High-nickel ternary single-crystal positive electrode material, preparation method thereof, positive electrode sheet and lithium ion battery

Abstract

The application provides a high-nickel ternary single-crystal positive electrode material and a preparation method, a positive electrode sheet and a lithium ion battery. The preparation method of the high-nickel ternary single-crystal positive electrode material comprises the following steps: providing a precursor, the porosity of the precursor being 30%-50%; mixing the precursor with a lithium source, and performing nitrogenization treatment under an ammonia atmosphere to prepare a nitrogenization treatment product; performing pre-oxidation treatment on the nitrogenization treatment product under an oxygen atmosphere to prepare a pre-oxidation treatment product; performing sintering treatment on the pre-oxidation treatment product under an oxygen atmosphere to prepare the high-nickel ternary single-crystal positive electrode material; and the temperature of the sintering treatment being 700 DEG C-900 DEG C. The preparation method of the high-nickel ternary single-crystal positive electrode material provided by the application reconstructs the solid-phase reaction path of the high-nickel material, suppresses the Li + / Ni 2+ mixing arrangement while realizing controllable preparation of single-crystal particles at a low temperature, so that the high-nickel ternary positive electrode material with high capacity retention rate and excellent cycle stability is obtained.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to high-nickel ternary single-crystal cathode materials and their preparation methods, cathode sheets, and lithium-ion batteries. Background Technology

[0002] High-nickel ternary cathode materials have become ideal materials for realizing high-energy-density lithium-ion batteries due to their high specific capacity and high operating voltage. However, with the increase of nickel content, the thermal stability and structural stability of the materials become more and more obvious, mainly due to: 1) Secondary particle cracking: Polycrystalline high-nickel ternary cathode materials prepared by the traditional co-precipitation method generate internal stress due to anisotropic volume changes during charging and discharging, leading to the propagation of cracks at grain boundaries and electrolyte intrusion, which accelerates interfacial side reactions; 2) Ni 2+ With Li + With similar radii, Li is more likely to occur. + / Ni 2+ Mixing and dispersing disrupts the stability of the layered structure; 3) Uncontrolled reaction kinetics: In traditional solid-state sintering, the reaction rate between the precursor and the lithium source is too fast, resulting in uneven grain growth and easy formation of internal defects.

[0003] To address the aforementioned shortcomings, traditional improvement strategies primarily include single-crystalization. However, while single-crystalization can suppress cracking, it typically requires ultra-high temperature sintering (>900℃), leading to increased lithium volatilization and cation mixing, resulting in poor cycle stability and capacity retention in high-nickel ternary cathode materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a high-nickel ternary single-crystal cathode material and its preparation method, a cathode sheet, and a lithium-ion battery. The preparation method of the high-nickel ternary single-crystal cathode material provided in this application, by reconstructing the solid-phase reaction pathway of the high-nickel material, suppresses Li... + / Ni 2+ While mixing and arranging, controllable preparation of single crystal particles at low temperature is achieved, thereby obtaining a high-nickel ternary cathode material with both high capacity retention and excellent cycle stability.

[0005] In a first aspect, this application provides a method for preparing a high-nickel ternary single-crystal cathode material, comprising the following steps:

[0006] Provide a precursor; the general chemical formula of the precursor is Ni x Co y Mn 1-x-y (OH)₂, 0.8≤x≤0.96, 0.02≤y≤0.18; the porosity of the precursor is 30%-50%;

[0007] The precursor was mixed with a lithium source and nitrided under an ammonia atmosphere to prepare the nitrided product.

[0008] The nitriding product was pre-oxidized in an oxygen atmosphere to prepare the pre-oxidized product.

[0009] The pre-oxidized product was sintered in an oxygen atmosphere to obtain a high-nickel ternary single-crystal cathode material; the sintering temperature was 700℃-900℃.

[0010] In some embodiments, the molar ratio of lithium metal in the lithium source to transition metal in the precursor is (1.01-1.2):1.

[0011] In some embodiments, the nitriding treatment performed under an ammonia atmosphere satisfies at least one of the following conditions:

[0012] (1) The flow rate of ammonia is 0.05 m³ / s. 3 / h-0.5m 3 / h;

[0013] (2) The nitriding temperature is 300℃-500℃;

[0014] (3) The holding time for nitriding treatment is 2h-10h.

[0015] In some implementations, the precursor satisfies at least one of the following conditions:

[0016] (1) The particle size D50 of the precursor is 1.5 μm to 5 μm;

[0017] (2) The radial distance of the precursor is <0.7;

[0018] (3) The specific surface area of ​​the precursor is 10 m². 2 / g-30m 2 / g;

[0019] (4) The precursor includes secondary particles with a spherical morphology. The secondary particles are formed by the aggregation of multiple primary particles in the form of thin strips or needles. The multiple primary particles are arranged radially along the center of the secondary particles toward the outer periphery.

[0020] In some embodiments, the pre-oxidation treatment satisfies at least one of the following conditions:

[0021] (1) The temperature of the pre-oxidation treatment is 500℃-650℃;

[0022] (2) The heat preservation time for pre-oxidation treatment is 4h-8h.

[0023] In some implementations, the sintering process satisfies at least one of the following conditions:

[0024] (1) The sintering temperature is 780℃-850℃;

[0025] (2) The holding time for sintering is 10h-24h.

[0026] In some implementations, the high-nickel ternary single-crystal cathode material satisfies at least one of the following conditions:

[0027] (1) The primary particle size is 0.5μm-2μm;

[0028] (2) Cation mixing degree <2%.

[0029] Secondly, this application provides a high-nickel ternary single-crystal cathode material, which is prepared by any of the above-mentioned methods for preparing high-nickel ternary single-crystal cathode materials.

[0030] Thirdly, this application provides a cathode material, including the aforementioned high-nickel ternary single-crystal cathode material.

[0031] Fourthly, this application provides a lithium-ion battery, including the aforementioned positive electrode.

[0032] Compared with traditional technologies, this application has at least the following beneficial effects:

[0033] The method for preparing high-nickel ternary single-crystal cathode material provided in this application involves nitriding a high-porosity precursor. The high porosity of the precursor ensures the bulk homogeneity of the nitriding modification, transforming the precursor into a nitride intermediate. The high activation energy of the nitride intermediate forms a kinetic barrier, effectively suppressing the instantaneous explosive reaction between the lithium source and the precursor. This facilitates a shift from traditional rapid diffusion control to slow nucleation-growth control, providing sufficient time for ordered atomic migration and lattice rearrangement. This solves the problems of uneven grain growth and internal defects caused by runaway reaction rates. Furthermore, based on the aforementioned slow and controllable reaction kinetics, this application can induce slow grain growth along a specific crystal orientation under relatively mild sintering conditions, directly generating primary particles without internal grain boundaries in situ. This eliminates the stress concentration effect caused by internal grain boundaries in traditional polycrystalline particles, improving the cathode material's resistance to microcracks during long-term cycling. Simultaneously, the pre-oxidation treatment and the nitride intermediate-mediated sintering process work synergistically: on the one hand, the pre-oxidation treatment effectively increases the valence state of nickel, reducing Li from the source. + / Ni 2+ The mixed arrangement of cations ensures the stability of the layered structure of the cathode material; on the other hand, the low-temperature sintering process avoids the loss of lithium source due to the ultra-high temperature sintering (>900℃) required by the traditional single crystallization strategy.

[0034] In summary, this application achieves the desired effect by reconstructing the solid-state reaction pathway of high-nickel ternary cathode materials, thereby suppressing the Li... + / Ni 2+While achieving cation mixing, the controllable preparation of single-crystal particles at low temperatures was realized, thereby significantly improving the capacity retention and cycle stability of the material. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic flowchart of a method for preparing a high-nickel ternary single-crystal cathode material according to one embodiment of this application.

[0037] Figure 2 This is a SEM image of the precursor in Embodiment 1 of this application.

[0038] Figure 3 This is a SEM image of the high-nickel ternary single-crystal cathode material prepared in Example 1 of this application.

[0039] Figure 4 This is a SEM image of the high-nickel ternary single-crystal cathode material prepared in Comparative Example 1 of this application. Detailed Implementation

[0040] A detailed reference is now provided to embodiments of this application, one or more of which are described below. Each embodiment is provided for explanation and not for limitation. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to this application without departing from its scope or spirit. For example, features described or illustrated as part of one embodiment may be used in another embodiment to produce further embodiments.

[0041] Therefore, this application is intended to cover such modifications and variations falling within the scope of the appended claims and their equivalents. Other objects, features, and aspects of this application are disclosed in or will be apparent from the following detailed description. It will be understood by those skilled in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this application.

[0042] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0043] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0044] In this article, when referring to units of data ranges, if a unit is only followed by the right endpoint, it means that the units of the left and right endpoints are the same.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0049] In this application, primary particles and secondary particles have the same meanings known in the art. "Primary particle" refers to a non-agglomerated particle. "Secondary particle" refers to an aggregated particle composed of two or more primary particles. Primary and secondary particles can be distinguished using scanning electron microscopy (SEM) images.

[0050] "Primary particle size" refers to the statistical result obtained by randomly selecting 100 primary particles as samples in the SEM image. The average value of the longest and shortest diagonals of each single crystal particle is taken as its particle size. SEM testing requires random sampling of primary particles and random selection of areas. The SEM image obtained from the test can represent the average level of high-nickel ternary single crystal cathode materials.

[0051] "Grain" refers to a single crystal or a single crystal in a single-crystal material, wherein the lattice of a single crystal is continuous and uninterrupted to its edge, and has no internal grain boundaries.

[0052] "Grain boundary" refers to a defect in the crystal structure of a grain. In polycrystalline materials, defects form an interface between two grains or microcrystals.

[0053] "Porosity" refers to the percentage of pore volume in a precursor to the total volume of the precursor under natural conditions.

[0054] "Particle size D10" refers to the particle size value corresponding to a cumulative particle size distribution percentage of 10%; "Particle size D50" refers to the particle size value corresponding to a cumulative particle size distribution percentage of 50%; and "Particle size D90" refers to the particle size value corresponding to a cumulative particle size distribution percentage of 90%. These values ​​can be measured using testing methods known in the art. For example, the national standard GB / T19077-2016 can be referenced, using a Malvern laser particle size analyzer for characterization testing.

[0055] "Diameter distance" refers to (D90-D10) / D50.

[0056] Specific surface area refers to the total surface area per unit mass of material. Specific surface area can be tested using methods well known to those skilled in the art. For example, the specific surface area of ​​a precursor can be calculated using the multi-point Brunauer-Emmett-Teller method after measuring the nitrogen isothermal adsorption-desorption curve of the material with a fully automated gas adsorption analyzer.

[0057] like Figure 1 As shown, in a first aspect, this application provides a method for preparing a high-nickel ternary single-crystal cathode material, comprising the following steps:

[0058] Provide a precursor; the general chemical formula of the precursor is Ni x Co y Mn 1-x-y (OH)₂, 0.8≤x≤0.96, 0.02≤y≤0.18; the porosity of the precursor is 30%-50%;

[0059] The precursor was mixed with a lithium source and nitrided under an ammonia atmosphere to prepare the nitrided product.

[0060] The nitriding product was pre-oxidized in an oxygen atmosphere to prepare the pre-oxidized product.

[0061] The pre-oxidized product was sintered in an oxygen atmosphere to obtain a high-nickel ternary single-crystal cathode material; the sintering temperature was 700℃-900℃.

[0062] This application utilizes the high porosity of a precursor to ensure the bulk uniformity of the nitriding modification, transforming the precursor into a nitride intermediate. The high activation energy of the nitride intermediate forms a kinetic barrier, effectively suppressing the instantaneous explosive reaction between the lithium source and the precursor. This facilitates a shift from traditional rapid diffusion control to slow nucleation-growth control, providing a sufficient time window for ordered atomic migration and lattice rearrangement. This solves the problems of uneven grain growth and internal defects caused by uncontrolled reaction rates.

[0063] Furthermore, based on the aforementioned slow and controllable reaction kinetics, this application can induce grains to grow slowly along a specific crystal orientation under relatively mild sintering conditions, directly generating primary particles without internal grain boundaries in situ, eliminating the stress concentration effect caused by internal grain boundaries in traditional polycrystalline particles, and improving the cathode material's resistance to microcracks during long-term cycling.

[0064] Simultaneously, the pre-oxidation treatment and the nitride intermediate-mediated sintering process work synergistically: on the one hand, the pre-oxidation treatment effectively increases the valence state of nickel, reducing Li from the source. + / Ni 2+ The mixed arrangement of cations ensures the stability of the layered structure of the cathode material; on the other hand, the low-temperature sintering process avoids the loss of lithium source due to the ultra-high temperature sintering (>900℃) required by the traditional single crystallization strategy.

[0065] In summary, this application achieves the desired effect by reconstructing the solid-state reaction pathway of high-nickel ternary cathode materials, thereby suppressing the Li... + / Ni 2+ While achieving cation mixing, the controllable preparation of single-crystal particles at low temperatures was realized, thereby significantly improving the capacity retention and cycle stability of the material.

[0066] Optionally, the porosity of the precursor is 30%, 35%, 40%, 45% or 50%, or the porosity of the precursor may be within the range of any two of the above porosities.

[0067] Within the porosity range of the aforementioned precursor, ensure that the nitriding reaction gas (e.g., ammonia) can flow smoothly and sufficiently through the gaps and interior of the material particles to guarantee the sufficiency of nitriding; at the same time, ensure the structural stability of the material during the nitriding process to prevent the formation of cracks.

[0068] In some embodiments, the particle size D50 of the precursor is 1.5 μm to 5 μm. Optionally, the particle size D50 of the precursor is 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, or the particle size D50 of the precursor may be within the range of any two of the above particle sizes D50.

[0069] Within the aforementioned precursor particle size D50 range, while suppressing precursor aggregation, it is beneficial for the precursor to obtain a uniform and controllable pore structure and a suitable specific surface area, ensuring reactivity while preventing excessively long diffusion paths for nitriding reaction gases (such as ammonia).

[0070] In some embodiments, the specific surface area of ​​the precursor is 10 m². 2 / g-30m 2 / g. Optionally, the specific surface area of ​​the precursor is 10m². 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g or 30m 2 / g, or the specific surface area of ​​the precursor can be within the range of any two specific surface areas mentioned above.

[0071] In some implementations, the precursor pitch is <0.7. This pitch ensures a narrower precursor particle size distribution, guarantees the synchronicity of the nitriding process of different precursor particles, and thus improves the structural uniformity of the high-nickel ternary single-crystal cathode material.

[0072] In some implementations, such as Figure 2 As shown, the precursor comprises secondary particles with a near-spherical morphology, which are formed by the aggregation of multiple primary particles that are shaped like thin strips or needles. These primary particles are arranged radially from the center of the secondary particles towards the outer periphery. This type of precursor structure facilitates the diffusion of ammonia gas along the pore channels into the interior of the particles.

[0073] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium acetate, lithium oxalate, and lithium citrate.

[0074] Optionally, the sintering temperature is 700°C, 750°C, 800°C, 850°C or 900°C, or the sintering temperature may be within any two of the above temperatures.

[0075] Furthermore, the sintering temperature is 780℃-850℃.

[0076] Within the temperature range of the above sintering treatment, grains are induced to grow slowly along a specific crystal orientation under relatively mild sintering conditions, directly generating primary particles without internal grain boundaries in situ, eliminating the stress concentration effect caused by internal grain boundaries in traditional polycrystalline particles; at the same time, it avoids the loss of lithium source due to ultra-high temperature sintering (>900℃) required by traditional single crystallization strategies.

[0077] In some embodiments, the holding time for sintering is 10h-24h. Optionally, the holding time for sintering is 10h, 15h, 20h, 22h or 24h, or the holding time for sintering can be within the range of any two of the above holding times.

[0078] In some embodiments, the molar ratio of lithium metal in the lithium source to the transition metal in the precursor is (1.01-1.2):1. Optionally, the molar ratio of lithium metal in the lithium source to the transition metal in the precursor is 1.01:1, 1.03:1, 1.06:1, 1.08:1, 1.1:1, or 1.2:1, or the molar ratio of lithium metal in the lithium source to the transition metal in the precursor may be within the range of any two of the above molar ratios.

[0079] In some embodiments, the ammonia flow rate is 0.05 m³ / s during the nitriding process. 3 / h-0.5m 3 / h. Optionally, the ammonia flow rate is 0.05m³ / h. 3 / h, 0.06m 3 / h, 0.07m 3 / h, 0.08m 3 / h, 0.09m 3 / h, 0.1m 3 / h, 0.2m 3 / h, 0.3m 3 / h, 0.4m 3 / h or 0.5m 3 / h, or the ammonia flow rate can be within the range of any two of the above flow rates.

[0080] In some embodiments, the nitriding treatment is performed at a temperature of 300°C to 500°C. Optionally, the nitriding treatment temperature is 300°C, 350°C, 400°C, 450°C, or 500°C, or the nitriding treatment temperature may be within any two of the above temperatures.

[0081] In some embodiments, the holding time for nitriding is 2h-10h. Optionally, the holding time for nitriding is 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, or the holding time for nitriding can be within any two of the above holding times.

[0082] Through the above nitriding treatment, the precursor (Ni) x Co y Mn 1-x-y (OH)₂, 0.8≤x≤0.96, 0.02≤y≤0.18) is converted into a nitriding intermediate. Because the Co-N / Mn-N bond energy is lower than the Co-O / Mn-O bond energy, the material's thermal stability decreases, providing a higher activation energy for subsequent reactions. This constructs a kinetic barrier on the material surface / interface, effectively suppressing direct contact between the lithium source and the precursor, avoiding instantaneous explosive reactions, and making the subsequent sintering process more gentle and controllable. Simultaneously, the gentle and uniform lithiation reaction, combined with the suppression of side reactions by the high energy barrier, effectively inhibits the nitriding of Li₂. + / Ni 2+ The mixing of cations ensures the stability of the layered structure of the cathode material.

[0083] The reaction formula for the nitriding process is shown in Equation 1 below:

[0084] .

[0085] In some embodiments, the pre-oxidation treatment temperature is 500°C-650°C. Optionally, the pre-oxidation treatment temperature is 500°C, 550°C, 600°C, or 650°C, or the pre-oxidation treatment temperature may be within the range of any two of the above temperatures.

[0086] In some embodiments, the holding time for the pre-oxidation treatment is 4-8 hours. Optionally, the holding time for the pre-oxidation treatment is 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, or the holding time for the pre-oxidation treatment may be within the range of any two of the above holding times.

[0087] In some implementations, the oxygen concentration is above 90%.

[0088] By nitriding the high-porosity precursor, a kinetic barrier was constructed using the weak Co-N / Mn-N bonds, suppressing the instantaneous burst behavior of subsequent reactions. Based on this, a pre-oxidation treatment was carried out at 500℃~650℃ in a high-concentration oxygen atmosphere for 4h~8h. Utilizing the mild oxidizing atmosphere and under the protection of the kinetic barrier, a slow phase transition was achieved, avoiding violent exothermic reactions, generating a highly reactive oxide intermediate, and initially constructing a layered structural framework. Most importantly, the pre-oxidation process effectively improved the valence state of transition metal elements, especially nickel (Ni). 2+ →Ni 3+ This reduces Li from the source. + / Ni 2+ The mixed arrangement of cations ensures the stability of the layered structure of the cathode material and improves the cycle stability and capacity retention of the cathode material.

[0089] In some embodiments, the primary particle size of the high-nickel ternary single-crystal cathode material is 0.5 μm-2 μm. Optionally, the primary particle size of the high-nickel ternary single-crystal cathode material is 0.5 μm, 0.8 μm, 1.5 μm, or 2 μm, or the primary particle size of the high-nickel ternary single-crystal cathode material may be within the range of any two of the above sizes.

[0090] In some implementations, the Li-type high-nickel ternary single-crystal cathode material + / Ni 2+ Cation mixing degree <2%.

[0091] Secondly, this application provides a high-nickel ternary single-crystal cathode material, which is prepared by any of the above-mentioned methods for preparing high-nickel ternary single-crystal cathode materials.

[0092] Thirdly, this application provides a cathode material, including the aforementioned high-nickel ternary single-crystal cathode material.

[0093] Specifically, the positive electrode sheet includes a positive current collector and a positive active layer disposed on at least one side of the surface of the positive current collector, wherein the positive active layer includes the aforementioned high-nickel ternary single-crystal positive electrode material.

[0094] In some embodiments, the positive electrode active layer further includes a positive electrode conductive agent and a positive electrode binder.

[0095] For example, the positive current collector includes metal foil and composite current collector; the composite current collector has a sandwich-like sandwich structure, with the middle polymer layer mainly composed of materials such as high molecular weight insulating resin, and metal layers deposited on both sides of the middle polymer layer by electroplating, chemical plating or other methods. Schematally, the high molecular weight resin includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, and cyclic polyolefins. The material is selected from one or more of the following: hydrocarbons, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone and its derivatives, sodium carboxymethyl cellulose, styrene-butadiene rubber, fluorinated rubber, polyvinyl alcohol, or polyvinylidene fluoride. The metal layer is selected from at least one of aluminum, copper, nickel, cobalt, tungsten, tin, lead, iron, silver, or gold. Further, the current collector is aluminum foil.

[0096] For example, the positive electrode conductive agent includes at least one of carbon nanotubes, conductive carbon, graphite, acetylene black, metal fibers, organic conductive polymers, graphene, conductive carbon black (super-P), Ketjen black, carbon dots, and carbon nanofibers.

[0097] For example, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol, polytetrafluoroethylene, sodium carboxymethyl cellulose, polyurethane, PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0098] Fourthly, this application provides a lithium-ion battery, including the aforementioned positive electrode.

[0099] Understandably, lithium-ion batteries also include a negative electrode, a separator, and an electrolyte.

[0100] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector, wherein the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent and a negative electrode binder.

[0101] For example, the negative electrode current collector can be a conventional metal foil or a composite current collector; for instance, a metal material can be disposed on a polymer substrate to form a composite current collector. As an example, the negative electrode current collector can be copper foil.

[0102] For example, the negative electrode active material includes, but is not limited to, one or more of artificial graphite, natural graphite, hard carbon materials, soft carbon, silicon-based materials, and tin-based materials. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds such as silicon suboxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. All of these materials are commercially available.

[0103] For example, the negative electrode conductive agent includes, but is not limited to, carbon-based materials, powdered nickel or other metal particles, or conductive polymers. Carbon-based materials may include particles such as carbon black, graphite, super-P, acetylene black (such as KETCHENTM black or DENKATM black), carbon fibers and nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene)polysulfonated styrene, etc.

[0104] For example, the negative electrode binder includes, but is not limited to, any one or a combination of at least two of the following: polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyoxymethylene (POM), polycarbonate (PC), polyamide (PA), acrylic plastics, other polyolefins and their copolymers, polysulfone, polyphenylene ether (PPO), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC).

[0105] It should be noted that this application does not impose any particular restriction on the type of diaphragm; any known porous diaphragm with good chemical and mechanical stability can be selected. As an example only, the diaphragm material can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular restriction. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular restriction.

[0106] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0107] For example, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0108] For example, the solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0109] In some embodiments, the electrolyte also includes additives. These additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance.

[0110] The following are specific embodiments. They are intended to provide a more detailed description of this application to help those skilled in the art and researchers better understand it. The technical conditions described do not constitute any limitation on this application. Any modifications made within the scope of the claims of this application are protected by the claims.

[0111] Unless otherwise stated, all raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0112] Example 1

[0113] This embodiment provides a high-nickel ternary single-crystal cathode material, and the preparation method is as follows:

[0114] (1) Provide a precursor. The precursor has the chemical formula Ni. 0.8 Co 0.1 Mn 0.1 (OH)₂, with a porosity of 40%, a particle size D50 of 4 μm, and a specific surface area of ​​21 m². 2 / g.

[0115] (2) Nitriding treatment: Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ and LiOH·H₂O were mixed and nitrided under an ammonia atmosphere to prepare the nitrided product. The molar ratio of lithium metal to transition metal was 1.05:1; the ammonia flow rate was 0.2 m³ / s. 3 / h, temperature is 450℃, and the heat preservation time is 5h.

[0116] (3) Pre-oxidation treatment: The above ammonia gas is switched to oxygen and kept at 550°C for 6 hours.

[0117] (4) Sintering treatment: continue heating to 780°C in oxygen and sinter for 20 hours to obtain high-nickel ternary single crystal cathode material.

[0118] The SEM image of the precursor used in this embodiment is as follows: Figure 2 As shown.

[0119] The SEM image of the high-nickel ternary single-crystal cathode material prepared in this embodiment is shown below. Figure 3 As shown, the primary particles of the high-nickel single-crystal cathode material have relatively uniform and regular morphology, small size, and less material agglomeration.

[0120] Example 2

[0121] This embodiment provides a high-nickel ternary single-crystal cathode material, and the preparation method is as follows:

[0122] (1) Provide a precursor. The precursor has the chemical formula Ni. 0.8 Co 0.1 Mn 0.1 (OH)₂, with a porosity of 30%, a particle size D50 of 1.5 μm, and a specific surface area of ​​10 m². 2 / g.

[0123] (2) Nitriding treatment: Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ and LiOH·H₂O were mixed and nitrided under an ammonia atmosphere to prepare the nitrided product. The molar ratio of lithium metal to transition metal was 1.01:1; the ammonia flow rate was 0.05 m³ / s. 3 / h, temperature is 300℃, and the heat preservation time is 2h.

[0124] (3) Pre-oxidation treatment: The above ammonia gas is switched to oxygen and kept at 500°C for 4 hours.

[0125] (4) Sintering treatment: continue heating to 700℃ in oxygen and sinter for 10h to obtain high-nickel ternary single crystal cathode material.

[0126] Example 3

[0127] This embodiment provides a high-nickel ternary single-crystal cathode material, and the preparation method is as follows:

[0128] (1) Provide a precursor. The precursor has the chemical formula Ni. 0.8 Co 0.1 Mn 0.1 (OH)₂, porosity 50%, particle size D50 5μm, specific surface area 30m² 2 / g.

[0129] (2) Nitriding treatment: Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ and LiOH·H₂O were mixed and nitrided under an ammonia atmosphere to prepare the nitrided product. The molar ratio of lithium metal to transition metal was 1.2:1; the ammonia flow rate was 0.5 m³ / s. 3 / h, temperature is 500℃, and the heat preservation time is 10h.

[0130] (3) Pre-oxidation treatment: The above ammonia gas is switched to oxygen and kept at 650°C for 8 hours.

[0131] (4) Sintering treatment: Continue heating in oxygen to 900℃ and sinter for 24h to obtain high-nickel ternary single crystal cathode material.

[0132] Example 4

[0133] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the porosity of the precursor in step (1) is 30% and the specific surface area is 12 m². 2 / g.

[0134] Example 5

[0135] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the porosity of the precursor in step (1) is 50% and the specific surface area is 28 m². 2 / g.

[0136] Example 6

[0137] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the sintering temperature in step (4) is 700℃.

[0138] Example 7

[0139] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the sintering temperature in step (4) is 850℃.

[0140] Example 8

[0141] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the sintering temperature in step (4) is 900℃.

[0142] Example 9

[0143] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that the chemical formula of the precursor is Ni. 0.96 Co 0.02 Mn 0.02 (OH)₂, with a porosity of 45%, a particle size D50 of 3.0 μm, and a specific surface area of ​​18 m². 2 / g.

[0144] Example 10

[0145] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that in step (2), the molar ratio of lithium metal to transition metal is 1.01:1.

[0146] Example 11

[0147] The preparation methods of this embodiment and Example 1 are basically the same, the main difference being that in step (2), the molar ratio of lithium metal to transition metal is 1.2:1.

[0148] Example 12

[0149] The preparation method of this embodiment is basically the same as that of Example 1, the main difference being that in step (2), the flow rate of ammonia is 0.05 m³ / s. 3 / h, temperature is 500℃, and the heat preservation time is 10h.

[0150] Example 13

[0151] The preparation method of this embodiment is basically the same as that of Example 1, the main difference being that in step (2), the flow rate of ammonia is 0.5 m³ / s. 3 / h, temperature is 300℃, and the heat preservation time is 2h.

[0152] Comparative Example 1

[0153] The preparation methods of this comparative example and Example 1 are basically the same, with the main difference being that the nitriding treatment step in step (2) is not included; and the sintering temperature in step (4) is 950℃, with sintering time of 20h. The SEM image of the high-nickel ternary single-crystal cathode material prepared in this comparative example is shown below. Figure 4 As shown, the material consists of single crystal particles with relatively large primary particle size and agglomeration.

[0154] Comparative Example 2

[0155] The preparation method of this comparative example is basically the same as that of Example 1, the main difference being that the nitriding treatment step in step (2) is not included. The prepared cathode material basically retains the spherical morphology of the precursor, and the interior is composed of multiple large single crystal grains aggregated into single crystal-like secondary particles.

[0156] Comparative Example 3

[0157] The preparation methods of this comparative example and Example 1 are basically the same, except that the pre-oxidation treatment step in step (3) is not included.

[0158] Comparative Example 4

[0159] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that the porosity of the precursor in step (1) is 20% and the specific surface area is 9m². 2 / g.

[0160] Comparative Example 5

[0161] The preparation methods of this comparative example and Example 1 are basically the same, the main difference being that the porosity of the precursor in step (1) is 60% and the specific surface area is 33m². 2 / g.

[0162] Test case

[0163] (1) The particle size and cation mixing degree of the high-nickel ternary cathode materials prepared in the examples and comparative examples were tested. The test results are shown in Table 1 below.

[0164] The primary particle size was determined by the following method: 100 primary particles were randomly selected from the SEM image as a sample to obtain statistical results. The longest and shortest diagonals of each single crystal particle were measured and the average value was taken as the primary particle size.

[0165] The cation mixing degree was determined by the following method: The XRD pattern of the high-nickel ternary single-crystal cathode material was measured using an X-ray diffractometer. The test conditions were: the X-ray source was Cu Kα rays, the scanning range was 10°-80°, the scanning rate was 1° / min, and the scanning step size was 0.02°. The cation mixing degree of the high-nickel ternary single-crystal cathode material was obtained by refining the image using the software Material Analysis Using Diffraction.

[0166] (2) The positive electrode materials prepared in the above examples and comparative examples were subjected to electrical performance tests according to the following methods: The positive electrode materials prepared above, polyvinylidene fluoride and conductive carbon black were added to N-methylpyrrolidone at a mass ratio of 90:5:5 and mixed into a slurry to obtain a paste; the slurry was coated on aluminum foil, dried and pressed to obtain a positive electrode sheet. Using lithium sheet as negative electrode sheet, the lithium sheet, PP separator and positive electrode sheet were assembled in the assembly order, and an electrolyte (LiPF6 electrolyte with a concentration of 1 mol / L, the solvent in the electrolyte being ethylene glycol dimethyl ether and propylene carbonate in a volume ratio of 1:1) was injected to make a button cell (CR2032).

[0167] The prepared battery was placed in the Blue Electric Test System and charged to 4.5V at a charging rate of 1C, and then discharged to 3.0V at a discharging rate of 1C. The cycle was repeated 500 times. The capacity retention rate was calculated as (discharge capacity on the 500th cycle / discharge capacity on the first cycle) × 100%. The average value of the three tests was taken. The results are shown in Table 1 below.

[0168] Table 1

[0169]

[0170] According to the comparison of Examples 1-3 and Comparative Examples 4-5 in Table 1, it can be seen that if the porosity of the precursor used is too high or too low, it is not conducive to the balance between nitriding sufficiency and structural stability, resulting in a decrease in the electrical performance of the high-nickel ternary single crystal cathode material.

[0171] according to Figure 3 and Figure 4 As can be seen from Example 1 and Comparative Examples 1-2 in Table 1, compared with Comparative Example 1, which did not perform a nitriding treatment step on the material and sintered the precursor at a high temperature above 900°C, and compared with Comparative Example 2, which did not perform a nitriding treatment step on the material, the cathode material prepared by the preparation method provided in this application has smaller size, better dispersion, and more uniform and regular morphology; and the cation mixing degree is lower, resulting in better electrical performance of the cathode material.

[0172] As can be seen from the comparison between Example 1 and Comparative Example 3 in Table 1, compared with Comparative Example 3 which did not perform a pre-oxidation treatment step on the material, the cathode material prepared by the preparation method provided in this application has a smaller size and a significantly reduced cation mixing degree, resulting in better electrical performance of the cathode material.

[0173] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0174] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a high-nickel ternary single-crystal cathode material, characterized in that, Includes the following steps: A precursor is provided; the general chemical formula of the precursor is Ni. x Co y Mn 1-x-y (OH)₂, 0.8≤x≤0.96, 0.02≤y≤0.18; the porosity of the precursor is 30%-50%; The precursor was mixed with a lithium source and subjected to nitriding treatment under an ammonia atmosphere to prepare a nitrided product. The nitriding product is pre-oxidized under an oxygen atmosphere to prepare a pre-oxidized product. The pre-oxidized product is sintered in an oxygen atmosphere to obtain the high-nickel ternary single-crystal cathode material; the sintering temperature is 700℃-900℃.

2. The method for preparing the high-nickel ternary single-crystal cathode material according to claim 1, characterized in that, The molar ratio of lithium metal in the lithium source to transition metal in the precursor is (1.01-1.2):

1.

3. The method for preparing the high-nickel ternary single-crystal cathode material according to claim 1, characterized in that, Nitriding treatment under an ammonia atmosphere must meet at least one of the following conditions: (1) The flow rate of the ammonia gas is 0.05 m³ / s. 3 / h-0.5m 3 / h; (2) The nitriding treatment temperature is 300℃-500℃; (3) The holding time for nitriding treatment is 2h-10h.

4. The method for preparing the high-nickel ternary single-crystal cathode material according to any one of claims 1-3, characterized in that, The precursor satisfies at least one of the following conditions: (1) The particle size D50 of the precursor is 1.5 μm to 5 μm; (2) The radial distance of the precursor is <0.7; (3) The specific surface area of ​​the precursor is 10 m². 2 / g-30m 2 / g; (4) The precursor includes secondary particles with a spherical morphology. The secondary particles are formed by the aggregation of multiple primary particles that are strip-shaped or needle-shaped. The multiple primary particles are arranged radially along the center of the secondary particles toward the outer periphery.

5. The method for preparing the high-nickel ternary single-crystal cathode material according to any one of claims 1-3, characterized in that, The pre-oxidation treatment satisfies at least one of the following conditions: (1) The temperature of the pre-oxidation treatment is 500℃-650℃; (2) The heat preservation time for the pre-oxidation treatment is 4h-8h.

6. The method for preparing the high-nickel ternary single-crystal cathode material according to any one of claims 1-3, characterized in that, The sintering process satisfies at least one of the following conditions: (1) The sintering temperature is 780℃-850℃; (2) The holding time for the sintering treatment is 10h-24h.

7. The method for preparing the high-nickel ternary single-crystal cathode material according to any one of claims 1-3, characterized in that, The high-nickel ternary single-crystal cathode material satisfies at least one of the following conditions: (1) The primary particle size is 0.5μm-2μm; (2) Cation mixing degree <2%.

8. A high-nickel ternary single-crystal cathode material, characterized in that, The high-nickel ternary single-crystal cathode material is prepared by the preparation method of the high-nickel ternary single-crystal cathode material according to any one of claims 1-7.

9. A positive electrode plate, characterized in that, Including the high-nickel ternary single-crystal cathode material as described in claim 8.

10. A lithium-ion battery, characterized in that, Includes the positive electrode as described in claim 9.

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