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; the mass content of free nitrates of the positive electrode material is Q ppm, where 10≤Q≤100; and in the positive electrode material, the number ratio of particles having a particle size of less than 1 μm is R%, where 8≤R≤16. The positive electrode material of the present application can effectively improve the specific capacity and achieve high initial efficiency performance of the positive electrode material, and can also improve the structural stability and the cycle performance thereof.

Description

Positive electrode materials, positive electrode sheets and batteries

[0001] This application claims priority to Chinese patent application 202411976483.9, filed on December 26, 2024. The entire contents of the aforementioned Chinese patent application 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] Lithium-ion batteries are widely used in laptops, mobile phones, and digital products due to their high energy density, good safety performance, long cycle life, and environmental friendliness. However, the development of cathode materials has been slower compared to the development of high-capacity anode materials (approximately 800–1000 mAh / g). Therefore, current researchers are focusing their efforts on developing high-capacity and high-voltage cathode materials to improve the energy density of lithium-ion batteries.

[0004] As the nickel content in the cathode material increases, problems such as lithium-nickel mixing, structural degradation, reduced thermal stability, and increased residual alkali inevitably arise, leading to battery capacity degradation, reduced cycle life, and poor structural stability, thus affecting its safety and high-performance use. Furthermore, at high voltages, excessive lithium-ion extraction from the cathode material causes cation mixing, resulting in the extraction of lattice oxygen. This not only generates gas in the battery but also significantly reduces the capacity and cycle performance of the cathode material. Additionally, at high potentials, the side reactions between the cathode material and the electrolyte intensify, producing carbon dioxide gas, which alters the surface crystal structure of the cathode material, causing the loss of lithium storage sites.

[0005] Therefore, improving the high-voltage resistance of cathode materials and reducing crystal structure distortion are among the urgent problems to be solved. Summary of the Invention

[0006] This application provides a cathode material and a cathode cell. The cathode material of this application has excellent high voltage resistance and can reduce crystal structure distortion of the cathode material, thereby improving the structural stability and cycle performance of the cathode material.

[0007] In a first aspect, this application provides a cathode material, wherein the free nitrate content of the cathode material is Q ppm, 10≤Q≤100; in the scanning electron microscope image of the cathode material, the percentage of particles with a diameter less than 1μm is R%, 8≤R≤16; wherein the cathode material is dispersed in pure water, and after ultrasonic filtration, the free nitrate content Q ppm of the cathode material is obtained by characterizing the filtrate using an ion chromatography instrument.

[0008] Secondly, this application provides a positive electrode sheet, the positive electrode sheet comprising the positive electrode material as described in the first aspect.

[0009] Thirdly, this application provides a battery, wherein the positive electrode sheet is as described in the second aspect or the positive electrode material is as described in the first aspect.

[0010] Compared with the prior art, this application has the following advantages:

[0011] This application controls the free nitrate content of the cathode material to be between 10 ppm and 100 ppm, while controlling the proportion of particles smaller than 1 μm in the cathode material to be between 8% and 16%. An appropriate amount of small particles can improve the packing density between cathode material particles without causing excessive side reactions, thus improving lithium-ion transport, reducing the internal resistance of the cathode material, lowering the lithium-ion transport barrier, and improving the lithium insertion / extraction efficiency of the cathode material. Under the synergistic effect of an appropriate amount of free nitrate and particles smaller than 1 μm, the high-voltage resistance and high capacity of the cathode material can be improved, while simultaneously enhancing the lithium-ion transport efficiency and cycle stability of the cathode material. Attached Figure Description

[0012] 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.

[0013] Figure 1 is a schematic diagram of the discharge state of the battery provided in the embodiment of this application.

[0014] Figure 2 shows the Li element spectrum obtained by XPS characterization of the cathode material prepared in Example 1 of this application after the first charge and discharge.

[0015] Figure 3 shows the Li element spectrum obtained by XPS characterization of the cathode material prepared in Comparative Example 1 of this application after the first charge and discharge. Detailed Implementation

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] This application provides a cathode material, wherein the free nitrate content of the cathode material is Q ppm, 10≤Q≤100; in the scanning electron microscope image of the cathode material, the proportion of particles with a diameter less than 1μm is R%, 8≤R≤16; wherein the cathode material is dispersed in pure water, and after ultrasonic filtration, the free nitrate content Qppm of the cathode material is obtained by characterizing the filtrate with an ion chromatograph.

[0021] The free nitrate content of the cathode material provided in this application is Q ppm, 10≤Q≤100. The free nitrate content Q in the cathode material meets the above range, and the cathode material has good structural stability and cycle performance. The applicant speculates that this is because the free nitrate in the cathode material can react with active lithium ions during charge-discharge cycles, thereby inducing the formation of Li2O on the surface of the cathode material. Li2O has high voltage resistance, which helps to improve the high voltage resistance of the cathode material, reduce the occurrence of side reactions between the cathode material and the electrolyte, and the distribution of Li2O on the surface of the cathode material can reduce the surface defects of the cathode material, reduce the surface energy of the cathode material, help improve the crystal structure stability of the cathode material, reduce oxygen escape from the crystal lattice, and thus reduce the crystal structure distortion of the cathode material.

[0022] However, because Li2O on the surface of the cathode material affects ion transport, the lithium insertion / extraction kinetics of the cathode material decrease. Therefore, this application controls the mass content of free nitrate in the cathode material to be between 10 ppm and 100 ppm, while controlling the proportion of particles with a diameter less than 1 μm in the cathode material to be between 8% and 16%. An appropriate amount of small particles can improve the stacking density between cathode material particles without causing excessive side reactions, thereby improving lithium-ion transport, reducing the internal resistance of the cathode material, lowering the lithium-ion transport barrier, and improving the lithium insertion / extraction efficiency of the cathode material. Under the synergistic effect of an appropriate amount of free nitrate and particles with a diameter less than 1 μm, the high voltage resistance and high capacity of the cathode material can be improved, while the lithium-ion transport efficiency and cycle stability of the cathode material can be improved.

[0023] In some embodiments, the free nitrate content of the positive electrode material can be specifically 10 ppm, 12 ppm, 25 ppm, 30 ppm, 50 ppm, 68 ppm, 75 ppm, 80 ppm, 85 ppm, 95 ppm, or 100 ppm, or other values ​​within the above range, which are not limited here. If the free nitrate content of the positive electrode material is too high, excessive Li2O will form on the surface of the positive electrode material, hindering ion transport. When the free nitrate content of the positive electrode material is too low, insufficient Li2O will form on the surface of the positive electrode material during charging and discharging, exacerbating side reactions between the positive electrode material and the electrolyte, especially under high-voltage charging and discharging conditions, leading to increased capacity loss of the positive electrode material. This application controls the mass content of free nitrate ions in the cathode material within the above-mentioned range. After cyclic charging and discharging, an appropriate amount of Li2O can be induced to form on the surface of the cathode material particles. The appropriate amount of Li2O can reduce the surface defects of the cathode material, reduce the surface energy of the cathode material, help improve the crystal structure stability of the cathode material, and make the cathode material have both high voltage resistance and excellent cycle stability.

[0024] It should be noted that in the coin cell formed by the cathode material, during the first charge and discharge process, free nitrate ions in the cathode material can react via the following reaction: 2Li + +NO3 - +2e - =Li₂O + NO 2- A certain amount of Li2O protective layer is induced to form on the surface of the positive electrode material. This protective layer has high chemical stability, can remain inert under high voltage, effectively isolate the electrolyte, and reduce the occurrence of side reactions.

[0025] In some embodiments, the proportion of particles with a diameter less than 1 μm in the cathode material is 8% to 16%, specifically 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or 16%, etc., and other values ​​within the above range are also possible and are not limited here. When the proportion of particles with a diameter less than 1 μm is too high, it means that the number of micro-powders increases, the particle size distribution width of the cathode material increases, and the compaction density of the cathode material can be improved. However, the specific surface area of ​​the cathode material increases, and the smaller the particle size, the more serious the side reactions with the electrolyte. In addition, these micro-powders can easily lead to the complexity of lithium-ion transport paths during charge-discharge cycles, affecting lithium-ion insertion and extraction, thus reducing the structural stability and cycle stability of the cathode material. When the proportion of particles with a diameter less than 1 μm is too low, the lithium-ion transport path lengthens, the initial DCR of the cathode material increases, and the compaction density of the cathode material decreases. This application controls the proportion of particles with a diameter of less than 1 μm within the above-mentioned range, which can shorten the lithium-ion diffusion path, reduce the transport barrier between cathode material particles, ensure that the compaction density of the cathode material is within a suitable range, improve the energy density of the cathode material, and at the same time help reduce the occurrence of side reactions between the cathode material and the electrolyte, reduce impedance, and improve the capacity and cycle stability of the cathode material.

[0026] In some embodiments, the general chemical formula of the cathode material is Li. n Ni x Co y N z M s O2, wherein 0.9≤n≤1.1, 0<x<1, 0<y<1, 0<z<1, 0≤s<1, x+y+z+s=1, N includes at least one of Mn and Al, and M includes at least one of Zr, Mg, W, Mo, Ti, Ba, Sr, Cr, Zn, Y, V, Cu, B, and Nb.

[0027] Specifically, the values ​​of n can be 0.90, 0.92, 0.95, 0.96, 0.98, 0.99, 1.0, 1.02, 1.05, 1.08, or 1.1, etc.; the values ​​of x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.92, etc.; and the values ​​of y can be 0.001, 0.06, 0.1, 0.2, 0.28, 0.3, 0.4, 0.5, or 0. The values ​​of z can be 0.001, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.92, etc., and the values ​​of s can be 0, 0.001, 0.005, 0.008, 0.01, 0.02, 0.05, 0.08, 0.1, 0.2, 0.3, or 0.5, etc., or other values ​​within the above ranges, which are not limited here.

[0028] The cathode material is a nickel-cobalt-lithium composite oxide, which includes a nickel-cobalt-manganese-lithium composite oxide or a nickel-cobalt-aluminum-lithium composite oxide.

[0029] In some embodiments, the volumetric particle size distribution of the cathode material satisfies: 0.2μm≤D10≤2.0μm, 2.0μm≤D50≤5.0μm, and 6.0μm≤D90≤12.0μm. Specifically, D10 can be 0.2μm, 0.3μm, 0.5μm, 0.8μm, 1.0μm, 1.2μm, 1.4μm, 1.5μm, 1.8μm, or 2.0μm, etc.; D50 can be 2.0μm, 2.3μm, 2.5μm, 2.8μm, 3.0μm, 3.2μm, 3.5μm, 3.8μm, 4.0μm, 4.2μm, 4.5μm, or 5.0μm, etc.; and D90 can be 6.0μm, 6.5μm, 6.8μm, 7.0μm, 8.0μm, 9.2μm, 10.5μm, 11μm, 11.5μm, 11.8μm, or 12.0μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here. In this application, controlling the volume particle size distribution of the cathode material to meet the above conditions can improve the compaction density of the cathode material and enhance its cycle stability.

[0030] In some embodiments, the volumetric particle size distribution width of the cathode material satisfies: 0.8 ≤ (D90 - D10) / D50 ≤ 2.0, specifically 0.8, 0.9, 1.0, 1.09, 1.1, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.6, 1.7, 1.8, or 2.0, etc., and of course, other values ​​within the above range are also possible, without limitation. By controlling the particle size distribution width of the cathode material within the above range, this application can improve the compaction density of the cathode material and increase the energy density of the battery made from the cathode material.

[0031] In some embodiments, the free sulfate content of the cathode material is K ppm, where 10 ≤ K ≤ 800. Specifically, it can be 10 ppm, 50 ppm, 80 ppm, 100 ppm, 150 ppm, 200 ppm, 275 ppm, 400 ppm, 470 ppm, 560 ppm, 650 ppm, 780 ppm, or 800 ppm, or other values ​​within the above range, which are not limited here. In this application, controlling the free sulfate content within the above range can improve the lithium-ion migration rate, increase the capacity of the cathode material, and enhance the structural stability of the cathode material.

[0032] In some embodiments, the average particle size of the primary particles in the cathode material is 1 μm to 5 μm, specifically 1.0 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.4 μm, 2.8 μm, 3.0 μm, 3.5 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.5 μm, 4.8 μm, or 5.0 μm, etc., or other values ​​within the above range, which are not limited here. In this application, controlling the average particle size of the primary particles within the above range can reduce the impedance of the cathode material, improve the lithium-ion transport efficiency, and is beneficial to improving the capacity of the cathode material.

[0033] In some embodiments, the cathode material is a single-crystal material, comprising single-crystal particles, wherein the single-crystal particles are particles with the same orientation. It should be specifically noted that the term "single-crystal material" as known to those skilled in the art is not strictly "single-crystal." In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations imposed by impurities, strain, and crystal defects, ideal single crystals are very rare and difficult to produce in reality. Therefore, the single-crystal materials known in the art are actually more accurately described as "single-crystal-like" cathode materials, which differ only in size from polycrystalline particles composed of numerous small particles due to their large, single-crystal-like particle size.

[0034] In this application, a single grain can be a single particle composed of a primary particle. The aforementioned single-crystal cathode material may also contain a small number of "quasi-secondary particles" formed by the adhesion of several primary particles. "Primary particle" refers to the smallest particle unit identified when observing the cathode active material using a scanning electron microscope.

[0035] It is important to note that the difference between single-crystal cathode materials and polycrystalline cathode materials (i.e., polycrystalline secondary particles) lies in the fact that the smallest particles in polycrystalline secondary particles are formed by the aggregation of nanoscale particles. In contrast, the smallest particles in single-crystal cathode materials are typically micrometer-sized individual particles. Generally, in addition to EBSD testing, scanning electron microscopy (SEM) and other characterization methods can be used to determine whether the obtained cathode product is a single-crystal material. For example, for single-crystal cathode materials, SEM can characterize the morphology of single-crystal particles, showing that they are generally regular or irregular spherical in shape, with no significant particle aggregation. EBSD can also characterize the orientation of single-crystal cathode materials. EBSD can observe that at least one grain has the same color, indicating that at least one grain has the same orientation; grains with the same orientation are single crystals. It is important to specifically clarify that the "single-crystal cathode material" known to those skilled in the art is not a "single crystal" in the strict crystallographic sense. In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations such as impurities, strain, and crystal defects, ideal single crystals are very rare and difficult to produce in the laboratory. Therefore, the single-crystal cathode materials known in the art are actually more "single-crystal-like" cathode materials, which only differ from polycrystalline materials composed of numerous small primary particles in size, exhibiting a large particle size similar to single crystals.

[0036] In some embodiments, the positive electrode material is fabricated into a mold battery, and the mold battery is characterized by in-situ XRD. During the first charge-discharge cycle, the structural recovery degree δ of the positive electrode material satisfies: 100.00% ≥ δ ≥ 99.70%; where δ = θ1 / θ2 × 100%, θ1 is the diffraction angle of the positive electrode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the beginning of the first charge cycle, and θ2 is the diffraction angle of the positive electrode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the end of the first discharge cycle. Specifically, δ can be 99.7%, 99.8%, 99.85%, 99.9%, 99.95%, or 100.00%, etc., and of course, it can also be other values ​​within the above range, which are not limited here. Understandably, if the degree of structural recovery of the cathode material is controlled within the above range, it can be seen that the crystal structure of the cathode material can remain stable during charge-discharge cycles, the irreversible phase transition of the cathode material is reduced, and the lattice structure decay is greatly improved, which is conducive to maintaining the cycle structure stability of the cathode material.

[0037] In some embodiments, the specific surface area of ​​the positive electrode material is 0.5 m². 2 / g~1.5m 2 / g; specifically, it can be 0.5m 2 / g, 0.6m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g or 1.5m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. By controlling the specific surface area of ​​the cathode material within the above range, the cathode material can exhibit higher capacity, first coulombic efficiency, cycle stability, and lower gas production.

[0038] In some embodiments, the tap density of the positive electrode material is 1.0 g / cm³. 3 ~3.0g / cm 3 Specifically, it can be 1.0 g / cm³. 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 2.4g / cm 3 2.5g / cm 3 2.8g / cm 3 Or 3.0g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. Controlling the tap density of the cathode material within the above range is beneficial for improving the material's processing performance and increasing the battery's energy density.

[0039] In some embodiments, the compaction density of the positive electrode material is 2.5 g / cm³. 3 ~3.5g / cm 3 Specifically, it could be 2.5 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 32.9g / cm 3 3.0g / cm 3 3.1g / cm 3 3.2g / cm 3 3.4g / cm 3 Or 3.5g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. Controlling the compaction density of the cathode material within the above range is beneficial to improving the energy density of the battery.

[0040] In some embodiments, the loose packing density of the positive electrode material is 0.5 g / cm³. 3 ~1.5g / cm 3 Specifically, it can be 0.5 g / cm³ 3 0.6g / cm 3 0.7g / cm 3 0.8g / cm 3 0.9g / cm 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm 3 1.4g / cm 3 Or 1.5g / cm 3 Of course, other values ​​within the above range are also possible and are not limited here. Controlling the loose packing density of the cathode material within the above range is beneficial to improving the energy density of the battery.

[0041] In some embodiments, after the cathode material is fabricated into a coin cell and charged and discharged for one week, the cathode material is characterized by XPS. The XPS spectrum of the cathode material shows that it contains a Li₂O phase. Therefore, the presence of a Li₂O phase in the cycled cathode material, as determined by XPS, indicates that free nitrate ions present in the cathode material can react with active lithium ions to induce the formation of Li₂O on the cathode material surface. In some embodiments, the XPS spectrum of the cathode material shows characteristic peaks between 53.5 eV and 55 eV.

[0042] It should be noted that the above-mentioned method for preparing coin cells is as follows:

[0043] Ingredients: NCM:SP:5% PVDF adhesive solution = 93:5:2 = 9.3g:0.5g:4.0g, NMP = 9g, disperse evenly by high-speed stirring.

[0044] Coating and drying: The slurry is evenly coated on a 20μm thick aluminum foil using a 210µm coater. The coating length is set to the maximum length of the coater. The latter half of the electrode is cut off and placed in a 100℃ forced-air drying oven to dry for more than 1.5 hours.

[0045] Rolling, punching and drying: During rolling, adjust the roller mill to 1 roll gap and roll 3 times; punch holes using a 14mm punching machine, weigh, and then place in a vacuum drying oven to vacuum dry at 85℃ for more than 8 hours.

[0046] Button cell (LIR2016) assembly: Positive electrode shell - 2 drops of electrolyte - Positive electrode sheet (14mm) - 3 drops of electrolyte - 20μm separator - 2 drops of electrolyte - Lithium foil - 150μm nickel foam - negative electrode shell (dried at 50℃), the battery is assembled and sealed, then removed from the glove box for testing. After standing for 12 hours, the coin cell is charged at 0.1C and then discharged once.

[0047] XPS characterization of the cathode material after cycling: The cathode sheet in the coin cell after one cycle of charging and discharging at 0.1C was removed, and the powder on the surface of the cathode sheet was scraped off with a scraper. The scraped-off powder was characterized using an XPS spectrometer to obtain the XPS spectrum.

[0048] Secondly, this application provides a method for preparing a cathode material, comprising the following steps:

[0049] S10, the hydroxide precursor of the positive electrode material is subjected to nitration annealing to obtain an oxide precursor containing nitrate ions;

[0050] S20, a mixture of an oxide precursor containing nitrate ions and a lithium source is subjected to a first sintering treatment, and the first sintering product is crushed to obtain a cathode material, wherein the mass content of free nitrate in the cathode material is Q ppm, 10≤Q≤100; the proportion of particles with a particle size of less than 1μm in the cathode material is R%, 8≤R≤16.

[0051] The method for preparing the cathode material provided in this application involves subjecting a hydroxide precursor to nitration annealing to obtain an oxide precursor containing nitrate ions. Nitration annealing refers to annealing in a nitric acid atmosphere for a certain time, resulting in an oxide precursor containing an appropriate amount of nitrate ions. A mixture of the oxide precursor containing nitrate ions and a lithium source is then subjected to a single sintering process. The reactivity of the oxide precursor during this single sintering process is lower than that of the hydroxide precursor, which is beneficial for uniform particle growth, increasing the particle size, and reducing the proportion of particles smaller than 1 μm. The cathode material prepared in this application has a free nitrate content between 10 ppm and 100 ppm, while controlling the proportion of particles smaller than 1 μm to between 8% and 16%. An appropriate amount of small particles can improve the packing density between cathode material particles without causing excessive side reactions, thus improving lithium-ion transport, reducing the internal resistance of the cathode material, lowering the lithium-ion transport barrier, and increasing the lithium insertion / extraction efficiency of the cathode material. The synergistic effect of appropriate amounts of free nitrate and particles with a diameter of less than 1 μm can improve the high voltage resistance and high capacity of the cathode material, while also enhancing the lithium-ion transport efficiency and cycle stability of the cathode material.

[0052] The preparation method of this application is described in detail below with reference to the embodiments:

[0053] Before step S10, the above method further includes:

[0054] S01, prepare a salt solution of nickel, manganese, and nitrogen in a certain stoichiometric ratio to form a mixed solution, adjust the pH of the mixed solution, and obtain the hydroxide precursor of the cathode material by co-precipitation. The nitrogen element can be Mn and / or Al.

[0055] In some embodiments, the stoichiometric ratios of nickel, cobalt, and nitrogen meet the following conditions: 0.5 ≤ Ni < 1, 0 < Co ≤ 0.2, 0 < N ≤ 0.4; the molar ratio of Ni:Co:N can specifically be 0.60:0.10:0.30, 0.67:0.05:0.28, or 0.90:0.5:0.05, etc. The nitrogen element can be Mn and / or Al.

[0056] In some embodiments, the salt solution is a sulfate, and compared with the conventional coprecipitation method, this application uses a sulfate system to prepare hydroxide precursors.

[0057] In some embodiments, the pH value of the mixed solution is 7 to 14, specifically 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13 or 14, etc., or other values ​​within the above range, which are not limited here.

[0058] In some embodiments, the modifier used in the coprecipitation method can be ammonia, citric acid, ethylene glycol, etc., which helps the hydroxide in the mixed solution to precipitate and separate from the mixed solution.

[0059] In other embodiments, before step S10, spray pyrolysis can be used to react the salt in the mixed solution to form an oxide precursor.

[0060] In other embodiments, commercially available hydroxide precursors may also be used.

[0061] S10, the hydroxide precursor of the positive electrode material is subjected to nitration annealing to obtain an oxide precursor containing nitrate ions.

[0062] In some embodiments, the nitrification annealing treatment is performed by holding the annealing process at a temperature for a certain period of time in a mixed atmosphere containing nitric acid.

[0063] In some embodiments, the volume concentration of nitric acid in the mixed atmosphere is 1% to 3%; specifically, it can be 1%, 1.5%, 2%, 2.5%, 2.8% or 3.0%, etc., or other values ​​within the above range, which are not limited here.

[0064] In some embodiments, the mass content of oxygen in the mixed atmosphere is <1.0 ppm. Too much oxygen will cause the oxide precursor grains to grow too quickly, which is not conducive to maintaining the uniformity of the precursor particles and will reduce the reactivity of the oxide precursor.

[0065] In some embodiments, the mixed atmosphere includes nitric acid vapor and water vapor.

[0066] In some embodiments, the temperature of the nitration annealing treatment is 200℃ to 800℃, specifically 200℃, 250℃, 300℃, 350℃, 480℃, 550℃, 600℃, 630℃, 650℃, 680℃, 700℃, 750℃, 780℃ or 800℃, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0067] In some embodiments, the heating rate of the nitration annealing treatment is 0.5℃ / min to 3℃ / min, specifically 0.5℃ / min, 0.8℃ / min, 1.0℃ / min, 1.5℃ / min, 1.8℃ / min, 2.0℃ / min, 2.5℃ / min or 3.0℃ / min, etc., or other values ​​within the above range, which are not limited here.

[0068] In some embodiments, the holding time for the nitration annealing treatment is 3h to 10h, specifically 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0069] In some embodiments, the ambient pressure during the nitrification annealing treatment is lower than the pressure of the mixed atmosphere.

[0070] In some embodiments, the ambient pressure during the nitration annealing treatment is 2.0 kPa to 4.0 kPa, specifically 2.0 kPa, 2.2 kPa, 2.5 kPa, 2.8 kPa, 3.0 kPa, 3.2 kPa, 3.5 kPa or 4.0 kPa, etc., or other values ​​within the above range, which are not limited here.

[0071] In this application, by controlling process parameters such as ambient pressure, holding time, and annealing temperature during the nitration annealing process, it is beneficial to form an appropriate amount of nitrate ions on the surface of the oxide precursor.

[0072] In some embodiments, the general chemical formula of the oxide precursor of the cathode material is Ni. a Co b N c M e O, where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 ≤ e < 1, and a + b + c + e = 1, N includes at least one of Mn and Al, and M includes at least one of Zr, Mg, W, Mo, Ti, Ba, Sr, Cr, Zn, Y, V, Cu, B, and Nb.

[0073] Oxide precursors containing nitrate ions have lower reactivity than hydroxide precursors. During the sintering process of oxide precursors and lithium salts, the diffusion resistance of lithium salts is slightly higher, which is beneficial to generating a suitable amount of small primary particles, thereby improving the compaction density of the cathode material.

[0074] S20 involves sintering a mixture containing an oxide precursor with nitrate ions and a lithium source, followed by crushing the sintered product to obtain the cathode material.

[0075] In some embodiments, the lithium source includes at least one selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate. Preferably, the lithium salt is lithium carbonate.

[0076] In some embodiments, the amount of lithium source and oxide precursor added satisfies the following: the molar ratio of Li to the total molar ratio of all metals in the oxide precursor is (0.87 to 1.25):1, specifically it can be 0.87:1, 0.89:1, 0.92:1, 0.95:1, 0.98:1, 1.02:1, 1.05:1, 1.1:1, 1.17:1 or 1.25:1, etc. Of course, other values ​​within the above range are also possible, and are not limited here.

[0077] In some embodiments, the mixture further includes a dopant containing metal M, where M includes at least one selected from Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. Specifically, it may be a salt or oxide containing metal M.

[0078] In some embodiments, the dopant includes at least one of Nb₂O₅, Nb₂O₃, MoO₃, WO₂, WO₃, V₂O₅, V₂O₃, Sr(OH)₂, SrO, SrCO₃, TiO₂, ZrO₂, Zr(OH)₄, Y₂O₃, BaO, Cr₂O₃, ZnO, CuO, Ta₂O₅, CaO, Sb₂O₃, Sb₂O₅, H₃BO₃, MgO, and Mg(OH)₂. Preferably, the dopant containing metal M is a compound of Zr or Ti.

[0079] In some embodiments, the mixing conditions for obtaining the mixture are: solid-phase mixing at 10°C to 50°C for 0.3h to 3h.

[0080] In some embodiments, the solid-phase mixing temperature can be 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C, and the solid-phase mixing time can be 0.3h, 0.4h, 0.5h, 0.6h, 0.8h, 1h, 1.5h, 1.8h, 2.5h, or 3h, etc., or other values ​​within the above ranges, which are not limited here. Preferably, the solid-phase mixing temperature is 10°C to 35°C.

[0081] In some implementations, the mixing equipment may be at least one of a ball mill, a three-dimensional mixer, a high-speed mixer, and a VC mixer.

[0082] In some embodiments, the primary sintering process includes sequentially performing a first heating stage, a second heating stage, a first cooling stage, and a third isothermal stage. The temperature of the first heating stage is 300℃ to 600℃, the temperature of the second heating stage is 720℃ to 1000℃, the temperature of the first cooling stage is 500℃ to 700℃, and the temperature of the third isothermal stage is 720℃ to 1000℃.

[0083] In some embodiments, the temperature of the first heating stage can be 300°C, 350°C, 380°C, 400°C, 430°C, 450°C, 500°C, 550°C, 580°C, or 600°C, etc. The duration of the first heating stage is 3h to 5h, specifically 3h, 3.5h, 4h, 4.5h, or 5h, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The temperature of the first heating stage is relatively low, at which time the lithium source can fully melt and react with the oxide precursor.

[0084] In some embodiments, the heating rate of the first heating stage is 15℃ / min to 20℃ / min, specifically 15℃ / min, 16℃ / min, 17℃ / min, 18℃ / min, 19℃ / min or 20℃ / min, etc., and of course, other values ​​within the above range are also possible, which are not limited here.

[0085] In some embodiments, the temperature of the second heating stage can be 720°C, 770°C, 800°C, 880°C, 900°C, or 1000°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The duration of the second heating stage is 4h to 12h, specifically 4h, 5h, 6h, 8h, 9h, 10h, 11h, or 12h, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. During the second heating stage, the cathode material undergoes initial crystal growth while reducing excessive particle growth.

[0086] In some embodiments, the heating rate of the second heating stage is 0.5℃ / min to 3℃ / min, specifically 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 1.0℃ / min, 1.2℃ / min, 1.5℃ / min, 2.0℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min or 3℃ / min, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0087] In some embodiments, the temperature of the first cooling stage can be 500°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 690°C, or 700°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The duration of the first cooling stage is 2 hours to 6 hours, specifically 2 hours, 3 hours, 4 hours, 5 hours, 5.5 hours, or 6 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. This cooling process enables the surface atoms of the grown primary particles to rearrange, forming a surface structure with lower free energy and higher chemical stability.

[0088] In some embodiments, the cooling rate of the first cooling stage is 0.5℃ / min to 3℃ / min, specifically 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 1.0℃ / min, 1.2℃ / min, 1.5℃ / min, 2.0℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min or 3℃ / min, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0089] In some embodiments, the temperature of the third isothermal stage can be 720°C, 770°C, 800°C, 880°C, 900°C, or 1000°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The duration of the third isothermal stage is 1 hour to 3 hours, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. During this isothermal stage, the crystal structure of the primary particles of the cathode material is fully grown to ensure the structural stability of the primary particles.

[0090] In some embodiments, the heating rate of the third isothermal stage is 0.5℃ / min to 3℃ / min, specifically 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 1.0℃ / min, 1.2℃ / min, 1.5℃ / min, 2.0℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min or 3℃ / min, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0091] In some embodiments, the sintered product is cooled to room temperature after the third isothermal stage.

[0092] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere with an oxygen content ≥95%.

[0093] In some embodiments, when the dopant containing metal M is a compound of Zr or Ti, the temperature of the first sintering process is 800℃~900℃, and the holding time is 8h~10h.

[0094] In some embodiments, the method further includes: mixing the crushed matrix material with a coating agent containing metal M, and then performing a secondary sintering treatment to obtain a positive electrode material.

[0095] In some embodiments, the crushing method includes at least one of a double roller mill, a plow-type agitator / crusher, and an air jet mill.

[0096] In some embodiments, the coating agent containing metal M is selected from at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. The coating agent containing metal M can be a salt or oxide of metal M. Preferably, the coating agent containing metal M includes compounds of Nb and / or compounds of W.

[0097] In some embodiments, the secondary sintering process is carried out in an oxygen-containing atmosphere with an oxygen content ≥95%.

[0098] In some embodiments, the temperature of the secondary sintering treatment is 300℃ to 800℃, specifically 300℃, 320℃, 330℃, 350℃, 380℃, 400℃, 450℃, 500℃, 550℃, 650℃, 700℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0099] In some embodiments, the holding time for the secondary sintering treatment is 6h to 24h, specifically 6h, 8h, 10h, 12h, 15h, 18h or 24h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0100] In some embodiments, when the coating agent containing metal M includes a compound of Nb and / or a compound of W, the temperature of the secondary sintering treatment is 500°C to 600°C, and the holding time of the secondary sintering treatment is 6h to 8h.

[0101] In some embodiments, the preparation method further includes cooling, shaping, and sieving the product after secondary sintering. The shaping includes at least one of crushing, grinding, ball milling, or air crushing.

[0102] In some implementations, the sieve used for screening has a mesh size of 300 to 400.

[0103] 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.

[0104] 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.

[0105] In other embodiments, the secondary battery may also be a steel-cased battery, an aluminum-cased battery, etc.

[0106] 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.

[0107] 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.

[0108] In some embodiments, the positive electrode 1 includes a positive current collector 11 and a positive active material layer 12 disposed on at least one surface of the positive current collector 11.

[0109] In some embodiments, the positive electrode current collector 11 can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and the polymer substrate. The positive electrode active material layer 12 comprises a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material is the positive electrode material of the first aspect described above or a positive electrode material prepared according to the above-described method for preparing the positive electrode material.

[0110] In some embodiments, the negative electrode 2 includes a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on at least one surface of the negative electrode current collector.

[0111] In some embodiments, the negative electrode current collector 21 may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil or carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, the current collector formed by combining the aforementioned conductive foil and polymer substrate.

[0112] In some embodiments, the negative electrode active material layer 22 includes a negative electrode material, which includes, but is not limited to, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials in batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0113] 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.

[0114] 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.

[0115] Test method:

[0116] (1) Test of free nitrate content in positive electrode material

[0117] 1. Weigh approximately 0.7 g of sample (denoted as M) into a 70 mL beaker, accurate to 0.0001 g;

[0118] 2. Accurately measure 50 mL of ultrapure water (denoted as V) using a 50 mL volumetric flask. First, add a small amount of ultrapure water (about 7 mL) to the sample, stir evenly with a glass rod, then add the remaining ultrapure water, stir evenly, sonicate for 3 min, and let stand for about 17 min to allow the sample to precipitate.

[0119] 3. Using a 1 mL sterile syringe, draw up the sample supernatant and inject it into the ion chromatograph through a disposable filter head for testing; Ion chromatograph model: Thermo Scientific Dionex ICS-6000; Chromatographic settings: Eluent concentration: 25 mmol / L; Eluent flow rate: 0.3 mL / min; Column temperature: 30±1℃; Detector cell temperature: 35±1℃; Suppressor current: 26 mA; Column: Anion exchange column (4×250 mm, AS11-HC); Data acquisition: After the baseline stabilizes (signal value change less than 0.1 μS / 20 min), click data acquisition to start the analysis and obtain the concentration of element i in the sample, denoted as Ci.

[0120] 4. Result Calculation: The calculation formula is Q = Ci × V / M, where Q is the content of element i in the sample (mg / kg); Ci is the concentration of element i in the sample solution (mg / L); V is the volume of the sample solution (mL); and M is the mass of the sample (g). In anion testing, by measuring the content of nitrogen (N) element, the nitrate (NO3) can be converted to its molecular weight using ion analysis. - The analytical method for the content of free sulfate is the same as that for the content of nitrate.

[0121] (2) The proportion of particles with a diameter of less than 1 μm in the cathode material

[0122] 1) Use a cotton swab to pick up a small amount of powder sample and spread it evenly and densely on the conductive adhesive; use a hair dryer to slowly blow it in the direction where there are no other samples, and when you are sure that it is evenly spread on the surface, blow it strongly more than 10 times until there is no powder residue.

[0123] 2) Set the basic SEM conditions: voltage 5kV, current 12mA, magnification 2kx, adjust contrast and brightness using the auto key, and randomly select 10 areas with 400 to 1200 particles to take SEM images.

[0124] 3) Import the electron microscope image obtained in step (2) into the Metis Vision software, click "Identify All" in the software interface to obtain the particle size distribution data and particle size distribution map in the electron microscope image, thereby obtaining the proportion R of particles with a particle size of less than 1 μm in the cathode material.

[0125] (3) IPC testing method for cathode materials:

[0126] Equipment: Agilent 5110ICP-OES Plasma Inductive Coupling System.

[0127] Method: Take 0.3g of sample, add aqua regia to digest, cool and make up to 100mL of mother liquor. Take 1mL of mother liquor, dilute 100 times and test the content of main elements Li / Ni / Co / Mn / Al. Test the content of impurity elements in the mother liquor.

[0128] (4) Test method for particle size of cathode material:

[0129] The particle size distribution range of the cathode material was measured using a Malvern laser particle size analyzer to obtain D90, D50, and D10. D90 refers to the particle size corresponding to a cumulative volume fraction of 90%, D50 to 50%, and D10 to 10%. Span = (D90 - D10) / D50.

[0130] Specifically, take an appropriate amount of sample, pour it into pure water and ultrasonically disperse it for 30 seconds at a power of 240W. Then, add an appropriate amount of sodium hexametaphosphate to the dispersed sample, stir well, and pour it into the sample pool of the testing equipment. After waiting for 10 seconds, click to start the sample test.

[0131] (5) Average size of primary particles of cathode material

[0132] Five random images of samples at 3000x magnification from different locations were taken using a Hitachi S4800 scanning electron microscope. The maximum diameter of the single-crystal particles completely visible within the field of view was measured using Nano Measure software. The average diameter of these particles was calculated as the average particle size. A single-crystal particle completely visible within the field of view is defined as one whose outline is fully displayed in the electron microscope image, without being obscured by other single-crystal particles or divided by the boundaries of the electron microscope image. The maximum diameter of a single-crystal particle refers to the diameter of its circumcircle in the electron microscope image.

[0133] (6) Test method for specific surface area of ​​cathode material:

[0134] Equipment: The specific surface area of ​​the cathode material was tested using a Microt Tristar 3020 specific surface area and pore size analyzer.

[0135] Method: Weigh the empty sample tube (mL); add 3g of sample into the sample tube through a long-necked funnel; degas under vacuum at 300℃ for 1h, cool, and weigh the sample tube (m2); the sample mass is m = m2 - m1. Place the sample tube in liquid nitrogen and measure the nitrogen adsorption capacity V of the sample under a series of relative pressures P / P0 to obtain adsorption isotherms. P / P0 is set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. Fit the isothermal adsorption curve, calculate the monolayer saturated adsorption capacity Vm based on the slope and intercept, and then calculate the specific surface area based on Vm.

[0136] (7) Canta tap density test of cathode material:

[0137] Equipment: A Canta DAT-4-220 tap density meter (USA) was used.

[0138] Method: Clean the graduated cylinder and weigh it (mL); add approximately 50g of sample into 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 (m2); place the graduated cylinder on the vibration stage and secure it with three symmetrical feet; turn on the instrument and set the vibration frequency to 5000 times; turn on the vibration switch, and 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); compaction density = (m2 - m1) / V.

[0139] (8) Cathode material compaction density test:

[0140] The compaction density of the cathode material was tested using a Carver 4350 from the United States. The procedure was as follows: weigh 1g of sample and place it in a mold, press it with a pressure of 3T for 30s, and then measure the height to calculate the compaction density.

[0141] (9) Test of loose packing density of positive electrode material:

[0142] Equipment: Beijing Zheyuan Loose Density Meter BT101

[0143] Method: Take an appropriate amount of sample and let it flow naturally into the cloth box, passing alternately through four glass plates with an inclination angle of 25° and a square funnel in the cloth box, and then into a cylindrical cup of known volume (25mL). Finally, weigh the mass of the powder in the cylindrical cup.

[0144] (10) Electrochemical performance testing:

[0145] The positive electrode materials obtained in the examples and comparative examples were assembled into coin cells: the positive electrode material, conductive carbon, and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) at a mass ratio of 96:2:2, and uniformly mixed to form a positive electrode slurry. This slurry was then coated onto a positive electrode current collector and vacuum dried to form a positive electrode sheet (the sheet's compaction density was 2.8 g / cm³). 3 Using lithium foil as the negative electrode, 2016 button batteries are assembled in a glove box.

[0146] After the assembled button cells were left to stand for 12 hours, capacity and cycle performance tests were conducted using the LAND battery testing system at 25°C and 3.0–4.45V. The nominal capacity at 1C was set to 200 mAh / g. The cells were cycled 50 times at a 0.5C charge-1C discharge rate. The ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 1st cycle was taken as the 50-cycle retention rate.

[0147] Discharge specific capacity test method:

[0148] The assembled button cells were tested using a CT3002A battery testing system. Charge and discharge tests were conducted at 0.3C / 0.3C rates in the 3.0V-4.3V discharge range at 25℃ to obtain the 0.1C discharge specific capacity (discharge capacity / mass), 1C discharge specific capacity, and 2C discharge specific capacity.

[0149] The method for testing the initial coulombic efficiency is as follows: The above-mentioned button cells are tested using a CT3002A battery testing system. The cells are charged and discharged once at a rate of 0.1C / 0.1C. The discharge specific capacity and charge specific capacity are obtained. The initial coulombic efficiency = discharge specific capacity / charge specific capacity.

[0150] (11) Structural recovery degree test:

[0151] The structural changes during the charge and discharge process were tested by electrochemical in-situ XRD using a Bruker D8 Advance (Cu target) device with a blue electric (5mA, 5V) device. The charge and discharge voltage range was 2.8V to 4.35V. The XRD spectrum was then fitted using Jade software to obtain the diffraction angles corresponding to the (003) peak at the beginning and end of the charge and discharge.

[0152] Specifically, the cathode materials prepared in the above embodiments and comparative examples are assembled to form mold batteries. The outer casing of the mold battery is provided by the Bruker in-situ XRD equipment, and the outer casing has a window that allows X-rays from the XRD equipment to pass through. The specific procedure is as follows: Cathode material, conductive carbon black, and PVDF are weighed in a mass ratio of 93:5:2. N-methyl-2-pyrrolidone (NMP) is added at a solid content of 50%, and dispersed into a viscous slurry using a high-speed disperser. The slurry is then uniformly coated onto aluminum foil using a 200-micron scraper. After baking in an oven at 80°C for 30 minutes, the slurry is rolled and punched into a cathode sheet with a diameter of 14 mm. The slurry is then placed back into the oven and baked at 80°C for 8 hours. Using a prepared positive electrode sheet, a 16mm lithium sheet as the negative electrode sheet, a Celgard polypropylene membrane as the separator, and a 1mol / L LiPF6 carbonate solution as the electrolyte, the mold battery was assembled in an argon-filled glove box using the casing of the XRD equipment. The mold battery was then subjected to charge-discharge tests at 25℃ and 2.5V-4.35V. Electrochemical in-situ XRD was used to characterize the change in the (003) peak of the positive electrode material during one cycle. θ1 represents the diffraction angle of the positive electrode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the beginning of the first charge cycle, and θ2 represents the diffraction angle of the positive electrode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the end of the first discharge cycle.

[0153] Example 1

[0154] (1) Dissolve metallic nickel, metallic manganese, and metallic cobalt separately in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total Ni, Co, and Mn concentration of 2 mol / L according to the stoichiometric ratio of Ni:Co:Mn = 6:1:3. Continuously pass a 1 mol / L NaOH solution and a 0.5 mol / L ammonia solution into the mixed solution, controlling the pH value within the range of 11 ± 0.2. When D 50 When the sediment reaches 8 μm, the reaction is stopped, and the sediment is centrifuged, washed, and dried to obtain the hydroxide precursor of the cathode material.

[0155] (2) The cathode material hydroxide precursor was placed in an atmosphere with a nitric acid concentration of 2% for nitrification annealing treatment; the atmosphere contained only HNO3 and H2O, and the O2 content was <1.0ppm; the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 6h for annealing; during the annealing process, the gas pressure of the reaction environment was controlled at 3.0kPa to obtain the oxide precursor, whose general chemical formula is Ni. 0.6 Co 0.1 Mn 0.3 O x (The content of each element is within ±1%).

[0156] (3) The oxide precursor and Li2CO3 were mixed at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1, and ZrO2 with a mass content of 2000ppm relative to the oxide precursor was added. The mixture was placed in an atmosphere electric furnace or Joule thermal reactor, using an oxygen atmosphere, and the reaction pressure was controlled at 10Pa. The temperature was increased from room temperature to 500℃ at a heating rate of 20℃ / min in the first heating stage and held for 4h. The temperature was increased to 700℃ in the second heating stage at a heating rate of 2℃ / min and held for 6h. The temperature was decreased to 500℃ in the first cooling stage at a cooling rate of 1℃ / min and held for 4h. The temperature was increased to 900℃ in the third isothermal stage at a heating rate of 1℃ / min and held for 2h. The temperature was decreased from the fourth plateau temperature to room temperature at a cooling rate of 2℃ / min to obtain the matrix material.

[0157] (4) After crushing the matrix material, it is mixed with 1000ppm Nb2O5 and sintered at 500℃ for 6h in an oxygen atmosphere to obtain the cathode material.

[0158] The general chemical formula of the cathode material is Li 1.02 Ni 0.6 Co 0.1 Mn 0.297 Zr 0.002 Nb 0.001 O2.

[0159] Example 2

[0160] The difference from Example 1 is:

[0161] (1) Dissolve metallic nickel, metallic manganese, and metallic cobalt separately in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total Ni, Co, and Mn concentration of 2 mol / L by mixing the three solutions in a stoichiometric ratio of Ni:Co:Mn = 67:5:28. Add appropriate amounts of citric acid and ethylene glycol to the mixed solution to control the pH value within the range of 8±0.2, and then place it in a reaction vessel and keep it at 180℃ for 24 h to obtain a gel precipitate. Centrifuge, wash, and dry the gel precipitate to obtain the gel precursor.

[0162] (2) The gel precursor was placed in an atmosphere containing 2% nitric acid for nitrification annealing. The atmosphere contained only HNO3 and H2O, with an O2 content of <1.0 ppm. The temperature was increased to 600℃ at a heating rate of 2℃ / min and held for 6 hours for annealing. During the annealing process, the gas pressure of the reaction environment was controlled at 3.0 kPa to obtain the oxide precursor with the general chemical formula Ni. 0.67 Co 0.05 Mn 0.28 O x (The content of each element is within ±1%).

[0163] (3) Mix the oxide precursor with Li2CO3 at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.01:1, and add TiO2 with a mass content of 1000ppm relative to the oxide precursor. The subsequent sintering process is the same as step (3) of Example 1.

[0164] (4) After crushing the matrix material, it is mixed with 1500ppm of Al2O3 and sintered at 500℃ for 6h in an oxygen atmosphere to obtain the cathode material.

[0165] The general chemical formula of the cathode material is Li 1.01 Ni 0.67 Co 0.05 Mn 0.274 Ti 0.002 Al 0.004 O2.

[0166] Example 3

[0167] The difference from Example 1 is:

[0168] (1) Dissolve metallic nickel, metallic manganese, and metallic cobalt separately in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total Ni, Co, and Mn concentration of 2 mol / L by mixing the three solutions in a stoichiometric ratio of Ni:Co:Mn = 6:1:3. Continuously add an appropriate amount of ammonia to the mixed solution to maintain the pH value within the range of 7 ± 0.2. When D... 50 When the particle size reaches 8 μm, the reaction is stopped, and the resulting mixed solution is subjected to a spray pyrolysis process to obtain the hydroxide precursor of the cathode material.

[0169] (2) The cathode material hydroxide precursor was placed in an atmosphere with a nitric acid concentration of 3% for nitrification annealing treatment; the atmosphere contained only HNO3 and H2O, and the O2 content was <1.0ppm; the temperature was raised to 200℃ at a heating rate of 3℃ / min and held for 3h for annealing; during the annealing process, the gas pressure of the reaction environment was controlled at 2.0kPa to obtain the oxide precursor, whose general chemical formula is Ni. 0.6 Co0.1 Mn 0.3 O x (The content of each element is within ±1%).

[0170] The general chemical formula of the cathode material is Li 1.02 Ni 0.6 Co 0.1 Mn 0.297 Zr 0.002 Nb 0.001 O2.

[0171] Example 4

[0172] The difference from Example 1 is:

[0173] (3) The oxide precursor and Li2CO3 were mixed at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1, and ZrO2 with a mass content of 2000ppm relative to the oxide precursor was added. The mixture was placed in an atmosphere electric furnace or Joule thermal reactor, using an oxygen atmosphere, and the reaction pressure was controlled at 10Pa. The temperature was increased from room temperature to 300℃ at a heating rate of 20℃ / min in the first heating stage and held for 5h. The temperature was increased to 900℃ in the second heating stage at a heating rate of 2℃ / min and held for 4h. The temperature was decreased to 600℃ in the first cooling stage at a cooling rate of 1℃ / min and held for 6h. The temperature was increased to 700℃ in the third isothermal stage at a heating rate of 0.5℃ / min and held for 6h. The temperature was decreased from the fourth plateau temperature to room temperature at a cooling rate of 1℃ / min to obtain the matrix material.

[0174] The general chemical formula of the cathode material is Li 1.02 Ni 0.6 Co 0.1 Mn 0.297 Zr 0.002 Nb 0.001 O2.

[0175] Example 5

[0176] Unlike Example 4:

[0177] (1) Dissolve metallic nickel, metallic manganese, and metallic cobalt separately in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total concentration of 2 mol / L of Ni, Co, and Mn according to the stoichiometric ratio of Ni:Co:Mn = 90:5:5. Add appropriate amounts of citric acid and ethylene glycol to the mixed solution to control the pH value within the range of 7-9, and then place it in a reaction vessel and keep it at 180℃ for 24 h to obtain precipitate. Centrifuge, wash, and dry the precipitate to obtain the hydroxide precursor of the positive electrode material.

[0178] (2) The cathode material hydroxide precursor was placed in an atmosphere with a nitric acid concentration of 1% for nitrification annealing treatment; the atmosphere contained only HNO3 and H2O, and the O2 content was <1.0ppm; the temperature was raised to 800℃ at a heating rate of 0.5℃ / min and held for 10h for annealing; during the annealing process, the gas pressure of the reaction environment was controlled at 2.0kPa to obtain the oxide precursor, whose general chemical formula is Ni. 0.6 Co 0.1 Mn 0.3 O x (The content of each element is within ±1%).

[0179] The general chemical formula of the cathode material is Li 1.02 Ni 0.9 Co 0.05 Mn 0.046 Zr 0.002 Nb 0.002 O2.

[0180] Example 6

[0181] Unlike Example 4:

[0182] (3) Mix the oxide precursor with Li2CO3 at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 0.99:1.

[0183] The general chemical formula of the cathode material is Li 0.99 Ni 0.6 Co 0.1 Mn 0.297 Zr 0.002 Nb 0.001 O2.

[0184] Example 7

[0185] Unlike Example 4:

[0186] (1) Dissolve metallic nickel, metallic manganese and metallic cobalt in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total concentration of 2 mol / L of Ni, Co and Mn according to the stoichiometric ratio of Ni:Co:Mn = 83:11:06.

[0187] Example 8

[0188] Unlike Example 4:

[0189] (1) Dissolve metallic nickel, metallic manganese and metallic cobalt in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total concentration of 2 mol / L of Ni, Co and Mn according to the stoichiometric ratio of Ni:Co:Mn = 75:15:10.

[0190] Example 9

[0191] The difference from Example 2 is:

[0192] (2) The cathode material hydroxide precursor was placed in an atmosphere with a nitric acid concentration of 2% for nitrification annealing treatment; the atmosphere contained only HNO3 and H2O, and the O2 content was <1.0ppm; the temperature was raised to 600℃ at a heating rate of 2℃ / min and held for 8h for annealing; during the annealing process, the gas pressure of the reaction environment was controlled at 4.0kPa to obtain the oxide precursor with the general chemical formula Ni. 0.67 Co 0.05 Mn 0.28 O x (The content of each element is within ±1%).

[0193] Example 10

[0194] The difference from Example 1 is:

[0195] (3) The oxide precursor and Li2CO3 are mixed at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1, and ZrO2 with a mass content of 2000ppm relative to the oxide precursor is added. The mixture is placed in an atmosphere electric furnace or Joule thermal reactor, using an oxygen atmosphere, and the reaction pressure is controlled at 10Pa. The temperature is increased from room temperature to 600℃ at a heating rate of 20℃ / min in the first heating stage and held for 5h. The temperature is increased to 1000℃ in the second heating stage at a heating rate of 2℃ / min and held for 3h. The temperature is decreased to 550℃ in the first cooling stage at a cooling rate of 1℃ / min and held for 4h. The temperature is increased to 850℃ in the third isothermal stage at a heating rate of 1℃ / min and held for 3h. The temperature is decreased from the fourth plateau temperature to room temperature at a cooling rate of 2℃ / min to obtain the matrix material.

[0196] Example 11

[0197] The difference from Example 1 is:

[0198] (1) Dissolve metallic nickel, metallic manganese, and metallic cobalt separately in nitric acid to form nitrate solutions; prepare a mixed solution with a total Ni, Co, and Mn concentration of 2 mol / L by stoichiometric ratio of Ni:Co:Mn = 6:1:3. Continuously pass 1 mol / L NaOH solution and 0.5 mol / L ammonia solution into the mixed solution, maintaining the pH value within the range of 11 ± 0.2. When D... 50 When the sediment reaches 8 μm, the reaction is stopped, and the sediment is centrifuged, washed, and dried to obtain the hydroxide precursor of the cathode material.

[0199] Example 12

[0200] The difference from Example 1 is:

[0201] (3) The oxide precursor and Li2CO3 are mixed at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1 and placed in an atmosphere electric furnace or Joule thermal reactor. An oxygen atmosphere is used and the reaction pressure is controlled at 10 Pa. The temperature is increased from room temperature to 500℃ at a heating rate of 20℃ / min and held for 4 hours. The temperature is increased to 700℃ at a heating rate of 2℃ / min and held for 6 hours. The temperature is decreased to 500℃ at a cooling rate of 1℃ / min and held for 4 hours. The temperature is increased to 900℃ at a heating rate of 1℃ / min and held for 2 hours. The temperature is decreased from the temperature of the third isothermal stage to room temperature at a cooling rate of 2℃ / min to obtain the matrix material.

[0202] (4) After crushing the matrix material, it is sintered again at 500°C for 6 hours in an oxygen atmosphere to obtain the cathode material.

[0203] The general chemical formula of the cathode material is Li 1.02 Ni 0.6 Co 0.1 Mn 0.3 O2.

[0204] Example 13

[0205] The difference from Example 1 is:

[0206] (1) Dissolve metallic nickel, metallic aluminum, and metallic cobalt separately in sulfuric acid to form sulfate solutions; prepare a mixed solution with a total Ni, Co, and Al concentration of 2 mol / L by mixing the three solutions in a stoichiometric ratio of Ni:Co:Al = 80:15:5. Add appropriate amounts of citric acid and ethylene glycol to the mixed solution to control the pH value within the range of 8±0.2, and then place it in a reaction vessel and keep it at 180℃ for 24 h to obtain a gel precipitate. Centrifuge, wash, and dry the gel precipitate to obtain the gel precursor.

[0207] The general chemical formula of the cathode material is Li 1.02 Ni 0.8 Co 0.15 Al 0.046 Zr 0.002 Nb 0.002 O2.

[0208] Comparative Example 1

[0209] The difference from Example 1 is:

[0210] (2) Ni hydroxide precursor of positive electrode material 0.6 Co 0.1 Mn 0.3 (OH)x Annealing was performed by heating to 200℃ at a heating rate of 3℃ / min and holding at that temperature for 3 hours to obtain an oxide precursor with the general chemical formula Ni. 0.6 Co 0.1 Mn 0.3 O x (The content of each element is within ±1%).

[0211] Comparative Example 2

[0212] The difference from Example 5 is:

[0213] (2) The hydroxide precursor of the positive electrode material was heated to 800℃ at a heating rate of 0.5℃ / min and held at that temperature for 10h for annealing. During the annealing process, the gas pressure of the reaction environment was controlled at 2.0kPa to obtain the oxide precursor, whose general chemical formula is Ni. 0.6 Co 0.1 Mn 0.3 O x (The content of each element is within ±1%).

[0214] Comparative Example 3

[0215] The difference from Example 2 is:

[0216] (2) The hydroxide precursor of the positive electrode material is heated to 600℃ at a heating rate of 2℃ / min and annealed for 6h to obtain the oxide precursor with the general chemical formula Ni. 0.67 Co 0.05 Mn 0.28 O x (The content of each element is within ±1%).

[0217] Comparative Example 4

[0218] The difference from Example 1 is:

[0219] (3) Mix the oxide precursor with Li2CO3 at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1, and add ZrO2 with a mass content of 2000ppm relative to the oxide precursor. Place the mixture in an atmosphere electric furnace or Joule thermal reactor, using an oxygen atmosphere, and control the reaction pressure at 10Pa. Increase the temperature from room temperature to 900℃ at a heating rate of 20℃ / min, hold for 12h, and then cool the sintered product to room temperature to obtain the matrix material.

[0220] Comparative Example 5

[0221] The difference from Example 1 is:

[0222] (3) Mix the oxide precursor with Li2CO3 at a molar ratio of Li / Me (Me is the sum of Ni, Co and Mn) of 1.02:1, and add ZrO2 with a mass content of 2000ppm relative to the oxide precursor. Place the mixture in an atmosphere electric furnace, use an oxygen atmosphere, and control the reaction pressure at 10Pa. Increase the temperature from room temperature to 700℃ at a heating rate of 2℃ / min and hold for 8h. Reduce the sintered product to room temperature to obtain the matrix material.

[0223] The cathode materials prepared in the examples and comparative examples were subjected to relevant tests, and the test data are shown in Tables 1 and 2:

[0224] Table 1. Performance Comparison of Cathode Materials in Examples and Comparative Examples

[0225] Table 2. Comparison of electrochemical performance of cathode materials in the examples and comparative examples.

[0226] According to the test data of Examples 1 to 13, when the mass content of free nitrate in the cathode material is controlled between 10 ppm and 100 ppm, and the proportion of particles with a diameter of less than 1 μm in the cathode material is controlled between 8% and 16%, the synergistic effect of appropriate amount of free nitrate and particles with a diameter of less than 1 μm can improve the high voltage resistance and high capacity of the cathode material, while also improving the lithium-ion transport efficiency and cycle stability of the cathode material. Although the cathode materials in Comparative Examples 1-3 met the requirement that the proportion of particles smaller than 1 μm was between 8% and 16%, they did not meet the requirement that the mass content of free nitrate in the cathode materials was between 10 ppm and 100 ppm. Although Comparative Examples 4-5 met the requirement that the mass content of free nitrate in the cathode materials was between 10 ppm and 100 ppm, they did not meet the requirement that the proportion of particles smaller than 1 μm was between 8% and 16%. The initial coulombic efficiency, 50-cycle capacity retention, and structural recovery of the cathode materials in Comparative Examples 1-5 were not as good as those in Examples 1-13.

[0227] Based on the test data from Examples 1 and 3-4, the cycle stability of the cathode material prepared in Example 3 is superior to that in Examples 1 and 4. The cathode material in Example 4 has a lower free nitrate content, resulting in a slight decrease in cycle stability. The applicant speculates that this is because the free nitrate in the cathode material can induce the formation of an appropriate amount of lithium oxide on the surface of the cathode material during cycling, thereby reducing the surface energy of the cathode material and contributing to improved crystal structure stability.

[0228] According to the test data of Examples 4 to 8, as the mass percentage of nickel atoms in the cathode material increases, the discharge specific capacity of the cathode material also increases. As long as the mass content of free nitrate ions and the proportion of particles with a particle size of less than 1 μm in the cathode material are controlled within a suitable range, different series of cathode materials can have high voltage resistance, high capacity and excellent cycle stability.

[0229] Based on the test data from Examples 2 and 9, and Examples 1 and 10, it can be seen that, compared to Example 2, the cathode material prepared in Example 9 had a higher proportion of particles with a diameter less than 1 μm. Although the compaction density of the cathode material increased, the increased number of small particles also led to more side reactions, resulting in a slight decrease in the discharge capacity and cycle capacity retention rate of the cathode material. Compared to Example 1, the cathode material prepared in Example 10 had a lower proportion of particles with a diameter less than 1 μm, and its discharge capacity and cycle capacity retention rate increased.

[0230] Based on the test data from Comparative Example 1 and Example 1, Comparative Example 2 and Example 5, and Comparative Example 3 and Example 2, and referring to Figures 2 and 3, after the first charge-discharge cycle of the battery prepared from the cathode material, the free nitrate content of the cathode material in Comparative Example 1 was 0. The XPS characterization spectrum showed that the main component of the solid electrolyte film on the surface of the cathode material was ROCO2Li. In contrast, the cathode material in Example 1 had a suitable amount of free nitrate, which induced the formation of Li2O on the surface of the cathode material after the first charge-discharge cycle. Li2O has high voltage resistance, which helps improve the high voltage resistance of the cathode material and reduces the occurrence of side reactions between the cathode material and the electrolyte. Therefore, the initial efficiency of the cathode material in Comparative Example 1 decreased, and the cycle capacity retention rate under high voltage also decreased significantly. Similarly, compared to Example 5, the discharge specific capacity, initial efficiency, and cycle capacity retention rate of the cathode material in Comparative Example 2 and Comparative Example 3 compared to Example 2 also decreased significantly.

[0231] According to the test data of Comparative Example 4 and Example 1, the free nitrate content of the cathode material in Comparative Example 4 is within a suitable range. However, due to the high sintering temperature and excessive heating rate, some particles fused together. The proportion of particles with a diameter of less than 1 μm in the cathode material of Comparative Example 4 was too small. The lithium ion transport path increased, the compaction density of the cathode material decreased, the lithium ion transport path increased, the lithium insertion / extraction efficiency of the cathode material decreased, and the discharge capacity of the cathode material decreased significantly.

[0232] According to the test data of Comparative Example 5 and Example 1, the free nitrate content of the cathode material in Comparative Example 5 is within a suitable range. However, due to the low sintering temperature, the proportion of particles with a diameter of less than 1 μm in the cathode material of Comparative Example 5 is too high. This increases the particle size distribution width of the cathode material, increases the specific surface area of ​​the cathode material, and makes the side reactions between small particles and electrolyte more severe, resulting in a decrease in the cycle capacity retention rate of the cathode material.

[0233] 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 free nitrate content of the cathode material is Q ppm, 10≤Q≤100; in the scanning electron microscope image of the cathode material, the percentage of particles with a diameter less than 1μm is R%, 8≤R≤16. The cathode material is dispersed in pure water, and after ultrasonic filtration, the mass content of free nitrate ions Q ppm of the cathode material is obtained by characterizing the filtrate using an ion chromatograph.

2. The cathode material according to claim 1, characterized in that, The cathode material satisfies any one of the following conditions: (1)19≤Q≤98； (2)47≤Q≤98； (3) The mass content of free nitrate in the positive electrode material is a range of 10ppm, 12ppm, 25ppm, 30ppm, 50ppm, 68ppm, 75ppm, 80ppm, 85ppm, 95ppm, 100ppm or any two of these.

3. The cathode material according to claim 1, characterized in that, The cathode material satisfies any one of the following conditions: (1)8≤R≤12.6； (2)8≤R≤14.5； (3) The proportion of particles with a diameter less than 1 μm in the positive electrode material is 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or any two of these proportions.

4. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The volumetric particle size distribution of the cathode material satisfies: 0.2μm≤D10≤2.0μm; (2) The volumetric particle size distribution of the positive electrode material satisfies: 2.0 μm ≤ D50 ≤ 5.0 μm; (3) The volumetric particle size distribution of the positive electrode material satisfies: 6.0μm≤D90≤12.0μm.

5. The cathode material according to claim 1, characterized in that, The free sulfate content of the positive electrode material is K ppm, and 10≤K≤800.

6. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The cathode material is a single crystal material; (2) The positive electrode material comprises grains with the same orientation, and the average grain size is 1 μm to 5 μm; (3) The positive electrode material includes primary particles, and the average particle size of the primary particles is 1 μm to 5 μm.

7. The cathode material according to claim 1, characterized in that, The chemical general formula of the positive electrode material is Li n Ni x Co y N z M s O2, wherein, 0.9≤n≤1.1, 0 x+y+z+s=1, N includes at least one of Mn and Al, and M includes at least one of Zr, Mg, W, Mo, Ti, Ba, Sr, Cr, Zn, Y, V, Cu, B, Nb.

8. The positive electrode material according to claim 1, characterized in that, The specific surface area of ​​the positive electrode material is 0.5 m². 2 / g~1.5m 2 / g.

9. The positive electrode material according to claim 1, characterized in that, The cathode material is formed into a mold battery, and the cathode material is characterized by in-situ XRD. During the first charge and discharge cycle, the structural recovery degree δ of the cathode material satisfies: 99.7% ≤ δ ≤ 100.0%; where δ = θ1 / θ2 × 100%, θ1 is the diffraction angle of the cathode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the beginning of the first charge cycle, and θ2 is the diffraction angle of the cathode material at the (003) crystal plane diffraction peak measured by X-ray diffraction at the end of the first discharge cycle.

10. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following technical characteristics: (1) The compaction density of the positive electrode material is 2.5 g / cm³. 3 ~3.5g / cm 3 ; (2) The loose packing density of the positive electrode material is 0.5 g / cm³. 3 ~1.5g / cm 3 ; (3) The tap density of the positive electrode material is 1.0 g / cm³. 3 ~3.0g / cm 3 .

11. The cathode material according to claim 1, characterized in that, After the cathode material was made into a coin cell and charged and discharged for one week, the cathode material was characterized by XPS. The XPS spectrum of the cathode material showed that the cathode material had a Li2O phase.

12. The cathode material according to claim 11, characterized in that, In the XPS spectrum of the cathode material, the cathode material has a characteristic peak between 53.5 eV and 55 eV in binding energy.

13. The cathode material according to claim 1, characterized in that, The volumetric particle size distribution of the cathode material satisfies: 0.8≤(D90-D10) / D50≤2.

0.

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

15. A battery, characterized in that, The battery includes the positive electrode sheet as described in claim 14 or the positive electrode material as described in any one of claims 1 to 13.

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