Positive electrode material precursor and preparation method thereof, positive electrode material and battery

Abstract

The invention provides a positive electrode material precursor, a preparation method thereof, a positive electrode material and a battery, and relates to the technical field of secondary batteries. The positive electrode material precursor comprises a crystal nucleus region, a middle region and an outer layer region from inside to outside; in the direction from inside to outside, the porosity of the middle area is gradually increased, and the porosity of the outer layer area is larger than that of the middle area. The porosity of the positive electrode material precursor is limited to be sequentially increased along the radial direction, so that the positive electrode material prepared from the positive electrode material precursor has high capacity and excellent cycle stability.

Description

Technical Field

[0001] The present application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode material precursor and a preparation method thereof, a positive electrode material, and a battery. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices and new energy vehicles due to their low self-discharge rate, wide operating temperature range, and flexible shape and size. The cathode material is key to the energy storage and release during the charge and discharge process of lithium-ion batteries. The structure of the cathode material largely inherits that of the cathode material precursor, which is reflected in its performance. Therefore, the performance of the cathode material precursor directly affects the capacity, cycle stability, and cycle life of the lithium-ion battery.

[0003] Currently, in the preparation process of cathode material precursors, a precipitant and a metal salt are mostly reacted in a hydrothermal reactor to form seed grains, which are then increased in size to form the cathode material precursor. Currently, the porosity of cathode material precursors is difficult to control. Excessively low porosity not only affects the diffusion of lithium ions during cathode sintering, but also reduces and shortens active sites and ion diffusion channels, hindering the transport and storage of ions in the electrolyte and resulting in poor cycle stability. While excessively high porosity facilitates lithium ion diffusion and electrolyte penetration, excessive pores reduce the material's density, thereby affecting the capacity of the cathode material. Summary of the Invention

[0004] The main purpose of this application is to provide a positive electrode material precursor and its preparation method, positive electrode material and battery, so as to solve the problem that the existing positive electrode material precursor is difficult to achieve both high capacity and excellent cycle stability.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode material precursor, which includes a crystal core region, a middle region and an outer region from the inside to the outside; along the direction from the inside to the outside, the porosity of the middle region gradually increases, and the porosity of the outer region is greater than the porosity of the middle region.

[0006] Furthermore, the cathode material precursor satisfies at least one of the following conditions:

[0007] a. The diameter of the crystal nucleus region is 1 to 5 μm;

[0008] b. From the inside out, the middle region includes at least two middle layers; preferably, the middle region includes a first middle layer and a second middle layer, or the middle region includes a first middle layer, a second middle layer, and a third middle layer, wherein the thickness of the first middle layer, the second middle layer, and the third middle layer are each independently 1 to 3 μm, and the porosity of the first middle layer is less than the porosity of the second middle layer, less than the porosity of the third middle layer, and less than the porosity of the outer region;

[0009] Preferably, the porosity of the first intermediate layer is less than 2%, the porosity of the second intermediate layer is 2% to 4%, the porosity of the third intermediate layer is 4% < 5%, and the porosity of the outer layer region is 3% < 10%.

[0010] c. The overall average porosity of the positive electrode material precursor is 3.0% to 5.5%.

[0011] Furthermore, the cathode material precursor satisfies at least one of the following conditions:

[0012] a. The D50 particle size of the cathode material precursor is 6μm to 30μm;

[0013] b. The specific surface area of ​​the cathode material precursor is 3m 2 / g~30m 2 / g;

[0014] c. The particles of the cathode material precursor are spherical or quasi-spherical, with a sphericity of 0.77 to 0.99;

[0015] d. The tap density of the cathode material precursor is 1.5 g / cm 3 ~2.5g / cm 3 ;

[0016] e. The cathode material precursor has a diffraction peak of the (001) crystal plane and a diffraction peak of the (101) crystal plane in the X-ray diffraction pattern, and the diffraction peak intensity of the (001) crystal plane I(001) and the diffraction peak intensity of the (101) crystal plane I(101) satisfy: I(101) / I(001)=0.7~1.2;

[0017] f. The particle size distribution width SPAN of the positive electrode material precursor is 0.25~0.85.

[0018] Furthermore, the cathode material precursor includes secondary particles formed by stacking primary particles;

[0019] The primary particles in the core region, the first intermediate layer, and the second intermediate layer are in the shape of flakes, rods, or blocks; the primary particles in the third intermediate layer and the outer layer are in the shape of spindles.

[0020] Preferably, when the primary particles have a spindle-shaped morphology, the average length of the primary particles is 220 to 600 nm, and the average width is 50 to 80 nm;

[0021] When the primary particle morphology is flaky, the average thickness of a single lamella of the primary particle is 5 to 200 nm, the average length of a single lamella of the primary particle is 200 to 450 nm, and the number of lamellae of the primary particle is ≥3;

[0022] When the primary particles are rod-shaped, the aspect ratio of the primary particles is 20-200.

[0023] Furthermore, the chemical formula of the cathode material precursor includes Ni x Co y M z T k (OH) 2-k , M is selected from at least one of Mn, Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, and Al, and T is selected from at least one of F, P, B, and O; wherein 0 <x≤1,0≤y<1,0≤z<1,0≤k<1;

[0024] Preferably, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, and 0≤k≤0.5.

[0025] In a second aspect of the present application, a method for preparing a positive electrode material precursor is provided, comprising the following steps:

[0026] S1, adding a metal salt solution, a precipitant, and a complexing agent to a first reaction base solution to form a first reaction system; and allowing the first reaction system to undergo a first growth to obtain a seed crystal;

[0027] S2, adding a metal salt solution, a precipitant, and a complexing agent to a second reaction base solution containing seed crystals to form a second reaction system; and causing the second reaction system to undergo a second growth to obtain a cathode material precursor;

[0028] In the second growth process, the feeding rate of the metal salt solution is gradually increased, and the feeding rates of the precipitant and the complexing agent are first gradually increased and then gradually decreased.

[0029] Furthermore, the preparation method satisfies at least one of the following conditions:

[0030] a. During the second growth period of 0 to 2 hours, the feeding rate of the metal salt solution is D1; ​​during the second growth period of 2 hours to 10 hours, the feeding rate of the metal salt solution is increased uniformly at a rate of 1 L / h to 5 L / h to D2; after 10 hours of the second growth, the feeding rate of the metal salt solution is D2, where D2>D1;

[0031] Preferably, D1 and D2 are each independently 10 L / h to 60 L / h;

[0032] b. During the second growth period of 0 to 2 hours, the feeding rate of the complexing agent is E1; during the second growth period of 2 hours to 10 hours, the feeding rate of the complexing agent is increased at a uniform rate of 0.1L / h to 1L / h to E2; during the second growth period of 10 hours to 16 hours, the feeding rate of the complexing agent is E2; during the second growth period of 16 hours to 18 hours, the feeding rate of the complexing agent is decreased at a uniform rate of 0.1L / h to 1L / h to E3; after 18 hours of the second growth period, the feeding rate of the complexing agent is E3; wherein, E2>E3>E1;

[0033] Preferably, E1, E2, and E3 are each independently 0.4 L / h to 10 L / h;

[0034] c. During the second growth period of 0 to 2 hours, the feed flow rate of the precipitant is H1. During the second growth period of 2 hours to 10 hours, the feed flow rate of the precipitant is increased at a uniform rate of 0.2L / h to 2L / h to H2. During the second growth period of 10 hours to 16 hours, the feed flow rate of the precipitant is H2. During the second growth period of 16 hours to 18 hours, the feed flow rate of the precipitant is decreased at a uniform rate of 0.2L / h to 2L / h to H3. After 18 hours of the second growth, the feed flow rate of the precipitant is H3. Among them, H2>H3>H1.

[0035] Preferably, H1, H2, and H3 are each independently 5 L / h to 20 L / h;

[0036] d. During the second growth period of 0 to 15 hours, the pH value of the second reaction system at 45°C is F1; during the second growth period of 15 to 18 hours, the pH value of the second reaction system decreases uniformly at a rate of 0.002 / h to 0.3 / h at 45°C to F2; after 18 hours of the second growth, the pH value of the second reaction system at 45°C is F2; ​​wherein F1>F2;

[0037] Preferably, F1 and F2 are each independently 10.35 to 10.60 at 45°C;

[0038] e. During the second growth period of 0 to 2 hours, the ammonia concentration of the second reaction system is G1; during the second growth period of 2 hours to 10 hours, the ammonia concentration of the second reaction system increases uniformly at a rate of 0.05 g / L·h to 0.3 g / L·h to G2; during the second growth period of 10 hours to 16 hours, the ammonia concentration of the second reaction system is G2; during the second growth period of 16 hours to 18 hours, the ammonia concentration of the second reaction system decreases uniformly at a rate of 0.05 g / L·h to 0.3 g / L·h to G3; after 18 hours of the second growth, the ammonia solubility of the second reaction system is G3; wherein, G2>G3>G1;

[0039] Preferably, G1, G2, and G3 are 2.2 g / L to 4.6 g / L;

[0040] f. During the second growth process, the stirring speed of the second reaction system is gradually reduced.

[0041] Furthermore, the preparation method satisfies at least one of the following conditions:

[0042] a. The metal salt solution comprises a soluble salt of a nickel salt and a cobalt salt, wherein the soluble salt comprises at least one of a nitrate, a chloride, and a sulfate, and the concentration of the metal salt in the metal salt solution is 120 g / L to 145 g / L; preferably, the metal salt further comprises at least one of a salt formed by an M element and a salt formed by an T element;

[0043] b. The complexing agent includes an aqueous ammonia solution, wherein the concentration of NH3 in the aqueous ammonia solution is 7% to 10%;

[0044] c. The precipitant includes a sodium hydroxide solution having a concentration of 200 g / L to 450 g / L;

[0045] d. The solid content of the first reaction system and the second reaction system is independently 400 g / L to 800 g / L.

[0046] e. The ammonia concentration of the first reaction bottom solution is 3.0 g / L ~ 4.5 g / L, and the pH value of the first reaction bottom solution is 10.55 ~ 11.95 at 45 ° C;

[0047] f. The ammonia concentration of the second reaction bottom solution is 1.0 to 4.0 g / L, and the pH value of the second reaction bottom solution is 10.40 to 11.80 at 45°C;

[0048] g. The reaction temperature of the first growth and the second growth is 50 ℃ ~ 90 ℃;

[0049] h. Both the first growth and the second growth are carried out under stirring, and the stirring speed is 50 rpm to 500 rpm.

[0050] The third aspect of the present application provides a positive electrode material, which is prepared by calcining a positive electrode material precursor and a lithium source, wherein the positive electrode material precursor includes the positive electrode material precursor provided by the first aspect or the positive electrode material precursor prepared by the preparation method provided by the second aspect.

[0051] The fourth aspect of the present application provides a battery comprising the positive electrode material provided in the third aspect.

[0052] By applying the technical solution of the present application, by limiting the porosity of the positive electrode material precursor to increase radially, the distribution of the porosity is controlled, which helps to improve structural stability, reduce internal stress, and lower impedance. In addition, in the subsequent sintering process to prepare the positive electrode material, it is beneficial for molten lithium ions to penetrate and migrate into the interior of the particles, thereby improving the uniformity of the lithium sintering process of the positive electrode material precursor, and greatly promoting the rapid penetration and diffusion of the electrolyte, so that the positive electrode material has high capacity and excellent cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0054] Figure 1 This is an SEM image of the cathode material precursor of Example 1;

[0055] Figure 2 This is a primary particle morphology image of the outer layer of the positive electrode material precursor of Example 1;

[0056] Figure 3 is a cross-sectional view of the positive electrode material precursor of Example 1;

[0057] Figure 4 This is an SEM image of the cathode material precursor of Example 2;

[0058] Figure 5 This is a primary particle morphology image of the outer layer of the positive electrode material precursor of Example 2;

[0059] Figure 6 is a cross-sectional view of the positive electrode material precursor of Example 2;

[0060] Figure 7 This is an SEM image of the cathode material precursor of Comparative Example 1;

[0061] Figure 8 This is a primary particle morphology of the positive electrode material precursor of Comparative Example 1;

[0062] Figure 9 is a cross-sectional view of the positive electrode material precursor of Comparative Example 1;

[0063] Figure 10 This is an SEM image of the cathode material precursor of Comparative Example 2;

[0064] Figure 11 This is a primary particle morphology of the positive electrode material precursor of Comparative Example 2;

[0065] Figure 12 This is a cross-sectional view of the positive electrode material precursor of Comparative Example 2. DETAILED DESCRIPTION

[0066] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the embodiments.

[0067] As described in the background art, existing cathode material precursors struggle to achieve both high capacity and excellent cycle stability. To address the aforementioned technical issues, the present application provides a cathode material precursor comprising, from the inside out, a crystal core region, a middle region, and an outer region; the porosity of the middle region gradually increases from the inside out, and the porosity of the outer region is greater than that of the middle region.

[0068] The cathode material precursor of the present application can be divided radially from the inside out into a core region, an intermediate region, and an outer region. The core region, as the innermost layer, has a low porosity, providing a stable starting point for subsequent particle growth. The porosity of the material gradually increases radially from the core region outward.

[0069] The porosity of the central region is higher than that of the core region, and this increase is gradual, starting from the edge of the central region close to the core region to the outermost edge of the central region farthest from the core region. This design facilitates the formation of a more efficient lithium ion diffusion path within the material, while also buffering the anisotropic stress of the lattice during charge and discharge, improving the material's structural stability and cycling performance.

[0070] Specifically, the middle region, close to the crystal nucleus, has the lowest porosity and a dense structure. This indicates that the particles are closely packed together, allowing for a high nickel content and high energy density to be maintained during sintering to prepare the cathode material. Furthermore, this structure helps reduce excessive lithium ion diffusion during charge and discharge, preventing structural instability and increasing the material's structural strength, thereby improving the electrochemical performance and cycling stability of the cathode material.

[0071] The porosity of the middle region near the outer layer is further increased compared to the region near the crystal core, which can be used to release the anisotropic stress of the lattice during charging and discharging, that is, the internal stress generated during charging and discharging, reduce the formation of microcracks, ensure the stability of the material structure, and reduce impedance.

[0072] The porosity of the outer region is further increased compared to the porosity of the middle region, forming a looser structure. The outer region has the highest porosity, which helps to increase the contact area of ​​the active sites, promote the rapid diffusion of lithium ions, and improve the capacity and rate performance of the battery. Secondly, it is conducive to improving the permeability of the electrolyte and the wettability of the electrode material, which helps to improve the high-rate charging capability of the battery. At the same time, due to the increase in porosity, it can provide more sufficient space to buffer the volume changes during the charge and discharge process, reduce structural stress, and extend the battery life. In addition, the high-porosity outer region provides a wider path and space, ensuring the effective migration of lithium ions and improving the cycle stability and safety of the battery.

[0073] It should be noted that the present application does not limit the porosity change of the core region and the outer region from the inside to the outside, which may be gradually increasing, constant, or gradually decreasing. The present application does not impose any further limitations here.

[0074] Among them, porosity refers to the percentage of the pore area in the corresponding area to the total area of ​​the corresponding area on the cross section or cross section of the particle. Porosity can be obtained by cross-section testing. Specifically, a sufficiently representative sample is selected from the cathode material precursor, and the particles are cut to obtain a cross section or cross section; a cross-section image is obtained using a scanning electron microscope (SEM) or a transmission electron microscope (TEM); the obtained cross-section image is analyzed, and the pores and materials are marked with different gray values ​​or colors, respectively, and the total area of ​​the material part and the total area of ​​the pore part are calculated. The porosity is calculated according to the following formula: Porosity = total area of ​​pores in the corresponding area / (total area of ​​pores in the corresponding area + total area of ​​material in the corresponding area) × 100%.

[0075] The present application limits the porosity of the positive electrode material precursor to increase radially, and by controlling the distribution of the porosity, it can not only avoid stress concentration inside the positive electrode material precursor and alleviate particle cracking, but also ensure the structural stability of the positive electrode material precursor with a high nickel content and reduce impedance; secondly, in the process of mixed sintering of the positive electrode material precursor and the lithium source to prepare the positive electrode material, it is conducive to the penetration and migration of molten lithium ions into the interior of the particles, thereby improving the uniformity of the lithiation sintering process of the positive electrode material precursor, and making the prepared positive electrode material have a high capacity; in addition, by increasing the porosity along the radial direction, it greatly promotes the rapid penetration and diffusion of the electrolyte, ensures the effective migration of lithium ions, and improves the cycle stability of the battery.

[0076] In some embodiments, r is the perpendicular distance from the center of the positive electrode material precursor particle to the outermost surface of the particle. The core region is the region extending from the center of the particle to the outermost surface (5% to 25%) of r. The outer region is the region extending from the outermost surface to the center of the particle (40% to 60%) of r. The intermediate region is located between the core region and the outer region.

[0077] In some embodiments, the diameter of the crystal nucleus region is 1 to 5 μm. Limiting the diameter of the crystal nucleus region to 1 to 5 μm helps form a dense core, providing a stable growth substrate for subsequent layers. Such a crystal nucleus region not only has high structural strength but also effectively maintains the stability of the high-nickel material during the sintering process, which is beneficial for improving the battery's capacity and cycle performance.

[0078] In some embodiments, along an inside-out direction, the intermediate region includes at least two intermediate layers.

[0079] Specifically, in some embodiments, the intermediate region includes a first intermediate layer and a second intermediate layer, and the porosity of the first intermediate layer and the second intermediate layer gradually increases. Thus, the positive electrode material precursor includes, from the inside out, a crystal core region, a first intermediate layer, a second intermediate layer, and an outer region, and the porosity of the first intermediate layer is less than the porosity of the second intermediate layer and less than the porosity of the outer region.

[0080] In other embodiments, the intermediate region includes a first intermediate layer, a second intermediate layer, and a third intermediate layer, and the porosity of the first intermediate layer, the second intermediate layer, and the third intermediate layer gradually increases. Thus, the positive electrode material precursor includes, from the inside out, a crystal core region, a first intermediate layer, a second intermediate layer, a third intermediate layer, and an outer region, and the porosity of the first intermediate layer is less than the porosity of the second intermediate layer, less than the porosity of the third intermediate layer, and less than the porosity of the outer region.

[0081] Specifically, the first intermediate layer has the lowest porosity and dense structure. This indicates that the particles in the first intermediate layer are closely packed together, which helps maintain a high nickel content and achieve high energy density during sintering to prepare the positive electrode material. Furthermore, this structure helps reduce excessive diffusion of lithium ions during charge and discharge, prevents structural instability, and improves the structural strength of the material, thereby contributing to improved electrochemical performance and cycle stability of the positive electrode material.

[0082] The porosity of the second intermediate layer is further improved compared to the first intermediate layer. The second intermediate layer can be used to release the anisotropic stress of the lattice during the charging and discharging process, that is, the internal stress generated during the charging and discharging process, reduce the formation of microcracks, ensure the stability of the material structure, and reduce impedance.

[0083] The porosity of the third intermediate layer increases again compared to the second intermediate layer, indicating that the particles in the third intermediate layer are arranged loosely, which helps to increase the contact area of ​​the active sites, promote the rapid diffusion of lithium ions, and improve the capacity and rate performance of the battery. Secondly, it is beneficial to improve the permeability of the electrolyte and the wettability of the electrode material, which helps to improve the high-rate charging capability of the battery. At the same time, due to the increase in porosity, it can provide more sufficient space to buffer the volume changes during the charge and discharge process, reduce structural stress, and extend battery life.

[0084] The outer layer has the highest porosity, indicating that the pores between the particles are further increased, greatly promoting the rapid penetration and diffusion of the electrolyte, which is conducive to achieving high capacity and high rate performance of the battery. In addition, the high-porosity outer layer provides a wider path and space, ensuring the effective migration of lithium ions and improving the cycle stability and safety of the battery.

[0085] In order to further improve the electrochemical performance of lithium-ion batteries in a targeted manner, the present application can specifically limit the porosity range of different radial layers of the positive electrode material precursor to maintain low porosity and dense structure, which is conducive to improving the compaction density of the material, thereby further improving the capacity and energy density of the battery.

[0086] Specifically, the porosity of the second intermediate layer is 2% to 4%, for example, 2%, 2.5%, 3%, 3.5%, 4% or a range consisting of any two of them. By limiting the porosity of the second intermediate layer to 2% to 4%, the anisotropic stress of the lattice can be released during the charge and discharge process, while still maintaining moderate structural strength and lithium ion conductivity, ensuring that the diffusion path of lithium ions inside the material is more unobstructed, which helps to further improve the rate performance of the battery. The porosity of the third intermediate layer is 4% < ≤ 5%. By limiting the porosity of the third intermediate layer to 4% < ≤ 5%, it is beneficial for the electrolyte to penetrate deeper into the interior of the material, promote the contact between lithium ions and active sites, and further improve the capacity and charge and discharge efficiency of the battery.

[0087] In some embodiments, the porosity of the outer region is 3% < ≤ 10%. By limiting the porosity range of the outer region, sufficient buffer space can be provided for volume changes during charge and discharge, avoiding the concentration of structural stress, reducing the risk of cracks and fractures, thereby extending the cycle life of the battery and further improving the overall cycle stability. Furthermore, the porosity of the outer region is preferably 3.1% to 6%, for example, 3.1%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or a range consisting of any two thereof.

[0088] By limiting the porosity range of different layers, this application can reduce the uneven shrinkage of the positive electrode material precursor during the sintering process, improve the consistency of the material, and further improve the consistency between battery batches and the uniformity of the electrodes, ensuring that the performance of the battery in actual applications is more stable.

[0089] In some embodiments, the overall average porosity of the cathode material precursor is 3.0% to 5.5%. By defining an appropriate overall average porosity, a balance can be found between improving lithium ion transmission efficiency and maintaining high energy density. In addition, by defining an appropriate porosity, it is ensured that the material still maintains good ion transmission capability during the compaction process, without causing a decrease in compaction density due to excessive pores, which affects the energy density of the battery.

[0090] This application does not limit the size of each radial layer, which can be adjusted according to actual needs. The thickness of the first intermediate layer is 1 to 3 μm; and / or, the thickness of the second intermediate layer is 1 to 3 μm; and / or, the thickness of the third intermediate layer is 1 to 3 μm. By limiting the thickness of the first intermediate layer, the second intermediate layer and the third intermediate layer to 1 to 3 μm, this thickness range ensures that the process of gradually increasing the porosity from the crystal core area to the outside is smooth and controllable. In this way, while maintaining the continuity and consistency of the material structure, the porosity is gradually increased, avoiding affecting the consistency and processing performance of the material, thereby further optimizing the diffusion path of lithium ions and the electrochemical performance of the battery.

[0091] In some embodiments, the D50 particle size of the cathode material precursor is 6 μm to 30 μm, for example, 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any two thereof. By limiting the D50 particle size of the cathode material precursor to 6 μm to 30 μm, efficient lithium ion transport is ensured while maintaining a good compaction density, thereby improving the energy density of the battery.

[0092] In some embodiments, the specific surface area of ​​the cathode material precursor is 3 m 2 / g~30m 2 / g, for example 3m 2 / g、5m 2 / g、10m 2 / g、15m 2 / g, 20m 2 / g, 25m 2 / g、30m 2 / g or a range consisting of any two thereof. Specifically, the specific surface area (SSA) refers to the total surface area per unit mass of the positive electrode material precursor. By limiting the specific surface area of ​​the positive electrode material precursor to the above range, efficient lithium ion transmission is ensured while maintaining a high compaction density, which is conducive to improving the capacity and energy density of the battery.

[0093] In some embodiments, the particles of the positive electrode material precursor are spherical or quasi-spherical, and the sphericity is 0.77 to 0.99, for example, 0.77, 0.8, 0.85, 0.9, 0.95, 0.99 or a range consisting of any two thereof. Wherein, sphericity refers to the degree to which the particles are close to a sphere. The present application can calculate the sphericity by the following formula: Sphericity γ = 4πS / L 2 , where S is the cross-sectional area of ​​the cathode material precursor particle and L is the perimeter of the cross-sectional area. The closer the sphericity value is to 1, the closer the secondary particle shape is to a perfect sphere.

[0094] By limiting the particle morphology and sphericity of the positive electrode material precursor, it can be ensured that it can be arranged more closely during the compaction process to form smaller gaps, thereby increasing the compaction density of the positive electrode material; secondly, the spherical or quasi-spherical structure helps to evenly distribute the transmission path of lithium ions, reduce the internal resistance of the electrode material, and accelerate the diffusion rate of lithium ions, thereby further improving the battery's rate performance and charge and discharge rate; in addition, particles with high sphericity shrink and expand more consistently during the sintering process, which can reduce the uneven distribution of stress between particles, reduce the generation of microcracks, improve the electrochemical stability of the positive electrode material, and extend the cycle life of the battery.

[0095] In some embodiments, the tap density of the cathode material precursor is 1.5 g / cm 3 ~2.5g / cm 3 , for example 1.5g / cm 3 , 1.8g / cm 3 , 2g / cm 3 , 2.2g / cm 3 , 2.5g / cm 3 Or a range consisting of any two of them. Tap density (Tap) refers to the compactness of a material under physical vibration. A higher tap density means that more active materials can be accommodated in the same volume, thereby increasing the energy density of the battery. This application limits the tap density of the positive electrode material precursor to 1.5g / cm 3 ~2.5g / cm 3 , which can ensure that the positive electrode material achieves high energy density while maintaining a good ion transport path.

[0096] In some embodiments, the positive electrode material precursor has a diffraction peak of the (001) crystal plane and a diffraction peak of the (101) crystal plane in the X-ray diffraction pattern, and the diffraction peak intensity I(001) of the (001) crystal plane and the diffraction peak intensity I(101) of the (101) crystal plane satisfy: I(101) / I(001)=0.7~1.2, for example, 0.7, 0.8, 0.9, 1, 1.1, 1.2 or a range composed of any two of them.

[0097] The cathode material precursor can obtain an X-ray diffraction pattern through X-ray diffraction (XRD), which has diffraction peaks of (101) crystal plane and (001) crystal plane. The intensity of the diffraction peak directly reflects the atomic arrangement density, lattice integrity and crystal defects of the crystal plane.

[0098] Specifically, the ratio of I(101) / I(001) reflects the characteristics of the material's crystal structure, which is related to the stacking mode of the material's layered structure. By limiting the ratio of I(101) / I(001) to 0.7 to 1.2, it is shown that the cathode material precursor has a good layered structure, which is conducive to the rapid diffusion of lithium ions between layers and improves the rate performance of the battery; by controlling the ratio within the range of 0.7 to 1.2, the structural stability of the material during the charge and discharge process and the uniform insertion / extraction of lithium ions are ensured, which helps to improve the electrochemical performance, including improving the capacity retention rate, coulombic efficiency and cycle performance of the first charge and discharge; in addition, the limitation of the ratio helps to enhance the consistency of the material structure, reduce the heterogeneity of crystal plane orientation and crystal defects, and help maintain the consistency of battery performance in mass production. In addition, the cathode material precursor with the above-mentioned crystal structure characteristics can reduce agglomeration and structural damage during the subsequent lithium mixing and sintering process, thereby improving the preparation efficiency and quality of the cathode material.

[0099] In some embodiments, the particle size distribution width SPAN of the positive electrode material precursor is 0.25 to 0.85, for example, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.8, 0.85 or a range consisting of any two thereof.

[0100] Specifically, the SPAN value is an indicator to measure the range of particle size distribution. The smaller the SPAN value, the narrower the particle size distribution and the better the consistency. The particle size distribution width of the positive electrode material precursor actually refers to the particle size distribution width of all secondary particles in the positive electrode material precursor. The particle size distribution width of the positive electrode material precursor is calculated according to the formula (D90-D10) / D50, where D10 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 10%, D50 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 50%, and D90 is the particle size corresponding to when the volume cumulative distribution percentage of the sample reaches 90%.

[0101] The present application does not limit the test method of D10, D50, and D90 of the positive electrode material precursor. For example, a laser particle size analyzer can be used for measurement.

[0102] This application limits the SPAN value to 0.25 to 0.85, which means that the particle size distribution of the positive electrode material precursor is relatively concentrated, which is conducive to ensuring the uniformity of the material. In the preparation process of the positive electrode material, the positive electrode material precursor with a narrow particle size distribution has better uniformity during the lithium mixing process and is less likely to agglomerate during sintering, which helps to improve the preparation quality and stability of the positive electrode material. In addition, the prepared positive electrode material has a uniform and narrow distribution range, which helps to uniformly diffuse and transmit lithium ions in the positive electrode material, reduce the resistance to lithium ion transmission, and improve the charge and discharge efficiency and rate performance of the battery. At the same time, the optimization of the particle size distribution can reduce the electrochemical instability inside the electrode and extend the cycle life of the battery.

[0103] In some embodiments, the cathode material precursor includes secondary particles formed by stacking primary particles. Specifically, the cathode material precursor is composed of multiple secondary particles. It is understood that the interior of the secondary particles forms a crystal core region, and the primary particles are stacked around the crystal core region to form a first intermediate layer, a second intermediate layer, a third intermediate layer, and an outer region. This structure is beneficial for improving the compaction density and electrochemical performance of the cathode material precursor.

[0104] The morphology of the primary particles directly influences the structure of the secondary particles and the final battery performance. In some embodiments, the primary particles in the core region, first intermediate layer, and second intermediate layer have a flake, rod, or block morphology; the primary particles in the third intermediate layer and outer layer have a spindle morphology. By precisely controlling the morphology of the primary particles in different layers, a gradient distribution of porosity can be achieved within the cathode material precursor along the particle's radial direction, with the porosity gradually increasing from the core region outward. This distribution helps improve the mechanical stability and cycling performance of the electrode material while maintaining high capacity.

[0105] When the primary particles are flaky in morphology, the average thickness of a single primary particle layer is 5 to 200 nm, the average length of a single primary particle layer is 200 to 450 nm, and the number of primary particle layers is ≥ 3. This stacking of flaky primary particles helps form a stable secondary particle structure and improves the transmission efficiency of lithium ions.

[0106] The spindle-shaped primary particles have a high aspect ratio, and this structure helps to increase the porosity. In some embodiments, when the primary particles are spindle-shaped, the average length of the primary particles is 220 to 600 nm, and the average width is 50 to 80 nm.

[0107] When the primary particles are rod-shaped, the aspect ratio of the primary particles is 20 to 200, such as 20, 50, 100, 150, 200, or any two thereof. This morphology can provide a straight lithium ion transport path, reduce lithium ion transport resistance in the positive electrode material, and help improve the battery's rate performance.

[0108] In some embodiments, the chemical formula of the cathode material precursor includes Ni x Co y M z T k (OH) 2-k , M is selected from at least one of Mn, Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, and Al, and T is selected from at least one of F, P, B, and O; wherein 0 <x≤1,0≤y<1,0≤z<1,0≤k<1。

[0109] Specifically, Ni (nickel), Co (cobalt), M (selected from at least one of Mn, Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, and Al), and T (selected from at least one of F, P, B, and O) are the main and auxiliary metal components in the cathode material precursor, respectively. They participate in the insertion and extraction of lithium ions during the battery's charge and discharge processes, affecting the battery's capacity, stability, and safety. Where x, y, z, and k are the mole fractions of these metal elements in the chemical formula, corresponding to the contents of Ni, Co, M, and T, respectively.

[0110] By adjusting the ratios of Ni, Co, M, and T, the material's performance can be optimized for different application requirements (such as high energy density, long cycle life, and high safety). For example, for applications pursuing high energy density, x (Ni content) can be increased, while to improve the thermal stability and safety of the material, the content of elements such as Co and Mn can be appropriately increased, and elements such as F and P can be introduced to form a stable coating layer.

[0111] By adjusting the molar fraction of each element, the electrochemical performance, thermal stability and structural stability of the material can be optimized, thereby meeting the requirements of different types of lithium-ion batteries for high energy density, long cycle life and high safety. In some preferred embodiments, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, 0≤k≤0.5. By further refining the content ratio of Ni, Co, M, and T, it is shown that the content of Ni in the positive electrode material precursor is high, while the content of Co, M, and T is relatively low. A high nickel content can significantly increase the energy density of the battery. At the same time, adding a small amount of Co, M, and T elements can improve the thermal stability, electrochemical performance, and structural stability of the material, thereby improving the overall performance of the battery.

[0112] In a second aspect of the present application, a method for preparing a positive electrode material precursor is provided, comprising the following steps:

[0113] S1, adding a metal salt solution, a precipitant, and a complexing agent to a first reaction base solution to form a first reaction system; and allowing the first reaction system to undergo a first growth to obtain a seed crystal;

[0114] S2, adding a metal salt solution, a precipitant, and a complexing agent to a second reaction base solution containing seed crystals to form a second reaction system; and causing the second reaction system to undergo a second growth to obtain a cathode material precursor;

[0115] In the second growth process, the feeding rate of the metal salt solution is gradually increased, and the feeding rates of the precipitant and the complexing agent are first gradually increased and then gradually decreased.

[0116] In step S1, a metal salt solution, a precipitant and a complexing agent are added to the first reaction base liquid to form a first reaction system. The purpose of this stage is to form seed crystals. In step S2, the seed crystals are moved to a reaction system containing a second reaction base liquid to form a second reaction system. At this stage, the feeding rate of the metal salt solution is gradually increased, which means that the flow rate of the metal salt solution gradually increases with the passage of time. This control method helps to promote the uniform growth of the precursor material, avoid agglomeration, and improve the radiality of the primary particles, thereby obtaining a secondary particle structure with a radial porosity gradient distribution. At the same time, the feeding rates of the precipitant and the complexing agent are first gradually increased and then gradually decreased. This rate change pattern helps to achieve dynamic control of the pH value and ammonia concentration in the reaction system, ensuring that the seed crystals gradually grow from the inner layer to the outer layer in the second reaction system to form an ideal pore structure and metal element distribution.

[0117] This two-stage growth reaction allows precise control of the structure of the cathode material precursor, including the radial distribution of porosity within the secondary particles. This unique structure helps improve the electrochemical performance of lithium-ion batteries, including capacity, rate capability, and cycling stability.

[0118] In some embodiments, during the 0-2h of the second growth, the feeding rate of the metal salt solution is D1; ​​during the 2h-10h of the second growth, the feeding rate of the metal salt solution increases uniformly at an increase rate of 1L / h-5L / h to D2; after 10h of the second growth, the feeding rate of the metal salt solution is D2, wherein D2>D1.

[0119] Specifically, within the initial 0-2h time range of the second growth, the feeding rate of the metal salt solution is set to D1. The main purpose of this stage is to provide a relatively stable growth environment for the seed crystal, ensuring that the seed crystal is initially expanded and structurally optimized in the second base liquid. Then, within the 2h-10h time period of the second growth, the feeding rate of the metal salt solution is increased at a fixed growth rate of 1L / h-5L / h to a uniform rate of D2. This gradually increasing feeding rate can promote the uniform growth of the seed crystal, avoid uneven agglomeration or structural defects during the growth process, and is conducive to the formation of a secondary particle structure with a radial porosity gradient distribution. The gradual increase in rate helps to control the dissolution and precipitation balance of the metal salt, ensuring that the primary particles of the material grow according to the predetermined morphology. After 10h of the second growth, the feeding rate of the metal salt solution is maintained at D2 until the growth process is completed. D2 is set at a higher rate than D1, which means that in the later stages of growth, the supply of metal salts increases, which helps to accelerate the nucleation and growth of particles and form larger secondary particles while maintaining the radial arrangement and porosity gradient distribution of primary particles.

[0120] In some preferred embodiments, D1 and D2 are each independently 10 L / h to 60 L / h. Under these preferred conditions, the metal salt solution feed rate ensures efficient and uniform material growth while controlling the stability of the reaction system. A lower D1 rate facilitates robust growth of the seed crystal in the early stages, while a higher D2 rate ensures rapid formation of a secondary particle structure with a high radial porosity distribution in the later stages of growth, thereby obtaining a cathode material precursor with excellent electrochemical performance.

[0121] In some embodiments, during the 0-2h of the second growth, the feeding rate of the complexing agent is E1; during the 2h-10h of the second growth, the feeding rate of the complexing agent is uniformly increased to E2 at an increasing rate of 0.1L / h-1L / h; during the 10h-16h of the second growth, the feeding rate of the complexing agent is E2; during the 16h-18h of the second growth, the feeding rate of the complexing agent is uniformly decreased to E3 at a decreasing rate of 0.1L / h-1L / h; after 18h of the second growth, the feeding rate of the complexing agent is E3; wherein, E2>E3>E1.

[0122] Specifically, during the initial 0-2 hours of the secondary growth phase, the complexing agent feed rate was set at E1. During this phase, the complexing agent promotes the complexation of metal ions, controls the precipitation rate and morphology, and provides stable conditions for the initial growth of the seed crystals. From 2 to 10 hours of the secondary growth phase, the complexing agent feed rate was increased uniformly at a rate of 0.1 to 1 L / h to E2. This increased rate further optimized the metal ion precipitation process, promoted the formation of the desired primary particle shape, and facilitated porosity control to achieve a radially gradient pore structure. From 10 to 16 hours of the secondary growth phase, the complexing agent feed rate was maintained at E2, the highest rate throughout the entire growth process, to ensure sufficient seed crystal expansion and structural optimization, resulting in a secondary particle structure with a high porosity distribution. From 16 to 18 hours of the secondary growth phase, the complexing agent feed rate was uniformly decreased at a rate of 0.1 to 1 L / h to E3. This slowdown helps regulate material growth, avoiding excessive complexation and precipitation, and maintaining structural stability and a consistent porosity gradient. After 18 hours of secondary growth, the complexing agent feed rate is maintained at E3 until the end of the secondary growth process. This rate, lower than E2 but higher than E1, helps maintain growth rate and structural control in the later stages of growth, avoiding unnecessary aggregation or structural defects.

[0123] In some preferred embodiments, E1, E2, and E3 are each independently set within a range of 0.4 L / h to 10 L / h. By limiting E1, E2, and E3 to be independently set within the range of 0.4 L / h to 10 L / h, the complexing agent feed rate under these preferred conditions ensures efficient and uniform material growth while controlling the stability of the reaction system, ultimately obtaining a cathode material precursor with a stable structure, ideal porosity distribution, and excellent performance.

[0124] In some embodiments, during the 0-2h of the second growth, the feeding flow rate of the precipitant is H1, and during the 2h-10h of the second growth, the feeding flow rate of the precipitant increases uniformly at an increasing rate of 0.2L / h-2L / h to H2; during the 10h-16h of the second growth, the feeding flow rate of the precipitant is H2; during the 16h-18h of the second growth, the feeding flow rate of the precipitant decreases uniformly at a decreasing rate of 0.2L / h-2L / h to H3; after 18h of the second growth, the feeding flow rate of the precipitant is H3; wherein, H2>H3>H1.

[0125] Specifically, during the initial 0-2 hours of the secondary growth, the precipitant feed rate was set to H1. During this stage, the slow addition of precipitant facilitates initial stabilization and growth of the seed crystals, laying the foundation for subsequent structural optimization. From 2 to 10 hours of the secondary growth, the precipitant feed rate was increased uniformly to H2 at a rate of 0.2 to 2 L / h. This acceleration process helps accelerate the precipitation of metal ions and promotes the formation of the material structure. In particular, adjusting the flow rate can influence the formation rate and structure of hydroxides, and thus the porosity and distribution of the final material. From 10 to 16 hours of the secondary growth, the precipitant feed rate was maintained at H2. This is the highest precipitant flow rate during the entire growth process, contributing to uniform material growth and structural optimization, ensuring the desired radial gradient of porosity within the secondary particles. From 16 to 18 hours of the secondary growth, the precipitant feed rate was decreased uniformly to H3 at a rate of 0.2 to 2 L / h. Controlling the flow rate during this phase helps ensure a smooth transition in material growth, avoiding structural defects caused by excessive flow rates and maintaining material stability and porosity gradient distribution. After 18 hours of secondary growth, the precipitant feed rate is maintained at H3 until the end of the growth process. This flow rate is lower than H2 but higher than H1, ensuring structural control in the later stages of growth, avoiding unnecessary agglomeration or structural changes, and maintaining consistent material properties.

[0126] In some preferred embodiments, H1, H2, and H3 are each independently 5 L / h to 20 L / h. By setting the flow rates of H1, H2, and H3 within the range of 5 L / h to 20 L / h, the precipitant feed flow rate under these preferred conditions not only ensures the stability of the reaction system and the controllability of material growth, but also facilitates an efficient and uniform material growth process, ultimately obtaining a positive electrode material precursor with a stable structure, ideal porosity distribution, and excellent performance. Preferably, H1, H2, and H3 are each independently 5 L / h to 15 L / h.

[0127] In some embodiments, during 0 to 15 hours of the second growth, the pH value of the second reaction system is F1 at 45°C; during 15 to 18 hours of the second growth, the pH value of the second reaction system decreases uniformly at a rate of 0.002 / h to 0.3 / h at 45°C to F2; after 18 hours of the second growth, the pH value of the second reaction system is F2 at 45°C; wherein, F1>F2.

[0128] Specifically, during the initial 0 to 15 hours of the second growth, the pH value of the second reaction system (at 45°C) is set to F1. The stable maintenance of this pH value is crucial for controlling the morphology and structure of the early growth of the seed crystal, helping to ensure a good foundation for the formation of the seed crystal and providing conditions for the subsequent formation of a porosity gradient distribution. During the 15-18 hours of the second growth, the pH value of the second reaction system (at 45°C) is uniformly reduced to F2 at a rate of 0.002 / h to 0.3 / h. The gradual reduction in pH can regulate the precipitation process, affect the deposition rate of metal ions, and promote the gradient distribution of the material's porosity. At this stage, precise control of pH helps control the formation of pores, especially in the outer layer of the secondary particles, to form a structure with higher porosity, which is conducive to the rapid penetration and diffusion of the electrolyte. After 18 hours of the second growth, the pH value of the second reaction system (at 45°C) is maintained at F2 until the entire second growth process is completed. Stabilizing the pH value at F2 helps ensure the controllability of material growth and avoids rapid precipitation due to too low a pH value, which in turn affects the structural properties and pore distribution of the material.

[0129] In some preferred embodiments, F1 and F2 are each independently between 10.35 and 10.60 at 45°C. This pH range is ideal for preparing cathode material precursors by coprecipitation. Controlling pH directly influences the precipitation rate of metal ions, and thus the formation of the material structure. Within this preferred pH range, radial arrangement of primary particles and a radially gradient porosity distribution can be effectively achieved, ultimately yielding a precursor material with superior performance.

[0130] In some embodiments, during the 0-2 h of the second growth, the ammonia concentration of the second reaction system is G1; during the 2-10 h of the second growth, the ammonia concentration of the second reaction system increases uniformly at a rate of 0.05 g / L·h to 0.3 g / L·h to G2; during the 10-16 h of the second growth, the ammonia concentration of the second reaction system is G2; during the 16-18 h of the second growth, the ammonia concentration of the second reaction system decreases uniformly at a rate of 0.05 g / L·h to 0.3 g / L·h to G3; after 18 h of the second growth, the ammonia solubility of the second reaction system is G3; wherein, G2>G3>G1.

[0131] Specifically, during the 0-2h period of the second growth, the ammonia concentration in the second reaction system is set to G1. This initial ammonia concentration is crucial for controlling the early growth and morphology of the seed crystal, helps to form a stable reaction environment, and lays the foundation for the formation of a porosity gradient distribution. During the 2h-10h period of the second growth, the ammonia concentration is uniformly increased to G2 at a rate of 0.05g / L·h to 0.3g / L·h. The gradual increase in ammonia concentration can regulate the precipitation process, affect the complexation between metal ions and ammonia, and thus affect the distribution of the material's porosity. At this stage, precise control of the ammonia concentration helps control the formation of pores, especially in the middle layer region of the secondary particles, forming a structure with suitable porosity, which is conducive to the diffusion of lithium ions. During the 10h-16h period of the second growth, the ammonia concentration is maintained at G2. The ammonia concentration at this stage is the highest value in the entire growth process, which helps to ensure that the internal porosity of the material reaches the expected high value and optimizes the diffusion path of lithium ions. During the 16th to 18th hour of the second growth phase, the ammonia concentration was steadily decreased to G3 at a rate of 0.05 to 0.3 g / L·h. This gradual decrease in ammonia concentration helped control the porosity of the secondary particle outer layer, forming a structure with strip-like pores with a high aspect ratio, which facilitated rapid electrolyte penetration and diffusion. After the 18th hour of the second growth phase, the ammonia concentration was maintained at G3 until the end of the second growth phase.

[0132] In some preferred embodiments, G1, G2, and G3 are 2.2 g / L to 4.6 g / L. Ammonia concentrations within this range can effectively achieve radial arrangement of primary particles and radial gradient distribution of porosity in the material, promote optimization of the internal structure of the material, and improve the diffusion efficiency of lithium ions and the electrochemical performance of the material. By precisely controlling the change in ammonia concentration, a radial gradient distribution of porosity inside the positive electrode material precursor can be achieved during the second growth, optimizing the diffusion path of lithium ions, improving the compaction density and electrochemical reaction efficiency of the material, and ultimately achieving high capacity, high rate performance, and long cycle stability of the battery.

[0133] In some embodiments, during the second growth process, the stirring speed of the second reaction system is gradually reduced.

[0134] Specifically, the stirring speed is reduced at a certain rate for 2 hours every 3 hours, and the reduction rate is 8 to 10 rpm / h. For example, in the initial 0 to 3 hours of the second growth, the stirring speed is set to M rpm. This initial speed helps to form a uniform solution environment in the reaction system, ensuring that the seed crystals are initially expanded and grown in the bottom liquid. After 3 hours of the second growth, the stirring speed is reduced at a certain rate. For example, after reducing it at a rate of 10 rpm / h for 2 hours, the stirring speed is (M-20) rpm, that is, the stirring speed is (M-20) rpm for 5 to 8 hours of the second growth, and so on. M is preferably 240 to 500. This stirring speed range can ensure sufficient mixing of the reaction system, and through the strategy of gradual reduction, the growth process of the material can be accurately controlled, thereby improving the performance of the positive electrode material precursor.

[0135] By gradually reducing the stirring speed, the present application can achieve fine control of the material growth environment during the second growth process, which helps to uniformly grow the material, optimize the porosity distribution, and ultimately improve the battery capacity, rate performance and cycle stability.

[0136] This application does not limit the specific type of raw materials, which can be conventional reaction raw materials in the art. For example, in some embodiments, the metal salt solution contains nickel salts and cobalt salts, the soluble salts include at least one of nitrates, chlorides, and sulfates, and the concentration of the metal salt in the metal salt solution is 120g / L to 145g / L; preferably, the metal salt also includes at least one of a salt formed by element M and a salt formed by element T. The complexing agent includes an ammonia solution, and the concentration of NH3 in the ammonia solution is 7% to 10%. The precipitant includes a sodium hydroxide solution, and the concentration of the sodium hydroxide solution is 200g / L to 450g / L. The solid content of the first reaction system and the second reaction system is independently 400g / L to 800g / L.

[0137] The properties of the seed crystal (such as morphology and structure) will directly affect the performance of the subsequent reaction products. By controlling the composition of the first reaction base liquid, reaction conditions (such as pH value, temperature, stirring speed) and feeding rate, the generation of seed crystals can be precisely controlled. For example, in some embodiments, the ammonia concentration of the first reaction base liquid is 3.0g / L~4.5g / L, and the pH value of the first reaction base liquid is 10.55~11.95 at 45°C. The ammonia concentration of the second reaction base liquid is 1.0~4.0g / L, and the pH value of the second reaction base liquid is 10.40~11.80 at 45°C. The reaction temperature of the first growth and the second growth is 50°C~90°C. Both the first growth and the second growth are carried out under stirring, and the stirring speed is 50rpm~500rpm. Both the first growth and the second growth are carried out under a fixed atmosphere, wherein the atmosphere can be selected from a protective gas and / or an oxygen-containing gas, the protective gas is selected from one or more of nitrogen, helium, neon, argon, krypton, xenon, and radon, and the oxygen-containing gas is selected from a mixed gas of a protective gas and oxygen or air, or one or more of air, and the volume ratio of oxygen in the atmosphere is ≤5%.

[0138] The third aspect of the present application provides a positive electrode material, which is prepared by calcining a positive electrode material precursor and a lithium source, wherein the positive electrode material precursor includes the positive electrode material precursor provided by the first aspect or the positive electrode material precursor prepared by the preparation method provided by the second aspect.

[0139] Specifically, the above-mentioned positive electrode material precursor can be directly subjected to a lithiation sintering treatment to obtain a positive electrode material. Since the above-mentioned positive electrode material precursor with excellent performance is used for sintering, a positive electrode material with high capacity and excellent cycle stability can be obtained.

[0140] The fourth aspect of the present application provides a battery comprising the positive electrode material provided in the third aspect.

[0141] Due to the inclusion of the above-mentioned positive electrode material with excellent performance, the battery assembled from the positive electrode material has higher capacity and excellent cycle stability.

[0142] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0143] Example 1

[0144] The preparation method of the positive electrode material precursor of this embodiment includes the following steps:

[0145] 1. Raw material preparation

[0146] Nickel sulfate, cobalt sulfate, manganese sulfate and pure water are mixed in a nickel:cobalt:manganese molar ratio of 97:1:2 to obtain a metal salt solution with a total metal ion concentration of 134 g / L; the precipitant is a sodium hydroxide solution with a concentration of 320 g / L, and the complexing agent is an ammonia solution with a mass fraction of NH3 of 9%.

[0147] 2. Formation of seed crystals

[0148] S21, forming the first reaction bottom liquid: in the first reaction kettle with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 220 L of pure water was added as the bottom liquid. Ammonia solution was further added to adjust the ammonia value to 2.4 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 11.88. The stirring was turned on to 430 rpm and the reaction temperature was maintained at 67°C to form the first reaction bottom liquid in the first reactor.

[0149] S22, nucleation reaction process: metal salt solution, sodium hydroxide solution, ammonia solution and the first reaction base solution are introduced into the first reaction kettle and mixed to carry out nucleation reaction for 1 hour; during the nucleation reaction, the flow rate of the metal salt solution is 6 L / h;

[0150] S23. First growth reaction process: After the nucleation reaction is completed, the pH value is uniformly reduced to 10.80 (at 45°C) within 30 minutes, the flow rate of the metal salt solution is increased to 22 L / h after 4 hours, and the stirring speed is maintained at 430 rpm. When the D50 particle size of the material in the first reactor is detected to reach 3.8 μm, the feeding is stopped, the slurry is washed and dried, and a seed crystal is obtained.

[0151] 3. Preparation of cathode material precursor

[0152] S31, prepare the second reaction base liquid: in the second reactor with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 320 L of pure water was added as the bottom liquid. An appropriate amount of ammonia solution was added to adjust the ammonia value of the bottom liquid to 3.0 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 10.65. The stirring was started to 430 rpm and the reaction temperature was maintained at 70°C to obtain the second reaction bottom liquid.

[0153] S32, second growth: adding the metal salt solution, sodium hydroxide solution and ammonia solution into the second reaction kettle and mixing with the second reaction base liquid to perform the second growth;

[0154] Among them, the feeding rate of the metal salt solution is 13 L / h from 0 to 2 hours of the second growth; the feeding rate of the metal salt solution increases at a constant rate of 1.8 L / h from 2 hours to 10 hours of the second growth; after 10 hours of the second growth, the feeding rate of the metal salt solution is 27.4 L / h;

[0155] During the second growth period of 0 to 2 hours, the feeding rate of the ammonia solution was 3 L / h; during the second growth period of 2 hours to 10 hours, the feeding rate of the ammonia solution was increased at a constant rate of 0.36 L / h to 5.88 L / h; during the second growth period of 10 hours to 16 hours, the feeding rate of the ammonia solution was 5.88 L / h; during the second growth period of 16 hours to 18 hours, the feeding rate of the ammonia solution was decreased at a constant rate of 0.4 L / h; after the second growth period of 18 hours, the feeding rate of the ammonia solution was 5.08 L / h;

[0156] During the second growth period of 0 to 2 hours, the feeding flow rate of the sodium hydroxide solution was 7.5 L / h; during the second growth period of 2 hours to 10 hours, the feeding flow rate of the sodium hydroxide solution increased uniformly at an increasing rate of 0.92 L / h to 14.86 L / h; after the second growth period of 10 hours to 16 hours, the feeding flow rate of the sodium hydroxide solution was 14.86 L / h; during the second growth period of 16 hours to 18 hours, the feeding flow rate of the sodium hydroxide solution decreased uniformly at a decreasing rate of 0.48 L / h; after the second growth period of 18 hours, the feeding flow rate of the sodium hydroxide solution was 13.9 L / h;

[0157] During the second growth period of 0-3h, the stirring speed was 330rpm, which was uniformly reduced at a rate of 10rpm / h for 2h. During the second growth period of 5-8h, the stirring speed was 310rpm, which was further uniformly reduced at a rate of 10rpm / h for 2h. The stirring speed during 10-13h was 290rpm, which was further uniformly reduced at a rate of 10rpm / h for 2h. The stirring speed during 15-18h was 270rpm, which was then uniformly reduced at a rate of 8rpm / h for 2h. The stirring speed during 20-23h was 254rpm, which was further uniformly reduced at a rate of 8rpm / h for 2h. The stirring speed during 25-28h was 238rpm, which was finally uniformly reduced at a rate of 8rpm / h for 2h. After 30h, the stirring speed was 222rpm.

[0158] During the second growth period of 0-2 hours, the ammonia concentration was 3.0 g / L; during the second growth period of 2-10 hours, the ammonia concentration increased at a constant rate of 0.1 g / L·h; during the second growth period of 10-16 hours, the ammonia concentration was 3.8 g / L; during the second growth period of 16-18 hours, the ammonia concentration decreased at a constant rate of 0.3 g / L·h to 3.2 g / L; after the second growth period of 18 hours, the ammonia solubility was 3.2 g / L.

[0159] During the second growth period of 0 to 15 hours, the pH value of the second reaction system (at 45°C) was 10.60; during the second growth period of 15 to 18 hours, the pH value of the second reaction system (at 45°C) decreased uniformly at a rate of 0.05 / h to 10.45; after 18 hours of the second growth period, the pH value of the second reaction system (at 45°C) was 10.45;

[0160] During the second growth reaction synthesis process, the atmosphere and temperature remain unchanged, and the precursor slurry is synthesized by continuous reaction. When the D50 particle size of the slurry in the second growth process is detected to reach 12 μm, the feeding is stopped to obtain the second reaction slurry;

[0161] S33, post-processing: adding the second reaction slurry to a filter press washing device for washing and filter pressing, washing with sodium hydroxide solution and pure water in turn, and then sending it to a drying process, and then screening through a 325-mesh filter and demagnetizing in turn to obtain the positive electrode precursor material of this embodiment.

[0162] Example 2

[0163] The preparation method of the positive electrode material precursor of this embodiment includes the following steps:

[0164] 1. Raw material preparation

[0165] Nickel sulfate, cobalt sulfate, manganese sulfate and pure water are mixed in a nickel:cobalt:manganese molar ratio of 94:4:2 to obtain a metal salt solution with a total metal ion concentration of 134 g / L; the precipitant is a sodium hydroxide solution with a concentration of 320 g / L, and the complexing agent is an ammonia solution with a mass fraction of NH3 of 9%.

[0166] 2. Formation of seed crystals

[0167] S21, forming the first reaction bottom liquid: in the first reaction kettle with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced with nitrogen, and 220 L of pure water was added as a bottom liquid. Ammonia solution was further added to adjust the ammonia value to 2.4 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 11.82. The stirring was turned on to 400 rpm and the reaction temperature was maintained at 65°C to form a first reaction bottom liquid in the first reactor.

[0168] S22, nucleation reaction process: metal salt solution, sodium hydroxide solution, ammonia solution and the first reaction base solution are introduced into the first reaction kettle and mixed to carry out nucleation reaction for 1 hour; during the nucleation reaction, the flow rate of the metal salt solution is 6 L / h;

[0169] S23. First growth reaction process: After the nucleation reaction is completed, the pH value is uniformly reduced to 10.75 (at 45°C) within 30 minutes, the flow rate of the metal salt solution is increased to 22 L / h after 4 hours, and the stirring speed is maintained at 400 rpm. When the average particle size D50 of the material in the first reactor is detected to reach 3.8 μm, the feeding is stopped, the slurry is washed and dried, and a seed crystal is obtained.

[0170] 3. Preparation of cathode material precursor

[0171] S31, prepare the second reaction base liquid: in the second reactor with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 320 L of pure water was added as the bottom liquid. An appropriate amount of ammonia solution was added to adjust the ammonia value of the bottom liquid to 3.0 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 10.60. The stirring was started to 400 rpm and the reaction temperature was maintained at 70°C to obtain the second reaction bottom liquid.

[0172] S32, second growth: adding the metal salt solution, sodium hydroxide solution and ammonia solution into the second reaction kettle and mixing with the second reaction base liquid to perform the second growth;

[0173] Among them, the feeding rate of the metal salt solution is 13 L / h from 0 to 2 hours of the second growth; the feeding rate of the metal salt solution increases at a constant rate of 1.8 L / h from 2 hours to 10 hours of the second growth; after 10 hours of the second growth, the feeding rate of the metal salt solution is 27.4 L / h;

[0174] During the second growth period of 0 to 2 hours, the feeding rate of the ammonia solution was 3 L / h; during the second growth period of 2 hours to 10 hours, the feeding rate of the ammonia solution was increased at a constant rate of 0.36 L / h to 5.88 L / h; during the second growth period of 10 hours to 16 hours, the feeding rate of the ammonia solution was 5.88 L / h; during the second growth period of 16 hours to 18 hours, the feeding rate of the ammonia solution was decreased at a constant rate of 0.45 L / h; after the second growth period of 18 hours, the feeding rate of the ammonia solution was 4.98 L / h;

[0175] During the second growth period of 0 to 2 hours, the feeding flow rate of the sodium hydroxide solution was 7.5 L / h; during the second growth period of 2 hours to 10 hours, the feeding flow rate of the sodium hydroxide solution increased uniformly at an increasing rate of 0.92 L / h to 14.86 L / h; after the second growth period of 10 hours to 16 hours, the feeding flow rate of the sodium hydroxide solution was 14.86 L / h; during the second growth period of 16 hours to 18 hours, the feeding flow rate of the sodium hydroxide solution decreased uniformly at a decreasing rate of 0.52 L / h; after the second growth period of 18 hours, the feeding flow rate of the sodium hydroxide solution was 13.82 L / h;

[0176] During the second growth period of 0-3h, the stirring speed was 300rpm, which was uniformly reduced at a rate of 10rpm / h for 2h. During the second growth period of 5-8h, the stirring speed was 280rpm, which was further uniformly reduced at a rate of 10rpm / h for 2h. The stirring speed during 10-13h was 260rpm, which was further uniformly reduced at a rate of 10rpm / h for 2h. The stirring speed during 15-18h was 240rpm, which was then uniformly reduced at a rate of 8rpm / h for 2h. The stirring speed during 20-23h was 224rpm, which was further uniformly reduced at a rate of 8rpm / h for 2h. The stirring speed during 25-28h was 208rpm, which was finally uniformly reduced at a rate of 8rpm / h for 2h. After 30h, the stirring speed was 192rpm.

[0177] During the second growth period of 0-2 hours, the ammonia concentration was 3.0 g / L; during the second growth period of 2-10 hours, the ammonia concentration increased at a constant rate of 0.1 g / L·h; during the second growth period of 10-16 hours, the ammonia concentration was 3.8 g / L; during the second growth period of 16-18 hours, the ammonia concentration decreased at a constant rate of 0.3 g / L·h to 3.2 g / L; after the second growth period of 18 hours, the ammonia solubility was 3.2 g / L.

[0178] During the second growth period of 0 to 15 hours, the pH value of the second reaction system (at 45°C) was 10.60; during the second growth period of 15 to 18 hours, the pH value of the second reaction system (at 45°C) decreased uniformly at a rate of 0.05 / h to 10.45; after 18 hours of the second growth period, the pH value of the second reaction system (at 45°C) was 10.45;

[0179] During the second growth reaction synthesis process, the atmosphere and temperature remain unchanged, and the precursor slurry is synthesized by continuous reaction. When the D50 particle size of the slurry in the second growth process is detected to reach 16 μm, the feeding is stopped to obtain the second reaction slurry;

[0180] S33, post-processing: adding the second reaction slurry to a filter press washing device for washing and filter pressing, washing with sodium hydroxide solution and pure water in turn, and then sending it to a drying process, and then screening through a 325-mesh filter and demagnetizing in turn to obtain the positive electrode precursor material of this embodiment.

[0181] Example 3

[0182] The difference from Example 1 is that nickel sulfate, cobalt sulfate, manganese sulfate, zinc sulfate and pure water are mixed in a molar ratio of nickel, cobalt, manganese and zinc of 94:4:1:1 to obtain a metal salt solution with a total metal ion concentration of 134 g / L.

[0183] Example 4

[0184] The difference from Example 1 is that 250 g of analytically pure sodium tetraborate crystals are added to every 80 L of 320 g / L sodium hydroxide solution and used as a precipitant, so that the boron doping amount in the final positive electrode precursor material is 300 ppm.

[0185] Example 5

[0186] The difference from Example 1 is that during the second growth period of 0 to 2 hours, the feeding rate of the metal salt solution is 13 L / h; during the second growth period of 2 hours to 10 hours, the feeding rate of the metal salt solution is increased at a constant rate of 1.8 L / h; after 10 hours of the second growth, the feeding rate of the metal salt solution is 27.4 L / h;

[0187] During the second growth period of 0 to 2 hours, the feeding rate of the ammonia solution was 0.4 L / h; during the second growth period of 2 hours to 10 hours, the feeding rate of the ammonia solution was increased uniformly at a flow rate of 1 L / h to 8.4 L / h; during the second growth period of 10 hours to 16 hours, the feeding rate of the ammonia solution was 8.4 L / h; during the second growth period of 16 hours to 18 hours, the feeding rate of the ammonia solution was decreased uniformly at a flow rate of 1 L / h to 6.4 L / h; after the second growth period of 18 hours, the feeding rate of the ammonia solution was 6.4 L / h;

[0188] During the second growth period of 0 to 2 hours, the feeding flow rate of the sodium hydroxide solution is 5 L / h; during the second growth period of 2 hours to 10 hours, the feeding flow rate of the sodium hydroxide solution is increased at a uniform rate of 1.5 L / h to 17 L / h; after the second growth period of 10 hours to 16 hours, the feeding flow rate of the sodium hydroxide solution is 17 L / h; during the second growth period of 16 hours to 18 hours, the feeding flow rate of the sodium hydroxide solution is decreased at a uniform rate of 2 L / h; after the second growth period of 18 hours, the feeding flow rate of the sodium hydroxide solution is 13 L / h;

[0189] During the 0-2h of the second growth, the ammonia concentration was 2.2g / L; during the 2h-10h of the second growth, the ammonia concentration increased uniformly at a rate of 0.2g / L·h; during the 10-16h of the second growth, the ammonia concentration was 3.8g / L; during the 16h-18h of the second growth, the ammonia concentration decreased uniformly at a rate of 0.3g / L·h to 3.2g / L; the ammonia solubility after 18h of the second growth was 3.2g / L.

[0190] Example 6

[0191] The difference from Example 1 is:

[0192] During the second growth period of 0 to 2 hours, the feeding rate of the ammonia solution was 3 L / h; during the second growth period of 2 to 10 hours, the feeding rate of the ammonia solution was increased at a constant rate of 0.36 L / h to 5.88 L / h; after the second growth period of 10 hours, the feeding rate of the ammonia solution was 5.88 L / h;

[0193] During the second growth period of 0 to 2 hours, the feeding flow rate of the sodium hydroxide solution was 7.5 L / h; during the second growth period of 2 hours to 10 hours, the feeding flow rate of the sodium hydroxide solution increased uniformly at an increase rate of 0.92 L / h to 14.86 L / h; after 10 hours of the second growth, the feeding flow rate of the sodium hydroxide solution was 14.86 L / h.

[0194] Example 7

[0195] The difference from Example 1 is:

[0196] During the second growth period of 0 to 2 hours, the feeding rate of the ammonia solution was 3 L / h; during the second growth period of 2 hours to 10 hours, the feeding rate of the ammonia solution was increased at a constant rate of 0.36 L / h to 5.88 L / h; during the second growth period of 10 hours to 16 hours, the feeding rate of the ammonia solution was 5.88 L / h; during the second growth period of 16 hours to 18 hours, the feeding rate of the ammonia solution was decreased at a constant rate of 1.44 L / h to 3 L / h; after the second growth period of 18 hours, the feeding rate of the ammonia solution was 3 L / h;

[0197] During the 0-2h period of the second growth, the feeding flow rate of the sodium hydroxide solution was 7.5 L / h; during the 2-10h period of the second growth, the feeding flow rate of the sodium hydroxide solution increased uniformly at an increasing rate of 0.92 L / h to 14.86 L / h; after 10h to 16h of the second growth, the feeding flow rate of the sodium hydroxide solution was 14.86 L / h; during the 16-18h period of the second growth, the feeding flow rate of the sodium hydroxide solution decreased uniformly at a decreasing rate of 3.36 L / h to 7.5 L / h; after 18h of the second growth, the feeding flow rate of the sodium hydroxide solution was 7.5 L / h.

[0198] Comparative Example 1

[0199] The preparation method of the positive electrode material precursor of this comparative example comprises the following steps:

[0200] 1. Raw material preparation

[0201] Nickel sulfate, cobalt sulfate, manganese sulfate and pure water are mixed in a nickel:cobalt:manganese molar ratio of 92:4:4 to obtain a metal salt solution with a total metal ion concentration of 134 g / L; the precipitant is a sodium hydroxide solution with a concentration of 320 g / L, and the complexing agent is an ammonia solution with a mass fraction of NH3 of 9%.

[0202] 2. Formation of seed crystals

[0203] S21, forming the first reaction bottom liquid: in the first reaction kettle with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 220 L of pure water was added as the bottom liquid. Ammonia solution was further added to adjust the ammonia value to 4.8 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 11.95. The stirring was started to 400 rpm and the reaction temperature was maintained at 68°C to form the first reaction bottom liquid in the first reactor.

[0204] S22, nucleation reaction process: metal salt solution, sodium hydroxide solution, ammonia solution and the first reaction base solution are introduced into the first reaction kettle and mixed to carry out nucleation reaction for 1 hour; during the nucleation reaction, the flow rate of the metal salt solution is 6 L / h;

[0205] S23. First growth reaction process: After the nucleation reaction is completed, the pH value is uniformly reduced to 10.80 (at 45°C) within 30 minutes, the flow rate of the metal salt solution is increased to 25 L / h after 4 hours, and the stirring speed is maintained at 400 rpm. When the D50 particle size of the material in the first reactor is detected to reach 3.6 μm, the feeding is stopped, the slurry is washed and dried, and a seed crystal is obtained.

[0206] 3. Preparation of cathode material precursor

[0207] S31, prepare the second reaction base liquid: in the second reactor with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 320 L of pure water was added as the bottom liquid. An appropriate amount of ammonia solution was added to adjust the ammonia value of the bottom liquid to 6.0 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 10.9. The stirring was started to 400 rpm and the reaction temperature was maintained at 68°C to obtain the second reaction bottom liquid.

[0208] S32, second growth: adding the metal salt solution, sodium hydroxide solution and ammonia solution into the second reaction kettle and mixing with the second reaction base liquid to perform the second growth;

[0209] Among them, during the second growth period of 0 to 2 hours, the feeding rate of the metal salt solution is 13 L / h; during the second growth period of 2 hours to 30 hours, the feeding rate of the metal salt solution is increased at a constant rate of 0.6 L / h; after 30 hours of the second growth, the feeding rate of the metal salt solution is 30 L / h;

[0210] The feeding rate of the ammonia solution during the second growth period of 0 to 2 hours was 6 L / h; during the second growth period of 2 to 30 hours, the feeding rate of the ammonia solution increased at a constant rate of 0.45 L / h; after 30 hours of the second growth, the feeding rate of the ammonia solution was 18.6 L / h;

[0211] During the second growth period of 0 to 2 hours, the feeding rate of the sodium hydroxide solution was 8.8 L / h; during the second growth period of 2 hours to 30 hours, the feeding rate of the sodium hydroxide solution increased at a constant rate of 0.35 L / h; after 31 hours of the second growth, the feeding rate of the sodium hydroxide solution was 18.6 L / h;

[0212] During the second growth period of 0 to 3 hours, the stirring speed was 360 rpm. After being uniformly reduced at a rate of 15 rpm / h for 3 hours, the stirring speed was 315 rpm during the second growth period of 6 to 10 hours. After being uniformly reduced at a rate of 15 rpm / h for 3 hours, the stirring speed was 270 rpm during 13 to 17 hours. After being uniformly reduced at a rate of 20 rpm / h for 2 hours, the stirring speed was 230 rpm during 19 to 24 hours. After being uniformly reduced at a rate of 20 rpm / h for 2 hours, the stirring speed was 190 rpm during 26 to 30 hours. After being uniformly reduced at a rate of 20 rpm / h for 2 hours, the stirring speed was 150 rpm after 32 hours.

[0213] During the 0-2 h of the second growth, the ammonia concentration was 6.5 g / L; after 2 h of the second growth, the ammonia concentration was 6.5 g / L;

[0214] During the second growth period of 0 to 2 hours, the pH value of the second reaction system (at 45°C) was 10.85; after 2 hours of the second growth period, the pH value of the second reaction system (at 45°C) was 10.8;

[0215] During the second growth reaction synthesis process, the atmosphere and temperature remain unchanged, and the precursor slurry is synthesized by continuous reaction. When the D50 particle size of the slurry in the second growth process is detected to reach 12 μm, the feeding is stopped to obtain the second reaction slurry;

[0216] S33, post-processing: adding the second reaction slurry to a filter press washing device for washing and filter pressing, washing with sodium hydroxide solution and pure water in turn, and then sending it to a drying process, and then screening through a 325-mesh filter and demagnetizing in turn to obtain the positive electrode precursor material of this embodiment.

[0217] Comparative Example 2

[0218] The preparation method of the positive electrode material precursor of this comparative example comprises the following steps:

[0219] 1. Raw material preparation

[0220] Nickel sulfate, cobalt sulfate, manganese sulfate and pure water are mixed in a nickel:cobalt:manganese molar ratio of 90:5:5 to obtain a metal salt solution with a total metal ion concentration of 134 g / L; the precipitant is a sodium hydroxide solution with a concentration of 320 g / L, and the complexing agent is an ammonia solution with a mass fraction of NH3 of 9%.

[0221] 2. Formation of seed crystals

[0222] S21, forming the first reaction bottom liquid: in the first reaction kettle with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 150 L of pure water was added as a bottom liquid. Ammonia solution was further added to adjust the ammonia value to 2.5 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 11.75. The stirring was turned on to 400 rpm and the reaction temperature was maintained at 65°C to form a first reaction bottom liquid in the first reactor.

[0223] S22, nucleation reaction process: metal salt solution, sodium hydroxide solution, ammonia solution and the first reaction base solution are introduced into the first reaction kettle and mixed to carry out nucleation reaction for 1 hour; during the nucleation reaction, the flow rate of the metal salt solution is 6 L / h;

[0224] S23. First growth reaction process: After the nucleation reaction is completed, the pH value is uniformly reduced to 10.65 (at 45°C) within 30 minutes, the flow rate of the metal salt solution is increased to 18 L / h after 4 hours, and the stirring speed is maintained at 400 rpm. When the D50 particle size of the material in the first reactor is detected to reach 3.7 μm, the feeding is stopped, the slurry is washed and dried, and a seed crystal is obtained.

[0225] 3. Preparation of cathode material precursor

[0226] S31, prepare the second reaction base liquid: in the second reactor with an effective volume of 500L, continuously introduce 8-12m 3 The air in the reactor was replaced by nitrogen, and 320 L of pure water was added as the bottom liquid. An appropriate amount of ammonia solution was added to adjust the ammonia value of the bottom liquid to 6.0 g / L. Sodium hydroxide solution was added to adjust the pH value of the bottom liquid (at 45°C) to 11.5. The stirring was started to 400 rpm and the reaction temperature was maintained at 65°C to obtain the second reaction bottom liquid.

[0227] S32, second growth: adding the metal salt solution, sodium hydroxide solution and ammonia solution into the second reaction kettle and mixing with the second reaction base liquid to perform the second growth;

[0228] Among them, the feeding rate of the metal salt solution is 8 L / h from 0 to 3 hours of the second growth; the feeding rate of the metal salt solution increases at a constant rate of 1.04 L / h from 3 to 30 hours of the second growth; after 30 hours of the second growth, the feeding rate of the metal salt solution is 36.08 L / h;

[0229] The feeding rate of the ammonia solution during the second growth period of 0-3 hours was 3.2 L / h; during the second growth period of 3-30 hours, the feeding rate of the ammonia solution increased at a constant rate of 0.18 L / h; after 30 hours of the second growth, the feeding rate of the ammonia solution was 8.06 L / h;

[0230] During the second growth period of 0 to 3 hours, the feeding rate of the sodium hydroxide solution was 4.2 L / h; during the second growth period of 3 to 30 hours, the feeding rate of the sodium hydroxide solution increased at a constant rate of 0.57 L / h; after 30 hours of the second growth, the feeding rate of the sodium hydroxide solution was 19.59 L / h;

[0231] During the second growth period of 0 to 3 hours, the stirring speed was 360 rpm, which was then uniformly decreased at a rate of 15 rpm / h for 3 hours. During the second growth period of 6 to 10 hours, the stirring speed was 315 rpm, which was further uniformly decreased at a rate of 15 rpm / h for 3 hours. The stirring speed during 13 to 17 hours was 270 rpm, which was further uniformly decreased at a rate of 20 rpm / h for 2 hours. The stirring speed during 19 to 24 hours was 230 rpm, which was then uniformly decreased at a rate of 20 rpm / h for 2 hours. The stirring speed during 26 to 30 hours was 190 rpm, which was further uniformly decreased at a rate of 20 rpm / h for 2 hours. The stirring speed during 32 hours was 150 rpm.

[0232] During the second growth period of 0 to 2 h, the ammonia concentration was 6.5 g / L; after 2 h of the second growth, the ammonia solubility was 6.5 g / L;

[0233] During the second growth period of 0 to 3 hours, the pH value of the second reaction system (at 45°C) was 10.65; after 3 hours of the second growth, the pH value of the second reaction system (at 45°C) was 10.70;

[0234] During the second growth reaction synthesis process, the atmosphere and temperature remain unchanged, and the precursor slurry is synthesized by continuous reaction. When the D50 particle size of the slurry in the second growth process is detected to reach 16 μm, the feeding is stopped to obtain the second reaction slurry;

[0235] S33, post-processing: adding the second reaction slurry to a filter press washing device for washing and filter pressing, washing with sodium hydroxide solution and pure water in turn, and then sending it to a drying process, and then screening through a 325-mesh filter and demagnetizing in turn to obtain the positive electrode precursor material of this embodiment.

[0236] Test example

[0237] 1. Porosity test

[0238] The positive electrode material precursor is milled into a particle sample using an ion thinning machine to observe the cross-section of the particle, and the particle is placed under a high-power electron microscope to observe the cross-section of the particle. The magnification of a single particle is 2.5k to 9.0k times to ensure that the cross-section presents a complete single particle.

[0239] On the cross section of the particle, along the extension direction from the center of the positive electrode material precursor particle to the particle surface, it is divided into the core region, the middle layer and the outer layer; among them, Figure 3 As shown in the figure, the crystal core region is the region extending 2μm from the center of the particle to the particle surface; the first intermediate layer is the region extending 1μm from the outer surface of the crystal core region to the particle surface, that is, the region with a particle radius of 2μm to 3μm; the second intermediate layer is the region extending 2μm from the outer surface of the first intermediate layer to the particle surface, that is, the region with a particle radius of 3μm to 5μm; the outer layer is the region extending outward from the outer surface of the second intermediate layer, that is, the region with a particle radius greater than 5μm. Figure 6 As shown, the crystal core region is a region extending 2 μm from the center of the particle to the surface of the particle; the first intermediate layer is a region extending 1 μm from the outer surface of the crystal core region to the surface of the particle, that is, a region with a particle radius of 2 μm to 3 μm; the second intermediate layer is a region extending 2 μm from the outer surface of the first intermediate layer to the surface of the particle, that is, a region with a particle radius of 3 μm to 5 μm; the third intermediate layer is a region extending 2 μm from the outer surface of the second intermediate layer to the surface of the particle, that is, a region with a particle radius of 5 μm to 7 μm; the outer layer region is a region extending outward from the outer surface of the third intermediate layer, that is, a region with a particle radius greater than 7 μm.

[0240] The porosity of the above regions is calculated according to the following formula: porosity = total pore area in the corresponding region / (total pore area in the corresponding region + total material area in the corresponding region) × 100%.

[0241] 2. D90 particle size, D50 particle size, D10 particle size

[0242] The D90, D50, and D10 particle sizes of the cathode material precursor were measured using a Malvern 3000 laser particle size analyzer. The sample, a small amount of dispersant (a mixture of ethanol, pure water, and a low-foaming surfactant), and pure water were added to a 50 mL beaker. Stir thoroughly with a glass rod to disperse the sample evenly. The sample was transferred to the sample cell of the Malvern 3000 laser particle size analyzer and the pump speed was set to 2500 rpm and the frequency to 19.5 Hz for particle size measurement. The SPAN value was calculated as (D90 - D10) / D50.

[0243] 3. Specific surface area

[0244] The specific surface area of ​​cathode material precursors was measured using a Micromeritics DX400 instrument. At constant temperature, the amount of gas adsorbed on the solid surface at different relative pressures was measured. The monolayer adsorption of the sample was then calculated based on the Brownauer-Etterling-Taylor adsorption theory and its formula (BET formula). The specific surface area of ​​the material was then calculated based on the monolayer adsorption.

[0245] 4. Sphericity

[0246] The positive electrode material precursor was milled into a particle sample using an ion milling machine to observe the cross section of the particle. The cross section of the particle was observed under a high-power electron microscope. The cross section area S and the perimeter L of the cross section of four positive electrode material precursor particles were measured respectively. According to the sphericity γ = 4πS / L 2 Get the mean sphericity value.

[0247] 5. Tap density

[0248] Place the powder sample in a container with a volume of V, and place the container containing the powder sample in a vibrating screen. The vibration frequency of the vibrating screen is between 100 Hz, the amplitude is 4 mm, and the vibration time is usually between 5 minutes. Take the container and the powder sample out of the vibrating screen, and use the electronic balance to measure the mass m of the powder sample after vibration again. Divide the mass m of the powder sample after vibration by the volume V of the container to obtain the tap density. Test multiple times and take the average value.

[0249] 6. XRD test

[0250] At least 15 particles are selected and X-ray diffraction pattern analysis is performed respectively, and the diffraction peak of the (001) crystal plane and the diffraction peak of the (101) crystal plane in the X-ray diffraction pattern are obtained, the diffraction peak intensity I(001) of the (001) crystal plane and the diffraction peak intensity I(101) of the (101) crystal plane are calculated, and the peak intensity ratio I(101) / I(001) is calculated.

[0251] 7. Battery performance test

[0252] (1) Preparation of positive electrode materials

[0253] The cathode material precursor and LiOH·H2O were mixed uniformly in a molar ratio of 1:1.05, sintered in a muffle furnace under an air atmosphere at a sintering temperature of 750°C for 12 hours, and then cooled to room temperature, crushed, and sieved to obtain a cathode material.

[0254] (2) Preparation of button batteries

[0255] The positive electrode material, conductive carbon black, and polytetrafluoroethylene (PVDF) were mixed in a mass ratio of 8:1:1 and dissolved in a solvent to form a slurry. The slurry was coated on aluminum foil, dried, and roll-pressed to obtain a positive electrode sheet. A metal lithium sheet was used as the counter electrode, the separator was Celgard C2400, the solute in the electrolyte was 1 mol / L LiPF6, and the solutes were ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1. The cells were assembled into button cells in an argon-filled glove box.

[0256] (3) Electrochemical performance test

[0257] An electrochemical workstation was used to set the frequency from 0.1 Hz to 1 MHz and the amplitude to less than 10 mV. The button cell was charged and discharged to 50% SOC at 25°C, and the impedance was tested.

[0258] The electrochemical performance of the button cell was tested using a Xinwei electrochemical workstation. Specifically, at 25°C, the button cell was charged at a constant current of 0.33C to 4.30V. This cycle was then repeated 100 times at a constant voltage, with the current gradually reduced to 0.05C. The cell was then discharged at a discharge rate of 0.33C to 3.0V. The discharge capacity (Q1) at the first cycle and the discharge capacity (Q100) at the 100th cycle were measured. The 100-cycle capacity retention was calculated as: 100-cycle capacity retention = Q100 / Q1 × 100%.

[0259] The button battery was charged and discharged at a current density of 0.33C in the charge and discharge range of 3.0 to 4.30V to obtain the first charge capacity and the first discharge capacity. The first coulombic efficiency was calculated according to the principle of first coulombic efficiency = first discharge capacity / first charge capacity.

[0260] The test results are shown in Tables 1 and 2.

[0261] Table 1

[0262]

[0263] Table 2

[0264]

[0265] According to Table 1, Figures 1 to 6 It can be seen that the areas outside the crystal core area of ​​the positive electrode material precursors of Examples 1 and 2 have a porosity that increases in the radial direction, and the primary particles in the outer area are spindle-shaped. Figures 7 to 12 It can be seen that the porosity of the positive electrode material precursors of Comparative Example 1 and Comparative Example 2 is basically the same, and the primary particles are in the form of flakes or blocks.

[0266] According to Table 2, compared with the comparative example, the battery assembled from the positive electrode material prepared from the positive electrode material precursor of the embodiment has obvious advantages in charge and discharge capacity and cycle stability, and has high capacity and high cycle stability.

[0267] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0268] The above are merely preferred embodiments of the present application and are not intended to limit the present application. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A cathode material precursor, characterized in that: The positive electrode material precursor includes a crystal core region, a middle region and an outer region from the inside out; Along the direction from the inside to the outside, the porosity of the middle region gradually increases, and the porosity of the outer region is greater than the porosity of the middle region.

2. The cathode material precursor according to claim 1, characterized in that The positive electrode material precursor satisfies at least one of the following conditions: a. The diameter of the crystal nucleus region is 1 to 5 μm; b. From the inside out, the middle region includes at least two middle layers; preferably, the middle region includes a first middle layer and a second middle layer, wherein the thickness of the first middle layer and the second middle layer are each independently 1 to 3 μm, and the porosity of the first middle layer is less than the porosity of the second middle layer; or, the middle region includes a first middle layer, a second middle layer, and a third middle layer, wherein the thickness of the first middle layer, the second middle layer, and the third middle layer are each independently 1 to 3 μm, and the porosity of the first middle layer is less than the porosity of the second middle layer, less than the porosity of the third middle layer, less than the porosity of the outer region; Preferably, the porosity of the first intermediate layer is less than 2%, the porosity of the second intermediate layer is 2% to 4%, 4% < the porosity of the third intermediate layer is ≤ 5%; 3% < the porosity of the outer layer is ≤ 10%; c. The overall average porosity of the positive electrode material precursor is 3.0% to 5.5%.

3. The cathode material precursor according to claim 1 or 2, characterized in that: The positive electrode material precursor satisfies at least one of the following conditions: a. The D50 particle size of the cathode material precursor is 6 μm to 30 μm; b. The specific surface area of ​​the cathode material precursor is 3m 2 / g~30m 2 / g; c. The particles of the cathode material precursor are spherical or quasi-spherical, with a sphericity of 0.77 to 0.99; d. The tap density of the cathode material precursor is 1.5 g / cm 3 ~2.5g / cm 3 ; e. The cathode material precursor has a diffraction peak of the (001) crystal plane and a diffraction peak of the (101) crystal plane in the X-ray diffraction pattern, and the diffraction peak intensity I(001) of the (001) crystal plane and the diffraction peak intensity I(101) of the (101) crystal plane satisfy: I(101) / I(001)=0.7~1.2; f. The particle size distribution width SPAN of the positive electrode material precursor is 0.25 to 0.

85.

4. The cathode material precursor according to claim 2, characterized in that The positive electrode material precursor includes secondary particles formed by stacking primary particles; The primary particles in the crystal core region, the first intermediate layer, and the second intermediate layer are in the shape of flakes, rods, or blocks; the primary particles in the third intermediate layer and the outer layer are in the shape of spindles. Preferably, when the primary particles are spindle-shaped, the average length of the primary particles is 220 to 600 nm, and the average width is 50 to 80 nm; When the primary particles are flaky in shape, the average thickness of a single layer of the primary particles is 5 to 200 nm, the average length of a single layer of the primary particles is 200 to 450 nm, and the number of flaky layers of the primary particles is ≥3; When the primary particles are rod-shaped, the aspect ratio of the primary particles is 20-200.

5. The cathode material precursor according to claim 1 or 2, characterized in that: The chemical formula of the positive electrode material precursor includes Ni x Co y M z T k (OH) 2-k , M is selected from at least one of Mn, Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, and Al, and T is selected from at least one of F, P, B, and O; wherein 0 <x≤1,0≤y<1,0≤z<1,0≤k<1; Preferably, 0.8≤x<1, 0≤y≤0.2, 0≤z≤0.2, and 0≤k≤0.

5.

6. A method for preparing the positive electrode material precursor according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, adding a metal salt solution, a precipitant, and a complexing agent to a first reaction base solution to form a first reaction system; and allowing the first reaction system to undergo a first growth to obtain a seed crystal; S2, adding a metal salt solution, a precipitant, and a complexing agent to a second reaction base solution containing the seed crystal to form a second reaction system; and allowing the second reaction system to undergo a second growth to obtain a positive electrode material precursor; In the second growth process, the feeding rate of the metal salt solution is gradually increased, and the feeding rates of the precipitant and the complexing agent are first gradually increased and then gradually decreased.

7. The method for preparing a cathode material precursor according to claim 6, wherein: The preparation method satisfies at least one of the following conditions: a. During the second growth period of 0 to 2 hours, the feeding rate of the metal salt solution is D1; ​​during the second growth period of 2 hours to 10 hours, the feeding rate of the metal salt solution is increased uniformly at a rate of 1 L / h to 5 L / h. D2; After 10 hours of the second growth, the feeding rate of the metal salt solution is D2, wherein, D2>D1; Preferably, D1 and D2 are each independently 10 L / h to 60 L / h; b. During the second growth period of 0 to 2 hours, the feeding rate of the complexing agent is E1; during the second growth period of 2 hours to 10 hours, the feeding rate of the complexing agent is increased at a uniform rate of 0.1L / h to 1L / h to E2; during the second growth period of 10 hours to 16 hours, the feeding rate of the complexing agent is E2; during the second growth period of 16 hours to 18 hours, the feeding rate of the complexing agent is uniformly reduced at a rate of 0.1L / h to 1L / h to E3; after 18 hours of the second growth period, the feeding rate of the complexing agent is E3; wherein, E2>E3>E1; Preferably, E1, E2, and E3 are each independently 0.4 L / h to 10 L / h; c. During the 0-2h period of the second growth, the feed flow rate of the precipitant is H1; during the 2-10h period of the second growth, the feed flow rate of the precipitant is increased uniformly at an increasing rate of 0.2L / h to 2L / h to H2; during the 10-16h period of the second growth, the feed flow rate of the precipitant is H2; during the 16-18h period of the second growth, the feed flow rate of the precipitant is decreased uniformly at a decreasing rate of 0.2L / h to 2L / h to H3; after 18h of the second growth, the feed flow rate of the precipitant is H3; wherein, H2>H3>H1; Preferably, H1, H2, and H3 are each independently 5 L / h to 20 L / h; d. During the first 0 to 15 hours of the second growth, the pH of the second reaction system at 45°C is F1; during the first 15 to 18 hours of the second growth, the pH of the second reaction system decreases uniformly at a rate of 0.002 / h to 0.3 / h at 45°C to F2; after 18 hours of the second growth, the pH of the second reaction system at 45°C is F2; ​​wherein F1>F2; Preferably, F1 and F2 are each independently 10.35 to 10.60 at 45°C; e. During the 0-2h period of the second growth, the ammonia concentration of the second reaction system is G1; during the 2-10h period of the second growth, the ammonia concentration of the second reaction system increases uniformly at a rate of 0.05g / L·h to 0.3g / L·h to G2; during the 10-16h period of the second growth, the ammonia concentration of the second reaction system is G2; during the 16-18h period of the second growth, the ammonia concentration of the second reaction system decreases uniformly at a rate of 0.05g / L·h to 0.3g / L·h to G3; after 18h of the second growth, the ammonia solubility of the second reaction system is G3; wherein, G2>G3>G1; Preferably, G1, G2, and G3 are 2.2 g / L to 4.6 g / L; f. During the second growth process, the stirring speed of the second reaction system is gradually reduced.

8. The method for preparing a cathode material precursor according to claim 6 or 7, characterized in that: The preparation method satisfies at least one of the following conditions: a. The metal salt solution comprises a soluble salt of a nickel salt and a cobalt salt, wherein the soluble salt comprises at least one of a nitrate, a chloride, and a sulfate, and the concentration of the metal salt in the metal salt solution is 120 g / L to 145 g / L; preferably, the metal salt further comprises at least one of a salt formed by an M element and a salt formed by an T element; b. The complexing agent comprises an aqueous ammonia solution, wherein the concentration of NH3 in the aqueous ammonia solution is 7% to 10%; c. The precipitant comprises a sodium hydroxide solution having a concentration of 200 g / L to 450 g / L; d. The solid content of the first reaction system and the second reaction system are each independently 400g / L to 800g / L; e. The ammonia concentration of the first reaction base solution is 3.0 g / L ~ 4.5 g / L, and the pH value of the first reaction base solution is 10.55 ~ 11.95 at 45 ° C; f. The ammonia concentration of the second reaction base liquid is 1.0 to 4.0 g / L, and the pH value of the second reaction base liquid is 10.40 to 11.80 at 45 ° C; g. The reaction temperature of the first growth and the second growth is 50 ℃ ~ 90 ℃; h. Both the first growth and the second growth are performed under stirring, and the stirring speed is 50 rpm to 500 rpm.

9. A positive electrode material, characterized in that The positive electrode material is prepared by calcining a positive electrode material precursor and a lithium source, wherein the positive electrode material precursor includes the positive electrode material precursor according to any one of claims 1 to 5 or the positive electrode material precursor prepared by the preparation method of the positive electrode material precursor according to any one of claims 6 to 8.

10. A battery, characterized in that: Comprising the positive electrode material according to claim 9.

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