Ternary positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a ternary positive electrode material and a preparation method and application thereof. The preparation method of the ternary positive electrode material provided by the invention comprises the following steps: S1, mixing a small-particle ternary positive electrode material precursor with a lithium source and a doping agent, carrying out first sintering, cooling and crushing to obtain a small-particle primary sintering product; mixing the large-particle ternary positive electrode material precursor with a lithium source and a doping agent, carrying out primary sintering, and crushing to obtain a large-particle primary sintering product; and S2, mixing the small-particle primary sintering product and the large-particle primary sintering product with a coating agent, and carrying out secondary sintering to obtain the ternary positive electrode material. The ternary positive electrode material prepared by the preparation method provided by the invention is large in compaction density, low in residual alkali content, good in interface stability, and relatively good in capacity and cycling stability, and the electrochemical performance of the ternary positive electrode material under a high-voltage condition is remarkably improved.

Description

Technical Field

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

[0002] Lithium-ion batteries possess advantages such as high operating voltage, light weight, small size, no memory effect, low self-discharge rate, long cycle life, and high energy density, and are currently widely used in digital products, electric vehicles, energy storage grids, and other fields. In recent years, with the rapid development of electronic products, people have higher demands for battery energy density, safety, cost, and environmental friendliness.

[0003] Existing ternary cathode materials still exhibit shortcomings in electrochemical performance under 4.5V high-voltage conditions. Their initial discharge capacity is often below 220mAh / g, and capacity retention after 500 cycles is generally below 80%. The main reasons for these defects are: 1) The material structure is unstable under high voltage, with intense interfacial side reactions, leading to irreversible phase transitions and lattice oxygen loss, resulting in rapid capacity decay; 2) Traditional single-particle-size distribution systems struggle to achieve ideal electrode packing density, with compaction densities typically only reaching 3.2-3.4 g / cm³, limiting the improvement of battery energy density and affecting the full utilization of active materials; 3) Existing doping and coating processes using conventional elements cannot effectively suppress interfacial side reactions under high voltage, resulting in high residual alkali content and poor cycle stability, severely restricting their application in high-voltage batteries; 4) Existing processes have limited ability to control the particle size distribution, failing to achieve optimized particle size ratios, further hindering the improvement of the material's overall performance. Summary of the Invention

[0004] This invention provides a ternary cathode material, its preparation method, and its application, to solve the problems of insufficient compaction density, high residual alkali content, and poor cycle performance of existing ternary cathode materials under high voltage conditions.

[0005] In a first aspect, the present invention provides a method for preparing a ternary cathode material, comprising the following steps: Step S1: Small-particle ternary cathode material precursors are mixed with lithium sources and dopants for a first sintering, cooled, and pulverized to obtain small-particle first-sintered products; large-particle ternary cathode material precursors are mixed with lithium sources and dopants for a first sintering, and pulverized to obtain large-particle first-sintered products; the dopants include Nb2O5 and La2O3; the D50 of the small-particle first-sintered products is 3-3.4 μm; the D50 of the large-particle first-sintered products is 4.6-5 μm; Step S2: The small-particle primary sintering product and the large-particle primary sintering product are mixed with a coating agent and sintered a second time to obtain a ternary cathode material; the coating agent includes Ta2O5 and Y2O3; the temperature of the second sintering is 300-450℃.

[0006] In one optional implementation, in step S1, the ternary cathode material precursor is nickel-cobalt-manganese hydroxide. Optionally, the chemical formula of nickel cobalt manganese hydroxide is Ni x Co y Mn 1-x-y (OH)2, where 0.6≤x≤0.65, 0.05≤y≤0.1, and satisfy x+y<1; And / or, the lithium source includes lithium hydroxide.

[0007] In one optional implementation, in step S1, the D50 of the small-particle ternary cathode material precursor is 2.5-2.9 μm.

[0008] In one alternative embodiment, the D50 of the large-particle ternary cathode material precursor is 4.8-5.2 μm.

[0009] In one optional embodiment, the ratio of the total number of moles of metal elements in the small-particle ternary cathode material precursor to the number of moles of lithium elements in the lithium source is 1:1.01-1.10.

[0010] And / or, the ratio of the total number of moles of metal elements in the large-particle ternary cathode material precursor to the number of moles of lithium elements in the lithium source is 1:1.01-1.10.

[0011] In one optional implementation, in step S1, the added mass of Nb2O5 is 1000-3000 ppm and the added mass of La2O3 is 1000-2500 ppm, based on the mass of the small-particle ternary cathode material precursor.

[0012] In one optional implementation, the mass of Nb2O5 added is 1000-3000 ppm and the mass of La2O3 added is 1000-2500 ppm, based on the mass of the large-particle ternary cathode material precursor.

[0013] In an optional embodiment, in step S1, the first sintering is performed by holding at 480-520°C for 4-6 hours at a heating rate of 1-3°C / min in an oxygen atmosphere, followed by holding at 955-975°C for 9-11 hours at a heating rate of 4-6°C / min.

[0014] In one alternative embodiment, the oxygen flow rate is 1.5-2.5 L / min.

[0015] In one alternative embodiment, the cooling is to reduce the temperature to 180-220°C at a rate of 9-11°C / min, and then reduce it to 23-27°C.

[0016] In one alternative embodiment, the crushing pressure is 0.6-0.8 MPa.

[0017] In one optional embodiment, the mass ratio of the small-particle primary sintering product to the large-particle primary sintering product is 1:1-3.

[0018] In one optional embodiment, the mass of Ta2O5 added is 1000-3000 ppm, based on the total mass of the small-particle primary sintering product and the large-particle primary sintering product.

[0019] In one optional embodiment, the added mass of Y2O3 is 800-2000 ppm, based on the total mass of the small-particle primary sintering product and the large-particle primary sintering product.

[0020] In one alternative embodiment, the second sintering is performed by holding at the sintering temperature for 3-5 hours at a heating rate of 2-4°C / min in an oxygen-containing atmosphere.

[0021] In one alternative embodiment, the oxygen-containing atmosphere includes air and / or oxygen.

[0022] Secondly, the present invention provides a ternary cathode material, which is prepared by the above-described method for preparing ternary cathode materials; the specific surface area of ​​the ternary cathode material is 0.4-0.55 m². 2 / g.

[0023] Thirdly, the present invention provides the application of the above-mentioned ternary cathode material in the preparation of lithium-ion batteries.

[0024] The technical solution of this invention has the following advantages: 1. This invention provides a method for preparing a ternary cathode material. By employing a dual-particle size design using small and large particles sintered in a single process, the specific surface area of ​​the final cathode material is within a suitable range, significantly improving the material interface stability. Simultaneously, it significantly increases the electrode compaction density to over 3.5 g / cm³, optimizing the internal structure of the electrode to improve the utilization rate of active materials. Specific dopants (Nb₂O₅ and La₂O₃) and coating agents (Ta₂O₅ and Y₂O₃) are used to stabilize the material's crystal structure, achieving a discharge specific capacity greater than 230 mAh / g at a high voltage of 4.5V while effectively suppressing phase transitions and lattice oxygen evolution. By controlling the coating sintering temperature in the preparation process, the residual alkali content is reduced to below 0.2%, enabling the final cathode material to maintain a high capacity while retaining a capacity retention rate of over 85% after 500 cycles at 1C rate. This comprehensively overcomes the technical bottleneck of traditional materials struggling to balance capacity, compaction density, and cycle stability in high-voltage applications.

[0025] 2. The present invention provides a ternary cathode material, which is prepared by the above-described method for preparing ternary cathode materials. This ternary cathode material has a high compaction density, low residual alkali content, and good interfacial stability, exhibiting good capacity and cycle stability, and significantly improving its electrochemical performance under high voltage conditions. Detailed Implementation

[0026] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental steps or conditions in the examples were performed in accordance with conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0028] In each embodiment and comparative example, the particle size D50 was tested using a Malvern Mastersizer 3000 laser particle size analyzer with a light-blocking degree of 10% and the sample stirred at 2500 r / min. The instrument automatically completed three measurements and recorded the particle size distribution data.

[0029] Example 1 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take small-particle ternary cathode material precursor (molecular formula: Ni 0.63 Co 0.07 Mn 0.3(OH)₂, D50 = 2.727 μm, specific surface area is 13.755 m². 2 (g) and lithium hydroxide were added to a high-speed mixer at a molar ratio of total nickel, cobalt, and manganese metals to lithium of 1:1.05. Simultaneously, based on the precursor mass, 2000 ppm of Nb₂O₅ and 1500 ppm of La₂O₃ were added to the high-speed mixer, and the mixture was stirred at 500 rpm for 60 min to obtain a mixture. The mixture was then subjected to a first sintering in an oxygen atmosphere. The temperature was first increased to 500℃ at a heating rate of 2℃ / min and held for 5 h, then increased to 965℃ at a heating rate of 5℃ / min and held for 10 h. The oxygen flow rate during sintering was 2 L / min. After sintering, the temperature was decreased to 200℃ at a rate of 10℃ / min, and then allowed to cool naturally to room temperature to obtain a small-particle primary sintered product. This small-particle primary sintered product was subjected to air jet milling at a controlled milling pressure of 0.7 MPa to obtain a small-particle primary sintered product with a D50 of 3.2 μm. Large-particle ternary cathode material precursors (molecular formula: Ni) were then used. 0.63 Co 0.07 Mn 0.3 (OH)₂, D50 = 5.025 μm, specific surface area is 20.961 m² 2 / g), repeat the above operation to obtain a large particle primary sintering product with D50=4.8μm; (2) Take small-particle primary sintering products and large-particle primary sintering products at a mass ratio of 1:2.3 and add them to a three-dimensional mixer. Based on the total mass of small-particle primary sintering products and large-particle primary sintering products, add 1800ppm of Ta2O5 and 1200ppm of Y2O3 to the three-dimensional mixer and mix at 30rpm for 120min. The uniformly mixed material is heated at 400℃ for 4h at a heating rate of 3℃ / min under an oxygen atmosphere to complete the coating and obtain the ternary cathode material.

[0030] Example 2 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take small-particle ternary cathode material precursor (molecular formula: Ni 0.63 Co 0.07 Mn 0.3 (OH)₂, D50 = 2.727 μm, specific surface area is 13.755 m². 2(g) and lithium hydroxide were added to a high-speed mixer at a molar ratio of total nickel, cobalt, and manganese metals to lithium of 1:1.01. Simultaneously, based on the precursor mass, 1000 ppm of Nb₂O₅ and 2500 ppm of La₂O₃ were added to the high-speed mixer, and the mixture was stirred at 500 rpm for 60 min to obtain a mixture. The mixture was then subjected to a first sintering in an oxygen atmosphere. The temperature was first increased to 520℃ at a heating rate of 3℃ / min and held for 4 h, then increased to 955℃ at a heating rate of 4℃ / min and held for 11 h. The oxygen flow rate during sintering was 2.5 L / min. After sintering, the temperature was decreased to 220℃ at a rate of 9℃ / min, and then naturally cooled to room temperature to obtain a small-particle primary sintered product. The small-particle primary sintered product was subjected to air jet milling with a milling pressure controlled at 0.6 MPa to obtain a small-particle primary sintered product with D50 = 3.2 μm. Large-particle ternary cathode material precursors (molecular formula: Ni) were then used. 0.63 Co 0.07 Mn 0.3 (OH)₂, D50 = 5.025 μm, specific surface area is 20.961 m² 2 / g) Repeat the same operation as for the small-particle ternary cathode material precursor to obtain a large-particle one-time sintered product with D50=4.8μm; (2) Take small-particle primary sintering products and large-particle primary sintering products at a mass ratio of 1:1 and add them to a three-dimensional mixer. Based on the total mass of small-particle primary sintering products and large-particle primary sintering products, add 3000ppm of Ta2O5 and 800ppm of Y2O3 to the three-dimensional mixer and mix at 30rpm for 120min. The uniformly mixed material is then heated at 450℃ for 3h in air atmosphere at a heating rate of 4℃ / min to complete the coating and obtain the ternary cathode material.

[0031] Example 3 This embodiment provides a method for preparing a ternary cathode material, including the following steps: (1) Take small-particle ternary cathode material precursor (molecular formula: Ni 0.63 Co 0.07 Mn 0.3 (OH)₂, D50 = 2.727 μm, specific surface area is 13.755 m². 2(g) and lithium hydroxide were added to a high-speed mixer at a molar ratio of nickel, cobalt, manganese and lithium of 1:1.10. Simultaneously, based on the precursor mass, 3000 ppm of Nb₂O₅ and 1000 ppm of La₂O₃ were added to the high-speed mixer, and the mixture was stirred at 500 rpm for 60 min to obtain a mixture. The mixture was then subjected to a first sintering in an oxygen atmosphere. The temperature was first increased to 480℃ at a heating rate of 1℃ / min and held for 6 h, then increased to 975℃ at a heating rate of 6℃ / min and held for 9 h. The oxygen flow rate during sintering was 1.5 L / min. After sintering, the temperature was decreased to 180℃ at a rate of 11℃ / min, and then naturally cooled to room temperature to obtain a small-particle primary sintered product. The small-particle primary sintered product was subjected to air jet milling at a controlled milling pressure of 0.8 MPa to obtain a small-particle primary sintered product with a D50 of 3.2 μm. Large-particle ternary cathode material precursors (molecular formula: Ni) were then used. 0.63 Co 0.07 Mn 0.3 (OH)₂, D50 = 5.025 μm, specific surface area is 20.961 m² 2 / g) Repeat the same operation as for the small-particle ternary cathode material precursor to obtain a large-particle one-time sintered product with D50=4.8μm; (2) Take small-particle primary sintering products and large-particle primary sintering products at a mass ratio of 1:3 and add them to a three-dimensional mixer. Based on the total mass of small-particle primary sintering products and large-particle primary sintering products, add 1000ppm of Ta2O5 and 2000ppm of Y2O3 to the three-dimensional mixer and mix at 30rpm for 120min. The uniformly mixed material is then heated at 300℃ for 5h in an oxygen atmosphere at a heating rate of 2℃ / min to complete the coating and obtain the ternary cathode material.

[0032] Example 4 This embodiment provides a method for preparing a ternary cathode material, which is basically the same as that in embodiment 1. The only difference is that the amount of dopant added in step (1) is different. Specifically, based on the mass of the precursor, 3000ppm of Nb2O5 and 2500ppm of La2O3 are added.

[0033] Comparative Example 1 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 1, except that in step (2), the mass of the large-particle primary sintering product is replaced with the small-particle primary sintering product.

[0034] Comparative Example 2 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 2, except that the dopant in step (1) is different. Specifically, an equal mass of Al2O3 is used to replace Nb2O5, and an equal mass of MgO is used to replace La2O3.

[0035] Comparative Example 3 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 3, except that the sintering temperature in step (2) is different. Specifically, the uniformly mixed material is heated at 250°C for 5 hours in an oxygen atmosphere at a heating rate of 2°C / min to complete the coating and obtain the ternary cathode material.

[0036] Comparative Example 4 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 4, except that the coating agent in step (2) is replaced by an equal mass of Ta2O5 instead of Y2O3, that is, only Ta2O5 is used as the coating agent.

[0037] Comparative Example 5 This comparative example provides a method for preparing a ternary cathode material, which is basically the same as that in Example 4, except that the dopant in step (1) is replaced by an equal mass of Nb2O5 instead of La2O3, that is, only Nb2O5 is used as the dopant.

[0038] Test case 1. Electrochemical performance testing (1) The ternary cathode materials obtained in each embodiment and comparative example are assembled into coin cells. The preparation method of the coin cells is as follows: The cathode materials obtained from each embodiment and comparative example were mixed with conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) binder at a mass ratio of 96:2:2. N-methylpyrrolidone (NMP) solvent was added to adjust the slurry viscosity, and the solid content was controlled to be 48%. A uniform slurry was prepared by stirring at 800 rpm for 240 minutes using a dual planetary mixer. The slurry was then coated onto a 20 μm thick aluminum foil current collector using an automatic coating machine, with the wet film thickness controlled at 150 μm. Subsequently, it was dried in a vacuum oven at 110°C for 12 hours. The electrode sheets were compacted to a density of 3.5 g / cm³ using a roller mill under a pressure of 120 MPa and punched into circular sheets with a diameter of 14 mm. CR2032 coin cells were assembled in an argon-protected glove box, using lithium metal sheets as the counter electrode and Celgard 2400 as the separator, and injected with 1 mol / L... The LiPF6 EC / EMC / DEC (volume ratio 1:1:1) electrolyte was injected at a precise volume of 80 μL, and the electrochemical performance was tested after standing for 24 hours.

[0039] (2) Test method: The Blue Electric CT3001 test system was used with a voltage range of 3.0-4.5V and an ambient temperature of 25±2℃. The first five charge-discharge cycles were performed at a rate of 0.1C. The discharge capacity of the first cycle was recorded to obtain the initial discharge capacity. The cycle performance was tested at a rate of 1C for 500 cycles. The capacity retention rate after 500 cycles was calculated by dividing the discharge capacity after 500 cycles at 1C by the discharge capacity of the first cycle × 100%. 2. Material performance testing (1) Compacted density test method: Take 1g of the positive electrode material sample to be tested and put it into the powder compacted density tester (Chuanyuan Technology Suzhou Co., Ltd., model PD310). Compact it in the mold to a pressure of 17kN, then take out the sample, measure the height of the compaction block, and calculate the compacted density. The calculation formula is compacted density = m / (H×0.132665), where m represents the mass of the sample to be tested and H is the height of the compaction block.

[0040] (2) Residual alkali test method: The test was conducted in accordance with the standard GB / T 41704-2022 "Test Methods for Cathode Materials of Lithium-ion Batteries: Determination of Magnetic Foreign Matter Content and Residual Alkali Content".

[0041] (3) Specific surface area test method: The specific surface area was determined by using a specific surface area meter (Beijing Bio-Tech Electronic Technology Co., Ltd.; model: SSA-3500) and referring to the standard GB / T 19587-2017 "Determination of specific surface area of ​​solid substances by gas adsorption BET method". The specific surface area of ​​the sample was calculated by comparing the peak area of ​​the standard sample using gas chromatography.

[0042] Table 1 Performance Test Results

[0043] As can be seen from the results in Table 1, the materials with dual particle size distribution design prepared in Examples 1-4 of this invention all achieved a compaction density of 3.5 g / cm³ under a pressure of 17 kN. 3In the above cases, the residual alkali content was reduced to below 0.2%, and the specific surface area was further optimized. Within a voltage range of 3.0-4.5V, the coin cells assembled from the cathode materials prepared using the method of this invention exhibited a first discharge capacity exceeding 230mAh / g at 0.1C, and a capacity retention rate exceeding 85% after 500 cycles at 1C. Comparative Example 1, due to the use of only a single-size sintered product, resulted in a cathode material with lower compaction density, higher residual alkali content, and poorer electrochemical performance compared to Example 1. Comparative Example 2, by replacing the dopant with a traditional doping system, resulted in a cathode material with significantly higher residual alkali content and poorer cycle performance compared to Example 2. Comparative Example 3, by lowering the second sintering temperature, showed insufficient material performance and electrochemical performance compared to Example 3. Comparative Examples 4 and 5, using single coating agents and dopants respectively, showed inferior material and electrochemical performance compared to Example 4.

[0044] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a ternary cathode material, characterized in that, Includes the following steps: Step S1: Small-particle ternary cathode material precursors are mixed with lithium sources and dopants for a first sintering, cooled, and pulverized to obtain small-particle first-sintered products; large-particle ternary cathode material precursors are mixed with lithium sources and dopants for a first sintering, and pulverized to obtain large-particle first-sintered products; the dopants include Nb2O5 and La2O3; the D50 of the small-particle first-sintered products is 3-3.4 μm; the D50 of the large-particle first-sintered products is 4.6-5 μm; Step S2: The small-particle primary sintering product and the large-particle primary sintering product are mixed with a coating agent and sintered a second time to obtain a ternary cathode material; the coating agent includes Ta2O5 and Y2O3; the temperature of the second sintering is 300-450℃.

2. The method for preparing the ternary cathode material according to claim 1, characterized in that, In the S1 step, the ternary positive electrode material precursor is a nickel-cobalt-manganese hydroxide; optionally, the chemical formula of the nickel-cobalt-manganese hydroxide is Ni x Co y Mn 1-x-y (OH)2, wherein 0.6≤x≤0.65, 0.05≤y≤0.1, and x+y<1 is satisfied; and / or the lithium source comprises lithium hydroxide.

3. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S1, the D50 of the small-particle ternary cathode material precursor is 2.5-2.9 μm; And / or, the D50 of the large-particle ternary cathode material precursor is 4.8-5.2 μm; And / or, the ratio of the total number of moles of metal elements in the small-particle ternary cathode material precursor to the number of moles of lithium elements in the lithium source is 1:1.01-1.10; And / or, the ratio of the total number of moles of metal elements in the large-particle ternary cathode material precursor to the number of moles of lithium elements in the lithium source is 1:1.01-1.

10.

4. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S1, based on the mass of the small-particle ternary cathode material precursor, the added mass of Nb2O5 is 1000-3000ppm, and the added mass of La2O3 is 1000-2500ppm. And / or, based on the mass of the large-particle ternary cathode material precursor, the added mass of Nb2O5 is 1000-3000ppm, and the added mass of La2O3 is 1000-2500ppm.

5. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S1, the first sintering is carried out in an oxygen atmosphere at a heating rate of 1-3℃ / min at 480-520℃ for 4-6 hours, followed by a heating rate of 4-6℃ / min at 955-975℃ for 9-11 hours. Optionally, the oxygen flow rate is 1.5-2.5 L / min; And / or, the cooling is to reduce the temperature to 180-220°C at a rate of 9-11°C / min, and then reduce the temperature to 23-27°C; And / or, the crushing pressure is 0.6-0.8 MPa.

6. The method for preparing the ternary cathode material according to claim 1, characterized in that, The mass ratio of the small-particle primary sintering product to the large-particle primary sintering product is 1:1-3.

7. The method for preparing the ternary cathode material according to claim 1, characterized in that, In step S2, the mass of Ta2O5 added is 1000-3000 ppm, based on the total mass of the small-particle primary sintering product and the large-particle primary sintering product. And / or, the mass of Y2O3 added is 800-2000 ppm, based on the total mass of the small-particle primary sintering product and the large-particle primary sintering product.

8. The method for preparing the ternary cathode material according to claim 1, characterized in that, The second sintering is carried out in an oxygen-containing atmosphere at a heating rate of 2-4℃ / min and held at the sintering temperature for 3-5 hours. Optionally, the oxygen-containing atmosphere includes air and / or oxygen.

9. A ternary cathode material, characterized in that, The ternary cathode material is prepared using the method described in any one of claims 1-8; the specific surface area of ​​the ternary cathode material is 0.4-0.55 m². 2 / g.

10. The application of the ternary cathode material according to claim 9 in the preparation of lithium-ion batteries.

Images