Positive electrode material, positive electrode sheet and secondary battery

Abstract

Provided in the present application are a positive electrode material, a positive electrode sheet and a secondary battery. The positive electrode material comprises a plurality of particles; a cross section of each particle and / or agglomerate particle comprises a central region and a surface layer region; and the positive electrode material contains element M which is selected from at least one of Na, K, Cs, Mg, Ca, Sr or Ba. A test of the cross section of a single-crystal particle by an energy dispersive spectrometer shows that the average concentration of M in the central region is X1, the average concentration of M in the surface layer region is X2, and X1 and X2 satisfy: 1.2≤X2 / X1≤20. The particles comprise primary particles and agglomerate particles. The total number of particles and agglomerates of the positive electrode material is N, the number of the agglomerate particles is n, and n and N satisfy: n / N < 1%. Each agglomerate is formed by agglomerating 5 particles or more than 5 particles each having a particle size of 1 μm or less. The positive electrode material provided in the present application can improve the cycling stability and rate performance of the positive electrode material.

Description

Positive electrode material, positive electrode sheet and secondary battery Cross-reference to related applications

[0001] This application claims priority to Chinese patent application filed on December 26, 2024, with application number 202411967110.5 and entitled "Positive electrode material, positive electrode sheet and secondary battery". Technical Field

[0002] This application relates to the field of battery cathode material technology, specifically to a cathode material, a cathode sheet, and a secondary battery. Background Technology

[0003] Lithium-ion batteries boast advantages such as high energy density, zero pollution, zero emissions, and small size. Cathode materials, as a key component of lithium-ion batteries, play a decisive role in the battery's capacity, performance, and cost. However, the cycle stability and gas generation performance of current cathode materials urgently need improvement. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above defects, this application provides a cathode material that can improve the cycle stability and gas generation performance of the cathode material.

[0005] In addition, this application also provides a positive electrode sheet using positive electrode materials and a secondary battery.

[0006] This application provides a cathode material comprising element M, wherein element M is selected from at least one of Na, K, Cs, Mg, Ca, Sr, or Ba. The cathode material comprises multiple particles, the cross-section of which includes a central region and a surface region. The cross-section of the particles is tested by energy dispersive spectroscopy (EDS), and the average concentration of element M in the central region is measured as X1, and the average concentration of element M in the surface region is measured as X2. X1 and X2 satisfy: 1.2≤X2 / X1≤20. The particles include primary particles and aggregated particles. The SEM image of the cathode material is obtained by scanning electron microscopy at 3K magnification. The total number of primary particles and aggregated particles in the SEM image of the cathode material is N, and the number of aggregates is n. n and N satisfy: n / N<1%. The aggregates are formed by the aggregation of 5 or more primary particles with a particle size of less than 1 μm.

[0007] This application also provides a positive electrode sheet, including a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive electrode material.

[0008] This application also provides a secondary battery, including a casing, an electrode assembly, and an electrolyte or electrolyte solution. The electrode assembly and the electrolyte or electrolyte solution are both located inside the casing. The electrode assembly includes a separator and a negative electrode plate. The electrode assembly also includes a positive electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate.

[0009] In this application, the concentration of element M in the cathode material particles satisfies 1.2 ≤ X2 / X1 ≤ 20, resulting in a higher content of element M in the surface region of the particles. This increases the unit cell volume in the surface region, while the content of element M in the central region of the particles is lower, resulting in a relatively smaller unit cell volume. This creates compressive stress from the surface towards the center of the particles. This compressive stress can suppress lattice volume changes during charging and discharging, thereby improving the gas generation performance and long-term cycle performance of the cathode material. Simultaneously, due to the low strength of the agglomerate particles, a smaller proportion of agglomerates in the cathode material reduces particle breakage during electrode rolling, thus reducing the exposed surface area of ​​fine powder and particles, improving gas generation, and consequently synergistically improving the cycle stability and rate performance of the secondary battery.

[0010] Explanation of main component symbols

[0011] Electrode assembly 100, positive electrode 101, negative electrode 102 and separator 103. Attached Figure Description

[0012] Figure 1 is a cross-sectional schematic diagram of a lithium-ion battery using the cathode material of this application during charging.

[0013] Figure 2 is a cross-sectional schematic diagram of a lithium-ion battery using the cathode material of this application during discharge.

[0014] In Figure 3, (a) and (b) are the content distribution diagrams of element K inside the single crystal particles in Example 1 and Comparative Example 2 of this application, respectively.

[0015] In Figure 4, (a) and (b) are high-magnification scanning electron microscope (SEM) images of the cathode materials in Example 1 and Comparative Example 2 of this application, respectively.

[0016] Figure 5 is a schematic diagram of the concentration distribution of element M in this application.

[0017] Figure 6 is a schematic diagram of the surface and central regions of the elongated particles in this application. Detailed Implementation

[0018] The embodiments of this application are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; where there is no conflict, the implementation methods and features of the implementation methods of this application can be combined with each other; many specific details are set forth in the following description to provide a full understanding of this application, and the described implementation methods are only a part of the implementation methods of this application, and not all of the implementation methods.

[0019] One embodiment of this application provides a secondary battery, including a casing, an electrode assembly, and an electrolyte. Both the electrode assembly and the electrolyte are located within the casing.

[0020] The outer casing can be a packaging bag encapsulated with a sealing film (such as aluminum-plastic film), for example, a pouch battery. In other embodiments, it can also be a steel-cased battery, an aluminum-cased battery, etc.

[0021] Referring to Figures 1 and 2, the electrode assembly 100 includes a positive electrode 101, a negative electrode 102, and a separator 103, with the separator 103 disposed between the positive electrode 101 and the negative electrode 102. Referring to Figure 1, during discharge, active ions (such as lithium ions) are deintercalated from the crystal lattice of the negative electrode material in the negative electrode 102, pass through the separator 103 via the electrolyte, reach the positive electrode 101, and embed into the crystal lattice of the positive electrode material (such as a lithium-ion intercalated compound). Electrons are generated and travel from the negative electrode 102 to the positive electrode 101 via an external circuit. The reverse movement of electrons forms a current, which can be used by electrical appliances. During charging, referring to Figure 2, active ions (such as lithium ions) are deintercalated from the crystal lattice of the positive electrode material (such as a lithium-ion intercalated compound) in the positive electrode 101, pass through the separator 103 via the electrolyte, reach the negative electrode 102, and embed into the crystal lattice of the negative electrode material.

[0022] In some embodiments, the electrode assembly 100 may be a stacked structure, which is formed by alternatingly stacking a positive electrode 101, a separator 103, and a negative electrode 102. In other embodiments, the electrode assembly 100 may also be a wound structure, which is formed by sequentially stacking and then winding a positive electrode 101, a separator 103, and a negative electrode 102.

[0023] This application also provides a positive electrode sheet, including a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer includes a positive electrode material.

[0024] One embodiment of this application provides a cathode material, including element M, which is selected from at least one of Na, K, Cs, Mg, Ca, Sr, or Ba. The cathode material includes multiple particles, and the cross-section of each particle includes a central region and a surface region. The cross-section of the particles is tested by energy dispersive spectroscopy (EDS), and the average concentration of element M in the central region is measured as X1, and the average concentration of element M in the surface region is measured as X2. X1 and X2 satisfy: 1.2 ≤ X2 / X1 ≤ 20. The particles of the cathode material include primary particles and aggregate particles. The cross-sectional SEM image of the cathode material is obtained by scanning electron microscopy (SEM) at 3K magnification. In the cross-sectional SEM image of the cathode material, the total number of primary particles and aggregate particles is N, and the number of aggregates is n. n and N satisfy: n / N < 1%.

[0025] It should be noted that, as shown in Figure 5, in the cross-sectional view of the particle, in the circumscribed circle of the particle cross-section, the center of the circumscribed circle of the particle cross-section is taken as the center, the radius of the circumscribed circle is the radius L of the particle, the area from the center of the particle to a distance L / 2 from the center of the particle is the central area, and the area from the position L / 2 of the particle to the surface of the particle is the surface area.

[0026] It should be further explained that, in this application, in the cross-sectional view of the cathode material, the diameter L of the particle is defined as the diameter of the intersection of the circumscribed circle and the particle's edge. The area covered by the central region of the circumscribed circle is the central region of the particle (i.e., the area from the center of the particle to a distance L / 2 from the center of the particle), and the area covered by the surface region of the circumscribed circle is the surface region of the particle (the area from the position L / 2 of the particle to the particle's surface is the surface region). For irregularly shaped particles, such as elongated particles, as shown in Figure 6, the center of the circumscribed circle is defined as the center of the particle, the diameter L of the particle is defined as the diameter of the particle, the portion of the particle covered by the surface region of the circumscribed circle is the surface region of the particle, and the area covered by the central region of the circumscribed circle is the central region of the particle.

[0027] In this application, the concentration of element M in the particles is controlled to satisfy 1.2≤X2 / X1≤20, so that the content of element M near the particle surface is relatively high. Element M increases the unit cell volume in the particle surface region, while the content of element M near the particle center is relatively low, resulting in a relatively small unit cell volume in the particle center region. This forms compressive stress from the particle surface towards the center. The compressive stress can suppress lattice volume changes during charging and discharging, suppress the generation or propagation of particle cracks, thereby improving the gas generation performance of the cathode material and enhancing the long-term cycle performance of the cathode material.

[0028] Meanwhile, since the agglomerate particles have low strength, the proportion of agglomerates in the cathode material can reduce particle breakage caused by the electrode rolling process, thereby reducing the exposed surface area of ​​fine powder and particles, improving gas generation, and thus synergistically improving the cycle stability and rate performance of the secondary battery.

[0029] It should be noted that the agglomerate is formed by the aggregation of 5 or more particles with a diameter of less than 1 μm, and the maximum distance between any two points on the agglomerate particles is less than 4 μm. It can be understood that in some other embodiments, the maximum distance between any two points on the agglomerate particles is less than or equal to 5 μm. The radius of particles with a diameter of less than 1 μm refers to the diameter of the inscribed circle of a primary particle in a cross-sectional view of the cathode material.

[0030] When the n / N ratio is large, such as greater than or equal to 1%, it means that the number of particle agglomerates increases. During the electrode rolling process, the agglomerates are easily broken, the exposed surface of the positive electrode material increases, and the side reactions with the electrolyte increase, affecting the capacity utilization and long-cycle stability of the positive electrode material.

[0031] When X2 / X1 < 1.2, the unit cell volume of the particle surface region and the central region are uniformly distributed, making it difficult to form compressive stress from the surface region towards the central region. When X2 / X1 > 20, excessive element M will accumulate on the surface of the particle, occupying lattice lithium sites, affecting lithium ion transport and diffusion, and reducing the rate performance of the secondary battery.

[0032] In some embodiments, the ratio of X2 / X1 can be 1.2, 1.5, 2, 5, 7, 9, 10, 12, 14, 15, 16, 18, 19, 20, or any value within the range of any two of the above values. In some embodiments, n / N can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, or any value within the range of any two of the above values.

[0033] In some embodiments, 3.3 ≤ X2 / X1 ≤ 9.5. This facilitates the formation of suitable compressive stress from the surface to the center of the particles. Compressive stress can suppress lattice expansion during charging and discharging, further improving the cycle stability and rate performance of the secondary battery and reducing gas production.

[0034] In some embodiments, 0.5% ≤ n / N < 1%. This is beneficial for improving the energy density of the secondary battery while maintaining good capacity of the cathode material, and further improving the cycle stability, rate performance, and reducing gas production of the secondary battery.

[0035] In some embodiments, the concentration of element M is between 10 ppm and 400 ppm, based on the mass of the cathode material. A concentration of element M within this suitable range is beneficial for ensuring that the cathode material particles contain an appropriate amount of element M and that element M maintains a suitable unit cell volume. This helps suppress lattice strain generated during long-term cycling, further improving the cycle stability of the cathode material, while also ensuring good rate performance and cycle performance. If the concentration of element M in the cathode material is too high, the particles will contain more element M, leading to a larger change in unit cell volume, reducing the structural stability of the cathode material, and hindering the improvement of its cycle stability. In some embodiments, the concentration of element M can be 10 ppm, 50 ppm, 80 ppm, 100 ppm, 120 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, or any value within the range of any two of the above values.

[0036] In some embodiments, the cathode material is a single-crystal material, and the average particle size of the primary particles is 1 μm to 5 μm. An average particle size within a suitable range allows the secondary battery to maintain good rate performance while reducing the amount of gas produced. If the average particle size is large, such as greater than 5 μm, it affects lithium-ion transport and reduces the rate performance of the secondary battery. Conversely, if the average particle size is small, such as less than 1 μm, the contact area between the primary particles and the electrolyte in the cathode material is large, increasing gas production in the secondary battery. In some embodiments, the average particle size can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value within the range of any two of the above values.

[0037] In this application, 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 secondary particles formed by the agglomeration of nanoscale primary particles. In contrast, the smallest particles in single-crystal cathode materials are typically micrometer-sized single primary particles. Generally, in addition to EBSD testing, characterization methods such as scanning electron microscopy (SEM) 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, without significant particle agglomeration. EBSD can also characterize the orientation of single-crystal cathode materials. EBSD can observe that at least one grain has the same color, indicating that at least one grain has the same orientation; grains with the same orientation are single crystals. It should be specifically noted 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, differing only in size from polycrystalline materials composed of numerous small primary particles. Understandably, a single grain in this application can be a single particle composed of a single primary particle. The aforementioned single-crystal cathode materials may also contain a small number of "quasi-secondary particles" formed by the adhesion of several single particles. "Primary particle" refers to the smallest particle unit identified when observing cathode active materials using a scanning electron microscope, while "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles, exhibiting a relatively rounded spherical morphology. "Quasi-secondary particles" are formed by the adhesion of several single particles; typically, the particle size of a single particle in these quasi-secondary particles is between 1 μm and 5 μm, and generally, the roundness of "quasi-secondary particles" is lower than that of conventional "secondary particles."

[0038] In some embodiments, the lattice strain ε of the cathode material is <0.1%. By controlling the lattice strain of the cathode material within a suitable range, it is beneficial to reduce the diffusion barrier of lithium ions between crystallites, increase the diffusion coefficient of lithium ions, thereby reducing the crystal volume change caused by lithium ion migration during the charging and discharging process of the secondary battery, suppressing the generation of microcracks within the single crystal particles in the cathode material, and thus improving the cycle stability of the cathode material and reducing the DC internal resistance (DCR) of the cathode material. In some embodiments, the lattice strain ε of the single crystal particles can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or any value within the range of any two of the above values.

[0039] In some embodiments, the general formula of the positive electrode material is: Li a Nib Co c Q d O2, wherein 0.95≤a≤1.2, 0<b≤1, 0<c≤1, 0<d≤1, b+c+d=1, and element Q is selected from at least one of Mn or Al.

[0040] In some embodiments, the general formula of the positive electrode material is: Li a Ni b Co c Q d M e N f O2, wherein 0.95≤a≤1.2, 0<b≤1, 0<c≤1, 0<d≤1, 0<e<1, 0≤f<1, b+c+d+e+f=1, element Q is selected from at least one of Mn or Al, element M is selected from at least one of Na, K, Cs, Mg, Ca, Sr or Ba, and element N is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, Y.

[0041] When element M is doped into the above material, it occupies the sites of the main element in the transition metal layer, thus increasing the interlayer spacing and unit cell volume. When element M is enriched near the particle surface, the unit cell volume in the surface region is larger than that in the central region, resulting in higher stress in the surface region and compressive stress towards the particle center. It should be noted that for element M selected from at least one of Na, K, Cs, Mg, Ca, Sr, or Ba, for example, when element M is Ca, the ionic radius of Ca²⁺ is 99 pm, while that of Ni… 2+ The ionic radius of Co is 72 pm. 2+ The ionic radius of Mn is 74 pm. 2+ The ionic radius of Ca is 80 pm, that is, Ca 2+ The ionic radius is greater than that of Ni. 2+ Co 2+ Mn 2+ The ionic radius of Ca 2+ When atoms enter the transition metal layer of the cathode material to replace Ni / Co / Mn elements, the Ca atoms with larger ionic radii... 2+ This will increase the interlayer spacing of the transition metals, thus increasing the unit cell volume; while when doped with Ca... 2+When the particles are concentrated near the surface, the average unit cell volume decreases from the surface to the center, generating compressive stress within the particles. This compressive stress can suppress expansion at the center of the particles, thus suppressing internal stress and fatigue cracks generated inside the particles due to the uneven lattice expansion during lithium ion insertion / extraction caused by the long lithium ion transport distance in the single-crystal material during the charging and discharging process of the cathode material. This inhibits the initiation and propagation of cracks within the particles, thereby improving the long-term electrochemical performance of the secondary battery.

[0042] In some embodiments, the cathode material further contains element N, which is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, and Y; the concentration of element N is less than 5000 ppm based on the mass of the cathode material. In the above cathode material, appropriate doping with element N can stabilize the cathode material and further improve its specific capacity and cycle stability. The concentration of element N is less than 5000 ppm based on the mass of the cathode material. Doping with element N within a suitable range is beneficial for further improving the specific capacity and cycle stability of the cathode material. If the concentration of element N is too high, such as greater than 5000 ppm, excessive element N will accumulate on the surface of the particles, easily causing particle agglomeration and adhesion. During the preparation of the cathode electrode sheet, compacting the cathode electrode sheet can easily lead to cracking of agglomerated particles, increasing side reactions between the electrolyte and the cathode material in the secondary battery, and affecting the long-term electrochemical performance of the secondary battery. In some embodiments, the concentration of element N can be 10 ppm, 100 ppm, 200 ppm, 500 ppm, 600 ppm, 800 ppm, 1000 ppm, 1500 ppm, 1700 ppm, 1900 ppm, 2000 ppm, 2500 ppm, 2700 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, or any value within the range of any two of the above values. In some embodiments, the concentration of element N is between 1000 ppm and 3000 ppm.

[0043] In some embodiments, the specific surface area of ​​the cathode material is 0.4 m². 2 / g to 0.9m 2 / g. A specific surface area of ​​the cathode material within the above range is beneficial for reducing the contact between the cathode material and the electrolyte, minimizing side reactions, and resulting in good discharge capacity. In some embodiments, the specific surface area of ​​the cathode material can be 0.4m². 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g or any value within the range of any two of the above values.

[0044] In some embodiments, the tap density ρ1 of the positive electrode material is: ρ1 > 2.0 g / cm³ 3 A suitable tap density for the positive electrode material is beneficial for improving the compaction of the electrode sheet containing the positive electrode material, thereby increasing the energy density of the secondary battery. In some embodiments, the tap density of the positive electrode material can be 2.5 g / cm³. 3 3.0g / cm 3 3.5g / cm 3 4.0g / cm 3 4.5g / cm 3 5.0g / cm 3 Or any value within the range formed by any two of the above values.

[0045] In some embodiments, the compacted density ρ2 of the cathode material powder is: ρ2 ≥ 2.8 g / cm³ 3 A suitable powder compaction density for the cathode material is beneficial for further improving the compaction of the electrode sheet containing the cathode material, thereby increasing the energy density of the secondary battery. In some embodiments, the powder compaction density of the cathode material can be 2.8 g / cm³. 3 3.0g / cm 3 3.2g / cm 3 3.8g / cm 3 4g / cm 3 4.5g / cm 3 Or any value within the range formed by any two of the above values.

[0046] In some embodiments, the particle size of the cathode material satisfies: 1.0 ≤ (D90 - D10) / D50 ≤ 1.5. A particle size distribution of the cathode material satisfying the above relationship is beneficial for further improving the compaction of the electrode containing the cathode material and increasing the energy density of the secondary battery. The particle size D50 of the cathode material represents the particle size that, in a volume-based particle size distribution, reaches 50% of the total volume from the smallest particle size; that is, the volume of cathode material particles smaller than this size accounts for 50% of the total volume of the cathode material particles. The particle size D90 of the cathode material represents the particle size that, in a volume-based particle size distribution, reaches 90% of the total volume from the smallest particle size. The particle size D10 of the cathode material represents the particle size that, in a volume-based particle size distribution, reaches 10% of the total volume from the smallest particle size. (D90 - D10) / D50 is represented by the "Span value".

[0047] This application also provides a method for preparing a step-by-step cathode material, comprising the following steps:

[0048] S1: Prepare a mixed salt solution containing Ni salt, Co salt, and Q salt according to a set ratio of Ni:Co:Q. Add a certain amount of salt solution containing element M to the mixed salt solution and mix thoroughly to obtain a mixed solution. Prepare an oxide precursor from the mixed solution using a spray pyrolysis method. Element Q is selected from at least one of Mn or Al.

[0049] In this step, the Ni salt, Co salt, and Q salt are all derived from the recycled cathode material. Specifically, the recycled ternary cathode material undergoes compositional analysis to confirm the proportion of the main element and the types and proportions of element M present in the recycled material. Then, the cathode material with the confirmed composition is mixed with pure Ni / Co / Q metal according to the final target Ni:Co:Q ratio to prepare a mixed salt solution. Element Q is selected from at least one of Mn or Al. It is understood that in some other embodiments, the Ni salt, Co salt, and Q salt may also be derived from commercially available products. The Ni salt, Co salt, and Q salt can be any one of sulfate, nitrate, chloride, carbonate, or phosphate.

[0050] If the recovered ternary cathode material contains dopant element M, the concentration of dopant element M can be adjusted by adding a target dopant element concentration to achieve the target concentration, thus obtaining a mixed solution. Salts of element M include at least one of the following: chloride, sulfate, sulfite, nitrate, carbonate, or phosphate.

[0051] Optionally, in the preparation process of the mixed solution, the total metal concentration in the mixed solution ranges from 2 mol / L to 8 mol / L, and the mass percentage concentration of element M in the precursor solution is 0.01% to 0.06%. Specifically, the mass percentage concentration of element M in the precursor solution can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or 0.06%, etc., or other values ​​within the above range, which are not limited here. By controlling the mass percentage concentration of element M in the precursor solution within the above range, the content of element M in the obtained cathode material can meet the range of 10 ppm to 400 ppm. Within this range, it is beneficial for the spray droplets to have a moderate solid content in the subsequent spraying step, and the solid phase, as a nucleation site, is conducive to the rapid solidification and nucleation of droplets.

[0052] In this step, the spray pyrolysis method includes a spraying step and an annealing step. During the spraying process in the spraying step, the atomizing airflow rate of the spray is controlled to be 100-300 m³ / h. 3 The atomization pressure is 400-700 kPa; during this process, the large atomization flow rate and atomization pressure enable ions with different ionic radii to separate in the droplets during the spraying process, and the M metal element will be distributed on the surface of the droplets.

[0053] The annealing step involves annealing the liquid treated in the spraying step at a temperature controlled between 800℃ and 1200℃. The higher annealing temperature allows for rapid pyrolysis and nucleation of the droplets, maximizing the retention of the M metal element distribution on the particle surface. Furthermore, by controlling different atomization airflow rates, atomization pressures, and annealing temperatures, the internal and external distribution difference of the M element can be adjusted to ensure that the M element value falls within the range of 1.2 ≤ X2 / X1 ≤ 20.

[0054] S2: The prepared oxide precursor is pulverized to a particle size D50 of 2.0μm-4.0μm. The pulverized oxide precursor is then uniformly mixed with lithium salt and a metal compound containing N element to obtain a mixture. The mixture is then sintered once to obtain a sintered product.

[0055] When the particle size D50 of the oxide precursor is within the above range, it is beneficial to obtain less cathode material powder and more rounded single crystal particles.

[0056] The metal oxide containing element N is selected from any one or more of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3; preferably, the metal oxide containing element N is CeO2 and / or WO3, and more preferably, the metal oxide containing element N is CeO2.

[0057] In one embodiment of the present invention, in step 2, the oxide precursor, lithium source, and metal oxide containing element N are mixed in a mass ratio of 1:(0.4-0.8):(0.003-0.006). Specifically, the oxide precursor, lithium source, and metal oxide containing element N are mixed in mass ratios of 1:0.4:0.003, 1:0.5:0.004, 1:0.6:0.006, 1:0.5:0.003, 1:0.5:0.005, 1:0.8:0.003, 1:0.8:0.006, 1:0.4:0.006, or 1:0.5:0.004. Other values ​​within the above range are also possible and are not limited here. By limiting the mass ratio of the oxide precursor, lithium source, and metal oxide containing element N, a cathode material with the chemical formula described in this application can be obtained.

[0058] The lithium salt can be at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

[0059] In step S2, during the first sintering, the heating rate in the heating section is controlled at 3℃ / min or less, and the slow heating allows for more complete single crystal nucleation.

[0060] In step S2, during sintering, the holding time is more than 8 hours, which allows for more complete growth of single crystal particles and results in fewer single crystal agglomerates. Optionally, in step S2, pulse sintering can be selected as the sintering method, which can reduce the mixing of cations caused by prolonged high temperature. At the same time, because the high temperature time is short, the single crystal particles will not grow excessively, and the sintered single crystal particles are of similar size with less fine powder. The specific steps are as follows: (1) In an oxygen or air atmosphere, place the mixture in a furnace with a furnace pressure of 2 Pa to 30 Pa and sinter at a temperature of 800°C to 1000°C for 1 to 2 hours. (2) Then sinter at a temperature of T3 (T3 = T2 - 30°C) for 1 to 2 hours. Repeat the temperatures of T2 and T3, so that the total sintering time of the mixture at T2 temperature is 4 to 8 hours and the total sintering time of the mixture at T3 temperature is 4 to 8 hours. (3) Finally, the material is kept at a temperature of T4 (T4 = T3 - 10℃) for 4 hours to anneal the sintered material, repair the micrograin boundaries, and achieve uniform particle growth, thereby obtaining the matrix material. Through the above steps, the value of agglomerates can be controlled to be less than 1%.

[0061] Optionally, the sintered product after sintering is subjected to air jet milling, and the particle size D50 is controlled within 3.0μm-5.0μm. This particle size range corresponds to the D50 particle size range of the precursor, which can break down the single crystal particles.

[0062] S3: The pulverized sintered product is uniformly mixed with the coating agent. After uniform mixing, a second sintering is carried out in an oxygen atmosphere. The sintered sample is then sieved and demagnetized to obtain the finished product. The coating agent contains element N.

[0063] In step S3, coating the sintered product with a coating agent can improve the electrochemical performance of the cathode material.

[0064] In one embodiment of the present invention, the coating agent used in the coating treatment is selected from at least one of ZrO2, TiO2, Al2O3, CoO, MgO, WO3, CeO2, and Y2O3. The content of element N in the cathode material is 0 ppm to 5000 ppm. Specifically, the content of element N in the cathode material can be 0 ppm, 5 ppm, 100 ppm, 500 ppm, 1000 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2400 ppm, 2800 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 4800 ppm, or 5000 ppm, etc., and of course, other values ​​within the above range are also possible and are not limited here. When the concentration of element N is within the above range, the crystal structure of the cathode material can be stabilized, the ionic conductivity can be improved, and the side reactions between the cathode material and the electrolyte can be delayed.

[0065] In step S3, the secondary sintering temperature is 500℃-800℃, and the sintering time is 6h-10h.

[0066] Negative electrode sheet

[0067] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector.

[0068] Negative current collectors include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, or any combination thereof.

[0069] Negative current collectors include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrates coated with conductive metal, or any combination thereof.

[0070] Negative electrode active materials include materials that reversibly insert / deintercalate lithium ions. In some embodiments, the materials that reversibly insert / deintercalate lithium ions include carbon materials. In some embodiments, the carbon material can be any carbon-based negative electrode active material commonly used in lithium-ion rechargeable batteries. In some embodiments, the carbon material includes, but is not limited to: crystalline carbon, amorphous carbon, or mixtures thereof. Crystalline carbon can be amorphous, flake-shaped, flake-shaped, spherical, or fibrous natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbides, calcined coke, etc.

[0071] In some embodiments, the negative electrode active material layer includes a negative electrode active material. The specific type of negative electrode active material is not limited and can be selected according to requirements. In some embodiments, the negative electrode active material includes, but is not limited to: lithium metal, structured lithium metal, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 Li-Al alloys or any combination thereof. The silicon-carbon composite refers to a silicon-carbon anode active material containing at least about 5 wt% silicon by weight.

[0072] In some embodiments, the negative electrode active material comprises at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon alloy, or silicon oxide.

[0073] When the negative electrode comprises silicon carbide, based on the total weight of the negative electrode active material, the silicon:carbon ratio is approximately 1:10-10:1, and the median particle size Dv50 of the silicon carbide is approximately 0.1 micrometers to 20 micrometers. When the negative electrode comprises an alloy material, the negative electrode active material layer can be formed using methods such as vapor deposition, sputtering, or plating. When the negative electrode comprises lithium metal, the negative electrode active material layer is formed, for example, using a conductive framework with spherical strands and metal particles dispersed in the conductive framework. In some embodiments, the spherical stranded conductive framework may have a porosity of approximately 5% to approximately 85%. In some embodiments, a protective layer may also be provided on the lithium metal negative electrode active material layer.

[0074] In some embodiments, the negative electrode active material layer may include an adhesive and optionally a conductive material. The adhesive enhances the bonding between the negative electrode active material particles and the bonding between the negative electrode active material and the current collector. In some embodiments, the adhesive includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0075] In some embodiments, the conductive material includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0076] In some embodiments, the current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with a conductive metal, and any combination thereof.

[0077] The negative electrode can be prepared by methods known in the art. For example, the negative electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and then coating the active material composition onto a current collector. In some embodiments, the solvent may include, but is not limited to, water.

[0078] Separating membrane

[0079] The material and shape of the separator used in the secondary battery of this application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic material formed from a material stable to the electrolyte of this application.

[0080] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be selected.

[0081] A surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0082] The binder is selected from at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, the polymer material of which is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0083] electrolyte

[0084] According to some embodiments of this application, the electrolyte includes an organic solvent, a lithium salt, and optional additives.

[0085] The organic solvent in the electrolyte of this application may be any organic solvent known in the prior art that can be used as an electrolyte solvent. There are no limitations on the electrolyte used in the electrolyte according to this application; it may be any electrolyte known in the prior art. The additives in the electrolyte according to this application may be any additives known in the prior art that can be used as electrolyte additives. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or ethyl propionate (EP).

[0086] In some embodiments, the organic solvent includes ether solvents, such as at least one selected from 1,3-dioxapentane (DOL) and dimethyl glycol ether (DME). In some embodiments, the lithium salt includes at least one selected from organic lithium salts or inorganic lithium salts. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(fluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalatoborate)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalatoborate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one selected from fluoroethylene carbonate and adiponitrile.

[0087] According to some embodiments of this application, the secondary battery of this application includes, but is not limited to, a lithium-ion battery. In some embodiments, the secondary battery includes a lithium-ion battery.

[0088] This application also utilizes secondary batteries in electronic devices to power loads within those devices. The electronic devices described in this application are not particularly limited. In some embodiments, the electronic devices include, but are not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0089] The present application's solution will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the present application. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically mentioned are all conventional commercially available products or open-source materials.

[0090] Example 1

[0091] (1) Take metal salts of Ni, Co and Mn and prepare chloride salt solutions according to the molar ratio of Ni:Co:Mn = 55:15:30. Add K chloride solution to the chloride salt solution to prepare a precursor solution. The mass ratio of K in the precursor solution is 0.01%, and the total concentration of Ni, Co, Mn and K in the precursor solution is 5 mol / L.

[0092] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 200 m³ / h. 3 / h, atomization pressure is 550Kpa, pyrolysis temperature is 500℃, and annealing temperature is 1000℃.

[0093] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.24 μm. 400 g of pulverized oxide precursor, 186.72 g of lithium carbonate and 1.8 g of Y2O3 were mixed evenly to obtain a mixture. Pulse sintering was selected for sintering. The mixture was sintered in an oxygen or air atmosphere at a furnace pressure of 20 Pa and a temperature of 950 °C for 1-2 h. The mixture was then sintered at a temperature of T3: T2-30 °C for 2 h. The temperatures of T2 and T3 were repeated to sinter for a total of 8 h at T2 and 8 h at T3. Finally, the mixture was held at T4: T3-10 °C for 4 h to anneal the material and obtain the first sintered product.

[0094] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0095] Example 2

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

[0097] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 60:10:30. Add Mg sulfate solution to nitrate solution to prepare precursor solution. The mass ratio of Mg in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and Mg in precursor solution is 5 mol / L.

[0098] (2) Spray pyrolysis involves spraying the precursor solution and then annealing it to produce an oxide precursor. The atomizing airflow rate for the spray treatment is 220 m³ / h. 3 / h, atomization pressure is 500Kpa, pyrolysis temperature is 600℃, and annealing temperature is 900℃.

[0099] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.16 μm. 400 g of pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of Y2O3 to obtain a mixture. Pulse sintering was selected for sintering. The mixture was sintered in an oxygen or air atmosphere at a furnace pressure of 20 Pa and a temperature of 940 °C for 1-2 h. The mixture was then sintered at a temperature of 30 °C (T2-30 °C) for 2 h. The temperatures of T2 and T3 were repeated to sinter for a total of 8 h at T2 and 8 h at T3. Finally, the mixture was annealed at a temperature of 10 °C (T3-10 °C) for 4 h to obtain a primary sintered product.

[0100] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.1 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0101] Example 3

[0102] The difference between Example 3 and Example 1 is that in step (1), "K chloride solution" is replaced with "Ca chloride solution". In step (2), the atomizing airflow rate for the spray treatment is 180 m³ / s. 3 The atomization pressure was 600 kPa, the pyrolysis temperature was 800 °C, and the annealing temperature was 1100 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor was 3.36 μm. In step (4), the median particle size distribution (D50) of the pulverized material was 4.8 μm. The remaining steps were the same as in Example 1.

[0103] Example 4

[0104] The difference between Example 4 and Example 1 is that in step (1), "K chloride solution" is replaced with "Ba chloride solution". In step (2), the atomization pressure of the spray treatment is 500 kPa and the pyrolysis temperature is 800 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor is 3.05 μm. In step (4), the median particle size distribution (D50) of the pulverized material is 3.5 μm. The remaining steps are the same as in Example 1.

[0105] Example 5

[0106] The difference between Example 5 and Example 1 is that in step (1), "K chloride solution" is replaced with "Sr nitrate solution". In step (2), the atomizing airflow rate for the spray treatment is 150 m³ / s. 3The atomization pressure was 650 kPa, the pyrolysis temperature was 700 °C, and the annealing temperature was 800 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor was 3.5 μm. In step (4), the median particle size distribution (D50) of the pulverized material was 4.2 μm. The remaining steps were the same as in Example 1.

[0107] Example 6

[0108] The difference between Example 6 and Example 1 is that in step (1), "K chloride solution" is replaced with "K chloride solution and Mg chloride solution", and the mass ratio of K and Mg elements in the precursor solution is 0.02%. In step (2), the pyrolysis temperature of the spray treatment is 900℃. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.28 μm. In step (4), the median particle size distribution D50 of the pulverized material is 4.0 μm. The remaining steps are the same as in Example 1.

[0109] Example 7

[0110] Example 7 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "K sulfate solution and Ca sulfate solution", and the mass ratio of K and Ca elements in the precursor solution is 0.02%. In step (2), the atomizing airflow rate for the spray treatment is 240 m³ / s. 3 The atomization pressure was 450 kPa, the pyrolysis temperature was 600 °C, and the annealing temperature was 950 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor was 2.96 μm. In step (4), the median particle size distribution (D50) of the pulverized material was 4.7 μm. The remaining steps were the same as in Example 1.

[0111] Example 8

[0112] Example 8 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "K chloride solution and Ba chloride solution", and the mass ratio of K and Ba elements in the precursor solution is 0.02%. In step (2), the atomization pressure of the spray treatment is 600 kPa, and the pyrolysis temperature is 700 °C. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.1 μm. In step (4), the median particle size distribution D50 of the pulverized material is 3.7 μm. The remaining steps are the same as in Example 1.

[0113] Example 9

[0114] Example 9 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "K chloride solution and Sr chloride solution", and the mass ratio of K and Sr elements in the precursor solution is 0.02%. In step (2), the atomization airflow rate for the spray treatment is 180 m³ / s. 3 The atomization pressure was 500 kPa, and the pyrolysis temperature was 650 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor was 3.25 μm. In step (4), the median particle size distribution (D50) of the pulverized material was 4.3 μm. The remaining steps were the same as in Example 1.

[0115] Example 10

[0116] Example 10 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "Mg chloride solution and Ca chloride solution", and the mass ratio of Mg and Ca elements in the precursor solution is 0.03%. In step (2), the atomization pressure of the spray treatment is 580 kPa, and the pyrolysis temperature is 700 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor is 3.75 μm. In step (4), the median particle size distribution (D50) of the pulverized material is 4.8 μm. The remaining steps are the same as in Example 1.

[0117] Example 11

[0118] Example 11 differs from Example 1 in that, in step (1), the "K chloride solution" is replaced with "Mg nitrate solution and Ba nitrate solution", and the mass ratio of Mg and Ba elements in the precursor solution is 0.03%. In step (2), the atomization airflow rate for the spray treatment is 150 m³ / s. 3 / h, atomization pressure is 550 kPa, pyrolysis temperature is 800 °C. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.21 μm. In step (4), the median particle size distribution D50 of the pulverized material is 4.1 μm. The remaining steps are the same as in Example 1.

[0119] Example 12

[0120] Example 12 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "Mg chloride solution and Sr chloride solution", and the mass ratio of Mg and Sr elements in the precursor solution is 0.03%. In step (2), the atomization airflow rate of the spray treatment is 120 m³ / s. 3The atomization pressure was 700 kPa, and the pyrolysis temperature was 900 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor was 3.19 μm. In step (4), the median particle size distribution (D50) of the pulverized material was 4.2 μm. The remaining steps were the same as in Example 1.

[0121] Example 13

[0122] Example 13 differs from Example 1 in that, in step (1), "K chloride solution" is replaced with "Ca chloride solution and Ba chloride solution", and the mass ratio of Ca and Ba elements in the precursor solution is 0.03%. In step (2), the atomization pressure of the spray treatment is 600 kPa, and the pyrolysis temperature is 600 °C. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.38 μm. In step (4), the median particle size distribution D50 of the pulverized material is 4.2 μm. The remaining steps are the same as in Example 1.

[0123] Example 14

[0124] Example 14 differs from Example 1 in that, in step (1), the "K chloride solution" is replaced with "Ca nitrate solution and Sr nitrate solution", and the mass ratio of Ca and Sr in the precursor solution is 0.03%. In step (2), the atomization pressure of the spray treatment is 600 kPa, and the pyrolysis temperature is 1000 °C. In step (3), the median particle size distribution (D50) of the pulverized oxide precursor is 3.48 μm. In step (4), the median particle size distribution (D50) of the pulverized material is 4.4 μm. The remaining steps are the same as in Example 1.

[0125] Example 15

[0126] Example 15 differs from Example 1 in that, in step (1), the "K chloride solution" is replaced with "Ba chloride solution and Sr chloride solution", and the mass ratio of Ba and Sr elements in the precursor solution is 0.03%. In step (2), the pyrolysis temperature of the spray treatment is 600℃, and the annealing temperature is 1200℃. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.52 μm. In step (4), the median particle size distribution D50 of the pulverized material is 4.7 μm. The remaining steps are the same as in Example 1.

[0127] Example 16

[0128] Example 16 differs from Example 1 in that, in step (1), metal salts of Ni, Co, and Al are prepared into a nitrate solution according to a molar ratio of Ni:Co:Al = 50:20:30. In step (3), the median particle size distribution D50 of the pulverized oxide precursor is 3.19 μm. In step (4), the median particle size distribution D50 of the pulverized material is 4.4 μm. The remaining steps are the same as in Example 1.

[0129] Example 17

[0130] Example 17 differs from Example 1 in that step (4) is omitted. The remaining steps are the same as in Example 1.

[0131] Example 18

[0132] The difference between Example 18 and Example 1 is that, in step (1), the metal salts of Ni, Co, and Mn are prepared into a nitrate solution according to a molar ratio of Ni:Co:Mn = 70:10:20, and the mass percentage of K in the precursor solution is 0.04%; in step (2), the atomization airflow rate of the spray treatment is 100 m³ / s. 3 / h, atomization pressure is 700Kpa, pyrolysis temperature is 400℃, and annealing temperature is 1200℃. In step (3), pulse sintering is selected for sintering; the mixture is sintered in an oxygen or air atmosphere at a furnace pressure of 20Pa and a temperature T2 of 935℃ for 1-2 hours, and other steps are the same as in Example 1.

[0133] Example 19

[0134] The difference between Example 19 and Example 1 is that, in step (1), the metal salts of Ni, Co, and Mn are prepared into a nitrate solution according to a molar ratio of Ni:Co:Mn = 80:10:10; and in step (2), the atomizing airflow rate of the spray treatment is 300 m³ / s. 3 / h, atomization pressure is 400Kpa, pyrolysis temperature is 1000℃, and annealing temperature is 500℃. In step (3), pulse sintering is selected for sintering; the mixture is sintered in an oxygen or air atmosphere at a furnace pressure of 20Pa and a temperature T2 of 930℃ for 1-2 hours, and other steps are the same as in Example 1.

[0135] Example 20

[0136] The difference between Example 20 and Example 1 is that in step (1), the metal salts of Ni, Co, and Mn are prepared into a nitrate solution according to a molar ratio of Ni:Co:Mn = 90:5:5. In step (3), pulse sintering is selected for sintering; the mixture is sintered in an oxygen or air atmosphere at a furnace pressure of 20 Pa and a temperature T2 of 925 °C for 1-2 hours, and the other steps are the same as in Example 1.

[0137] Comparative Example 1

[0138] The difference between Comparative Example 1 and Example 1 is that, in steps (1) and (2), a hydroxide precursor with a molar ratio of Ni:Co:Mn = 55:15:30 was synthesized by co-precipitation. In step (3), "Y2O3" was replaced with "CeO2". The remaining steps are the same as in Example 1.

[0139] Comparative Example 2

[0140] The difference between Comparative Example 2 and Example 1 is that in steps (1) and (2), a hydroxide precursor with a molar ratio of Ni:Co:Mn = 55:15:30 was synthesized by co-precipitation. In step (3), "Y2O3" was replaced with "1.8g CeO2, 0.1g MgO, 0.1g KOH", and sintered at 960°C for 8 hours in a compressed air atmosphere to obtain the sintered product. The remaining steps were the same as in Example 1.

[0141] Comparative Example 3

[0142] This comparative example provides a cathode material, which is obtained by the following preparation method:

[0143] (1) Pure metal salts of Ni, Co, and Mn are prepared into a mixed nitrate solution according to a molar ratio of Ni:Co:Mn = 55:15:30. The nitrate solution is then spray-treated and followed by annealing to produce an oxide precursor. The atomization airflow rate for the spray treatment is 220 m³ / h. 3 / h, atomization pressure is 500Kpa, pyrolysis temperature is 600℃, and annealing temperature is 900℃.

[0144] (2) The oxide precursor was pulverized and the pulverization D50 was controlled to be 3.48 μm. 400 g of pulverized oxide precursor, 186.72 g of lithium carbonate, and 1.8 g of CeO2 were mixed evenly and sintered at 960 °C for 8 h in a compressed air atmosphere to obtain the sintered product.

[0145] (3) The obtained sintered material is crushed to a particle size D50 of 4.1μm to obtain crushed material; 300g of crushed material is mixed with 0.5g of WO3 and sintered at 550℃ for 8h in an oxygen atmosphere to obtain sintered material; the sintered material is demagnetized by sieving to obtain positive electrode material.

[0146] Comparative Example 4

[0147] (1) Take metal salts of Ni, Co and Mn and prepare nitrate solution according to the molar ratio of Ni:Co:Mn = 55:15:30. Add K chloride solution to nitrate solution to prepare precursor solution. The mass content of K element in precursor solution is 0.01% and the total concentration of Ni, Co, Mn and K in precursor solution is 5 mol / L.

[0148] (2) The precursor solution is spray-treated and then annealed to produce an oxide precursor. The atomization airflow rate of the spray treatment is 80 m³ / s. 3 / h, atomization pressure is 900Kpa, pyrolysis temperature is 1000℃, and annealing temperature is 700℃;

[0149] (3) The oxide precursor was pulverized, and the median particle size D50 of the pulverized oxide precursor was 3.24 μm. 400 g of the pulverized oxide precursor was uniformly mixed with 186.72 g of lithium carbonate and 1.8 g of CeO2 to obtain a mixture. Pulse sintering was selected for sintering. The mixture was sintered in an oxygen or air atmosphere at a furnace pressure of 20 Pa and a temperature of 940 °C for 1-2 h. The mixture was then sintered at a temperature of 30 °C (T2-30 °C) for 2 h. The temperatures of T2 and T3 were repeated to sinter for a total of 8 h at T2 and 8 h at T3. Finally, the mixture was held at T4 (T3-10 °C) for 4 h to anneal the material and obtain the first sintered product.

[0150] (4) The sintered material is crushed to obtain a pulverized material with a median particle size D50 of 4.2 μm. 300 g of the pulverized material is mixed with 0.5 g of WO3 and sintered at 550 °C for 8 h in an oxygen atmosphere to obtain a sintered material. The sintered material is demagnetized by sieving to obtain a positive electrode material.

[0151] Comparative Example 5

[0152] The difference between Comparative Example 5 and Example 19 is that, in step (3), pulse sintering is not used, but two-stage sintering is used. The sintering temperature of the first stage is 830°C and the sintering time is 4 hours. The sintering temperature of the second stage is 930°C and the time is 4 hours.

[0153] The specific performance parameters of the cathode materials in the above embodiments and comparative examples are detailed in Tables 1 to 4.

[0154] The performance of the cathode materials prepared in the examples and comparative examples was tested using the following test methods and battery performance test methods.

[0155] Test method:

[0156] 1. The methods for testing the elemental concentrations of M, N, and the main element are as follows:

[0157] 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. Use an Agilent 5110ICP-OES detection instrument to test the diluted solution to characterize the content of the main elements Li / Ni / Co / Mn / Al. Use an Agilent 5110ICP-OES detection instrument to test the test stock solution to characterize the content of other elements such as M and N. Thus, the content of M and N elements can be obtained.

[0158] 2. The test method for the concentration distribution of element M is as follows:

[0159] The method for testing the average concentration X1 of element M in the central region and the average concentration X2 of element M in the surface region of cathode material particles is as follows: A cross-sectional sample is prepared using a Hitachi ion cutter (IM5000). A suitable field of view is selected using a Hitachi S4800 scanning electron microscope, and then EDS is used to perform a line scan or spot scan of the particle cross-section within a 5k field of view. For example, a spot scan can be used to measure the content of element M at 10 locations (generally at least 5 points) in the central region of the particle cross-section. The summation and averaging of the element M content yields the number of atoms in the central region of the particle (dimensionless). Similarly, the content of element M at 10 locations in the surface region of the particle cross-section is measured, and the summation and averaging of the element M content yields the number of atoms in the surface region of the particle (dimensionless). Ten particles were randomly selected and the number of atoms in the central region and the number of atoms in the surface region of each particle were characterized using the method described above. The average concentration of element M in the central region X1 (dimensionless) was obtained by summing and averaging the number of atoms in the central region of each of the ten particles. The average concentration of element M in the surface region X2 (dimensionless) was obtained by summing and averaging the number of atoms in the surface region of each of the ten particles.

[0160] As shown in Figure 5, in the cross-sectional view of the particle, within the circumcircle of the particle's cross-section, the center of the circumcircle is taken as the center, and the radius of the particle is L, defined as the radius of the circumcircle. The region from the particle's center to a distance L / 2 from the particle's center is the central region, and the region from L / 2 to the particle's surface is the surface region. For irregularly shaped particles, such as elongated particles, as shown in Figure 6, the center of the particle's circumcircle is taken as the particle's center, and the diameter L of the particle's diameter is the diameter of the intersection of the circumcircle and the particle's edge. The portion of the particle covered by the surface region of the circumcircle is the surface region, and the region covered by the central region of the circumcircle is the central region. When the cathode material contains two or more elements M, the X1 and X2 values ​​of each element M are measured separately, and the corresponding X2 / X1 values ​​are calculated.

[0161] For point scanning and line scanning, please refer to Figure 5 for the following explanation:

[0162] Point scan: Select 5-10 points in the central region (inside the dashed circle in Figure 5) for EDS measurement, and take the average value to obtain the average number of atoms in the central region X1; select 5-10 points in the surface region (outside the dashed circle in Figure 5) for EDS measurement, and take the average value to obtain the average number of atoms in the central region X2.

[0163] Line scan: At least three lines are randomly selected in the central region (inside the dashed circle in Figure 5) for line scanning. The average value of the measurements is taken to obtain the average number of atoms in the central region, X1. At least three lines are randomly selected in the surface region (outside the dashed circle in Figure 5) for line scanning. The average value of the measurements is taken to obtain the average number of atoms in the central region, X2. In actual testing, spot scanning and line scanning can also be used in combination.

[0164] 3. The calculation method for the proportion of aggregates n / N is as follows:

[0165] After sample preparation, five cross-sectional views of the sample at different positions were taken at 3K magnification. The total number N of particles fully exposed in the field of view was counted, and the particle size in the view was measured using Nano Measure software. After measurement, the number n of agglomerates consisting of five or more particles with a diameter of less than 1 μm fully exposed in the field of view was counted, with the maximum distance between any two points in the agglomerate less than or equal to 4 μm. Finally, the agglomerate ratio n / N was calculated. It should be noted that the total number of particles N includes primary particles and agglomerate particles. It should be noted that the particle diameter of particles with a diameter of less than 1 μm refers to the diameter of the inscribed circle of a primary particle in the cross-sectional view of the cathode material. A particle fully appearing in the field of view of the electron microscope means that the outline of the particle is completely displayed in the electron microscope image, and the outline of the particle is not covered by other single crystal particles in the field of view or divided by the boundary of the electron microscope image. A primary particle refers to an independent particle in the cross-sectional view that has not formed an agglomerate with other primary particles. Aggregate particles refer to aggregate particles formed by the aggregation of 5 or more particles with a diameter of less than 1 micrometer.

[0166] 4. The test method for the specific surface area S1 of the cathode material is as follows:

[0167] The specific surface area was measured using a Micrometer (Mc) from the USA. The mass of the empty sample tube was measured as m1. 3g of sample was added to the sample tube through a long-necked funnel. The tube was degassed under vacuum at 300℃ for 1 hour. After cooling, the mass of the sample tube was measured as m2. The sample mass was calculated as m = m2 - m1. The sample tube was placed in liquid nitrogen, and the nitrogen adsorption capacity V was measured under a series of relative pressures P / P0, yielding adsorption isotherms. P / P0 was 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.

[0168] 5. The test method for the tap density ρ1 of the cathode material is as follows:

[0169] The tap density was tested using Dandong Baite BT-303: vibration rate 3000 times / min, vibration time 1min, vibration amplitude 3mm±0.1mm.

[0170] 6. The test method for the compacted density ρ2 of cathode material powder is as follows:

[0171] Using a Carver 4350 tester from the United States, 1g of sample was placed in a mold and pressed with a pressure of 6t for 30s. After pressing, the height was measured and the compaction density was calculated. The compaction density is the ratio of the sample mass to the volume after compaction.

[0172] 7. The particle size testing method for cathode materials is as follows:

[0173] The particle size of the cathode material was measured using a Malvern MS 3000 laser particle size analyzer. An appropriate amount of sample was taken, poured into pure water, and ultrasonically dispersed for 30 seconds at a power of 240 W. Then, an appropriate amount of sodium hexametaphosphate was added to the dispersed sample, stirred thoroughly, and poured into the sample cell of the testing equipment. After waiting 10 seconds, the sample was started by clicking "Start Sample Testing".

[0174] 8. The method for testing the average particle size of primary particles is as follows:

[0175] Five electron microscope (EM) images were taken at 3K magnification using a Hitachi S4800 scanning electron microscope at different positions. Alternatively, five cross-sectional EEM images were taken at 3K magnification using a cross-section of the sample at different positions. The EEM images were imported into Nano Measure software, and random measurements were performed using Nano Measure. The diameter of the circumcircle of the particle completely exposed in the field of view was taken as the particle size. At least 200 particles were counted, and the average value was taken as the average value for one batch of particles. A single-crystal particle completely appearing in the field of view of the EEM image means that the outline of the single-crystal particle is completely displayed in the EEM image, and the outline of the single-crystal particle is not covered by other single-crystal particles in the field of view or divided by the boundaries of the EEM image.

[0176] 10. The methods for testing cell volume and lattice strain are as follows:

[0177] The XRD diffractometer was used to test the XRD pattern in the range of 10°-70° with a speed of 1° / min and a step size of 0.005°. The XRD pattern was then refined by Rietveld using GASA to obtain information such as cell volume, cell parameters (a, c) and peak shape parameters. The lattice strain was calculated based on the obtained peak shape parameters according to equation (1).

[0178] Equation (1):

[0179] Where β is the full width at half maximum (FWHM), θ is the diffraction angle (both in radians), k is a constant of 0.89, λ is the X-ray wavelength of 0.154 nm, D is the grain size (in nm), and ε is the lattice strain, which is dimensionless.

[0180] 11. The ternary cathode material products obtained in the above embodiments and comparative examples were assembled into button cells and their performance was tested using the following methods.

[0181] The positive electrode material, conductive carbon black, and PVDF (polyvinylidene fluoride) binder were mixed in a mass ratio of 80:10:10. NMP (N-methylpyrrolidone) was then added to form a uniform slurry. This slurry was evenly coated onto aluminum foil and dried in a 100℃ oven for 12 hours. After drying, it was rolled under 10 MPa pressure and cut into circular electrode sheets with a diameter of 14 mm. The negative electrode used a 14 mm diameter Li metal sheet. The lithium-ion battery was assembled according to the industrial CR2025 button cell design. A Cellgard separator was used, and the electrolyte was a mixture of equal parts ethylene carbonate (EC), polycarbonate (PC), and diethyl carbonate (DEC) with 1 mol / L LiPF6 as the electrolyte. The positive electrode sheet, separator, negative electrode sheet, and electrolyte were assembled into a button cell in an Ar gas glove box with a water and oxygen content of less than 0.5 ppm.

[0182] Electrochemical cycle performance, capacity, rate performance, and initial efficiency (first-time efficiency) of the coin cells were tested. The charge-discharge cycle voltage range was 2.8V-4.35V, the current was 0.1C (20mAh / g), and the cycle test was conducted for 50 cycles at a 0.5C charge-1C discharge rate. Capacity is expressed in mAh / g, and initial efficiency is expressed as a percentage (%).

[0183] Capacity testing method: The electrical performance was tested using the Blue Electric testing system (charge and discharge voltage of 2.8 to 4.35V, temperature condition of 25℃). The device was charged at 0.1C and then discharged at 0.1C, with a constant voltage cutoff current of 0.005C. The discharge capacity (mAh / g) was calculated.

[0184] Cyclic test method: At 25℃ and with a charge / discharge voltage of 2.8~4.35V, the coin cell battery is charged and discharged at 0.5C / 1C for 50 cycles. The final capacity retention rate after 50 cycles is the cycle performance. The cycle retention rate can be obtained by dividing the discharge capacity of the 50th cycle by the discharge capacity of the first cycle.

[0185] Rate testing method: At 25℃ and with a charge / discharge voltage of 2.8~4.35V, the button cell is first charged and discharged at 0.1C for 2 weeks with a cutoff current of 0.005C, then charged and discharged at 0.33C for 1 week with a cutoff current of 0.05C, then charged and discharged at 0.5C for 1 week, then charged and discharged at 0.5C for 2 weeks with a cutoff current of 0.05C. The ratio of the capacity obtained by discharging at 2C to the capacity obtained by charging and discharging at 0.1C is the rate performance at 2C.

[0186] Gas generation value test of cathode material:

[0187] The positive electrode materials were assembled into a 2Ah soft-pack battery. The positive electrode formulation was positive electrode: binder: conductive agent = 96.8:1.2:2, and the negative electrode formulation was negative electrode (artificial graphite): binder: conductive agent = 95.6:1.4:3. The battery was stored in a 60℃ high-temperature oven for 7 days, and the gas production was tested by the water displacement method. The obtained gas production was the gas production per unit mass of soft-pack battery in 7 days, in mL / g. The specific method is as follows: The positive electrode material, PVDF, SP, and CNT are weighed in a mass ratio of 97.0:1.0:1.5:0.5. NMP is added at a solid content of 50% to form a viscous slurry. This slurry is then evenly coated onto aluminum foil using a scraper. After drying in an oven at 80℃, it is rolled and cut into 4cm × 8cm positive electrode sheets. The graphite negative electrode material, SP, CMC, and SBR are weighed in a mass ratio of 96:1.0:1.2:1.8, dispersed into a slurry, coated onto copper foil, and cut into 4cm × 8cm negative electrode sheets. The positive and negative electrode sheets are assembled into a basic soft-pack battery. The capacity of the soft-pack battery is controlled at 2Ah. After formation, it is charged to 50% SOC and then stored in a 60℃ oven for 7 days. The volume difference before and after storage is measured using the water displacement method, and the volume change rate is calculated, which is the indicator of gas production.

[0188] The test results are detailed in List 1 to Table 2. (D90-D10) / D50 is represented by the "Span value".

[0189] Table 1

[0190] Table 2

[0191] Table 4

[0192] From Tables 1 to 4 above, compared with Comparative Examples 1 to 5, in Examples 1 to 20, the cathode material contains element M (e.g., at least one of Na, K, Cs, Mg, Ca, Sr or Ba), and the concentrations X1 and X2 in the central region and surface region of the particles satisfy 1.2≤X2 / X1≤20. Combined with the fact that the proportion of agglomerates in the cathode material is less than 1%, the cathode material has good capacity and first-time efficiency, as well as good cycle performance and rate performance, and reduces the gas production of the secondary battery. After extensive experimentation, the inventors hypothesized that the concentration of element M in the particles satisfies 1.2 ≤ X2 / X1 ≤ 20, resulting in a higher content of element M near the particle surface. This increases the unit cell volume in the surface region, while the lower content near the particle center leads to a smaller unit cell volume. This creates compressive stress from the surface towards the center, which suppresses lattice volume changes during charging and discharging, inhibiting the generation or propagation of particle cracks. This, in turn, improves the gas generation performance and long-term cycle performance of the cathode material. Furthermore, considering the range of agglomerate proportions in this application, an appropriate amount of agglomerate particles can shorten the lithium-ion intercalation / deintercalation transport channel during charging and discharging, facilitating lithium-ion diffusion and reducing internal stress caused by lithium-ion intercalation / deintercalation. Additionally, the higher strength of agglomerate particles reduces particle breakage during electrode rolling, significantly reducing the exposed surface area of ​​fine powder and particles, thus improving gas generation and synergistically enhancing the cycle stability and rate performance of the secondary battery.

[0193] Please refer to Figure 3. In Figure 3(b), the content distribution of element K inside the particles in Comparative Example 2 is basically consistent, while the internal distribution of the particles in Example 1 shows differences, as shown in Figure 3(a), with more element K enriched in the region near the surface. Referring to Figure 4, Figure 4(a) shows fewer aggregates in Example 2, while Figure 4(b) shows more aggregates in Comparative Example 1.

[0194] Compared to Example 1, Comparative Example 1 used a co-precipitation method to prepare the cathode material precursor. The resulting cathode material did not contain element M, and the proportion of aggregates was relatively high. The capacity, first-time efficiency, and cycle performance of the cathode material all decreased, while the gas production increased.

[0195] Compared with Example 1, Comparative Example 2 uses a co-precipitation method to prepare the cathode material precursor, and K and Mg elements are solid-phase doped in step (3). The distribution of M element in the cathode material is more uniform, and the proportion of agglomerates is higher. The capacity, first efficiency and cycle performance of the cathode material are reduced, while the gas production is increased.

[0196] Compared with Example 1, no soluble element M was added in step (1) of Comparative Example 3, and the obtained cathode material does not contain element M. The capacity, first efficiency and cycle performance of the cathode material are reduced, while the gas production is increased.

[0197] Compared with Example 1, in step (1) of Comparative Example 4, soluble element M was added and the pyrolysis temperature was adjusted to 1000 degrees. Element M was enriched in the surface area of ​​the material. The capacity, first-time efficiency and cycle performance of the cathode material decreased, while the gas production increased.

[0198] Compared with Example 1, Comparative Example 5 uses a segmented sintering method in step (3), resulting in a higher agglomerate content in the cathode material, a decrease in the cathode material's capacity, first-time efficiency, and cycle performance, and an increase in gas production.

[0199] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A positive electrode material, characterized by, The cathode material includes element M, which is selected from at least one of Na, K, Cs, Mg, Ca, Sr, or Ba. The cathode material comprises multiple particles, each with a cross-section including a central region and a surface region. The cross-section of the particles is tested using an energy dispersive spectroscopy (EDS) instrument. The average concentration of element M in the central region is measured as X1, and the average concentration of element M in the surface region is measured as X2. X1 and X2 satisfy the condition: 1.2 ≤ X2 / X1 ≤ 20. The particles include primary particles and aggregated particles. A cross-sectional SEM image of the cathode material is obtained using a scanning electron microscope (SEM) at 3K magnification. The total number of primary particles and aggregated particles in the cross-sectional SEM image is N, and the number of aggregated particles is n. n and N satisfy the condition: n / N < 1%. The aggregated particles are formed by the aggregation of 5 or more primary particles with a particle size of less than 1 μm.

2. The positive electrode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) 3.3 ≤ X2 / X1 ≤ 9.5; (2) 9.5 ≤ X2 / X1 ≤ 19.8; (3) 1.2 ≤ X2 / X1 ≤ 5.4; (4) The ratio of X2 / X1 can be 1.2, 1.5, 2, 5, 7, 9, 10, 12, 14, 15, 16, 18, 19, 20 or within any range of the two values ​​mentioned above.

3. The positive electrode material of claim 1, wherein, The cathode material satisfies at least one of the following conditions: (1) 0.5% ≤ n / N < 1%; (2) 0.39% ≤ n / N < 1%; (3) n / N can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95% or within any two of the above values.

4. The positive electrode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) The maximum distance between any two points on the aggregated particles is less than 4 μm; (2) The maximum distance between any two points on the aggregated particles is less than or equal to 5 μm.

5. The cathode material of claim 1, wherein, Based on the mass of the cathode material, the concentration of element M is between 10 ppm and 400 ppm.

6. The cathode material of claim 1, wherein, The cathode material is a single-crystal material, and the average particle size of the primary particles is 1 μm to 5 μm.

7. The cathode material of claim 1, wherein, The lattice strain ε of the cathode material is less than 0.1%.

8. The cathode material of claim 1, wherein, The cathode material satisfies any one of the following conditions: (1) the positive electrode material has a general formula of Li a Ni b Co c Q d O2, wherein 0.95≤a≤1.2, 0 b+c+d=1, and the element Q is selected from at least one of Mn or Al; (2) the positive electrode material has a general formula of Li a Ni b Co c Q d M e N f O2, wherein 0.95≤a≤1.2, 0 b+c+d+e+f=1, element Q is selected from at least one of Mn or Al, element M is selected from at least one of Na, K, Cs, Mg, Ca, Sr or Ba, and element N is selected from at least one of Zr, Ti, Al, Co, Mg, W, Ce, Y.

9. The cathode material of claim 1, wherein, The cathode material also contains element N, which is selected from at least one of Zr, Ti, Co, Mg, W, Ce, and Y; based on the mass of the cathode material, the concentration of element N is less than 5000 ppm.

10. The cathode material of claim 1, wherein, The cathode material satisfies at least one of the following conditions: (1) the tap density p1 of the positive electrode material: p1 > 2.0 g / cm3 3 ; (2) the powder compaction density p2 of the positive electrode material: p2≥2.8 g / cm3 3 .

11. The cathode material of claim 1, wherein The volume distribution particle size width of the positive electrode material satisfies: 1.0≤(D90-D10) / D50≤1.

5.

12. The cathode material of claim 1, wherein, The specific surface area of the positive electrode material is 0.4 m 2 / g to 0.9 m 2 / g.

13. A positive electrode sheet, said positive electrode sheet comprising the positive electrode material as described in any one of claims 1 to 12.

14. A secondary battery, the secondary battery comprising a positive electrode sheet as described in claim 13, or comprising a positive electrode material as described in any one of claims 1 to 12.

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