Preparation methods of ternary cathode materials, ternary cathode materials and lithium-ion batteries

Abstract

This invention discloses a method for preparing ternary cathode materials, the ternary cathode materials themselves, and lithium-ion batteries, relating to the field of lithium-ion battery technology. In this invention, nickel, cobalt, and manganese sources are ball-milled in the presence of a ball-milling aid. During the ball-milling process, the carboxyl groups (-COOH) of the organic acid coordinate with metal ions on the precursor surface under mechanical force, repeatedly impacting and shearing to disrupt the surface lattice order, inducing lattice distortion and oxygen vacancy defects, forming a surface activation layer. Subsequently, during calcination with lithium salts, the atomic arrangement in the defect regions becomes loose and bonding weakens, significantly increasing the lithium-ion diffusion rate, allowing the lithiation reaction to occur at lower temperatures. Simultaneously, the activation layer provides uniform nucleation sites, promoting uniform growth of single-crystal particles. Therefore, the preparation method provided by this invention can achieve low-temperature synthesis while preparing large-size single-crystal products.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a method for preparing ternary cathode materials, ternary cathode materials, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, due to their high energy density and long cycle life, have become core components for new energy vehicles and large-scale energy storage. Cathode materials account for 20% to 30% of the total battery cost, and their performance directly determines the battery's energy density and lifespan. Single-crystal ternary materials, with their high specific capacity and excellent structural stability, have become the mainstream cathode material for power batteries.

[0003] Currently, the mainstream industrial route for single-crystal ternary materials is liquid-phase co-precipitation combined with high-temperature lithiation: that is, firstly, a hydroxide precursor is prepared by co-precipitation, and then it is mixed with a lithium source and calcined. This method is technically mature, but the process is lengthy, the equipment investment is high, and the co-precipitation process generates a large amount of ammonia-containing wastewater / waste gas, which does not conform to the concept of green and sustainable development. The all-dry method can directly ball-mill and mix the raw materials and calcin to obtain single-crystal ternary materials, which has the characteristics of simple process, zero ammonia nitrogen emission, and significant cost advantage. However, the all-dry solid-phase synthesis of ternary materials faces two major bottlenecks: (1) High lithiation temperature: transition metal oxides are thermodynamically stable, and the diffusion resistance of lithium ions in the solid phase is large. It is necessary to reach above 900℃ to form a good layered structure; (2) Difficulty in single-crystal particle growth: after the lithium salt melts at high temperature, it reacts with the precursor in a solid-liquid reaction. Due to the limited mixing uniformity, the reaction is concentrated in the local area of ​​the particle surface, and the final product is mostly agglomerated small particles with low tap density.

[0004] To address the above issues, existing improvement strategies mainly fall into two categories: (1) Increase the calcination temperature / extend the holding time. This method can accelerate the lithiation and particle coarsening rate of ternary materials, but excessively high calcination temperature will cause the Li / Ni mixing of layered materials to intensify, lattice oxygen loss, and is not conducive to electrochemical performance; (2) Introducing molten salts or sintering aids. The molten salt strategy utilizes low-melting-point salts to form a liquid phase at high temperatures, which can significantly accelerate mass transport and reduce reaction temperature. However, molten salt residues in the product are difficult to remove completely and often require an additional water washing process, which weakens the advantages of the all-dry synthesis. Sintering aids (such as Sr, Ce, Bi, etc.) can promote grain growth and improve particle size, but their effect on accelerating the lithiation reaction is limited.

[0005] In summary, how to overcome the inherent defects of high lithiation temperature and fine product particles from the source while preserving the green and low-cost nature of the all-dry process, and achieve a synergistic breakthrough in "low-temperature synthesis" and "large-size single crystals", has become a key technical problem that urgently needs to be solved in this field.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing ternary cathode materials, ternary cathode materials, and lithium-ion batteries, aiming to achieve low-temperature synthesis while preparing large-size single-crystal products.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a ternary cathode material, comprising: ball milling a nickel source, a cobalt source and a manganese source in the presence of a ball milling aid to obtain a lithium-free precursor; wherein the ball milling aid is an organic acid; The lithium-free precursor was mixed with a lithium source and then calcined.

[0009] This invention introduces organic acids during the ball milling stage to induce lattice distortion and oxygen vacancy defects, forming a surface activation layer. During subsequent calcination with a lithium source, the atomic arrangement in the defect region becomes looser, and bonding weakens, significantly increasing the lithium-ion diffusion rate and allowing the lithiation reaction to occur at a lower temperature. Simultaneously, the activation layer provides uniform nucleation sites, promoting uniform growth of single crystal particles.

[0010] In an optional embodiment, the organic acid has a pKa of 1-6, where Ka represents the dissociation constant; Preferably, the organic acid is selected from at least one of oxalic acid, citric acid, tartaric acid, acetic acid, malic acid, and ethylenediaminetetraacetic acid; More preferably, the organic acid is selected from at least one of oxalic acid and citric acid.

[0011] If the acid is too strong, it will corrode the material. The inventor was unable to obtain a single-crystal cathode material product after trying it.

[0012] In an optional embodiment, the molar amount of the organic acid is 1%-5% of the total molar amount of nickel, cobalt, and manganese; And / or, the area of ​​the oxygen vacancy characteristic peak at 531.2~531.8 eV in the XPS O 1s spectrum of the lithium-free precursor accounts for 15%-45%.

[0013] In an optional implementation, during the ball milling process, the rotation speed is controlled at 100 rpm to 1000 rpm, and the ball milling time is 2 h to 15 h. And / or, control the ball-to-material ratio to be (10-15):1; And / or, the atmosphere of the ball mill is air or an inert atmosphere; And / or, the ball milling equipment is a planetary high-energy ball milling equipment.

[0014] In an optional implementation, grinding media are added before ball milling; Preferably, the grinding media is selected from at least one of ethanol and acetone; Preferably, the mass ratio of the grinding media to the total mass of the nickel source, cobalt source and manganese source is (10-20):100.

[0015] In an optional embodiment, the calcination temperature is 750℃-900℃, and the holding time is 8h-20h; And / or, calcination is carried out in an oxygen-containing atmosphere.

[0016] In an optional implementation, the molar ratio of lithium to the total amount of nickel, cobalt, and manganese in the lithium source is controlled to be 1.02-1.10; And / or, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate and lithium acetate.

[0017] In an optional embodiment, the nickel source is selected from at least one of nickel oxide, nickel hydroxide, nickel carbonate, and nickel oxalate, preferably nickel oxide; And / or, the cobalt source is selected from at least one of cobalt(II) oxide, cobalt(III) oxide, cobalt(IV) oxide, cobalt(III) hydroxide, cobalt(IV) carbonate and cobalt(IV) oxalate, preferably at least one of cobalt(II) oxide, cobalt(III) oxide and cobalt(IV) oxide; And / or, the manganese source is selected from at least one of manganese trioxide, manganese tetroxide, manganese dioxide, manganese hydroxide, manganese carbonate and manganese oxalate, preferably at least one of manganese trioxide, manganese tetroxide and manganese dioxide; And / or, by adjusting the amounts of nickel, cobalt and manganese sources, the molar ratio of nickel, cobalt and manganese is (0.6-0.90):(0.05-0.3):(0.05-0.3).

[0018] Secondly, the present invention provides a ternary cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0019] Thirdly, the present invention provides a lithium-ion battery comprising the ternary cathode material of the aforementioned embodiments.

[0020] This invention offers the following advantages: Nickel, cobalt, and manganese sources are ball-milled in the presence of a ball-milling aid. During the milling process, the carboxyl groups (-COOH) of the organic acid coordinate with metal ions on the precursor surface under mechanical force, repeatedly impacting and shearing to disrupt the surface lattice order, inducing lattice distortion and oxygen vacancy defects, forming a surface activation layer. Subsequent calcination with lithium salts results in a looser atomic arrangement and weaker bonding in the defect regions, significantly increasing the lithium-ion diffusion rate and allowing the lithiation reaction to occur at lower temperatures. Simultaneously, the activation layer provides uniform nucleation sites, promoting uniform growth of single crystal particles. Therefore, the preparation method provided by this invention can achieve low-temperature synthesis while simultaneously preparing large-size single crystal products. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The images shown are SEM images of the ball-milled product obtained in Example 1 of this invention; (a) and (b) represent different magnification ratios. Figure 2 SEM images of the single-crystal ternary material prepared in Example 1 of this invention; (a) and (b) represent different magnification ratios; Figure 3 The XRD pattern of the single-crystal ternary material prepared in Example 1 of this invention; Figure 4 This is the first charge-discharge curve of the single-crystal ternary material prepared in Example 1 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the range referred to.

[0025] In the description of this invention, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0026] This invention optimizes the solid-state method for preparing ternary cathode materials. By introducing organic acids during the ball milling stage, lattice distortion and oxygen vacancy defects are induced, forming a surface activation layer. During subsequent calcination with a lithium source, the atomic arrangement in the defect region is looser, bonding is weakened, and the lithium-ion diffusion rate is significantly improved, allowing the lithiation reaction to occur at a lower temperature. Simultaneously, the activation layer provides uniform nucleation sites, promoting the uniform growth of single-crystal particles. Through process optimization, this invention can produce large-size single-crystal products while reducing calcination temperature. It is a green and low-cost preparation process with excellent prospects for industrial application.

[0027] This invention provides a method for preparing a ternary cathode material, which is a dry solid-state synthesis method for single-crystal ternary cathode material using a ball milling aid to activate the precursor. The chemical formula of the synthesized single-crystal ternary cathode material is LiNi. x Co y Mn z O2 (x+y+z=1, x≥0.6).

[0028] S1, ball mill Nickel, cobalt, and manganese sources were mixed in a ternary stoichiometric ratio and placed in a ball mill jar. A ball milling aid and grinding media were added, and high-energy ball milling was performed. After ball milling, a lithium-free precursor with a surface rich in lattice defects and oxygen vacancies was obtained. The ball milling aid was an organic acid.

[0029] It should be noted that during high-energy ball milling, the carboxyl groups (-COOH) of the organic acid coordinate with metal ions on the precursor surface under mechanical force, repeatedly impacting and shearing to disrupt the surface lattice order, inducing lattice distortion and oxygen vacancy defects, forming a surface activation layer. During subsequent calcination with lithium salts, the atomic arrangement in the defect regions becomes loose and bonding weakens, significantly increasing the lithium-ion diffusion rate, allowing the lithiation reaction to occur at a lower temperature. Simultaneously, the activation layer provides uniform nucleation sites, promoting uniform growth of single crystal particles.

[0030] In optional embodiments of the present invention, the pKa of the organic acid is 1-6, such as 2, 3, 4, 5, 6, etc., or any value among the above adjacent values. Wherein, Ka represents the dissociation equilibrium constant of the acid, reflecting the ionization of a weak acid into H+ in water. + The smaller the Ka value, the weaker the acidity. pKa = The larger the lgKa and pKa values, the weaker the acidity. pKa can be tested using conventional methods, and standard data can be directly consulted. For example, at 25°C, the pKa1 of oxalic acid is approximately 1.2, the pKa1 of citric acid is approximately 3.13, and the pKa1 of acetic acid is approximately 4.76.

[0031] It should be added that if strong organic acids are used, they will corrode the surface of the raw materials during ball milling, causing dissolution and peeling. The raw materials for nickel, cobalt, and manganese sources are mostly basic / amphoteric oxides, and strong organic acids will dissociate to release H+. + A typical acid-base reaction occurs.

[0032] In optional embodiments of the present invention, the organic acid is selected from at least one of oxalic acid, citric acid, tartaric acid, acetic acid, malic acid and ethylenediaminetetraacetic acid. The organic acid can be any one or more of the above, and can be one, such as oxalic acid, citric acid, tartaric acid, acetic acid, malic acid or ethylenediaminetetraacetic acid alone, or a combination of two, three, four, five or six kinds.

[0033] In a preferred embodiment, the organic acid is selected from at least one of oxalic acid and citric acid. The organic acid can be any one or more of the above. When the organic acid is one or more of the above, it can further improve the performance of the cathode material and improve the electrochemical performance of the battery.

[0034] Furthermore, the molar amount of organic acid is 1%-5% of the total molar amount of nickel, cobalt, and manganese. For example, it can be 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.0%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, etc., or any value from the above adjacent ranges. In other words, the molar amount of organic acid added is 1%-5% of the total molar amount of nickel, cobalt, and manganese. If too little organic acid is added, not enough oxygen vacancy defects will be formed, which is not conducive to improving the lithium-ion diffusion rate and requires a higher calcination temperature. If too much organic acid is added, too many oxygen vacancy defects will be formed, which will destroy the cation order of the layered structure (exacerbate Li / Ni mixing), thereby reducing the long-term stability of the crystal structure and ultimately deteriorating the electrochemical cycle life of the material.

[0035] In an optional embodiment of the present invention, the nickel source is selected from at least one of nickel oxide, nickel hydroxide, nickel carbonate and nickel oxalate. The nickel source can be any one or more of the above, that is, it can be a single nickel source or a combination of two, three or four nickel sources, preferably nickel oxide.

[0036] In optional embodiments of the present invention, the cobalt source is selected from at least one of cobalt(II) oxide, cobalt(III) oxide, cobalt(IV) oxide, cobalt hydroxide, cobalt carbonate, and cobalt oxalate. The cobalt source can be any one or more of the above, i.e., it can be a single cobalt source, or a combination of two, three, four, five, or six cobalt sources. Preferably, the cobalt source is selected from at least one of cobalt(II) oxide, cobalt(III) oxide, and cobalt(IV) oxide, and more preferably, it is any one of the above, or a combination of two or three.

[0037] In optional embodiments of the present invention, the manganese source is selected from at least one of manganese trioxide, manganese tetroxide, manganese dioxide, manganese hydroxide, manganese carbonate, and manganese oxalate. The manganese source can be any one or more of the above, that is, it can be a single manganese source, or a combination of two, three, four, five, or six manganese sources. Preferably, the manganese source is selected from at least one of manganese trioxide, manganese tetroxide, and manganese dioxide, and the manganese source is preferably any one of the above, or a combination of two or three.

[0038] The specific types of nickel, cobalt, and manganese sources can be quite broad, with their oxide forms being preferred, although other forms also have the same activation effect.

[0039] Furthermore, by adjusting the amounts of nickel, cobalt, and manganese sources, the molar ratio of nickel, cobalt, and manganese can be made as (x=0.6-0.90):(y=0.05-0.3):(z=0.05-0.3), where x + y + z = 1. The ratio can be determined based on the chemical formula of the ternary cathode material. For example, it could be NCM622, Ni:Co:Mn=6:2:2 (0.6:0.2:0.2); or NCM721, Ni:Co:Mn=7:2:1 (0.7:0.2:0.1); or NCM811, Ni:Co:Mn=8:1:1 (0.8:0.1:0.1).

[0040] In an optional embodiment of the present invention, during the ball milling process, the rotation speed is controlled to be 100rpm-1000rpm, such as 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm, 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm, etc., or any value among the above adjacent values; the ball milling time is 2h-15h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc., or any value among the above adjacent values.

[0041] It should be noted that if the rotation speed is too low, the centrifugal force of the grinding balls is insufficient, the lifting height is not enough, the impact force and shear force are greatly weakened, the powder crushing and de-agglomeration effect is poor, large particles and agglomerates cannot be dispersed, and the particle size is too large and the distribution is uneven. If the rotation speed is too high, the grinding balls obtain a great centrifugal force, adhere to the tank wall and rotate synchronously with the tank, and no longer fall or impact effectively (similar to the critical speed phenomenon of ordinary ball mills), and the grinding efficiency will decrease instead.

[0042] It should be noted that if the ball milling time is too short, the energy accumulation will be insufficient, the particle refinement will not meet the standard, the agglomerates will not be completely broken up, and the particle size and distribution will be unqualified. If the ball milling time is too long, the particles will be over-refined, and the surface energy of the ultrafine particles will be high, causing them to re-agglomerate and form hard agglomerates, which will be even more difficult to disperse. In addition, continuous mechanical force will damage the crystal structure, resulting in too many lattice defects, damage to the layered structure of the ternary material, and degradation of electrochemical performance. Prolonged friction and heating will cause a large amount of liquid solvent to evaporate, and the system will gradually turn into a dry grinding state, exacerbating dust and wear.

[0043] The type of ball milling equipment used is not limited, such as a planetary high-energy ball mill. The core of a planetary high-energy ball mill is the planetary composite motion of revolution and rotation. Strong centrifugal force (far greater than gravity) causes the grinding balls to collide, shear, and squeeze at high frequency and high speed inside the jar, achieving ultrafine / nano-grinding and mechanical alloying.

[0044] In an optional embodiment of the present invention, during the ball milling stage, the ball-to-material ratio is controlled to be (10-15):1, such as 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc., or any value among the above adjacent values. The atmosphere for ball milling can be air or an inert atmosphere, such as nitrogen or argon.

[0045] In an optional embodiment of the present invention, a small amount of grinding media is added before ball milling. The type of grinding media is not limited and can be a common organic solvent, such as NMP (N-methylpyrrolidone), anhydrous ethanol (EtOH), acetone, isopropanol (IPA), etc., but is not limited thereto. Preferably, the grinding media is selected from at least one of ethanol and acetone, and the grinding media can be any one or a combination of two of the above. The mass ratio of the grinding media to the total mass of the nickel source, cobalt source, and manganese source is (10-20):100, such as 10:100, 13:100, 15:100, 18:100, 20:100, etc. The amount of grinding media used should be within the above range to make the ball milling more uniform.

[0046] Specifically, the addition of grinding media can isolate the dry friction between particles and grinding balls, reduce excessive powder refinement and wear of grinding balls / cans, and reduce the introduction of metal impurities; it can also prevent fine particles from re-adsorbing and agglomerating, maintaining a dispersed state; it can also completely suppress dust emission, and wet grinding of flammable and explosive powders and ultrafine powders can significantly reduce the risk of combustion and explosion; it can also improve powder flowability, making the components more uniformly mixed; and it can also remove the frictional heat and impact heat generated by ball milling, avoiding local high temperature from causing powder phase transformation and lithium salt decomposition.

[0047] Specifically, the type of grinding balls is not limited, such as zirconium oxide, stainless steel, agate, alumina, etc. The functions of grinding balls are: (1) Particle crushing and refining. High-speed impact, extrusion, and shearing force break up agglomerates and large particles, reduce particle size, optimize particle size distribution, and adapt to the requirements of electrode powder. (2) De-agglomeration. Disperse soft and hard agglomerates of powder, so that the primary particles are fully dispersed, and avoid particle lumps and pinholes in electrode coating. (3) Mechanical activation / surface modification. Under high-energy ball milling, the impact of grinding balls causes lattice defects on the particle surface and improves surface activity; which is beneficial to subsequent sintering reaction and slurry wetting. (4) Uniform mixing. Multi-component powder (active material + conductive agent + lithium source precursor) is fully mixed to ensure uniform composition and avoid local proportion deviation. (5) Particle morphology control. Friction and rolling can grind the edges of particles, achieve sphericity to a certain extent, and improve the compaction density and fluidity of powder.

[0048] Tests showed that the area percentage of the oxygen vacancy characteristic peak at 531.2~531.8 eV in the XPS O 1s spectrum of the lithium-free precursor obtained after ball milling was 15%-45%, which could be 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., or any value among the above adjacent values.

[0049] S2, calcination The lithium-free precursor and the lithium source are directly mixed evenly and placed in an atmosphere furnace for calcination. After calcination and cooling, a single-crystal ternary cathode material is obtained.

[0050] In an optional embodiment of the present invention, the calcination temperature is 750℃-900℃, such as 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, etc., or any value among the above adjacent values; the heat preservation time is 8h-20h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, etc., or any value among the above adjacent values. If the calcination temperature is too high or the holding time is too long, such as exceeding 900℃, lithium / oxygen will be lost from the layered material, which will harm the electrochemical performance and increase energy consumption. If the calcination temperature is too low or the holding time is too short, such as less than 750℃, it will be impossible to obtain an ordered layered structure and dispersed single-crystal ternary cathode material, which will significantly reduce the electrochemical performance of the battery.

[0051] In an optional embodiment of the present invention, the molar ratio (Li / TM) of lithium to nickel, cobalt, and manganese in the lithium source is controlled to be 1.02-1.10, such as 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.10, etc., or any value among the above adjacent values. That is, the molar ratio of lithium to the total molar amount of nickel, cobalt, and manganese is (1.02-1.10):1. A slight excess of lithium is preferable, which can compensate for the volatilization of lithium during high-temperature sintering, replenish the lithium in the lattice, suppress cation mixing, and improve capacity and cycling performance. However, lithium is generally in slight excess (≤1.10) to prevent the formation of free residual alkali on the surface and avoid gas expansion, slurry failure, and interface deterioration.

[0052] Specifically, the amount of lithium added varies slightly depending on the ratio of nickel, cobalt, and manganese. For example, NCM622 controls the Li / TM ratio to be 1.08-1.10; NCM721 controls the Li / TM ratio to be 1.06-1.08; and NCM811 / NCA controls the Li / TM ratio to be 1.02-1.05.

[0053] In an optional embodiment of the present invention, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium acetate. The lithium source can be any one of the above, any combination of any two of the above, or a combination of the above three.

[0054] This invention provides a ternary cathode material, which is prepared by the preparation method provided in this invention. It is a single-crystal high-nickel ternary cathode material, and is also a ternary product with ordered layered structure and uniform single-crystal dispersion, which endows it with high specific capacity and long cycle life from the material source.

[0055] This invention also provides a positive electrode sheet, which is prepared using the ternary positive electrode material. Optimization of the ternary positive electrode material is beneficial to improving the electrode sheet performance.

[0056] Specifically, the positive current collector used to prepare the positive electrode sheet can be aluminum foil (Al) or carbon-coated aluminum foil, but is not limited to these. The thickness of the positive current collector can be 12μm, 15μm, or 20μm.

[0057] Specifically, a positive electrode active slurry is obtained by mixing a ternary cathode material with a conductive agent, a binder, and a dispersant. The positive electrode active slurry is then coated onto one or both sides of the positive electrode current collector, followed by drying and rolling. By mass fraction, the ternary cathode material comprises 92%-96%, the binder 2%-4%, the conductive agent 2%-4%, and the dispersant amount is unlimited. The binder can be PVDF, but is not limited to it. The conductive agent can be at least one of carbon black and carbon nanotubes.

[0058] This invention also provides a lithium-ion battery, including the ternary cathode material provided in this invention, which is used to assemble the battery with a cathode, a separator, and an electrolyte.

[0059] Specifically, the negative electrode sheet is also made by coating a negative electrode active slurry onto a negative electrode current collector, followed by drying and rolling. The negative electrode current collector can be copper foil (Cu), with a thickness of 6μm, 8μm, or 10μm. The negative electrode active slurry is obtained by mixing a negative electrode active material, a conductive agent, a binder, and a solvent. The negative electrode active material can be graphite; the conductive agent can be conductive carbon black, carbon nanotubes, graphene, etc.; the binder can be sodium carboxymethyl cellulose and styrene-butadiene rubber latex; and the solvent can be N-methylpyrrolidone.

[0060] Specifically, the diaphragm can be PE (polyethylene) or PP (polypropylene), but is not limited to these.

[0061] Specifically, the electrolyte is a complex system of lithium salt, organic solvent, and functional additives, which directly determines the battery's voltage platform, cycle life, rate capability, low-temperature performance, and safety performance. The lithium salt can be LiPF6 (lithium hexafluorophosphate); the organic solvent can be EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), or DEC (diethyl carbonate), preferably a ternary mixture of EC, DMC, and EMC; the functional additive can be, for example, VC (ethylene carbonate), which forms a stable SEI film on the negative electrode surface, reduces interfacial impedance, and improves cycle life, and is commonly used in ternary batteries.

[0062] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0063] Example 1 (Oxalic Acid System) This embodiment provides a method for preparing a ternary cathode material, the steps of which are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0064] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0065] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are as follows: The single-crystal high-nickel ternary cathode material obtained in step (2), conductive carbon black (Super-P), and polyvinylidene fluoride (PVDF) were weighed and mixed at a mass ratio of 8:1:1 (e.g., 160 mg of cathode material, 20 mg of Super-P, and 20 mg of PVDF). The mixture was then ground in a mortar for 10 min, transferred to a small beaker, and an appropriate amount of N-methylpyrrolidone (NMP) was added. The mixture was sealed and stirred for 1 h to obtain a uniform cathode slurry. The slurry was coated onto aluminum foil, dried under vacuum at 120℃ for 10 h, rolled, and then cut into circular cathode sheets with a diameter of 12 mm for later use.

[0066] A CR2032 coin cell was assembled in an argon-filled glove box using a lithium electrode as the counter electrode, a porous polypropylene membrane as the separator, and a 1 mol / L LiPF6 / EC-EMC-DMC (1:1:1, volume ratio) electrolyte, in the following order: positive electrode shell, positive electrode plate, separator, lithium electrode plate, gasket, spring contact, and negative electrode shell. After standing for 12 hours, a constant current charge-discharge test was performed, with a voltage window of 2.8–4.3 V.

[0067] Example 2 (only the molar ratios of Ni, Co, and Mn are different) Compared to Example 1, in Example 2, the molar ratio of NiO, Co3O4, and MnO2 during ball milling was Ni:Co:Mn = 60:20:20, and the corresponding single-crystal ternary material had the chemical formula LiNi. 0.6 Co 0.2 Mn 0.2 O2.

[0068] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=60:20:20, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0069] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.6 Co 0.2 Mn 0.2 O2 materials.

[0070] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0071] Example 3 (only the molar ratios of Ni, Co, and Mn are different) Compared to Example 1, in Example 3, the molar ratio of NiO, Co3O4, and MnO2 during ball milling was Ni:Co:Mn = 70:10:20, and the corresponding single-crystal ternary material had the chemical formula LiNi. 0.7 Co 0.1 Mn 0.2 O2.

[0072] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=70:10:20, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0073] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.7 Co 0.1 Mn 0.2 O2 materials.

[0074] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0075] Example 4 (Expanding the types of ball milling aids - citric acid) Compared with Example 1, the auxiliary agent used in the ball milling of Example 4 is citric acid, and the rest of the preparation process is the same as that of Example 1.

[0076] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% citric acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0077] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0078] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0079] Example 5 (Oxalic acid addition 5%) Compared with Example 1, the oxalic acid content added during ball milling in Example 5 was 5%. The above precursor was mixed with LiOH·H2O at Li / TM=1.04, placed in an atmosphere furnace, and the calcination temperature was reduced to 780°C and held for 15 hours. The other conditions were the same as in Example 1.

[0080] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0081] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 780℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 15 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0082] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0083] Example 6 (Oxalic acid addition 5%) Compared to Example 1, the oxalic acid content added during ball milling in Example 6 was 5%.

[0084] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0085] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0086] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0087] Example 7 (1% oxalic acid added) Compared to Example 1, the oxalic acid content added during ball milling in Example 7 was 1%.

[0088] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0089] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0090] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0091] Example 8 (Oxalic acid addition: 0.5%) Compared to Example 1, the oxalic acid content added during ball milling in Example 8 was 0.5%.

[0092] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 0.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0093] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0094] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0095] Example 9 (7% oxalic acid added) Compared with Example 1, the oxalic acid content added during ball milling in Example 9 was 7%.

[0096] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 7mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0097] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0098] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0099] Example 10 (Organic Acid Modification) Compared to Example 1, Example 10 replaces oxalic acid with tartaric acid.

[0100] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% tartaric acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0101] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0102] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0103] Example 11 (Organic Acid Modification) Compared to Example 1, Example 11 replaces oxalic acid with acetic acid.

[0104] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% acetic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0105] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0106] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0107] Example 12 (Organic Acid Modification) Compared to Example 1, Example 12 replaces oxalic acid with malic acid.

[0108] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% malic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0109] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0110] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0111] Example 13 (Organic Acid Modification) Compared to Example 1, Example 13 replaces oxalic acid with ethylenediaminetetraacetic acid.

[0112] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4, and MnO2 in a molar ratio of Ni:Co:Mn = 83:11:6, with a total mass of 500g. Add 1.5mol% ethylenediaminetetraacetic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0113] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0114] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0115] Example 14 (Change of ball milling conditions) Compared to Example 1, Example 14 changed the ball milling conditions.

[0116] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4, and MnO2 in a molar ratio of Ni:Co:Mn = 83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 10:1, speed of 100 rpm, and ball mill for 15 hours in a nitrogen atmosphere to obtain the defective precursor.

[0117] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0118] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0119] Example 15 (Change of ball milling conditions) Compared to Example 1, Example 15 changed the ball milling conditions.

[0120] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4, and MnO2 in a molar ratio of Ni:Co:Mn = 83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 15:1, speed of 1000 rpm, and ball mill for 2 hours in a nitrogen atmosphere to obtain the defective precursor.

[0121] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 820℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0122] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0123] Example 16 (Comprehensive modification of calcination conditions) Compared with Example 1, Example 16 changed the calcination temperature, time and amount of lithium source.

[0124] (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0125] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.01, place it in an atmosphere furnace, heat it to 750℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 20 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0126] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0127] Example 17 (Comprehensive modification of calcination conditions) Compared with Example 1, Example 17 changed the calcination temperature, time and amount of lithium source.

[0128] (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0129] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.08, place it in an atmosphere furnace, heat it to 900℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 8 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0130] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0131] Example 18 (Calming temperature varied) Compared with Example 1, Example 18 changed the calcination temperature.

[0132] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0133] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 750℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0134] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0135] Example 19 (Calming temperature varied) Compared with Example 1, Example 19 changed the calcination temperature.

[0136] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0137] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 900℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0138] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0139] Example 20 (Calming temperature varied) Compared with Example 1, Example 20 changed the calcination temperature.

[0140] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0141] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 700℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0142] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0143] Example 21 (Changing the calcination temperature) Compared with Example 1, Example 21 changed the calcination temperature.

[0144] The specific steps in this embodiment are as follows: (1) Mix NiO, Co3O4 and MnO2 in a molar ratio of Ni:Co:Mn=83:11:6, with a total mass of 500g. Add 1.5mol% oxalic acid and 15wt% ethanol (75g), place in a zirconia ball mill jar, ball-to-material ratio of 12:1, speed of 350 rpm, and ball mill for 6 hours in a nitrogen atmosphere to obtain the defective precursor.

[0145] (2) Take the above precursor and mix it with LiOH·H2O at Li / TM=1.04, place it in an atmosphere furnace, heat it to 1000℃ at 3℃ / min under an oxygen atmosphere, hold it at that temperature for 12 hours, cool it naturally, and sieve it to obtain single crystal LiNi. 0.83 Co 0.11 Mn 0.06 O2 materials.

[0146] The ternary cathode material prepared in this embodiment is assembled into a battery, and the steps are the same as in Example 1.

[0147] Comparative Example 1 (without ball milling aid) Compared with Example 1, Comparative Example 1 used the same oxide raw material ratio and underwent high-energy ball milling (parameters same as Example 1), but no ball milling aid was added, and the rest of the preparation process was the same as Example 1.

[0148] Comparative Example 2 (without ball milling aid) Compared with Example 2, Comparative Example 2 used the same oxide raw material ratio and underwent high-energy ball milling (parameters same as Example 2), but no ball milling aid was added, and the rest of the preparation process was the same as Example 2.

[0149] Comparative Example 3 (without ball milling aid) Compared with Example 3, Comparative Example 3 used the same oxide raw material ratio and underwent high-energy ball milling (parameters same as Example 3), but no ball milling aid was added, and the rest of the preparation process was the same as Example 3.

[0150] Comparative Example 4 (no ball milling process, no additives) Compared with Example 1, the same oxide raw material ratio was used, and no ball milling aids were added; only low-speed mechanical mixing (20 rpm) was performed.

[0151] Comparative Example 5 (Conventional sintering aid - Bi2O3) Compared with Example 1, the same oxide raw material ratio was used, but no ball milling aid was added, and 1.0 wt% Bi2O3 was added as a sintering aid in the lithium mixing stage. The rest of the preparation process was the same as in Example 1.

[0152] Comparative Example 6 (Conventional sintering aid - CeO2) Compared with Example 1, the same oxide raw material ratio was used, but no ball milling aid was added, and 1.0 wt% CeO2 was added as a sintering aid in the lithium mixing stage. The rest of the preparation process was the same as in Example 1.

[0153] Comparative Example 7 (using a strong acid as a ball milling aid) Compared to Example 1, oxalic acid was replaced with the same molar mass of p-toluenesulfonic acid (pKa = -2.8).

[0154] Experimental Example 1 The lithium-free precursor and ternary cathode material prepared in Example 1 were characterized, such as... Figures 1-4 As shown in Table 1-2.

[0155] Table 1. Oxygen-vacancy ratios of precursors used in each embodiment and comparative example.

[0156] Table 2: Electrochemical performance of cathode materials obtained in each embodiment and comparative example

[0157] Figure 1 The image shows an SEM image of the product after ball milling in Example 1 of this invention. As can be seen from the image, the precursor particles are finer and a distinct defect layer is formed on the surface after high-energy ball milling.

[0158] Figure 2 The image shows a SEM image of the single-crystal ternary material prepared in Example 1 of this invention. The results show that after activating the precursor with a ball milling aid, the obtained product exhibits a uniformly dispersed single-crystal particle morphology with a particle size of approximately 2-4 micrometers.

[0159] Figure 3 The XRD pattern of the single-crystal ternary material prepared in Example 1 of this invention shows that all diffraction peaks correspond to the typical α-NaFeO2 layered structure, and the (006) / (102) and (108) / (110) splits are obvious, indicating that the material has a highly ordered layered structure. Table 1 shows the oxygen vacancy ratio in the XPS O1s pattern of the precursors used in each example and comparative example. The results show that the introduction of the ball milling aid can effectively increase the oxygen vacancy ratio in the precursor, thereby facilitating the formation of single-crystal particles and lithiation during the calcination process.

[0160] Electrochemical performance analysis was performed by assembling button half-cells. Figure 4 The test results in Table 2 show that the initial discharge specific capacities of Examples 1, 2, and 3 at 0.1 C are 198.9, 180.5, and 190.5 mAh g, respectively. -1The first-cycle coulombic efficiencies were 89.2%, 88.0%, and 88.5%, respectively. Even at a high current density of 5C, the specific capacities remained as high as 138.6, 124.0, and 132.0 mAh g⁻¹. -1 Furthermore, after 100 cycles at a current density of 1C, the capacity retention rates of Examples 1, 2, and 3 were as high as 93.4%, 94.5%, and 94.0%, respectively. These results demonstrate that the single-crystal ternary material prepared by the method of this invention possesses high specific capacity, excellent rate performance, and long cycle life, and exhibits good applicability in systems with different nickel contents.

[0161] When citric acid was used as a ball milling aid, the material prepared in Example 4 also exhibited excellent electrochemical performance, with a 0.1C discharge specific capacity of 199.5 mAh g⁻¹. -1 First-efficiency performance is 88.6%, and the capacity remains at 138.0 mAh g at 5C rate. -1 This confirmed that various organic acid additives all possess good mechanochemical activation effects. Example 5, by increasing the oxalic acid dosage to 5% and lowering the calcination temperature to 780°C, still yielded 197.0 mAh g. -1 The initial discharge capacity and 92.2% capacity retention per 100 cycles demonstrate the significant advantage of the method of the present invention in reducing the synthesis temperature.

[0162] When the process parameters are not within the preferred range, Comparative Examples 1-3 use the same ball milling process but without adding ball milling aids, and the specific capacity of the prepared materials decreases to 158.0~172.0 mAh g⁻¹. -1 Rate performance and cycle stability also showed varying degrees of degradation. Comparative Example 4, which used a conventional low-speed mixing method without any additives or high-energy ball milling activation, produced the worst-performing material, with a first-cycle specific capacity of only 145.0 mAh g⁻¹. -1 The retention rate after 100 cycles was as low as 70.0%. Comparative Examples 5 and 6, with the addition of Bi₂O₃ and CeO₂ as sintering aids respectively, showed some improvement compared to the sample without aids, with first-cycle specific capacities reaching 175.0~178.0 mAh g⁻¹. -1 However, its cycle retention rate (80.0%~81.0%) and rate performance (only 105.0~108.0 mAh g at 5C) are low. -1The results of Comparative Example 7 were significantly inferior to those of the embodiments of the present invention, confirming that traditional sintering aid strategies are difficult to balance lithiation promotion and interface purity, and cannot achieve the synergistic breakthrough of "low-temperature synthesis" and "large-size single crystal" described in the present invention. Comparative Example 7 used p-toluenesulfonic acid as a ball milling aid (a strong organic acid), and the performance of the resulting material was severely deteriorated: the specific capacity of the first cycle was only 171.3 mAh / g, the coulombic efficiency of the first cycle was as low as 75.1%, the capacity at 5C rate was only 89.4 mAh / g, and the retention rate after 100 cycles was only 72.3%. Compared with Comparative Example 1 without aid, its capacity, rate capability, and cycling performance all decreased, confirming that the strong acid caused excessive corrosion to the precursor surface during ball milling, destroying the controllable defect construction, resulting in uneven lithiation reaction and reduced order of the layered structure. This further proves the key role of the organic acid (pKa 1~6) defined in the present invention in achieving mild surface activation and avoiding excessive corrosion.

[0163] In summary, this invention provides a method for preparing ternary cathode materials, ternary cathode materials, and lithium-ion batteries. The optimized method for preparing ternary cathode materials offers the following advantages: (1) In this invention, an organic acid additive is introduced during the ball milling stage to complete the in-situ construction of defects on the precursor surface in one step. This defect layer serves as a preferential diffusion channel for lithium ions, which significantly reduces the energy barrier of solid-phase lithiation reaction. At the same time, it induces crystal epitaxial growth through confined nucleation, which synergistically promotes the homogenization and coarsening of lithiation at low temperatures, ultimately forming a high-performance single-crystal ternary material with an ordered layered structure and uniform size.

[0164] (2) This invention significantly reduces the synthesis temperature of the all-dry process by inducing surface defects through ball milling aids, thereby fundamentally reducing energy consumption and lithium source volatilization loss caused by high-temperature calcination. The optimization of the synthesis temperature not only reduces equipment energy consumption and operating costs, but also reduces raw material consumption caused by lithium replenishment, further enhancing the low-cost advantage of the all-dry process.

[0165] (3) The present invention obtains a ternary product with an ordered layered structure and uniform single crystal dispersion, which endows it with high specific capacity and long cycle life from the material source.

[0166] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a ternary cathode material, characterized in that, include: A lithium-free precursor was obtained by ball milling a nickel source, a cobalt source, and a manganese source in the presence of a ball milling aid; wherein the ball milling aid was an organic acid. The lithium-free precursor is mixed with a lithium source and then calcined.

2. The preparation method according to claim 1, characterized in that, The organic acid has a pKa of 1-6, where Ka represents the dissociation constant; Preferably, the organic acid is selected from at least one of oxalic acid, citric acid, tartaric acid, acetic acid, malic acid, and ethylenediaminetetraacetic acid; More preferably, the organic acid is selected from at least one of oxalic acid and citric acid.

3. The preparation method according to claim 1 or 2, characterized in that, The molar amount of the organic acid is 1%-5% of the total molar amount of nickel, cobalt, and manganese; And / or, the area of ​​the oxygen vacancy characteristic peak at 531.2~531.8 eV in the XPS O 1s spectrum of the lithium-free precursor accounts for 15%-45%.

4. The preparation method according to claim 1, characterized in that, During the ball milling process, the rotation speed is controlled at 100rpm-1000rpm, and the ball milling time is 2h-15h; And / or, control the ball-to-material ratio to be (10-15):1; And / or, the atmosphere of the ball mill is air or an inert atmosphere; And / or, the ball milling equipment is a planetary high-energy ball milling equipment.

5. The preparation method according to claim 1 or 4, characterized in that, Add grinding media before ball milling; Preferably, the grinding media is selected from at least one of ethanol and acetone; Preferably, the mass ratio of the grinding media to the total mass of the nickel source, the cobalt source and the manganese source is (10-20):

100.

6. The preparation method according to claim 1, characterized in that, The calcination temperature is 750℃-900℃, and the holding time is 8h-20h; And / or, calcination is carried out in an oxygen-containing atmosphere.

7. The preparation method according to claim 1, characterized in that, The molar ratio of lithium to the total amount of nickel, cobalt, and manganese in the lithium source is controlled to be 1.02-1.10; And / or, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium acetate.

8. The preparation method according to claim 1, characterized in that, The nickel source is selected from at least one of nickel oxide, nickel hydroxide, nickel carbonate, and nickel oxalate, preferably nickel oxide; And / or, the cobalt source is selected from at least one of cobalt(II) oxide, cobalt(III) oxide, cobalt(IV) oxide, cobalt(III) hydroxide, cobalt(IV) carbonate and cobalt(IV) oxalate, preferably at least one of cobalt(II) oxide, cobalt(III) oxide and cobalt(IV) oxalate; And / or, the manganese source is selected from at least one of manganese trioxide, manganese tetroxide, manganese dioxide, manganese hydroxide, manganese carbonate and manganese oxalate, preferably at least one of manganese trioxide, manganese tetroxide and manganese dioxide; And / or, by adjusting the amounts of the nickel source, the cobalt source and the manganese source, the molar ratio of nickel, cobalt and manganese is (0.6-0.90):(0.05-0.3):(0.05-0.3).

9. A ternary cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Including the ternary cathode material as described in claim 9.

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