Positive electrode material, positive electrode sheet and battery

Abstract

Provided in the present application are a positive electrode material, a positive electrode sheet and a battery. The positive electrode material is a nickel-cobalt-lithium composite oxide, and the positive electrode material comprises secondary particles. The powder plasticity ratio of the positive electrode material is β, where 70%≤β<91%. The powder plasticity ratio β of the positive electrode material is measured according to the following test method: the plastic strain energy A of the positive electrode material and the elastic strain energy B of the positive electrode material are measured by using a UTM7305 automatic compaction density instrument, and β=A / (A+B)*100%. The positive electrode material provided in the present application has an excellent powder plasticity, such that the electrode sheet rebound rate of a positive electrode sheet prepared from the positive electrode material can be reduced, and the structural stability and cycle stability of the positive electrode material can be improved.

Description

Positive electrode materials and positive electrode sheets, batteries

[0001] This application claims priority to Chinese patent application filed on July 3, 2025, with application number 202510912307.7 and title "Positive Electrode Material and Positive Electrode Sheet, Battery", the entire contents of which are incorporated herein by reference. Technical Field

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

[0003] With the rapid development of the new energy industry, lithium-ion batteries, as core components, have been widely used in new energy development due to their superior high energy density, long cycle life, and excellent stability. As a key component of lithium-ion batteries, the cathode material directly affects the battery's core performance characteristics such as energy density, cycle life, and safety, and is crucial for enhancing the competitiveness of lithium-ion batteries. The compaction density of the cathode material is an important parameter closely related to the overall performance of the battery. Specifically, compaction density is closely related to the electrode's specific capacity, initial coulombic efficiency, internal resistance, and cycle retention rate.

[0004] As the compaction density of the cathode sheet increases, the compressive strength between the cathode material particles strengthens, leading to a reduction in the porosity of the cathode sheet. This reduces the cathode sheet's ability to absorb electrolyte, making it difficult for the cathode sheet to be fully wetted by the electrolyte. During battery cycling, insufficient electrolyte wetting exacerbates the polarization of the cathode material, resulting in accelerated battery capacity decay and increased internal resistance. Furthermore, high compaction density can cause large-scale breakage of the cathode material particles, reducing the initial coulombic efficiency, cycle stability, and safety.

[0005] Therefore, how to improve the compaction density of the cathode sheet while maintaining the structural stability of the cathode material is a technical problem that still needs to be solved.

[0006] Application content

[0007] This application provides a cathode material, a cathode sheet, and a battery. The cathode material of this application has excellent powder plasticity and high particle strength, which can reduce the electrode rebound rate of the cathode sheet prepared from the cathode material and improve the structural stability and cycle stability of the cathode material.

[0008] In a first aspect, this application provides a cathode material, the cathode material comprising a nickel-cobalt-lithium composite oxide, the cathode material comprising secondary particles;

[0009] The powder plasticity ratio of the positive electrode material is β, where 70% ≤ β < 91%;

[0010] The powder plasticity ratio β of the positive electrode material was measured according to the following test method:

[0011] 1g of cathode material was subjected to pressure using a UTM7305 automatic compaction density meter. The initial powder height of the cathode material under the applied pressure was H0. The pressure was gradually increased and then gradually decreased, and each pressure was held for 5 seconds. The powder height under each pressure was H0. n ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 30) is the deformation variable δ. n ; with δ n The x-axis represents the powder height, H. n The pressure it withstands is input into the Origin software as the vertical axis to obtain the compression-spring stress-strain curve. The compression-spring stress-strain curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material, β=A / (A+B)*100%.

[0012] Secondly, this application provides a positive electrode sheet, which includes the above-mentioned positive electrode material.

[0013] Thirdly, this application provides a battery, which includes a positive electrode material or the aforementioned positive electrode sheet.

[0014] Compared with the prior art, this application has the following advantages:

[0015] In this application, the powder plasticity ratio is the proportion of the work done by the cathode material to overcome plastic deformation (i.e., plastic strain energy A) in the sum of the work done to overcome plastic deformation and the work done to overcome elastic deformation (elastic strain energy B). By controlling the powder plasticity ratio of the cathode material within the range of 70% to 91%, it indicates that the proportion of elastic strain energy B in the cathode material is small, while the proportion of plastic strain energy A is relatively large. When the proportion of elastic strain energy B in the cathode material particles is low, it means that the cathode material is more likely to deform under lower stress and has lower resilience. This makes it easier for the cathode material particles to deform under the pressure of the electrode rolling to adapt to the stress between particle collisions and reduce the generation of particle cracks. At the same time, when the plastic strain energy A of the cathode material particles is high, the intermolecular forces within them are weaker. Therefore, the cathode material also has greater toughness and can maintain the integrity of the particle structure under high stress, which is beneficial for maintaining the structural stability of the cathode material particles under high compaction. This application controls the powder plasticity ratio of the cathode material to be in the range of 70% to 91%, so that the cathode material can have both high compaction density and high structural stability. The two complement each other and together enable the cathode material to be used under high compaction density, thereby improving battery capacity, first coulombic efficiency and cycle performance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 is a schematic diagram of the discharge state of the battery provided in the embodiment of this application.

[0018] Figure 2a is a graph showing the test data of the powder plasticity ratio of the cathode material provided in Example 1 of this application.

[0019] Figure 2b is a graph showing the test data of the powder plasticity ratio of the cathode material provided in Comparative Example 2 of this application.

[0020] Figure 3a is an electron microscope image of the cathode material provided in Embodiment 1 of this application.

[0021] Figure 3b is an electron microscope image of the cathode material provided in Embodiment 5 of this application.

[0022] Figure 4a is a graph of the average crushing force of the cathode material provided in Embodiment 1 of this application.

[0023] Figure 4b is a graph showing the average crushing force of the cathode material provided in Comparative Example 2 of this application.

[0024] Figure 5a is a comparison diagram of the positive electrode material provided in Example 1 of this application before and after powder compression.

[0025] Figure 5b is a comparison diagram of the positive electrode material provided in Comparative Example 2 of this application before and after powder compression. Detailed Implementation

[0026] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0027] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0028] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0029] For ease of understanding of this application, specific terms have been appropriately defined herein. Unless otherwise defined herein, scientific and technical terms used in this application have the meanings commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] This application provides a cathode material, which includes a nickel-cobalt-lithium composite oxide and secondary particles;

[0031] The powder plasticity ratio of the positive electrode material is β, and 70% ≤ β < 91;

[0032] The powder plasticity ratio β of the positive electrode material was measured according to the following test method:

[0033] 1g of cathode material was subjected to pressure using a UTM7305 automatic compaction density meter. The initial powder height of the cathode material under the applied pressure was H0. The pressure was gradually increased and then gradually decreased, and each pressure was held for 5 seconds. The powder height under each pressure was H0. n ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 30) is the deformation variable δ. n ; with δ n The x-axis represents the powder height, H. n The pressure it withstands is input into the Origin software as the vertical axis to obtain the compression-spring stress-strain curve. The compression-spring stress-strain curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material, β=A / (A+B)*100%.

[0034] In the specific testing process, a UTM7305 automatic compaction density meter was used to apply pressure to 1g of cathode material. The pressures were successively 100N, 1000N, 5000N, 10000N, 15000N, 20000N, 25000N, 20000N, 15000N, 10000N, 5000N, 100N, and 100N. Each pressure was held for 5 seconds, and the height of the cathode material powder was recorded at each pressure. The powder height under the first 100N pressure was H0, the powder height under the 1000N pressure was H1, and so on, with the powder height under the last 100N pressure being H... 12 ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 12) is the shape variable δ. n ; with δ n The x-axis represents the powder height, H. nThe pressure exerted during compression is used as the ordinate. The compression-rebound stress-strain curve is obtained by inputting the data into Origin software. The curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material. Referring to Figure 2a, in the compression-rebound stress-strain curve, curve P1 represents the compression segment, i.e., the curve representing the stage where the pressure gradually increases, corresponding to pressures of 100N, 1000N, 5000N, 10000N, 15000N, 20000N, and 25000N. Curve P2 represents the rebound segment, i.e., the curve representing the stage where the pressure gradually decreases, corresponding to pressures of 25000N, 20000N, 15000N, 10000N, 5000N, 1000N, and 100N. The plastic strain energy A is the integrated area between curves P1 and P2, and the elastic strain energy is the integrated area of ​​curve P2.

[0035] The cathode material of this invention includes a nickel-cobalt-lithium composite oxide. Specifically, the nickel-cobalt-lithium composite oxide 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 intramolecular plasma mass spectrometry (ICP-MS) to determine the presence of lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn) / aluminum (Al) and their elemental ratios to characterize the cathode material as a lithium transition metal oxide. The cathode material can also be characterized by X-ray diffraction (XRD). The XRD pattern showing that the cathode material has a layered α-NaFeO2 structure, a rock salt phase structure, a spinel phase structure, or a combination thereof characterizes the cathode material as a lithium transition metal oxide.

[0036] In this application, the powder plasticity ratio is the proportion of the work done by the cathode material to overcome plastic deformation (i.e., plastic strain energy A) to the work done to overcome plastic deformation and the work done to overcome elastic deformation (elastic strain energy B). By controlling the powder plasticity ratio of the cathode material within the range of 70% to 91%, it indicates that the proportion of elastic strain energy B in the cathode material is small, while the proportion of plastic strain energy A is relatively large. When the proportion of elastic strain energy B in the cathode material particles is low, it means that the cathode material is more likely to deform under lower stress and has lower resilience. This makes it easier for the cathode material particles to deform under rolling pressure to adapt to the stress between particle collisions and reduce the generation of particle cracks. At the same time, when the plastic strain energy A of the cathode material particles is high, the intermolecular forces within them are weaker. Therefore, the cathode material also has greater toughness and can maintain the integrity of the particle structure under high stress, which is beneficial for maintaining the structural stability of the cathode material particles under high compaction. This application controls the powder plasticity ratio of the cathode material to be in the range of 70% to 91%, so that the cathode material can have both high compaction density and high structural stability. The two complement each other and together enable the cathode material to be used under high compaction density, thereby improving battery capacity, first coulombic efficiency and cycle performance.

[0037] In some embodiments, the powder plasticity ratio β of the positive electrode material is 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 89%, 90%, 91%, or within any two of the above values. When the powder plasticity ratio of the positive electrode material is too low, meaning the particles are too elastic, under high compaction density, this leads to a higher electrode rebound rate, decreased electrochemical reaction efficiency, and may even cause internal short circuits, increased internal resistance, and increased risk of overheating or even fire. When the powder plasticity ratio of the positive electrode material is too high, the particles are too weak to withstand the interparticle compressive stress, causing the particles to easily break under high compaction density. This results in repeated formation of a solid electrolyte film on the particle surface, accelerated capacity decay of the positive electrode, and consequently, affects the stability of the electrode. Optionally, 70% ≤ β < 80%. Optionally, 80% ≤ β ≤ 90%.

[0038] In some embodiments, the plastic strain energy of the cathode material is A, where 4.5 J ≤ A ≤ 12 J. Specifically, the plastic strain energy of the cathode material is 4.5 J, 5 J, 6 J, 7 J, 8 J, 9 J, 10 J, 11 J, 12 J, or any two values ​​within the above range. By controlling the plastic strain energy A of the cathode material within the above range, this application achieves higher particle strength in the cathode material, enabling it to maintain particle structural stability under high stress, thereby facilitating the maintenance of structural stability of the cathode material particles under high compaction density.

[0039] In some embodiments, the elastic strain energy of the positive electrode material is B, where 0.6J ≤ B ≤ 2.1J. Specifically, the plastic strain energy of the positive electrode material is 0.6J, 0.8J, 0.9J, 1.0J, 1.2J, 1.4J, 1.6J, 1.8J, 1.9J, 2.0J, 2.1J, or any two values ​​within the above range. This application, by controlling the elastic strain energy B of the positive electrode material within the above range, allows the positive electrode material to easily deform under lower stress and exhibits lower resilience. This makes it easier for the positive electrode material particles to deform under the pressure of the electrode rolls to adapt to the stress between particle collisions, reducing the generation of particle cracks.

[0040] In some embodiments, the average crushing force of the cathode material is 5mN to 20mN, specifically 5mN, 7mN, 8mN, 10mN, 12mN, 15mN, 17mN, 18mN, 20mN, or any two of the above values. Controlling the average crushing force of the cathode material within this range can increase the particle structure stability of the cathode material under high compaction density, reduce particle breakage and pulverization, and ensure the stability of the lithium-ion transport channel. This application simultaneously regulates the average crushing force of the cathode material and the powder plasticity ratio; the two can work synergistically to further improve the particle structure stability under high compaction density, increase battery capacity, initial coulombic efficiency, and cycle performance, and also improve the service life and safety of the cathode material. Optionally, the average crushing force of the cathode material is 9mN to 15mN.

[0041] In some embodiments, the general chemical formula of the cathode material is Li. a Ni x Co y M z N b O2, wherein 0.95≤a≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, x+y+z+b=1, M includes Mn and / or Al, and N includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, Nb, Ba, Ta, and V.

[0042] In some implementation methods, the general chemical formula of the cathode material is Li. a Ni x Co y M z N bO2, wherein 0.95≤a≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, 0≤b<0.1, x+y+z+b=1, M includes Mn and / or Al, and N includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, Nb, Ba, Ta, and V.

[0043] Specifically, the value of 'a' can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.02, 1.05, 1.07, 1.09, 1.1, or any two of the above values. The value of 'x' can be 0.6, 0.7, 0.8, 0.9, 0.95, or 0.99, etc. The value of 'y' can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.38, or 0.39, etc. The value of 'z' can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.38, or 0.39, etc., or other values ​​within the above ranges, which are not limited here.

[0044] In some embodiments, in the XRD diffraction pattern of the cathode material, the full width at half maximum (FWHM) of the diffraction peaks of the (003) crystal plane of the cathode material is 0.13 to 0.20, specifically 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, or any two of the above values, without limitation. The FWHM of the diffraction peaks of the (104) crystal plane of the cathode material is 0.20 to 0.28, specifically 0.20, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, or any two of the above values, without limitation.

[0045] It should be noted that in XRD diffraction patterns, the half-width at half-maximum (WHM) of the diffraction peaks of crystal planes can reflect the arrangement of atoms and the degree of crystal defects in the crystal structure of cathode materials. Within a certain range, the smaller the WHM, the higher the degree of orderliness of surface atomic arrangement and the fewer defects in the crystal. In other words, the lower the degree of cation mixing in the layered crystal structure of the cathode material, the better the stability of the crystal structure. The WHM of the (003) and (104) crystal planes of the cathode material of this application are within the above range, which is beneficial to improving the structural stability of the cathode material, thereby increasing the average crushing force of the cathode material. The cathode material particles are not easily deformed, and the cathode material has appropriate elastic strain energy B, giving the cathode material a good powder plasticity ratio.

[0046] In some embodiments, the peak intensity of the diffraction peak of the (003) crystal plane of the cathode material is I. (003)The peak intensity of the diffraction peak of the (104) crystal plane of the cathode material is I. (104) The positive electrode material satisfies: 1.5 ≤ I (003) / I (104) ≤2.0; specifically, it can be 1.5, 1.6, 1.7, 1.8, 1.9, 1.95, 2.0 or any two of the above values, without limitation here.

[0047] In some embodiments, the cathode material includes secondary particles formed by the agglomeration of multiple primary particles. These secondary particles have a spherical or near-spherical structure and a roughly circular cross-section. The secondary particles contain pores, including mesopores and macropores. Understandably, an appropriate amount of porosity within the cathode material can increase the specific surface area, resulting in more contact sites between the cathode material and the electrolyte, which is beneficial for improving the cathode material's capacity. Furthermore, an appropriate amount of porosity can buffer the expansion stress generated by the primary particles during lithium insertion / extraction, reducing the formation of intergranular cracks between primary particles and improving the structural stability and cycle stability of the cathode material.

[0048] In some embodiments, the volume ratio of mesopores to macropores is L, where L is (3-25):1. Specifically, it can be 3:1, 5:1, 8:1, 10:1, 15:1, 20:1, 25:1, or any two of the above values, and is not limited thereto. Controlling the volume ratio of mesopores to macropores within the above range allows for better dispersion and relief of local stress by an appropriate amount of mesopores, thereby increasing the average crushing force of the cathode material particles. This enables better particle rebound during electrode rolling, improving elastic deformation capability. Simultaneously, a small number of macropores facilitates electrolyte penetration, improves lithium-ion transport efficiency, and better buffers expansion stress. Controlling the volume ratio of mesopores to macropores within the above range helps disperse and relieve high local stress, reduces the risk of particle breakage, and provides deformation space, allowing the cathode material to achieve a balance between high average crushing force and powder compressibility. Preferably, the volume ratio of mesopores to macropores is (5-15):1.

[0049] In some embodiments, the mesopores (pore size 2-50 nm) account for 55% to 95% of the total volume of all pores. Specifically, this can be 55%, 58%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any range of two of the above values, and is not limited herein. Preferably, the mesopores account for 75% to 95% of the total volume of all pores.

[0050] In some embodiments, the macropores (pore diameter greater than 50 nm) account for 3% to 35% of the total volume of all pores. Specifically, this can be 3%, 5%, 8%, 10%, 12%, 15%, 20%, 25%, 30%, 35%, or any range of two of the above values, and is not limited herein. When the macropore volume percentage is high, secondary particles are prone to breakage when the cathode material particles are subjected to external pressure, and cannot rebound after the external force is released, leading to increased plastic deformation. Preferably, the macropore volume percentage is 3% to 18% of the total volume of all pores.

[0051] In some embodiments, the most probable pore size of the cathode material is 1nm to 6nm and / or 10nm to 25nm, specifically 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 10nm, 15nm, 20nm, 25nm or within any two of the above values, and is not limited here.

[0052] In some embodiments, the secondary particles of the cathode material have a coating layer on their surface, the coating layer comprising nitrogen (N) element, and the material of the coating layer comprising a compound of N element, wherein the N element is selected from at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. The compound may be an oxide of N element, a hydroxide of N element, a phosphide of N element, or a lithium complex of N element, etc.

[0053] Understandably, the coating layer on the surface of secondary particles can reduce direct contact with the electrolyte, reduce the occurrence of side reactions, and thus improve the cycle stability of the cathode material. The coating layer on the surface of secondary particles can also improve the surface smoothness of the cathode material particles, improve particle flowability, and make the dispersion of the cathode material with the conductive agent and binder more uniform, which is beneficial to reducing the internal resistance of the cathode sheet.

[0054] In some embodiments, the thickness of the coating layer is 3nm to 20nm, specifically 3nm, 5nm, 8nm, 9nm, 10nm, 13nm, 15nm, 18nm, 20nm, or any two of the above values, and is not limited thereto. If the coating layer is <3nm, the contact inhibition effect between the positive electrode material and the electrolyte decreases. If the coating layer is >20nm, it will hinder Li + Migration of the cathode material leads to increased impedance, which in turn affects fast charging performance and cycle life. Controlling the thickness of the coating layer within the above-mentioned range can effectively reduce the side reactions between the cathode material and the electrolyte, and also effectively improve fast charging performance and cycle life.

[0055] In some embodiments, the scraping angle of the positive electrode material particles is between 10° and 80°. Specifically, it can be 10°, 20°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, or 80°, or other values ​​within the above range, which are not limited here. Controlling the scraping angle of the positive electrode material particles within the above range increases the fluidity of the particles and the uniformity of dispersion between the particles and the conductive agent and binder, which helps reduce the internal resistance of the positive electrode sheet. If the scraping angle α > 80°, the fluidity of the positive electrode material particles decreases, and the uniformity of dispersion between the particles and the conductive agent and binder decreases. If the scraping angle α < 10°, the good fluidity of the positive electrode material particles leads to relatively poor adsorption, insufficient adhesion between particles and between particles and the current collector, reduced contact quality between the positive electrode material and the positive electrode current collector, decreased electrochemical reaction efficiency, accelerated battery capacity decay, and increased internal resistance of the battery.

[0056] In some implementations, the specific surface area of ​​the cathode material is 0.4 m². 2 / g~1.5m 2 / g; specifically, it can be 0.4m 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m 2 / g, 0.7m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g, 1.5m 2 / g or any two of the above values, without limitation. Controlling the specific surface area of ​​the cathode material within the above range makes the contact sites between the cathode material and the electrolyte more abundant, which is beneficial to improving the capacity of the cathode material.

[0057] In some embodiments, the surface free lithium content of the cathode material is 500 ppm to 2300 ppm, specifically 500 ppm, 600 ppm, 700 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1500 ppm, 1800 ppm, 2000 ppm, 2300 ppm, or any two of the above values, and is not limited herein. Understandably, the surface free lithium of the cathode material mainly originates from Li2CO3 and LiOH. Controlling the surface free lithium content of the cathode material can reduce the corrosive effect of alkaline substances on the cathode material, protect the structural stability of the cathode material, and help improve the cycle stability of the cathode material.

[0058] In some embodiments, the pH value of the positive electrode material is 11.5 to 12.0, specifically 11.5, 11.6, 11.7, 11.8, 11.9, 12, or any two of the above values; no limitation is made here. Controlling the pH value of the positive electrode material within the above range can prevent the decomposition of residual alkali on the surface of the positive electrode material under high pressure, which would lead to the generation of gas during battery charging and discharging, thereby affecting the safety and lifespan of the battery.

[0059] In some embodiments, the tap density of the cathode material is 2.0 g / cm³. 3 ~3.1g / cm 3 Specifically, it could be 2.0 g / cm³. 3 2.2g / cm 3 2.3g / cm 3 2.5g / cm 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 Or within any two of the above values, without limitation. This application controls the tap density of the cathode material within the above range, which is beneficial to the utilization of the cathode material's capacity, improves energy density, and helps to improve the battery's capacity retention rate.

[0060] In some embodiments, the compaction density of the cathode material is 2.7 g / cm³. 3 ~3.6g / cm 3 Specifically, it could be 2.7 g / cm³. 3 2.8g / cm 3 2.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.3g / cm 33.4g / cm 3 3.5g / cm 3 3.6g / cm 3 Or within any two of the above values, without limitation. This application controls the compaction density of the cathode material within the above range, which is beneficial to the utilization of the cathode material's capacity, improves energy density, and helps to improve the battery's capacity retention rate.

[0061] In some embodiments, the ratio of the compaction density to the tap density of the cathode material is 1.15 to 1.5, specifically 1.15, 1.17, 1.2, 1.24, 1.25, 1.26, 1.27, 1.29, 1.3, 1.32, 1.35, 1.38, 1.4, 1.42, 1.45, 1.48, 1.5, or any two of the above values ​​within a range, and is not limited herein. When the ratio of compaction density to tap density is too low, the mass of the active material decreases, leading to a reduction in battery energy density and reduced battery range. When the ratio is too high, the porosity of the cathode sheet decreases, reducing its ability to absorb electrolyte. The cathode sheet becomes difficult to fully wet with electrolyte, and during battery cycling, insufficient electrolyte wetting exacerbates the polarization of the cathode material, accelerating battery capacity decay and increasing internal resistance.

[0062] In some embodiments, the volumetric cumulative particle size distribution of the particle size distribution determination is obtained using laser diffraction, D. 50 This represents the particle size at which the cumulative particle size distribution percentage reaches 50%. The median particle size D50 of the cathode material's volume distribution is 6μm to 12μm, specifically 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, or any two of the above values; no specific limitation is made here. Controlling the particle size D50 of the cathode material can improve lithium-ion transport efficiency, resulting in particles with superior electrochemical performance, and contributing to improved discharge capacity and rate performance of the cathode material.

[0063] In some embodiments, the positive electrode material, conductive carbon black, and polyvinylidene fluoride are prepared into a positive electrode sheet in a mass ratio of 8:1:1, and the electrode sheet rebound rate of the positive electrode is 3.0% to 20.0%. Thus, the fact that the electrode sheet prepared from the above-mentioned positive electrode material has a rebound rate of 3.0% to 20.0% indicates that the prepared electrode sheet has a low rebound rate, and the positive electrode material easily deforms during the rolling process to adapt to the stress between particle collisions.

[0064] In some embodiments, the positive electrode material, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 8:1:1 to form a positive electrode sheet, and the peel strength of the positive electrode sheet is 50 mN / mm to 500 mN / mm. Therefore, the peel strength of the positive electrode sheet prepared from the above-mentioned positive electrode material is 50 mN / mm to 500 mN / mm, indicating that the positive electrode material has good dispersibility during the slurry processing, and the interface between the positive electrode material and the current collector is strong, effectively resisting the expansion stress during charging and discharging, thereby helping to improve the cycle performance of the positive electrode material.

[0065] Secondly, this application provides a method for preparing a cathode material, comprising the following steps:

[0066] Step S10: The mixture containing nickel-cobalt-based precursor, lithium source and dopant is subjected to a first sintering treatment to obtain a first sintered product.

[0067] In some embodiments, the nickel-cobalt-based precursor is Ni x1 Co y1 M z1 The oxide or hydroxide, wherein 0.6≤x1<1, 0<y1<0.4, 0≤z1<0.4, x1+y1+z1=1, and M is selected from Mn and / or Al.

[0068] Specifically, the values ​​of x1 can be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.89, 0.90, 0.92, 0.95, or 0.99, etc.; the values ​​of y1 can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.19, 0.2, 0.25, 0.3, 0.35, or 0.39, etc.; and the values ​​of z1 can be 0.001, 0.01, 0.05, 0.1, 0.15, 0.19, 0.2, 0.25, 0.3, 0.35, or 0.39, etc., without any restrictions here.

[0069] In some embodiments, the lithium source includes at least one selected from lithium carbonate, lithium hydroxide, lithium acetate, lithium sulfate, lithium chloride, lithium nitrate, and lithium oxalate. Preferably, the lithium source is LiOH·H2O or lithium carbonate.

[0070] In some embodiments, the molar ratio of the nickel-cobalt-based precursor to the lithium source is 0.95 to 1.1, specifically 0.95, 0.96, 0.98, 0.99, 1.0, 1.02, 1.05, 1.08, or 1.1, etc., and is not limited thereto. Preferably, the molar ratio of the nickel-cobalt-based precursor to the lithium source is 1.03.

[0071] In some embodiments, the mass ratio of the nickel-cobalt-based precursor to the dopant is (350–30):1, specifically 350:1, 300:1, 250:1, 200:1, 150:1, 100:1, 50:1, 30:1, or any value between them, and is not limited herein. By controlling the amount of dopant added within the above range, this application helps to improve the structural order of the cathode material, thereby enabling the cathode material to possess both high capacity, high structural stability, and good cycle performance.

[0072] In some embodiments, the nickel-cobalt-based precursor is ground and pulverized in a mixture with the lithium source and dopant. Understandably, grinding and pulverizing can make the various components mix more evenly, thereby making the subsequent sintering reaction more complete and uniform. This is beneficial for reducing structural defects in the cathode material and improving the structural order of the cathode material.

[0073] In some embodiments, the dopant includes a compound of at least one selected from Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, Nb, Ba, Ta, and V. The compound can be an oxide, hydroxide, phosphide, or lithium complex oxide, etc., and is not limited thereto. Preferably, the dopant includes a compound of at least one selected from Y, W, Sr, Zr, La, Ti, Mg, Al, and Ta.

[0074] It should be noted that the metal elements in the dopant can replace the original metal ions in the precursor. By doping with different elements and doping amounts, the binding energy between the metal elements and oxygen elements can be controlled, thereby changing the crystal structure of the cathode material and exhibiting different particle strengths and plasticity. For example, doping with elements with high metal-oxygen bond energy can enhance structural stability, exhibit high particle strength, and resist material deformation, thus exhibiting low plastic deformation. Conversely, it exhibits high plastic deformation.

[0075] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere with an oxygen concentration ≥95%.

[0076] In some implementations, a single sintering process includes a first stage and a second stage of stepped heating and cooling.

[0077] In some embodiments, the temperature of the first stage is 650℃ to 950℃, specifically 650℃, 660℃, 680℃, 700℃, 740℃, 780℃, 800℃, 850℃, 900℃, or 950℃, or other values ​​within the above range, which are not limited here. The heat preservation time of the first stage is 1 hour to 9 hours, specifically 1 hour, 3 hours, 5 hours, 7 hours, 8 hours, or 9 hours, or other values ​​within the above range, which are not limited here.

[0078] In some embodiments, the temperature of the second stage is 400℃ to 600℃, specifically 400℃, 450℃, 480℃, 520℃, 540℃, 570℃, 580℃, or 600℃, etc., or other values ​​within the above range, which are not limited here. The heat preservation time of the second stage is 8h to 16h, specifically 8h, 10h, 12h, 14h, 15h, 16h, etc., or other values ​​within the above range, which are not limited here.

[0079] In this application, by precisely controlling the first sintering method of high temperature followed by low temperature, the secondary particles obtained by sintering can have both high strength and toughness. In the first stage of the first sintering (high temperature stage), the strength of the primary particles that make up the secondary particles can be improved. Then, in the second stage (low temperature stage), the grain structure of the primary particles becomes more regular and intergranular defects are reduced. Furthermore, in the low temperature stage, some pores inside the secondary particles fuse to form an appropriate amount of macropore structure, which can provide more lithium-ion transport channels. The appropriate pore distribution can better buffer expansion stress.

[0080] When the sintering temperature in the first stage is too high, it leads to a decrease in the internal porosity of the secondary particles (especially a significant decrease in the proportion of macropores) and an improvement in the integrity of the crystal structure, resulting in a dense and defect-free particle structure. However, the increased strength of the secondary particles makes them less prone to plastic deformation, leading to reduced plastic deformation and increased electrode rebound. When the sintering temperature in the first stage is further increased, melting occurs on the particle surface, increasing the number of internal stress concentration points, which in turn leads to a decrease in particle strength.

[0081] In some embodiments, the primary sintering product is sieved and stored in a polyethylene (PE) bag and sealed with an aluminum-plastic film.

[0082] In step S20, the suspension B containing the coating material is added to the suspension A containing the primary sintering product, and the mixture is stirred to obtain a mixture C. The mixture C is heated and stirred to remove the solvent, and the powder is dried to obtain the composite material.

[0083] In some embodiments, suspension A includes a primary sintering product and a solvent.

[0084] In some embodiments, suspension B includes a coating material and a solvent.

[0085] In some embodiments, the solvent may be water or ethanol, etc., and is not limited thereto.

[0086] In some embodiments, the coating material includes a compound of at least one of W, Al, Co, B, and Ti, without limitation thereof.

[0087] In this application, by coating the primary sintering product, the coating material can improve the integrity of the crystal structure on the surface of the cathode material, reduce lattice oxygen loss, and form a protective layer on the surface of the secondary particles. This core-shell structure can effectively disperse stress, maintain the structural stability of the secondary particles, and improve the particle strength and plasticity in both micro and macro aspects.

[0088] In some embodiments, the mass ratio of the primary sintering product to the coating material is 1:(0.001~1), specifically 1:0.001, 1:0.005, 1:0.01, 1:0.05, 1:0.08, 1:0.1, 1:0.5, 1:1, etc., which are not limited here.

[0089] In step S30, the composite material is subjected to a secondary sintering treatment under an oxygen-containing atmosphere to obtain a secondary sintered product.

[0090] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥95%.

[0091] In some embodiments, the temperature of the secondary sintering process is 300℃ to 850℃, specifically 300℃, 350℃, 380℃, 400℃, 450℃, 500℃, 550℃, 600℃, 750℃, 800℃, or 850℃, etc., or other values ​​within the above range, which are not limited here. Preferably, the temperature of the secondary sintering is 600℃.

[0092] In step S40, the suspension E containing the coating material is added to the suspension D containing the secondary sintering product, and the mixture is stirred to obtain the mixture F. The mixture F is heated and stirred to remove the solvent, and the powder is dried to obtain the composite.

[0093] In some embodiments, the secondary sintering product is added to 50 mL of water and stirred for 3 h to form a suspension D.

[0094] In some embodiments, the coating material is added to 50 mL of water and stirred for 3 h to form suspension E.

[0095] In some embodiments, suspension E is added to suspension D and stirred at room temperature for 5 hours to form mixture F.

[0096] In some embodiments, the solvent in suspension D and suspension E can be water or ethanol, etc., and is not limited here.

[0097] In some embodiments, the coating material includes a compound of at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb, without limitation thereof.

[0098] In some embodiments, the mass ratio of the secondary sintering product to the coating material is 1:(0.001 to 0.1), specifically 1:0.001, 1:0.005, 1:0.01, 1:0.05, 1:0.08, 1:0.1, etc., which are not limited here.

[0099] In some embodiments, the drying temperature is 80°C to 150°C, and the drying time is 3 hours to 24 hours.

[0100] In some embodiments, the compound is sieved and stored in a polyethylene (PE) bag and sealed with an aluminum-plastic film.

[0101] In step S50, the composite is subjected to three sintering processes under an oxygen-containing atmosphere to obtain the cathode material.

[0102] In some implementations, the oxygen concentration in the oxygen-containing atmosphere is ≥95%.

[0103] In some embodiments, the temperature for the three sintering processes is between 300°C and 850°C, specifically 300°C, 350°C, 380°C, 400°C, 450°C, 500°C, 550°C, 600°C, 750°C, 800°C, or 850°C, etc., or other values ​​within the above range, which are not limited here. Preferably, the temperature for the three sintering processes is 500°C.

[0104] In the technical solution of this application, by precisely controlling the first sintering method of high temperature followed by low temperature, the secondary particles obtained by sintering can have both high strength and toughness. In the first stage of the first sintering (high temperature stage), the strength of the primary particles that make up the secondary particles can be improved. Then, in the second stage (low temperature stage), the grain structure of the primary particles becomes more regular and intergranular defects are reduced. Combined with doping and coating processes, the prepared cathode material has a good powder plasticity ratio and high compressive strength. This can reduce the rebound of the material electrode, meet the requirements of high-precision manufacturing, improve the energy density of the battery, reduce the resistance of the battery, and effectively reduce the risk of particle breakage, fragmentation and irreversible deformation during the rolling process or battery cycling process, thereby improving the stability and cycle performance of the battery.

[0105] Thirdly, this application provides a battery comprising the positive electrode material described in the first aspect or a positive electrode material prepared according to the method for preparing the positive electrode material described above.

[0106] The battery provided in this application can be a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, electrode assembly, and electrolyte. Both the electrode assembly and electrolyte are located inside the casing. The casing can be a packaging bag sealed with an encapsulating film (such as an aluminum-plastic film), such as a pouch battery for secondary batteries.

[0107] In other embodiments, the secondary battery may also be a steel-cased battery, an aluminum-cased battery, etc.

[0108] Figure 1 is a schematic diagram of the discharge state of the battery provided in an embodiment of this application. As shown in Figure 1, the battery includes a casing and an electrode assembly. The electrode assembly includes a positive electrode 1, a negative electrode 2, and a separator 3, with the separator 3 disposed between the positive electrode 1 and the negative electrode 2. The electrode assembly can be a stacked structure, which is formed by alternating layers of the positive electrode 1, the separator 3, and the negative electrode 2.

[0109] In other embodiments, the electrode assembly can also be a wound structure, which is formed by sequentially stacking and winding a positive electrode, a separator, and a negative electrode.

[0110] In some embodiments, the positive electrode 1 includes a positive current collector 101 and a positive active material layer 102 disposed on at least one surface of the positive current collector 101, wherein the positive active material layer 102 includes the aforementioned positive electrode material.

[0111] In some embodiments, the positive electrode current collector 101 can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and the polymer substrate. The positive electrode active material layer 102 comprises a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material is the positive electrode material of the first aspect described above or a positive electrode material prepared according to the above-described method for preparing the positive electrode material.

[0112] In some embodiments, the conductive agent is one of conductive carbon black, graphene, carbon nanofibers, Ketjen black, graphite, acetylene black, and the two-dimensional inorganic compound MXene.

[0113] In some embodiments, the binder is one of sodium carboxymethyl cellulose, cyclodextrin, styrene-butadiene rubber latex, polyacrylate, and polyvinylidene fluoride.

[0114] In some embodiments, the positive electrode has a rebound rate of 3.0% to 20.0%, specifically 3%, 5%, 8%, 9%, 10%, 12%, 15%, 18%, 19%, 20%, or within any two of the above values.

[0115] In some embodiments, the electrode peel strength of the positive electrode is 50mN / mm to 500mN / mm, specifically 50mN / mm, 60mN / mm, 80mN / mm, 100mN / mm, 150mN / mm, 200mN / mm, 250mN / mm, 300mN / mm, 350mN / mm, 400mN / mm, 450mN / mm, 500mN / mm, or within any two of the above values.

[0116] In some embodiments, the negative electrode 2 includes a negative electrode current collector 201 and a negative electrode active material layer 202 disposed on at least one surface of the negative electrode current collector.

[0117] In some embodiments, the negative electrode current collector 201 may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil and polymer substrate.

[0118] In some embodiments, the negative electrode active material layer 202 includes a negative electrode material, which includes, but is not limited to, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0119] The battery provided in this application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion. The battery can be a lithium-ion battery, a sodium-ion battery, a solid-state electrolyte battery, etc., and is not limited thereto.

[0120] The embodiments of this application will be further described below with reference to several examples. However, the embodiments of this application are not limited to the specific embodiments described below. Appropriate modifications can be made within the scope of the main claims.

[0121] Test method:

[0122] 1) Powder plasticity ratio β test of cathode material:

[0123] 1g of cathode material was subjected to pressure using a UTM7305 automatic compaction density meter. The initial powder height of the cathode material under the applied pressure was H0. The pressure was gradually increased and then gradually decreased, and each pressure was held for 5 seconds. The powder height under each pressure was H0. n ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 30) is the deformation variable δ. n ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 30) is the deformation variable δ. n ; with δ n The x-axis represents the powder height, H. nThe pressure it withstands is input into the Origin software as the vertical axis to obtain the compression-spring stress-strain curve. The compression-spring stress-strain curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material, β=A / (A+B)*100%.

[0124] For example, in this application, a UTM7305 automatic compaction density meter was used to apply pressure to 1g of cathode material at pressures of 100N, 1000N, 5000N, 10000N, 15000N, 20000N, 25000N, 20000N, 15000N, 10000N, 5000N, 100N, and 100N. The pressure was held for 5 seconds at each pressure, and the height of the cathode material powder was recorded at each pressure. The powder height at the first 100N pressure was H0, the powder height at the 1000N pressure was H1, and so on, with the powder height at the last 100N pressure being H... 12 ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 12) is the shape variable δ. n ; with δ n The x-axis represents the powder height, H. n The pressure experienced during compression is used as the ordinate. In Origin software, click Plot, Line+Symbol, Line+Symbol sequentially to obtain the compression-rebound stress-strain curve. When n takes any natural number between 1 and 6, it represents the complete compression process. Then, click Analysis, Mathematics, Integrate, Open Dialog sequentially to integrate the compression stress-strain curve (refer to Figure 2, curve P1). The absolute value of the integral is the total stress-strain work A+B of the cathode material. When n takes any natural number between 6 and 12, it represents the rebound process. Then, click Analysis, Mathematics, Integrate, Open Dialog sequentially to integrate the rebound stress-strain curve (refer to Figure 2, curve P2). The absolute value of the integral is the elastic strain energy B of the cathode material.

[0125] β = A / (A+B)*100%.

[0126] Referring to Figure 2a, in the compressive stress-strain curves, curve P1 represents the compression segment, i.e., the stage where the pressure gradually increases, corresponding to pressures of 100N, 1000N, 5000N, 10000N, 15000N, 20000N, and 25000N. Curve P2 represents the rebound segment, i.e., the stage where the pressure gradually decreases, corresponding to pressures of 25000N, 20000N, 15000N, 10000N, 5000N, 1000N, and 100N. The plastic strain energy A is the integral area between curves P1 and P2, and the elastic strain energy is the integral area of ​​curve P2.

[0127] 2) Average crushing force test of cathode material:

[0128] The crushing force of cathode particles was measured using a DUH-211S dynamic microhardness tester. For example, in this application, the strength of cathode material particles was tested using a Shimadzu dynamic microhardness tester. After selecting a particle with the test probe, a certain pressure was applied to the particle. The particle deformed under the action of pressure and resistance, and the instrument recorded the degree of deformation. When the particle broke, the applied pressure stopped; this was the maximum pressure the particle could withstand, i.e., the crushing force. The crushing force of 16 randomly selected particles with a diameter ≥ 5 μm was measured, and the average crushing force of the cathode material was obtained by averaging the results.

[0129] 3) Testing of metallic elements in the cathode material:

[0130] Dissolve 0.3g of the sample to be tested in aqua regia, cool and dilute to a volume of 100ml to prepare the test stock solution; take 1mL of the test stock solution, dilute it 100 times, and test the contents of the main elements Li, Ni, Co, Mn and Al by ICP, as well as the contents of other elements such as element N. All determinations are performed using an Agilent 5110 ICP-OES detection instrument.

[0131] 4) Test of specific surface area and pore distribution of cathode material:

[0132] The specific surface area and pore size distribution of the cathode material were measured by adsorption gas 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 to calculate the specific surface area and pore size distribution of the cathode material. Specifically, the specific surface area / pore size distribution of the material was tested according to GB / T 19587-2017 "Determination of Specific Surface Area / Porosity of Solid Substances by Gas Adsorption BET Method": A dry specific surface area tube was taken, and 1 / 2 to 2 / 3 of the volume of material in the tube bulb was weighed. Degassing treatment (removal of moisture or impurities) was required before testing, which could be performed using vacuum heating or nitrogen purging (vacuum heating method: set the degassing temperature to 300℃, degassing time to 1 hour, and after degassing, place the tube in a cooling tank or on an external specific surface area tube rack for 20 minutes to cool). After backfilling with gas for 5-10 seconds (depending on the situation, to avoid sample ejection and sticking to the side wall of the sample tube), the sample tube is then disassembled, and the sample tube is quickly plugged with a rubber stopper before proceeding with subsequent tests; Nitrogen removal purging method: Set the degassing temperature to 300℃ and the degassing time to 1 hour. After purging, place the sample tube in a cooling tank or on an external specific surface area tube holder for 20 minutes before quickly removing the rubber stopper and the degassing needle. Then quickly plug the rubber stopper again to prevent air from entering; Perform the determination according to the instruction manual of the specific surface area / pore size analyzer.

[0133] 5) XRD test:

[0134] The samples were characterized using an XRD diffractometer (RIGAICU UITIMAIV) with a scanning range of 10–90° and a scanning step size of 0.05°. The incident angle (2θ), interplanar spacing (d), and full width at half maximum (FWHM) of the characterized samples were read using Jade software, and I was calculated using the Scherer formula. 003 and I 104 The value. 6) The thickness of the coating layer of the positive electrode material:

[0135] Focused ion beam (FIB) was used to thin the cross-section of the cathode material sample to obtain a flat and transparent cross-section. At the same time, the thickness of the coating layer was measured by transmission electron microscopy (TEM) (HT7700). Specifically, 15 particles were randomly selected at magnification of 50k-100k, and the thickness of the coating layer was measured using the TEM's built-in scale. The average thickness was taken as the thickness of the cathode material coating layer.

[0136] 7) Testing the particle scraping angle of the positive electrode material:

[0137] The scraping angle of the particles was determined using the Hosokawa PT-X comprehensive particle analyzer. For example, in this application, 200-300cc of sample was gently placed into the sieve and the sieve heightening sleeve. Then, the vibration conditions were set and vibration was started (default settings: amplitude 1.5mm, time: 180s). After vibration, the receiving tray was lowered, and then the angle before impact was measured. After the measurement, impact was performed, and the angle after impact was measured. After the measurement, the scraping angle was calculated: scraping angle = (angle before impact + angle after impact) / 2.

[0138] 8) Test of the surface free lithium content of the cathode material:

[0139] 5.0 g of positive electrode material powder was immersed in 100 mL of deionized water and stirred for 10 minutes in a sealed glass flask. After thorough stirring, the suspension was filtered to obtain a clear solution. Then, 90 mL of the clear solution was titrated with 0.1 mol / L HCl solution at a rate of 0.5 mL / min while stirring, and the pH curve was recorded until the pH reached 3. The reference voltage curve was obtained by titrating to determine the low concentrations of LiOH and Li₂CO₃ dissolved in the deionized water. The first plateau with an endpoint y₁ (in mL) between pH 8 and 9 is the determined OH content. - The mass content of H2O, with a second plateau of endpoint y2 (in mL) between pH 4 and 6, is a definite indicator of HCO3-. - / H2CO3 mass content. The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau were obtained by the corresponding minimum values ​​of the derivative dpH / dVol of the pH curve. The results were then expressed as weight percentages of LiOH and Li2CO3 as shown in equations (1) and (2) below: Free Li wt%=LiOHwt%*6.94 / 23.95+Li2CO3wt%*6.94*2 / 73.89 (3)

[0140] 9) pH test of positive electrode material:

[0141] 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.

[0142] 10) Tap density test of cathode material:

[0143] The following steps were taken using a Canta vibratory density meter (model: DAT-4-220):

[0144] Clean the graduated cylinder and weigh it to obtain m1. Add approximately 50g of sample to the graduated cylinder, ensuring the sample surface is as horizontal as possible, and wipe the surrounding area with a paper towel. Weigh the total mass of the sample and graduated cylinder to obtain m2. Place the graduated cylinder on the vibration stage and secure it with the three symmetrical feet. Turn on the instrument and set the vibration frequency to 5000 times. Turn on the vibration switch; the instrument will automatically stop after vibrating for the specified number of times. Remove the graduated cylinder and read the sample volume. If the sample surface is horizontal after compaction, read the volume directly; if it is oblique, take the average of the readings at the highest and lowest points, V. The compacted density = (m2 - m1) / V.

[0145] 11) Testing the compaction density of the cathode material:

[0146] The compaction density of the cathode material was tested using a Carver 4350 from the United States. The procedure was as follows: 1g of sample was placed in a mold and pressed with a pressure of 3T for 30s. After pressing, the height was measured and the compaction density was calculated, which is the ratio of mass to volume after compaction.

[0147] 12) Particle size testing of cathode materials:

[0148] Using a Malvern Mastersizer 3000 laser particle size analyzer, the volumetric particle size distribution of the cathode material particles was obtained by utilizing the intensity distribution of laser diffraction. 50 This indicates the particle size corresponding to a cumulative particle size distribution percentage of 50%.

[0149] 13) Electrode rebound rate test and electrode peel strength test of positive electrode.

[0150] Production of positive electrode plates:

[0151] Weigh 0.8g of positive electrode material, 0.1g of conductive carbon black, and 0.1g of polyvinylidene fluoride and place them in a ball mill jar. Add 15mL of N-methylpyrrolidone and ball mill to form a uniform positive electrode slurry. Then, uniformly coat the positive electrode slurry onto aluminum foil and vacuum dry it at 80℃ for 12h to obtain the positive electrode sheet.

[0152] Electrode rebound rate test:

[0153] Weigh 0.8g of positive electrode material, 0.1g of conductive carbon black, and 0.1g of polyvinylidene fluoride and place them in a ball mill jar. Add 15mL of N-methylpyrrolidone and ball mill to form a uniform slurry. Then, uniformly coat the slurry onto aluminum foil and vacuum dry at 80℃ for 12 hours to obtain the positive electrode sheet. Cut the slurry into 50*200mm samples using a slitting machine and roll them to the specified electrode compaction density (3.4g / cm³). 3Using a micrometer, the thickness d1 of the electrode sheet was measured and recorded when it was pressed to the specified compaction point. Three measurement points were fixed. After that, the electrode sheet was left to stand at room temperature, and the thickness d1 of the electrode sheet at the three fixed points was measured and recorded at standing times of 1h, 2h, 24h, and 48h. t1 d t2 d t3 According to the formula, the electrode rebound rate = (d t1 / d t2 / d t3 Calculate using (-d1) / (d1-d0)*100%, where d t1 d t2 d t3 d1 is read directly during measurement, and d0 is the foil thickness, which is the average value.

[0154] Electrode peel strength test:

[0155] Weigh 0.8g of positive electrode material, 0.1g of conductive carbon black, and 0.1g of polyvinylidene fluoride and place them in a ball mill jar. Add 15mL of N-methylpyrrolidone and ball mill to form a uniform slurry. Then, coat the slurry evenly onto aluminum foil and vacuum dry at 80℃ for 12h to obtain the positive electrode sheet.

[0156] The peel strength of the prepared positive electrode sheet was measured by a tensile testing instrument. Specifically, the single-sided electrode sheet was cut into strips of 25mm*200mm. The test side was bonded to a steel plate with double-sided tape (30mm wide). The electrode sheet was parallel to the steel plate and rolled back and forth 3 times with an automatic roller press. The steel plate with the electrode sheet attached was inserted into the lower clamp of the SHIMADZU peel testing machine and fixed vertically. The electrode sheet current collector was inserted into the upper clamp and fixed so that the electrode sheet attached to the adhesive tape was at 180° with the electrode sheet fixed in the upper clamp. After the test sample was fixed, the test was started at a peel rate of 100mm / min. 3-5 samples were recorded for each material and the average value was taken.

[0157] 14) Button performance test:

[0158] The dried positive electrode sheet was cut into 15mm diameter circles. In a glove box, the positive electrode shell, electrode sheet, electrolyte (EC / DMC / EMC volume ratio 1:1:1, LiPF6 concentration 1mol / L), separator (Celgard PP / PE / PP three-layer composite film), lithium sheet, electrolyte, nickel foam, and negative electrode shell were assembled and sealed to obtain a CR2016 coin cell. The cells were then left to stand for 24 hours. The resulting cells were then tested in a constant temperature chamber.

[0159] The button cell was activated by charging and discharging at a current density of 0.1C at 25°C within a charge-discharge range of 3.0 to 4.3V. After activation, the cell was placed on a battery cycle testing system for charge-discharge testing.

[0160] Specifically, the CT2001A battery testing system was used for testing. Charge and discharge tests were conducted at 0.1C / 0.1C, 0.5C / 1C, and 0.5C / 2C rates within the 3.0V-4.3V discharge range at 25℃. The reference capacity was set to 200mA / g, and the 0.1C discharge specific capacity, 1C discharge specific capacity, and 2C discharge specific capacity were obtained.

[0161] The cycle capacity retention rate was measured by conducting 50 cycles at 0.5C / 1C rates within the 3.0V-4.3V discharge range and at 45℃.

[0162] Example 1

[0163] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0164] (2) The mixture is loaded into a sagger and transferred to a box furnace for primary sintering. First, it is calcined at 750°C for 4 hours in an oxygen atmosphere, and then the temperature is reduced to 550°C for 6 hours to obtain the primary sintering product. The primary sintering product is sieved and stored in a PE bag and sealed with aluminum-plastic film.

[0165] (3) Add the first sintering product to 50 mL of water and stir for 3 h to form suspension A. In addition, control the mass ratio of the first sintering product to Al2O3 to be 1:0.01. Add an appropriate amount of Al2O3 to 50 mL of water and stir for 3 h to form suspension B. Add suspension B to suspension A and stir at room temperature for 5 h to form mixed solution C. Then heat and stir at 80°C for 5 h to evaporate the solvent. Heat at 100°C for 24 h in a vacuum drying oven to obtain the composite material. Store it in a PE bag and seal it with aluminum-plastic film.

[0166] (4) The composite material is placed in an oxygen-filled atmosphere for secondary sintering. The secondary sintering temperature is controlled at 600℃ to obtain the secondary sintered product.

[0167] (5) Add the secondary sintering product to 50 mL of water and stir for 3 h to form suspension D. In addition, control the mass ratio of the secondary sintering product to H3BO3 to be 1:0.07. Add an appropriate amount of H3BO3 to 50 mL of water and stir for 3 h to form suspension E. Add suspension E to suspension D and stir at room temperature for 5 h to form mixture F. Then heat and stir at 80 °C for 5 h to evaporate the solvent. Heat at 100 °C for 24 h in a vacuum drying oven to obtain the composite. Store it in a PE bag and seal it with aluminum-plastic film.

[0168] (6) The composite is placed in an oxygen-filled atmosphere for three sinterings, with the temperature of the three sinterings controlled at 500℃, to obtain the cathode material.

[0169] The cathode material prepared in this embodiment includes secondary particles, the surface of which has a coating layer. The physicochemical parameters of the cathode material are detailed in Table 1.

[0170] Example 2

[0171] The difference from Example 1 is:

[0172] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 820:1. ZrO2 is then added and pulverized to obtain a mixture.

[0173] Example 3

[0174] The difference from Example 1 is:

[0175] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 70:1. ZrO2 is then added and pulverized to obtain a mixture.

[0176] Example 4

[0177] The difference from Example 1 is:

[0178] (3) Add the first sintering product to 50 mL of water and stir for 3 h to form suspension A. In addition, control the mass ratio of the first sintering product to WO3 to be 1:0.01. Add an appropriate amount of WO3 to 50 mL of water and stir for 3 h to form suspension B. Add suspension B to suspension A and stir at room temperature for 5 h to form mixture C. Then heat and stir at 80°C for 5 h to evaporate the solvent. Heat at 100°C for 24 h in a vacuum drying oven to obtain the composite material. Store it in a PE bag and seal it with aluminum-plastic film.

[0179] Example 5

[0180] The difference from Example 1 is:

[0181] (3) Add the first sintering product to 50 mL of water and stir for 3 h to form suspension A. In addition, control the mass ratio of the first sintering product to Al2O3 to be 1:0.02. Add an appropriate amount of Al2O3 to 50 mL of water and stir for 3 h to form suspension B. Add suspension B to suspension A and stir at room temperature for 5 h to form mixed solution C. Then heat and stir at 80°C for 5 h to evaporate the solvent. Heat at 100°C for 24 h in a vacuum drying oven to obtain the composite material. Store it in a PE bag and seal it with aluminum-plastic film.

[0182] Example 6

[0183] The difference from Example 1 is:

[0184] (3) Add the first sintering product to 50 mL of water and stir for 3 h to form suspension A. In addition, control the mass ratio of the first sintering product to Al2O3 to 1:0.005. Add an appropriate amount of Al2O3 to 50 mL of water and stir for 3 h to form suspension B. Add suspension B to suspension A and stir at room temperature for 5 h to form mixed solution C. Then heat and stir at 80°C for 5 h to evaporate the solvent. Heat at 100°C for 24 h in a vacuum drying oven to obtain the composite material. Store it in a PE bag and seal it with aluminum-plastic film.

[0185] Example 7

[0186] The difference from Example 1 is:

[0187] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to Y2O3 is controlled at 210:1. ZrO2 is added and the mixture is pulverized and ground to obtain a mixture.

[0188] Example 8

[0189] The difference from Example 1 is:

[0190] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0191] Example 9

[0192] The difference from Example 1 is:

[0193] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.8Co 0.1 Mn 0.1 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0194] Example 10

[0195] The difference from Example 1 is:

[0196] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.08:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0197] Example 11

[0198] The difference from Example 1 is:

[0199] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.00:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0200] Example 12

[0201] The difference from Example 1 is:

[0202] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Al 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0203] Example 13

[0204] The difference from Example 1 is:

[0205] (2) The mixture is loaded into a sagger and transferred to a box furnace for primary sintering. First, it is calcined at 650°C for 4 hours in an oxygen atmosphere, and then the temperature is reduced to 550°C for 6 hours to obtain the primary sintering product. The primary sintering product is sieved and stored in a PE bag and sealed with aluminum-plastic film.

[0206] Example 14

[0207] The difference from Example 1 is:

[0208] (2) The mixture is loaded into a sagger and transferred to a box furnace for primary sintering. First, it is calcined at 750°C for 1 hour in an oxygen atmosphere, and then the temperature is reduced to 550°C for 6 hours to obtain the primary sintering product. The primary sintering product is sieved and stored in a PE bag and sealed with aluminum-plastic film.

[0209] Comparative Example 1

[0210] (1) Reacting LiOH with the nickel-cobalt-manganese precursor Ni 0.89 Co 0.04 Mn 0.07 (OH)2 is mixed in a molar ratio of 1.04:1, and the mass ratio of nickel cobalt manganese precursor to ZrO2 is controlled at 210:1. ZrO2 is then added and pulverized to obtain a mixture.

[0211] (2) The mixture was loaded into a crucible and transferred to a box furnace for primary sintering. It was first calcined at 600°C for 8 hours in an oxygen atmosphere to obtain the primary sintering product. The primary sintering product was sieved and stored in a PE bag and sealed with aluminum-plastic film to obtain the positive electrode material. Comparative Example 1 was not coated.

[0212] Comparative Example 2

[0213] Unlike Comparative Example 1:

[0214] (2) The mixture is loaded into a sagger and transferred to a box furnace for primary sintering. First, it is calcined at 980°C for 4 hours in an oxygen atmosphere, and then the temperature is reduced to 550°C for 6 hours to obtain the primary sintering product. The primary sintering product is sieved and stored in a PE bag and sealed with aluminum-plastic film.

[0215] The cathode materials prepared in the examples and comparative examples were tested, and the test results are shown in Tables 1 and 2:

[0216] Table 1. Physicochemical parameters of the cathode materials in the examples and comparative examples (I)

[0217] Table 2 Physicochemical parameters of the cathode materials in the examples and comparative examples (II)

[0218] The cathode materials prepared in the examples and comparative examples were subjected to physicochemical and electrochemical tests, and the test results are shown in Table 3 below.

[0219] Table 3. Comparison of the physicochemical properties of the cathode materials in the examples and the comparative examples, and the performance of the batteries prepared from them.

[0220] Referring to Tables 1 to 3, based on the test data from Examples 1 to 12, it can be seen that by controlling the powder plasticity ratio of the cathode material in this application to be within the range of 70% to 91%, the cathode material can possess both high compaction density and high structural stability. The two complement each other, jointly enabling the cathode material to be used under high compaction density, thereby improving battery capacity, first coulombic efficiency, and cycle performance.

[0221] Based on the test data from Examples 1 and 13, it is evident that the proportion of mesopores in the cathode material decreases while the proportion of macropores increases, resulting in a smaller pore ratio B. This leads to a decrease in the average crushing force of the cathode material and a reduction in the electrode rebound rate. This indicates that during cycling, there is insufficient mesopore content to disperse and alleviate expansion stress, resulting in decreased cycle performance. Furthermore, the increased proportion of macropores exacerbates side reactions between the cathode material and the electrolyte, and the initial coulombic efficiency of the cathode material is slightly lower compared to Example 1.

[0222] According to the test data of Examples 1 and 14, the ratio of compaction density to tap density of the cathode material is lower than that of Example 1, the ratio B of mesopores to macropores is also lower than that of Example 1, the average crushing force of the cathode material is too low, the phenomenon of particle breakage of secondary particles during electrode preparation is increased, the structural stability of particles is reduced, the electrode peeling strength is reduced, and the capacity, first efficiency and cycle performance of the cathode material are also lower than those of Example 1.

[0223] According to the test data of Comparative Example 1 and Example 1, the powder plasticity ratio of the positive electrode material in Comparative Example 1 is too large, the proportion of large pores in the positive electrode material particles increases, the particle structure strength decreases, the positive electrode material particles are difficult to adapt to the extrusion stress between particles, which makes the particles prone to breakage under high pressure density, resulting in repeated formation of solid electrolyte film on the particle surface, accelerated capacity decay of the positive electrode sheet, and a significant decrease in electrode sheet peel strength.

[0224] Figure 2a is a test data graph of the powder plasticity ratio of the cathode material provided in Example 1 of this application, and Figure 2b is a test data graph of the powder plasticity ratio of the cathode material provided in Comparative Example 2 of this application. As shown in Figures 2a and 2b, it can be seen from the test data of Comparative Example 2 and Example 1 that the powder plasticity ratio of the cathode material in Comparative Example 2 is too low, the ratio of mesopores to macropores is too high, which leads to a larger electrode rebound rate, a significant decrease in electrode peel strength, an increase in battery internal resistance, a further decrease in the battery's initial efficiency compared to Example 1, and an accelerated capacity decay of the cathode.

[0225] Figure 3a is an electron microscope image of the cathode material provided in Example 1 of this application, and Figure 3b is an electron microscope image of the cathode material provided in Example 5 of this application. As shown in Figures 3a and 3b, the primary particles that make up the secondary particles in Example 1 have smooth and rounded surfaces, while the primary particles that make up the secondary particles in Example 5 have rougher surfaces. Excessive surface coating leads to agglomeration of the surface coatings, resulting in a slight increase in the specific surface area of ​​the cathode material and a slight decrease in the capacity and first-time efficiency of the material.

[0226] Figure 4a is the average crushing force curve of the cathode material provided in Example 1 of this application, and Figure 4b is the average crushing force curve of the cathode material provided in Comparative Example 2 of this application. As shown in Figures 4a and 4b, the first stage sintering temperature of the primary sintering process in Comparative Example 2 is too high, resulting in harder particles and increased crushing force of secondary particles, but the toughness of secondary particles weakens. Figure 5a is a comparison diagram of the cathode material powder before and after compression provided in Example 1 of this application, and Figure 5b is a comparison diagram of the cathode material powder before and after compression provided in Comparative Example 2 of this application. As shown in Figures 5a and 5b, the cathode material particles of Comparative Example 2 are broken into multiple dispersed small particles after compression, while the powder plasticity ratio of the cathode material of Example 1 is within a suitable range, and the secondary particles have both high strength and toughness. The secondary particles can still maintain a large block shape after compression, which can reduce the rebound rate of the cathode sheet, increase the energy density of the battery, reduce the resistance of the battery, and also effectively reduce the risk of particle breakage and fragmentation during the rolling process or battery cycling process, improve the structural stability and cycle stability of the cathode material, and thus improve the overall performance of the battery.

[0227] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a nickel-cobalt-lithium composite oxide, and the cathode material includes secondary particles; The powder plasticity ratio of the positive electrode material is β, where 70% ≤ β < 91%; The powder plasticity ratio β of the positive electrode material was measured according to the following test method: 1g of cathode material was subjected to pressure using a UTM7305 automatic compaction density meter. The initial powder height of the cathode material under the applied pressure was H0. The pressure was gradually increased and then gradually decreased, and each pressure was held for 5 seconds. The powder height under each pressure was H0. n ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 30) is the deformation variable δ. n ; with δ n The x-axis represents the powder height, H. n The pressure it withstands is input into the Origin software as the vertical axis to obtain the compression-spring stress-strain curve. The compression-spring stress-strain curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material, β=A / (A+B)*100%.

2. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The powder plasticity ratio β of the positive electrode material is 70%, 72%, 75%, 78%, 80%, 82%, 85%, 88%, 89%, 90%, or within any two of the above values; (2)70％≤β＜80％； (3)80％≤β≤90％。 3. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The average crushing force of the positive electrode material is 5mN to 20mN; (2) The average crushing force of the positive electrode material is 5mN, 7mN, 8mN, 10mN, 12mN, 15mN, 17mN, 18mN, 20mN or within any two of the above values; (3) The average crushing force of the positive electrode material is 9mN to 15mN.

4. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The plastic strain energy of the positive electrode material is A, 4.5J≤A≤12J; (2) The elastic strain energy of the positive electrode material is B, 0.6J≤B≤2.1J.

5. The positive electrode material according to claim 1, characterized in that, The secondary particles of the cathode material have pores, including mesopores and macropores, and the cathode material satisfies at least one of the following characteristics: (1) The volume ratio of the mesopore to the macropore is L, where L is (3~25):1; (2) The mesopores account for 55% to 95% of the total volume of all pores.

6. The cathode material according to claim 1, characterized in that, The secondary particles of the cathode material have pores, including mesopores and macropores, and the cathode material satisfies at least one of the following characteristics: (1) The volume ratio of the macropores in all pores is 3% to 35%; (2) The most probable pore size of the cathode material is 1 nm to 6 nm and / or 10 nm to 25 nm.

7. The cathode material according to claim 1, characterized in that, In the XRD diffraction pattern of the cathode material, the cathode material satisfies at least one of the following characteristics: (1) The full width at half maximum (FWHM) of the diffraction peaks of the (003) crystal plane of the cathode material is 0.13 to 0.20; (2) The full width at half maximum (FWHM) of the diffraction peaks of the (104) crystal plane of the cathode material is 0.20 to 0.28; (3) The peak intensity of the diffraction peak of the (003) crystal plane of the cathode material is I. (003) The peak intensity of the diffraction peak of the (104) crystal plane of the cathode material is I. (104) The positive electrode material satisfies: 1.5 ≤ I (003) / I (104) ≤2.

0.

8. The positive electrode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The secondary particles of the cathode material have a coating layer on their surface, and the coating layer includes an element N, which is selected from at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, and Sb. (2) The secondary particles of the cathode material have a coating layer on their surface, and the thickness of the coating layer is 3nm to 20nm. (3) The general chemical formula of the positive electrode material is Li a Ni x Co y M z N b O2, wherein 0.95≤a≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, x+y+z+b=1, M includes Mn and / or Al, and N includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, Nb, Ba, Ta, and V; (4) The general chemical formula of the positive electrode material is Li a Ni x Co y M z N b O2, wherein 0.95≤a≤1.1, 0.6≤x<1, 0<y<0.4, 0<z<0.4, 0≤b<0.1, x+y+z+b=1, M includes Mn and / or Al, and N includes at least one of Y, W, Sr, Zr, La, Co, Ti, Mg, Al, B, Sb, Nb, Ba, Ta, and V.

9. The positive electrode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The scraping angle of the positive electrode material particles is 10° to 80°; (2) The specific surface area of ​​the positive electrode material is 0.4 m². 2 / g~1.5m 2 / g.

10. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The surface free lithium content of the cathode material is 500ppm to 2300ppm; (2) The pH value of the positive electrode material is 11.5 to 12.

0.

11. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The tap density of the positive electrode material is 2.0 g / cm³. 3 ~3.1g / cm 3 ; (2) The compaction density of the positive electrode material is 2.7 g / cm³. 3 ~3.6g / cm 3 .

12. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The ratio of the compaction density to the tapped density of the positive electrode material is 1.15 to 1.5; (2) The median particle size D50 of the volume distribution of the positive electrode material is 6μm to 12μm.

13. The cathode material according to claim 1, characterized in that, The positive electrode material, conductive carbon black, and polyvinylidene fluoride are mixed in a mass ratio of 8:1:1 to form a positive electrode sheet, wherein the positive electrode sheet satisfies the following conditions: (1) The positive electrode has a rebound rate of 3.0% to 20.0%; (2) The electrode peel strength of the positive electrode is 50mN / mm to 500mN / mm.

14. The cathode material according to claim 1, characterized in that, The test method for the powder plasticity ratio β of the cathode material is as follows: 1g of cathode material is subjected to pressure using a UTM7305 automatic compaction density meter. The pressures are sequentially 100N, 1000N, 5000N, 10000N, 15000N, 20000N, 25000N, 20000N, 15000N, 10000N, 5000N, 100N, and 100N. Each pressure is held for 5 seconds, and the height of the cathode material powder is recorded at each pressure. The powder height at the first 100N pressure is H0, the powder height at 1000N pressure is H1, and so on, with the final powder height at 100N pressure being H... 12 ; Calculate H0 and H based on H0 n The difference between (n, a natural number between 1 and 12) is the shape variable δ. n ; with δ n The x-axis represents the powder height, H. n The pressure exerted during the compression-rebound stress-strain curve is used as the ordinate. This curve is then input into Origin software to obtain the compression-rebound stress-strain curve. The curve is then integrated to obtain the plastic strain energy A and elastic strain energy B of the cathode material. In the compression-rebound stress-strain curve, the compression segment represents the stage where the pressure gradually increases, corresponding to pressures of 100N, 1000N, 5000N, 10000N, 15000N, 20000N, and 25000N. The rebound segment represents the stage where the pressure gradually decreases, corresponding to pressures of 25000N, 20000N, 15000N, 10000N, 5000N, 1000N, and 100N. The plastic strain energy A is the integrated area between curves P1 and P2, and the elastic strain energy is the integrated area of ​​curve P2.

15. A positive electrode plate, characterized in that, The positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 14, wherein the electrode rebound rate of the positive electrode sheet is 3.0% to 20.0%; and / or, the electrode peel strength of the positive electrode sheet is 50mN / mm to 500mN / mm.

16. A battery, characterized in that, The battery comprises the positive electrode material of any one of claims 1 to 14 or the positive electrode sheet of claim 15.

Images