High-nickel ternary positive electrode material and preparation method thereof, positive electrode plate and lithium battery

Abstract

The invention relates to the technical field of lithium batteries, in particular to a high-nickel ternary positive electrode material, a preparation method thereof, a positive electrode plate and a lithium battery. The positive electrode material comprises complete type sphere-like secondary particles and defect type sphere-like secondary particles, the number ratio of the defect type sphere-like secondary particles to the complete type sphere-like secondary particles is smaller than or equal to 10%, and the content of the defect type sphere-like secondary particles is low; and the high energy density of the material can be fully exerted.

Description

Technical Field

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

[0002] In recent years, the new energy vehicle industry has developed rapidly. Long driving range is the primary technical indicator of new energy vehicles. On the premise of ensuring safety, continuously improving energy density is an inevitable development trend. Among them, LiNi, a high-nickel ternary cathode material with a layered structure, x Co y Mn z O2 (x ≥ 0.8) can provide higher energy density and better meet the long mileage requirements of new energy vehicles.

[0003] The sintering process of ternary materials is a high-temperature solid-phase reaction, which refers to the solid-phase reaction between the precursor and the lithium source at a certain temperature, and sintering for a certain period of time to generate a complete crystalline positive electrode material. The sintering process is one of the core preparation processes for synthesizing ternary positive electrode materials, among which sintering temperature, sintering time and sintering atmosphere are important factors affecting the electrochemical properties of ternary materials. The sintering processes used to synthesize ternary positive electrode materials from precursors generated by different processes are different. Most of the research on process parameters focuses on sintering temperature and time, while ignoring the influence of heating rate.

[0004] For high-nickel ternary materials, the traditional sintering process is prone to over-burning or insufficient sintering. Common problems are severe cracking and crushing of quasi-spherical secondary particles, and an increase in the proportion of defective quasi-spherical secondary particles in complete quasi-spherical secondary particles. When the sintered positive electrode material is screened, it is difficult to separate the defective secondary particles of hemisphere and above from the complete secondary particles. The active material of the positive electrode sheet is a mixture of defective secondary particles and complete secondary particles. The defective secondary particles have a collapsed layered structure and a smaller specific surface area, which is not conducive to the release and embedding of lithium ions in the lattice, and will seriously affect the electrochemical performance of the positive electrode material. Therefore, it is of great significance to reduce the defect rate in the positive electrode material. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem of low initial discharge capacity of positive electrode materials caused by insufficient sintering or over-burning in the prior art through a dynamic combined temperature-raising sintering process, and to provide a high-nickel ternary positive electrode material and a preparation method thereof, a positive electrode sheet and a lithium battery. In the high-nickel ternary positive electrode material of the present invention, the content of defective spherical secondary particles is low. The high-nickel ternary positive electrode material of the present invention is applied to a lithium battery to improve the initial discharge capacity of the lithium battery.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a high-nickel ternary positive electrode material, which includes complete spherical secondary particles and defective spherical secondary particles, and the ratio of the number of defective spherical secondary particles to the number of complete spherical secondary particles is ≤15%.

[0007] A second aspect of the present invention provides a method for preparing the high-nickel ternary positive electrode material of the present invention, comprising the following steps:

[0008] Sintering a mixture of a high-nickel ternary positive electrode material precursor and a lithium salt through at least two stages of gradient temperature increase to obtain a high-nickel ternary positive electrode material;

[0009] The heating rate of the latter stage of gradient temperature rise sintering is 10%-50% of the heating rate of the former stage of gradient temperature rise sintering.

[0010] A third aspect of the present invention provides a positive electrode plate, which contains the high-nickel ternary positive electrode material.

[0011] A fourth aspect of the present invention provides a lithium battery, comprising a positive electrode sheet, a negative electrode sheet, a separator for isolating the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is the positive electrode sheet described in the present invention.

[0012] Through the above technical scheme, unlike the prior art that improves the energy density of positive electrode materials by doping modification and surface coating, in the present invention, the high-nickel ternary positive electrode material is a mixture of complete spherical secondary particles and defective spherical secondary particles formed by agglomeration of primary particles. In the high-nickel ternary positive electrode material of the present invention, the content of defective spherical secondary particles is low; the high energy density of the material itself can be fully utilized; and according to the preferred embodiment of the invention, the primary particles forming the secondary particles have a small particle size and high density, which can fully utilize the high energy density of the material itself. The high-nickel ternary positive electrode material is used to prepare lithium batteries, which can improve the initial discharge capacity.

[0013] In the present invention, by dynamically combining the temperature-raising sintering process, the temperature is quickly raised to medium-low temperature sintering in the first sintering stage, which can effectively decompose the adsorbed water in the precursor and lithium source mixture in a short time and promote the diffusion of lithium ions; the heating rate in the second sintering stage is matched with the heating rate of the first sintering stage, which can ensure that the layered structure of the material is not destroyed, reduce the defect rate of the positive electrode material, and reduce the proportion of defective spherical secondary particles, effectively solving the problem of insufficient sintering or overburning in the traditional sintering process. It can be seen from the embodiment of the present invention that the first discharge capacity of the lithium battery prepared by the high-nickel ternary positive electrode material of the present invention can reach up to 231mAh / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a SEM image of the positive electrode material prepared in Example 1;

[0015] Figure 2 This is a SEM image of the positive electrode material prepared in Example 2;

[0016] Figure 3 This is a SEM image of the positive electrode material prepared in Example 3;

[0017] Figure 4 This is a SEM image of the positive electrode material prepared in Example 4;

[0018] Figure 5 This is a SEM image of the positive electrode material prepared in Example 5;

[0019] Figure 6 This is a SEM image of the positive electrode material prepared in Comparative Example 1;

[0020] Figure 7 The overall SEM morphology of the positive electrode material prepared in Example 1;

[0021] Figure 8 This is the overall SEM morphology of the positive electrode material prepared in Comparative Example 1. DETAILED DESCRIPTION

[0022] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0023] The definition of secondary particles in this field: When the crystals are very small, due to the large surface energy of the grains, the small grains are easily combined together due to weak interaction forces, resulting in agglomeration between the grains, that is, many small grains gather together to form larger particles.

[0024] In the present invention, primary particles and secondary particles are conventionally defined in the art, wherein primary particles refer to single crystal grains with elongated or blocky morphology; secondary particles refer to polycrystalline particles formed by the accumulation of primary particles.

[0025] In the present invention, the complete spherical secondary particles refer to polycrystalline particles without cracking.

[0026] In the present invention, the defective quasi-spherical secondary particles refer to polycrystalline particles in a state between hemispherical and complete.

[0027] In the present invention, the ratio of the number of defective spherical secondary particles to the number of complete spherical secondary particles is calculated by counting the number of defective spherical secondary particles and complete spherical secondary particles in the overall scanning electron microscope (SEM) image of the high-nickel ternary positive electrode material.

[0028] The first aspect of the present invention provides a high-nickel ternary positive electrode material, which includes complete spherical secondary particles and defective spherical secondary particles, and the number ratio of defective spherical secondary particles to complete spherical secondary particles is ≤15%.

[0029] In the present invention, the high-nickel ternary positive electrode material is a mixture of complete spherical secondary particles and defective spherical secondary particles formed by agglomeration of primary particles. In the high-nickel ternary positive electrode material of the present invention, the content of defective spherical secondary particles is low, which can give full play to the high energy density of the material itself.

[0030] According to a preferred embodiment of the present invention, the average particle size of the secondary particles is 5-15 μm.

[0031] The average particle size was measured by Malvern 3000 laser particle size analyzer.

[0032] In the present invention, the high energy density of the material itself can be fully utilized when the ratio of defective spherical secondary particles to complete spherical secondary particles is less than or equal to 15%; the ratio of defective spherical secondary particles to complete spherical secondary particles can be 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 5%, 4%, 3%, 2%, 1%; preferably, the ratio of defective spherical secondary particles to complete spherical secondary particles is ≤10%, which can further give full play to the high energy density of the material itself.

[0033] According to a preferred embodiment of the present invention, the average particle size of the primary particles forming the secondary particles is 100-1000 nm, preferably 100-500 nm, and more preferably 100-300 nm.

[0034] In the present invention, the types of the positive electrode material can be selected from a wide range. According to a preferred embodiment of the present invention, the chemical formula of the high-nickel ternary positive electrode material is LiNi x Co y Mn z O2, 0.8≤x<1, 0.05≤y<0.1, and x+y+z=1.

[0035] According to a preferred embodiment of the present invention, x is 0.9-0.96.

[0036] A second aspect of the present invention provides a method for preparing the high-nickel ternary positive electrode material of the present invention, comprising the following steps:

[0037] Sintering a mixture of a high-nickel ternary positive electrode material precursor and a lithium salt through at least two stages of gradient temperature increase to obtain a high-nickel ternary positive electrode material;

[0038] The heating rate of the latter stage of gradient temperature rise sintering is 10%-50% of the heating rate of the former stage of gradient temperature rise sintering.

[0039] In the present invention, the heating rate of the first stage of heating sintering is 1-10°C / min, preferably 2-8°C / min.

[0040] According to a preferred embodiment of the present invention, a high-nickel ternary positive electrode material is obtained by two-stage gradient temperature sintering. Preferably,

[0041] In the first stage of sintering, the heating rate is 2-8℃ / min, and the temperature is raised to the low temperature stage for 2-8h;

[0042] In the second stage of sintering, based on the low temperature stage, the heating rate is 10%-50% of the heating rate in the first stage, and the temperature is raised to the high temperature stage for sintering for 6-20 hours.

[0043] In the present invention, by dynamically combining the temperature-raising sintering process, the temperature is quickly raised to medium-low temperature for sintering in the first sintering stage, which can effectively decompose the adsorbed water in the precursor and the lithium source mixture in a short time and promote the diffusion of lithium ions; the temperature-raising rate in the second sintering stage is matched with the temperature-raising rate in the first sintering stage, which can ensure that the layered structure of the material is not destroyed, reduce the defect rate of the positive electrode material, and reduce the proportion of defective spherical secondary particles, effectively solving the problem of insufficient sintering or over-burning in the traditional sintering process.

[0044] According to a preferred embodiment of the present invention, the temperature of the low temperature section is 400-600°C.

[0045] According to a preferred embodiment of the present invention, the temperature of the high temperature section is 600-900°C.

[0046] In the present invention, the sintering is carried out in an oxygen-rich atmosphere. According to a preferred embodiment of the present invention, the oxygen concentration is not less than 99%.

[0047] According to a preferred embodiment of the present invention, the high-nickel ternary positive electrode material precursor is calculated based on the total amount of metal elements, the lithium salt is calculated based on lithium, and the molar ratio of the high-nickel ternary positive electrode material precursor to the lithium salt is 1:1.0051.07.

[0048] In the present invention, the types of the lithium salt can be selected from a wide range. According to a preferred embodiment of the present invention, the lithium salt is selected from one or more of lithium hydroxide, lithium carbonate, and lithium sulfate.

[0049] According to a preferred embodiment of the present invention, the high-nickel ternary positive electrode material precursor Ni x Co y Mn z (OH)2, wherein 0.8≤x<1, 0.05≤y<0.1, and x+y+z=1; preferably, x is 0.9-0.96.

[0050] According to a preferred embodiment of the present invention, the temperature difference between the high temperature section and the low temperature section is 150-300° C., preferably 170-250° C. On the basis of controlling the heating rate of the second stage sintering, controlling the temperature difference between the high temperature section and the low temperature section is beneficial to further improve the high energy density of the material itself.

[0051] According to a preferred embodiment of the present invention, the method for preparing the high-nickel ternary positive electrode material further comprises: after the second-stage sintering, cooling to below 100° C., taking out the positive electrode material, grinding it, and sieving it to obtain the positive electrode material.

[0052] In the present invention, grinding and sieving are conventional operations in the art, and there is no limitation on the conditions.

[0053] A third aspect of the present invention provides a positive electrode plate, which contains the high-nickel ternary positive electrode material.

[0054] The fourth aspect of the present invention provides a lithium battery, comprising a positive electrode sheet, a negative electrode sheet, a separator for isolating the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the positive electrode sheet is the positive electrode sheet of the present invention. The high-nickel ternary positive electrode material is used to prepare a lithium battery, which can improve the initial discharge capacity.

[0055] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0056] In the following examples, normal temperature refers to 25-30°C.

[0057] Example 1

[0058] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.01), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0059] The first sintering process: heating from room temperature to 500°C at a rate of 5°C / min and then sintering for 4h;

[0060] Second stage sintering process: heating from 500℃ to 720℃ at a rate of 1℃ / min and then sintering for 12h;

[0061] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0062] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0063] Example 2

[0064] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium sulfate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.03), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0065] The first sintering process: heating from room temperature to 550°C at a rate of 5°C / min and then sintering for 4h;

[0066] Second stage sintering process: heating from 550℃ to 740℃ at a rate of 2℃ / min and sintering for 12h;

[0067] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0068] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0069] Example 3

[0070] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium hydroxide are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.01), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0071] The first sintering process: heating from room temperature to 500°C at a rate of 8°C / min and then sintering for 4h;

[0072] Second stage sintering process: heating from 500℃ to 720℃ at a rate of 4℃ / min and then sintering for 12h;

[0073] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0074] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0075] Example 4

[0076] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.05), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0077] The first sintering process: heating from room temperature to 550℃ at a rate of 7℃ / min and then sintering for 4h;

[0078] Second stage sintering process: heating from 550℃ to 820℃ at a rate of 3℃ / min and sintering for 12h;

[0079] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0080] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0081] Example 5

[0082] Ni 0.83 Co 0.05 Mn 0.12 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.05), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0083] The first sintering process: heating from room temperature to 550°C at a rate of 5°C / min and then sintering for 4h;

[0084] Second stage sintering process: heating from 550℃ to 780℃ at a rate of 2℃ / min and sintering for 12h;

[0085] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0086] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0087] Example 6

[0088] The method of Example 1 is different in that the temperature of the two-stage sintering process is different, specifically: the second-stage sintering process: heating from 500°C to 820°C at a rate of 1°C / min and then sintering for 8h; the other conditions are the same as Example 1.

[0089] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0090] Comparative Example 1

[0091] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.01), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0092] The first sintering process: heating from room temperature to 500°C at a rate of 5°C / min and then sintering for 4h;

[0093] Second stage sintering process: heating from 500℃ to 720℃ at a rate of 5℃ / min and then sintering for 12h;

[0094] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0095] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0096] Comparative Example 2

[0097] Ni 0.9 Co 0.05 Mn 0.05 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a proportion (molar ratio (Ni+Co+Mn):Li=1:1.03), two-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0098] The first sintering process: heating from room temperature to 550°C at a rate of 10°C / min and then sintering for 4h;

[0099] Second stage sintering process: heating from 550℃ to 740℃ at a rate of 1℃ / min and then sintering for 12h;

[0100] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0101] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0102] Comparative Example 3

[0103] Ni 0.83 Co 0.05 Mn 0.12 After the (OH)2 precursor and lithium carbonate are uniformly mixed in a molar ratio of (Ni+Co+Mn):Li=1:1.05), a second-stage sintering is performed in an oxygen atmosphere with a concentration of 99%;

[0104] The first sintering process: heating from room temperature to 550°C at a rate of 5°C / min and then sintering for 4h;

[0105] Second stage sintering process: heating from 550℃ to 780℃ at a rate of 4℃ / min and sintering for 12h;

[0106] After sintering, wait until the temperature drops below 100°C, take out and grind, and sieve through a 400-mesh sieve to obtain the positive electrode material.

[0107] The ratio of the number of defective quasi-spherical secondary particles to the number of complete quasi-spherical secondary particles in the positive electrode material, the particle size of the positive electrode material and the particle size of the primary particles are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] Figure 1 The SEM image of the positive electrode material prepared in Example 1, Figure 2 The SEM image of the positive electrode material prepared in Example 2, Figure 3 The SEM image of the positive electrode material prepared in Example 3, Figure 4 This is the SEM image of the positive electrode material prepared in Example 4. Figure 1 and Figure 2 It can be seen that under reasonable heating conditions during the entire dynamic sintering process, the primary particle nucleus of the material is small and has a high density; Figure 3 and Figure 4 When the ratio of the staged combined heating rate increases during the sintering process, it can be seen that the crystal nucleus of the primary particles is significantly enlarged, indicating that the ratio of the staged combined heating rate in the sintering process has a great influence on the crystal nucleus size of the primary particles of the positive electrode material.

[0112] Figure 5 This is the SEM image of the positive electrode material prepared in Preparation Example 5. Figure 5It can be seen that although the primary crystal nucleus increases due to the increase in sintering temperature, the density of the entire secondary particles is relatively high when the second stage sintering heating rate is controlled within the range of 10%-50%.

[0113] Figure 6 This is the SEM image of the positive electrode material prepared in Comparative Example 1. It can be seen that when a reasonable dynamic combined temperature rise sintering process is not adopted, uneven sintering and insufficient growth of primary particle nuclei are likely to occur.

[0114] Figure 7 This is the overall morphology of the positive electrode material of Example 1. Figure 8 This is the overall morphology of the positive electrode material of Comparative Example 1. It can be seen that during the sintering process of the high-nickel ternary positive electrode material, the spherical secondary particles are prone to cracking and breaking. In Example 1, the ratio of defective spherical secondary particles to complete spherical secondary particles is 10%, while in Comparative Example 1, the ratio of defective spherical secondary particles to complete spherical secondary particles reaches 30%.

[0115] Test Case

[0116] The positive electrode material is mixed with the conductive agent acetylene black (AB) and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) is used as a solvent. The mixture is placed in a small beaker and stirred at a speed of 800r / min for 2h to obtain a slurry. The slurry is coated on the current collector aluminum foil using an automatic coating machine, placed flat on tempered glass and transferred to a vacuum drying oven at 120 degrees Celsius for 4h, punched into a pole piece with a diameter of 12mm, and then dried at 105℃ in a vacuum drying oven for 4h. It is placed in a glove box filled with argon atmosphere with a water content and oxygen content of less than 0.1ppm for 4h to reduce the moisture adsorbed by the pole piece during the transfer process, and then assembled into a CR2032 button cell in the glove box. The battery uses a pure metal lithium sheet with a diameter of 16mm and a thickness of 0.5mm as the negative electrode, and a porous polyethylene film of Celgard2300 with a diameter of 18mm as the diaphragm.

[0117] After the battery was assembled and aged for 12 hours, charge and discharge tests were performed at different potentials. The results are shown in Table 2.

[0118] Table 2

[0119] Source of positive electrode material 0.1C charging mAh / g 0.1C discharge mAh / g First coulombic efficiency / % Example 1 263.5 231.4 87.8 Example 2 262.5 230.0 87.6 Example 3 253.5 220.0 86.8 Example 4 251.2 218.2 86.9 Example 5 239.8 206.6 86.2 Example 6 240.0 204.7 85.3 Comparative Example 1 241.1 199.9 82.9 Comparative Example 2 255.3 214.6 84.1 Comparative Example 3 218.7 182.1 83.3

[0120] Table 2 shows the performance test data of the ternary positive electrode materials prepared corresponding to Examples 1-6 and Comparative Examples 1-3. The ternary positive electrode materials prepared by the segmented sintering process in the preparation method of the present invention are significantly superior to the sintering process used in the existing conventional preparation method in terms of the first charge and discharge capacity and the first charge and discharge efficiency.

[0121] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A high-nickel ternary positive electrode material, characterized in that: The positive electrode material comprises complete quasi-spherical secondary particles and defective quasi-spherical secondary particles, and the quantity ratio of the defective quasi-spherical secondary particles to the complete quasi-spherical secondary particles is ≤15%.

2. The high-nickel ternary positive electrode material according to claim 1, wherein: The average particle size of the secondary particles is 5-15 μm; and / or The ratio of defective quasi-spherical secondary particles to complete quasi-spherical secondary particles is ≤ 10%; and / or The average particle size of the primary particles forming the secondary particles is 100-1000 nm, preferably 100-500 nm.

3. The high-nickel ternary positive electrode material according to claim 1 or 2, wherein: The chemical formula of the high nickel ternary positive electrode material is LiNi x Co y Mn z O2, 0.8≤x<1, 0.05≤y<0.1, and x+y+z=1; preferably, x is 0.9-0.

96.

4. The method for preparing the high-nickel ternary positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: Sintering a mixture of a high-nickel ternary positive electrode material precursor and a lithium salt through at least two stages of gradient temperature increase to obtain a high-nickel ternary positive electrode material; The heating rate of the first stage of sintering is 2-8℃ / min; The heating rate of the latter stage of gradient temperature rise sintering is 10%-50% of the heating rate of the former stage of gradient temperature rise sintering.

5. The preparation method according to claim 4, wherein The high-nickel ternary positive electrode material is obtained by two-stage gradient temperature sintering; preferably, In the first stage of sintering, the heating rate is 2-8℃ / min, and the temperature is raised to the low temperature stage for 2-8h; In the second stage of sintering, based on the low temperature stage, the heating rate is 10%-50%, preferably 20%-40% of the heating rate of the first stage, and the temperature is raised to the high temperature stage for sintering for 6-20 hours.

6. The preparation method according to claim 4 or 5, wherein: The temperature of the low temperature section is 400-600°C, preferably 450-550°C; and / or The high temperature section temperature is 600-900°C, preferably 700-800°C; and / or The sintering is carried out in an oxygen-rich atmosphere, preferably, the oxygen volume concentration is not less than 99%; and / or The high-nickel ternary positive electrode material precursor is calculated based on the total amount of metal elements, and the lithium salt is calculated based on lithium. The molar ratio of the high-nickel ternary positive electrode material precursor to the lithium salt is 1:1.0051.

07.

7. The preparation method according to claim 4 or 5, wherein: The lithium salt is selected from one or more of lithium hydroxide, lithium carbonate and lithium sulfate; and / or The high nickel ternary cathode material precursor Ni x Co y Mn z (OH)2, wherein 0.8≤x<1, 0.05≤y<0.1, and x+y+z=1; preferably, x is 0.9-0.

96.

8. The preparation method according to claim 4 or 5, wherein: The temperature difference between the high temperature section and the low temperature section is 150-300°C.

9. A positive electrode sheet, characterized in that: The positive electrode sheet contains the high-nickel ternary positive electrode material described in any one of claims 1-3.

10. A lithium battery comprising a positive electrode sheet, a negative electrode sheet, a separator for isolating the positive electrode sheet and the negative electrode sheet, and an electrolyte, characterized in that: The positive electrode sheet is the positive electrode sheet according to claim 9.

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