Lithium ion battery cathode material, preparation method and application thereof

Abstract

The application belongs to the field of lithium ion batteries, and particularly relates to a lithium ion battery positive electrode material and a preparation method and application thereof. The lithium ion battery positive electrode material comprises lithium ion battery positive electrode material base particles and a coating layer coated on the surface of the lithium ion battery positive electrode material base particles; the composition of the coating layer comprises fluoride and oxide converted from the fluoride; the fluoride is one or more of FeF3, CrF3, VF4, TmF3, NdF3, PrF3, CeF3, SnF4 and DyF3; the mass proportion of the fluoride in the coating layer is greater than or equal to 20 wt%; and the total content of the fluoride and the oxide in the lithium ion battery positive electrode material is 1500-3500 ppm in terms of metal elements. By regulating the F / O ratio and the coating amount of the coating layer on the surface of the positive electrode material, the lithium ion battery positive electrode material can exhibit very excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion batteries, and particularly relates to a lithium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] In lithium-ion batteries, the cathode material plays a decisive role in battery performance. Ternary nickel-cobalt-manganese cathode materials are emerging cathode materials in recent years. Their cost and cobalt usage are far lower than traditional lithium cobalt oxide cathode materials, while their energy density (energy density = voltage × capacity) is higher than that of the popular lithium iron phosphate materials. Due to their important advantages such as low cost, good environmental performance, high capacity, and good cycle performance, ternary nickel-cobalt-manganese cathode materials are widely used in the field of power batteries.

[0003] However, ternary materials have the following problems in application: (1) With the increase of nickel content, the energy density increases, but the thermal stability and cycle stability are insufficient, and the safety and lifespan cannot meet the requirements of power batteries; (2) In the low-nickel ternary system, the battery performance is poor during high-current fast charging and discharging, and the rate performance advantage is insufficient. The main reasons for these problems are as follows: (1) Low-nickel ternary cathode materials have relatively low conductivity; (2) In the layered structure of ternary cathode materials, due to the low conductivity of Li + (0.76) with Ni 2+ (0.69) Atomic radii are similar, and Ni in the Ni-O layer 2+ The crystal field stabilization energy is low, and during the preparation process, some Li in the crystal structure... + Easy and Ni 2+ A positional interchange occurs (i.e., cation mixing occurs), which leads to changes in the Li content during charging and discharging. + The resistance to ion diffusion increases, and the Ni in high-nickel ternary materials increases during cycling. 2+ The migration of nickel can also lead to phase transition, destroy the layered structure of the material, and affect the electrochemical performance of the material. The higher the nickel content, the more obvious this phenomenon is; (3) As the nickel content or the cutoff voltage increases, the structural stability of the material decreases during cycling, and the thermal stability decreases, the battery safety performance decreases, and the accident rate increases.

[0004] Therefore, to address the problems of ternary cathode materials in lithium-ion batteries and fully leverage their advantages, one of the most common methods is surface coating. By coating ternary nickel-cobalt-manganese cathode materials, side reactions between the material and the electrolyte can be suppressed, improving the stability of the material structure, increasing the conductivity, and thus enhancing the cycle stability and rate performance. Furthermore, if the coated material also possesses excellent Li... + Ion conductivity (such as lithium salt compounds like Li2SO4) can further enhance the capacity of the material and improve its rate performance.

[0005] Currently, the main method to improve the properties of ternary cathode materials for lithium-ion batteries is through oxide coating. However, during long-term cycling and high-temperature storage, the coated oxide is easily corroded by the by-reaction product HF, which can lead to the failure of the coating layer and thus reduce its electrochemical performance. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a lithium-ion battery cathode material, its preparation method and application. The lithium-ion battery cathode material provided by this invention has excellent electrochemical performance.

[0007] The present invention provides a lithium-ion battery cathode material, comprising lithium-ion battery cathode material matrix particles and a coating layer covering the surface of the lithium-ion battery cathode material matrix particles;

[0008] The coating layer comprises fluorides and oxides converted from the fluorides; the fluorides are one or more of FeF3, CrF3, VF4, TmF3, NdF3, PrF3, CeF3, SnF4, and DyF3; the fluorides account for ≥20 wt% of the mass percentage in the coating layer; and the total content of the fluorides and oxides in the lithium-ion battery cathode material, calculated as metal elements, is 1500–3500 ppm.

[0009] Preferably, the general chemical formula of the lithium-ion battery cathode material matrix particles is Li. x Ni y Co z M1 m M2 n O2, wherein M1 is Al and / or Mn, and M2 is at least one of Ti, Ba, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, B and Cu; x, y, z and m are all > 0, n ≥ 0, and the values ​​of x, y, z, m and n satisfy the charge balance of the general chemical formula.

[0010] Preferably, 1≤x≤1.1, 0.5≤y<1, 0<z≤0.3, 0<m≤0.3, and 0.002≤n≤0.005.

[0011] This invention provides a method for preparing the lithium-ion battery cathode material described in the above technical solution, comprising the following steps:

[0012] The lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor are mixed and sintered to obtain the lithium-ion battery cathode material.

[0013] Preferably, the conversion inhibitor is one or more of SnCl2, H2C2O4, KBH4, Na2SO3, NaBH4, NH4F, and LiAlH4.

[0014] Preferably, the mass ratio of the lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor is 100:(0.25-0.5):(0.03-0.12).

[0015] Preferably, the sintering is carried out under oxygen-free or oxygen-containing conditions.

[0016] Preferably, the sintering temperature is 200–500°C; and the sintering time is 3–10 h.

[0017] Preferably, the lithium-ion battery cathode material matrix particles are prepared according to the following steps:

[0018] The lithium source, nickel source, cobalt source, M1 source and M2 source are mixed, sintered in an oxygen-containing atmosphere, and pulverized to obtain lithium-ion battery cathode material matrix particles.

[0019] The M1 source is an Al source and / or a Mn source, and the M2 source is at least one of a Ti source, a Ba source, a Sr source, a Mg source, a Cr source, a Zr source, a Y source, a Ta source, a Zn source, a V source, a W source, a B source, and a Cu source.

[0020] This invention provides a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery is the lithium-ion battery positive electrode material described in the above technical solution or the lithium-ion battery positive electrode material prepared by the preparation method described in the above technical solution.

[0021] Compared with existing technologies, this invention provides a lithium-ion battery cathode material, its preparation method, and its application. The lithium-ion battery cathode material provided by this invention comprises lithium-ion battery cathode material matrix particles and a coating layer covering the surface of the lithium-ion battery cathode material matrix particles; the coating layer comprises fluorides and oxides converted from the fluorides; the fluorides are one or more selected from FeF3, CrF3, VF4, TmF3, NdF3, PrF3, CeF3, SnF4, and DyF3; the mass percentage of the fluorides in the coating layer is ≥20 wt%; the total content of the fluorides and oxides in the lithium-ion battery cathode material, calculated as metal elements, is 1500–3500 ppm. This invention uses fluorides as the main coating material for lithium-ion battery cathode materials, and by controlling the ratio of fluorides to oxides (F / O) in the coating layer within a suitable range and selecting an appropriate coating amount, the material exhibits excellent electrochemical performance. The coating material for lithium-ion battery cathodes provided by this invention possesses excellent lubrication and film-forming properties, enabling the cathode material to exhibit good voltage resistance and superior voltage resistance during subsequent electrode fabrication. Furthermore, this coating material readily transforms into an oxide under oxygen conditions, mitigating the effects of unstable Ni in the cathode material during long-term high-temperature storage or cycling. 4+ It is easy to convert to a lower valence state. With the release of active oxygen, the active oxygen can react with the coating material, thereby reducing the reaction between active oxygen and electrolyte, and thus reducing gas generation and the deterioration of SEI film in the battery system, showing better long-term cycle performance and safety performance. In addition, the coating amount of the cathode material is moderate and will not have a significant adverse effect on the capacity of the cathode material. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a SEM image of the cathode material of Example 1 provided by the present invention;

[0024] Figure 2 This is a SEM image of the cathode material of Comparative Example 1 provided by the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The present invention provides a lithium-ion battery cathode material, comprising lithium-ion battery cathode material matrix particles and a coating layer covering the surface of the lithium-ion battery cathode material matrix particles.

[0027] In the cathode material provided by this invention, the preferred chemical formula of the lithium-ion battery cathode material matrix particles is Li. x Ni y Co z M1 m M2 n O2; wherein M1 is Al and / or Mn, M2 is at least one of Ti, Ba, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, B and Cu, preferably Zr; x, y, z and m are all > 0, n ≥ 0, and the values ​​of x, y, z, m and n satisfy the charge balance of the general chemical formula. In the preferred technical solution provided by the present invention, 1 ≤ x ≤ 1.1, 0.5 ≤ y < 1, 0 < z ≤ 0.3, 0 < m ≤ 0.3, 0.002 ≤ n ≤ 0.005; more preferably 1 < x ≤ 1.02, 0.6 ≤ y ≤ 0.9, 0.05 ≤ z ≤ 0.12, 0.05 ≤ m ≤ 0.3, 0.002 ≤ n ≤ 0.0035. In the embodiments provided by the present invention, the chemical formula of the lithium-ion battery cathode material matrix particles can specifically be Li 1.01 Ni 0.798 Co 0.1 Mn 0.1 Zr 0.0022 O2, Li 1.01 Ni 0.897 Co 0.05 Al 0.05 Zr 0.0033 O2, Li 1.01 Ni 0.898 Co 0.05 Mn 0.05 Zr 0.0022 O2, Li 1.02 Ni 0.648 Co 0.05 Mn 0.3 Zr 0.0022 O2 or Li 1.01 Ni 0.648 Co 0.05 Mn 0.3 Zr 0.0022 O.

[0028] In the cathode material provided by the present invention, the median particle size of the lithium-ion battery cathode material matrix particles is preferably ≤20μm, more preferably 1~15μm, and specifically can be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or 15μm.

[0029] In the cathode material provided by this invention, the coating layer comprises fluorides and oxides converted from the fluorides. The fluorides are one or more selected from FeF3, CrF3, VF4, TmF3, NdF3, PrF3, CeF3, SnF4, and DyF3. The mass percentage of the fluorides in the coating layer is ≥20 wt%, preferably 30–80 wt%, specifically 30 wt%, 35 wt%, 40 wt%, 41.5 wt%, 45 wt%, 50 wt%, 50.1 wt%, 50.5 wt%, 55 wt%, 55.5 wt%, 60 wt%, 60.5 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%.

[0030] In the cathode material provided by the present invention, the total content of the fluorides and oxides, calculated as metal elements, in the lithium-ion battery cathode material is 1500-3500 ppm, specifically 1500 ppm, 1600 ppm, 1700 ppm, 1750 ppm, 1800 ppm, 1900 ppm, 1970 ppm, 2000 ppm, 2100 ppm, 2150 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 2980 ppm, 3000 ppm, 3050 ppm, 3100 ppm, 3200 ppm, 3300 ppm, 3400 ppm, or 3500 ppm. In this invention, taking NdF3 as an example of the fluoride, the total content of the fluoride and oxide in the lithium-ion battery cathode material, calculated as metal elements, is the content of Nd element in the cathode material.

[0031] In the cathode material provided by this invention, the coating layer is formed by sintering fluoride coated onto the surface of the cathode material matrix particles in the presence of an inhibitor of conversion. The inhibitor of conversion is used to regulate the degree of oxidation of the fluoride during the sintering process. The lower the degree of oxidation, the higher the proportion of fluoride and the lower the proportion of oxides in the coating layer formed after sintering, and vice versa. In this invention, the inhibitor of conversion is preferably one or more of SnCl2, H2C2O4, KBH4, Na2SO3, NaBH4, NH4F, and LiAlH4. The sintering is preferably carried out under oxygen-free or oxygen-containing conditions, specifically in a pure oxygen atmosphere or an air atmosphere. The sintering temperature is preferably 200–500°C, and the sintering time is preferably 3–10 h.

[0032] In the positive electrode material provided by the present invention, the inhibitor of conversion is one or more of SnCl2, H2C2O4, KBH4, Na2SO3, NaBH4, NH4F and LiAlH4.

[0033] In the cathode material provided by this invention, the preferred mass ratio of the lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor is 100:(0.25-0.5):(0.03-0.12); specifically, the mass ratio of the lithium-ion battery cathode material matrix particles to fluoride can be 100:0.25, 100:0.26, 100:0.27, 100:0.28, 100:0.29, 100:0.3, 100:0.31, 100:0.32, 100:0.33, 100:0.34, 100:0.35, 100:0.36, 100:0.37, or 100:0.3. 8, 100:0.39, 100:0.4, 100:0.41, 100:0.42, 100:0.43, 100:0.44, 100:0.45, 100:0.46, 100:0.47, 100:0.48, 100:0.49 or 100:0.5; the specific mass ratio of the lithium-ion battery cathode material matrix particles to the conversion inhibitor can be 100:0.03, 100:0.04, 100:0.05, 100:0.06, 100:0.07, 100:0.08, 100:0.09, 100:0.1, 100:0.11 or 100:0.12.

[0034] In the cathode material provided by this invention, the sintering is preferably carried out under oxygen-free or oxygen-containing conditions, specifically in a pure oxygen atmosphere or an air atmosphere; the sintering temperature is preferably 200–500°C, specifically 200°C, 230°C, 250°C, 270°C, 300°C, 320°C, 350°C, 370°C, 400°C, 420°C, 450°C, 470°C, or 500°C; the sintering time is preferably 3–10 hours, specifically 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, or 10 hours.

[0035] In the cathode material provided by the present invention, the cathode material is preferably crushed after sintering, that is, the cathode material provided is a particulate material.

[0036] The present invention also provides a method for preparing the lithium-ion battery cathode material described in the above technical solution, comprising the following steps:

[0037] The lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor are mixed and sintered to obtain the lithium-ion battery cathode material.

[0038] In the preparation method provided by this invention, lithium-ion battery cathode material matrix particles are first prepared; the chemical composition and particle size of the lithium-ion battery cathode material matrix particles have been described above and will not be repeated here; the lithium-ion battery cathode material matrix particles are preferably prepared according to the following steps:

[0039] The lithium source, nickel source, cobalt source, M1 source and M2 source are mixed, sintered in an oxygen-containing atmosphere, and pulverized to obtain lithium-ion battery cathode material matrix particles.

[0040] The M1 source is an Al source and / or a Mn source, and the M2 source is at least one of a Ti source, a Ba source, a Sr source, a Mg source, a Cr source, a Zr source, a Y source, a Ta source, a Zn source, a V source, a W source, a B source, and a Cu source.

[0041] In the above-mentioned cathode material matrix particle preparation steps provided by the present invention, the lithium source is preferably lithium hydroxide; the nickel source, cobalt source, and M1 source can be derived from the same raw material or from different raw materials; more specifically, when the M source is a Mn source, the nickel source, cobalt source, and Mn source are preferably nickel-cobalt-manganese hydroxides, such as Ni 0.8 Co 0.1 Mn 0.1 (OH)2, Ni 0.9 Co 0.05 Mn 0.05 (OH)2, Ni 0.65 Co 0.05 Mn0.3 (OH)2; when the M source is an Al source, the nickel source, cobalt source, and Al source are preferably nickel-cobalt-aluminum hydroxides, such as Ni 0.9 Co 0.05 Al 0.05 (OH)2; the M2 source is preferably an oxide of M2.

[0042] In the above-mentioned cathode material matrix particle preparation steps provided by the present invention, the preferred ratio of the molar amount of the lithium source to the total molar amount of the nickel source, cobalt source and M1 source is (1~1.1):1, specifically 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.1:1; the amount of the M2 source is determined according to the M2 content in the cathode material matrix particles to be prepared.

[0043] In the above-mentioned preparation steps of the positive electrode material matrix particles provided by the present invention, the oxygen-containing atmosphere is preferably a pure oxygen atmosphere; the sintering temperature under the oxygen-containing atmosphere is preferably 700-1000℃, specifically 700℃, 720℃, 750℃, 770℃, 800℃, 820℃, 850℃, 870℃, 900℃, 920℃, 950℃, 970℃ or 1000℃; the sintering time under the oxygen-containing atmosphere is preferably 7-15h, specifically 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h or 15h.

[0044] In the above-mentioned positive electrode material matrix particle preparation steps provided by the present invention, after pulverization, it is preferable to further perform sieving, washing and drying.

[0045] In the preparation method provided by this invention, the selection of the types of fluoride and conversion inhibitor has been described above and will not be repeated here.

[0046] In the preparation method provided by this invention, the preferred mass ratio of the lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor is 100:(0.25-0.5):(0.03-0.12); specifically, the mass ratio of the lithium-ion battery cathode material matrix particles to fluoride can be 100:0.25, 100:0.26, 100:0.27, 100:0.28, 100:0.29, 100:0.3, 100:0.31, 100:0.32, 100:0.33, 100:0.34, 100:0.35, 100:0.36, 100:0.37, or 100:0.3. 8, 100:0.39, 100:0.4, 100:0.41, 100:0.42, 100:0.43, 100:0.44, 100:0.45, 100:0.46, 100:0.47, 100:0.48, 100:0.49 or 100:0.5; the specific mass ratio of the lithium-ion battery cathode material matrix particles to the conversion inhibitor can be 100:0.03, 100:0.04, 100:0.05, 100:0.06, 100:0.07, 100:0.08, 100:0.09, 100:0.1, 100:0.11 or 100:0.12.

[0047] In the preparation method provided by this invention, the lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor are preferably mixed in a high-speed mixer or ball mill jar; wherein, the rotational speed of the high-speed mixer is preferably 500-1000 r / s, specifically 500 r / s, 550 r / s, 600 r / s, 650 r / s, 700 r / s, 750 r / s, 800 r / s, 850 r / s, 900 r / s, 950 r / s, or 1000 r / s; the processing time in the high-speed mixer is preferably 0.5-5 hours, specifically... The processing time is 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h; the rotational speed of the ball mill jar is preferably 100-500 r / s, specifically 100 r / s, 150 r / s, 200 r / s, 250 r / s, 300 r / s, 350 r / s, 400 r / s, 450 r / s, or 500 r / s; the processing time in the ball mill jar is preferably 1-5h, specifically 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h.

[0048] In the preparation method provided by the present invention, the sintering is preferably carried out under oxygen-free or oxygen-containing conditions, specifically in a pure oxygen atmosphere or an air atmosphere; the sintering temperature is preferably 200-500℃, specifically 200℃, 230℃, 250℃, 270℃, 300℃, 320℃, 350℃, 370℃, 400℃, 420℃, 450℃, 470℃ or 500℃; the sintering time is preferably 3-10h, specifically 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h.

[0049] In the preparation method provided by the present invention, after sintering, it is preferable to further pulverize and sieve to obtain a powdered lithium-ion battery cathode material.

[0050] The present invention also provides a lithium-ion battery, wherein the positive electrode material of the lithium-ion battery is the lithium-ion battery positive electrode material described in the above technical solution or the lithium-ion battery positive electrode material prepared by the preparation method described in the above technical solution.

[0051] The technical solution provided by this invention uses fluoride as the main coating material for the positive electrode of lithium-ion batteries. By adding a certain amount of conversion inhibitor during the coating process, the degree of conversion of fluoride to oxide can be controlled, thereby controlling the F / O ratio of the coating layer on the surface of the positive electrode material. Furthermore, by determining a suitable coating amount, the positive electrode material exhibits excellent electrochemical performance. More specifically, the technical solution provided by this invention has the following advantages:

[0052] 1) The coating material has excellent lubrication and film-forming properties, which can give the positive electrode material good voltage resistance and excellent voltage resistance when it is subsequently made into an electrode sheet;

[0053] 2) The coating material also has the characteristic of easily transforming into oxides under oxygen conditions. During long-term high-temperature storage or cycling, due to the unstable Ni in the cathode material... 4+ It is easy to convert to a lower valence state. With the release of active oxygen, the active oxygen can react with the coating material, thereby reducing the reaction between active oxygen and electrolyte, thus reducing gas generation and deterioration of SEI film in battery system, and exhibiting better long-term cycle performance and safety performance.

[0054] 3) By changing the type and / or amount of coating materials (fluorides and conversion inhibitors), as well as the mixing and sintering process and / or process conditions, it is possible to precisely control the degree of fluoride conversion and the amount of material coating, so as to ensure that the F / O ratio and coating amount of the final lithium-ion battery cathode material surface coating layer meet the expected requirements.

[0055] 4) The process is simple, easy to operate, and low in cost, making it suitable for industrial production.

[0056] For clarity, the following examples will be used to provide a detailed description.

[0057] Example 1

[0058] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0059] (1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.8 Co 0.1 Mn 0.1 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the Zr content in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 800℃ in an oxygen atmosphere for 10 hours. After sintering, the mixture was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix particles Li with a median particle size of 10.0 μm. 1.01 Ni 0.798 Co 0.1 Mn 0.1 Zr 0.0022 O2;

[0060] (2) The above-mentioned cathode material matrix particles, NdF3 and NaBH4 are mixed in a high-speed mixer; wherein, the amount of NdF3 is 0.3wt% of the cathode material matrix particles, the amount of NaBH4 is 0.05wt% of the cathode material matrix particles, the mixing speed is 800r / s, and the mixing time is 2h; after uniform mixing, it is placed in a box furnace and sintered in an oxygen atmosphere at 400℃ for 10h, pulverized, and sieved to obtain a lithium-ion battery cathode material with a coating layer.

[0061] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of NdF3 and Nd oxide, of which NdF3 accounts for 41.5% of the total mass of the coating layer.

[0062] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Nd content in the finished cathode material was determined to be 1970 ppm.

[0063] Example 2

[0064] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0065] (1) Ni 0.90 Co 0.05 Al 0.05 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.9 Co 0.05 Al 0.05 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the content of Zr in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 900℃ in air atmosphere for 10 hours. After sintering, it was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix particles Li with a median particle size of 10.0 μm. 1.01 Ni 0.897 Co 0.05 Al 0.05 Zr 0.0033 O2;

[0066] (2) The above-mentioned cathode material matrix particles, DyF3 and NH4F were placed in a ball mill jar and ball milled; wherein, the amount of DyF3 was 0.5wt% of the cathode material matrix particles, the amount of NH4F was 0.05wt% of the cathode material matrix particles, the ball milling speed was 300r / s, and the ball milling time was 2h; after ball milling, the material was placed in a box furnace and sintered in an oxygen atmosphere at 350℃ for 10h, then crushed and sieved to obtain the lithium-ion battery cathode material.

[0067] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of DyF3 and Dy oxide, of which DyF3 accounts for 50.1% of the total mass of the coating layer.

[0068] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Dy element content in the finished cathode material was determined to be 3050 ppm.

[0069] Example 3

[0070] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0071] (1) Ni 0.9 Co 0.05 Mn 0.05 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.9 Co 0.05 Mn 0.05The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the content of Zr in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 900℃ in air atmosphere for 10 hours. After sintering, it was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix particles Li with a median particle size of 10.0 μm. 1.01 Ni 0.898 Co 0.05 Mn 0.05 Zr 0.0022 O2;

[0072] (2) The above-mentioned cathode material matrix particles, PrF3 and NaBH4 were placed in a ball mill jar and ball milled; wherein, the amount of PrF3 was 0.5wt% of the cathode material matrix particles, the amount of NaBH4 was 0.04wt% of the cathode material matrix particles, the ball milling speed was 300r / s, and the ball milling time was 2h; after ball milling, the material was placed in a box furnace and sintered in an oxygen atmosphere at 350℃ for 10h, then crushed and sieved to obtain the lithium-ion battery cathode material.

[0073] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of PrF3 and Pr oxide, of which PrF3 accounts for 55.5% of the total mass of the coating layer.

[0074] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Pr content in the finished cathode material was determined to be 2980 ppm.

[0075] Example 4

[0076] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0077] (1) Ni 0.65 Co 0.05 Mn 0.3 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.65 Co 0.05 Mn 0.3 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the Zr content in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 880℃ in an oxygen atmosphere for 10 hours. After sintering, the mixture was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix particles Li with a median particle size of 3.5 μm. 1.02 Ni 0.648 Co 0.05 Mn0.3 Zr 0.0022 O2;

[0078] (2) The above-mentioned cathode material matrix particles, SnF4 and LiAlH4 are mixed in a high-speed mixer; wherein, the amount of SnF4 is 0.3wt% of the cathode material matrix particles, the amount of LiAlH4 is 0.07wt% of the cathode material matrix particles, the mixing speed is 800r / s, and the mixing time is 2h; after uniform mixing, it is placed in a box furnace and sintered in an air atmosphere at 300℃ for 10h, pulverized, and sieved to obtain lithium-ion battery cathode material.

[0079] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of SnF4 and Sn oxide, of which SnF4 accounts for 60.5% of the total mass of the coating layer.

[0080] The above-mentioned lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Sn element content in the finished cathode material was determined to be 2150 ppm.

[0081] Example 5

[0082] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0083] (1) Ni 0.65 Co 0.05 Mn 0.3 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed evenly in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.65 Co 0.05 Mn 0.3 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the Zr content in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 880℃ in an oxygen atmosphere for 10 hours. After sintering, the mixture was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix particles Li with a median particle size of 3.5 μm. 1.01 Ni 0.648 Co 0.05 Mn 0.3 Zr 0.0022 O2;

[0084] (2) The above-mentioned cathode material matrix particles, CeF4 and LiAlH4 are mixed in a high-speed mixer; wherein, the amount of CeF4 is 0.3wt% of the cathode material matrix particles, the amount of LiAlH4 is 0.07wt% of the cathode material matrix particles, the mixing speed is 800r / s, and the mixing time is 2h; after uniform mixing, it is placed in a box furnace and sintered in an air atmosphere at 350℃ for 10h, pulverized, and sieved to obtain lithium-ion battery cathode material.

[0085] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of CeF4 and Ce oxide, of which CeF4 accounts for 50.5% of the total coating layer mass.

[0086] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Ce element content in the finished cathode material was determined to be 1750 ppm.

[0087] Comparative Example 1

[0088] A method for preparing a lithium-ion battery cathode material includes the following steps:

[0089] (1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.8 Co 0.1 Mn 0.1 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the Zr content in the cathode material matrix particles to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 800℃ in an oxygen atmosphere for 10 hours. After sintering, it was mechanically ground, sieved, washed with water, and dried to obtain a cathode material matrix Li with a median particle size of 10.0 μm. 1.01 Ni 0.798 Co 0.1 Mn 0.1 Zr 0.0022 O2;

[0090] (2) The above-mentioned cathode material matrix particles and NdF3 are mixed in a high-speed mixer; wherein, the amount of NdF3 is 0.3wt% of the cathode material matrix particles, the mixing speed is 800r / s, and the mixing time is 2h; after uniform mixing, it is placed in a box furnace and sintered in an oxygen atmosphere at 400℃ for 10h, then crushed and sieved to obtain lithium-ion battery cathode material.

[0091] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of NdF3 and Nd oxide, of which NdF3 accounts for 15.5% of the total mass of the coating layer.

[0092] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Nd content in the finished cathode material was determined to be 1860 ppm.

[0093] Comparative Example 2

[0094] (1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂, LiOH·H₂O, and ZrO₂ are mixed in a high-speed mixer; wherein, LiOH·H₂O and Ni 0.8 Co 0.1 Mn 0.1 The molar ratio of (OH)₂ was 1.04:1, and the amount of ZrO₂ was determined based on the content of Zr in the cathode material matrix powder to be prepared. After uniform mixing, the mixture was placed in a box furnace and sintered at 800℃ in an oxygen atmosphere for 10 hours. After sintering, it was mechanically ground, sieved, washed with water, and dried to obtain cathode material matrix powder Li with a median particle size of 10.0 μm. 1.01 Ni 0.798 Co 0.1 Mn 0.1 Zr 0.0022 O2;

[0095] (2) The above-mentioned cathode material matrix powder, NdF3 and NaBH4 are mixed in a high-speed mixer; wherein, the amount of NdF3 is 0.6wt% of the cathode material matrix powder, the amount of NaBH4 is 0.15wt% of the cathode material matrix powder, the mixing speed is 800r / s, and the mixing time is 2h; after uniform mixing, it is placed in a box furnace and sintered in an oxygen atmosphere at 400℃ for 10h, pulverized, and sieved to obtain the lithium-ion battery cathode material.

[0096] The coating layer of the above-mentioned lithium-ion battery cathode material was detected by X-ray photoelectron spectroscopy (XPS), and it was determined that the coating layer is mainly composed of NdF3 and Nd oxide, of which NdF3 accounts for 43.1% of the total mass of the coating layer.

[0097] The lithium-ion battery cathode material was tested using an inductively coupled plasma atomic emission spectrometer (ICP), and the Nd content in the finished cathode material was determined to be 3750 ppm.

[0098] Structural characterization and electrical performance testing

[0099] 1) Structural characterization:

[0100] The lithium-ion battery cathode materials prepared in Example 1 and Comparative Example 1 were observed by scanning electron microscopy (SEM), and the results are as follows: Figure 1 and Figure 2 As shown, Figure 1 This is a SEM image of the cathode material of Example 1 provided by the present invention. Figure 2 This is a SEM image of the cathode material of Comparative Example 1 provided by the present invention.

[0101] By comparison Figure 1 and Figure 2 As can be seen, there is no significant difference between the SEM images of Example 1 and Comparative Example 1, and there are fine coating particles on the surface of the positive electrode material.

[0102] 2) Electrical performance testing:

[0103] The coin cell and full-capacity performance of the lithium-ion battery cathode materials prepared in Examples 1-5 and Comparative Example 1 were tested. Specifically, the lithium-ion battery cathode materials were fabricated into coin cells with lithium metal sheets as the negative electrode, and their initial charge-discharge capacity at 0.2C was tested at a voltage of 3.0–4.25V. The lithium-ion battery cathode materials were also fabricated into pouch cells with graphite as the negative electrode, and their volume change rate at 70℃ for 28 days and cycle retention rate at 300 cyc@45℃ were tested. The results are shown in Table 1.

[0104] Table 1. Test results of coin cell performance and overall electrical performance of lithium-ion battery cathode materials.

[0105]

[0106] As can be seen from Example 1 and Comparative Example 1, without the addition of an inhibitor of conversion, the long-term high-temperature storage and cycling performance of the cathode material are poor, indicating that a low fluoride content in the coating layer (i.e., a low F / O ratio) will have an adverse effect on the long-term high-temperature storage and cycling performance of the cathode material. As can be seen from Example 1 and Comparative Example 2, if the amount of fluoride and the inhibitor of conversion is high, the long-term high-temperature storage and long-term cycling performance of the cathode material will be improved to a certain extent, but the charge and discharge capacity will be significantly reduced, indicating that an excessively thick coating layer will seriously affect the capacity of the cathode material. The cathode materials provided in Examples 1 to 5 have suitable coating amounts and coating layer F / O ratios, which not only have a small impact on battery capacity, but also have good long-term high-temperature storage and long-term cycling performance.

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A lithium-ion battery cathode material, comprising lithium-ion battery cathode material matrix particles and a coating layer covering the surface of the lithium-ion battery cathode material matrix particles; The general chemical formula of the lithium-ion battery cathode material matrix particles is Li x Ni y Co z M1 m M2 n O2, where, M1 is Al and / or Mn, and M2 is at least one of Ti, Ba, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, B, and Cu; 1≤x≤1.1, 0.5≤y<1, 0<z≤0.3, 0<m≤0.3, 0.002≤n≤0.005, and the values ​​of x, y, z, m, and n satisfy the charge balance of the general chemical formula; The coating layer comprises fluorides and oxides converted from the fluorides; the fluorides are one or more of NdF3, PrF3, CeF3, SnF4, and DyF3; the fluorides account for 40-65 wt% of the mass of the coating layer; and the total content of the fluorides and oxides in the lithium-ion battery cathode material, calculated as metal elements, is 1500-3500 ppm.

2. A method for preparing the lithium-ion battery cathode material according to claim 1, comprising the following steps: The lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor are mixed and sintered to obtain the lithium-ion battery cathode material.

3. The preparation method according to claim 2, characterized in that, The inhibitory conversion agent is one or more of SnCl2, H2C2O4, KBH4, Na2SO3, NaBH4, NH4F and LiAlH4.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the lithium-ion battery cathode material matrix particles, fluoride, and conversion inhibitor is 100:(0.25~0.5):(0.03~0.12).

5. The preparation method according to claim 2, characterized in that, The sintering is carried out under oxygen-free or oxygen-containing conditions.

6. The preparation method according to claim 2, characterized in that, The sintering temperature is 200~500℃; the sintering time is 3~10h.

7. The preparation method according to claim 2, characterized in that, The lithium-ion battery cathode material matrix particles are prepared according to the following steps: The lithium source, nickel source, cobalt source, M1 source and M2 source are mixed, sintered in an oxygen-containing atmosphere, and pulverized to obtain lithium-ion battery cathode material matrix particles. The M1 source is an Al source and / or a Mn source, and the M2 source is at least one of a Ti source, a Ba source, a Sr source, a Mg source, a Cr source, a Zr source, a Y source, a Ta source, a Zn source, a V source, a W source, a B source, and a Cu source.

8. A lithium-ion battery, characterized in that, The positive electrode material of the lithium-ion battery is the lithium-ion battery positive electrode material according to claim 1 or the lithium-ion battery positive electrode material prepared by the preparation method according to any one of claims 2 to 7.

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