A surface multi-metal modified high-nickel positive electrode material and a preparation method and application thereof

Abstract

The application provides a high-nickel positive electrode material with surface multi-metal modification and a preparation method and application thereof. The positive electrode material is a high-nickel positive electrode material with surface multi-metal modification and is composed of a high-nickel positive electrode material and multi-metals on the surface of the high-nickel positive electrode material. The multi-metals can be a combination of cobalt and aluminum or a combination of cobalt, aluminum and other metals (including one or more of iron, niobium, tantalum, tungsten, titanium, zinc, zirconium and molybdenum). The application starts from the selection and control of coating species, is based on a low-cost and high-efficiency surface treatment process, further combines a high-temperature heat treatment process in the later stage, adjusts and controls the chemical reaction of the surface coating species and the high-nickel positive electrode on the surface, realizes the adjustment and optimization of the physical and chemical properties of the high-nickel positive electrode surface, and thus obtains a high-stable positive electrode / electrolyte interface, which has important theoretical and application values for improving the stability and safety of high-energy lithium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a high-nickel cathode material with multi-metal surface modification, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as an important electrochemical energy storage device, have been widely used in consumer electronics, energy storage devices, and electric vehicles due to their high energy density, environmental friendliness, and excellent safety performance. With the rapid development of the energy storage industry, more stringent requirements have been placed on key performance indicators of lithium-ion batteries, such as energy density, cost-effectiveness, and cycle life, to meet the diversified needs of the future market. Among all the components of a lithium-ion battery, the cathode material plays a crucial role in the overall battery performance. On the one hand, the cost of the cathode material usually accounts for a large proportion of the total battery cost, directly affecting the battery's economics; on the other hand, the charge / discharge capacity and energy density of a lithium-ion battery are mainly determined by the cathode material. Therefore, improving the performance of the cathode material can not only optimize the overall battery performance but also is of great significance for reducing costs and increasing energy density. Against this backdrop, the development of high-energy-density cathode materials has become key to breaking through the performance bottlenecks of lithium-ion batteries and promoting their large-scale application.

[0003] However, while achieving increased energy density, high-energy-density cathode materials typically face more severe surface side reactions and bulk structural degradation problems. These issues lead to rapid capacity decay, resulting in shortened cycle life and increased potential safety hazards, such as thermal runaway. Given that the surface of cathode materials is the source of structural failure and the main site of side reactions, constructing a protective coating layer on the cathode material surface and improving stability by controlling the surface chemical properties and structural attributes is an important means to obtain high-performance, high-energy-density cathode materials.

[0004] However, the design and construction of the surface coating layer are both key and challenging aspects of controlling the surface structure of cathode materials. On the one hand, commonly used inert coating layers have poor electronic and ionic conductivity, which increases the charge transfer resistance between the material surface and the interface, thus reducing the charge and discharge capacity of the cathode material. Therefore, it is necessary to combine the selection and control of surface coating species to obtain better interfacial stability. On the other hand, commonly used coating methods in current research include solid-phase mixing, liquid-phase evaporation, and atomic layer deposition. Simple solid-phase mixing and liquid-phase evaporation can quickly introduce modified species, but they cannot achieve uniform control of the material surface or effective regulation of the cathode material surface state. Atomic layer deposition can achieve uniform coating of the material surface, but it has disadvantages such as high cost, harsh reaction conditions, and high toxicity. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-nickel cathode material with multi-metal surface modification, its preparation method, and its applications, thereby improving the stability and safety of existing high-nickel cathode materials. Furthermore, given the inherent sensitivity of high-nickel cathode materials to water and air, structural degradation often occurs during surface treatment due to environmental exposure, affecting application performance. The surface treatment process of this invention, while ensuring no additional damage to the high-nickel cathode material, can fully meet the needs of scale-up production, offering advantages such as low cost and high reliability.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0007] The present invention provides a cathode material, wherein the cathode material is a high-nickel cathode material with surface multi-metal modification, and is composed of a high-nickel cathode material and its surface modification with multi-metals.

[0008] The multimetallic composition may be a combination of cobalt and aluminum, or a combination of cobalt and aluminum with other metals (including one or more of iron, niobium, tantalum, tungsten, titanium, zinc, zirconium and molybdenum).

[0009] The high-nickel cathode material has the structural formula LiNi. x Co y Mn 1-x-y O2, where: 0.6≤x<1, for example, x=0.6, 0.7, 0.8, 0.91, 0.92; 0<y≤0.2, for example, y=0.06, 0.1, 0.04, 0.02; x+y<1;

[0010] In the cathode material, the mass fraction of the surface-modified metal element is 0.1-10%;

[0011] According to an embodiment of the present invention, the mass fraction of the surface-modified metal element in the cathode material is, for example, 0.5%, 0.8%, 1%, 1.5%, 2%, or 10%.

[0012] According to an exemplary embodiment of the present invention, the high-nickel cathode material may be LiNi. 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.92 Co 0.04 Mn 0.04 O2.

[0013] According to an embodiment of the present invention, the high-nickel cathode material includes single-crystal and polycrystalline high-nickel cathode materials.

[0014] The present invention also provides a method for preparing the above-mentioned cathode material.

[0015] The method for preparing the above-mentioned positive electrode material provided by the present invention includes the following steps:

[0016] (1) Add the high-nickel cathode material to the solvent to obtain suspension A;

[0017] (2) Add the complexing agent and water to suspension A to obtain suspension B;

[0018] (3) Add the metal salt to suspension B to carry out the reaction, centrifuge, wash and dry the reaction product to obtain the surface-modified high nickel cathode material;

[0019] (4) The surface-modified high-nickel cathode material prepared in step (3) is calcined at high temperature in an oxygen atmosphere to obtain a surface-modified high-nickel cathode material with multiple metals.

[0020] In step (1) of the above method, the structural formula of the high-nickel cathode material is LiNi. x Co y Mn 1-x-y O2, where: 0.6≤x<1, for example, x=0.6, 0.7, 0.8, 0.91, 0.92; 0<y≤0.2, for example, y=0.06, 0.1, 0.04, 0.02; x+y<1;

[0021] According to an exemplary embodiment of the present invention, the high-nickel cathode material may be LiNi. 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.92 Co 0.04 Mn 0.04 O2;

[0022] In step (1), the solvent is selected from at least one of organic alcohols and / or ketone solvents, such as at least one of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, n-butanol, acetone, etc., preferably ethanol;

[0023] In step (2), the ligand is an organic or inorganic reagent containing nitrogen, such as at least one selected from formamide, acetamide, triethanolamine, ammonium formate, oleylamine, hexadecylamine, tridecylamine, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hexamethylenetetramine, urea and ammonia, preferably oleylamine;

[0024] The ratio of the high-nickel cathode material to the ligand can be (2-500g):(0.1mmol-6.25mmol), preferably (2-10g):(0.1mmol:3mmol);

[0025] In step (2), the concentration of the ligand can be 1×10⁻⁶. -5 -0.3 mol / L, further preferably 3 × 10⁻⁶ mol / L. -4 -0.03 mol / L, exemplarily 1×10 -5 mol / L, 1×10 -4 mol / L, 3×10 -4 mol / L, 1×10 -3 mol / L, 0.01mol / L, 0.03mol / L, 0.1mol / L, 0.3mol / L;

[0026] In step (2), based on 2g of high-nickel cathode material, the amount of water added is 0.001mL-10mL, and further optimized to 0.01mL-7mL, with examples being 0.01mL, 0.05mL, 1mL, 3mL, and 5mL;

[0027] In step (3), the metal salt is selected from one or more of the following: chloride salts of metal elements, sulfate salts of metal elements, nitrate salts of metal elements, acetate salts of metal elements, and alkoxide salts of metal elements;

[0028] The multimetallic composition may be a combination of cobalt and aluminum, or a combination of cobalt and aluminum with other metals (including one or more of iron, niobium, tantalum, tungsten, titanium, zinc, zirconium and molybdenum).

[0029] In step (3), the concentration of the metal salt is 1×10⁻⁶. -5 -0.1 mol / L, preferably 1×10 -4 -0.01 mol / L, exemplarily 1×10 -5 mol / L, 1×10 -4 mol / L, 1×10 -3 mol / L, 0.01mol / L, 0.1mol / L;

[0030] The mass ratio of the high-nickel cathode material to the metal salt is 500-0.1, preferably 150-20, with examples being 300, 200, 150, 75, 38, 20, 10, and 5.

[0031] In one embodiment of the present invention, the metal salt is cobalt acetate and aluminum isopropoxide;

[0032] The mass ratio of the high-nickel cathode material to the metal salt is 200-20:7-1, specifically 50:3, 200:7, 50:1 or 100:1; wherein the mass ratio of cobalt acetate to aluminum isopropoxide is 1:1.

[0033] In another embodiment of the present invention, the metal salt is cobalt acetate, aluminum isopropoxide, and niobium ethanol;

[0034] The mass ratio of the high-nickel cathode material to the metal salt is 20:1.

[0035] Furthermore, the solvent used in this invention is of chromatographic purity and has a water content ≤0.1wt%.

[0036] In step (3), the reaction temperature is 5-150℃, preferably 15-60℃, for example 5℃, 20℃, 25℃, 40℃, 60℃.

[0037] In step (3), the reaction time is 0.1-24h, preferably 0.2-6h, with examples being 0.2h, 3h, 6h, 8h, 12h, and 24h.

[0038] In step (3), the metal ions undergo a hydrolysis reaction, and the hydrolysis rate of the metal ions is controlled by the participation of the ligand.

[0039] In step (4), the calcination temperature is 300-1000℃, preferably 600-800℃, and exemplarily 300℃, 400℃, 600℃, 650℃, 700℃, 750℃, 800℃, and 1000℃.

[0040] In step (4), the calcination time is 0.5-24h, preferably 1-5h, with examples being 0.5h, 1h, 3h, 5h, 8h, 12h, 24h, and 48h.

[0041] In step (4), the heating rate of calcination is 1-10℃ / min, for example 1℃ / min, 5℃ / min, or 10℃ / min.

[0042] The application of the aforementioned cathode material in lithium-ion batteries also falls within the scope of protection of this invention.

[0043] The present invention also provides a lithium-ion battery containing the above-mentioned positive electrode material.

[0044] According to an embodiment of the present invention, the positive electrode of the lithium-ion battery further includes a conductive agent Super-P and a binder polyvinylidene fluoride (PVDF).

[0045] According to an embodiment of the present invention, in the positive electrode, the mass ratio of the positive electrode material to the conductive agent and the binder is (8-0):(1-9):1, for example 8:1:1.

[0046] This invention starts with the selection and control of coating species, focusing on low-cost and efficient surface treatment processes. It further combines this with subsequent high-temperature heat treatment to regulate the chemical reaction between the surface-coated species and the high-nickel cathode, thereby controlling and optimizing the physicochemical properties of the high-nickel cathode surface. This results in a highly stable cathode / electrolyte interface, which has significant theoretical and practical value for improving the stability and safety of high-energy-density lithium-ion batteries. Specifically:

[0047] (1) This invention provides a method for preparing surface-modified high-nickel cathode materials with multiple metals, which has the advantages of simple process, low cost, environmental friendliness and large-scale production. The method is based on liquid-phase reaction, which introduces multiple metals on the surface of cathode materials and obtains surface-modified cathode materials with structural stability through high-temperature treatment, so as to achieve surface modification treatment of cathode materials and obtain excellent electrochemical performance.

[0048] (2) The high-nickel cathode material of the present invention, after surface coating and subsequent high-temperature treatment, achieves surface multi-metal modification and stabilization, and exhibits better electrochemical stability during battery testing. At the same time, the surface modification method of the cathode material of the present invention can improve the structural stability of the cathode material, thereby improving the cycle performance of the battery. Attached Figure Description

[0049] Figure 1 The X-ray diffraction (XRD) pattern of the high-nickel single-crystal cathode material with surface multi-metal modification prepared in Example 1 of the present invention.

[0050] Figure 2 Scanning electron microscope (SEM) image of the high-nickel single-crystal cathode material with surface multi-metal modification prepared in Example 1 of the present invention.

[0051] Figure 3 This is a transmission electron microscope (TEM) image of the high-nickel single-crystal cathode material with multi-metal modification on its surface before calcination in Example 1 of the present invention.

[0052] Figure 4 This is an X-ray energy dispersive spectroscopy (EDS) image of the high-nickel single-crystal cathode material with multi-metal modification on its surface before calcination, as shown in Example 1 of this invention.

[0053] Figure 5 The above are charge-discharge curves of the high-nickel single-crystal cathode materials in Example 1 and Comparative Example 1 of the present invention at a rate of 0.1C.

[0054] Figure 6This is a cycling diagram of the high-nickel single-crystal cathode material in Example 1 and Comparative Example 1 of the present invention at a 1C rate. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0056] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0057] Example 1

[0058] (I) Preparation of cathode materials

[0059] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (0.032 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 200:7). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0060] (II) Structural and Morphological Characterization

[0061] The crystal structure of the prepared cathode material was analyzed using a powder X-ray diffractometer (D8 Advance, Bruke), and the results are as follows: Figure 1 As shown in the figure, the cathode material prepared in this embodiment conforms to the diffraction peaks of layered materials and has no other impurity peaks, indicating that the material has high purity.

[0062] The morphology of the cathode materials prepared in the examples was further characterized using scanning electron microscopy (SEM-4800), and the results are as follows: Figure 2 As shown in the figure, the material retains the characteristics of single-crystal LiNi after surface modification.0.92 Co 0.04 Mn 0.04 Morphology of O2(NCM) cathode material.

[0063] The morphology of the high-nickel single-crystal cathode material modified with multi-metals before calcination was characterized using transmission electron microscopy (TEM-2100F). The results are as follows: Figure 3 As shown in the figure, the thickness of the multi-metal coating is approximately 8 nm.

[0064] Figure 4 The image shows the X-ray energy dispersive spectroscopy (EDS) analysis of the high-nickel single-crystal cathode material with multi-metal modification on its surface before calcination. The results show that there is a uniform and continuous coating layer containing cobalt and aluminum species on the surface of the high-nickel single-crystal cathode material.

[0065] (III) Battery Assembly

[0066] The prepared 200 mg of positive electrode material was mixed with 25 mg of polyvinylidene fluoride (PVDF) binder and 25 mg of Super-P conductive agent, and approximately 200 μL of N-methylpyrrolidone (NMP) was added to prepare a slurry. Using aluminum foil as the current collector, the slurry was uniformly coated onto the aluminum foil to a thickness of 200 μm. The coating was then vacuum dried at 80 °C for 12 h to obtain the positive electrode film. A lithium metal sheet was used as the negative electrode, a polypropylene microporous membrane (Celgard 2400) as the separator, and 1 mol / L LiPF6 (EC:DMC:DEC = 1:4:2) as the electrolyte. The cells were then assembled into a button cell in an argon-protected glove box.

[0067] (iv) Performance Testing

[0068] The assembled battery was subjected to constant current charge-discharge testing on a Blue Electric charge-discharge tester. The charge-discharge rate was 0.1C (1C = 200mA / g), and the charge-discharge range was 2.8-4.5V. The charge-discharge curve for the first cycle is shown below. Figure 5 As shown in the figure, the discharge specific capacity of this NCM cathode material can reach 197 mAh / g. The charge / discharge range is 3.0-4.5V, and the capacity retention after 100 cycles at 1C rate is 94.2% (e.g., ...). Figure 6 As shown in the figure, this indicates that the cathode material has good cycle stability.

[0069] Example 2

[0070] (I) Preparation of cathode materials

[0071] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 10 mg of cobalt acetate and 10 mg of aluminum isopropoxide (0.009 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 100:1). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0072] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0073] (III) Battery assembly (specific steps are the same as in Example 1).

[0074] (iv) Performance testing (the specific steps are the same as in Example 1).

[0075] Example 3

[0076] (I) Preparation of cathode materials

[0077] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 20 mg of cobalt acetate and 20 mg of aluminum isopropoxide (0.018 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 50:1). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0078] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0079] (III) Battery assembly (specific steps are the same as in Example 1).

[0080] (iv) Performance testing (the specific steps are the same as in Example 1).

[0081] Example 4

[0082] (I) Preparation of cathode materials

[0083] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 60 mg of cobalt acetate and 60 mg of aluminum isopropoxide (0.054 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 50:3). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0084] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0085] (III) Battery assembly (specific steps are the same as in Example 1).

[0086] (iv) Performance testing (the specific steps are the same as in Example 1).

[0087] Example 5

[0088] (I) Preparation of cathode materials

[0089] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (0.032 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 200:7). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 650 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0090] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0091] (III) Battery assembly (specific steps are the same as in Example 1).

[0092] (iv) Performance testing (the specific steps are the same as in Example 1).

[0093] Example 6

[0094] (I) Preparation of cathode materials

[0095] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (0.032 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 200:7). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 750 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0096] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0097] (III) Battery assembly (specific steps are the same as in Example 1).

[0098] (iv) Performance testing (the specific steps are the same as in Example 1).

[0099] Example 7

[0100] (I) Preparation of cathode materials

[0101] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04O2 (NCM) was dispersed in 10 mL of ethanol and stirred until a suspension was obtained. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (0.032 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 200:7). The mixture was stirred at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 1 h. After natural cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface. (II) Structure and morphology characterization (specific steps are the same as in Example 1).

[0102] (III) Battery assembly (specific steps are the same as in Example 1).

[0103] (iv) Performance testing (the specific steps are the same as in Example 1).

[0104] Example 8

[0105] (I) Preparation of cathode materials

[0106] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (0.032 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 200:7). The mixture was stirred at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 5 h. After naturally cooling to room temperature, it was ground in a mortar to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0107] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0108] (III) Battery assembly (specific steps are the same as in Example 1).

[0109] (iv) Performance testing (the specific steps are the same as in Example 1).

[0110] Example 9

[0111] (I) Preparation of cathode materials

[0112] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of oleylamine (0.03 mol / L concentration of ligand, ratio of high-nickel cathode material to ligand 2 g: 0.3 mmol) and 100 μL of deionized water were added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate, 35 mg of aluminum isopropoxide, and 30 μL of niobium ethanol (0.050 mol / L concentration of metal salt) were added to the suspension (mass ratio of high-nickel cathode material to metal salt 20:1). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0113] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0114] (III) Battery assembly (specific steps are the same as in Example 1).

[0115] (iv) Performance testing (the specific steps are the same as in Example 1).

[0116] Comparative Example 1

[0117] (I) Preparation of cathode materials

[0118] Take 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2 (NCM) was dispersed in 10 ml of anhydrous ethanol solution and stirred at 25 °C for 3 h. After centrifugation, washing and drying, the positive electrode material powder was obtained. The powder was calcined in a tube furnace at 700 °C for 3 h under an oxygen atmosphere at a heating rate of 5 °C / min. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain the unmodified positive electrode material.

[0119] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0120] (III) Battery assembly (specific steps are the same as in Example 1).

[0121] (iv) Performance testing (the specific steps are the same as in Example 1).

[0122] Comparative Example 2

[0123] (I) Preparation of cathode materials

[0124] Accurately weigh 2.000g of LiNi at 25℃ 0.92 Co 0.04 Mn 0.04 O2(NCM) was dispersed in 10 mL of ethanol and stirred until homogeneous to obtain a suspension. 100 μL of deionized water was added to the suspension and stirred until homogeneous. 35 mg of cobalt acetate and 35 mg of aluminum isopropoxide (concentration of metal salt was 0.032 mol / L) were added to the suspension (mass ratio of high-nickel cathode material to metal salt was 200:7). The mixture was stirred and reacted at 25 °C for 3 h. After centrifugation, washing, and drying, cathode material powder was obtained. The powder was calcined in a tube furnace under an oxygen atmosphere at a heating rate of 5 °C / min to 700 °C for 3 h. After naturally cooling to room temperature, it was ground in a mortar and pestle to obtain a cathode material with cobalt and aluminum co-modification on the surface.

[0125] (II) Structural and morphological characterization (specific steps are the same as in Example 1).

[0126] (III) Battery assembly (specific steps are the same as in Example 1).

[0127] (iv) Performance testing (the specific steps are the same as in Example 1).

[0128] The performance test results of the batteries in Examples 1-9 and Comparative Examples 1-2 are shown in Table 1 below.

[0129] Table 1

[0130] First-cycle discharge specific capacity 100 laps capacity maintenance Example 1 198.3 94.2 Example 2 192.8 89.7 Example 3 193.8 90.7 Example 4 189.5 93.0 Example 5 186.9 90.8 Example 6 195.4 93.0 Example 7 187.5 92.1 Example 8 194.0 91.0 Example 9 190.0 92.0 Comparative Example 1 188.7 85.8 Comparative Example 2 189.9 88.0

[0131] A comparison of Examples 1-9 with Comparative Example 1 shows that surface multi-metal modification can significantly improve the cycle stability of the cathode material, while an appropriate amount of metal ions added can improve the discharge specific capacity of the material to a certain extent.

[0132] As can be seen from the comparison of Examples 1-4, the amount of multi-metal coating on the surface affects the first-cycle discharge specific capacity and cycle stability of the cathode material. If the coating amount is too low, a sufficient stable layer cannot be formed on the cathode material surface, and the surface chemical properties cannot be fully adjusted, thus failing to provide comprehensive protection for the cathode material surface. However, if the coating amount is too high, other unstable impurities will form on the cathode surface, leading to a decrease in the first-cycle discharge specific capacity of the cathode material. Even with the high coating amount in Example 4 of this invention, its discharge capacity (189.5 mAh g) is... -1 It is still higher than the control ratio (188.7 mAh g) -1 This demonstrates that the method of improving the cycle stability of cathode materials through surface multi-metal modification is reliable.

[0133] A comparison of Examples 1 and 5-6 shows that calcination temperature affects the first-cycle discharge specific capacity and cycle stability of the cathode material. If the calcination temperature is too low, the reaction between the multi-metal coating layer and the solid phase on the cathode material surface is incomplete, forming an inert layer on the material surface, resulting in a decrease in discharge capacity and limited improvement in cycle stability. However, if the calcination temperature is too high, it will damage the crystal structure of the cathode material itself and generate harmful impurities, which to some extent affects the modification of the cathode material by the surface coating layer, leading to a decrease in cycle stability. The batteries assembled from the cathode materials prepared in Examples 5 and 6 of this invention still have a higher capacity retention rate after 100 cycles than the comparative examples, indicating that the multi-metal surface modification method of this invention can improve the cycle stability of the cathode material.

[0134] A comparison of Examples 1 and 7-8 shows that calcination time affects the first-cycle discharge specific capacity and cycle stability of the cathode material. Shortening the calcination time results in incomplete reaction between the electrode material and the surface multi-metal coating, leading to a decrease in the first-cycle discharge specific capacity of the cathode material and limited improvement in cycle stability. However, excessively long calcination times cause the multi-metal coating to form harmful impurities on the cathode material surface, which is detrimental to improving cycle stability. The batteries assembled from the cathode materials prepared in Examples 7 and 8 still exhibit better cycle stability than the comparative examples, demonstrating the effectiveness of the surface multi-metal modification method of this invention.

[0135] A comparison of Examples 1, 9, and Comparative Example 1 shows that after the additional introduction of niobium metal modification, the increased amount of surface-coated species leads to the formation of other unstable impurity phases on the cathode surface, resulting in a decrease in the first-cycle discharge specific capacity of the cathode material. The battery assembled from the cathode material obtained in Example 9 still exhibits better cycle stability than the comparative example, thus demonstrating the effectiveness of the multi-metal surface modification method of this invention.

[0136] A comparison of Example 1, Comparative Example 1, and Comparative Example 2 shows that without the addition of a ligand, the hydrolysis rate of metal ions is difficult to control, making it difficult to achieve effective coating. The cycle stability and discharge capacity of the battery assembled with the cathode material obtained in Comparative Example 2 are close to those of Comparative Example 1.

[0137] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A cathode material, wherein the cathode material is a high-nickel cathode material with surface multi-metal modification, and is composed of the high-nickel cathode material and the multi-metal modification on its surface; in, The multimetal is a combination of cobalt and aluminum, or a combination of cobalt and aluminum with other metals (including one or more of iron, niobium, tantalum, tungsten, titanium, zinc, zirconium and molybdenum).

2. The cathode material according to claim 1, characterized in that, The high-nickel cathode material has the structural formula LiNi. x Co y Mn 1-x-y O2, where: 0.6≤x<1; 0<y≤0.2; x+y<1; The high-nickel cathode material includes single-crystal and polycrystalline high-nickel cathode materials.

3. The cathode material according to claim 1, characterized in that, In the cathode material, the mass fraction of the surface-modified metal element is 0.1-10%.

4. A method for preparing the cathode material according to any one of claims 1-3, comprising the following steps: (1) Add the high-nickel cathode material to the solvent to obtain suspension A; (2) Add the complexing agent and water to suspension A to obtain suspension B; (3) Add the metal salt to suspension B to carry out the reaction, centrifuge, wash and dry the reaction product to obtain the surface-modified high nickel cathode material; (4) The surface-modified high-nickel cathode material prepared in step (3) is calcined at high temperature in an oxygen atmosphere to obtain a surface-modified high-nickel cathode material with multiple metals.

5. The method according to claim 4, characterized in that, In step (1), the high-nickel cathode material has the structural formula LiNi. x Co y Mn 1-x-y O2, where: 0.6≤x<1; 0<y≤0.2; x+y<1; In step (1), the solvent is selected from at least one of organic alcohols and / or ketone solvents.

6. The method according to claim 4, characterized in that, In step (2), the ligand is an organic or inorganic reagent containing nitrogen, specifically selected from at least one of formamide, acetamide, triethanolamine, ammonium formate, oleylamine, hexadecylamine, tridecylamine, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, hexamethylenetetramine, urea and ammonia water; The ratio of the high-nickel cathode material to the ligand is: (2-500g): (0.1mmol-6.25mmol); In step (2), the concentration of the ligand is 1×10⁻⁶. -5 -0.3mol / L; In step (2), the amount of water added is 0.001 mL to 10 mL.

7. The method according to claim 4, characterized in that, In step (3), the metal salt is selected from one or more of the following: chloride salts of metal elements, sulfate salts of metal elements, nitrate salts of metal elements, acetate salts of metal elements, and alkoxide salts of metal elements; The multimetal is a combination of cobalt and aluminum, or a combination of cobalt and aluminum with other metals (including one or more of iron, niobium, tantalum, tungsten, titanium, zinc, zirconium and molybdenum). In step (3), the concentration of the metal salt is 1×10⁻⁶. -5 -0.1 mol / L; The mass ratio of the high-nickel cathode material to the metal salt is 500-0.

1.

8. The method according to claim 4, characterized in that, In step (3), the reaction temperature is 5-150℃; the reaction time is 0.1-24h.

9. The method according to claim 4, characterized in that, In step (4), the calcination temperature is 300-1000℃; the calcination time is 0.5-24h. In step (4), the heating rate of calcination is 1-10℃ / min.

10. A lithium-ion battery, wherein the lithium-ion battery contains the positive electrode material according to any one of claims 1-3.

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