A double-coated high-nickel lithium ion positive electrode material, a preparation method and application thereof

Abstract

The application relates to the field of lithium ion batteries, in particular to a double-coated high-nickel lithium ion positive electrode material and a preparation method and application thereof, the double-coated high-nickel lithium ion positive electrode material comprising a positive electrode material matrix, a first coating layer coated on the surface of the positive electrode material matrix and a second coating layer coated on the surface of the first coating layer; wherein the first coating layer and the second coating layer are prepared by sequentially coating the positive electrode material matrix with a metal oxide and a boron-containing compound. The lithium ion battery high-nickel positive electrode material is stable in structure and interface, is relatively stable in air, is convenient for large-scale production, has less gas generation after being made into a battery, and is high in safety.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to a double-coated high-nickel lithium-ion cathode material, its preparation method and application, and a low-gas-producing high-nickel lithium-ion battery made using the double-coated high-nickel lithium-ion cathode material. Background Technology

[0002] As consumers demand increasingly longer driving ranges for new energy vehicles, high-nickel ternary lithium batteries are gaining popularity. In 2022, the installed capacity of high-nickel ternary lithium batteries gradually surpassed that of low-nickel ternary lithium batteries. High-nickel lithium-ion batteries (Ni molar fraction ≥ 0.6) have become one of the important future development directions. On the one hand, current high-nickel cathode materials are mainly in the form of secondary spherical particles, which have a relatively higher capacity compared to single-crystal particles. However, due to the relatively low sintering temperature, gas generation is also relatively severe. On the other hand, high-nickel cathode materials, due to their high nickel content, are unstable in air, which also easily leads to relatively severe gas generation after battery fabrication.

[0003] Chinese patent CN112349905A discloses a dual-coating modified lithium-ion battery cathode material, comprising a cathode material substrate, a first coating layer coated on the surface of the substrate, and a second coating layer coated on the surface of the first coating layer. The first coating layer is a nanosheet-shaped fast ion conductor layer; the second coating layer is an Al compound layer. This patent uses a two-stage sintering process. In the coating process, the fast ion conductor coating method involves adding the cathode material substrate to water and stirring to form a uniform slurry A; adding tungsten ammonium salt, molybdenum ammonium salt, or vanadium ammonium salt to water and stirring to form a uniform solution B; adding solution B and citric acid solution to slurry A and stirring until uniform; heating the mixture to evaporate the water until a viscous gel appears; then drying and dehydrating the gel slurry to obtain a cathode material coated with a nanosheet-shaped fast ion conductor. This coating method is overly complex, requiring strict control of process parameters and heating to evaporate moisture, making it difficult to industrialize and requiring improvement in gas generation performance. Furthermore, the substrate material has a secondary spherical morphology.

[0004] Chinese patent CN111628158A discloses a double-coated cathode material, comprising a first coating layer and a second coating layer sequentially coated on the cathode material, wherein the cathode material comprises Li. a Ni x Co y Mn 1-x-yO2, where 0.3 < x < 0.9, 0.1 < y < 0.35, and 0.95 < a < 1.03. The first coating layer and the second coating layer are different. The first coating layer is an LATP layer or an LNTO layer, and the second coating layer is an LNTO layer or an LATP layer. This patented process can only be applied to high-nickel materials below the 9 series, and the coating material is a fast ion conductor. It adopts a two-time dry coating and two-sintering process. The matrix material also has a secondary spherical morphology. Although compared with single coating, this invention alleviates the problems of rapid capacity decay and excessive side reactions during cycling, the gas generation performance still needs to be improved.

[0005] Chinese Patent CN108807926A discloses a Co / B co-coated nickel cobalt manganese lithium ion cathode material and its preparation method. In the process of manufacturing the lithium ion cathode material of the present invention, an appropriate amount of F / W is incorporated, and a small amount of F- ions and W6+ ions are incorporated to improve the cycling performance and safety performance. Since the electronegativity of F ions is very strong, it can inhibit the overflow of O2- ions and stabilize the structural stability of the material, playing a role as a skeleton. W6+ ions can improve the high-temperature cycling performance of the material. In addition, during the secondary sintering of the present invention, Co / B double coating is carried out. The Co / B-coated cathode material at high voltage can effectively improve the cycling performance and electronic conductivity of the battery, reduce residual alkali, reduce gas swelling, and reduce the occurrence of side reactions when the cathode material contacts the electrolyte, but the gas generation performance still needs to be improved.

[0006] In addition, to solve the gas generation performance, most of the existing technologies adopt inorganic or organic solvent washing, and then a process of coating and low-temperature sintering after washing. The process is relatively simple, but the performance is also limited. Therefore, there are not many enterprises with high-nickel scale production, especially when the molar fraction of Ni ≥ 0.9 and the free lithium is relatively high, it is very difficult to produce products with excellent performance by the above simple process. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a double-coated high-nickel lithium ion cathode material, improve the stability of the cathode material, reduce the gas generation amount of high-nickel lithium ion batteries, and improve the safety performance of high-nickel lithium ion batteries.

[0008] The inventor of the present invention has found through research that for high-nickel cathode materials with a nickel molar fraction exceeding 0.8, a process of mixing wet and dry coating is adopted. After surface etching with strong acid in the wet process and then wet coating, and then combined with dry coating of a boron-containing fast ion conductor, the stability of the material can be significantly improved and the gas generation performance of the battery can be reduced. In addition, the sintering temperature after wet coating is relatively high, which can play a role in stabilizing the structure and interface, and the sintering temperature after dry coating is relatively low, which can play a role in inhibiting the side reactions between the material and the electrolyte.

[0009] To solve the above problems, the present invention proposes the following technical solutions:

[0010] This invention provides a double-coated high-nickel lithium-ion battery cathode material, which includes a cathode material matrix, a first coating layer coated on the surface of the cathode material matrix, and a second coating layer coated on the surface of the first coating layer;

[0011] The first coating layer and the second coating layer are prepared by sequentially coating the positive electrode material substrate with a metal oxide and a boron-containing compound.

[0012] In some embodiments of the present invention, the general chemical formula of the positive electrode material is Li. a Ni x Co y Mn z M b O2·cA·dB, where: 1.00≤a≤1.20, 0.00<b≤0.01, 0.00<c≤0.01, 0.00<d≤0.05, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, x+y+z=1; M is a doping element, wherein M is selected from one or more of Mg, Ti, Al, Zr, Ba and rare earth elements; A is the first coating layer, and B is the second coating layer.

[0013] In some embodiments of the present invention, in the above-mentioned double-coated high-nickel lithium-ion battery cathode material, 1.00≤a≤1.20, 0.001≤b≤0.01, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, 0.0005<c≤0.01, 0.001<d≤0.05, x+y+z=1; preferably, 1.02≤a≤1.20, 0.0015≤b≤0.005, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, 0.0005<c≤0.01, 0.001<d≤0.03, x+y+z=1.

[0014] Preferably, in the above-mentioned double-coated high-nickel lithium-ion battery cathode material, the rare earth element is selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or europium, with yttrium being the most preferred.

[0015] In some embodiments of the present invention, in the above-mentioned double-coated high-nickel lithium-ion battery cathode material, the first coating layer is a coating layer formed by wet coating of metal oxide; preferably, the metal oxide is selected from one or more of Al2O3, TiO2, ZrO2, MgO and rare earth element oxides.

[0016] In some embodiments of the present invention, in the above-mentioned double-coated high-nickel lithium-ion battery cathode material, the rare earth element oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, or europium oxide, preferably yttrium oxide.

[0017] In some embodiments of the present invention, in the above-mentioned double-coated high-nickel lithium-ion battery cathode material, the second coating layer is a coating layer formed by dry coating of a boron-containing compound; preferably, the boron-containing compound is selected from one or more of boric acid, lithium borate, lithium metaborate or lithium tetraborate.

[0018] In some embodiments of the present invention, the above-mentioned double-coated high-nickel lithium-ion battery cathode material has a morphology of primary particles or a small number of primary particles agglomerated.

[0019] In some embodiments of the present invention, the above-mentioned double-coated high-nickel lithium-ion battery cathode material contains, by weight of cathode material, a total free lithium content of <2000 ppm.

[0020] In some embodiments of the present invention, the specific surface area of ​​the above-mentioned double-coated high-nickel lithium-ion battery cathode material is 0.4-1.5 m². 2 / g; preferably, the average particle size of the cathode material is 2-5μm.

[0021] In some embodiments of the present invention, the wet coating of the above-mentioned dual-coated high-nickel lithium-ion battery cathode material includes the step of mixing a wet coating reagent with the cathode material matrix and then sintering it.

[0022] Preferably, the wet coating reagent includes metal oxides and water, and more preferably, it also includes a strong acid.

[0023] The present invention also provides a method for preparing the above-mentioned double-coated high-nickel lithium-ion battery cathode material, comprising the following steps:

[0024] (1) Mix the lithium source compound, the cathode material precursor and the M source compound to obtain a mixture;

[0025] (2) The mixture from step (1) is subjected to a first calcination to obtain the positive electrode material matrix;

[0026] (3) The cathode material substrate obtained in step (2) is wet coated to obtain the cathode material coated with the first coating layer;

[0027] (4) The cathode material coated with the first coating layer obtained in step (3) is dry coated to obtain a double-coated high-nickel lithium-ion battery cathode material.

[0028] In some embodiments of the present invention, in the above preparation method, the elemental molar ratio of the lithium source compound, the cathode material precursor and the M source compound is Li:(Ni+Co+Mn):M is (1.0~1.2):1.0:(0.00~0.01).

[0029] In some embodiments of the present invention, the wet coating method described above includes a step of mixing a positive electrode material matrix, water, strong acid and metal oxide and then performing a second sintering.

[0030] Preferably, the mass ratio of the positive electrode material matrix to the metal oxide is 1.0:(0.0005~0.005), more preferably the mass ratio of the positive electrode material matrix to water is 1:(1.0~2.0), and more preferably the mass ratio of the positive electrode material matrix to the strong acid is 1:(0.001~0.01).

[0031] More preferably, the temperature of the second sintering is 600-800℃, and the sintering time is preferably 6-20h; even more preferably, the mixing process further includes filtration and drying steps.

[0032] In some embodiments of the present invention, the dry coating method described above includes a step of mixing the cathode material coated with the first coating layer obtained in step (3) with a boron-containing compound and then performing a third sintering.

[0033] Preferably, the mass ratio of the positive electrode material to the boron-containing compound coated by the first coating layer is 1.0:(0.002~0.02);

[0034] More preferably, the temperature of the third sintering is 250-450℃, and the preferred sintering time is 3-15h.

[0035] The present invention also provides a low-gas-producing high-nickel lithium-ion battery, wherein the low-gas-producing high-nickel lithium-ion battery contains the above-mentioned double-coated high-nickel lithium-ion battery cathode material or the double-coated high-nickel lithium-ion battery cathode material prepared by the above-mentioned preparation method.

[0036] In some embodiments of the present invention, the low-gas-producing high-nickel lithium-ion battery has an initial discharge capacity of 190-210 mAh / g under 4.2V, 1C charge-discharge conditions.

[0037] In some embodiments of the present invention, the low-gas-producing high-nickel lithium-ion battery, when stored at 4.25V and 70°C for 30 days, has a battery thickness expansion rate of less than or equal to 32%.

[0038] The present invention also provides the application of the above-mentioned double-coated high-nickel lithium-ion battery cathode material or the double-coated high-nickel lithium-ion battery cathode material prepared by the above-mentioned preparation method or the above-mentioned low-gas-producing high-nickel lithium-ion battery in digital products, electric vehicles or energy storage fields.

[0039] The beneficial effects of this invention include:

[0040] The high-nickel cathode material for lithium-ion batteries of this invention has a stable structure and interface, is relatively stable in air, facilitates large-scale production, produces less gas, and has high safety. The high-nickel cathode material for lithium-ion batteries of this invention has the morphology of primary particles and a small amount of secondary particles agglomerated from primary particles, has high specific capacity, and excellent cycle performance. The high-nickel cathode material for lithium-ion batteries of this invention has a low cobalt content, which greatly reduces the cost of raw materials. Attached Figure Description

[0041] Figure 1 The image shown is a scanning electron microscope (SEM) image of the cathode material prepared in Example 1 of this invention, with a magnification of 3000x. Detailed Implementation

[0042] In this invention, unless otherwise specified in the specific context, the numerical ranges listed herein include upper and lower limits, and "above" and "below" include endpoint values ​​and all integers and fractions within that range, not limited to the specific values ​​listed when the range is defined. The term "and / or" as used herein is inclusive; for example, "A; and / or B" means only A, or only B, or both A and B.

[0043] Because high-nickel lithium-ion cathode materials have a high nickel content, they are relatively unstable in air. Batteries made with high-nickel lithium-ion cathode materials produce a lot of gas, posing a significant safety hazard and limiting the large-scale application of high-nickel lithium-ion cathode materials. This invention provides a double-coated high-nickel lithium-ion battery cathode material and a low-gas-producing high-nickel lithium-ion secondary battery made with this cathode material.

[0044] In a first aspect, in a specific embodiment of the present invention, the present invention provides a double-coated high-nickel lithium-ion battery cathode material, comprising a cathode material substrate, a first coating layer coated on the surface of the cathode material substrate, and a second coating layer coated on the surface of the first coating layer;

[0045] The dual-coated high-nickel lithium-ion battery cathode material is prepared by sequentially coating the cathode material substrate with wet coating and dry coating.

[0046] In some embodiments of the present invention, the general chemical formula of the dual-coated high-nickel lithium-ion battery cathode material is: Li a Ni x Co y Mn z Mb O2·cA·dB, where: 1.00≤a≤1.20, 0.00<b≤0.01, 0.00<c≤0.01, 0.00<d≤0.05, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, x+y+z=1; M is a doping element, wherein M is selected from one or more of Mg, Ti, Al, Zr, Ba and rare earth elements; A is the first coating layer, and B is the second coating layer.

[0047] In some embodiments of the present invention, the general chemical formula of the dual-coated high-nickel lithium-ion battery cathode material is: Li a Ni x Co y Mn z M b O2·cA·dB, where: 1.00≤a≤1.20, 0.001≤b≤0.01, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, 0.0005<c≤0.01, 0.001<d≤0.05, x+y+z=1, and M is a dopant element selected from Mg, Ti, Al, Zr, Ba, and rare earth elements. One or more; A is the first coating layer, and B is the second coating layer; preferably, 1.02≤a≤1.20, more preferably 1.10≤a≤1.20; more preferably, 0.83≤x≤0.92, more preferably 0.03≤y≤0.07, more preferably 0.03≤z≤0.1, even more preferably 0.0015≤b≤0.005, and even more preferably 0.002≤b≤0.003.

[0048] The following describes the types of elements, compounds, and contents of the coating layer in the cathode material of this invention.

[0049] The inventors discovered that in the chemical formula of the cathode material of this invention, the doping element is selected from one or more of Mg, Ti, Al, Zr, Ba, and rare earth elements. The rare earth element is selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or europium. Selecting a chemical element similar to the matrix element to replace some of the vacancies in the matrix element can stabilize the material's framework structure.

[0050] In some embodiments of the present invention, the first coating layer is a coating layer formed of a metal oxide, wherein the metal oxide is selected from one or more of Al2O3, TiO2, ZrO2, MgO, and rare earth element oxides; wherein the rare earth element oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, or europium oxide. Selecting a chemical element similar to the matrix element for a shallow coating can stabilize the shallow interface and suppress side reactions with the electrolyte.

[0051] In some preferred embodiments of the present invention, the second coating layer is a coating layer formed of a boron-containing compound. Preferably, the boron-containing compound is selected from one or more of boric acid, lithium borate, lithium metaborate or lithium tetraborate.

[0052] In some embodiments of the present invention, in the above chemical formula, 0.0005 < c ≤ 0.01, 0.001 < d ≤ 0.03, the coating layer is too thick, which affects the capacity. Preferably, 0.00075 ≤ c ≤ 0.003, more preferably 0.002 ≤ c ≤ 0.003, even more preferably 0.002 < d ≤ 0.01, and even more preferably 0.0025 ≤ d ≤ 0.01.

[0053] In some embodiments of the present invention, the cathode material powder, under a scanning electron microscope (SEM), comprises primary particles and a small amount of secondary particles agglomerated from the primary particles.

[0054] The primary particle morphology of the cathode material described in this invention refers to the morphology of the cathode material as primary particles and secondary particles formed by the aggregation of a small number of primary particles.

[0055] It should be noted that "a small number of secondary particles formed by the agglomeration of primary particles" refers to the fact that the percentage of secondary particles formed by the agglomeration of primary particles in the cathode material is less than 10%.

[0056] The single crystal or near-single crystal mentioned in this invention refers to the cathode material having primary particle morphology characteristics.

[0057] In some embodiments of the present invention, the cathode material contains less than 2000 ppm of total free lithium, based on the mass of the cathode material.

[0058] In some embodiments of the present invention, the specific surface area of ​​the positive electrode material is 0.4-1.5 m². 2 / g; preferably, the average particle size of the cathode material is 2-5μm.

[0059] Secondly, the present invention also provides a method for preparing the above-mentioned double-coated high-nickel lithium-ion battery cathode material, comprising the following steps:

[0060] (1) The lithium source compound, the cathode material precursor and the M source compound are mixed to obtain a mixture;

[0061] (2) The mixture from step (1) is subjected to a first sintering to obtain the positive electrode material matrix;

[0062] (3) The cathode material substrate obtained in step (2) is wet coated to obtain the cathode material coated with the first coating layer;

[0063] (4) The cathode material coated with the first coating layer obtained in step (3) is dry coated to obtain a double-coated high-nickel lithium-ion battery cathode material.

[0064] It should be understood that the aforementioned cathode material precursors include one or more of nickel-cobalt-manganese precursors, nickel-cobalt precursors, or nickel-manganese precursors. For example, nickel-cobalt-manganese precursors are one or more of hydroxides, carboxyl oxides, or oxides containing nickel, cobalt, and manganese elements, with a particle size of 3μm-20μm.

[0065] In some embodiments of the present invention, the lithium source compound, the cathode material precursor, and the M source compound are in the elemental molar ratio of Li:(Ni+Co+Mn):M as (1.0~1.2):1.0:(0.00~0.01), preferably as (1.0~1.2):1.0:(0.0013~0.005).

[0066] In some embodiments of the present invention, the wet coating includes a step of mixing the positive electrode material matrix and a wet coating reagent and then performing a second sintering; wherein the wet coating reagent includes metal oxides, strong acids and water.

[0067] In some embodiments of the present invention, the mass ratio of the positive electrode material matrix to the metal oxide is 1.0:(0.0005~0.005), preferably 1.0:(0.0016~0.003); the mass ratio of the positive electrode material matrix to water is 1.0:(1.0~2.0), preferably 1.0:(1.2~2); and the mass ratio of the positive electrode material matrix to the strong acid is 1.0:(0.001~0.01), preferably 1.0:

[0068] (0.001-0.006), more preferably 1.0: (0.005-0.006);

[0069] In some embodiments of the present invention, the temperature of the second sintering is 600-800℃, preferably 700-780℃, and the sintering time is preferably 6-20h, preferably 8-10h; more preferably, the mixing process further includes the steps of filtration and drying.

[0070] In this invention, the strong acid is not particularly limited, and any commercially available strong acid is acceptable, such as one or more of sulfuric acid, hydrochloric acid, or nitric acid.

[0071] In some embodiments of the present invention, the dry coating includes a step of mixing the cathode material coated with the first coating layer obtained in step (3) with a boron-containing compound and then performing a third sintering.

[0072] In some embodiments of the present invention, the mass ratio of the cathode material and the boron-containing compound coated by the first coating layer is 1.0:(0.002-0.02), preferably 1.0:(0.004-0.006); the sintering temperature is 250-450℃, preferably 250-300℃, more preferably 3-15h, and preferably 8-12h.

[0073] It should be understood that the sintering in the wet coating step is the second sintering, while the sintering in the dry coating step is the third sintering.

[0074] In some embodiments of the present invention, the first sintering, the second sintering and the third sintering are further followed by crushing and grading steps, wherein the crushing is selected from air jet milling, and the first sintering, the second sintering and the third sintering are all protected by an oxygen atmosphere.

[0075] In some embodiments of the present invention, the lithium source compound includes, but is not limited to, one or more of lithium-containing oxides, hydroxides, carbonates, sulfates or nitrates, such as lithium hydroxide monohydrate.

[0076] In some embodiments of the present invention, the M source compound includes one or more of oxides, hydroxides, carbonates, sulfates or nitrates containing the M element, preferably oxides or nitrates, such as, but not limited to, one or more of aluminum oxide, titanium oxide, magnesium oxide, yttrium oxide, barium oxide or zirconium oxide.

[0077] In some embodiments of the present invention, the metal oxide is selected from one or more of Al2O3, TiO2, ZrO2, MgO and rare earth element oxides; wherein the rare earth element oxide is selected from one or more of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, or europium oxide.

[0078] In some embodiments of the present invention, the second coating layer is a coating layer formed of a boron-containing compound. Preferably, the boron-containing compound is selected from one or more of boric acid, lithium borate, lithium metaborate, or lithium tetraborate.

[0079] Thirdly, the present invention also provides a low-gas-producing high-nickel lithium-ion battery, wherein the low-gas-producing high-nickel lithium-ion battery contains the above-mentioned double-coated high-nickel cathode material or the double-coated high-nickel cathode material prepared by the above-mentioned preparation method.

[0080] In some embodiments of the present invention, the low-gas-producing high-nickel lithium-ion battery has an initial discharge capacity of 190-210 mAh / g under 4.2V, 1C charge-discharge conditions.

[0081] In some preferred embodiments of the present invention, after the low-gas-producing high-nickel lithium-ion battery is stored at 70°C for 30 days, the battery thickness expansion rate is less than or equal to 32%, preferably less than 30%.

[0082] It should be understood that the low-gas-producing high-nickel lithium-ion battery of the present invention includes electrodes, a non-aqueous electrolyte, a separator, and a container. The electrodes include a positive electrode and a negative electrode. The positive electrode comprises a positive electrode current collector and a positive electrode coating material coated on the current collector. The current collector can be various current collectors well known to those skilled in the art, such as aluminum foil, copper foil followed by nickel-plated steel strip; the positive electrode coating material includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material is the double-coated high-nickel lithium-ion positive electrode material of the present invention. The positive electrode conductive agent includes, but is not limited to, one or more of carbon black conductive agent, carbon nanotubes (CNT), SP-Li, flake graphite, Ketjen black, VGCF, and CNF; the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride (VF2) homopolymers and polyvinylidene fluoride copolymers, and polyvinylidene fluoride (VF2) / hexafluoropropylene (HFP) copolymers.

[0083] The negative electrode comprises a current collector and a negative electrode coating material coated on the current collector. The current collector can be any current collector well known to those skilled in the art, such as aluminum foil, copper foil followed by nickel-plated steel strip. The negative electrode coating material comprises a negative electrode active material, a binder, and a conductive agent. The negative electrode active material includes, but is not limited to, artificial graphite (C) or mesophase carbon microspheres. The conductive agent includes, but is not limited to, one or more of carbon black conductive agent, carbon nanotubes (CNT), SP-Li, conductive graphite, flake graphite, Ketjen black, VGCF, and CNF. The binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex (SBR), and sodium carboxymethyl cellulose (CMC).

[0084] It should be understood that the separator is a PP / PE film commonly used in this industry to separate the positive and negative electrodes; the container is the enclosure of the positive electrode, negative electrode, separator, and electrolyte.

[0085] Fourthly, the present invention also provides the above-mentioned double-coated high-nickel cathode material or the double-coated high-nickel cathode material prepared by the above-mentioned preparation method, or the application of the above-mentioned low-gas-producing high-nickel lithium-ion battery in digital products, electric vehicles or energy storage fields.

[0086] The following specific embodiments illustrate the materials, preparation methods, and applications of the present invention. All reagents or instruments not described in this application are contents that can be routinely confirmed by those skilled in the art.

[0087] The reagents used in the following examples are shown in Table 1.

[0088] Table 1. Reagent information used in the embodiments of the present invention.

[0089]

[0090]

[0091]

[0092] Example 1

[0093] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 92:03:05, was added to a two-planet mill as a precursor (chemical formula: Ni) at a molar ratio of Li:(Ni+Co+Mn):Ti = 1.2:1:0.005. 0.92 Co 0.03 Mn 0.05(OH)₂) and nano-titanium dioxide powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 800 °C for 25 hours (first sintering) under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled at 40 Hz for 10 min to obtain the main material 1 for the cathode material (i.e., the cathode material matrix). Then, 1 kg of a mixture (water:main material 1:sulfuric acid:alumina) was weighed according to a mass ratio of 1.5:1.0:0.006:0.0012. Water, the main material, and sulfuric acid (98 wt%) were added sequentially to the reactor and stirred for 10 min. Alumina was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 600 °C for 18 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material (i.e., the cathode material coated by the first coating layer). Then, 1 kg of boric acid was weighed according to the mass ratio of main material 2 to boric acid of 1.0:0.004. The weighed boric acid was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 450 ℃ for 6 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, it was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 1.

[0094] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 1 was analyzed using the following testing methods. The results are shown in Table 2. The final cathode material has the chemical formula Li. 1.2 Ni 0.92 Co 0.03 Mn 0.05 Ti 0.005 O2·0.0012Al2O3·0.006Li3BO3.

[0095] Accurately weigh 0.2000 g (accurate to 0.0001 g) of the sample into a clean 100 mL glass beaker. Add 10 mL of (1:1) aqua regia solution (for a blank experiment), cover with a watch glass, and heat on a hot plate until the solution evaporates to near dryness. Stop heating and remove the beaker to cool to room temperature. Rinse the watch glass and beaker walls with deionized water at least three times. Transfer the entire solution to a 50 mL volumetric flask, dilute to volume with deionized water, and mix well. Transfer 1 mL of the sample into a 100 mL volumetric flask, dilute to volume, and mix well. Test the above solution using an inductively coupled plasma atomic emission spectrometer (Thermo Fisher Scientific / ICAP7400) according to Part 1 of YS / T 1006.2-2014.

[0096] Table 2. Test results of elemental mass content of cathode materials

[0097] element Li Co Ni Mn Ti Al B ％ 7.9221 1.9112 54.5322 2.8013 0.2376 0.0643 0.0642

[0098] The physical properties of the double-coated high-nickel lithium-ion battery cathode material were tested using the following method:

[0099] 1) Average particle size test: The MS3000 laser particle size analyzer was used for testing. The method is as follows, and the test results are shown in Table 12:

[0100] Take an appropriate amount of sample into a 100ml beaker. First, rinse the inside of the beaker with a wash bottle, then rinse the sample adhering to the bottom of the beaker with the wash bottle. Add 20-30mL of pure water to the beaker. Sonicate for 5 minutes (stirring for 10 seconds before, during, and after sonication at a stirring rate of approximately 2 rpm). Add 100±10ml of pure water to the sampler of the MS3000 laser particle size analyzer, adjust the rotation speed to 3000 rpm, and click start. The instrument will automatically adjust the light and background settings, and wait for prompts. After sonication, transfer the sample to the mixing tank, and rinse the beaker again with the wash bottle to ensure complete sample transfer. After the sample is completely added, the software will automatically start the measurement. The data will be automatically saved upon completion of the measurement.

[0101] 2) Specific surface area test: The specific surface area and porosity analyzer (TriStarⅡ3020, Murray MacTyco Ltd., USA) was used for analysis and testing. The test results are shown in Table 12.

[0102] 3) The test method for free lithium is as follows, and the test results are shown in Table 12.

[0103] Accurately weigh an appropriate amount of sample, m grams (approximately 30 g), accurate to 0.01 g; place the sample in a 250 mL Erlenmeyer flask, add a magnetic stir bar, and add 100 mL of deionized water; place the Erlenmeyer flask on a magnetic stirrer and stir for 30 minutes; filter the mixture using filter paper and a funnel; transfer 50 mL of the filtrate to a 100 mL beaker using a 50 mL pipette, and add a magnetic stir bar; place the beaker on a magnetic stirrer and add 2 drops of phenolphthalein indicator; titrate with 0.05 mol / L hydrochloric acid standard solution until the solution changes from red to colorless; record 0.05 mol / L. Volume V1 of the hydrochloric acid standard titration solution (endpoint 1); add 2 drops of methyl red indicator, the color changes from colorless to yellow; titrate with 0.05 mol / L hydrochloric acid standard titration solution until the solution color changes from yellow to orange; place the beaker on a heating furnace and heat until the solution boils (the solution color changes from orange to yellow); remove the 100 mL beaker and cool to room temperature; place the beaker on a magnetic stirrer again; titrate with 0.05 mol / L hydrochloric acid standard titration solution until the solution color changes from yellow to pale red. Record the volume V2 of the 0.05 mol / L hydrochloric acid standard titration solution (endpoint 2);

[0104] Lithium hydroxide: LiOH (wt%) = [V2 - 2 × (V2 - V1)] × 0.05 × 23.946 × 2 × 100 / (m × 1000)

[0105] Lithium carbonate: Li₂CO₃ (wt%) = (V₂ - V₁) × 0.05 × 73.886 × 2 × 100 / (m × 1000)

[0106] Total free lithium: Li + (wt%)=V2×0.05×6.94×2×100 / (m×1000)

[0107] m – mass of the sample (g); V1 – first titration endpoint; V2 – second titration endpoint.

[0108] 4) Morphology testing of cathode materials:

[0109] SEM testing was performed on cathode material 1 from Example 1. The test parameters were: accelerating voltage EHT = 15.00 kV, working distance WD = 7.0 mm, and probe selection SignalA = InLens. Figure 1 As shown, by Figure 1 It can be seen that the material has a primary particle morphology, that is, the morphology of primary particles and secondary particles formed by the aggregation of a small number of primary particles.

[0110] Example 2

[0111] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 92:03:05, was added to a two-planet mill at a molar ratio of Li:(Ni+Co+Mn):Zr = 1.08:1:0.002. The precursor (chemical formula: Ni) was added to the mill. 0.92 Co 0.03 Mn 0.05 (OH)₂) and nano-zirconia powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 830 °C for 20 hours (first sintering) under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled again at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, 1 kg of water, main material 1, sulfuric acid, and titanium dioxide were weighed according to a mass ratio of 2.0:1.0:0.005:0.0016. Water, main material 1, and sulfuric acid (98 wt%) were added sequentially to the reactor and stirred for 10 min. Titanium dioxide was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 700 °C for 8 hours (second sintering) under an oxygen atmosphere at a heating rate of 10 °C / min, and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium borate were weighed according to the mass ratio of main material 2 to lithium borate of 1.0:0.006. The lithium borate was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 250 ℃ for 12 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 2.

[0112] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material were tested according to the method described in Example 1, and the results are shown in Table 12.

[0113] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 2 was analyzed using the test method described in Example 1. The results are shown in Table 3. The final cathode material has the chemical formula Li. 1.08 Ni 0.92 Co 0.03 Mn 0.05 Zr 0.002 O2·0.002TiO2·0.008Li3BO3.

[0114] Table 3. Test results of elemental mass content of cathode materials

[0115] element Li Co Ni Mn Zr Ti B ％ 7.3123 1.9314 54.4619 2.8623 0.1832 0.0952 0.0840

[0116] Example 3

[0117] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 87:05:08, was added to a two-plane planetary mill at a molar ratio of Li:(Ni+Co+Mn):Al = 1.1:1:0.003. The precursor (chemical formula: Ni) was added to the mill at a molar ratio of Ni:Co:Mn = 87:05:08. 0.87 Co 0.05 Mn 0.08 (OH)₂) and nano-alumina powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 860 °C for 20 hours (first sintering) under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled again at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, water, main material 1, sulfuric acid, and zirconium oxide, totaling 1 kg, were weighed according to a mass ratio of water:main material 1:sulfuric acid:zirconia of 1.2:1.0:0.005:0.003. These were added sequentially to a reactor and stirred for 10 min. Zirconia was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 750 °C for 10 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium metaborate were weighed according to the mass ratio of main material 2 to lithium metaborate of 1.0:0.005. The lithium metaborate was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 300 ℃ for 8 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 3.

[0118] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material 3 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0119] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 3 was analyzed using the test method described in Example 1. The results are shown in Table 4. The final cathode material has the chemical formula Li. 1.1 Ni 0.87 Co 0.05 Mn 0.08 Al 0.003 O2·0.0025ZrO2·0.01LiBO2.

[0120] Table 4. Test results of elemental mass content of cathode materials

[0121] element Li Co Ni Mn Al Zr B ％ 7.4128 3.1246 52.6737 4.5858 0.0542 0.2287 0.1020

[0122] Example 4

[0123] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 83:07:10, was added to a binary planetary mill jar according to a Li:(Ni+Co+Mn):Zr molar ratio of 1.12:1:0.002. The precursor (chemical formula: Ni) was added to the jar. 0.83 Co 0.07 Mn 0.1 (OH)₂) and nano-zirconia powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 880 °C for 24 hours under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled again at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, 1 kg of water, main material 1, sulfuric acid, and alumina were weighed into a reactor according to a mass ratio of water:main material 1:sulfuric acid:alumina of 1.5:1.0:0.005:0.003. Water, main material 1, sulfuric acid, and alumina, totaling 1 kg, were added sequentially to the reactor and stirred for 10 min. Alumina was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 780 °C for 10 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium tetraborate were weighed according to the mass ratio of main material 2 to lithium tetraborate of 1.0:0.004. The lithium tetraborate was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 280 ℃ for 8 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 4.

[0124] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material 4 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0125] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 4 was analyzed using the test method described in Example 1. The results are shown in Table 5. The final cathode material has the chemical formula Li. 1.12 Ni 0.83 Co 0.07 Mn 0.10 Zr 0.002 O2·0.003Al2O3·0.0025Li2B4O7.

[0126] Table 5 shows the test results of elemental mass content of the cathode material.

[0127] element Li Co Ni Mn Zr Al B ％ 7.4789 4.2859 50.1489 5.6396 0.1743 0.1478 0.0998

[0128] Example 5

[0129] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 87:05:08, was added to a binary planetary mill jar according to a Li:(Ni+Co+Mn):Zr molar ratio of 1.1:1:0.0013. The precursor (chemical formula: Ni) was added to the jar. 0.87 Co 0.05 Mn 0.08 (OH)₂) and nano-zirconia powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 810 °C for 30 hours under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled again at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, water, main material 1, sulfuric acid, and alumina, totaling 1 kg, were weighed according to a water:main material 1:sulfuric acid:alumina mass ratio of 1.2:1.0:0.005:0.0024. These were added sequentially to a reactor, and the mixture was stirred for 10 min. Alumina was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 760 °C for 12 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and boric acid were weighed according to the mass ratio of main material 2 to boric acid of 1.0:0.004. The boric acid was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 320 ℃ for 6 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 5.

[0130] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material 5 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0131] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 5 was analyzed using the test method described in Example 1. The results are shown in Table 6. The final cathode material has the chemical formula Li. 1.1 Ni 0.87 Co 0.05 Mn 0.08 Zr 0.0016O2·0.0024Al2O3·0.0065Li3BO3.

[0132] Table 6 shows the test results of elemental mass content of the cathode material.

[0133] element Li Co Ni Mn Zr Al B ％ 7.3949 3.2790 52.6280 4.7500 0.1120 0.1372 0.0689

[0134] Example 6

[0135] Lithium hydroxide monohydrate and a precursor (chemical formula: Ni+Co+Mn) with a molar ratio of Ni:Co:Mn = 92:05:03 were added to a two-planet mill at a molar ratio of Li:(Ni+Co+Mn):Y = 1.02:1:0.002. 0.92 Co 0.05 Mn 0.03 (OH)₂) and yttrium oxide powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to mix evenly, and the mixture was discharged. The mixture was placed in a muffle furnace and sintered at 850 °C for 8 hours (first sintering) under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, water, main material 1, nitric acid, and niobium oxide, totaling 1 kg, were weighed according to a water:main material 1:nitric acid:niobium oxide mass ratio of 1.0:1.0:0.001:0.002. Water, main material 1, nitric acid, and niobium oxide were added to the reactor sequentially, and the mixture was stirred for 10 min. Then, niobium oxide was added, and stirring was continued for 10 min. The mixture was filtered and dried at 120 °C. The dried sample was sintered at 720 °C for 20 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium borate were weighed according to the mass ratio of main material 2 to lithium borate of 1.0:0.02. The lithium borate was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 350 ℃ for 3 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 6.

[0136] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material 6 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0137] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 6 was analyzed using the test method described in Example 1. The results are shown in Table 7. The final cathode material has the chemical formula Li. 1.02 Ni 0.92 Co0.05 Mn 0.03 Y 0.002 O2·0.00075Nb2O5·0.03Li3BO3.

[0138] Table 7. Test results of elemental mass content of cathode materials

[0139] element Li Co Ni Mn Y Nb B ％ 7.0254 2.8946 54.1236 1.6758 0.1753 0.1289 0.3087

[0140] Example 7

[0141] The difference from Example 6 is that the wet coating did not involve the addition of nitric acid. The specific method is as follows:

[0142] Lithium hydroxide monohydrate and a precursor (chemical formula: Ni+Co+Mn) with a molar ratio of Ni:Co:Mn = 92:05:03 were added to a two-planet mill at a molar ratio of Li:(Ni+Co+Mn):Y = 1.02:1:0.002. 0.92 Co 0.05 Mn 0.03 (OH)₂) and yttrium oxide powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to mix evenly, and the mixture was discharged. The mixture was placed in a muffle furnace and sintered at 850 °C for 8 hours (first sintering) under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, water, main material 1, and niobium oxide, totaling 1 kg, were weighed according to a water:main material 1:niobium oxide mass ratio of 1.0:1.0:0.002. Water and main material 1 were added sequentially to the reactor, mixed and stirred for 10 min, then niobium oxide was added, and stirring was continued for 10 min. The mixture was filtered and dried at 120 °C. The dried sample was sintered at 720 °C for 20 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized using an air jet mill at a pulverizing pressure of 0.65 MPa to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium borate were weighed according to the mass ratio of main material 2 to lithium borate of 1.0:0.02. The lithium borate was added to the main material 2 and ball-milled at a speed of 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 350 ℃ for 3 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the material was sieved through a 300-mesh metal sieve to obtain the double-coated high-nickel lithium-ion battery cathode material 7.

[0143] The particle size, specific surface area, and total free lithium content of the primary particles of the double-coated high-nickel lithium-ion battery cathode material 7 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0144] The elemental composition of the double-coated high-nickel lithium-ion battery cathode material 7 was analyzed using the test method described in Example 1. The results are shown in Table 8. The final cathode material has the chemical formula Li. 1.02 Ni 0.92 Co 0.05 Mn 0.03 Y 0.002 O2·0.00075Nb2O5·0.03Li3BO3.

[0145] Table 8. Test results of elemental mass content of cathode materials

[0146] element Li Ni Co Mn Y Nb B ％ 7.0264 54.1674 2.8763 1.6678 0.1748 0.1302 0.3142

[0147] Comparative Example 1

[0148] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 83:07:10, was added to a two-planet mill at a molar ratio of Li:(Ni+Co+Mn):Zr = 1.12:1:0.002. The precursor (chemical formula: Ni) was added to the mill. 0.83 Co 0.07 Mn 0.1 (OH)₂) and nano-zirconia powder, totaling 1 kg, were ball-milled at 40 Hz for 10 min to obtain a homogeneous mixture. This mixture was then placed in a muffle furnace and sintered at 880 °C for 24 hours under an oxygen atmosphere at a heating rate of 5 °C / min. After cooling to room temperature, it was ball-milled again at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, water, main material 1, sulfuric acid, and alumina, totaling 1 kg, were weighed according to a water:main material 1:sulfuric acid:alumina mass ratio of 1.5:1.0:0.005:0.003. Water, main material 1, sulfuric acid, and alumina were added sequentially and stirred for 10 min. Alumina was then added, and stirring continued for another 10 min. The mixture was filtered and dried at 120 °C. The dried sample was then sintered at 780 °C for 10 hours under an oxygen atmosphere at a heating rate of 10 °C / min (second sintering), and then cooled to room temperature. The sample after the second sintering was then pulverized by airflow and sieved through a 300-mesh metal sieve to obtain the positive electrode material D1.

[0149] The particle size, specific surface area, and total free lithium content of the primary particles of the cathode material D1 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0150] The elemental composition of cathode material D1 was analyzed using the test method described in Example 1. The results are shown in Table 9. The final chemical formula of cathode material D1 is Li. 1.12 Ni 0.83 Co 0.07 Mn 0.10 Zr 0.002 O2·0.003Al2O3.

[0151] Table 9 shows the test results of elemental mass content of the cathode material.

[0152] element Li Co Ni Mn Zr Al ％ 7.4242 4.3111 50.2667 5.6179 0.1801 0.1588

[0153] Comparative Example 2

[0154] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 83:07:10, was added to the ball mill jar according to the molar ratio of Li:(Ni+Co+Mn):Zr = 1.12:1:0.002. The precursor (chemical formula: Ni) was added to the jar. 0.83 Co 0.07 Mn 0.1 (OH)2) and nano-zirconia powder, a total of 1 kg, were ball-milled at 40 Hz for 10 min to obtain a uniform mixture. The mixture was then placed in a muffle furnace and sintered at 880 ℃ for 24 hours under an oxygen atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the mixture was ball-milled at 40 Hz for 10 min to obtain the main material 1 for the cathode material. Then, lithium tetraborate, a total of 1 kg, was weighed according to the mass ratio of main material 1 to lithium tetraborate of 1.0:0.004. The lithium tetraborate was added to main material 1 and ball-milled at 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 280 ℃ for 8 hours under an air atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, the mixture was sieved through a 300-mesh metal sieve to obtain cathode material D2.

[0155] The particle size, specific surface area, and total free lithium content of the primary particles of the cathode material D2 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0156] The elemental composition of cathode material D2 was analyzed using the test method described in Example 1. The results are shown in Table 10. The final chemical formula of cathode material D2 is Li. 1.12 Ni 0.83 Co 0.07 Mn 0.10 Zr 0.002 O2·0.0025Li2B4O7.

[0157] Table 10 Results of elemental mass content test for cathode materials

[0158] element Li Co Ni Mn Zr B ％ 7.8696 4.2959 50.1270 5.6149 0.1764 0.1022

[0159] Comparative Example 3

[0160] The difference from Example 4 is that the first coating is done by dry coating followed by washing with water, and then a second dry coating is performed. The specific method is as follows:

[0161] Lithium hydroxide monohydrate, with a molar ratio of Ni:Co:Mn = 83:07:10, was added to a two-planet mill at a molar ratio of Li:(Ni+Co+Mn):Zr = 1.12:1:0.002. The precursor (chemical formula: Ni) was added to the mill. 0.83 Co 0.07 Mn 0.1 (OH)2) and nano-zirconia powder, a total of 1 kg, were mixed evenly by ball milling at 40 Hz for 10 min and discharged (i.e., the mixture). The mixture was placed in a muffle furnace and sintered at 880 ℃ for 24 hours under an oxygen atmosphere at a heating rate of 5 ℃ / min. After cooling to room temperature, it was ball milled at 40 Hz for 10 min to obtain the main material 1 for the cathode material.

[0162] The obtained main material 1 and alumina were added to a ball mill at a mass ratio of 1.0:0.003, totaling 400g. The mixture was ball-milled at a speed of 40Hz for 10 minutes and then discharged. The mixture was placed in a muffle furnace and sintered at 780℃ for 10 hours (second sintering) under an oxygen atmosphere at a heating rate of 10℃ / min. The mixture was then cooled to room temperature to obtain an intermediate product.

[0163] Then, water and intermediate product were added to the reactor in a water-to-intermediate product mass ratio of 1.5:1.0, totaling 1 kg. The mixture was stirred for 10 min, filtered, and dried at 120℃. The dried sample was used to obtain the main material 2 for the cathode material. Then, 1 kg of main material 2 and lithium tetraborate were weighed in a main material 2-lithium tetraborate mass ratio of 1.0:0.004. The lithium tetraborate was added to the main material 2, and the mixture was ball-milled at 40 Hz for 10 min. The uniformly mixed material was placed in a muffle furnace and sintered at 280℃ for 8 hours in air atmosphere at a heating rate of 5℃ / min. After cooling to room temperature, the mixture was sieved through a 300-mesh metal sieve to obtain the cathode material D3.

[0164] The particle size, specific surface area, and total free lithium content of the primary particles of the cathode material D3 were tested according to the method described in Example 1, and the results are shown in Table 12.

[0165] The elemental composition of cathode material D3 was analyzed using the test method described in Example 1. The results are shown in Table 11. The final chemical formula of the cathode material is Li. 1.12 Ni 0.83 Co 0.07 Mn 0.10 Zr 0.002 O2·0.003Al2O3·0.0025Li2B4O7.

[0166] Table 11 shows the test results of elemental mass content of the cathode material.

[0167] element Li Co Ni Mn Zr Al B ％ 7.5124 4.2785 50.2037 5.6271 0.1712 0.1523 0.0956

[0168] Table 12 Characterization results of the cathode materials obtained in the examples and comparative examples.

[0169]

[0170] Experimental Example

[0171] Preparation and performance evaluation of lithium-ion batteries.

[0172] Different battery systems significantly affect the cycle retention rate of materials. This experiment uses the most common evaluation system: a 1 mol / L lithium hexafluorophosphate solution as the electrolyte, with the solvent being a mixture of dimethyl carbonate (DMC): ethylene carbonate (EC): diethyl carbonate (DEC) in a mass ratio of 1:1:1. The negative electrode material is a mixture of artificial graphite, conductive carbon black, carboxymethyl cellulose, and adhesive in a weight ratio of 95:1:1:3. The cell model is 454261. This approach aims to quickly expose the actual defects of the positive electrode material and determine its performance.

[0173] The full cell (cell model 454261) was prepared according to the following method:

[0174] Positive electrode preparation: The positive electrode materials prepared in the above examples and comparative examples were added to N-methylpyrrolidone (NMP) at a weight ratio of 94:3:3 (the weight ratio of positive electrode material to NMP was 2.1:1) and thoroughly mixed to form a uniform slurry. The slurry was then coated onto an aluminum foil current collector, dried, and pressed into an electrode sheet.

[0175] Negative electrode preparation: Negative electrode artificial graphite is mixed with conductive carbon black (SP), carboxymethyl cellulose (CMC), and adhesive (SBR) in a weight ratio of 95:1:1:3 in sufficient pure water, stirred to form a uniform slurry, coated on copper foil current collector, dried and pressed into an electrode sheet.

[0176] The diaphragm is a three-layer composite film material of PP / PE / PP.

[0177] After pressing, the positive and negative electrode sheets are spot-welded with tabs, inserted into the diaphragm, wound on a winding machine, and placed into a soft-pack fixture. The top and sides are sealed, and then the sheets are baked in an oven. Afterward, 9g of electrolyte is injected under conditions of relative humidity less than 1.5%, and after 48 hours of formation (using the Zhejiang Hangke LIP-3AHB06 high-temperature constant-temperature formation system), vacuum sealing is performed. The electrolyte is 1mol / L lithium hexafluorophosphate, and the solvent in the lithium hexafluorophosphate solution is a mixed solvent with a mass ratio of dimethyl carbonate (DMC): ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1:1.

[0178] Sample drying and high-temperature battery testing were performed using the Dongguan Kerui Electromechanical KPBAK-03E-02 high-efficiency vacuum drying oven.

[0179] The charge-discharge test of the lithium-ion battery prepared by this invention was conducted on the Wuhan Landian Battery Tester. The method is as follows, and the results are shown in Table 13.

[0180] 1) Capacity testing method

[0181] Connect the prepared lithium-ion battery to the test stand and start the test program. Setup steps: Set the test temperature to 25℃, let it stand for 4 hours, charge at a constant current of 1C to 4.2V, then charge at a constant voltage of 4.2V for 0.5 hours, let it stand for 5 minutes, and then discharge at a constant current of 1C to 3.0V to obtain the capacity at this current and voltage.

[0182] 2) Test method for capacity retention

[0183] Connect the battery that has undergone the above capacity test to the test rack, start the test program, and set the steps as follows: set the test temperature to 45℃, let it stand for 4 hours, charge it with a constant current of 1C to 4.2V, switch to constant voltage charging at 4.2V for 0.5 hours, let it stand for 5 minutes, then discharge it with a constant current of 1C to the cutoff voltage of 3.0V, let it stand for 5 minutes, and repeat the steps at the beginning of the constant current charging to perform a cycle test, so as to obtain the capacity retention rate for different cycles.

[0184] 3) The battery thickness expansion rate was tested using a PPG battery thickness gauge.

[0185] Charge the battery to the set voltage of 4.25V, and use a PPG battery thickness gauge to measure the battery thickness. Then, place the battery in a 70℃ constant temperature chamber for 30 days, and take it out. Use a PPG battery thickness gauge to measure the battery thickness at this time. Calculate the battery thickness expansion rate using the following formula: Battery thickness expansion rate = (Battery thickness after constant temperature - Battery thickness before constant temperature) / Battery thickness before constant temperature.

[0186] Table 13 Battery performance test results

[0187]

[0188] The cathode materials prepared in the embodiments of the present invention all have primary particle morphology. As shown in Table 12, the total free lithium in the cathode materials prepared in the embodiments of the present invention is <2000ppm, and the specific surface area is 0.8-1.2m². 2 The particle size is between 2.5-4 μm and the g / g.

[0189] As shown in Table 13, the lithium-ion batteries made using double-coated high-nickel lithium-ion battery cathode materials all exhibited a thickness expansion rate of less than 90% after being placed in a 70°C constant temperature chamber for 30 days. Compared to Example 4, Comparative Example 1, which only used a single wet coating process, had a battery thickness expansion rate of 120% after being placed in a 70°C constant temperature chamber for 30 days, which was significantly higher than Example 4. Comparative Example 2, which only used a single dry coating process, had a battery thickness expansion rate of 105% after being placed in a 70°C constant temperature chamber for 30 days, which was significantly higher than Example 4. Comparative Example 3, which used a process of single dry coating followed by water washing and then a second dry coating process, had a battery thickness expansion rate of 152% after being placed in a 70°C constant temperature chamber for 30 days, which was also significantly higher than Example 4 and other embodiments of the present invention. Furthermore, in Examples 1-6 of the present invention, strong acid was added to the wet process to etch the surface, and the resulting cathode material was used to prepare lithium-ion batteries. After being placed in a constant temperature chamber at 70°C for 30 days, the battery thickness expansion rate was 23-32%. Compared with Example 6, Example 7 did not add strong acid to the wet process to etch the surface, and the resulting cathode material was used to prepare lithium-ion batteries. After being placed in a constant temperature chamber at 70°C for 30 days, the battery thickness expansion rate was 87%, which is nearly 172% higher than that of Example 6.

[0190] In summary, the cathode materials prepared by a single coating in Comparative Examples 1 and 2 exhibited high thickness expansion rates and poor gas generation performance. The cathode material prepared by Comparative Example 3, using a process of initial dry coating followed by water washing and then a second dry coating, while significantly reducing the free lithium content through water washing, actually had an even higher thickness expansion rate and decreased gas generation performance. This invention, through a combined wet and dry coating process, achieves superior cycle performance and gas generation performance for high-nickel cathode materials while maintaining high capacity. Therefore, the cathode material of this invention achieves high capacity while maintaining good cycle performance and gas generation performance, demonstrating excellent overall performance.

[0191] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A double-coated high-nickel lithium-ion battery cathode material, characterized in that, The general chemical formula of the cathode material is Li. a Ni x Co y Mn z M b O2·cA·dB, where: 1.00≤a≤1.20, 0.00<b≤0.01, 0.00<c≤0.01, 0.00<d≤0.05, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, x+y+z=1; M is a doping element, wherein M is selected from one or more of Mg, Ti, Al, Zr, Ba and rare earth elements; A is the first coating layer, and B is the second coating layer; It includes a positive electrode material matrix, a first coating layer covering the surface of the positive electrode material matrix, and a second coating layer covering the surface of the first coating layer; The first coating layer and the second coating layer are prepared by sequentially coating the positive electrode material substrate with a metal oxide and a boron-containing compound; the metal oxide is selected from one or more of Al2O3, TiO2, ZrO2, MgO and rare earth element oxides; the boron-containing compound is selected from one or more of boric acid, lithium borate, lithium metaborate or lithium tetraborate. The first coating layer is a coating layer formed by wet coating of metal oxide; the wet coating includes the step of mixing the positive electrode material matrix, water, strong acid and metal oxide and then sintering; the mass ratio of the positive electrode material matrix and the strong acid is 1:0.001~0.01; wherein, the strong acid is one or more of sulfuric acid, hydrochloric acid or nitric acid; The second coating layer is a coating layer formed by dry coating of a boron-containing compound; the dry coating includes the step of mixing the cathode material coated by the first coating layer and the boron-containing compound and then sintering them.

2. The double-coated high-nickel lithium-ion battery cathode material according to claim 1, wherein, The general chemical formula of the cathode material is Li. a Ni x Co y Mn z M b O2·cA·dB, where: 1.00≤a≤1.20, 0.001≤b≤0.01, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, 0.0005<c≤0.01, 0.001<d≤0.05, x+y+z=1.

3. The double-coated high-nickel lithium-ion battery cathode material according to claim 1, wherein, The general chemical formula of the cathode material is Li. a Ni x Co y Mn z M b O2·cA·dB, where: 1.02≤a≤1.20, 0.0015≤b≤0.005, 0.80≤x<1.00, 0.00≤y<0.12, 0.00≤z<0.2, 0.0005<c≤0.01, 0.001<d≤0.03, x+y+z=1.

4. The double-coated high-nickel lithium-ion battery cathode material according to claim 1, wherein, The rare earth element is selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or europium.

5. The double-coated high-nickel lithium-ion battery cathode material according to claim 2, wherein, The rare earth element is selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or europium.

6. The double-coated high-nickel lithium-ion battery cathode material according to claim 3, wherein, The rare earth element is selected from one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or europium.

7. The double-coated high-nickel lithium-ion battery cathode material according to claim 1, wherein, The rare earth element is yttrium.

8. The double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-7, wherein, The rare earth element oxides are selected from one or more of the following: lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, yttrium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, scandium oxide, or europium oxide.

9. The double-coated high-nickel lithium-ion battery cathode material according to claim 8, wherein, The rare earth element oxide is yttrium oxide.

10. The dual-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-7, wherein, The cathode material has a primary particle morphology.

11. The double-coated high-nickel lithium-ion battery cathode material according to claim 8, wherein, The cathode material has a primary particle morphology.

12. The double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-7, wherein, The cathode material contains less than 2000 ppm of total free lithium, based on the mass of the cathode material.

13. The double-coated high-nickel lithium-ion battery cathode material according to claim 8, wherein, The cathode material contains less than 2000 ppm of total free lithium, based on the mass of the cathode material.

14. The double-coated high-nickel lithium-ion battery cathode material according to claim 10, wherein, The cathode material contains less than 2000 ppm of total free lithium, based on the mass of the cathode material.

15. The dual-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-7, wherein, The specific surface area of ​​the cathode material is 0.4-1.5 m². 2 / g.

16. The double-coated high-nickel lithium-ion battery cathode material according to claim 8, wherein, The specific surface area of ​​the cathode material is 0.4-1.5 m². 2 / g.

17. The dual-coated high-nickel lithium-ion battery cathode material according to claim 10, wherein, The specific surface area of ​​the cathode material is 0.4-1.5 m². 2 / g.

18. The double-coated high-nickel lithium-ion battery cathode material according to claim 12, wherein, The specific surface area of ​​the cathode material is 0.4-1.5 m². 2 / g.

19. The double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-7, wherein, The average particle size of the cathode material is 2-5 μm.

20. The double-coated high-nickel lithium-ion battery cathode material according to claim 8, wherein, The average particle size of the cathode material is 2-5 μm.

21. The dual-coated high-nickel lithium-ion battery cathode material according to claim 10, wherein, The average particle size of the cathode material is 2-5 μm.

22. The dual-coated high-nickel lithium-ion battery cathode material according to claim 12, wherein, The average particle size of the cathode material is 2-5 μm.

23. The dual-coated high-nickel lithium-ion battery cathode material according to claim 15, wherein, The average particle size of the cathode material is 2-5 μm.

24. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-23, characterized in that, Includes the following steps: (1) The lithium source compound, the cathode material precursor and the M source compound are mixed to obtain a mixture; (2) The mixture from step (1) is subjected to a first calcination to obtain the cathode material matrix; (3) The cathode material substrate obtained in step (2) is wet coated to obtain the cathode material coated with the first coating layer; (4) The cathode material coated with the first coating layer obtained in step (3) is dry coated to obtain a double-coated high-nickel lithium-ion battery cathode material.

25. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 24, wherein, The lithium source compound, cathode material precursor, and M source compound are in the elemental molar ratio of Li:(Ni+Co+Mn):M of (1.0~1.2):1.0:(0.00~0.01).

26. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 24, wherein, The wet coating process includes a second sintering step after mixing the cathode material matrix, water, strong acid, and metal oxide.

27. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 24, wherein, The mass ratio of the cathode material matrix to the metal oxide is 1.0:(0.0005~0.005).

28. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 25, wherein, The mass ratio of the cathode material matrix to the metal oxide is 1.0:(0.0005~0.005).

29. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 26, wherein, The mass ratio of the cathode material matrix to the metal oxide is 1.0:(0.0005~0.005).

30. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 24, wherein, The mass ratio of the positive electrode material matrix to water is 1:(1.0~2.0).

31. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 25, wherein, The mass ratio of the positive electrode material matrix to water is 1:(1.0~2.0).

32. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 26, wherein, The mass ratio of the positive electrode material matrix to water is 1:(1.0~2.0).

33. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 27, wherein, The mass ratio of the positive electrode material matrix to water is 1:(1.0~2.0).

34. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 26, wherein, The temperature for the second sintering is 600-800℃.

35. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 26, wherein, The second sintering time is 6-20 hours.

36. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 34, wherein, The second sintering time is 6-20 hours.

37. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 26, wherein, The mixing process also includes filtering and drying steps.

38. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to any one of claims 24-37, wherein, The dry coating process includes a third sintering step after mixing the cathode material coated with the first coating layer obtained in step (3) with a boron-containing compound.

39. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 38, wherein, The mass ratio of the cathode material to the boron-containing compound coated in the first coating layer is 1.0:(0.002~0.02).

40. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 38, wherein, The temperature for the third sintering is 250-450℃.

41. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 39, wherein, The temperature for the third sintering is 250-450℃.

42. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 38, wherein, The third sintering time is 3-15 hours.

43. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 39, wherein, The third sintering time is 3-15 hours.

44. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to claim 40, wherein, The third sintering time is 3-15 hours.

45. A low-gas-producing, high-nickel lithium-ion battery, wherein, The low-gas-producing high-nickel lithium-ion battery contains the double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-23 or the double-coated high-nickel lithium-ion battery cathode material prepared by any one of claims 24-44.

46. ​​The low-gas-production, high-nickel lithium-ion battery according to claim 45, wherein, The low-gas-producing high-nickel lithium-ion battery has an initial discharge capacity of 190-210 mAh / g under 4.2V and 1C charge / discharge conditions.

47. The low-gas-production, high-nickel lithium-ion battery according to claim 45 or 46, wherein, The low-gas-producing high-nickel lithium-ion battery, when stored at 70°C for 30 days, has a thickness expansion rate of less than or equal to 32%.

48. The method for preparing the double-coated high-nickel lithium-ion battery cathode material according to any one of claims 1-23 or any one of claims 24-44, or the low-gas-producing high-nickel lithium-ion battery according to any one of claims 45-47, is used in digital products, electric vehicles, or energy storage fields.

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