Positive electrode material, positive plate and secondary battery

Abstract

The invention discloses a positive electrode material, a positive plate and a secondary battery, and relates to the technical field of secondary batteries. The positive electrode material comprises a lithium transition metal oxide, and the positive electrode material comprises a plurality of secondary particles; the pore size distribution curve of the positive electrode material comprises a first distribution peak, a second distribution peak and a third distribution peak, the most probable pore size corresponding to the first distribution peak is A, the most probable pore size corresponding to the second distribution peak is B, and the most probable pore size corresponding to the third distribution peak is C; the positive electrode material meets the following conditions: 1.0 nm < = A < 3.0 nm, 3.0 nm < = B < 10.0 nm, and 10.0 nm < = C < = 20.0 nm, so that the problem that the ternary positive electrode material in the prior art is difficult to consider the capacity, rate capability and cycling stability at the same time is solved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and more specifically, to a positive electrode material, a positive electrode sheet, and a secondary battery. Background Technology

[0002] Lithium-ion batteries are widely used in 3C products, power devices, and energy storage equipment due to their advantages such as low self-discharge rate, high charge-discharge efficiency, no memory effect, and long cycle life. The cathode material is a crucial component of lithium-ion batteries, and its performance directly affects the battery's electrochemical performance. To improve the capacity of cathode materials, the compaction density is often increased. However, increasing compaction density reduces electrode porosity, hindering electrolyte penetration, leading to capacity loss and decreased conductivity, thus affecting the battery's rate performance and cycle life. Furthermore, cathode material particles are prone to fracture under high voltage, increasing side reactions and compromising the battery's cycle stability and safety. Therefore, how to balance improving the capacity, rate performance, and cycle stability of cathode materials is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0003] The main objective of this invention is to provide a cathode material and a secondary battery to solve the problem that ternary cathode materials in the prior art are difficult to balance capacity, rate performance and cycle stability.

[0004] To achieve the above objectives, according to one aspect of the present invention, a cathode material is provided, the cathode material comprising a lithium transition metal oxide, and the cathode material comprising a plurality of secondary particles;

[0005] The pore size distribution curve of the cathode material includes a first distribution peak, a second distribution peak, and a third distribution peak. The most probable pore size corresponding to the first distribution peak is A, the most probable pore size corresponding to the second distribution peak is B, and the most probable pore size corresponding to the third distribution peak is C.

[0006] The cathode material satisfies the following conditions: 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, 10.0nm≤C≤20.0nm.

[0007] Furthermore, the half-width at half maximum (WHM) corresponding to the first distribution peak is a, the half-width at half maximum (WHM) corresponding to the second distribution peak is b, and the half-width at half maximum (WHM) corresponding to the third distribution peak is c.

[0008] The cathode material satisfies the following conditions: 0.2nm≤a<3.0nm, 0.01nm≤b<2.5nm, 5.0nm≤c<20.0nm.

[0009] Furthermore, the X-ray diffraction pattern of the cathode material includes (003) crystal plane diffraction peaks and (104) crystal plane diffraction peaks, and the cathode material satisfies at least one of the following characteristics:

[0010] (1) The peak intensity of the (003) crystal plane diffraction peak of the cathode material is I 003 The peak intensity of the (104) crystal plane diffraction peak of the cathode material is I. 104 The positive electrode material satisfies: 1.5 ≤ I 003 / I 104 ≤2.0;

[0011] (2) The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material is 0.13~0.20;

[0012] (3) The half-width of the (104) crystal plane diffraction peak of the cathode material is 0.20~0.28.

[0013] Furthermore, the cathode material satisfies at least one of the following characteristics:

[0014] (1) The volume distribution D50 of the cathode material is 2.0 μm to 10.0 μm;

[0015] (2) The volume distribution D50 of the cathode material before and after holding at 6T pressure for 30s has a change rate of 20%~30%;

[0016] (3) The volume percentage of particles with a diameter of less than 1 μm after holding the positive electrode material under a pressure of 1T for 30s is less than 1%.

[0017] Furthermore, the cathode material includes a coating layer located on at least a portion of the surface of the secondary particles, and the cathode material satisfies at least one of the following characteristics:

[0018] (1) The coating layer contains at least one element selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb;

[0019] (2) The average thickness of the coating layer is 2nm~50nm.

[0020] Furthermore, the general chemical formula of the cathode material is Li u Ni x Co y M z R v O2, wherein 0.95≤u≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, x+y+z+v=1, 0≤v<0.4, M is selected from Mn and / or Al, and R is selected from at least one of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, W, Ti, Sb, Ta, Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb.

[0021] Furthermore, the cathode material satisfies at least one of the following characteristics:

[0022] (1) The specific surface area of ​​the cathode material is 0.45 m². 2 / g~1.5m 2 / g;

[0023] (2) The mass content of free lithium in the cathode material is 500ppm~2500ppm;

[0024] (3) The pH value of the positive electrode material is 11.5~12.0;

[0025] (4) The ratio of the compaction density to the tap density of the cathode material is 1.3 to 2.3;

[0026] (5) The compaction density of the positive electrode material is 2.5 g / cm³. 3 ~3.3g / cm 3 ;

[0027] (6) The tap density of the positive electrode material is 1.2 g / cm³. 3 ~2.0g / cm 3 .

[0028] Furthermore, by preparing an electrode sheet from positive electrode material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 93:5:2, the rebound rate of the electrode sheet is ≤5%.

[0029] A second aspect of the present invention provides a positive electrode sheet comprising the positive electrode material provided in the first aspect.

[0030] A third aspect of the present invention provides a secondary battery, the secondary battery comprising the positive electrode material provided in the first aspect or the positive electrode sheet provided in the second aspect.

[0031] By applying the technical solution of this invention, and controlling the pore size distribution curve of the cathode material to include three peaks, each peak corresponding to a different pore size range, it is possible to effectively promote the full wetting of the electrolyte, while also helping to disperse external pressure, reduce internal stress concentration, prevent excessive deformation or breakage of the cathode material under high compaction, and ensure the structural stability of the cathode material. Furthermore, it can provide sufficient buffer space for deformation under high compaction, reducing the possibility of electrode rebound and helping to reduce the breakage of cathode material particles under high compaction, thereby simultaneously improving the capacity, rate performance, and cycle stability of the cathode material. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a secondary battery during charging according to an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of a secondary battery during discharge according to an embodiment of the present invention;

[0034] Figure 3The graph shows the pore size distribution of the cathode material in Example 1; where the horizontal axis represents the pore size (PoreWidth) in nm, and the vertical axis represents the rate of change of pore volume (Pore Volume) with pore size (dV / dw) in cm. 3 / g·nm;

[0035] Figure 4 for Figure 3 A partially enlarged view of the pore size distribution curve of the cathode material in Example 1 shown;

[0036] Figure 5 The pore size distribution curve of the cathode material in Comparative Example 4 is shown.

[0037] Figure 6 This is a particle size distribution curve of the cathode material in Example 1 after being held under a pressure of 1T for 30 seconds.

[0038] Figure 7 The particle size distribution curve of the cathode material in Comparative Example 3 after being held under a pressure of 1T for 30s is shown.

[0039] Explanation of reference numerals in the attached figures:

[0040] 100 - Electrode assembly; 101 - Positive electrode; 102 - Negative electrode; 103 - Separator membrane. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0042] As described in the background section of this invention, existing cathode materials suffer from difficulties in simultaneously achieving capacity, rate performance, and cycle stability. To address these issues, in a typical embodiment of this invention, a cathode material is provided. The cathode material comprises a lithium transition metal oxide and includes multiple secondary particles. The pore size distribution curve of the cathode material includes a first distribution peak, a second distribution peak, and a third distribution peak. The most probable pore size corresponding to the first distribution peak is A, the most probable pore size corresponding to the second distribution peak is B, and the most probable pore size corresponding to the third distribution peak is C. The cathode material satisfies the following conditions: 1.0 nm ≤ A < 3.0 nm, 3.0 nm ≤ B < 10.0 nm, and 10.0 nm ≤ C ≤ 20.0 nm.

[0043] Lithium transition metal oxides can be one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, or lithium nickel oxide. Specifically, the cathode material can be characterized by inductively coupled plasma optical emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS) to determine the presence of lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn) / aluminum (Al) and their elemental ratios, thus identifying the cathode material as a lithium transition metal oxide. Alternatively, the cathode material can be characterized by X-ray diffraction (XRD), where the XRD pattern reveals a layered α-NaFe structure. The structure and space group R-3m are used to characterize the cathode material as a lithium transition metal oxide.

[0044] The cathode material of the present invention comprises a plurality of secondary particles, each secondary particle including one primary particle. The secondary particles may be formed by the agglomeration of primary particles.

[0045] Pore ​​size distribution curves characterize the pore size distribution in porous materials, that is, how the pore volume of pores with different pore sizes changes with pore size in the material structure. The pore size distribution of the cathode material was measured using a nitrogen adsorption method. Specifically, Micromeritics Tristar II was used to perform N2 adsorption tests and calculate the adsorption capacity under different equilibrium pressures, obtaining isothermal adsorption curves, and then calculating the pore size distribution of the cathode material. In the pore size distribution curve, the horizontal axis represents pore size (nm), and the vertical axis represents the rate of change of pore volume (dV / dw) with pore size (cm). 3 / g·nm. The values ​​on the vertical axis reflect the density of pores around a certain pore size, i.e., the local rate of change of pore volume. In the pore size distribution curve, the location of the distribution peak refers to the local highest point that appears in the curve, i.e., the pore size region corresponding to the maximum rate of change of pore volume. These distribution peaks represent pore size regions in the material where the number of pores or pore volume is particularly concentrated. The most probable pore size corresponding to the distribution peak is the pore size at the location of the distribution peak, i.e., the pore size value with the highest pore frequency or pore volume change rate.

[0046] The pore size distribution curve of the cathode material of the present invention includes a first distribution peak, a second distribution peak, and a third distribution peak. The most probable pore size corresponding to the first distribution peak is A, meaning the cathode material contains a large number of pores with a pore size of A; the most probable pore size corresponding to the second distribution peak is B, meaning the cathode material contains a large number of pores with a pore size of B; and the most probable pore size corresponding to the third distribution peak is C, meaning the cathode material contains a large number of pores with a pore size of C.

[0047] This invention effectively promotes the full wetting of the electrolyte under high compaction conditions by controlling the pore size distribution curve of the cathode material to include three peaks, each corresponding to a different pore size range. Specifically, the first distribution peak (most probable pore size A) is located between 1.0 nm and 3.0 nm. The small pores of size A provide abundant tiny channels for the electrolyte, greatly promoting electrolyte permeability and enabling lithium ions to quickly insert and extract into the cathode material, thereby improving the capacity, rate performance, and charge / discharge rate of the cathode material. The second distribution peak (most probable pore size B) is located between 3.0 nm and 10.0 nm. The medium-sized pores of size B further optimize the lithium ion diffusion path of the cathode material, improve the wettability of the cathode material, and also help disperse external pressure, reduce internal stress concentration, prevent excessive deformation or breakage of the cathode material under high compaction, and contribute to improving the cycle stability of the cathode material. The third distribution peak (most probable pore size C) is between 10.0 nm and 20.0 nm. The presence of larger pores with a pore size of C provides sufficient buffer space for deformation under high compaction, so that the cathode material will not easily break when subjected to high compaction, reducing the possibility of electrode rebound. At the same time, the presence of larger pores can further effectively disperse stress and reduce local stress concentration, thereby helping to further improve the cycle stability of the cathode material.

[0048] Therefore, this invention controls the pore size distribution of the cathode material to satisfy 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm. This allows the cathode material to possess good electrolyte wettability and lithium-ion transport efficiency under high compaction conditions, reducing stress concentration between particles and preventing excessive deformation or breakage of the cathode material. This not only significantly improves the capacity and energy density of the cathode material but also reduces its internal resistance, enhancing its cycle stability, rate performance, and thermal stability. If the pore size distribution of the cathode material is too narrow, electrolyte flow is restricted, affecting the activation of the cathode material and the charge / discharge efficiency of the battery. It also increases the brittleness of the cathode material, leading to a higher electrode rebound rate and increasing the risk of internal failures in the secondary battery. Conversely, if the pore size distribution of the cathode material is too wide, it leads to structural instability and reduces the cycle stability of the cathode material.

[0049] Specifically, A can be a range of 1.0nm, 1.2nm, 1.4nm, 1.5nm, 1.7nm, 1.8nm, 2.0nm, 2.2nm, 2.4nm, 2.6nm, 2.8nm, 2.9nm, or any two of these; B can be a range of 3.0nm, 3.2nm, 3.5nm, 3.8nm, 4.0nm, 4.2nm, 4.5nm, 4.8nm, 5.0nm, 5.2nm, 5.4nm, 5.5nm, 5.8nm, 6.0nm, 6.5nm, 7.0nm, 7.5nm, 8nm, 8.5nm, 9.0nm, 9.5nm, 9.9nm, or any two of these; and C can be a range of 10.0nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20.0nm, or any two of these.

[0050] In some embodiments, the full width at half maximum (FWHM) of the first distribution peak is a, the FWHM of the second distribution peak is b, and the FWHM of the third distribution peak is c; the cathode material satisfies: 0.2nm≤a<3.0nm, 0.01nm≤b<2.5nm, 5.0nm≤c<20.0nm.

[0051] Half-peak width (HWW) refers to the horizontal distance between the point where the peak height is halfway down (i.e., 50% of the peak's maximum value) and the points where the peak intersects with either side of the peak. HWW reflects the pore size distribution width within the pore range corresponding to the distributed peak. Specifically, the HWW corresponding to the first distributed peak reflects the pore size distribution width corresponding to the first distributed peak, the HWW corresponding to the second distributed peak reflects the pore size distribution width corresponding to the second distributed peak, and so on, until the third distributed peak corresponds to the third distributed peak.

[0052] By controlling 0.2nm ≤ a < 3.0nm, the distribution width of smaller pores is narrower, which is beneficial for further promoting the rapid penetration of electrolyte molecules. By controlling 0.01nm ≤ b < 2.5nm, the distribution width of medium-sized pores is narrower, which helps to form an appropriate pore structure and reduces the structural looseness caused by excessive pore density, thus helping to further improve the structural stability of the material. By controlling 5.0nm ≤ c < 20.0nm, the distribution width of larger pores is wider, which helps to further disperse external forces and reduce excessive contact pressure between particles, thereby further reducing the risk of electrode rebound rate and particle breakage, and thus further improving the structural integrity and cycle stability of the cathode material.

[0053] Specifically, a can be a range of 0.2nm, 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 1.8nm, 2nm, 2.5nm, 2.8nm, 2.95nm, or any two of these; b can be a range of 0.01nm, 0.2nm, 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 1.8nm, 2nm, 2.2nm, 2.4nm, 2.49nm, or any two of these; and c can be a range of 5.0nm, 8nm, 10nm, 12nm, 15nm, 18nm, 19nm, 19.5nm, or any two of these.

[0054] In some embodiments, the X-ray diffraction pattern of the cathode material includes (003) crystal plane diffraction peaks and (104) crystal plane diffraction peaks, and the peak intensity of the (003) crystal plane diffraction peak of the cathode material is I. 003 The peak intensity of the (104) crystal plane diffraction peak of the cathode material is I. 104 The positive electrode material satisfies: 1.5 ≤ I 003 / I 104 ≤2.0. The peak intensity ratio of the (003) crystal plane diffraction peak and the (104) crystal plane diffraction peak can reflect the orderliness and stability of the internal layered structure of the cathode material. By controlling I 003 / I 104 The value of 1.5 to 2.0 indicates that the cathode material has good layered structure consistency and relatively high crystallinity, which is conducive to the insertion and extraction of lithium ions and can reduce the diffusion resistance of lithium ions in the cathode material, thereby further improving the rate performance and cycle stability of the cathode material.

[0055] Specifically, I 003 / I 104 It can be a range consisting of 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, or any two of them.

[0056] The half-width at half-maximum (HWHM) refers to the width of a diffraction peak when its intensity drops to half its peak value. HWHM reflects the arrangement of atoms and the degree of crystal defects. A smaller HWHM indicates a more ordered atomic arrangement, fewer crystal defects, a more stable crystal structure, higher internal structural consistency, and a narrower pore size distribution. In some embodiments, the HWHM of the (003) crystal plane diffraction peak of the cathode material is 0.13~0.20, indicating that the cathode material exhibits good crystal order and high crystallinity on the (003) crystal plane, which is beneficial for the rapid transport of lithium ions in the layered structure and helps to further improve the electrochemical performance of the cathode material, such as charge / discharge efficiency and cycle stability.

[0057] In some embodiments, the full width at half maximum (FWHM) of the (104) crystal plane diffraction peak of the cathode material is 0.20–0.28. Compared to the (003) crystal plane, the diffraction peak of the (104) crystal plane is generally related to small changes in the interlayer distance and intralayer atomic arrangement of the cathode material. By controlling the FWHM of the (104) crystal plane diffraction peak to 0.20–0.28, it is helpful to balance the structural stability of the cathode material during cycling, reduce capacity decay, and thus help to further improve the cycling stability of the cathode material.

[0058] Specifically, the full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material can be in the range of 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 or any two of them. The full width at half maximum (FWHM) of the (104) crystal plane diffraction peak can be in the range of 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28 or any two of them.

[0059] In some embodiments, the volume distribution D50 of the cathode material is 2.0 μm to 10.0 μm. The volume distribution D50 refers to the particle size corresponding to a cumulative volume distribution of 50%. By controlling the volume distribution D50 of the cathode material to be 2.0 μm to 10.0 μm, it is helpful to promote appropriate plastic deformation of the cathode material under high compaction, rather than breakage, which helps to further improve the cycle stability of the cathode material.

[0060] Specifically, the volume distribution D50 of the cathode material can be a range of 2.0 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10.0 μm or any combination thereof.

[0061] In some embodiments, the volume distribution D50 of the cathode material changes by 20% to 30% before and after holding at 6T pressure for 30s. This indicates that the cathode material has appropriate deformation after high compaction, and can undergo certain deformation during the holding period to adapt to high pressure conditions. However, it can also return to a considerable degree of its original state after the pressure is released, avoiding extreme breakage and rebound. This helps to improve the structural stability of the cathode material particles while increasing the electrode density, thereby further improving the cycle stability of the cathode material.

[0062] It should be noted that the volume distribution D50 of the cathode material is D1, the volume distribution D50 of the cathode material after holding at 6T pressure for 30s is D2, and the change rate of the volume distribution D50 of the cathode material before and after holding at 6T pressure for 30s is (D1-D2) / D1×100%.

[0063] Specifically, the change rate of the volume distribution D50 of the cathode material before and after holding at 6T pressure for 30s can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, or any combination thereof.

[0064] The volume percentage of particles smaller than 1 μm in the cathode material after holding at 1T pressure for 30s is less than 1%. The cathode material was pressure-crushed at 1T pressure for 30s to obtain crushed material. Characterization of the crushed material using laser particle size analysis showed that the volume percentage of particles smaller than 1 μm in the crushed material was less than 1%. This indicates that the cathode material can effectively maintain its particle morphology under lower pressure, helping to reduce the formation of fine particles and achieving a good balance between deformation and structural integrity under pressure, further improving the cycle life and safety of the cathode material. The volume percentage of particles smaller than 1 μm in the cathode material at 1T pressure can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.9%.

[0065] In some embodiments, the cathode material includes a coating layer located on at least a portion of the surface of the secondary particles, the coating layer comprising at least one element selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb; and / or, the thickness of the coating layer is 2 nm to 50 nm. By introducing specific coating elements into the cathode material and controlling the thickness of the coating layer, it is helpful to further optimize the surface properties and internal structural stability of the cathode material, thereby further improving the cycle performance and safety of the cathode material. Specifically, the average thickness of the coating layer is within the range of 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any combination thereof.

[0066] In some embodiments, the general chemical formula of the cathode material is Li u Ni x Co y M z R vO2, wherein 0.95≤u≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, x+y+z+v=1, 0≤v<0.4, M is selected from Mn and / or Al, and R is selected from at least one of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, W, Ti, Sb, Ta, Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. Wherein, R includes elements R1, R2, and R3, where element R1 is a dopant element, and elements R2 and R3 are the first and second coating elements, respectively. R1 is selected from at least one of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, W, Ti, Sb, Ta, Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. R2 and R3 are each independently selected from at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. By controlling the cathode material to satisfy the above specific chemical formula, it is helpful to further improve the electronic conductivity and structural stability of the cathode material, thereby further improving the capacity and cycle stability of the secondary battery.

[0067] In some embodiments, the specific surface area of ​​the cathode material is 0.45 m². 2 / g~1.5m 2 / g. By controlling the specific surface area of ​​the cathode material to meet the above requirements, it is helpful to further promote the efficient transport of lithium ions, while reducing surface side reactions and improving the high-rate charge-discharge performance and cycle life of the cathode material. Specifically, the specific surface area of ​​the cathode material can be 0.45m². 2 / g, 0.5m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1m 2 / g, 1.2m 2 / g, 1.4m 2 / g, 1.5m 2 / g or a range consisting of any two of them.

[0068] In some embodiments, the free lithium content of the cathode material is 500 ppm to 2500 ppm. By controlling the free lithium content in the cathode material to meet the above requirements, the content of free lithium is effectively controlled, the increase in internal resistance is effectively controlled, and thus the cycle stability of the secondary battery is further improved. Specifically, the free lithium content of the cathode material can be within the range of 500 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2200 ppm, 2400 ppm, 2500 ppm, or any combination thereof.

[0069] In some embodiments, the pH value of the positive electrode material is 11.5 to 12.0. Controlling the pH value of the positive electrode material to meet the above requirements helps reduce side reactions between the positive electrode material and the electrolyte, further improving the performance and lifespan of the secondary battery. Specifically, the pH value of the positive electrode material can be a range of 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, or any combination thereof.

[0070] In some embodiments, the ratio of the compacted density to the tapped density of the cathode material is 1.3 to 2.3. Controlling this ratio to meet the above requirements helps promote the structural stability of the cathode material under high compaction conditions and ensures sufficient electrolyte wetting, thus promoting the electrochemical reaction of the cathode material and further improving its rate performance. Specifically, the ratio of the compacted density to the tapped density of the cathode material can be within the range of 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, or any combination thereof.

[0071] In some embodiments, the compaction density of the cathode material is 2.5 g / cm³. 3 ~3.3g / cm 3 By controlling the compaction density of the cathode material to meet the above requirements, it is helpful to improve the energy density of the cathode sheet, thereby effectively increasing the capacity of the secondary battery. Specifically, the compaction density of the cathode material can be 2.5 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 3g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 3 or a range consisting of any two of them.

[0072] In some embodiments, the tap density of the positive electrode material is 1.2 g / cm³. 3 ~2.0g / cm 3 By controlling the tap density of the cathode material to meet the above requirements, it is helpful to enhance the compactness between particles, further improving the stability and cycle life of the secondary battery. Specifically, the tap density of the cathode material can be 1.2 g / cm³. 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 31.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 or a range consisting of any two of them.

[0073] In some embodiments, an electrode sheet is prepared by mixing positive electrode material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 93:5:2, with a rebound rate ≤5%. Specifically, the positive electrode material, conductive carbon black, and polyvinylidene fluoride are dispersed in an appropriate amount of solvent and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated onto a positive electrode current collector, and after drying, rolling, and slitting, an electrode sheet is obtained. After a standing time of 60 hours, the electrode sheet rebound rate is ≤5%. The electrode sheet rebound rate reflects the different degrees of deformation and recovery ability of the electrode sheet under pressure. The lower the electrode sheet rebound rate, the smaller the thickness change of the electrode sheet after decompression. This indicates that the positive electrode material particles undergo appropriate deformation under high pressure to reduce electrode rebound, while avoiding particle breakage or structural collapse caused by excessive deformation. This demonstrates that the positive electrode material still has good deformation and structural integrity under high pressure.

[0074] This invention does not limit the specific preparation process of the cathode material, as long as the above parameters are met. In some embodiments, the preparation method of the above cathode material includes the following steps:

[0075] S1, the first precursor, glucose, dopant and solvent are mixed and ultrasonically treated to obtain the first mixture; the first mixture is stirred and evaporated to remove the solvent to obtain the second precursor; the second precursor is mixed with lithium source and ground to obtain the first mixture.

[0076] S2, the first mixture is subjected to first sintering, second sintering and third sintering in sequence to obtain sintered products; wherein, the temperature of the second sintering is greater than the temperature of the third sintering and greater than the temperature of the first sintering.

[0077] S3, the sintered product is sieved to obtain the first intermediate product;

[0078] S4, the first intermediate product, the first coating agent and water are mixed to obtain a second mixture; the second mixture is filtered to remove water to obtain a third mixture; the third mixture is subjected to vacuum drying and fourth sintering in sequence to obtain the second intermediate product;

[0079] S5, the second intermediate product is mixed with the second coating agent, and after the fifth sintering, the cathode material is obtained.

[0080] This invention, by controlling the doping and coating process, facilitates the preparation of cathode materials with specific pore size distributions. Specifically, in step S1, glucose is introduced as an organic additive, which is oxidized and decomposed during the high-temperature sintering process in step S2. The generated small molecule gas escapes and leaves pores in the material, helping to increase the porosity of the cathode material, promote electrolyte penetration, reduce the internal resistance of the battery, and improve capacity. In step S2, by controlling the temperature of the three-stage sintering to ensure that the temperature of the second sintering is greater than or equal to the temperature of the first sintering, it is beneficial to promote solid-state reactions between particles, forming a denser material structure, reducing internal voids, and improving crystal integrity. On the other hand, it helps to further control the pore size distribution of the material, enhance the mechanical properties of the particles, balance the density of the structure and the elasticity of the particles, and reduce electrode rebound. In step S1, the introduction of dopants helps to adjust the binding strength between metal and oxygen in the material, optimize the crystal structure, and improve the mechanical properties of the material. For example, selecting elements with high metal-oxygen bond energy for doping can effectively enhance the structural stability and particle strength of the material, making it less prone to breakage under high compaction or cyclic strain, thereby reducing the risk of electrode rebound. In steps S4 and S5, the introduction of a first coating agent and a second coating agent helps enhance the integrity of the crystal structure on the surface of the cathode material, reduces oxygen loss in the crystals, and improves the chemical stability of the cathode material. The double-layer coating helps disperse stress at the microscopic level and buffers the mechanical impact on particles during high-pressure compaction or battery cycling, thereby further improving the mechanical stability and microstructural integrity of the cathode material. In summary, by controlling the above-mentioned process parameters, this invention helps optimize the porosity of the cathode material, obtaining a cathode material that meets the aforementioned pore size distribution, thus helping to simultaneously improve the capacity, rate performance, and cycle stability of the cathode material.

[0081] In some embodiments, in step S1, the molar ratio of the second precursor to the lithium source is (0.95~1.1):1, for example, a range consisting of 0.95:1, 1:1, 1.05:1, 1.1:1, or any two of these. The mass ratio of the first precursor to glucose is (10~300):1, for example, a range consisting of 10:1, 20:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, or any two of these. By controlling the amount of glucose added, it helps to promote uniform distribution of pores within the material. The mass ratio of the first precursor to the dopant is (10~350):1, for example, a range consisting of 10:1, 20:1, 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, or any two of these.

[0082] In some embodiments, in step S2, the first sintering, the second sintering, and the third sintering are all performed in an oxygen atmosphere. The temperature of the first sintering is 300°C to 600°C, for example, a range of 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, or any two of these ranges. The time for the first sintering is 1 hour to 9 hours, for example, a range of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or any two of these ranges. The temperature of the second sintering is 650°C to 950°C, for example, a range of 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, or any two of these ranges. The time for the second sintering is 2 hours to 9 hours, for example, a range of 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or any two of these ranges. The third sintering temperature is 300℃~600℃, for example, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃ or any combination thereof. The third sintering time is 5h~16h, for example, 5h, 8h, 10h, 12h, 15h, 16h or any combination thereof.

[0083] In step S4, the mass ratio of the first intermediate product to the first coating agent is 1:(0.001~1), for example, 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.03, 1:0.05, 1:0.1, 1:0.5, 1:1, or any combination thereof. The vacuum drying temperature is 150℃~250℃, for example, 150℃, 180℃, 200℃, 220℃, 240℃, 250℃, or any combination thereof. The vacuum drying time is 20h~28h, for example, 20h, 24h, 25h, 28h, or any combination thereof. The fourth sintering is carried out in an oxygen atmosphere, and the temperature of the fourth sintering is 300℃~850℃, for example, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 850℃ or any combination thereof.

[0084] In step S5, the mass ratio of the second intermediate product to the second coating agent is 1:(0.001~1), for example, 1:0.001, 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.03, 1:0.05, 1:0.1, 1:0.5, 1:1, or any combination thereof. The fifth sintering temperature is 300℃~850℃, for example, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 850℃, or any combination thereof.

[0085] This invention does not limit the specific type of reactants; for example, in some embodiments, the first precursor may be Ni. x Co y M z (OH)2 or Ni x Co y M z O, where 0.6≤x<1, 0<y<0.4, 0≤z<0.4, x+y+z=1, and M is Mn and / or Al. The lithium salt includes at least one of LiOH, LiOH·H2O, Li2CO3, Li2SO4, and LiO. The dopant contains element R1, specifically, the dopant includes at least one nitrate, sulfate, chloride, phosphate, or acetate of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, W, Ti, Sb, Ta, Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. The first coating agent includes element R2, and the second coating agent includes element R3. Specifically, the first and second coating agents are each independently selected from at least one hydroxide, oxide, nitrate, or sulfate of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb.

[0086] A second aspect of the present invention provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material of the first aspect.

[0087] The positive electrode sheet of the present invention includes a positive current collector and a positive electrode material active layer disposed on at least one surface of the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and polymer substrate. The positive electrode material active layer comprises the positive electrode material as described in the first aspect above.

[0088] The positive electrode material active layer also includes an adhesive for bonding the positive electrode active material particles to facilitate the formation of the film layer, and also to improve the bonding force between the positive electrode material active layer and the positive electrode current collector. In some embodiments, the adhesive may include, but is not limited to, at least one of polyvinyl alcohol, 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, or nylon.

[0089] The positive electrode material active layer may further include a conductive material, which includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, metal-based materials may include, but are not limited to, metal powders or metal fibers, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0090] In the specific preparation of the positive electrode sheet, the positive electrode material, conductive material, and binder can be dispersed in an appropriate amount of solvent and thoroughly stirred to form a uniform positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, rolling, and slitting, the positive electrode sheet is obtained. In one specific embodiment, the positive electrode active layer comprises, by mass percentage, 70% to 99% of the positive electrode material, 0.5% to 15% of the conductive agent, and 0.5% to 15% of the binder.

[0091] A third aspect of the present invention provides a secondary battery comprising the positive electrode sheet provided in the second aspect or the positive electrode material provided in the first aspect.

[0092] Due to the inclusion of the aforementioned high-performance positive electrode, this secondary battery possesses advantages such as high capacity, excellent rate performance, cycle stability, and thermal stability. The secondary battery can be a lithium-ion battery, sodium-ion battery, solid-state electrolyte battery, etc., and is not limited thereto.

[0093] Specifically, the secondary battery includes a casing, an electrode assembly, and an electrolyte. Both the electrode assembly and the electrolyte are located inside the casing.

[0094] The outer casing can be a packaging bag encapsulated with a 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.

[0095] Please see Figure 1 and Figure 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. For charging, please refer to [reference needed]. Figure 1 Active ions (such as lithium ions) are extracted from the lattice of the positive electrode material (such as a lithium-ion intercalation compound) in the positive electrode 101, pass through the electrolyte and the separator 103, reach the negative electrode 102, and insert into the lattice of the negative electrode material. For discharge procedures, please refer to [link to relevant documentation]. Figure 2Active ions (such as lithium ions) are deintercalated from the lattice of the negative electrode material of the negative electrode 102, pass through the electrolyte through the separator 103, reach the positive electrode 101 and are embedded in the lattice of the positive electrode material (such as lithium intercalation compound), generating electrons that travel from the negative electrode 102 to the positive electrode 101 through the external circuit. The reverse movement of electrons forms an electric current, which can be used by electrical appliances.

[0096] 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 the positive electrode 101, the separator 103, and the negative electrode 102.

[0097] The positive electrode 101 includes a positive current collector and a positive electrode material active layer disposed on at least one surface of the positive current collector. The positive current collector can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and polymer substrate. The positive electrode material active layer includes the positive electrode material described in the first aspect.

[0098] The negative electrode 102 includes a negative electrode current collector and an active layer of negative electrode material disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and polymer substrate.

[0099] The negative electrode active material layer includes a negative electrode material, which may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. 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, the present invention is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0100] The active layer of the negative electrode material also includes a binder to bond the negative electrode active material particles, thereby facilitating the formation of the film layer and improving the bonding force between the active layer of the negative electrode material and the negative electrode current collector. In some embodiments, the binder may include, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0101] The active layer of the negative electrode material may further include a conductive material, which includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, carbon-based materials may include, but are not limited to, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, metal-based materials may include, but are not limited to, metal powders or metal fibers, such as copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative, such as poly(p-phenylene), poly(p-phenylene dinitrile), or poly(p-phenylene imide).

[0102] The separator 103 includes a membrane layer with a porous structure, and its material includes, but is not limited to, at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, the separator 103 may be a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane, etc.

[0103] The electrolyte serves to conduct ions between the positive electrode 101 and the negative electrode 102. The electrolyte can be in one or more states, including gel, solid, and liquid. In some embodiments, the electrolyte is a liquid electrolyte solution. The liquid electrolyte solution serves to conduct active ions between the positive electrode 101 and the negative electrode 102. In some embodiments, the liquid electrolyte solution includes a lithium salt and an organic solvent. The lithium salt may be selected from, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium tris(trifluoromethanesulfonyl)methyllithium (LiC(SO2CF3)3), lithium dioxolaneborate (LiBOB), and lithium difluorophosphate (LiPO2F2). For example, LiPF6 is selected as the lithium salt because it provides high ionic conductivity and improves cycling characteristics. The organic solvent may be a carbonate compound, a carboxylic acid ester compound, an ether compound, a nitrile compound, other organic solvents, or combinations thereof. Examples of carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or combinations thereof.

[0104] In the preparation of secondary batteries, positive electrode sheets, separators and negative electrode sheets are wound or stacked to obtain battery cells. The battery cells are then encapsulated in pre-stamped aluminum-plastic films. After the encapsulated batteries are dried, electrolyte is injected into the dried batteries. The secondary batteries are then aged, formed and resealed to complete the preparation of the secondary batteries.

[0105] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0106] Example 1

[0107] The method for preparing the cathode material in this embodiment includes the following steps:

[0108] S1, Ni with a volume distribution D50 of 5.0 μm 0.84 Co 0.04 Mn 0.12 (OH)₂ was dispersed in 50 mL of water, followed by the addition of glucose and Zr(NO₃)₄. After sonication for 1 hour, the mixture was stirred at 80 °C until the solvent was completely evaporated, yielding the second precursor; wherein Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)₂ to glucose is 100:1, Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)2 to Zr(NO3)4 is 78:1. LiOH and the second precursor are pulverized and ground at a molar ratio of 1.04:1 to obtain the first mixture.

[0109] S2, the first mixture is calcined at 500°C for 4 hours in an oxygen atmosphere in a box furnace, then heated to 850°C for 8 hours, and then cooled to 650°C for 6 hours to obtain the sintered product.

[0110] S3. The sintered product is sieved through a 325-mesh sieve to obtain the first intermediate product.

[0111] S4, under nitrogen protection, the first intermediate product was added to 50 mL of water and stirred for 3 h to form suspension A. AlOOH was added to 50 mL of water and stirred for 3 h to form suspension B. Suspension B was then added to suspension A and stirred at room temperature for 5 h to form mixture C. The solvent was then filtered off to obtain the third mixture. The third mixture was heated at 200 °C for 24 h in a vacuum drying oven to obtain the composite material, which was stored in a PE bag and sealed with aluminum-plastic film. The mass ratio of the first intermediate product to AlOOH was 1:0.013. The composite material was sintered at 650 °C for 10 h in an oxygen-purified atmosphere to obtain the second intermediate product.

[0112] S5, the second intermediate product and H3BO3 are mechanically mixed at a mass ratio of 1:0.006, and sintered at 550°C for 10 hours in an oxygen-purified atmosphere to obtain the cathode material. The cathode material includes a matrix material, a first coating layer, and a second coating layer. The general chemical formula of the cathode material is Li. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0113] Example 2

[0114] The difference from Example 1 is that in step S1, Ni 0.84 Co0.04 Mn 0.12 With a mass ratio of (OH)2 to Zr(NO3)4 of 156:1 and other conditions remaining unchanged, the cathode material Li in this embodiment was obtained. 0.994 Ni 0.805 Co 0.049 Mn 0.117 (Zr-Al-B) 0.03 O2.

[0115] Example 3

[0116] The difference from Example 1 is that in step S1, Ni 0.84 Co 0.04 Mn 0.12 With a mass ratio of (OH)2 to Zr(NO3)4 of 39:1 and other conditions remaining unchanged, the cathode material Li in this embodiment was obtained. 0.989 Ni 0.801 Co 0.048 Mn 0.116 (Zr-Al-B) 0.035 O2.

[0117] Example 4

[0118] The difference from Example 1 is that in step S4, the first intermediate product is added to 50 mL of water and stirred for 3 hours to form suspension A. WO3 is then added to 50 mL of water and stirred for 3 hours to form suspension B. Suspension B is then added to suspension A and stirred at room temperature for 5 hours to form mixture C. The solvent is then filtered off to obtain the third mixture. The third mixture is heated at 200°C for 24 hours in a vacuum drying oven to obtain the composite material, which is stored in a PE bag and sealed with aluminum-plastic film. The mass ratio of the first intermediate product to WO3 is 1:0.013. Other conditions remain unchanged to obtain the positive electrode material Li of this example. 1.007 Ni 0.815 Co 0.049 Mn 0.118 (Zr-WB) 0.016 O2.

[0119] Example 5

[0120] The difference from Example 1 is that in step S4, the mass ratio of the first intermediate product to AlOOH is 1:0.0065; other conditions remain unchanged, resulting in the cathode material Li of this example. 1.002 Ni 0.812 Co 0.049 Mn 0.118 (Zr-Al-B) 0.021 O2.

[0121] Example 6

[0122] The difference from Example 1 is that in step S1, Zr(NO3)4 is replaced with Y(NO3)4, and Ni 0.84 Co 0.04 Mn 0.12 With a mass ratio of (OH)2 to Y(NO3)4 of 86:1 and other conditions remaining unchanged, the cathode material Li in this embodiment was obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Y-Al-B) 0.031 O2.

[0123] Example 7

[0124] The difference from Example 1 is that in step S1, LiOH and the second precursor are pulverized and ground at a molar ratio of 1.14:1; other conditions remain unchanged, and the positive electrode material Li of this example is obtained. 1.09 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0125] Example 8

[0126] The difference from Example 1 is that in step S1, LiOH and the second precursor are pulverized and ground at a molar ratio of 1:1; other conditions remain unchanged, resulting in the cathode material Li of this example. 0.955 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0127] Example 9

[0128] The difference from Example 1 is that in step S2, the first mixture is calcined at 500°C for 4 hours in an oxygen atmosphere in a box furnace, then heated to 700°C for 8 hours, and then cooled to 650°C for 6 hours to obtain the sintered product.

[0129] With other conditions remaining unchanged, the positive electrode material Li in this embodiment is obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0130] Example 10

[0131] The difference from Example 1 is that in step S2, the first mixture is calcined at 500°C for 4 hours in an oxygen atmosphere in a box furnace, then heated to 750°C for 8 hours, and then cooled to 650°C for 6 hours to obtain the sintered product.

[0132] With other conditions remaining unchanged, the positive electrode material Li in this embodiment is obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0133] Example 11

[0134] The difference from Example 1 is that in step S2, the first mixture is calcined at 500°C for 4 hours in an oxygen atmosphere in a box furnace, then heated to 800°C for 8 hours, and then cooled to 650°C for 6 hours to obtain the sintered product.

[0135] With other conditions remaining unchanged, the positive electrode material Li in this embodiment is obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0136] Example 12

[0137] The difference from Example 1 is that in step S2, Ni with a volume distribution D50 of 9.0 μm is used. 0.84 Co 0.04 Mn 0.12 (OH)₂ was dispersed in 50 mL of water, followed by the addition of glucose and Zr(NO₃)₄. After sonication for 1 hour, the mixture was stirred at 80 °C until the solvent was completely evaporated, yielding the second precursor; wherein Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)₂ to glucose is 100:1, Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)2 to Zr(NO3)4 is 78:1. LiOH and the second precursor are pulverized and ground at a molar ratio of 1.04:1 to obtain the first mixture.

[0138] With other conditions remaining unchanged, the positive electrode material Li in this embodiment is obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0139] Example 13

[0140] The difference from Example 1 is that in step S2, Ni with a volume distribution D50 of 3.5 μm is used. 0.84 Co 0.04 Mn 0.12 (OH)₂ was dispersed in 50 mL of water, followed by the addition of glucose and Zr(NO₃)₄. After sonication for 1 hour, the mixture was stirred at 80 °C until the solvent was completely evaporated, yielding the second precursor; wherein Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)₂ to glucose is 100:1, Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)2 to Zr(NO3)4 is 78:1. LiOH and the second precursor are pulverized and ground at a molar ratio of 1.04:1 to obtain the first mixture.

[0141] With other conditions remaining unchanged, the positive electrode material Li in this embodiment is obtained. 0.992 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0142] Example 14

[0143] The difference from Example 1 is that in step S5, the second intermediate product is directly sintered at 550°C for 10 hours in an oxygen-filled atmosphere to obtain the cathode material. The cathode material includes a matrix material and a first coating layer, and the general chemical formula of the cathode material is Li. 0.992 Ni 0.805 Co 0.049 Mn 0.116 (Zr-Al) 0.030 O2.

[0144] Comparative Example 1

[0145] The difference from Example 1 is that the sintered product is used as the cathode material in this comparative example, with the chemical formula Li. 1.02 Ni 0.827 Co 0.050 Mn 0.120 Zr 0.003 O2.

[0146] Comparative Example 2

[0147] The preparation method of the cathode material in this comparative example includes the following steps:

[0148] S1, Ni with a volume distribution D50 of 5.0 μm 0.84 Co0.04 Mn 0.12 (OH)₂ was dispersed in 50 mL of water, and then glucose was added. After sonication for 1 hour, the mixture was stirred at 80 °C until the solvent was completely evaporated to obtain the second precursor; wherein Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)2 to glucose is 100:1; LiOH and the second precursor are pulverized and ground at a molar ratio of 1.04:1 to obtain the first mixture;

[0149] S2, the first mixture is calcined at 500°C for 4 hours in an oxygen atmosphere in a box furnace, then heated to 850°C for 8 hours, and then cooled to 650°C for 6 hours to obtain the sintered product.

[0150] S3. The sintered product is sieved through a 325-mesh sieve to obtain the first intermediate product.

[0151] S4, under nitrogen protection, the first intermediate product was added to 50 mL of water and stirred for 3 h to form suspension A. AlOOH was added to 50 mL of water and stirred for 3 h to form suspension B. Suspension B was then added to suspension A and stirred at room temperature for 5 h to form mixture C. The solvent was then filtered off to obtain the third mixture. The third mixture was heated at 200 °C for 24 h in a vacuum drying oven to obtain the composite material, which was stored in a PE bag and sealed with aluminum-plastic film. The mass ratio of the first intermediate product to AlOOH was 1:0.013. The composite material was sintered at 650 °C for 10 h in an oxygen-purified atmosphere to obtain the second intermediate product.

[0152] S5, the second intermediate product and H3BO3 are mechanically mixed at a mass ratio of 1:0.006, and sintered at 550°C for 10 hours in an oxygen-purified atmosphere to obtain the cathode material. The cathode material includes a matrix material, a first coating layer, and a second coating layer. The general chemical formula of the cathode material is Li. 0.995 Ni 0.806 Co 0.049 Mn 0.117 (Al-B) 0.028 O2.

[0153] Comparative Example 3

[0154] The preparation method of the cathode material in this comparative example includes the following steps:

[0155] S1, Ni with a volume distribution D50 of 5.0 μm 0.84 Co 0.04 Mn 0.12(OH)₂ was dispersed in 50 mL of water, followed by the addition of glucose and Zr(NO₃)₄. After sonication for 1 hour, the mixture was stirred at 80 °C until the solvent was completely evaporated, yielding the second precursor; wherein Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)₂ to glucose is 100:1, Ni 0.84 Co 0.04 Mn 0.12 The mass ratio of (OH)2 to Zr(NO3)4 is 78:1. LiOH and the second precursor are pulverized and ground at a molar ratio of 1.04:1 to obtain the first mixture.

[0156] S2, the first mixture is calcined in an oxygen atmosphere in a box furnace at 500°C for 4 hours, then heated to 900°C and calcined for 8 hours, and then cooled to 650°C and calcined for 6 hours to obtain the sintered product.

[0157] S3. The sintered product is sieved through a 325-mesh sieve to obtain the first intermediate product.

[0158] S4, under nitrogen protection, the first intermediate product was added to 50 mL of water and stirred for 3 h to form suspension A. AlOOH was added to 50 mL of water and stirred for 3 h to form suspension B. Suspension B was then added to suspension A and stirred at room temperature for 5 h to form mixture C. The solvent was then filtered off to obtain the third mixture. The third mixture was heated at 200 °C for 24 h in a vacuum drying oven to obtain the composite material, which was stored in a PE bag and sealed with aluminum-plastic film. The mass ratio of the first intermediate product to AlOOH was 1:0.013. The composite material was sintered at 650 °C for 10 h in an oxygen-purified atmosphere to obtain the second intermediate product.

[0159] S5, the second intermediate product and H3BO3 are mechanically mixed at a mass ratio of 1:0.006, and sintered at 550°C for 10 hours in an oxygen-purified atmosphere to obtain the cathode material. The cathode material includes a matrix material, a first coating layer, and a second coating layer. The general chemical formula of the cathode material is Li. 0.985 Ni 0.804 Co 0.049 Mn 0.116 (Zr-Al-B) 0.031 O2.

[0160] Comparative Example 4

[0161] The difference from Example 1 is that in step S4, the mass ratio of the first intermediate product to AlOOH is 1:0.026; other conditions remain unchanged, resulting in the cathode material Li of this example. 0.972 Ni 0.788 Co 0.048 Mn0.114 (Zr-Al-B) 0.05 O2.

[0162] Test methods

[0163] 1. Specific surface area and pore size distribution curve test

[0164] The specific surface area and pore size distribution of the cathode material were measured by adsorption gas method. Specifically, a Tristar 3020 N2 adsorption tester was used to calculate the adsorption capacity under different equilibrium pressures through N2 adsorption tests, obtaining isothermal adsorption curves, and then calculating the specific surface area and pore size distribution of the cathode material. Specifically, a dry specific surface area tube was taken, and 1 / 2 to 2 / 3 of the volume of the tube bulb was weighed. Before testing, degassing treatment (removing moisture or impurities) was required. Degassing was performed using a vacuum heating method, setting the degassing temperature to 300℃ and the degassing time to 1 hour. After degassing, the tube was placed in a cooling tank or an external specific surface area tube holder for 20 minutes of cooling, followed by backfilling with gas for 5-10 seconds (depending on the situation, to avoid sample ejection and adhesion to the sample tube sidewall). Then, the sample tube was disassembled, quickly plugged with a rubber stopper, and subsequent testing was performed. The P / P0 ratio was set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. A fitted isothermal adsorption curve was used to calculate the monolayer saturated adsorption capacity Vm based on the slope and intercept. Then, the specific surface area and pore size were calculated based on Vm. Using the measured data, the pore size (Pore Width) was plotted on the x-axis, and the dV / dw Pore Volume was plotted on the y-axis, with units in cm. 3 The pore size distribution curve can be obtained by importing the value in g·nm into Origin and selecting Line+Symbol to plot the graph. The x-axis represents the pore size in nm, and the y-axis represents the rate of change of pore volume with pore size (dV / dw) in cm. 3 / g·nm.

[0165] Half-peak width test: Identify the first, second, and third distribution peaks in the pore size distribution curve, and determine the highest point of each distribution peak, i.e., the maximum value of the peak. Simultaneously, find the lowest points on both sides of the peak relative to the X-axis (pore size). At the highest point of the peak, draw a vertical line downwards to find the half-peak height. Then, from this half-peak height, draw horizontal lines to the left and right until these two lines intersect the two sides of the peak. The distance between the two points where these two horizontal lines intersect the two sides of the peak is the half-peak width. It should be noted that when identifying the first, second, and third distribution peaks, the peak must meet the following condition: at least one side of the peak must include a highest point, a lowest point, and the total number of points between the highest and lowest points must be ≥3, and there must be no inflection point between the highest and lowest points on one side of the peak. The lowest point is the point corresponding to the intersection of a line parallel to the X-axis with both sides of the bottom of the peak. The specific locations of the first, second, and third distribution peaks of the cathode material in Example 1 can be found in [reference needed]. Figure 3 and Figure 4 .

[0166] 2. XRD test

[0167] The sample was characterized by XRD using an X'Pert Powder XRD diffractometer with a scanning range of 10~90° and a scanning step of 0.05. The incident angle 2θ, half-maximum width and peak intensity of the (003) and (104) crystal planes were obtained using JADE software.

[0168] 3. Particle size test

[0169] The particle size distribution of the cathode material was tested using a Malvern laser particle size analyzer (Mastersizer 3000). D50 represents the particle size corresponding to a cumulative particle size distribution percentage of 50%. Specifically, an appropriate amount of sample was taken, poured into pure water, and ultrasonically dispersed evenly. Then, an appropriate amount of sodium hexametaphosphate (powder: surfactant = 1g: 1 drop) was added to the dispersed sample, stirred evenly, and poured into the sample cell of the testing equipment. After waiting for 10 seconds, the sample testing was started.

[0170] The particle size test after 1T pressure was conducted using a compaction density tester, model 4350, from Carver Corporation, USA. The procedure was as follows: 5g of sample was placed in a mold and pressed with 1T pressure for 30s. The crushed powder was then tested and characterized using a Malvern laser particle size analyzer to calculate the volume percentage of micro-powder particles with a diameter of less than 1μm after the cathode material was subjected to 1T pressure.

[0171] 4. Volume distribution D50 change rate test

[0172] The D50 particle size of the cathode material was measured using a Malvern MS3000 laser particle size analyzer (UK), and denoted as D1. The particle size at 6T was measured using a Carver 4350 compaction density analyzer (USA) and a Malvern MS3000 laser particle size analyzer (UK). Specifically, a certain mass (1.0g ± 0.0050g) of powder sample was placed in a metal sleeve and pressed into a tablet under 6T pressure for 30s. The tablet was then ground in a mortar and pestle, and its D50 particle size was measured and denoted as D2. The volume distribution D50 change rate was calculated using the formula: (D1 - D2) / D1 × 100%.

[0173] 5. Coating thickness test

[0174] The thickness of the coating layer was measured using a TEM (HT7700). Specifically, at a magnification of 50k-100k, the TEM's built-in scale was used to select 10 particles, and the thickness of the coating layer was measured at 3 locations for each particle. The average thickness of the coating layer was then obtained by averaging the measurements.

[0175] 6. Free lithium content test

[0176] The residual free lithium in the cathode material was determined using a Mettler Toledo G20S automatic potentiometric titrator. 5.0000±0.0050 g of sample was weighed, 100 mL of water was added, and the mixture was magnetically stirred for 10 min (450 r / min). The stirred liquid was centrifuged, and the supernatant was diluted to volume. The diluted sample was then tested using a potentiometric titrator. The amount of HCl consumed was determined based on the potential change, thus yielding the contents of LiOH and Li2CO3.

[0177] 7. pH value test

[0178] Equipment Model: Mettler FE28

[0179] Take approximately 5g of the positive electrode material sample, add 45mL of water, sonicate for 5 minutes, then remove and let stand for 10 minutes. After calibrating the pH meter, insert the composite electrode into the supernatant solution to be tested. Calculate the pH value of the solution based on the potential difference between the measuring electrode and the reference electrode.

[0180] 8. Tap density test

[0181] The cathode material was placed in the sample chamber of a CANTA tap density meter (CANTA, DAT-6-220, USA), with a sample weight of about 50g and a vibration count of 5000.

[0182] 9. Compacted density test

[0183] The compaction density was tested using a Carver 4350 compaction density tester. The procedure was as follows: 1g of sample was placed in the mold and pressed with a pressure of 3T for 30s. After pressing, the height was measured, and the compaction density was calculated. The unit is g / cm³.3 .

[0184] 10. Electrode Rebound Rate Test

[0185] The positive electrode material, conductive carbon black, and polyvinylidene fluoride of the examples and comparative examples were mixed evenly in a mass ratio of 93:5:2. N-methylpyrrolidone (NMP) was added and placed in a high-speed disperser. After dispersing for 20 minutes, a positive electrode slurry was obtained. The positive electrode slurry was evenly coated on aluminum foil using a scraper and dried at 85°C for 1 hour to obtain the positive electrode sample to be tested.

[0186] The positive electrode samples, which appeared to be in good condition and dry, were tested for thickness using a micrometer to ensure uniform thickness. Three qualified samples were then rolled using a roller press until the compacted density reached 3.4 g / cm³. 3 After rolling, qualified electrodes are visually inspected to ensure there are no foreign objects on the surface. A micrometer is used to measure and record the electrode thickness d1 corresponding to the specified compaction density for each electrode. Three measurement points are fixed for each electrode: point 1, point 2, and point 3. The electrodes are then placed in the electrode rebound test sample placement area at room temperature. The electrode thicknesses dt1, dt2, and dt3 at the three fixed points are measured and recorded after a 60-hour settling time. The electrode rebound rate is calculated using the following formula:

[0187] First point: Electrode rebound rate = (dt1-d1) / (d1-d0)×100%; Second point: Electrode rebound rate = (dt2-d1) / (d1-d0)×100%; Third point: Electrode rebound rate = (dt3-d1) / (d1-d0)×100%; d0 is the aluminum foil thickness, and then the average value of the electrode rebound rate of each of the three electrodes at three fixed points is taken.

[0188] 11. Electrochemical performance testing

[0189] The positive electrode material, acetylene black, and polyvinylidene fluoride of the examples and comparative examples were mixed evenly in a mass ratio of 93:5:2. N-methylpyrrolidone (NMP) was added and placed in a high-speed disperser. After dispersing for 20 minutes, a positive electrode slurry was obtained. The slurry was evenly coated on an aluminum sheet, dried, and pressed into a positive electrode sheet. A lithium metal sheet was used as the negative electrode sheet, and the 2032 coin cell was assembled in an argon-filled glove box.

[0190] Using the Land button cell testing equipment, the button cells were charged and discharged at 25°C and a current density of 0.1C, within a charge / discharge range of 3.0V to 4.3V. The initial charge capacity and initial discharge capacity at 0.1C were obtained. The initial coulombic efficiency at 0.1C was calculated as follows: initial coulombic efficiency at 0.1C = initial discharge capacity at 0.1C / initial charge capacity at 0.1C.

[0191] The coin cells were activated by charge-discharge cycles at 45°C and a 1C current density, within a charge-discharge range of 3.0V to 4.3V. After activation, the cells were placed on a battery cycle testing system. They were charged at a constant current rate of 1C to 4.3V, then charged at a constant voltage rate with the current gradually decreasing to 0.05C, and finally discharged at a 1C rate to 3.0V. This charge-discharge cycle was repeated 50 times. The discharge capacity Q1 at the first cycle and Q50 at the 50th cycle were measured. The 50-cycle capacity retention rate was calculated as Q50 / Q1 × 100%.

[0192] 12. Ratio Performance

[0193] The aforementioned coin cells were used to test the rate performance of the materials. Using the Land coin cell testing equipment, the cells were charged at a constant current rate of 0.5C to 4.30V, then charged at a constant voltage rate with the current gradually decreasing to 0.05C, and finally discharged at a discharge rate of 1C to 3.0V. The specific capacity at the 1C rate was recorded.

[0194] The aforementioned coin cells were used to test the rate performance of the materials. Using the Land coin cell testing equipment, the cells were charged at a constant current rate of 0.5C to 4.30V, then charged at a constant voltage rate with the current gradually decreasing to 0.05C, and finally discharged at a discharge rate of 2C to 3.0V. The specific capacity at the 2C rate was recorded.

[0195] The test results are shown in Tables 1, 2 and 3.

[0196] Table 1

[0197]

[0198] Table 2

[0199]

[0200] Table 3

[0201]

[0202] Figure 3 The figure shows the pore size distribution curve of the cathode material in Example 1. Figure 4 for Figure 3 A partially enlarged view of the pore size distribution curve of the cathode material in Example 1 is shown. Figure 5 The image shows the pore size distribution curve of the cathode material in Comparative Example 4. Based on... Figure 3 and Figure 4 It can be seen that the pore size distribution curve of the cathode material in Example 1 exhibits a multi-peak distribution. Figure 5It can be seen that the pore size distribution curve of the cathode material in Comparative Example 4 exhibits a single-peak distribution and a narrow pore size distribution, which affects the electrochemical performance of the cathode material. The study suggests that excessive surface coating of the cathode material in Comparative Example 4 may lead to the aggregation of surface coatings.

[0203] Figure 6 This is a particle size distribution curve of the cathode material in Example 1 after being held under a pressure of 1T for 30 seconds. Figure 7 This is a particle size distribution curve of the cathode material in Comparative Example 3 after being held under a pressure of 1T for 30 seconds. Based on... Figure 6 and Figure 7 It can be seen that the cathode material in Comparative Example 3 has raised peaks in the particle size range of 0.1~1.0μm. Due to the excessively high sintering temperature, the particles are harder and more brittle, and are prone to cracking and producing micro powder under high pressure.

[0204] According to Tables 1, 2, and 3, compared to Comparative Examples 1-4, the cathode materials of Examples 1-14 all satisfy the requirement that the pore size distribution curve includes a first distribution peak, a second distribution peak, and a third distribution peak. Furthermore, the most probable pore size A corresponding to the first distribution peak, the most probable pore size B corresponding to the second distribution peak, and the most probable pore size C corresponding to the third distribution peak satisfy the following conditions: 1.0 nm ≤ A < 3.0 nm, 3.0 nm ≤ B < 10.0 nm, and 10.0 nm ≤ C ≤ 20.0 nm. In contrast, the pore size distribution curve of Comparative Example 1 only has two distribution peaks, while Comparative Examples 2, 3, and 4 each have only one distribution peak. Compared to the cathode materials of Comparative Examples 1-4, the cathode materials of Examples 1-14 exhibit higher capacity retention and superior cycle performance and thermal stability after 50 cycles at 1C and 45℃.

[0205] Furthermore, compared to Example 9, Examples 1-8, in addition to satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy 1.5≤I 003 / I 104 ≤2.0, the 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention after 50 cycles of the cathode materials in Examples 1-8 were further improved.

[0206] Furthermore, compared to Example 10, Examples 1-8, while satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy the requirement that the half-width of the (003) crystal plane diffraction peak is 0.13~0.20. The 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention rate after 50 cycles of the cathode material in Examples 1-8 have all been further improved.

[0207] Furthermore, compared to Example 11, Examples 1-8, while satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy the requirement that the half-width of the (104) crystal plane diffraction peak is 0.20~0.28. The 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention rate after 50 cycles of the cathode material in Examples 1-8 have all been further improved.

[0208] Furthermore, compared to Example 12, Examples 1-8, while satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy the volume distribution D50 change rate of 20%~30%. The 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention rate after 50 cycles of the cathode material in Examples 1-8 have all been further improved.

[0209] Furthermore, compared to Example 13, Examples 1-8, while satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy the requirement that the volume percentage of particles with a diameter less than 1μm after holding at 1T pressure for 30s is <1%. The 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention rate after 50 cycles of the cathode material in Examples 1-8 have all been further improved.

[0210] Furthermore, compared to Example 14, Examples 1-8, while satisfying 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, and 10.0nm≤C≤20.0nm, further satisfy the requirement that the coating thickness is 2nm~50nm. The 0.1C discharge capacity, initial coulombic efficiency, 1C discharge capacity, 2C discharge capacity, and capacity retention rate after 50 cycles of the cathode material in Examples 1-8 have all been further improved.

[0211] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 includes a lithium transition metal oxide, and the cathode material includes a plurality of secondary particles; The pore size distribution curve of the cathode material includes a first distribution peak, a second distribution peak and a third distribution peak. The most probable pore size corresponding to the first distribution peak is A, the most probable pore size corresponding to the second distribution peak is B, and the most probable pore size corresponding to the third distribution peak is C. The cathode material satisfies the following conditions: 1.0nm≤A<3.0nm, 3.0nm≤B<10.0nm, 10.0nm≤C≤20.0nm.

2. The cathode material according to claim 1, characterized in that, The half-width at half maximum (WHM) of the first distribution peak is a, the half-width at half maximum (WHM) of the second distribution peak is b, and the half-width at half maximum (WHM) of the third distribution peak is c. The cathode material satisfies the following conditions: 0.2nm≤a<3.0nm, 0.01nm≤b<2.5nm, 5.0nm≤c<20.0nm.

3. The cathode material according to claim 1, characterized in that, The X-ray diffraction pattern of the cathode material includes (003) crystal plane diffraction peaks and (104) crystal plane diffraction peaks, and the cathode material satisfies at least one of the following characteristics: (1) The peak intensity of the (003) crystal plane diffraction peak of the cathode material is I. 003 The peak intensity of the (104) crystal plane diffraction peak of the cathode material is I. 104 The positive electrode material satisfies: 1.5 ≤ I 003 / I 104 ≤2.0; (2) The full width at half maximum (FWHM) of the (003) crystal plane diffraction peak of the cathode material is 0.13~0.20; (3) The half-width of the (104) crystal plane diffraction peak of the cathode material is 0.20~0.

28.

4. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The volume distribution D50 of the positive electrode material is 2.0 μm to 10.0 μm; (2) The volume distribution D50 of the cathode material before and after holding at 6T pressure for 30s has a change rate of 20%~30%; (3) The volume percentage of particles with a diameter of less than 1 μm after holding the positive electrode material under a pressure of 1T for 30s is less than 1%.

5. The cathode material according to any one of claims 1 to 4, characterized in that, The cathode material includes a coating layer located on at least a portion of the surface of the secondary particles, and the cathode material satisfies at least one of the following characteristics: (1) The coating layer contains at least one element selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb; (2) The average thickness of the coating layer is 2nm~50nm.

6. The cathode material according to any one of claims 1 to 4, characterized in that, The general chemical formula of the cathode material is Li. u Ni x Co y M z R v O2, wherein 0.95≤u≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, x+y+z+v=1, 0≤v<0.4, M is selected from Mn and / or Al, and R is selected from at least one of Zr, Mg, Sr, V, Y, Nb, B, S, Ba, W, Ti, Sb, Ta, Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb.

7. The cathode material according to any one of claims 1 to 6, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The specific surface area of ​​the cathode material is 0.45 m². 2 / g~1.5m 2 / g; (2) The free lithium content of the cathode material is 500ppm~2500ppm; (3) The pH value of the positive electrode material is 11.5~12.0; (4) The ratio of the compaction density to the tap density of the positive electrode material is 1.3 to 2.3; (5) The compaction density of the positive electrode material is 2.5 g / cm³. 3 ~3.3g / cm 3 ; (6) The tap density of the positive electrode material is 1.2 g / cm³. 3 ~2.0g / cm 3 .

8. The cathode material according to any one of claims 1 to 6, characterized in that, An electrode sheet is made by combining the positive electrode material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 93:5:2, and the rebound rate of the electrode sheet is ≤5%.

9. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 8.

10. A secondary battery, characterized in that, The secondary battery comprises the positive electrode material according to any one of claims 1 to 8 or the positive electrode sheet according to claim 9.

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