Positive electrode material and battery

Abstract

The present application relates to a positive electrode material and a battery. The positive electrode material comprises a plurality of particles; an SEM image of the positive electrode material is obtained by using a scanning electron microscope at a magnification of 3K, 200 particles in the SEM image are randomly measured, the average size of the longest diameters of individual particles is D, the average size of the wide diameters of the particles perpendicular to and bisecting the longest diameters is L, the average aspect ratio of the particles is α=D / L, and 1≤α≤1.6; moreover, the proportion of particles having a particle size less than 1 μm in the positive electrode material is R%, and 10≤R≤16. The positive electrode material in the present application has both high capacity and high energy density, and excellent long-cycle stability, particularly high-temperature cycle stability.

Description

Positive electrode materials and batteries Cross-reference to related applications

[0001] This application claims priority to Chinese patent application filed on December 26, 2024, with application number 202411976302.2 and entitled "Cathode Material and Battery". Technical Field

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

[0003] Lithium-ion batteries (LIBs) possess advantages such as high energy density, high power density, long cycle life, and low self-discharge, making them 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, cathode materials suffer from drawbacks such as high reactivity during battery reactions, easy reaction with electrolytes, leading to material gas generation, reduced cycle life, and decreased high-temperature storage performance. Therefore, improving cathode materials to achieve excellent capacity and energy density, and enhancing their long-cycle stability, remain urgent problems to be solved. Summary of the Invention

[0005] This application provides a cathode material and a battery. The cathode material of this application has both high capacity and energy density, as well as excellent long-term cycle stability, especially high-temperature cycle stability.

[0006] In a first aspect, this application provides a cathode material; the cathode material comprises a plurality of particles;

[0007] The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. 200 particles in the SEM image were randomly measured. The average size of the longest diameter of a single particle was D, the average size of the width diameter that perpendicularly bisects the longest diameter of the particle was L, and the average aspect ratio of the particles was α = D / L, where 1 ≤ α ≤ 1.6.

[0008] Furthermore, in the electron microscope image of the cathode material, the proportion of particles with a diameter less than 1 μm is R%, 10≤R≤16.

[0009] Secondly, this application provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material described in the first aspect.

[0010] Secondly, 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.

[0011] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0012] The cathode material of this application has an average aspect ratio of 1≤α≤1.6, indicating that the diameter difference of the particles in different directions is small. When the particles are subjected to stress, the stress difference in each direction is small, which is conducive to the uniform distribution of particle expansion stress, reduces local stress accumulation, and improves the structural stability and cycle capacity retention of the cathode material. However, within the above-mentioned average aspect ratio, the diameter difference of the particles in different directions becomes smaller, resulting in a narrowing of the volumetric particle size distribution of the cathode material, which leads to a decrease in the compaction density and capacity of the cathode material. Therefore, this application controls the proportion of 1μm particles at R%, 10≤R≤16, while controlling the average aspect ratio of the cathode material particles. Particles with a diameter less than 1μm can effectively fill the gaps between particles larger than 1μm, thereby ensuring the compaction density and capacity of the cathode material while controlling the aspect ratio. The average aspect ratio of the cathode material satisfying 1≤α≤1.6 can reduce particle breakage and improve the structural stability and long-cycle performance of the cathode material. With the synergistic effect of both, the cathode material has both high capacity and energy density, as well as excellent long-term cycling stability, especially high-temperature cycling stability. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application.

[0015] Figure 2 is a SEM image of the cathode material provided in Embodiment 1 of this application.

[0016] Figure 3 is a SEM image of the cathode material provided in Comparative Example 1 of this application.

[0017] Figure 4 is a comparison chart of the cycle performance of the cathode materials provided in Example 1 of this application with those in Comparative Examples 1 and 2. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] In a first aspect, this application provides a cathode material, the cathode material comprising a plurality of particles;

[0023] The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. 200 particles in the SEM image were randomly measured. The average size of the longest diameter of a single particle was D, the average size of the width diameter that perpendicularly bisects the longest diameter of the particle was L, and the average aspect ratio of the particles was α = D / L, where 1 ≤ α ≤ 1.6.

[0024] Furthermore, in the electron microscope image of the cathode material, the proportion of particles with a diameter less than 1 μm is R%, 10≤R≤16.

[0025] The cathode material of this application has an average aspect ratio of 1≤α≤1.6, indicating that the diameter difference of the particles in different directions is small. When the particles are subjected to stress, the anisotropy difference of the particles is small, which is conducive to the uniform distribution of particle expansion stress, reduces local stress accumulation, and improves the structural stability and cycle capacity retention of the cathode material. However, within the above-mentioned average aspect ratio, the diameter difference of the particles in different directions becomes smaller, which leads to a narrowing of the particle size distribution of the cathode material, resulting in a decrease in the compaction density and capacity of the cathode material. This application controls the proportion of 1μm particles to R%, 10≤R≤16, while controlling the average aspect ratio of the cathode material particles. Particles with a diameter less than 1μm can effectively fill the gaps between particles larger than 1μm, which can ensure the compaction density and capacity of the cathode material while controlling the aspect ratio of the particles. Particles with an average aspect ratio of 1≤α≤1.6 can reduce particle breakage of the cathode material under high compaction conditions and improve the structural stability and long cycle performance of the cathode material. With the synergistic effect of both, the cathode material has both high capacity and energy density, as well as excellent long-term cycling stability, especially high-temperature cycling stability.

[0026] It should be noted that when the average length and diameter of the cathode material particles is greater than 1.6, it means that the diameter of the particles varies greatly in different directions. During the rolling process of the cathode material into electrode sheets, the particles are squeezed against each other and stress is easily generated. Moreover, the stress difference in each direction is large, which leads to the formation of cracks on the particles, resulting in an increase in the specific surface area of ​​the cathode material, an increase in the number of active sites, and an increase in side reactions with the electrolyte.

[0027] In some embodiments, the general chemical formula of the cathode material is Li. x Ni a Co b N c M d O2, 0.98≤x≤1.1, 0.50≤a≤0.98, 0<b≤0.40, 0<c≤0.4, 0≤d≤0.10, N is Mn or Al, M is a metallic element.

[0028] The specific values ​​of x 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, 0.15, 0, etc. The values ​​of c can be 0.16, 0.2, 0.25, 0.3, 0.35, or 0.4, etc., and the values ​​of d can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.16, 0.2, 0.25, 0.3, 0.35, or 0.4, etc., and the values ​​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 any restrictions here.

[0029] In some embodiments, the M element includes at least one selected from Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y. Understandably, appropriate M element doping can improve the lattice structure stability of the cathode material and reduce lithium-nickel mixing.

[0030] In some embodiments, the average aspect ratio of the particles satisfies 1 ≤ α ≤ 1.6, specifically 1, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, or 1.6, etc., and of course, other values ​​within the above range are also possible, without limitation. Optionally, 1.08 ≤ α ≤ 1.37. Optionally, 1.1 ≤ α ≤ 1.4. Optionally, 1.2 ≤ α ≤ 1.6. When the average aspect ratio of the particles is within the above range, the diameter difference of the particles in different directions is small. When the particles are subjected to stress, the stress difference in each direction of the particles is small, which is beneficial to reduce the uniform distribution of particle expansion stress, reduce local stress accumulation, and improve the structural stability and cycle capacity retention rate of the cathode material.

[0031] It should be noted that the average aspect ratio of the particles refers to the average of the aspect ratios of 200 particles that are randomly and completely visible in the electron microscope image field of view. A particle that is completely visible in the electron microscope image field of view means that the particle's outline is fully displayed in the electron microscope image, and its outline is not covered by other particles in the field of view or divided by the boundaries of the electron microscope image. The longest diameter refers to the diameter line whose two ends lie on the particle's outline within the particle's circumcircle. The widest diameter refers to the diameter perpendicular to the midpoint of the longest diameter and whose two ends lie on the particle's outline.

[0032] In some implementations, 1 μm < D < 5 μm, and 1 μm < L < 5 μm. Specifically, the value of D can be 1.1 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, or 4.9 μm, or other values ​​within the aforementioned range; no limitation is imposed here. Similarly, the value of L can be 1.1 μm, 1.5 μm, 2.0 μm, 2.5 μm, 3.0 μm, 3.5 μm, 4.0 μm, or 4.9 μm, or other values ​​within the aforementioned range; no limitation is imposed here.

[0033] In some embodiments, the percentage R% of particles with a diameter less than 1 μm in the cathode material satisfies 10 ≤ R ≤ 16. Specifically, the percentage R% of particles with a diameter less than 1 μm in the cathode material can be 10, 11, 12, 13, 14, 15, 16, or any two of the above values. Optionally, 10 ≤ R ≤ 14. Optionally, 11 ≤ R ≤ 14. Thus, particles smaller than 1 μm can effectively fill the gaps between particles larger than 1 μm, ensuring the compaction density and capacity of the cathode material while controlling the aspect ratio of the particles.

[0034] In some embodiments, in the cathode material, the proportion of particles with an aspect ratio satisfying 1≤α≤1.6 is P%, P≥90, specifically 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, etc., and other values ​​within the above range are also possible, without limitation. Understandably, the higher the proportion of particles with an aspect ratio satisfying 1≤α≤1.6, the lower the proportion of elongated particles in the cathode material, which is beneficial for the uniform dispersion of particle expansion stress and for maintaining isotropic lithium-ion insertion / extraction rates, thus improving the rate performance and cycle capacity retention of the cathode material. It should be noted that particles with a diameter less than 1μm can also satisfy 1≤α≤1.6. These small, rounded particles can fill the spaces between larger particles, increasing the compaction density of the cathode material and thereby improving the energy density of the battery.

[0035] In some embodiments, the volume median particle size D50 of the cathode material is 2.0 μm to 6.0 μm, specifically 2.0 μm, 3.0 μm, 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, or 6.0 μm, etc., and of course, other values ​​within the above range are also possible, and are not limited here. Because the volume median particle size of the cathode material is within the above range, particles within this size range have better electrochemical performance, higher discharge capacity, and excellent rate performance.

[0036] In some embodiments, the volumetric particle size distribution width of the cathode material satisfies: 1.0 < (D 90 -D 10 ) / D 50 The value ≤2 can specifically be 1.05, 1.08, 1.1, 1.15, 1.18, 1.2, 1.22, 1.25, 1.26, 1.3, 1.35, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2, etc., and can also be other values ​​within the above range, which are not limited here. This application controls the particle size distribution width of the positive electrode material within the above range, so that particles of different sizes can achieve a more compact stacking, thereby improving the compaction density of the positive electrode sheet and the energy density.

[0037] In some embodiments, the cathode material is a single-crystal material, and the particles include primary particles with a particle size of 1 μm to 5 μm.

[0038] 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.

[0039] 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.

[0040] 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 imposed by impurities, strain, and crystal defects, ideal single crystals are extremely rare and difficult to produce in the laboratory. Therefore, the single-crystal cathode materials known in the art are actually more often "single-crystal-like" cathode materials, which differ from polycrystalline materials composed of numerous small primary particles only in size, exhibiting a large particle size similar to single crystals.

[0041] In some implementations, the specific surface area of ​​the cathode material is 0.4 m². 2 / g~0.8m 2 / g. Specifically, it can be 0.4m 2 / g, 0.45m 2 / g, 0.5m 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m2 / g, 0.7m 2 / g, 0.75m 2 / g or 0.8m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Thanks to the improved particle roundness in the cathode material, the specific surface area of ​​the cathode material can be controlled within the above range, which can effectively reduce the side reactions between the cathode material and the electrolyte and improve the capacity of the cathode material.

[0042] In some embodiments, the tap density of the cathode material is ρ1g / cm³. 3 1.5 ≤ ρ1 < 2.2, specifically 1.91 g / cm³ 3 1.95g / cm 3 2.0g / cm 3 2.1g / cm 3 2.3g / cm 3 2.4g / cm 3 2.5g / cm 3 2.6g / cm 3 Or 2.69 g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0043] In some embodiments, the compaction density of the cathode material is ρ² g / cm³. 3 3.0 ≤ ρ² < 3.5. Specifically, it could be 3.0 g / cm³. 3 3.1g / 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 Or 3.49 g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0044] In some embodiments, the cathode material satisfies 11 ≤ pH ≤ 12, specifically 11, 11.2, 11.5, 11.7, 11.8, 11.9, or 12, but is not limited to the listed values; other unlisted values ​​within this range also apply. Understandably, the surface alkaline impurities of the cathode material mainly refer to Li₂CO₃ and LiOH. Maintaining the pH value of the cathode material within the above range can reduce gas generation during cycling, protect the structural stability of the cathode material, and improve its cycle stability.

[0045] In some embodiments, the coin cell made of the positive electrode material has a capacity retention rate of ≥95% after 50 cycles at 55°C. Specifically, it can be 95%, 95.5%, 95.8%, 96.2%, 96.5%, 97.0%, 97.5%, 98.0%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Secondly, this application provides a method for preparing the above-mentioned cathode material, comprising the following steps:

[0047] Step S100: The precursor, lithium salt and dopant are mixed to obtain a first mixture, wherein the dopant includes at least one of the compounds of Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y.

[0048] In some embodiments, the precursor has the general chemical formula Ni. x Co y N z O2, where 0.6≤x≤0.98, 0<y≤0.4, 0<z≤1-xy, and N is Mn or Al.

[0049] In some embodiments, the precursor has the general chemical formula Ni. x Co y N z (OH)2, where 0.6≤x≤0.98, 0<y≤0.4, 0<z≤1-xy, and N element is Mn or Al.

[0050] In some embodiments, the median particle size of the precursor is 2.0 μm to 4.0 μm, specifically 2.0 μm, 2.3 μm, 2.5 μm, 3.0 μm, 3.5 μm, 3.8 μm, 3.9 μm or 4.0 μm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] In some embodiments, the dopant may be an oxide, salt, or other form of the aforementioned element, and is not limited thereto.

[0052] In some embodiments, based on the mass of the nickel-cobalt-manganese-based oxide precursor, the amount of dopant added is 0.05% to 0.5%, specifically 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.12%, 0.15%, 0.2%, 0.25%, 0.28%, 0.3%, 0.4%, or 0.5%, 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 primary particles in the cathode material, thereby improving the capacity and particle structure stability of the cathode material.

[0053] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium chloride, lithium nitrate, and lithium oxalate.

[0054] In some embodiments, the ratio of the molar amount of Li in the first mixture to the total molar amount of the transition metal in the precursor is controlled to be 0.98 ≤ n. Li / n Me ≤1.1; specifically, it can be 0.98:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.08:1 or 1.1:1, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0055] In some implementations, 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.

[0056] In some implementations, mixing includes low-speed mixing, medium-speed mixing, and high-speed mixing. By gradually increasing the mixing speed, it is possible to ensure that the components are mixed evenly, which is beneficial to improving the distribution uniformity of nickel-cobalt-manganese-based oxide precursors, lithium sources, and dopants, and to reducing structural defects in cathode materials and improving the structural order of cathode materials.

[0057] Step S200: The first mixture is subjected to pre-oxidation sintering treatment under an oxygen-containing atmosphere to obtain a pre-oxidized composite.

[0058] In some embodiments, the first mixture is pressed into a slab material and then perforated, with the spacing between the perforations controlled to be less than 1 cm.

[0059] In some embodiments, the temperature of the pre-oxidation sintering treatment is 500℃ to 900℃, specifically 500℃, 550℃, 570℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0060] In some embodiments, the environmental pressure during the pre-oxidation sintering treatment 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.

[0061] In some embodiments, the pre-oxidation sintering treatment time is 2h to 8h, specifically 2h, 3h, 4h, 5h, 6h, 7h or 8h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0062] In this application, the first mixture is first subjected to pre-oxidation sintering treatment. By controlling the pressure, temperature and time, lithium salt can act as a flux to make the various components mix more uniformly. The lithium ions in the lithium salt can be embedded in the precursor to improve the roundness of the precursor particles. At the above temperature, most of the lithium salt can be embedded in the precursor, which can reduce the residue of lithium salt and reduce the generation of fine powder, thus obtaining a pre-oxidized composite.

[0063] In step S300, the pre-oxidized composite is mixed with an oxygen supplement to obtain a second mixture, and the second mixture is subjected to a single pulse sintering in an oxygen-containing atmosphere to obtain a matrix material. The single pulse sintering 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.

[0064] In some embodiments, the oxygen supplement includes at least one of lithium peroxide, sodium peroxide, sodium perborate, and potassium permanganate. Understandably, the oxygen supplement can decompose at high temperatures to generate oxygen. Because the oxygen supplement is thoroughly mixed with the pre-oxidized composite, it can fill the spaces between the pre-oxidized composite particles, providing additional oxygen during the subsequent single-pulse sintering process, which is beneficial for the complete oxidation of all components.

[0065] In some embodiments, the amount of oxygen supplement added is 0.5% to 1% based on 100% of the mass of the pre-oxidized compound. Specifically, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] Understandably, the pre-oxidized composite particles are relatively compact, making it difficult for oxygen to penetrate during the first pulse sintering process. Therefore, an oxygen supplement is added. The oxygen supplement decomposes at high temperature to produce oxygen, and has few byproducts. It can provide the oxygen required for the pre-oxidized composite to continue to be fully oxidized from inside the second mixture, making the first pulse sintering more complete and improving the structural stability of the matrix material.

[0067] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥90%.

[0068] In some embodiments, the heating rate of a single pulse sintering 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.

[0069] In some implementations, the ambient pressure during a single 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.

[0070] In some embodiments, during a single 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.

[0071] In some implementations, during a single pulse sintering process, the holding time in the first stage is 1 to 2 hours, specifically 1.0 hour, 1.2 hours, 1.5 hours, or 2 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0072] In some implementations, during a single pulse sintering process, 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.

[0073] In some implementations, during a single pulse sintering process, the holding time in the second stage is 1 to 2 hours, specifically 1.0 hour, 1.2 hours, 1.5 hours, or 2 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0074] In some embodiments, during a single pulse sintering process, the total holding time for controlling temperature T1 is 4 to 8 hours, specifically 4.0 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, or other values ​​within the above range, which are not limited here. The total holding time for controlling temperature T2 is 4 to 8 hours, specifically 4.0 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, or other values ​​within the above range, which are not limited here.

[0075] In some embodiments, during a single pulse sintering process, the sintering temperature T4 of 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.

[0076] 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.

[0077] During a single pulse sintering process, controlling the temperature and time of the fourth stage within the aforementioned range can promote the repair of the primary grain boundary surface of the cathode material, thereby improving the particle tolerance and structural order of the cathode material.

[0078] In step S300, the matrix material is subjected to micron-level particle dissociation treatment. After the dissociation products are mixed with the coating agent, a secondary sintering treatment is performed to obtain the cathode material.

[0079] In some embodiments, the dissociation process includes at least one of air jet milling and grinding.

[0080] In some embodiments, the grinding air pressure during air jet milling is in the range of 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, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0081] In some embodiments, the classifying frequency during air jet milling 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.

[0082] In some embodiments, the average aspect ratio of the matrix material after dissociation treatment is 1-1.6, and the proportion of particles with a diameter of less than 1 μm identified under 3K electron microscopy is 10%-16%.

[0083] In some embodiments, the amount of coating agent added is 0.05% to 0.4% based on 100% of the mass of the matrix material. Specifically, it can be 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 is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In some embodiments, the coating agent comprises a compound containing element M, wherein element M includes at least one compound selected from B, Al, Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn, and Y.

[0085] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥95%.

[0086] In some embodiments, the temperature of the secondary sintering treatment is 500℃ to 900℃, specifically 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0087] In some embodiments, the secondary sintering treatment time is 6h to 16h, specifically 6h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 11h, 12h, 13h, 14h, 15h or 16h, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0088] In some embodiments, during the secondary sintering process, the ambient pressure 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.

[0089] 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.

[0090] 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.

[0091] In other embodiments, the secondary battery may also be a steel-cased battery, an aluminum-cased battery, etc.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] Example 1

[0101] (1) Weigh out the chemical formula Ni 0.6 Co 0.1 Mn 0.3 2.5 kg of (OH)2 precursor and 1.2 kg of LiOH were used. Based on the mass of the precursor, 0.3% ZrO2, 0.1% Al2O3, and 0.1% Sr(OH)2 were weighed and added to a high-speed mixer. After the addition was complete, the high-speed mixer was turned on and mixed at low speed (300 rpm) for 5 min, medium speed (800 rpm) for 10 min, and high speed (1500 rpm) for 15 min to obtain the first mixture.

[0102] (2) Place the first mixture in a sintering vessel and press it with a pressure of about 1t to make the material clump together; punch holes in the pressed material, and the distance between the holes should be less than 1cm; place the punched material in a kiln and perform pre-oxidation sintering treatment in an oxygen atmosphere. The pre-oxidation sintering temperature is 600℃, the furnace pressure is about 50Pa, and the pre-oxidation sintering time is 5h to obtain the pre-oxidized composite.

[0103] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added is 1% based on the mass of the pre-oxidized composite) are mixed for 10 min under nitrogen protection to obtain a second mixture; the second mixture is placed in a kiln and subjected to a single pulse sintering under an oxygen atmosphere at a furnace pressure of 50 Pa; the single pulse sintering steps include 960℃-2h→930℃-2h→960℃-2h→930℃-2h→960℃-2h→930℃-2h→960℃-2h→930℃-2h→920℃-4h to obtain the single sintering product.

[0104] (4) The sintered product is subjected to air jet milling at a pressure of 0.65 MPa and a grading frequency of 45 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 3.0 μm ≤ D50 ≤ 3.4 μm.

[0105] (5) The matrix material is mixed with 0.1% tungsten oxide and 0.1% titanium oxide under nitrogen atmosphere protection to obtain a third mixture. The third mixture is placed in a kiln and sintered in an oxygen atmosphere. The secondary sintering temperature is controlled at 500℃, the furnace pressure is about 50Pa, and the secondary sintering time is 10h to obtain the cathode material.

[0106] Figure 2 is a SEM image of the cathode material provided in Example 1 of this application. As shown in Figure 2, the general chemical formula of the cathode material prepared in this example is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0107] Example 2

[0108] Unlike Example 1:

[0109] In step (1), the precursor has the general formula Ni. 0.5 Co 0.2 Mn 0.3 (OH)2.

[0110] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.50 Co 0.2 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0111] Example 3

[0112] Unlike Example 1:

[0113] In step (1), the precursor has the general formula Ni. 0.7 Co 0.1 Mn 0.2 (OH)2.

[0114] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.70 Co 0.1 Mn 0.2 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0115] Example 4

[0116] Unlike Example 1:

[0117] In step (1), the precursor has the general formula Ni. 0.6 Co 0.1 Mn 0.3 O2, the lithium salt used is anhydrous LiOH.

[0118] (4) The sintered product is subjected to air jet milling at a pressure of 0.70 MPa and a classification frequency of 45 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 2.9 μm ≤ D50 ≤ 3.3 μm.

[0119] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0120] Example 5

[0121] Unlike Example 1:

[0122] In step (1), the precursor has the general formula Ni. 0.8 Co 0.1 Mn 0.1 (OH)2.

[0123] (4) The sintered product is subjected to air jet milling at a pressure of 0.70 MPa and a classification frequency of 45 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 2.9 μm ≤ D50 ≤ 3.3 μm.

[0124] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.80 Co 0.1 Mn 0.1 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0125] Example 6

[0126] Unlike Example 1:

[0127] In step (1), the precursor has the general formula Ni. 0.98 Co 0.01 Mn 0.01 (OH)2.

[0128] (4) The sintered product is subjected to air jet milling at a pressure of 0.70 MPa and a classification frequency of 45 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 2.9 μm ≤ D50 ≤ 3.3 μm.

[0129] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.98 Co 0.01 Mn 0.01 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0130] Example 7

[0131] Unlike Example 1:

[0132] (2) Place the first mixture in a sintering vessel and press it with a pressure of about 1t to make the material slab; punch holes in the pressed material, the distance between the holes should be less than 1cm; place the punched material in a kiln and perform pre-oxidation sintering treatment in an oxygen atmosphere. The pre-oxidation sintering temperature is 700℃, the furnace pressure is about 50Pa, and the pre-oxidation sintering time is 8h to obtain the pre-oxidized composite.

[0133] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0134] Example 8

[0135] Unlike Example 1:

[0136] (1) Weigh out the chemical formula Ni 0.6 Co 0.1 Mn 0.3 2.5 kg of (OH)2 precursor and 1.2 kg of LiOH were used. Based on the mass of the precursor, 0.3% ZrO2, 0.1% Al2O3, 0.1% Sr(OH)2, and 0.05% WO3 were weighed out respectively. They were added to a high-speed mixer. After the addition was complete, the high-speed mixer was turned on and mixed at low speed (300 rpm) for 5 min, medium speed (800 rpm) for 10 min, and high speed (1500 rpm) for 15 min to obtain the first mixture.

[0137] (2) Place the first mixture in a sintering vessel and press it with a pressure of about 1t to make the material clump together; punch holes in the pressed material, and the distance between the holes should be less than 1cm; place the punched material in a kiln and perform pre-oxidation sintering treatment in an oxygen atmosphere. The pre-oxidation sintering temperature is 700℃, the furnace pressure is about 50Pa, and the pre-oxidation sintering time is 2h to obtain the pre-oxidation composite.

[0138] 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 the doping elements are Zr, Al, Sr and W, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0139] Example 9

[0140] Unlike Example 1:

[0141] In step (1), weigh out the sample with the general chemical formula Ni. 0.6 Co 0.1 Al 0.3 2.5 kg of (OH)2 precursor and 1.2 kg of LiOH were used. Based on the mass of the precursor, 0.3% ZrO2 and 0.1% Sr(OH)2 were weighed and added to a high-speed mixer. After the addition was complete, the high-speed mixer was turned on and mixed at low speed (300 rpm) for 5 min, medium speed (800 rpm) for 10 min, and high speed (1500 rpm) for 15 min to obtain the first mixture.

[0142] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Al 0.3 O2, in which the doping elements are Zr and Sr, are not shown in the chemical formula because the amount of doping elements is difficult to determine precisely.

[0143] Example 10

[0144] Unlike Example 1, in step (3), the pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added based on the mass of the pre-oxidized composite is 1%) are mixed for 10 min under nitrogen protection to obtain a second mixture; the second mixture is placed in a kiln and subjected to a single pulse sintering under an oxygen atmosphere with a furnace pressure of 50 Pa; the single pulse sintering steps include 960℃-4h→930℃-4h→960℃-4h→930℃-4h→920℃-4h to obtain the single sintering product.

[0145] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0146] Example 11

[0147] Unlike Example 1:

[0148] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added based on the mass of the pre-oxidized composite is 1%) are mixed for 10 min under nitrogen protection to obtain a second mixture; the second mixture is placed in a kiln and subjected to a single pulse sintering under an oxygen atmosphere at a furnace pressure of 50 Pa; the single pulse sintering steps include 960℃-1h→930℃-1h→960℃-1h→930℃-1h→960℃-1h→930℃-1h→960℃-1h→930℃-1h→960℃-1h→930℃-1h→960℃-1h→930℃-1h→960℃-1h→930℃-1h→920℃-4h to obtain the single sintering product.

[0149] (4) The sintered product is subjected to air jet milling at a pressure of 0.70 MPa and a grading frequency of 50 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 3.0 μm ≤ D50 ≤ 3.4 μm.

[0150] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0151] Example 12

[0152] Unlike Example 1:

[0153] (3) The pre-oxidized composite and the oxygen supplement (sodium peroxide, with the amount of lithium peroxide added based on the mass of the pre-oxidized composite being 0.5%) were mixed under nitrogen protection for 10 min to obtain a second mixture; the second mixture was placed in a kiln and subjected to a single pulse sintering under an oxygen atmosphere at a furnace pressure of 50 Pa; the single pulse sintering steps included 960℃-2h→930℃-2h→960℃-2h→930℃-2h→960℃-2h→930℃-2h→960℃-2h→930℃-2h→920℃-4h to obtain the single sintering product.

[0154] (4) The sintered product is subjected to air jet milling at a pressure of 0.75 MPa and a classification frequency of 55 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 3.0 μm ≤ D50 ≤ 3.4 μm.

[0155] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0156] Example 13

[0157] (1) Weigh out the chemical formula Ni 0.6 Co 0.1 Al 0.3 2.5 kg of (OH)2 precursor and 1.2 kg of LiOH were added to a high-speed mixer. After the addition was complete, the high-speed mixer was turned on and mixed at low speed (300 rpm) for 5 min, medium speed (800 rpm) for 10 min, and high speed (1500 rpm) for 15 min to obtain the first mixture.

[0158] (2) Place the first mixture in a sintering vessel and press it with a pressure of about 1t to make the material clump together; punch holes in the pressed material, and the distance between the holes should be less than 1cm; place the punched material in a kiln and perform pre-oxidation sintering treatment in an oxygen atmosphere. The pre-oxidation sintering temperature is 600℃, the furnace pressure is about 50Pa, and the pre-oxidation sintering time is 5h to obtain the pre-oxidized composite.

[0159] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added is 1% based on the mass of the pre-oxidized composite) are mixed for 10 min under nitrogen protection to obtain a second mixture; the second mixture is placed in a kiln and subjected to a single pulse sintering under an oxygen atmosphere at a furnace pressure of 50 Pa; the single pulse sintering steps include 950℃-2h→920℃-2h→950℃-2h→920℃-2h→950℃-2h→920℃-2h→910℃-4h to obtain the single sintering product.

[0160] (4) The primary sintering product is subjected to airflow pulverization at a pressure of 0.65 MPa and a grading frequency of 45 Hz to obtain the positive electrode material.

[0161] The general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Al 0.3 O2.

[0162] Comparative Example 1

[0163] Unlike Example 1:

[0164] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added based on the mass of the pre-oxidized composite is 1%) are mixed under nitrogen protection for 10 min to obtain a second mixture; the second mixture is placed in a kiln and sintered once under an oxygen atmosphere at a furnace pressure of 50 Pa; the first sintering temperature is 970 °C and the first sintering time is 12 h to obtain the first sintered product.

[0165] Figure 3 shows the SEM morphology of the cathode material provided in Comparative Example 1 of this application. As shown in Figure 3, the general chemical formula of the cathode material prepared in this embodiment is LiNi. 0.60 Co 0.1 Mn 0.3 O2, in which the doping elements are Zr, Al and Sr, and the coating elements are W and Ti. Since the amount of doping and coating elements is difficult to determine precisely, it is not reflected in the chemical formula.

[0166] Comparative Example 2

[0167] Unlike Example 1:

[0168] (3) The pre-oxidized composite was placed in a kiln and sintered once in an oxygen atmosphere at a furnace pressure of 50 Pa. The sintering temperature was 950 °C and the sintering time was 8 h to obtain the sintered product.

[0169] Comparative Example 3

[0170] Unlike Example 1:

[0171] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added based on the mass of the pre-oxidized composite is 1%) are mixed under nitrogen protection for 10 min to obtain a second mixture; the second mixture is placed in a kiln and sintered once under an oxygen atmosphere at a furnace pressure of 50 Pa; the first sintering temperature is 980℃ and the first sintering time is 12 h to obtain the first sintered product.

[0172] (4) The sintered product is subjected to air jet milling at a pressure of 0.8 MPa and a classification frequency of 55 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 2.9 μm ≤ D50 ≤ 3.3 μm.

[0173] Comparative Example 4

[0174] The difference from Example 13 is:

[0175] (2) The first mixture was placed in a kiln and pre-oxidized and sintered in an oxygen atmosphere. The pre-oxidation and sintering temperature was 600℃, the furnace pressure was about 50Pa, and the pre-oxidation and sintering time was 5h to obtain the pre-oxidized composite.

[0176] (3) The pre-oxidized composite and the oxygen supplement (lithium peroxide, the amount of lithium peroxide added based on the mass of the pre-oxidized composite is 1%) are mixed under nitrogen protection for 10 min to obtain a second mixture; the second mixture is placed in a kiln and sintered once under an oxygen atmosphere at a furnace pressure of 50 Pa; the first sintering temperature is 950 °C and the first sintering time is 12 h to obtain the first sintered product.

[0177] (4) The sintered product is subjected to air jet milling at a pressure of 0.8 MPa and a classification frequency of 55 Hz to obtain the matrix material. The median particle size D50 of the matrix material is 2.8 μm ≤ D50 ≤ 3.2 μm.

[0178] Test method:

[0179] (1) Particle distribution test of cathode material:

[0180] SEM images of the cathode material were obtained using a scanning electron microscope (Hitachi S4800) at 3K magnification. The particle size within the SEM images was measured using Nana Measure software. 200 particles that appeared completely within the SEM images were randomly measured. The average length diameter of each particle was denoted as D, and the average width diameter perpendicular to the longest diameter was denoted as L. The average aspect ratio of the particles was α = D / L. A particle appearing completely within the field of view of the electron microscope image is defined as one whose outline is fully visible in the image, without being obscured by other particles or divided by the boundaries of the image. It should also be noted that the longest diameter refers to the diameter line within the circumcircle of the particle whose ends lie on the particle's outline. The width diameter refers to the straight line perpendicular to the midpoint of the longest diameter and whose ends lie on the particle's outline.

[0181] (2) The proportion of particles with a diameter of less than 1 μm in the cathode material

[0182] Equipment: Hitachi S4800 scanning electron microscope

[0183] 1) Use a cotton swab to pick up a small amount of powder sample and spread it evenly and densely on the conductive adhesive; use a hair dryer to slowly blow it in the direction where there are no other samples, and when you are sure that it is evenly spread on the surface, blow it strongly more than 10 times until there is no powder residue.

[0184] 2) Set the basic SEM conditions: voltage 5kV, current 12mA, magnification 2kx, adjust contrast and brightness using the auto key, and randomly select 10 areas with 400 to 1200 particles to take SEM images.

[0185] 3) Import the electron microscope image obtained in step (2) into the Metis Vision software, click "Identify All" in the software interface to obtain the particle size distribution data and particle size distribution map in the electron microscope image, thereby obtaining the proportion R of particles with a particle size of less than 1 μm in the cathode material.

[0186] (3) Testing of metallic elements in the cathode material:

[0187] Dissolve 0.3g of the sample to be tested in aqua regia, cool and bring the volume to 100ml to prepare the test stock solution; take 1mL of the test stock solution and dilute it 100 times to obtain the diluted solution. The diluted solution is used to test the content of the main elements Li, Ni, Co and Mn, while the stock solution is used to test the content of other elements such as dopants. All measurements are performed using an Agilent 5110ICP-OES detection instrument.

[0188] (4) 24-hour gas production value test:

[0189] The positive electrode was prepared by mixing the positive electrode material with binder, conductive agent and carbon nanotubes in a mass ratio of 96:2:1.5:0.5. The negative electrode was prepared by mixing graphite with conductive agent and binder in a mass ratio of 95.4:1.2:3.4. The separator was a Cellgard separator. The electrolyte was a mixture of equal parts of ethylene carbonate (EC), polycarbonate (PC) and diethyl carbonate (DEC) with 1 mol / L LiPF6 as electrolyte. The cells were assembled into a 2Ah soft pack battery. The gas production was tested by the water displacement method over 24 hours.

[0190] (5) Particle size test:

[0191] 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%. 90 This indicates the particle size corresponding to a cumulative particle size distribution percentage of 90%.

[0192] The volumetric particle size distribution width of the cathode material = (D 90 -D 10 ) / D 50 .

[0193] Specifically, take an appropriate amount of sample, pour it into pure water and ultrasonically disperse it evenly. Then, add an appropriate amount of sodium hexametaphosphate (powder: surfactant = 1g: 1 drop) to the dispersed sample, stir evenly, and pour it into the sample cell of the testing equipment. After waiting for 10 seconds, click "Start" to begin sample testing.

[0194] (6) Specific surface area test:

[0195] The specific surface area of ​​the material was calculated using a TriStar II surface area and porosity analyzer from the United States, by adsorbing the specific surface area of ​​the material with nitrogen and then calculating it using the BET method.

[0196] Specifically: Finished product pretreatment: Weigh the mass of the empty sample tube m1; take 3g of sample, degas it under vacuum at 300℃ for 1h, and weigh the sample tube after cooling to get the mass m2; sample mass m = m2 - m1.

[0197] Sample testing: The sample tube was placed in liquid nitrogen, and the amount of nitrogen adsorbed, V, was measured at 6 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.

[0198] Fit the isothermal adsorption curve and calculate the monolayer saturated adsorption capacity Vm based on the slope and intercept; calculate the specific surface area of ​​the cathode material based on Vm.

[0199] (7) Morphological test:

[0200] 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. The average particle size of the cathode material was measured using Nano Measurer software. The specific method is as follows: morphology analysis of the single-crystal material was performed using a scanning electron microscope. Random measurements of particles in the SEM at 3000x magnification were performed using Nano Measurer software, and the diameter of the circumscribed circle was taken as the particle size. At least 200 particles were counted, and the average value was taken.

[0201] (8) Tap density test of cathode material:

[0202] 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.

[0203] (9) Compaction density test of cathode material:

[0204] The compaction density ρ2 of the powder was tested using a compaction density meter (Carver 4350.22, USA). 1g of sample was weighed and placed in the mold and pressed with a pressure of 6T for 30s. After pressing, the height was measured and the compaction density was calculated.

[0205] (10) Electrochemical performance was evaluated using coin half-cells:

[0206] The positive electrode material, conductive agent SP, and binder (5% 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 gas glove box with a water and oxygen content of less than 5ppm.

[0207] Capacity testing procedure: The electrical performance was tested using the Blue Electric testing system (charge and discharge voltage of 3.0 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 and the initial capacity were calculated based on the discharge capacity.

[0208] Cyclic testing regime: At 55℃ and a charge / discharge voltage of 3.0–4.4V, the cells are charged and discharged at a 1C rate for 50 cycles. The ratio of the final capacity to the initial capacity after 50 cycles is the 50-cycle capacity retention rate, which is the high-temperature cycling performance. It should be noted that the cutoff current for the capacity test is the same as the constant voltage cutoff current in the above capacity testing regime.

[0209] The cathode materials of the above embodiments (abbreviated as S1 to S13) and comparative examples (abbreviated as D1 to D3) were subjected to physicochemical and electrochemical tests, and the test results are shown in Table 1 and Table 2 below.

[0210] Table 1: Physicochemical properties of cathode materials

[0211] Table 2: Electrochemical performance results of cathode materials

[0212] According to the test data from Examples 1-13, controlling the average aspect ratio of the cathode material particles to satisfy 1≤α≤1.6 and controlling the proportion of 1μm particles to satisfy 10≤R≤16 allows particles smaller than 1μm to effectively fill the spaces between particles larger than 1μm. By controlling the aspect ratio, the compaction density and capacity of the cathode material are maintained. An average aspect ratio of 1≤α≤1.6 reduces particle breakage and improves the structural stability and long-cycle performance of the cathode material. Through the synergistic effect of these two factors, the cathode material exhibits both high capacity and energy density, as well as excellent long-cycle stability, especially high-temperature cycle stability.

[0213] According to the test data from Examples 1 and 2-6, the capacity of the cathode material gradually increases with the increase of nickel content. Appropriate control of the single-pulse sintering temperature helps improve the roundness of the cathode material particles, allowing the aspect ratio to be controlled within the range of 1-1.6, resulting in more stable cycle performance. In Example 6, the cathode material had the highest nickel content, leading to increased lattice distortion and decreased structural stability, thus reducing the cycle capacity retention rate.

[0214] According to the test data of Examples 1 and 7, as the pre-oxidation sintering temperature and time increase, lithium ions can be fully embedded in the pre-oxidation composite to form a stable lithium nickel cobalt manganese oxide compound. After the lithium ions are fully embedded, during a single pulse sintering, the adhesion between particles caused by lithium salt as a flux can be effectively avoided, making the particles of the sintered matrix material more rounded and dispersed, and the cathode material has excellent cycle performance and capacity performance.

[0215] According to the test data of Examples 1 and 8, due to the shortening of the pre-oxidation sintering time, some lithium salts can act as fluxes, resulting in more particle adhesion. This leads to an increase in the aspect ratio of the particles, a decrease in the roundness of the particles, and some particles are prone to breakage during the electrode rolling process. This results in an increase in the side reactions between the cathode material and the electrolyte, and a decrease in the capacity and cycle retention rate of the cathode material compared to Example 1.

[0216] According to the test data of Examples 1 and 9, since the cathode material prepared in Example 9 is a lithium nickel cobalt aluminum oxide compound, the discharge capacity of the cathode material is slightly reduced, but the cycle capacity retention rate of the cathode material can be maintained at a high level.

[0217] According to the test data of Examples 1 and 11, the number of repetitions of the first and second stages during a single pulse sintering process increases, the aspect ratio of the cathode material particles is further reduced, the proportion of particles smaller than 1 μm is further reduced, and due to the increase in air pressure and classification frequency of the gas flow pulverization of the single sintering product, the particle size distribution width of the cathode material is increased, the compaction density of the cathode material is improved, and the specific capacity and cycle retention rate of the cathode material are also improved.

[0218] According to the test data of Examples 1 and 12, due to the decrease in the amount of oxygen supplement added, the proportion of particles satisfying 1≤α≤1.6 in all particles decreased, the number of slender particles in the cathode material increased, and the specific capacity and cycle retention rate of the cathode material decreased slightly.

[0219] According to the test data of Example 1 and Comparative Example 1, since the pulse sintering process was not used and the sintering temperature was high, the number of small particles decreased, and the high temperature sintering easily led to excessive particle growth, resulting in a further increase in the aspect ratio; the proportion of particles smaller than 1μm decreased, resulting in more voids between particles after the positive electrode material was coated on the electrode sheet, and the compaction density was low, which led to a lower capacity; at the same time, the contact of a large amount of electrolyte increased the number of side reactions on the material surface, which further led to a decrease in battery cycle performance.

[0220] According to the test data of Example 1 and Comparative Example 2, since the pulse sintering process was not used, the sintering temperature was low, and no oxygen supplement was added, the growth of the cathode material particles was insufficient, the reaction was incomplete, the aspect ratio of the particles increased, and the roundness of the particles decreased. In addition, the proportion of particles smaller than 1 μm increased, the specific surface area of ​​the cathode material was larger, the surface residual alkali increased, the side reactions with the electrolyte increased, and the cycle performance and discharge capacity of the cathode material decreased.

[0221] According to the test data of Example 1 and Comparative Example 3, since the pulse sintering process was not used, the sintering temperature was low, and no oxygen supplement was added, the growth of the cathode material particles was insufficient, the reaction was incomplete, the aspect ratio of the particles increased, and the roundness of the particles decreased. In addition, the proportion of particles smaller than 1 μm increased, the specific surface area of ​​the cathode material was larger, the surface residual alkali increased, the side reactions with the electrolyte increased, and the cycle performance and discharge capacity of the cathode material decreased.

[0222] Figure 4 is a comparison of the cycle performance of the cathode materials provided in Example 1 of this application with those in Comparative Examples 1 and 2. As shown in Figure 4, the capacity retention rate of the cathode material in Example 1 after 50 cycles of 1C charge-discharge is better than that of the cathode materials prepared in Comparative Examples 1 and 2.

[0223] 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 in that, The cathode material comprises multiple particles; The SEM image of the cathode material was obtained by scanning electron microscopy at 3K magnification. 200 particles in the SEM image were randomly measured. The average size of the longest diameter of a single particle was D, the average size of the width diameter that perpendicularly bisects the longest diameter of the particle was L, and the average aspect ratio of the particles was α = D / L, where 1 ≤ α ≤ 1.

6. In the electron microscope image of the cathode material, the proportion of particles with a diameter of less than 1 μm is R%, 10≤R≤16.

2. The cathode material according to claim 1, characterized in that, The general chemical formula of the cathode material is Li. x Ni a Co b N c M d O2, 0.98≤x≤1.1, 0.5≤a≤0.98, 0<b≤0.40, 0<c≤0.4, 0≤d≤0.10, a+b+c+d=1, N is Mn or Al; M element includes at least one of Ti, Zr, Mg, Sr, Ba, Ca, Nb, W, Sb, Ta, Sn and Y.

3. The cathode material according to claim 1, characterized in that, In the cathode material, the proportion of particles satisfying 1≤α≤1.6 among all particles is β, where β≥90%.

4. The cathode material according to claim 1, characterized in that, The volume median particle size D50 of the cathode material is 2.0 μm to 6.0 μm.

5. The positive electrode material according to claim 1, characterized in that, The volumetric particle size distribution width of the cathode material satisfies: 1.0 < (D 90 -D 10 ) / D 50 ≤2.

6. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The cathode material is a single crystal material; (2) The particles include primary particles, and the particle size of the primary particles is 1μm to 5μm.

7. The cathode material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode material is 0.4 m². 2 / g~0.8m 2 / g.

8. The positive electrode material according to claim 1, characterized in that, The tap density of the positive electrode material is ρ1g / cm³. 3 , 1.5≤ρ1<2.

2.

9. The positive electrode material according to claim 1, characterized in that, The compaction density of the cathode material is ρ2g / cm³. 3 , 3.0≤ρ2<3.

5.

10. The cathode material according to claim 1, characterized in that, The positive electrode material satisfies 11≤pH≤12.

11. The cathode material according to claim 1, characterized in that, The average aspect ratio α of the cathode material satisfies any one of the following conditions: (1) The average aspect ratio α of the positive electrode material is 1, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6 or any two of the above values. (2)1.08≤α≤1.37； (3)1.1≤α≤1.4； (4)1.2≤α≤1.6。 12. The cathode material according to claim 1, characterized in that, The percentage (R%) of particles with a diameter less than 1 μm in the cathode material satisfies any one of the following conditions: (1) The percentage of particles with a diameter less than 1 μm in the positive electrode material, R%, is 10, 11, 12, 13, 14, 15, 16 or any two of the above values. (2)10≤R≤14； (3)11≤R≤14。 13. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) 1μm < D < 5μm; (2) 1μm < L < 5μm.

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

15. A battery, characterized in that, 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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