Positive electrode material and positive electrode sheet comprising same, and battery

Abstract

The present application relates to a positive electrode material and a preparation method therefor, and a battery. The positive electrode material comprises a plurality of particles and agglomerate particles; an SEM image of the positive electrode material is obtained by means of a scanning electron microscope at a 3K magnification, wherein the total number of particles of the positive electrode material in the SEM image is N, where N≥200, and the number of agglomerate particles formed by agglomeration of five or more particles having a particle size of <1 μm is n; a percentage of the number of the agglomerates β=n / N, where β≤1％; and 200 or more particles in the SEM image are randomly measured, an average value of maximum diameters of the a single particle is D, an average value of a width diameter perpendicular to and bisecting the maximum diameter of the particle is L, and an average aspect ratio of the particles is α=D / L, where 1<α<1.6. The positive electrode material of the present application enables the increase of the lithium ion transmission efficiency, an improvement in the long cycle performance, and alleviation of the gas generation phenomenon of the positive electrode material. FIG. 1

Description

Positive electrode materials and their positive electrode sheets, batteries Cross-references to related applications

[0001] This application claims priority to Chinese patent application filed on December 26, 2024, with application number 202411950144.3 and entitled "Cathode material and preparation method thereof, battery". Technical Field

[0002] This invention relates to the field of cathode material technology, and more particularly to cathode materials, cathode sheets, and batteries. Background Technology

[0003] Lithium-ion batteries (LIBs) have advantages such as high energy density, high power density, long cycle life, and low self-discharge, and are therefore widely used in 3C electronic products, electric vehicles, and energy storage. The cathode material, as the core component of a lithium-ion battery, directly determines the battery's operating voltage and storage capacity.

[0004] Currently, existing cathode materials are prone to agglomeration during high-temperature sintering. During the battery electrode rolling process, the agglomerate particles are easily crushed, and the exposed cathode material particles come into direct contact with the electrolyte during charging and discharging, increasing surface side reactions, leading to battery performance degradation and affecting the capacity utilization of the cathode material.

[0005] Therefore, how to reduce agglomerates in cathode materials and improve their capacity and long-cycle stability remains an urgent problem to be solved. Summary of the Invention

[0006] This application provides a cathode material, a cathode sheet, and a battery thereof. The cathode material of this application can reduce agglomerates in the cathode material and improve the capacity and long-cycle stability of the cathode material.

[0007] In a first aspect, this application provides a cathode material, the cathode material comprising a plurality of particles and aggregated particles;

[0008] The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. The total number of particles in the SEM image of the cathode material is N, N≥200, of which the number of aggregate particles formed by the aggregation of 5 or more particles with a particle size <1μm is n.

[0009] The proportion of the aggregates is β = n / N, β ≤ 1%;

[0010] Randomly measure more than 200 particles in the SEM images. The average size of the longest diameter of a single particle is D, the average size of the straight side that perpendicularly bisects the longest diameter of the particle is L, and the average aspect ratio of the particle is α = D / L, where 1 < α < 1.6.

[0011] Secondly, this application provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material described in the first aspect.

[0012] Thirdly, this application provides a battery, the battery comprising the positive electrode material described in the first aspect or the positive electrode sheet described in the second aspect.

[0013] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0014] The cathode material provided in this application has an average aspect ratio of particles within the aforementioned range. When the particles are subjected to stress, the difference in stress in each direction is small, which can slow down the propagation of particle cracks caused by local expansion, thereby reducing the side reactions between the cathode material and the electrolyte and improving long-cycle performance. When the average aspect ratio of cathode material particles is too large, the difference in stress in each direction is large when the particles are subjected to stress. More fine powder is easily generated during particle shaping, increasing the reactivity of the cathode material and increasing the side reactions with the electrolyte. On the other hand, when the average aspect ratio of cathode material particles is too large, during charge-discharge cycles, the large difference in stress in each direction can easily lead to excessive local expansion pressure, resulting in micro-cracks or even particle breakage, which reduces the structural stability and cycle stability of the cathode material. This application controls the average aspect ratio of the cathode material particles while keeping the proportion of agglomerates below 1%. Since agglomerates have low particle strength, they are easily broken during the rolling process. By controlling the proportion of agglomerates in the cathode material and the aspect ratio of the particles within the range of 1 < α < 1.6, the two work synergistically to significantly reduce particle breakage during the rolling process, reduce the consumption of active lithium ions, and comprehensively improve the long-cycle performance of the cathode material. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application;

[0017] Figure 2 is a SEM image of the cathode material provided in Embodiment 1 of this application;

[0018] Figure 3 is a SEM image of the cathode material provided in Comparative Example 2 of this application. Detailed Implementation

[0019] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0022] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0023] The inventors discovered that currently, cathode materials are produced by mixing a co-precipitation precursor with a lithium source, followed by sintering, crushing, air jet milling, coating, sieving, and demagnetization. Because the co-precipitation precursor is mostly spherical, it is prone to agglomeration during high-temperature sintering. During the battery electrode rolling process, these agglomerated particles are easily crushed, exposing the cathode material particles to direct contact with the electrolyte during charging and discharging. This increases surface side reactions, leading to battery performance degradation and affecting the cathode material's capacity utilization.

[0024] Therefore, how to reduce agglomerates in cathode materials and improve their capacity and long-cycle stability remains an urgent problem to be solved.

[0025] In a first aspect, this application provides a cathode material, the cathode material comprising a plurality of particles and aggregated particles;

[0026] The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. The total number of particles in the SEM image of the cathode material is N, N≥200, of which the number of aggregate particles formed by the aggregation of 5 or more particles with a particle size <1μm is n.

[0027] The proportion of the aggregates is β = n / N, β ≤ 1%;

[0028] Randomly measure more than 200 particles in the SEM images. The average size of the longest diameter of a single particle is D, the average size of the straight side that perpendicularly bisects the longest diameter of the particle is L, and the average aspect ratio of the particle is α = D / L, where 1 < α < 1.6.

[0029] The cathode material comprises multiple particles, including single particles and aggregated particles. Single particles refer to monocrystalline particles, while aggregated particles are formed by the aggregation of multiple single particles. In addition to particles formed by the aggregation of 5 or more single particles with a particle size <1 μm, aggregated particles also include other types of aggregated particles, such as particles formed by the aggregation of fewer than 5 single particles, and single particles with more than 5 particles and a particle size greater than 1 μm. In this application, only the number of aggregated particles satisfying the condition of 5 or more particles with a particle size <1 μm is counted as n particles.

[0030] It should be noted that, at 3k magnification, for the electron microscope (SEM) images characterizing the cathode material, the total number N of particles fully exposed in the field of view is counted. Then, the particle size in the SEM image is calculated using Nano Measure software. After measurement, the number n of agglomerates consisting of 5 or more particles with a diameter of less than 1 μm is counted. Finally, the agglomeration ratio n / N is calculated. It should be noted that the total number N includes independent single particles (monocrystalline particles) and agglomerated particles. It should be noted that particles with a diameter less than 1 μm in agglomerates refer to the diameter of the inscribed circle of the particles in the agglomerate in the electron microscope image of the cathode material. A particle fully exposed in the electron microscope image means that the particle's outline is completely displayed in the electron microscope image, and the particle's outline is not covered by other monocrystalline particles in the field of view or divided by the boundaries of the electron microscope image. A single particle refers to an independent particle in the view that has not formed an agglomerate with other particles. Aggregate particles refer to aggregate particles formed by the aggregation of 5 or more particles with a diameter of less than 1 micrometer.

[0031] It is understandable that the proportion of agglomerate particles in the cathode material can also be characterized by cross-sectional SEM images. Specifically, after sample preparation, five cross-sectional views of the sample at different positions are taken at 3K magnification. The total number N of particles fully exposed in the field of view is counted, and then the particle size in the view is measured using Nano Measure software. After measurement, the number n of agglomerates formed by five or more particles with a diameter of less than 1 micrometer that are fully exposed in the field of view is counted. The maximum distance between any two points in the agglomerate is less than or equal to 4 μm. Finally, the agglomerate proportion n / N is calculated. It should be noted that the total number of particles N mentioned above includes primary particles and agglomerate particles.

[0032] It should be noted that the particle size within the SEM image was calculated using Nano Measure software. Randomly measured particles that appeared completely within the SEM image were used. The average longest diameter of a single particle was denoted as D, the average size of the straight line perpendicularly bisecting the longest diameter of the particle was denoted as L, and the average aspect ratio of the particle was α = D / L. It should be noted that a particle appearing completely within the field of view of the electron microscope image means that the particle's outline is fully displayed in the electron microscope image, and its outline is not covered by other single-crystal particles in the field of view or divided by the boundaries of the electron microscope image. It should also be noted that the longest diameter refers to the diameter line whose two ends lie on the outline of the particle within its circumcircle. The straight line perpendicular to the midpoint of the longest straight line refers to a straight line perpendicular to the midpoint of the longest straight line and whose two ends lie on the outline of the single-crystal particle.

[0033] The cathode material provided in this application has an average aspect ratio of particles within the aforementioned range. When the particles are subjected to stress, the difference in stress in each direction is small, which can slow down the propagation of particle cracks caused by local expansion, thereby reducing the side reactions between the cathode material and the electrolyte and improving long-cycle performance. When the average aspect ratio of cathode material particles is too large, the difference in stress in each direction is large when the particles are subjected to stress. More fine powder is easily generated during particle shaping, increasing the reactivity of the cathode material and increasing the side reactions with the electrolyte. On the other hand, when the average aspect ratio of cathode material particles is too large, during charge-discharge cycles, the large difference in stress in each direction can easily lead to excessive local expansion pressure, resulting in micro-cracks or even particle breakage, which reduces the structural stability and cycle stability of the cathode material.

[0034] This application controls the average aspect ratio of cathode material particles while keeping the proportion of agglomerates below 1%. Since agglomerates have low particle strength, they are prone to breakage and separation during the rolling process. By controlling the proportion of agglomerates in the cathode material and the aspect ratio of the particles within the range of 1 < α < 1.6, the two work synergistically to significantly reduce particle breakage during the rolling process, reduce the consumption of active lithium ions, and comprehensively improve the long-cycle performance of the cathode material.

[0035] In some embodiments, the cathode material is a lithium nickel cobalt oxide compound, and the general chemical formula of the cathode material is Li. k Ni a Co b N c M d O2, 0.98≤k≤1.1, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.35, 0≤d≤0.10, a+b+c+d=1, N is Mn or Al.

[0036] In some embodiments, the cathode material is a lithium cobalt oxide compound, and the general chemical formula of the cathode material is Li. k Ni a Co b N c M d O2, 0.98≤k≤1.1, 0.50≤a≤0.98, 0<b≤0.20, 0<c≤0.35, 0≤d≤0.10, a+b+c+d=1, N is Mn or Al, M includes metallic elements except Li, Ni and Co.

[0037] The specific values ​​of k can be 0.98, 0.99, 1.0, 1.02, 1.04, 1.05, 1.07, 1.08, 1.09, or 1.1, etc.; the specific values ​​of a can be 0.5, 0.6, 0.7, 0.8, 0.82, 0.84, 0.85, 0.88, 0.89, 0.90, 0.92, 0.95, or 0.98, etc.; and the specific values ​​of b can be 0.001, 0.01, 0.05, 0.1, or 0.1. 5, 0.16, 0.17, 0.19 or 0.2, etc.; the value of c can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.16, 0.18, 0.2, 0.25, 0.3 or 0.35, etc.; the value of d can be 0, 0.001, 0.005, 0.006, 0.008, 0.009, 0.01, 0.02, 0.03, 0.05, 0.07 or 0.1, etc., without limitation here.

[0038] The cathode material of this invention is a lithium cobalt oxide compound. Specifically, the lithium cobalt oxide compound can be one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium cobalt oxide. Specifically, the cathode material can be characterized by inductively coupled plasma optical emission spectrometry (ICP-OES) or mass spectrometry (ICP-MS) to determine the presence of lithium (Li) and cobalt (Co) and their elemental ratio, thus characterizing the cathode material as a lithium cobalt oxide compound. The cathode material can also be characterized by X-ray diffraction (XRD). An XRD pattern showing a layered α-NaFeO2 structure with space group R-3m indicates that the cathode material is a lithium cobalt oxide compound.

[0039] In some embodiments, the M element includes at least one selected from Al, Ti, Zr, Mg, Sr, Ba, Ca, Y, B, Nb, W, Sb, Ta, Sn, Mo, La, and Ce. Understandably, doping the cathode material with the M element can improve the lattice structure stability of the cathode material and reduce lithium-nickel mixing.

[0040] In some embodiments, the proportion of agglomerates β is ≤ 1%, where β can specifically be 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.3%, 0.2%, 0.1%, 0.05%, etc., or other values ​​within the above range, which are not limited here. When β > 1%, it means that the number of particle agglomerates increases. During the electrode rolling process, the agglomerates are easily broken, increasing the exposed surface of the positive electrode material and increasing side reactions with the electrolyte, thus affecting the capacity utilization and long-cycle stability of the positive electrode material. This application controls the proportion of agglomerates β to be within the range of ≤ 1%, resulting in higher particle strength of the positive electrode material, which can reduce particle breakage during electrode rolling, significantly reducing the exposed surface of fine powder and particles, thereby improving gas generation. It should be noted that the agglomerate refers to an agglomerate formed by the aggregation of 5 or more particles with a particle size < 1 μm, and the maximum length of the agglomerate in the SEM image is less than 4 μm. It should be noted that the maximum length of the aggregate refers to the diameter of its circumscribed circle. It is understood that in some other embodiments, the maximum length of the aggregate is less than 6 μm.

[0041] In some embodiments, the particle size satisfies the following conditions: 2.0 μm < D < 3.0 μm; 1.5 μm ≤ L ≤ 2.5 μm. Specifically, D can be 2.1 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, or 2.9 μm, or other values ​​within the above range, which are not limited here. Similarly, L can be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, or 2.5 μm, or other values ​​within the above range, which are not limited here.

[0042] In some embodiments, the average aspect ratio of the particles satisfies 1 < α < 1.6, specifically 1.1, 1.2, 1.3, 1.4, 1.5, or 1.59, etc., and of course, other values ​​within the above range are also possible and are not limited here. An average aspect ratio within the above range can improve the problem of excessive local expansion stress, slow down the propagation of particle cracks caused by local expansion, thereby reducing side reactions between the cathode material and the electrolyte, and improving long-cycle performance. When the aspect ratio of the particles is too large, it indicates poor particle roundness and obvious edges, which easily generates more fine powder during the airflow pulverization process of the cathode material particles, leading to an increase in the specific surface area of ​​the cathode material and an increase in side reactions with the electrolyte. In addition, particles with poor roundness are prone to excessive local expansion pressure during charge-discharge cycles, and micro-cracks are easily generated inside the particles, even leading to particle breakage, resulting in a decrease in the structural stability and cycle stability of the cathode material.

[0043] In some embodiments, the volume median particle size D of the cathode material 50 The median particle size is 3.0 μm to 5.0 μm, specifically 3.0 μm, 3.2 μm, 3.5 μm, 4.0 μm, 4.3 μm, 4.5 μm, 4.8 μm, or 5.0 μm, or other values ​​within this range. Since most particles in the cathode material are particulates, meaning the median particle size falls within this range, particles in this size range exhibit superior electrochemical performance, higher discharge capacity, and excellent rate performance.

[0044] In some embodiments, the volumetric particle size distribution width of the cathode material satisfies: 1.0 < (D 90 -D 10 ) / D 50 <1.5, specifically can be 1.05, 1.08, 1.1, 1.15, 1.18, 1.2, 1.22, 1.25, 1.26, 1.28, 1.3, 1.35, 1.4, or 1.49, etc., and of course, other values ​​within the above range are also possible, without limitation. This application controls the particle size distribution width of the positive electrode material within the above range, allowing particles of different sizes to achieve a more compact stacking, thereby increasing the compaction density of the positive electrode sheet and achieving a higher energy density.

[0045] In some embodiments, the cathode material is a single-crystal material, the particles include primary particles, the primary particles have the same orientation, and the particle size of the primary particles is 1μm to 5μm.

[0046] It is important to clarify that the "grains with the same orientation" as understood by those skilled in the art are not strictly speaking "single crystals." In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations imposed by impurities, strain, and crystal defects, ideal single crystals are extremely rare and difficult to produce in reality. Therefore, materials known in the art to possess a single-crystal structure are actually more accurately described as "single-crystal morphology" cathode materials, which differ from polycrystalline particles composed of numerous small particles only in size due to their large, single-crystal-like particle size.

[0047] In this application, particles with the same orientation can be single particles composed of a primary particle. The aforementioned single-crystal cathode material may also contain a small number of "quasi-secondary particles" formed by the adhesion of several primary particles. "Primary particle" refers to the smallest particle unit identified when observing the cathode active material using a scanning electron microscope.

[0048] 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 nanometer-sized agglomerations of primary particles. In contrast, the smallest particles in single-crystal cathode materials are typically micrometer-sized individual 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 primary particle has the same color, indicating that at least one primary particle has the same orientation; primary particles 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.

[0049] In some implementations, the specific surface area of ​​the cathode material is S m 2 / g, 0.5 < S < 0.9; specifically, it could be 0.51m 2 / g, 0.55m 2 / g, 0.58m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.85m 2 / g or 0.89m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Controlling the specific surface area of ​​the cathode material within the above range can effectively control the side reactions between the cathode material and the electrolyte, and improve the capacity of the cathode material.

[0050] In some embodiments, the tap density of the cathode material is ρ1g / cm³. 3 1.8 < ρ1 < 2.5, specifically 1.82 g / cm³ 3 1.85g / cm 3 1.9g / cm 3 1.95g / cm 3 1.98g / cm3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.25g / cm 3 2.3g / cm 3 2.4g / cm 3 Or 2.49 g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. When the tap density of the cathode material is too low, the compaction density of the cathode sheet prepared from the cathode material decreases, and the particle strength also decreases relatively, leading to a decrease in the energy density of the lithium-ion battery. When the tap density of the cathode material is too high, the compaction density of the cathode sheet prepared from the cathode material is too high, the porosity of the cathode sheet decreases, which makes it difficult for the electrolyte to effectively wet the electrode sheet, increasing the internal resistance of the lithium-ion battery and decreasing the specific capacity of the cathode material. This application controls the tap density of the cathode material within the above range, which is beneficial to improving the energy density of the cathode sheet.

[0051] In some embodiments, the compaction density of the cathode material is ρ² g / cm³. 3 3 < ρ² < 3.5. Specifically, it could be 3.05 g / cm³. 3 3.1g / cm 3 3.15g / cm 3 3.18 g / cm 3 3.2g / cm 3 3.25g / cm 3 3.3g / cm 3 3.35g / cm 3 3.4g / cm 3 3.45g / cm 3 3.48 g / cm 3 Or 3.49 g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. This application controls the compaction density of the cathode material within the above range, which is beneficial to the utilization of the cathode material's capacity, improves the energy density, reduces the polarization phenomenon of the battery prepared with the cathode material during cycling, and helps to improve the battery's capacity retention rate.

[0052] In some embodiments, the mass content of residual alkali in the cathode material is m. Li wt%, 0.10 < m Li <0.25, m LiSpecifically, the content can be 0.11wt%, 0.12wt%, 0.15wt%, 0.18wt%, 0.20wt%, 0.22wt%, 0.23wt%, or 0.24wt%, but is not limited to the listed values; other unlisted values ​​within this range also apply. Understandably, the alkaline impurities on the surface of the cathode material mainly refer to Li₂CO₃ and LiOH. Controlling the total mass content of residual alkali (LiOH and Li₂CO₃) on the cathode material surface within the above range can reduce the corrosive effect of alkaline substances on the cathode material, protect the structural stability of the cathode material, and help improve the cycle stability of the cathode material.

[0053] Secondly, this application provides a method for preparing the above-mentioned cathode material, comprising the following steps:

[0054] Step S100: Mix the oxide precursor, lithium source, dopant and pore-forming agent to obtain a first mixture, wherein the amount of pore-forming agent added is 1% to 5% based on the mass of the oxide precursor as 100%.

[0055] Step S200: Under an oxygen-containing atmosphere, the first mixture is subjected to pulse sintering treatment to obtain a matrix material. The pulse sintering treatment includes a first stage, a second stage, and repeated first and second stages. The sintering temperature T1 of the first stage is 800℃~1000℃, the sintering temperature T2 of the second stage is T1-30℃, and the total holding time for controlling the T1 temperature is 4h~8h.

[0056] In step S300, the matrix material is subjected to a dissociation treatment. The dissociation product is mixed with the coating agent and then subjected to a secondary sintering treatment to obtain the cathode material.

[0057] The method for preparing the cathode material provided in this application involves mixing an oxide precursor, a lithium source, a dopant, and a pore-forming agent. The addition of the pore-forming agent facilitates sufficient contact between the precursor and oxygen during sintering, accelerates the reaction rate, increases the porosity of the matrix material, reduces particle agglomeration, and significantly reduces the proportion of agglomerates in the cathode material. It also improves the roundness of the particles in the matrix material. Furthermore, the pulse sintering process, with its shorter high-temperature sintering time, results in more uniform particle growth, allowing the average aspect ratio of the sintered particles to be controlled within a suitable range. The matrix material undergoes a dissociation treatment, during which some agglomerates of 2-3 particles can be re-dissociated into individual particles, reducing the proportion of agglomerates in the cathode material. During the secondary sintering process, the coating agent can form a coating substance on the particle surface of these particles with exposed surfaces, reducing residual alkali on the cathode material surface and further improving the particle tolerance and structural order of the cathode material, improving cation mixing phenomenon, thereby increasing the compaction density and capacity of the cathode material, and also improving the long-cycle performance of the cathode material.

[0058] The preparation method of this application is described in detail below with reference to the above embodiments:

[0059] Before step S100, the method further includes: preparing a salt solution of nickel, manganese and nitrogen elements, preparing a mixed solution according to a certain stoichiometric ratio, and preparing an oxide precursor by using a spray pyrolysis method, wherein the nitrogen element is Mn or Al.

[0060] In some implementations, the stoichiometric ratios of nickel, cobalt, and nitrogen meet the following conditions: 0.5 ≤ Ni ≤ 0.98, 0 < Co ≤ 0.2, 0 < Mn ≤ 0.35; the molar ratio of Ni:Co:Mn can specifically be 0.60:0.10:0.30, 0.67:0.05:0.28, or 0.90:0.5:0.05, etc.

[0061] In some embodiments, the salt solution is at least one of nitrate, hydrochloride, sulfate, carbonate, oxalate, and acetate. For example, the nickel salt solution may be at least one of nickel chloride, nickel sulfate, nickel nitrate, nickel carbonate, nickel oxalate, and nickel acetate. Of course, nickel, manganese, aluminum, and cobalt may also be elemental metal raw materials or recycled materials from ternary cathode materials, and are not limited thereto.

[0062] In some embodiments, a compound containing element M is also added to the salt solution according to the target doping ratio. Specifically, it may be a nitrate containing element M, a hydrochloride containing element M, an acid containing element M, etc., which is not limited here.

[0063] In some embodiments, the element M includes at least one selected from Al, Ti, Zr, Mg, Sr, Ba, Ca, Y, B, Nb, W, Sb, Ta, Sn, Mo, La, and Ce.

[0064] In some embodiments, spray pyrolysis includes a dehydration stage and a pyrolysis stage, wherein the temperature of the dehydration stage is 300°C to 500°C and the temperature of the pyrolysis stage is 500°C to 850°C.

[0065] Specifically, the temperature during the dehydration stage can be 300℃, 350℃, 380℃, 400℃, 430℃, 450℃, or 500℃, or other values ​​within the above range; no limitation is made here. The temperature during the pyrolysis stage can be 510℃, 520℃, 530℃, 550℃, 600℃, 650℃, 680℃, 700℃, 750℃, 800℃, or 850℃, or other values ​​within the above range; no limitation is made here. In the dehydration temperature zone, the mixed solution after spray atomization treatment is rapidly dehydrated, and in the pyrolysis temperature zone, the dehydrated particles are ultimately pyrolyzed into oxide precursor particles.

[0066] In some embodiments, the products of spray pyrolysis are subjected to air jet milling to control the oxide precursor D. 50 The micrometer size ranges from 2.0 μm to 4.0 μm, specifically 2.0 μm, 2.2 μm, 2.5 μm, 3.0 μm, 3.3 μm, 3.5 μm, 3.8 μm, or 4.0 μm, or other values ​​within the above range.

[0067] In some embodiments, the general chemical formula of the oxide precursor is Ni. x Co y N z M e O2, where 0.50≤x≤0.98, 0<y≤0.20, 0<z≤0.35, 0≤e≤0.05, x+y+z+e=1, and N is Mn or Al.

[0068] Step S100: Mix the oxide precursor, lithium source, dopant and pore-forming agent to obtain a first mixture, wherein the amount of pore-forming agent added is 1% to 5% based on the mass of the oxide precursor as 100%.

[0069] In some embodiments, the amount of pore-forming agent added can be 1%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. If too little pore-forming agent is added, the growth process of the cathode material particles is greatly affected by sintering conditions such as atmosphere and temperature, easily leading to insufficient particle growth, sharp edges, and increased soft agglomerates, thus affecting cycle performance. If too much pore-forming agent is added, the cathode material particles grow uniformly, the volume distribution width of the cathode material narrows, the compaction density decreases, and the capacity is affected.

[0070] In some embodiments, the pore-forming agent includes at least one of carbon powder, sucrose, starch, pine powder, polyvinyl alcohol, polymethyl methacrylate, polyethylene glycol, and coal powder.

[0071] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate, and lithium oxalate.

[0072] In some embodiments, the ratio of the molar amount of Li in the lithium source to the total molar amount of transition metal in the oxide precursor is controlled to be 1.0 ≤ n. Li / n Me ≤1.06; specifically, it can be 1.0:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1 or 1.06:1, etc., and of course, it can also be other values ​​within the above range, which are not limited here.

[0073] In some embodiments, based on 100% by mass of the oxide precursor, the amount of dopant added is 0.05% to 0.4%, specifically 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.28%, 0.3%, 0.35%, or 0.4%, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable. Controlling the amount of dopant added within the above range in this application is beneficial for controlling the size and arrangement of the cathode material particles, thereby improving the capacity and particle structure stability of the cathode material.

[0074] In some embodiments, mixing is carried out in a mixing device, which may be a high-speed mixer, ball mill mixer, VC mixer, or three-dimensional mixer, etc., and can be selected according to actual needs, without limitation. Understandably, thorough mixing is beneficial to improving the uniformity of the distribution of oxide precursor and lithium source, reducing structural defects in cathode materials, and improving the structural order of cathode materials.

[0075] Step S200: Under an oxygen-containing atmosphere, the first mixture is subjected to pulse sintering treatment to obtain a matrix material. The pulse sintering treatment includes a first stage, a second stage, repeated first and second stages, and a fifth stage. The sintering temperature T1 of the first stage is 800℃~1000℃, the sintering temperature T2 of the second stage is T1-30℃, and the sintering temperature T5 of the fifth stage is T2-10℃. The total holding time for controlling the T1 temperature is 4h~8h.

[0076] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥95%.

[0077] In some embodiments, the heating rate of the pulse sintering process is 0.5℃ / min to 2.5℃ / min, specifically 0.5℃ / min, 0.75℃ / min, 1℃ / min, 1.25℃ / min, 1.5℃ / min, 2℃ / min, 2.25℃ / min or 2.5℃ / min, etc. Of course, other values ​​within the above range are also possible, and are not limited here.

[0078] In some embodiments, the ambient pressure during the pulse sintering process is 20 Pa to 60 Pa, specifically 20 Pa, 25 Pa, 30 Pa, 35 Pa, 40 Pa, 45 Pa, 50 Pa, 55 Pa or 60 Pa, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0079] In some embodiments, during the pulse sintering process, the sintering temperature T1 of the first stage is 800℃~1000℃, specifically it can be 800℃, 820℃, 830℃, 850℃, 870℃, 900℃, 950℃, 980℃, 990℃ or 1000℃, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0080] In some implementations, the holding time for the first stage of pulse sintering is 1h to 2h, specifically 1.0h, 1.2h, 1.5h or 2h, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0081] In some implementations, the sintering temperature T2 in the second stage is T1-30℃, specifically 770℃, 820℃, 850℃, 870℃, 900℃, 950℃ or 970℃, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0082] In some implementations, the heat preservation time in the second stage is 1h to 2h, specifically 1.0h, 1.2h, 1.5h or 2h, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0083] In some implementations, the total holding time for controlling the T1 temperature during the entire pulse sintering process is 4h to 8h, specifically 4.0h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0084] In some embodiments, during the pulse sintering process, the sintering temperature T4 in the fourth stage is T2-10℃, that is, 760℃~960℃. Specifically, it can be 760℃, 820℃, 850℃, 870℃, 900℃, 950℃ or 960℃, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0085] In some implementations, the heat preservation time in the fourth stage is 4h to 6h, specifically 4h, 4.5h, 5h, 5.5h, 5.8h or 6h, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0086] Controlling the temperature and time in the fourth stage of pulse sintering within the above range can promote the repair of the grain boundary surface of the cathode material, thereby improving the particle tolerance and structural order of the cathode material.

[0087] In step S300, the matrix material is subjected to a dissociation treatment. The dissociation product is mixed with the coating agent and then subjected to a secondary sintering treatment to obtain the cathode material.

[0088] In some embodiments, the dissociation process includes at least one of roller crushing, mechanical pulverization, air jet milling, and micron-sized particle dissociation.

[0089] In some embodiments, the dissociation process includes air jet milling, where the grinding pressure is 0.3 MPa to 0.8 MPa, specifically 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, or 0.8 MPa, or other values ​​within the above range, which are not limited here.

[0090] In some embodiments, the classifying frequency of the air jet mill is 30Hz to 55Hz, specifically 30Hz, 35Hz, 40Hz, 45Hz, 50Hz or 55Hz, etc., or other values ​​within the above range, which are not limited here.

[0091] In some embodiments, the proportion of agglomerates in the dissociation product is ≤1%, specifically 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.3%, 0.2%, 0.1%, 0.05%, etc., or other values ​​within the above range, which are not limited here.

[0092] This application reduces the proportion of agglomerates in the cathode material by controlling the grinding pressure and classification frequency during airflow pulverization. Some agglomerates formed by the aggregation of 2 to 3 primary particles can be re-dissociated into individual particles during the dissociation process. During the secondary sintering process, the coating agent can form a coating layer on the particle surface of these particles with exposed surfaces, reducing the residual alkali on the surface of the cathode material and further improving the particle tolerance and structural order of the cathode material, thus improving the cation mixing phenomenon.

[0093] In some implementations, the median particle size of the dissociation products is ≤5 μm.

[0094] In some embodiments, the amount of coating agent added is 0.1% to 0.8% based on 100% of the mass of the dissociated product. Specifically, it can be 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.28%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, or 0.8%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0095] In some embodiments, the coating agent comprises a compound containing element M, which includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Y, B, Nb, W, Sb, Ta, Sn, Mo, La, and Ce.

[0096] In some embodiments, the coating agent includes La(NO3)3·6H2O, (NH4)HB4O7, (NH4)2MoO4, H3BO3, and (NH4)6W7O. 24 ·6H2O、(NH4)3PW 12 O 40 ·3H2O, Zr(SO4)2·4H2O, H 28 N6O 41 W 12 At least one of WO3 and Al2O3. It should be noted that, due to H... 28 N6O 41 W 12 It is difficult to dissolve in water, therefore H is used. 28 N6O 41 W 12 When used as a coating agent, H 28 N6O41 W 12 Dry mixing directly with the matrix material.

[0097] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥95%.

[0098] In some embodiments, the temperature of the secondary sintering treatment is 350℃ to 600℃, specifically 350℃, 360℃, 380℃, 400℃, 420℃, 480℃, 500℃, 550℃ or 600℃, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0099] In some implementations, the secondary sintering treatment time is 5h to 10h, specifically 5h, 5.5h, 6h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0100] Thirdly, this application provides a battery comprising the positive electrode material described in the first aspect or a positive electrode material prepared according to the method for preparing the positive electrode material described above.

[0101] The battery provided in this application can be a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, electrode assembly, and electrolyte. Both the electrode assembly and electrolyte are located inside the casing. The casing can be a packaging bag sealed with an encapsulating film (such as an aluminum-plastic film), such as a pouch battery for secondary batteries.

[0102] In other embodiments, the secondary battery may also be a steel-cased battery, an aluminum-cased battery, etc.

[0103] Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application. As shown in Figure 1, the battery includes a casing and an electrode assembly. The electrode assembly includes a positive electrode 1, a negative electrode 2, and a separator 3, with the separator 3 disposed between the positive electrode 1 and the negative electrode 2. The electrode assembly can be a stacked structure, which is formed by alternating layers of the positive electrode 1, the separator 3, and the negative electrode 2.

[0104] In other embodiments, the electrode assembly can also be a wound structure, which is formed by sequentially stacking and winding a positive electrode, a separator, and a negative electrode.

[0105] In some embodiments, the positive electrode 1 includes a positive current collector 11 and a positive active material layer 12 disposed on at least one surface of the positive current collector 11.

[0106] In some embodiments, the positive electrode current collector 11 can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and the polymer substrate. The positive electrode active material layer 12 comprises a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material is the positive electrode material of the first aspect described above or a positive electrode material prepared according to the above-described method for preparing the positive electrode material.

[0107] In some embodiments, the negative electrode 2 includes a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on at least one surface of the negative electrode current collector.

[0108] In some embodiments, the negative electrode current collector 21 may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil and polymer substrate.

[0109] In some embodiments, the negative electrode active material layer 22 includes a negative electrode material, which includes, but is not limited to, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0110] The battery provided in this application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion. The battery can be a lithium-ion battery, a sodium-ion battery, a solid-state electrolyte battery, etc., and is not limited thereto.

[0111] The technical solution of this application will be further described below with reference to the embodiments:

[0112] Example 1

[0113] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 60:10:30. Then add a hydrochloric acid solution of 0.2% Zr and hydrochloric acid solutions of 0.05% Sr and 0.05% Ca to the mixed solution.

[0114] (2) The cathode material precursor (Ni) was synthesized by spray pyrolysis (dehydration temperature zone 500℃, pyrolysis temperature zone 650℃). 0.6 Co 0.1 Mn 0.3O (Since the amounts of doping elements Zr, Sr, and Ca are difficult to determine precisely, they are not reflected in the chemical formula), the cathode material precursor is subjected to airflow pulverization to obtain a particle size D. 50 Oxide precursor with a diameter of 3.3 μm.

[0115] (3) The oxide precursor and Li2CO3 were mixed evenly at a molar ratio of 1:1.03 and the oxide precursor and sucrose were mixed at a mass ratio of 1:3% to obtain the first mixture. The first mixture was then subjected to pulse sintering under an oxygen atmosphere with an ambient pressure of 40 Pa. The specific sintering process was as follows: the temperature T1 of the first stage sintering was 970℃ and the holding time t1 was 4h; the temperature T2 of the second stage sintering was 940℃ and the holding time t2 was 2h; the temperature T3 of the third stage sintering was 970℃ and the holding time t3 was 2h; the temperature T4 of the fourth stage sintering was 940℃ and the holding time t4 was 2h; and the temperature T5 of the fifth stage sintering was 930℃ and the holding time t5 was 4h to obtain the matrix material.

[0116] (4) The matrix material is subjected to roller crushing, air jet milling and sieving. During air jet milling, the grinding air pressure is set to 0.55 MPa and the grading frequency is 40 Hz to obtain the dissociation product.

[0117] (5) The dissociation product is mixed with Al2O3 and WO3 in a weight ratio of 100:0.2:0.3 to obtain a second mixture. The second mixture is placed in an oxygen-containing atmosphere for secondary sintering at a temperature of 500°C for 8 hours. The obtained secondary sintering product is sieved and demagnetized to obtain the positive electrode material.

[0118] The general chemical formula of the cathode material prepared in this embodiment is: LiNi 0.6 Co 0.1 Mn 0.3 O2, in which doping elements include Zr, Sr, Al and W. Since the amount of doping elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0119] Example 2

[0120] Unlike Example 1:

[0121] In step (3), Li2CO3 is replaced with LiOH, and the remaining steps are the same as in Example 1.

[0122] Example 3

[0123] Unlike Example 1:

[0124] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 50:20:30. Then add a hydrochloric acid solution of 0.2% Zr and a hydrochloric acid solution of 0.05% Sr and 0.05% Ca to the mixed solution.

[0125] The pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 980℃ and the holding time t1 is 4h; the temperature T2 of the second sintering stage is 950℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 980℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 950℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 940℃ and the holding time t5 is 4h, thus obtaining the matrix material.

[0126] Example 4

[0127] Unlike Example 1:

[0128] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 70:10:20. Then add a hydrochloric acid solution of 0.2% Zr and a hydrochloric acid solution of 0.05% Sr and 0.05% Ca to the mixed solution.

[0129] The pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 940℃ and the holding time t1 is 4h; the temperature T2 of the second sintering stage is 910℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 940℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 910℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 900℃ and the holding time t5 is 4h, thus obtaining the matrix material.

[0130] Example 5

[0131] Unlike Example 1:

[0132] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 80:10:10. Then add a hydrochloric acid solution of 0.2% Zr and a hydrochloric acid solution of 0.05% Sr and 0.05% Ca to the mixed solution.

[0133] The pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 870℃ and the holding time t1 is 4h; the temperature T2 of the second sintering stage is 840℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 870℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 840℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 830℃ and the holding time t5 is 4h, thus obtaining the matrix material.

[0134] Example 6

[0135] Unlike Example 1:

[0136] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 90:6:4. Then add a hydrochloric acid solution of 0.2% Zr and a hydrochloric acid solution of 0.05% Sr and 0.05% Ca to the mixed solution.

[0137] The pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 830℃ and the holding time t1 is 4h; the temperature T2 of the second sintering stage is 800℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 830℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 800℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 790℃ and the holding time t5 is 4h, and the sintered product is obtained.

[0138] Example 7

[0139] Compared with Example 1, the amount of sucrose used in step (3) is 1%, and the remaining steps are the same as in Example 1.

[0140] Example 8

[0141] Compared with Example 1, the amount of sucrose used in step (3) is 5%, and the remaining steps are the same as in Example 1.

[0142] Example 9

[0143] Compared with Example 1, the pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 960℃ and the holding time t1 is 4h; the temperature T2 of the second sintering stage is 930℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 960℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 930℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 920℃ and the holding time t5 is 4h, and the sintered product is obtained.

[0144] Example 10

[0145] The difference compared to Example 1 is as follows:

[0146] The pulse sintering process in step (3) is as follows: the temperature T1 of the first sintering stage is 970℃ and the holding time t1 is 2h; the temperature T2 of the second sintering stage is 940℃ and the holding time t2 is 2h; the temperature T3 of the third sintering stage is 970℃ and the holding time t3 is 2h; the temperature T4 of the fourth sintering stage is 940℃ and the holding time t4 is 2h; the temperature T5 of the fifth sintering stage is 930℃ and the holding time t5 is 4h, and the sintered product is obtained.

[0147] Example 11

[0148] Compared with Example 1, the amount of pore-forming agent (polymethyl methacrylate) used in step (3) is 3%, and the remaining steps are the same as in Example 1.

[0149] Example 12

[0150] (1) Weigh out nickel chloride, cobalt chloride and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 60:10:30.

[0151] (2) The cathode material precursor (Ni) was synthesized by spray pyrolysis (dehydration temperature zone 500℃, pyrolysis temperature zone 650℃). 0.6 Co 0.1 Mn 0.3 O), the cathode material precursor is subjected to airflow pulverization to obtain a particle size D. 50 Oxide precursor with a diameter of 3.3 μm.

[0152] (3) Ni oxide precursor 0.6 Co 0.1 Mn 0.3 O and Li₂CO₃ are mixed in a molar ratio of 1:1.03, Ni 0.6 Co 0.1 Mn 0.3 O and carbon powder are mixed uniformly at a mass ratio of 1:3% to obtain a first mixture. The first mixture is then subjected to pulse sintering treatment under an oxygen atmosphere with an ambient pressure of 40 Pa. The specific sintering process is as follows: the first stage sintering temperature T1 is 970℃, and the holding time t1 is 4h; the second stage sintering temperature T2 is 940℃, and the holding time t2 is 2h; the third stage sintering temperature T3 is 970℃, and the holding time t3 is 2h; the fourth stage sintering temperature T4 is 940℃, and the holding time t4 is 2h; the fifth stage sintering temperature T5 is 930℃, and the holding time t5 is 4h, thus obtaining the matrix material.

[0153] (4) The matrix material is crushed by roller crushing, air jet milling and sieving. During air jet milling, the grinding air pressure is set to 0.55 MPa and the grading frequency is 40 Hz to obtain the positive electrode material.

[0154] Example 13

[0155] Compared with Example 1, in step (1), nickel chloride, cobalt chloride and aluminum chloride are weighed and mixed hydrochloride solution is prepared according to the molar ratio of Ni:Co:Al = 60:10:30.

[0156] Comparative Example 1

[0157] Unlike Example 1:

[0158] (1) Weigh nickel chloride, cobalt chloride, and manganese chloride, and prepare a mixed hydrochloric acid solution according to the molar ratio of Ni:Co:Mn = 60:10:30. Then add a 0.2% Zr hydrochloric acid solution and a 0.01% Sr hydrochloric acid solution to the mixed solution. Add the solution to a reactor at 55°C, and use NaOH and NH3·H2O as precipitating and chelating agents respectively to carry out a co-precipitation reaction for 36 hours to obtain Ni. 0.6 Co 0.1 Mn 0.3 The (OH)₂ precursor was dried at 80°C for 12 hours, and then dried again at 110°C for 12 hours to obtain the hydroxide precursor Ni. 0.6 Co 0.1 Mn 0.3 (OH)2.

[0159] Step (2) was skipped, and step (3) was performed directly:

[0160] (3) The hydroxide precursor and Li2CO3 were mixed evenly at a molar ratio of 1:1.03 and the hydroxide precursor and sucrose were mixed evenly at a mass ratio of 1:0.2%:3% to obtain the first mixture. The first mixture was then subjected to pulse segmented sintering under an oxygen atmosphere. The specific sintering process was as follows: the temperature T1 of the first sintering stage was 970℃ and the holding time t1 was 4h; the temperature T2 of the second sintering stage was 940℃ and the holding time t2 was 2h; the temperature T3 of the third sintering stage was 970℃ and the holding time t3 was 2h; and the temperature T4 of the fourth sintering stage was 930℃ and the holding time t4 was 4h to obtain the sintered product.

[0161] The remaining steps are the same as in Example 1.

[0162] Comparative Example 2

[0163] Compared with Example 1, the amount of sucrose used in step (3) is 0%, and the remaining steps are the same as in Example 1.

[0164] Comparative Example 3

[0165] Compared with Example 1, (3) the oxide precursor and Li2CO3 were mixed evenly at a molar ratio of 1:1.03 and the oxide precursor and sucrose were mixed evenly at a mass ratio of 1:3% to obtain the first mixture. The first mixture was sintered in an oxygen atmosphere with an ambient pressure of 40 Pa, a sintering temperature of 970 °C, and a holding time of 7 h to obtain the matrix material.

[0166] Comparative Example 4

[0167] Compared with Example 1, in step (4), the matrix material is subjected to roller crushing, air jet milling and sieving. During air jet milling, the grinding air pressure is set to 0.3 MPa and the grading frequency is 30 Hz to obtain the dissociation product.

[0168] Test method:

[0169] (1) Particle distribution test of cathode material:

[0170] The SEM image of the cathode material was obtained using a Hitachi S4800 scanning electron microscope at 3K magnification. The total number of particles in the SEM image of the cathode material was N, of which n were aggregates of 5 or more particles with a diameter <1 μm. The proportion of aggregates was β = n / N. Specifically, at 3K magnification, the total number N of particles fully exposed in the field of view was counted in the electron microscope image of the cathode material. Then, the particle size in the SEM image was calculated using Nano Measure software. After the measurement, the number n of aggregates formed by 5 or more particles with a diameter of less than 1 μm fully exposed in the field of view was counted. The maximum distance between any two points in an aggregate was less than or equal to 4 μm. Finally, the proportion of aggregates n / N was calculated. It should be noted that the total number of particles N includes single particles (single crystal particles) and aggregate particles, that is, all particles in the field of view. It should be noted that particles with a diameter of less than 1 μm in an agglomerate refer to the diameter of the inscribed circle of the particle in the agglomerate in the electron microscope (EM) view of the cathode material. A particle appearing completely in the EM image field of view means that the particle's outline is fully displayed in the EM image, and its outline is not obscured by other single-crystal particles in the field of view or divided by the boundaries of the EM image. A single particle refers to an independent particle in the view that has not formed an agglomeration with other particles. An agglomerate particle refers to an agglomeration of 5 or more particles with a diameter of less than 1 micrometer. It is understandable that the proportion of agglomerate particles in the cathode material can also be characterized by cross-sectional SEM images. Specifically, after sample preparation, five cross-sectional views of the sample at different positions are taken at 3K magnification. The total number N of particles fully exposed in the field of view is counted, and then the particle size in the view is measured using Nano Measure software. After measurement, the number n of agglomerates formed by five or more particles with a diameter of less than 1 micrometer that are fully exposed in the field of view is counted, with the longest diameter of the agglomerate being less than or equal to 4 μm. Finally, the agglomerate proportion n / N is calculated. It should be noted that the total number of particles N mentioned above includes primary particles and agglomerate particles.

[0171] The particle size within the SEM images was calculated using Nano Measure software. More than 200 particles that appeared completely within the SEM images were randomly measured. The average longest diameter of a single particle was denoted as D, and the average size of the straight line bisecting the longest diameter of the particle was denoted as L. The average aspect ratio of the particles was α = D / L. The longest diameter of the aggregates was less than 4 μm. It should be noted that a particle appearing completely within the field of view of the electron microscope image means that the particle's outline is fully displayed in the electron microscope image, and the particle's outline is not covered by other single-crystal particles in the field of view or divided by the boundaries of the electron microscope image. It should also be noted that the longest diameter refers to the diameter line whose two ends lie on the outline of the particle within its circumcircle. The straight line perpendicular to the midpoint of the longest straight line refers to a straight line perpendicular to the midpoint of the longest straight line and whose two ends lie on the outline of the single-crystal particle.

[0172] The particle size within the SEM image was calculated using Nana Measure software. The longest diameter of a primary particle was measured as its diameter, which ranged from 1 μm to 5 μm. The longest diameter of a primary particle is the diameter of its circumscribed circle.

[0173] (2) Testing of the metal element content in the cathode material:

[0174] The content of various metallic elements in the cathode material was determined by ICP testing. An Agilent 5800 ICP spectrometer was used to analyze the elemental content in the material. The specific procedure was as follows: 0.4g of the ternary cathode material was added to an Erlenmeyer flask, followed by 60mL of pure water and 8mL of aqua regia. The flask was placed on a graphite heating platform and digested at 375℃ until clear. The resulting solution was diluted to 100mL using a volumetric flask to obtain the mother liquor. An Agilent 5110 ICP-OES instrument was used to test the diluted solution to characterize the content of the main elements Li / Ni / Co / Mn / Al. The Agilent 5110 ICP-OES instrument was used to test the mother liquor to characterize the content of other elements such as M and N, thus obtaining the content of element M.

[0175] (3) Particle size test:

[0176] The particle size distribution of the cathode material particles was obtained using a Malvern Mastersizer 3000 laser particle size analyzer, which utilized the intensity distribution of laser diffraction. The volumetric cumulative particle size distribution, D, was determined using laser diffraction. 10 D represents the particle size at which the cumulative particle size distribution percentage of the powder reaches 10%. 50 D represents the particle size at which the cumulative particle size distribution percentage reaches 50%. 90This indicates the particle size corresponding to a cumulative particle size distribution percentage of 90%. Specifically, the particle size of the cathode material is measured using a Malvern MS 3000 laser particle size analyzer. An appropriate amount of sample is taken, poured into pure water, and ultrasonically dispersed for 30 seconds at a power of 240W. Then, an appropriate amount of sodium hexametaphosphate is added to the dispersed sample, stirred thoroughly, and poured into the sample cell of the testing equipment. After waiting 10 seconds, the sample testing is started.

[0177] The volumetric particle size distribution width of the cathode material = (D 90 -D 10 ) / D 50 .

[0178] (4) Specific surface area test of cathode material:

[0179] The specific surface area of ​​the material was calculated using a TriStar II surface area and porosity analyzer (USA) by adsorbing nitrogen and employing the BET method. Specifically, the mass of the empty sample tube was weighed (m1); 3g of sample was added to the sample tube through a long-necked funnel, and the tube was degassed under vacuum at 300℃ for 1 hour. After cooling, the mass of the sample tube was weighed (m2); the sample mass was calculated as m = m2 - m1. The sample tube was placed in liquid nitrogen, and the nitrogen adsorption capacity (V) of the sample was measured under a series of relative pressures (P / P0) to obtain adsorption isotherms. The P / P0 values ​​were set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. The isothermal adsorption curves were fitted, and the monolayer saturated adsorption capacity (Vm) was calculated based on the slope and intercept. The specific surface area was then calculated based on Vm.

[0180] (5) Morphological test:

[0181] The surface morphology and particle size of the samples were observed using a Hitachi S4800 scanning electron microscope to obtain SEM images of the cathode material. Specifically, five SEM images were taken at 3K magnification using the Hitachi S4800 scanning electron microscope at different positions, or five cross-sectional SEM images were taken at 3K magnification after sample preparation. The SEM images were imported into Nano Measure software, and random measurements were performed using Nano Measure software. The diameter of the circumcircle of the particle completely exposed in the field of view was taken as the particle diameter. At least 200 particles were counted, and the average value was taken as the average value of the particles. A particle completely exposed in the field of view of the SEM image is one whose outline is completely displayed in the SEM image, and whose outline is not covered by other single crystal particles in the field of view or divided by the boundaries of the SEM image.

[0182] (6) Tap density test of cathode material:

[0183] Test of 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.

[0184] (7) Compaction density test of cathode material:

[0185] The compaction density ρ2 of the powder was tested using a compaction density meter, with a pressure of 6t for 30s. Specifically, using a Carver 4350 compaction meter (USA), 1g of sample was placed in a mold and pressed with a pressure of 6t for 30s. After compaction, the height was measured to calculate the compaction density, which is the ratio of the sample mass to the compacted volume.

[0186] (8) Electrochemical performance was evaluated using coin half-cells:

[0187] The positive electrode material, conductive agent SP, and binder (PVDF adhesive) were mixed and homogenized in a mass ratio of 93:5:2. The slurry was then evenly coated onto a 16μm thick aluminum foil and dried in a 100℃ oven for 12 hours. The negative electrode used a 16mm diameter, 1mm thick Li metal sheet. The separator used a 20μm thick porous polyethylene membrane. The electrolyte was a mixture of equal volumes of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1mol / L LiPF6 as the electrolyte. The positive electrode, separator, negative electrode, and electrolyte were assembled into a 2016-type coin cell in an Ar glove box with a water and oxygen content of less than 5ppm.

[0188] Capacity testing procedure: The electrical performance was tested using the Blue Electric testing system (charge and discharge voltage of 2.8 to 4.4V, temperature condition of 25℃), with 0.1C charging, 0.1C discharging, and a constant voltage cutoff current of 0.005C. The discharge capacity C mAh / g was calculated based on the discharge capacity.

[0189] Cyclic test regime: 25℃, charge and discharge voltage of 2.8~4.4V, 0.5C charge and 1C discharge, 50 cycles, constant voltage cutoff current of 0.05C, the final capacity retention rate after 50 cycles is the cycle performance.

[0190] The test results of Examples 1 to 13 (abbreviated as S1 to S13) and Comparative Examples 1 to 4 (abbreviated as D1 to D4) prepared in this application are detailed in List 1 to Table 2.

[0191] Table 1 Physicochemical properties of cathode materials

[0192] Table 2 Electrochemical performance results of cathode materials

[0193] Figure 2 shows the SEM image of the cathode material prepared in Example 1. As can be seen from Figure 2, the number of agglomerates in the cathode material prepared in Example 1 is 0, the particles have high roundness and good dispersibility.

[0194] Figure 3 shows the SEM image of the cathode material prepared in Comparative Example 1. As can be seen from Figure 3, the cathode material prepared in Comparative Example 1 has a large number of agglomerates and low particle roundness.

[0195] According to the test data from the examples, mixing the oxide precursor, lithium source, dopant, and pore-forming agent, and adding the pore-forming agent, facilitates sufficient contact between the precursor and oxygen during sintering, accelerates the reaction rate, increases the porosity of the matrix material, reduces particle agglomeration, and significantly reduces the proportion of agglomerates in the cathode material. It also improves particle roundness. Furthermore, the segmented sintering process, with its shorter high-temperature sintering time, results in more uniform particle growth. The sintered matrix material undergoes a dissociation treatment, where some agglomerates of 2-3 particles can be re-dissociated into individual particles, reducing the proportion of agglomerates in the cathode material. Controlling the average aspect ratio of the particles in the cathode material within the range of 1-1.6 improves the particle tolerance and structural order of the cathode material, increasing its compaction density and capacity, and also enhancing its long-cycle performance.

[0196] Comparing Examples 2-6 with Examples 1, under the premise of maintaining the same process conditions, only changing the lithium source or different oxide precursors, the electrochemical performance of the prepared cathode material is still at a high level. The capacity and cycle performance of the cathode material are mainly affected by the Ni content. Furthermore, as the nickel content in the cathode material increases and the primary sintering temperature rises, the degree of particle agglomeration also increases slightly.

[0197] Compared with Example 7, after reducing the amount of sucrose used as a pore-forming agent, the degree of contact between oxygen and precursor materials during sintering was reduced, which affected particle growth, increased the aspect ratio α of the particles, reduced roundness, and improved the capacity of the cathode material. However, the cycle performance was slightly reduced after long-term cycling.

[0198] Compared with Example 8, after increasing the amount of sucrose used as a pore-forming agent, oxygen and precursor materials came into more sufficient contact during sintering, resulting in more rounded particle growth and a smaller aspect ratio α value. This indicates that the number of slender particles in the particles decreased, the particle size distribution width of the cathode material decreased, leading to a decrease in the compaction density of the cathode material, and a slight decrease in the overall capacity and cycle life of the cathode material.

[0199] Compared with Example 9, Example 1 showed that during the preparation process, the pulse sintering temperature decreased and the particle size D... 50 Compared to Example 1, the number of agglomerates in the cathode material is reduced, and the proportion of agglomerates in the cathode material is slightly increased, which slightly affects the capacity and cycle performance of the cathode material.

[0200] Compared with Example 10, in the preparation process, after the pulse sintering time was shortened, the particles did not grow sufficiently, resulting in a slight increase in the proportion of agglomerates in the cathode material, a wider particle size distribution of the cathode material, and a slight increase in the compaction density of the cathode material. However, the capacity and cycle performance of the cathode material were slightly reduced.

[0201] Compared with Example 11, Example 1 shows that different types of pore-forming agents can effectively alleviate the degree of particle agglomeration, reduce the proportion of agglomerates in the cathode material, and improve the roundness of particles, which is beneficial to improving the capacity and cycle stability of the cathode material.

[0202] Compared with Example 12, Example 1 did not contain any other metal elements doped or coated, and the roundness of the particles deteriorated and the aspect ratio increased during the growth process. Due to the lack of secondary sintering treatment, the cycle performance of the cathode material also decreased.

[0203] Compared with Comparative Example 1, Comparative Example 1 prepared a cathode material hydroxide precursor by co-precipitation. The roundness of the cathode material was reduced, the particle edges were obvious, and the degree of agglomeration was increased. It was easier to produce fine powder in the subsequent dissociation process, and the cycle performance of the cathode material was significantly reduced.

[0204] Compared with Comparative Example 2, Comparative Example 2, without the addition of a pore-forming agent, had an impact on the oxygen atmosphere of the oxide precursor particles during the sintering process. This resulted in an increase in the aspect ratio of the particles and a decrease in the roundness of the particles. Consequently, the local expansion stress of the particles was too large during cycling, making the particles prone to breakage. This increased the side reactions between the cathode material and the electrolyte and reduced the cycle retention rate of the cathode material.

[0205] Compared with Comparative Example 3, Example 1 uses ordinary sintering, which results in a decreased particle growth rate and oxygen atmosphere, a significant increase in particle aspect ratio, and a significant increase in agglomerates. Consequently, the capacity and cycle life of the cathode material are significantly reduced.

[0206] Compared with Comparative Example 4, the grinding air pressure and the fractionation frequency of the cathode material in Comparative Example 4 were lower during airflow pulverization, which resulted in some agglomerates not being effectively dissociated, leading to an increase in the proportion of agglomerates in the cathode material and a decrease in the capacity and cycle performance of the cathode material.

[0207] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized by, The cathode material includes multiple particles and aggregated particles; The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. The total number of particles in the SEM image of the cathode material is N, N≥200, of which the number of aggregate particles formed by the aggregation of 5 or more particles with a particle size <1μm is n. The proportion of the aggregates is β = n / N, β ≤ 1%; Randomly measure more than 200 particles in the SEM images. The average size of the longest diameter of the particles is D, the average size of the straight side that perpendicularly bisects the longest diameter of the particles is L, and the average aspect ratio of the particles is α = D / L, where 1 < α < 1.

6.

2. The positive electrode material of claim 1, wherein, The cathode material satisfies the condition 2.0 μm < D < 3.0 μm.

3. The cathode material of claim 1, wherein, The cathode material satisfies 1.5μm≤L≤2.5μm.

4. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) the positive electrode material has a chemical formula of Li k Ni a Co b N c M d O2, 0.98≤k≤1.1, 0.50≤a≤0.98, 0 b≤0.20, 0 c≤0.35, 0≤d≤0.10, a+b+c+d=1, N is Mn or Al, and M elements include metal elements other than Li, Ni, and Co; (2) the positive electrode material has a general chemical formula of Li k Ni a Co b N c M d O2, 0.98≤k≤1.1, 0.50≤a≤0.98, 0 N is Mn or Al, and the M element includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Ca, Y, B, Nb, W, Sb, Ta, Sn, Mo, La, and Ce.

5. The cathode material of claim 1, wherein, The cathode material satisfies at least one of the following conditions: (1) the volume median particle diameter D50 of the positive electrode material is 3.0 μm to 5.0 μm 50 3.0 μm to 5.0 μm; (2) the positive electrode material has a volume particle size distribution width that satisfies: 1.0 < (D 90 -D 10 ) / D 50 < 1.

5.

6. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) The cathode material is a single crystal material; (2) The particles include primary particles, and the primary particles have the same orientation; (3) The particles include primary particles, and the particle size of the primary particles is 1μm to 5μm.

7. The cathode material of claim 1, wherein, The specific surface area of the positive electrode material is Sm 2 / g, 0.5 < S < 0.

9.

8. The cathode material of claim 1, wherein, The tap density of the positive electrode material is ρ1 g / cm3 3 , 1.8 < ρ1 < 2.

5.

9. The cathode material of claim 1, wherein, The compacted density of the positive electrode material is ρ2 g / cm 3 , 3 < ρ2 < 3.

5.

10. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) The maximum length of the aggregate is less than 4 μm; (2) The maximum length of the aggregate is less than 6 μm.

11. The cathode material of claim 1, wherein, The mass content of residual alkali of the positive electrode material is m Li wt%, 0.10 < m Li <0.

25.

12. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) The average aspect ratio of the particles is α, which is any value within the range of 1.1, 1.2, 1.3, 1.4, 1.5 or any two of these values; (2)1＜α≤1.3； (3)1.1＜α≤1.5。 13. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) The percentage of aggregate particles β can be 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.3%, 0.2%, 0.1%, 0.05%, or any value within the range of any two of these values; (2)0％≤β≤0.3％； (3)0％≤β≤0.69％。 14. A positive electrode sheet characterized by comprising: The positive electrode sheet includes the positive electrode material as described in any one of claims 1 to 13.

15. A battery, characterized by The battery comprises the positive electrode material according to any one of claims 1 to 13 or the positive electrode sheet according to claim 14.

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