particle ternary precursor is 2.75-3.75 μm; (2) The tap density of the high specific surface area, high tap density small particle ternary precursor is 1.55-1.75 g / cm³. 3 ; (3) The particle size of the kernel is 1.5-2.0 μm; (4) The thickness of the first coating layer is 0-0.7 μm, and the thickness is not 0; (5) The length of the primary particles in the first coating layer is 0.1-0.4 μm; (6) The thickness of the second coating layer is 0.1-0.5 μm; (7) The length of the primary particles in the second coating layer is 0.3-0.6 μm; (8) The specific surface area of ​​the high specific surface area, high tap density, small particle ternary precursor is 12-20 m². 2 / g.

3. The high specific surface area, high tap density, small particle ternary precursor according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The alkalinity of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 7-12 g / L independently; (2) The temperatures of the first coprecipitation reaction, the nucleation inhibition reaction, the second coprecipitation reaction and the third coprecipitation reaction are each 50-70℃.

4. The high specific surface area, high tap density, small particle ternary precursor according to claim 1, characterized in that, The time for the first coprecipitation reaction is 40 min to 120 min.

5. The high specific surface area, high tap density, small particle ternary precursor according to claim 1, characterized in that, The particle size of the particles in the secondary granular slurry is 1.5-2.0 μm.

6. The high specific surface area, high tap density small particle ternary precursor according to any one of claims 1-5, characterized in that, The particle size of the material at the end of the second coprecipitation reaction is 2.0-2.9 μm.

7. A positive electrode material, characterized in that, Including the high specific surface area, high tap density small particle ternary precursor as described in any one of claims 1-6.

8. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 7.

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