Positive electrode material, positive electrode sheet and lithium-ion battery

Abstract

The present invention relates to the technical field of lithium-ion battery materials, specifically discloses a positive electrode material, and also relates to a preparation method therefor and a lithium-ion battery comprising the positive electrode material. The chemical formula of the positive electrode material provided by the present invention is LiaNibCocN1dM(1-b-c-d-e)N2eO2. The positive electrode material provided by the present invention can achieve a higher capacity during charging and discharging, and the cycling stability of the positive electrode material is significantly improved.

Description

Positive electrode materials, positive electrode sheets and lithium-ion batteries Cross-reference to related applications

[0001] This application claims priority to Chinese patent application filed on December 26, 2024, with application number 202411959508.4 and entitled "Cathode Material, Preparation Method and Lithium-ion Battery". Technical Field

[0002] This invention relates to the field of lithium-ion battery materials technology, specifically to a cathode material, its cathode sheet, and a lithium-ion battery including the cathode material. Background Technology

[0003] In existing technologies, lithium ions in some cathode materials exhibit long diffusion paths during charge and discharge, resulting in poor rate performance and cycle stability. To improve the rate performance and cycle stability of cathode materials, existing technologies generally employ bulk doping techniques.

[0004] However, when some elements are doped into the crystal lattice, it will cause lattice expansion. In addition, the cathode material will also cause lattice expansion during long-term cycling. The superposition of the two effects will make it easier for microcracks to be generated inside the cathode material particles, which will then cause the particles to crack and deteriorate the performance of lithium batteries.

[0005] Therefore, improving the rate performance and cycle stability of cathode materials remains an urgent technical problem to be solved. Summary of the Invention

[0006] One objective of this invention is to provide a cathode material, and another objective is to provide a method for preparing the cathode material described herein. Furthermore, another objective of this invention is to provide a lithium-ion battery comprising the cathode material.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0008] In a first aspect, the present invention provides a cathode material, the chemical formula of which is: Li a Ni b Co c N1 d M (1-b-c-d-e) N2 eO2, where: 0.95≤a≤1.2, 0<b≤1, 0<c≤1, 0<d≤1, 0≤e<1, and b+c+d+e<1; element M is selected from at least one element in Group IA or Group IIA of the periodic table; element N1 is selected from at least one of Mn or Al; element N2 is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, and Y.

[0009] The cathode material comprises multiple grains, and the cross-section of each grain includes a central region and a surface region. The cross-section of the grain is tested by EDS, and the average concentration of element M in the central region is measured to be X1, and the average concentration of element M in the surface region is measured to be X2. X1 and X2 satisfy: 1.2≤X2 / X1≤20.

[0010] In a second aspect, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material described in the first aspect above.

[0011] Thirdly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material described in the first aspect above or the positive electrode sheet described in the present invention.

[0012] The cathode material provided by this invention uses element M selected from Group IA and Group IIA of the periodic table. The concentration of element M in the grain is controlled to satisfy 1.2≤X2 / X1≤20, resulting in a higher content of element M near the grain surface. This increases the unit cell volume of the grain surface region, while the content of element M near the grain center region is lower, resulting in a relatively smaller unit cell volume at the grain center. This creates compressive stress from the grain surface towards the center, which can suppress lattice expansion during charging and discharging, thereby improving gas generation performance and long-term cycle performance. Attached Figure Description

[0013] Figure 1 is a schematic diagram of the element M concentration distribution test in the grains of the cathode material of the present invention;

[0014] Figure 2 is a comparison of the concentration distribution of K element on the cross-section of multiple particles obtained by line scanning of the cathode materials provided in Embodiments 1, 6, 7 and Comparative Example 2 of the present invention.

[0015] Figure 3 is a comparison of the concentration distribution of Mg element in the cross-sections of multiple particles obtained by line scanning of the cathode materials provided in Embodiments 2, 6, 10 and Comparative Example 2 of the present invention.

[0016] Figure 4 is a comparison diagram of the internal cracks in the cathode materials provided in Embodiment 6 and Comparative Example 2 of the present invention;

[0017] Figure 5 is a schematic diagram of a lithium-ion battery in a discharge state provided by the present invention;

[0018] Figure 6 is an illustration of the spot scan area during the testing of the average concentration X1 of element M in the central region and the average concentration X2 of element M in the surface region of the positive electrode material of the present invention.

[0019] Figure 7 is a schematic diagram of the characterization of strip-shaped particles in the cathode material of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be understood that the terms "first," "second," "third," and "fourth," etc., in the claims, specification, and drawings of this invention are used to distinguish different objects, rather than to describe a specific order. The terms "comprising" and "including" used in the specification and claims of this invention indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0022] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0023] Unless otherwise specified, the materials, reagents and equipment used in the embodiments and comparative examples of this application are all obtained from conventional commercial channels.

[0024] In a first aspect, the present invention provides a cathode material having the chemical formula: Li a Ni b Co c N1 d M (1-b-c-d-e) N2 eO2, where: 0.95≤a≤1.2, 0<b≤1, 0<c≤1, 0<d≤1, 0≤e<1, and b+c+d+e<1; element M is selected from at least one element in Group IA or Group IIA of the periodic table; element N1 is selected from at least one of Mn or Al; element N2 is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, and Y.

[0025] The cathode material comprises multiple grains. The cross-section of the grains is tested by EDS. The cross-section of the grains includes a central region and a surface region. The average concentration of element M in the central region is measured as X1, and the average concentration of element M in the surface region is measured as X2. X1 and X2 satisfy: 1.2≤X2 / X1≤20.

[0026] Therefore, by selecting element M from Group IA and Group IIA of the periodic table and controlling the concentration of element M in the grain to satisfy 1.2≤X2 / X1≤20, the content of element M in the surface region of the grain is relatively high, which increases the unit cell volume in the surface region of the grain. Meanwhile, the content of element M in the central region of the grain is relatively low, which makes the unit cell volume in the central region of the grain relatively small. This creates compressive stress from the surface of the grain toward the center. The compressive stress can suppress lattice expansion during the charging and discharging process, thereby improving gas generation performance and long-term cycling performance.

[0027] It should be noted that, since the ionic radius of element M is larger than that of elements Ni, Co, and Ni, after element M enters the transition metal layer and occupies the sites of elements Ni / Co / Ni, element M will increase the interlayer spacing of the transition metal layer, thereby increasing the unit cell volume. When element M is enriched near the grain surface, the unit cell volume of the grain surface region will be larger than that of the grain center region. The stress in the grain surface region is greater, which generates compressive stress towards the grain center, thus causing the grain to tend to shrink from the surface to the grain center (i.e., shrinkage state).

[0028] It should be noted that, as shown in Figure 1, in the cross-sectional view of the grain, within the circumscribed circle of the grain's cross-section, the center of the circumscribed circle is taken as the center, and the radius of the circumscribed circle is taken as the grain radius L. The region from the grain center to a distance L / 2 from the grain center is the central region, and the region from the L / 2 position of the grain to the grain surface is the surface region. Further, in the cross-sectional view of the cathode material, the diameter L of the grain is taken as the diameter of the intersection of the grain's circumscribed circle and the grain edge. The region covered by the central region of the circumscribed circle is the central region of the grain (i.e., from the grain center to a distance L / 2 from the grain center), and the region covered by the surface region of the circumscribed circle is the surface region (the region from the L / 2 position of the grain to the grain surface). For irregularly shaped particles, such as elongated particles, as shown in Figure 7, in the cross-sectional view of the particle, the center of the circumscribed circle is the center of the grain, the diameter L of the grain is the diameter of the grain where the circumscribed circle intersects the edge of the grain, the part of the grain covered by the surface region of the circumscribed circle is the surface region of the grain, and the region of the grain covered by the central region of the circumscribed circle is the central region of the grain.

[0029] In some preferred embodiments, element M is selected from at least one element in Group IA or Group IIA of the periodic table, such as at least one selected from Na, K, Mg, Ca, Sr, Ba, Rb, and Cs. These elements are in a single valence state, and their valence state is fixed after oxidation, which plays a role in stabilizing the crystal structure of the cathode material. Furthermore, the ionic radii of these elements are relatively large. After entering the transition metal layer and occupying the sites of Ni / Co / Ni elements, the large ionic radius of element M will increase the interlayer spacing of the transition metal layer, thereby increasing the unit cell volume.

[0030] In some preferred embodiments, element N1 is selected from at least one of Mn or Al. Selecting Mn or Al as element N1 can help stabilize the crystal structure of the cathode material.

[0031] In some preferred embodiments, element N2 is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, and Y. Selecting this element N2 can stabilize the crystal structure of the cathode material and improve its ionic conductivity. Furthermore, by coating the particle surface, element N2 can also delay the reaction between the cathode material and the electrolyte.

[0032] In one embodiment of the present invention, the value of X2 / X1 can be any value between 1.2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 1.2-20. Optionally, 1.2 ≤ X2 / X1 ≤ 4. Optionally, 4 ≤ X2 / X1 ≤ 10. Optionally, 4 ≤ X2 / X1 ≤ 20.

[0033] In one embodiment of the present invention, the mass content of element M in the central region of the grain is x1, where x1 is 10ppm to 400ppm. Specifically, x1 can be 10ppm, 20ppm, 50ppm, 80ppm, 100ppm, 120ppm, 150ppm, 180ppm, 200ppm, 250ppm, 280ppm, 300ppm, 320ppm, 350ppm, or 400ppm, etc., or other values ​​within the above range, which are not limited here. The value of x1 is within the range described above, which stabilizes the crystal structure without affecting the capacity of the cathode material; if the content is too high, it will occupy more transition metal or lithium ion sites, thereby affecting the normal charge and discharge performance.

[0034] In one embodiment of the present invention, the mass content of element M in the surface region of the grain is x2, wherein x2 is 10ppm to 400ppm. Specifically, x2 can be 10ppm, 20ppm, 50ppm, 80ppm, 100ppm, 120ppm, 150ppm, 180ppm, 200ppm, 250ppm, 280ppm, 300ppm, 320ppm, 350ppm, or 400ppm, etc., and of course, it can also be other values ​​within the above range, which are not limited here. The value of x2 is within the range described above, which can stabilize the crystal structure without affecting the capacity of the cathode material; if the content is too high, it will occupy more transition metal or lithium ion sites, thereby affecting the normal charge and discharge performance.

[0035] In one embodiment of the present invention, the mass content of element M in the cathode material is 10 ppm to 400 ppm. Specifically, the content of element M in the cathode material can be 10 ppm, 20 ppm, 50 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 180 ppm, 200 ppm, 250 ppm, 280 ppm, 300 ppm, 320 ppm, 350 ppm, or 400 ppm, etc., and of course, other values ​​within the above range are also possible, without limitation. When the content of element M is too low, the doping effect cannot be achieved; when the content of element M is too high, the excessive M element in the grains will lead to a large change in unit cell volume, resulting in decreased structural stability and negatively impacting the long-term electrochemical performance of the battery. When the content of element M is controlled within the range of 10 ppm to 400 ppm, fewer cracks are generated during long-term cycling, resulting in better cycle stability.

[0036] In one embodiment of the present invention, the content of element N2 in the positive electrode material is 0 ppm to 5000 ppm. Specifically, the content of element N2 in the positive electrode material can be 0 ppm, 5 ppm, 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2400 ppm, 2800 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 4800 ppm, or 5000 ppm, etc., or other values ​​within the above range, which are not limited here. When the concentration of element N2 is within the above range, it can stabilize the crystal structure, improve the ionic conductivity, and delay the reaction between the positive electrode material and the electrolyte.

[0037] In one embodiment of the present invention, the lattice strain ε of the cathode material is less than 0.1%. Specifically, the lattice strain ε of the cathode material can be 0.095%, 0.09%, 0.05%, 0.01%, 0.005%, 0%, -0.01%, -0.05%, -0.08%, -0.10%, or -0.15%, etc., or other values ​​within the above range, which are not limited here. By controlling the lattice strain ε to within 0.1%, the occurrence of microcracks inside the particles can be reduced, making the cathode material less prone to cracking and failure during cycling.

[0038] In one embodiment of the present invention, the specific surface area S of the positive electrode material is 0.4 m². 2 / g~0.9m 2 / g. Specifically, the specific surface area S of the cathode material can be 0.4m². 2 / g, 0.45m 2 / g, 0.50m 2 / g, 0.55m 2 / g, 0.58m 2 / g, 0.60m 2 / g, 0.70m 2 / g, 0.75m 2 / g, 0.80m 2 / g, 0.85m 2 / g or 0.9m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Studies have found that the specific surface area S of the cathode material is greater than 0.9 m². 2 At a concentration of / g, there is a high amount of particulate powder, which easily reacts with the electrolyte during charging and discharging, leading to gas generation; while when the specific surface area S of the positive electrode material is less than 0.4m², the concentration of particulate powder is higher. 2 At a particle size of / g, the particle size is relatively large. The large particle size leads to an excessively long lithium-ion transport channel and relatively high internal resistance, which affects the kinetic process and the rate performance of the cathode material.

[0039] In one embodiment of the present invention, the tap density ρ1 of the positive electrode material is greater than 2.0 g / cm³. 3 The compaction density ρ2 of the positive electrode material is ≥ 2.8 g / cm³. 3 Specifically, the tap density ρ1 of the positive electrode material can be 2.10 g / cm³. 3 2.12 g / cm 3 2.18 g / cm 3 2.20g / cm 3 2.22 g / cm 3 2.24 g / cm 3 2.30g / cm 3 2.32 g / cm 3 2.35g / cm 3 Or 2.40 g / cm 3 Of course, it can also be other values ​​within the above range, and is not limited here. The compaction density ρ2 of the positive electrode material can be 2.80 g / cm³. 3 2.90g / cm 3 3.00g / cm 3 3.10 g / cm 3 3.15g / cm 3 3.18 g / cm 3 3.20g / cm 3 3.22g / cm 3 3.25g / cm 3 Or 3.30g / cm 3 Of course, it can also be other values ​​within the above range, and is not limited here. Cathode materials with higher tap density and compaction density have higher electrode compaction density during the electrode fabrication process, and can achieve higher capacity.

[0040] In one embodiment of the present invention, the volumetric particle size distribution width (Span) of the positive electrode material satisfies: 1.5 ≥ Span value ≥ 1.0. Specifically, the Span value can be 1.0, 1.15, 1.18, 1.19, 1.20, 1.22, 1.24, 1.30, 1.35, 1.40, 1.45, or 1.50, etc., and of course, other values ​​within the above range are also possible and are not limited here. The positive electrode material's volumetric particle size distribution satisfying the above range allows for a wider overall volumetric distribution of the positive electrode material particles, facilitating higher electrode compaction and thus improving battery capacity.

[0041] In one embodiment of the present invention, the cathode material is a single-crystal material, comprising at least one grain with the same orientation, the average grain size being 1 μm to 5 μm. The cathode material contains single grains with the same orientation, wherein the average grain size of the single grain is 1 μm to 5 μm. Specifically, the average grain size of the single grain is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within the range of any two of the above values, without limitation. The primary particles of the cathode material have the same orientation, and the average grain size of the primary particles is 1 μm to 5 μm. Specifically, the average grain size of the primary particles is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within the range of any two of the above values, without limitation. The cathode material particles of this application have single grains with the same orientation. Because single crystals have a more stable structure, a more uniform bulk composition distribution, and better particle strength than polycrystalline materials, the material can significantly reduce particle cracking during electrode pressing, thereby improving electrode compaction density and volumetric energy density.

[0042] It is important to note that the difference between single-crystal cathode materials and polycrystalline cathode materials (i.e., polycrystalline secondary particles) lies in the fact that the smallest particles in polycrystalline secondary particles are formed by the agglomeration of nanoscale primary particles. In contrast, the smallest particles in single-crystal cathode materials are typically micrometer-sized single primary particles. Generally, in addition to EBSD testing, scanning electron microscopy (SEM) and other characterization methods can be used to determine whether the obtained cathode product is a single-crystal material. For example, for single-crystal cathode materials, SEM can characterize the morphology of single-crystal particles, showing that they are generally regular or irregular spherical in shape, with no significant particle agglomeration. EBSD can also characterize the orientation of single-crystal cathode materials. EBSD observation shows that at least one grain has the same color, indicating that at least one grain has the same orientation; grains with the same orientation are single crystals. It is important to clarify that the "single-crystal cathode material" known to those skilled in the art is not a "single crystal" in the strict crystallographic sense. In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations such as impurities, strain, and crystal defects, ideal single crystals are very rare and difficult to produce in the laboratory. Therefore, the single-crystal cathode materials known in the art are actually more "single-crystal-like" cathode materials, which only differ from polycrystalline materials composed of numerous small primary particles in size, exhibiting a large particle size similar to single crystals.

[0043] In one embodiment of the present invention, the grain comprises a matrix and a coating, wherein the coating covers at least a portion of the surface of the matrix. The coating is selected from at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3. Coating can improve the chemical stability of the matrix material surface and enhance the electrochemical performance of the cathode material.

[0044] It should be noted that the positive electrode material provided by the present invention has two types of grains: one type is where the grains are the matrix and there is no coating on the matrix; the other type is where the grains include the matrix and the coating on the matrix.

[0045] It should be noted that the grains include a matrix and a coating, and the coating at least partially covers a portion of the surface of the matrix. The grains can be characterized by transmission scanning electron microscopy (TEM). The presence of a clear layered structure between the matrix and the coating, or the formation of a granular structure of the coating on the surface of the matrix, indicates that the surface of the matrix is ​​coated with the coating.

[0046] It should be noted that the coating material is selected from at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3. In this application, any one of the above elements is characterized by XPS high-resolution scanning to obtain a fine spectrum. Based on the analysis of the fine spectrum, the valence state of the element can be obtained, thus indicating that the coating layer of the cathode material contains at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3.

[0047] In some embodiments, the grain includes a matrix and a coating covering at least a portion of the surface of the matrix, the coating including at least one element selected from Zr, Ti, Al, Co, W, Ce, and Y.

[0048] Secondly, the present invention provides a method for preparing the cathode material described herein, comprising the following steps:

[0049] S1: A precursor solution is prepared by mixing a salt solution containing Ni, Co, and N1 with a salt solution containing element M; wherein the element N1 is selected from at least one of Mn or Al.

[0050] S2: The precursor solution is prepared into an oxide precursor by spray pyrolysis treatment, wherein the spray pyrolysis treatment includes spray treatment and annealing treatment, and the atomization airflow rate of the spray treatment is 100m³. 3 / h~300m 3 / h, atomization pressure is 400Kpa~700Kpa, pyrolysis temperature is 400℃~1000℃, and the annealing treatment temperature is 500℃~1200℃;

[0051] S3: The oxide precursor is mixed with a lithium source and a metal oxide containing element N2 and sintered to obtain a cathode material; the element N2 is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce and Y.

[0052] The method for preparing the cathode material provided by this invention can use recycled cathode material or pure metal salts of Ni, Co, and Ni as raw materials.

[0053] If recycled ternary cathode materials are used, the composition of the recycled ternary cathode materials needs to be analyzed first. This process is to confirm the content ratio of the main elements in the recycled material and the types and proportions of impurity elements present. Then, the cathode material with confirmed composition is mixed with pure Ni / Co / N1 metal salts according to the final target Ni:Co:N1 molar ratio to prepare a nitrate solution.

[0054] In one embodiment of the present invention, in step S1, the molar ratio of Ni, Co, and N1 in the salt solution containing Ni, Co, and N1 is (55-70):(10-12):(20-33). Specifically, the molar ratio of Ni, Co, and N1 in the nitrate solution containing Ni, Co, and N1 can be 55:12:33, 70:12:33, 55:10:20, 70:10:20, 60:10:30, 65:12:33, 55:11:30, 70:11:30, 60:12:33, or 68:11:28, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0055] In one embodiment of the present invention, in step S1, the N1 element can be Mn and / or Al.

[0056] A precursor solution is prepared by adding a salt solution of element M to a nitrate solution in the target proportion. If the recovered ternary cathode material contains the target element M, the concentration of element M to be added can be adjusted to ensure that the final concentration is the target concentration.

[0057] In one embodiment of the present invention, in step S1, the mass percentage concentration of element M in the precursor solution is 0.01% to 0.06%. Specifically, the mass percentage concentration of element M in the precursor solution can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%, etc., and of course, other values ​​within the above range are also possible, which are not limited here. By controlling the mass percentage concentration of element M in the precursor solution within the above range, the content of element M in the obtained cathode material can meet the range of 10ppm to 400ppm.

[0058] In one embodiment of the present invention, in step S1, the salt of element M includes at least one of the following: chloride, sulfate, sulfite, nitrate, carbonate, and phosphate of element M. Element M is selected from at least one element in Group IA or Group IIA of the periodic table. For example, element M can be at least one of Na, K, Mg, Ca, Sr, Ba, Rb, and Cs.

[0059] In one embodiment of the present invention, the total concentration of Ni, Co, Ni, and M in the precursor solution is 2 mol / L to 8 mol / L. Specifically, the total concentration of Ni, Co, Ni, and M in the precursor solution can be 2.0 mol / L, 2.5 mol / L, 2.8 mol / L, 3.0 mol / L, 4.0 mol / L, 4.5 mol / L, 5.0 mol / L, 5.5 mol / L, 6.0 mol / L, 6.4 mol / L, 6.8 mol / L, 7.0 mol / L, or 8.0 mol / L, or other values ​​within the above range, which are not limited here. When the total concentration of Ni, Co, Ni, and M in the precursor solution is within the above range, the solid content of the formed spray droplets is moderate, and the solid phase, as a nucleation site, is conducive to the rapid solidification and nucleation of droplets.

[0060] In one embodiment of the present invention, the spray pyrolysis includes spray treatment and annealing treatment. The atomizing airflow rate of the spray treatment is 100 m³ / h. 3 / h~300m 3 The atomization pressure is 400 kPa to 700 kPa, and the pyrolysis temperature is 400°C to 1000°C. Specifically, the atomization airflow rate for spray treatment can be 100 m³ / h. 3 / h, 120m 3 / h, 150m 3 / h, 180m 3 / h、200m 3 / h、240m 3 / h、280m 3 / h or 300m 3 / h, or other values ​​within the above range, are not limited here. The atomization pressure can be 400 kPa, 420 kPa, 450 kPa, 500 kPa, 540 kPa, 580 kPa, 600 kPa, 650 kPa, or 700 kPa, or other values ​​within the above range, are not limited here. The pyrolysis temperature can be 400℃, 450℃, 500℃, 600℃, 650℃, 700℃, 800℃, 900℃, or 1000℃, or other values ​​within the above range, are not limited here. By controlling the atomization airflow, atomization pressure, and pyrolysis temperature within the above ranges, and by adjusting the appropriate atomization airflow, atomization pressure, and pyrolysis temperature, the time for the precursor solution to form dehydrated particles can be controlled, promoting the enrichment of element M in the surface region of the dehydrated particles.

[0061] In one embodiment of the present invention, the annealing temperature is 500℃ to 1200℃. Specifically, the annealing temperature can be 500℃, 600℃, 650℃, 700℃, 800℃, 850℃, 900℃, 960℃, 1000℃, 1050℃, 1100℃, 1140℃, or 1200℃, or other values ​​within the above range, which are not limited here. Higher annealing temperatures can cause the dehydrated particles to form oxide precursors.

[0062] The method for preparing the cathode material provided by this invention can effectively regulate the difference in the internal and external distribution of element M by controlling the spray treatment and annealing treatment during the spray pyrolysis process, so that the concentration X1 of element M in the central region and the concentration X2 in the surface region of element M in the obtained cathode material grains satisfy: 1.2≤X2 / X1≤20.

[0063] In one embodiment of the present invention, in step S3, the oxide precursor is first pulverized to a D50 of 2.0 μm to 4.0 μm, and then used for mixing. Specifically, the oxide precursor can be pulverized to a D50 of 2.0 μm, 2.2 μm, 2.5 μm, 3.0 μm, 3.5 μm, 3.8 μm, or 4.0 μm, or other values ​​within the above range, which are not limited here. Pulverizing the oxide precursor to a D50 of 2.0 μm to 4.0 μm before mixing results in less cathode material powder and more rounded grains.

[0064] In one embodiment of the present invention, in step S3, the lithium source can be selected from any one or more of lithium carbonate, lithium nitrate, and lithium hydroxide.

[0065] In one embodiment of the present invention, in step S3, the metal oxide containing element N2 is selected from any one or more of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3; preferably, the metal oxide containing element N2 is CeO2 and / or WO3, and more preferably, the metal oxide containing element N2 is CeO2.

[0066] In one embodiment of the present invention, in step S3, the oxide precursor, lithium source, and metal oxide containing element N2 are mixed in a mass ratio of 1:(0.4-0.8):(0.003-0.006). Specifically, the oxide precursor, lithium source, and metal oxide containing element N2 are mixed in mass ratios of 1:0.4:0.003, 1:0.5:0.004, 1:0.6:0.006, 1:0.5:0.003, 1:0.5:0.005, 1:0.8:0.003, 1:0.8:0.006, 1:0.4:0.006, or 1:0.5:0.004. Other values ​​within the above range are also possible and are not limited here. By limiting the mass ratio of the oxide precursor, lithium source, and metal oxide containing element N2, a cathode material with the chemical formula described in this invention can be obtained.

[0067] In one embodiment of the present invention, in step S3, the heating rate of the sintering heating section is controlled at 0.5℃ / min to 3℃ / min, and the holding time for sintering is 8h to 16h. Specifically, the heating rate of the sintering heating section can be controlled at 0.5℃ / min, 1.0℃ / min, 1.2℃ / min, 1.5℃ / min, 1.8℃ / min, 2.0℃ / min, 2.5℃ / min, or 3.0℃ / min, or other values ​​within the above range, which are not limited here. Controlling the heating rate within the above range allows for more complete lithium intercalation and more complete grain nucleation through slow heating. Specifically, the holding time for sintering can be 8h, 8.5h, 9.0h, 10h, 10.5h, 11h, 12h, 13h, 14h, 15h, or 16h, or other values ​​within the above range, which are not limited here. When the sintering holding time is within the above-mentioned range, grain growth is more complete, and less grain agglomeration occurs in the obtained cathode material. As one embodiment of the invention, the sintered material is subjected to airflow milling followed by coating treatment, and the median particle size distribution (D50) of the milled sintered material is controlled to be 3.0 μm to 5.0 μm. Specifically, the matrix can be milled to a D50 of 3.0 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.5 μm, or 5.0 μm, or other values ​​within the above range, which are not limited here. The particle size D50 of the matrix airflow milling is controlled within the above-mentioned range, which corresponds to the particle size D50 range of the oxide precursor, ensuring a good milling effect.

[0068] As one embodiment of the present invention, the coating agent used in the coating treatment is selected from at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3.

[0069] Thirdly, the present invention also provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode material described in the present invention or the positive electrode material obtained by the preparation method described in the present invention.

[0070] As one embodiment of this application, a secondary battery is provided, including a casing, an electrode assembly, and an electrolyte / electrolyte. Both the electrode assembly and the electrolyte / electrolyte are located within the casing. The casing can be a packaging bag encapsulated with an encapsulating film (such as an aluminum-plastic film), for example, a pouch battery. In other embodiments, the secondary battery can also be a steel-cased battery, an aluminum-cased battery, etc.

[0071] Figure 5 shows a schematic diagram of a battery in a discharged state, i.e., during operation. As shown, the electrode assembly includes a positive electrode 110, a negative electrode 120, and a separator 130, with the separator disposed between the positive and negative electrode sheets. The electrode assembly can be a stacked structure, formed by alternating layers of the positive electrode, separator, and negative electrode. In other embodiments, the electrode assembly can also be a wound structure, formed by winding the positive electrode, separator, and negative electrode after they have been stacked in sequence.

[0072] Positive electrode tablets

[0073] The positive electrode 110 includes a positive current collector 111 and a positive active layer 112 disposed on at least one surface of the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and polymer substrate. The positive active layer contains a positive active material, including the positive electrode material provided by this invention or the positive electrode material obtained by the preparation method of this invention.

[0074] Negative electrode film

[0075] The negative electrode 120 includes a negative electrode current collector 121 and a negative electrode active material layer 122 disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collectors, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode active material layer includes a negative electrode material.

[0076] During battery operation, i.e., when the battery is in a discharged state, metal ions 140 (e.g., lithium ions) in the negative electrode are released from the lattice of the negative electrode material, pass through the electrolyte / electrolyte through the separator 130, and are inserted into the lattice of the positive electrode material. Conversely, when the battery is charged by applying an external circuit, oxidation of the positive electrode material causes metal ions (e.g., lithium ions) in the positive electrode to be released from the lattice of the positive electrode material, pass through the electrolyte / electrolyte through the separator, and move to the negative electrode; simultaneously, a reduction reaction occurs in the negative electrode material, causing metal ions to be inserted into the lattice of the negative electrode material. With the repeated movement of metal ions between the positive and negative electrodes, the battery can achieve the discharge and charge process in thousands of cycles.

[0077] In some embodiments, the silicon-based material in the negative electrode material may include at least one of amorphous silicon, crystalline silicon, silicon oxide, and silicate.

[0078] In some embodiments, the silicon-based material includes silicon oxide, which includes silicon and oxygen elements in an atomic ratio of 0 to 2, excluding 0.

[0079] In some embodiments, the silicon-based material includes silicon oxide, which has the general chemical formula SiOx, where 0 < x ≤ 2. Specifically, SiOx can be SiO 0.5 SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 The terms are not limited here. Silicon oxides can be represented by the general formula SiOx (0 < x ≤ 2). It can be a material formed by silicon dispersed in SiO2; or it can be a material with tetrahedral structural units, where silicon atoms are located at the center of the tetrahedral structural units, and oxygen atoms and / or silicon atoms are located at the four vertices of the tetrahedral structural units.

[0080] In some embodiments, the graphite material in the negative electrode material may include at least one of natural graphite, artificial graphite, expanded graphite, and graphite oxide.

[0081] In some embodiments, the negative electrode material includes a carbon material, which includes at least one of amorphous carbon and graphitized carbon.

[0082] Specific embodiments and comparative examples

[0083] Example 1

[0084] This embodiment provides a cathode material, the preparation process of which is as follows:

[0085] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 55:12:33. Add K chloride solution to nitrate solution to prepare precursor solution. The mass ratio of K element in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and K in precursor solution is 5 mol / L.

[0086] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 500℃, and annealing temperature is 1000℃;

[0087] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.24 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0088] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0089] Example 2

[0090] This embodiment provides a cathode material, the preparation process of which is as follows:

[0091] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 60:10:30. Add Mg sulfate solution to nitrate solution to prepare precursor solution. The mass ratio of Mg in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and Mg in precursor solution is 5 mol / L.

[0092] (2) Spray pyrolysis involves spraying the precursor solution and then annealing it to produce an oxide precursor. The atomizing airflow rate for the spray treatment is 220 m³ / h. 3 / h, atomization pressure is 500Kpa, pyrolysis temperature is 600℃, and annealing temperature is 900℃;

[0093] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.16 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 950 °C in an oxygen atmosphere. The heating rate of the sintering heating section was controlled at 3 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0094] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.5 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0095] Example 3

[0096] This embodiment provides a cathode material, the preparation process of which is as follows:

[0097] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Ca chloride solution to nitrate solution to prepare precursor solution. The mass ratio of Ca in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and Ca in precursor solution is 5 mol / L.

[0098] (2) Spray pyrolysis involves spraying the precursor solution and then annealing it to produce an oxide precursor. The atomizing airflow rate for the spray treatment is 180 m³ / h. 3 / h, atomization pressure is 600Kpa, pyrolysis temperature is 800℃, and annealing temperature is 1100℃;

[0099] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.36 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 1 °C / min, and the holding time of sintering was 8 h to obtain the sintered product.

[0100] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.8 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0101] Example 4

[0102] This embodiment provides a cathode material, the preparation process of which is as follows:

[0103] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Ba chloride solution to nitrate solution to prepare precursor solution. The mass content of Ba element in precursor solution is 0.01%, and the total concentration of Ni, Co, Mn and Ba in precursor solution is 5 mol / L.

[0104] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 500Kpa, pyrolysis temperature is 800℃, and annealing temperature is 1000℃;

[0105] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.05 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 1 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0106] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 3.5 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0107] Example 5

[0108] This embodiment provides a cathode material, the preparation process of which is as follows:

[0109] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Sr nitrate solution to the nitrate solution to prepare a precursor solution. The mass content of Sr element in the precursor solution is 0.01%, and the total concentration of Ni, Co, Mn and Sr in the precursor solution is 5 mol / L.

[0110] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate for the spray treatment is 150 m³ / h. 3 / h, atomization pressure is 650Kpa, pyrolysis temperature is 700℃, and annealing temperature is 800℃;

[0111] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.50 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of sintering was 8 h to obtain the sintered product.

[0112] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0113] Example 6

[0114] This embodiment provides a cathode material, the preparation process of which is as follows:

[0115] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add chloride solutions of K and Mg to the nitrate solutions to prepare precursor solutions. The mass ratio of K and Mg in the precursor solutions is 0.02%, and the total concentration of Ni, Co, Mn, K and Mg in the precursor solutions is 5 mol / L.

[0116] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 900℃, and annealing temperature is 1000℃;

[0117] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.28 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 3 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0118] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.0 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0119] Example 7

[0120] This embodiment provides a cathode material, the preparation process of which is as follows:

[0121] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add sulfate solution of K and nitrate solution of Ca to the nitrate solution to prepare precursor solutions. The mass ratio of K and Ca in the precursor solutions is 0.02% and the total concentration of Ni, Co, Mn, K and Ca in the precursor solutions is 5 mol / L.

[0122] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 240 m³ / h. 3 / h, atomization pressure is 450Kpa, pyrolysis temperature is 600℃, and annealing temperature is 950℃;

[0123] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 2.96 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0124] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.7 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0125] Example 8

[0126] This embodiment provides a cathode material, the preparation process of which is as follows:

[0127] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add chloride solutions of K and Ba to the nitrate solutions to prepare precursor solutions. The mass ratio of K and Ba in the precursor solutions is 0.02%, and the total concentration of Ni, Co, Mn, K and Ba in the precursor solutions is 5 mol / L.

[0128] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 600Kpa, pyrolysis temperature is 700℃, and annealing temperature is 1000℃;

[0129] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.10 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 1.5 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0130] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 3.7 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0131] Example 9

[0132] This embodiment provides a cathode material, the preparation process of which is as follows:

[0133] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add K chloride solution and Sr chloride solution to the nitrate solution to prepare precursor solutions. The mass ratio of K and Sr in the precursor solutions is 0.02%, and the total concentration of Ni, Co, Mn, K and Sr in the precursor solutions is 5 mol / L.

[0134] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate for the spray treatment is 180 m³ / h. 3 / h, atomization pressure is 500Kpa, pyrolysis temperature is 650℃, and annealing temperature is 1000℃;

[0135] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.25 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 0.5 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0136] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.3 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0137] Example 10

[0138] This embodiment provides a cathode material, the preparation process of which is as follows:

[0139] (1) Take metal salts of Ni, Co and Mn and prepare chloride salt solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add chloride salt solutions of Mg and Ca to the chloride salt solutions to prepare precursor solutions. The mass ratio of Mg and Ca in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Mg and Ca in the precursor solutions is 5 mol / L.

[0140] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 580Kpa, pyrolysis temperature is 700℃, and annealing temperature is 1000℃;

[0141] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.75 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2, and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 1.5 °C / min, and the holding time of sintering was 8 h to obtain the sintered product.

[0142] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.8 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0143] Example 11

[0144] This embodiment provides a cathode material, the preparation process of which is as follows:

[0145] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add nitrate solutions of Mg and Ba to the nitrate solutions to prepare precursor solutions. The mass ratio of Mg and Ba in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Mg and Ba in the precursor solutions is 5 mol / L.

[0146] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate for the spray treatment is 150 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 800℃, and annealing temperature is 1000℃;

[0147] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.21 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 1 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0148] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.1 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0149] Example 12

[0150] This embodiment provides a cathode material, the preparation process of which is as follows:

[0151] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Mg chloride solution and Sr chloride solution to the nitrate solution to prepare precursor solutions. The mass ratio of Mg and Sr in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Mg and Sr in the precursor solutions is 5 mol / L.

[0152] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 120 m³ / h. 3 / h, atomization pressure is 700Kpa, pyrolysis temperature is 900℃, and annealing temperature is 1000℃;

[0153] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.19 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 3 °C / min, and the holding time of sintering was 8 h to obtain the sintered product.

[0154] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0155] Example 13

[0156] This embodiment provides a cathode material, the preparation process of which is as follows:

[0157] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Ca chloride solution and Ba chloride solution to the nitrate solution to prepare precursor solutions. The mass ratio of Ca and Ba elements in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Ca and Ba in the precursor solutions is 5 mol / L.

[0158] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 600Kpa, pyrolysis temperature is 600℃, and annealing temperature is 1000℃;

[0159] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.38 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 3 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0160] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0161] Example 14

[0162] This embodiment provides a cathode material, the preparation process of which is as follows:

[0163] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Ca nitrate solution and Sr nitrate solution to the nitrate solution to prepare precursor solutions. The mass ratio of Ca and Sr in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Ca and Sr in the precursor solutions is 5 mol / L.

[0164] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 600Kpa, pyrolysis temperature is 1000℃, and annealing temperature is 1000℃;

[0165] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.48 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of sintering was 8 h to obtain the sintered product.

[0166] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.4 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0167] Example 15

[0168] This embodiment provides a cathode material, the preparation process of which is as follows:

[0169] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add Ba chloride solution and Sr chloride solution to the nitrate solution to prepare precursor solutions. The mass ratio of Ba and Sr in the precursor solutions is 0.03% and the total concentration of Ni, Co, Mn, Ba and Sr in the precursor solutions is 5 mol / L.

[0170] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 600℃, and annealing temperature is 1200℃;

[0171] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.52 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0172] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.7 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0173] Example 16

[0174] This embodiment provides a cathode material, the preparation process of which is as follows:

[0175] (1) Take metal salts of Ni, Co and Al and prepare nitrate solution according to the molar ratio of Ni:Co:Al = 55:12:33. Add K chloride solution to nitrate solution to prepare precursor solution. The mass ratio of K element in precursor solution is 0.01% and the total concentration of Ni, Co, Al and K in precursor solution is 5 mol / L.

[0176] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 500℃, and annealing temperature is 1000℃;

[0177] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.19 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0178] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.4 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0179] Example 17

[0180] This embodiment provides a cathode material, the preparation process of which is as follows:

[0181] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 55:12:33. Add K chloride solution to nitrate solution to prepare precursor solution. The mass ratio of K element in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and K in precursor solution is 5 mol / L.

[0182] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 500℃, and annealing temperature is 1000℃;

[0183] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.20 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0184] Example 18

[0185] The difference between this embodiment and Embodiment 1 is that the Ni, Co, and Mn metal salts are prepared into a nitrate solution according to a molar ratio of Ni:Co:Mn = 70:10:20, and the mass percentage of K in the precursor solution is 0.04%; the atomization airflow rate of the spray treatment is 100 m³ / s. 3 The atomization pressure was 700 kPa, the pyrolysis temperature was 400 °C, and the annealing temperature was 1200 °C. Other steps were the same as in Example 1.

[0186] Example 19

[0187] The difference between this embodiment and Embodiment 1 is that the Ni, Co, and Mn metal salts are prepared as nitrate solutions in a molar ratio of Ni:Co:Mn = 80:10:10; and the atomizing airflow rate of the spray treatment is 300 m³ / s. 3 The atomization pressure is 400 kPa, the pyrolysis temperature is 1000 °C, and the annealing temperature is 500 °C. Other steps are the same as in Example 1.

[0188] Example 20

[0189] The difference between this embodiment and Embodiment 1 is that the metal salts of Ni, Co, and Mn are prepared into nitrate solutions according to a molar ratio of Ni:Co:Mn = 90:5:5; the other steps are the same as in Embodiment 1.

[0190] Comparative Example 1

[0191] This comparative example provides a cathode material, which is obtained by the following preparation method:

[0192] (1) A hydroxide precursor with a molar ratio of Ni:Co:Mn = 55:12:33 was synthesized by coprecipitation method;

[0193] (2) The oxide precursor was pulverized and the pulverization D50 was controlled to be 3.24 μm. 400 g of pulverized oxide precursor, 186.72 g of lithium carbonate, and 1.8 g of CeO2 were uniformly mixed and sintered at 960 °C for 8 h in a compressed air atmosphere to obtain the sintered product.

[0194] The obtained sintered material was pulverized to a particle size D50 of 4.2 μm to obtain pulverized material; 300 g of pulverized material was mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain sintered material; the sintered material was demagnetized by sieving to obtain positive electrode material.

[0195] Comparative Example 2

[0196] This comparative example provides a cathode material, which is obtained by the following preparation method:

[0197] (1) A hydroxide precursor with a molar ratio of Ni:Co:Mn = 55:12:33 was synthesized by coprecipitation method;

[0198] (2) The oxide precursor was pulverized and the pulverization D50 was controlled to be 3.16 μm. 400 g of pulverized oxide precursor was mixed with 186.72 g of lithium carbonate, 1.8 g of CeO2, 0.1 g of MgO and 0.1 g of KOH and sintered at 960 °C for 8 h in a compressed air atmosphere to obtain sintered material.

[0199] The obtained sintered material was pulverized to a particle size D50 of 4.5 μm to obtain pulverized material; 300 g of pulverized material was mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain sintered material; the sintered material was demagnetized by sieving to obtain positive electrode material.

[0200] Comparative Example 3

[0201] This comparative example provides a cathode material, which is obtained by the following preparation method:

[0202] (1) Take pure metal salts of Ni, Co and Mn, prepare a ternary nitrate solution according to the molar ratio of Ni:Co:Mn = 55:12:33, and prepare oxide precursors by spray pyrolysis;

[0203] (2) The oxide precursor was pulverized and the pulverization D50 was controlled to be 3.48 μm. 400 g of pulverized oxide precursor, 186.72 g of lithium carbonate, and 1.8 g of CeO2 were mixed evenly and sintered at 960 °C for 8 h in a compressed air atmosphere to obtain the sintered product.

[0204] The obtained sintered material was pulverized to a particle size D50 of 4.1 μm to obtain pulverized material; 300 g of pulverized material was mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain sintered material; the sintered material was demagnetized by sieving to obtain positive electrode material.

[0205] Comparative Example 4

[0206] 1) Take metal salts of Ni, Co, and Mn and prepare nitrate solutions according to the molar ratio of Ni:Co:Mn = 55:12:33. Add K chloride solution to the nitrate solution to prepare a precursor solution. The mass content of K element in the precursor solution is 0.01%, and the total concentration of Ni, Co, Mn, and K in the precursor solution is 5 mol / L.

[0207] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 80 m³ / s. 3 / h, atomization pressure is 900Kpa, pyrolysis temperature is 1000℃, and annealing temperature is 700℃;

[0208] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.24 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 and sintered at 960 °C in a compressed air atmosphere. The heating rate of the sintering heating section was controlled at 2 °C / min, and the holding time of the sintering was 8 h to obtain the sintered product.

[0209] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0210] Test method:

[0211] The method for testing the average concentration X1 of element M in the central region and the average concentration X2 of element M in the surface region of the cathode material grain is as follows: A cross-section sample is prepared using a Hitachi ion cutter (IM5000). A suitable field of view is selected using a Hitachi S4800 scanning electron microscope, and then EDS is used to perform a line scan or spot scan of the grain cross-section within a 5k field of view. For example, a spot scan can be used to measure the content of element M at 10 locations (generally at least 5 points) in the central region of the grain cross-section. The summation and averaging of the M content yields the number of atoms in the central region of the grain. Similarly, the content of element M at 10 locations in the surface region of the grain cross-section is measured, and the summation and averaging of the M content yields the number of atoms in the surface region of the grain. Then, randomly select 10 particles and characterize the number of atoms in the central region and the number of atoms in the surface region of each particle according to the above method. Sum and average the number of atoms in the central region of each of the 10 particles to obtain the average number of atoms of element M in the central region X1 (dimensionless). Sum and average the number of atoms in the surface region of each of the 10 particles to obtain the average number of atoms of element M in the surface region X2 (dimensionless).

[0212] As shown in Figure 1, in the cross-sectional view of the grain, the radius of the grain is L. The region from the center of the grain to a distance L / 2 from the center is the central region, and the region from L / 2 to the grain surface is the surface region. When the cathode material contains two or more elements M, the X1 and X2 values ​​of each element M are measured separately, and the corresponding X2 / X1 values ​​are calculated. It should be further noted that for irregularly shaped particles, such as elongated particles, as shown in Figure 7, the center of the circumscribed circle is the center of the grain, the diameter L of the grain is the diameter where the circumscribed circle intersects the grain edge, the portion of the grain covered by the surface region of the circumscribed circle is the surface region, and the region covered by the central region of the circumscribed circle is the central region.

[0213] For point scanning and line scanning, please refer to Figure 6 for the following explanation:

[0214] Point scanning: Select 5-10 points in the central area (inside the black circle in Figure 6) for EDS measurement, and take the average value to obtain the X1 value; select 5-10 points in the surface area (outside the black circle in Figure 6) for EDS measurement, and take the average value to obtain the X2 value.

[0215] Line scanning: Randomly select at least three line positions in the central area (i.e., inside the black circle in Figure 6) for line scanning, and take the average value after measurement to obtain the X1 value; Randomly select at least three line positions in the surface area (i.e., outside the black circle in Figure 6) for line scanning, and take the average value after measurement to obtain the X2 value. In actual testing, spot scanning and line scanning can also be used in combination.

[0216] Test method for the content of each element in the cathode material: Take 0.3g of the cathode material sample to be tested, dissolve it in aqua regia, cool and dilute to a volume of 100ml to prepare the test stock solution; take 1mL of the test stock solution, test the content of elements M and N, dilute it 100 times and then test the content of the main elements Li, Ni, Co, Mn and Al, and record it as ICP(M). All determinations were performed using an Agilent 5110 ICP-OES detection instrument.

[0217] Calculation of the elemental mass content x1 in the central region: x1(ppm)=ICP(M)*X1 / (X1+X2); x1 is the number of atoms in the central region obtained by EDS characterization, and x2 is the number of atoms in the surface region obtained by EDS characterization.

[0218] The calculation of the elemental mass content x2 in the surface region is as follows: x2(ppm)=ICP(M)*X2 / (X1+X2); X1 is the number of atoms in the central region obtained by EDS characterization, and X2 is the number of atoms in the surface region obtained by EDS characterization.

[0219] The method for measuring the microscopic strain ε was as follows: A Rigaku XRD diffractometer (Japan) was used to measure the strain within the range of 10°–70° at a rate of 1° / min and a step size of 0.005°. The XRD images were then refined using GASA with Rietveld parameters to obtain information such as the sample cell parameters and peak shape parameters. The strain magnitude was calculated using the Scherrer formula based on the obtained peak shape parameters. The volume of the unit cell after M-doping was compared with the volume of the unit cell without M-doping. If the unit cell volume decreased after M-doping, it indicated the introduction of compressive strain (represented by a negative number) within the lattice; otherwise, it indicated tensile strain. The measured strain magnitudes are shown in Table 3.

[0220] The specific surface area S was measured using a Micrometer (USA). The sample was degassed at 300℃ under vacuum for 1 hour before testing. Specifically, the total mass of the empty sample tube was weighed as m1; 3g (±0.005g) of sample was added to the sample tube; the sample tube was then degassed under vacuum at 300℃ for 1 hour, and after cooling, the total mass of the sample tube and sample was weighed as m2; the sample mass m = m2 - m1. The sample tube was placed in liquid nitrogen, and the nitrogen adsorption capacity V was measured at six relative pressures P / P0 to obtain adsorption isotherms; where P / P0 was set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. The monolayer saturated adsorption capacity Vm was obtained from the adsorption isotherms, and the specific surface area of ​​the cathode material was calculated based on Vm.

[0221] Test method for tap density ρ1: The tap density was tested using Dandong Baite BT-303 with a vibration rate of 3000 times / min, a vibration time of 1min, and a vibration amplitude of 3mm±0.1mm.

[0222] Test method for compacted density ρ2 of powder: The compacted density of powder is tested using a compaction density meter, with a pressure of 6t for 30s.

[0223] The volumetric particle size of the cathode material was tested using a Malvern MS 3000 laser particle size analyzer. Specifically, an appropriate amount of sample was taken, poured into pure water, and ultrasonically dispersed evenly. Then, an appropriate amount of sodium hexametaphosphate (powder: surfactant = 1g: 1 drop) was added to the dispersed sample, stirred evenly, and poured into the sample cell of the testing equipment. After waiting for 10 seconds, the sample was started by clicking "Start Sample Testing".

[0224] The formula for calculating the volumetric particle size distribution width (Span) is: Span value = (D90 - D10) / D50.

[0225] The surface morphology and particle size of the samples were observed using a Hitachi S4800 scanning electron microscope.

[0226] The electrochemical performance of the cathode materials provided in the above embodiments and comparative examples was tested using the following methods.

[0227] First, the positive electrode materials provided in each embodiment and comparative example are mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) in a mass ratio of 80:10:10. Then, NMP (N-methylpyrrolidone) is added to form a uniform slurry, which is then coated onto copper foil, dried in an oven, and rolled under a pressure of 10 MPa to form a circular electrode sheet with a diameter of 14 mm.

[0228] The CR2025 button cell is assembled into a lithium-ion battery according to industrial standards. The separator is a Cellgard separator, the electrolyte is a 1 mol / L LiPF6 solution with EC / PC / DEC solvent, and the electrode is a lithium sheet.

[0229] The entire assembly process of the lithium-ion battery is carried out in a glove box filled with argon gas, where the oxygen and moisture content are controlled to be below 0.5 ppm.

[0230] The testing conditions for lithium-ion batteries are: temperature 25℃±1℃.

[0231] Electrochemical cycle performance, capacity, and initial efficiency (first-time efficiency) of the lithium-ion battery were tested. The charge-discharge cycle voltage range was 2.8V-4.35V, the current was 0.1C (20mAh / g), and the cycle test was conducted for 50 cycles at a 0.5C charge-1C discharge rate. Capacity is expressed in mAh / g, and initial efficiency is expressed as a percentage (%).

[0232] The X2 / X1 values ​​of element M in the cathode materials provided in the above embodiments and comparative examples are shown in Table 1 below. The contents of elements M and N2 in the cathode materials provided in the above embodiments and comparative examples were also tested, and the test results are shown in Table 1.

[0233] Table 1:

[0234]

[0235] The physicochemical properties of the cathode materials provided in the above embodiments and comparative examples are shown in Table 2 below.

[0236] Table 2:

[0237] The electrochemical performance test results of the cathode materials provided in the above embodiments and comparative examples are shown in Table 3.

[0238] Table 3:

[0239] Examples 1-20 of this invention employ various elements M, controlling different X1 and X2 values ​​of element M, and different X2 / X1 values ​​within the range of 1.2 ≤ X2 / X1 ≤ 20. As can be seen from the above examples, the cathode material provided by this invention, by doping the cathode material with element M and ensuring that the concentration of element M is greater in the surface region than in the internal region of the cathode material grains, suppresses lattice expansion during charge and discharge, thus achieving the goal of improving long-term cycle performance. In Comparative Example 1, the precursor was prepared by co-precipitation without the use of element M for doping, resulting in significantly weaker capacity and initial efficiency. In Comparative Example 2, the precursor was prepared by co-precipitation and simultaneously doped with element K, resulting in an X2 / X1 value significantly less than 1.2. Furthermore, as shown in Figure 3, the K element is more uniformly distributed, with a smaller concentration difference between the surface and internal regions, leading to significantly poorer capacity and initial efficiency. In Comparative Example 3, the precursor was prepared by spray pyrolysis, but without the use of element M for doping, resulting in significantly weaker capacity and initial efficiency. In Comparative Example 4, the precursor was prepared by spray pyrolysis and doped with element M. The X2 / X1 ratio of the obtained cathode material was greater than 20, indicating that element M was enriched in the surface region of the grain. At the same time, its cycle stability was weak. The inventors speculated that the large difference in element concentration between the surface region and the inner region led to excessive compressive stress. During cycling, the grain was more likely to form cracks, thus reducing the cycle stability.

[0240] As shown in Table 1 and Figure 2, in Examples 1, 6, and 7, a significant concentration difference exists between the surface and internal regions of the K element, with X1 / X2 satisfying the value range of 1.2 ≤ X2 / X1 ≤ 20. In contrast, in Comparative Example 2, the K element distribution is more uniform, with a smaller concentration difference between the surface and internal regions. Table 3 further shows that, compared to Comparative Example 2, the lithium batteries made from the cathode materials in Examples 1, 6, and 7 exhibit significantly improved capacity and initial efficiency, as well as significantly improved electrochemical cycle performance. A comparison of the internal cracks in the cathode materials provided in Example 6 and Comparative Example 2 is also presented in Figure 4. Figure 4 shows that the grain cross-section in Comparative Example 2 reveals multiple cracks within the grains, specifically marked by white circles. This indicates that Example 6 produces fewer microcracks, which is beneficial for improving gas generation performance and long-term cycling.

[0241] As shown in Table 2, the lattice strain ε of the cathode material of this invention is less than 0.1%. Cathode materials with this strain have fewer internal microcracks and exhibit high long-term cycle capacity retention. The specific surface area S of the cathode material is less than 0.4 m². 2 / g~0.9m 2 Within the range of / g, this indicates that the surface coating of the cathode material is uniform and the discharge capacity is high. The tap density ρ1 of the cathode material is greater than 2.0 g / cm³. 3High tap density leads to higher electrode compaction and thus higher energy density. The compaction density of the cathode material ρ2 ≥ 2.8 g / cm³. 3 High powder compaction density results in higher electrode compaction and thus higher energy density. The volumetric particle size distribution width (Span value) of the cathode material should be 1.5 ≥ 1.0. Cathode materials meeting this particle size distribution exhibit higher electrode compaction and therefore higher energy density.

[0242] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that, The chemical formula of the cathode material is: Li a Ni b Co c N1 d M (1-b-c-d-e) N2 e O2, where: 0.95≤a≤1.2, 0<b≤1, 0<c≤1, 0<d≤1, 0≤e<1, and b+c+d+e<1; element M is selected from at least one element in Group IA or Group IIA of the periodic table; element N1 is selected from at least one of Mn or Al; element N2 is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, and Y. The cathode material comprises multiple grains, and the cross-section of each grain includes a central region and a surface region. The cross-section of the grain is tested by EDS, and the average concentration of element M in the central region is measured to be X1, and the average concentration of element M in the surface region is measured to be X2. X1 and X2 satisfy: 1.2≤X2 / X1≤20.

2. The cathode material according to claim 1, characterized in that, The content of element M in the cathode material is 10ppm to 400ppm; and / or, the content of element N2 in the cathode material is 0ppm to 5000ppm.

3. The cathode material according to claim 1, characterized in that, The positive electrode material includes at least one of the following characteristics (a) to (g): (a) The cathode material comprises at least one grain with the same orientation, and the average grain size is 1 μm to 5 μm; (b) The cathode material is a single crystal material.

4. The cathode material according to claim 1, characterized in that, The lattice strain ε of the cathode material is less than 0.1%.

5. The positive electrode material according to claim 1, characterized in that, The specific surface area S of the positive electrode material is 0.4 m². 2 / g~0.9m 2 / g.

6. The cathode material according to claim 1, characterized in that, The cathode material includes at least one of the following characteristics: (a) The tap density ρ1 of the cathode material is greater than 2.0 g / cm³. 3 ; (b) The compaction density ρ2 of the cathode material is ≥ 2.8 g / cm³. 3 .

7. The cathode material according to claim 1, characterized in that... The volumetric particle size distribution width Span value of the cathode material satisfies: 1.5 ≥ Span ≥ 1.

0.

8. The positive electrode material according to claim 1, characterized in that, The element M is selected from at least one of Na, K, Mg, Ca, Sr, Ba, Sr, Rb, and Cs.

9. The positive electrode material according to claim 1, characterized in that, The grain comprises a matrix and a coating, wherein the coating covers at least a portion of the surface of the matrix, and the coating comprises at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3.

10. The cathode material according to claim 1, characterized in that, The mass content of element M in the central region of the grain is x1, where x1 ranges from 10 ppm to 400 ppm.

11. The cathode material according to claim 1, characterized in that, The mass content of element M in the surface region of the grain is 10 ppm to 400 ppm for x1 and x2.

12. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (a) The value of X2 / X1 is 1.2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any value between 1.2 and 20; (b) 1.2 ≤ X2 / X1 ≤ 4; (c) 4 ≤ X2 / X1 ≤ 10; (d)4≤X2 / X1≤20.

13. The cathode material according to claim 9, characterized in that, The grain comprises a matrix and a coating covering at least a portion of the surface of the matrix, the coating comprising at least one element selected from Zr, Ti, Al, Co, W, Ce, and Y.

14. A positive electrode plate, characterized in that, The positive electrode sheet includes the positive electrode material as described in any one of claims 1 to 13.

15. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material according to any one of claims 1-13 or the positive electrode sheet according to claim 14.

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