Ternary single crystal material for lithium ion battery and preparation method of ternary single crystal material

Abstract

The invention discloses a ternary single crystal material for a lithium ion battery and a preparation method of the ternary single crystal material, and relates to the technical field of lithium ion battery electrode materials. Comprising the following steps: mixing a nickel-cobalt-manganese compound and a lithium compound according to a ratio, and carrying out first sintering to obtain a first material; mixing the first material and a lithium compound according to a ratio, adding a nitride, mixing and mechanically granulating, and sintering for the second time to obtain a second material; and crushing the second material to obtain a third material, mixing the third material with inert elements, and carrying out third sintering to obtain the ternary single crystal material. According to the invention, a nitride material with high thermal conductivity is used as an additive, and mechanical granulation is utilized, so that the primary grain dispersity is effectively improved, and the conductivity and the cycle performance are improved. And meanwhile, the dispersity index of the primary crystal grains is quantified through formula calculation of the crystal grain size and the granularity data. The preparation process is simple, the operability is high, and large-scale production is easy to realize.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode materials technology, and more specifically, to a ternary single-crystal material for lithium-ion batteries and its preparation method. Background Technology

[0002] With the market's increasing demands for energy density, cycle life, and safety performance of lithium-ion batteries, ternary lithium batteries are rapidly developing towards higher capacity, longer cycle life, and higher stability. Against this backdrop, ternary single-crystal materials, due to their significant advantages in suppressing particle cracks, mitigating electrode surface side reactions, and extending battery cycle life, are gradually becoming an important development direction for high-performance cathode materials. Single-crystalization technology is also considered one of the key paths to promote the advancement of ternary battery technology.

[0003] However, single-crystal ternary materials still face key challenges in practical applications, with excessive agglomeration of primary grains being particularly prominent. This phenomenon easily leads to uneven or failed surface coatings, and when the battery is charged and discharged under high voltage conditions, changes in internal stress trigger microcracks, eventually causing the agglomerates to separate, exposing the unprotected ternary material matrix. This exacerbates interfacial side reactions and structural degradation, severely restricting the actual capacity and long-term cycle performance of the battery. Currently, the detection of primary grain agglomeration still mainly relies on visual observation of scanning electron microscope images, lacking unified and objective judgment standards and methods. This has become a significant bottleneck restricting the quality control and performance optimization of single-crystal ternary materials.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a ternary single-crystal material for lithium-ion batteries and a method for preparing the same. The dispersion of the ternary single-crystal material can be quantitatively controlled, effectively improving its cycle performance.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a ternary single-crystal material for lithium-ion batteries, wherein the hard agglomeration degree S of the ternary single-crystal material is 1-1.3; The hard agglomeration degree S is calculated using the following formula:

[0007] Where D[2,1] is the average area diameter of the sample tested by the laser particle size analyzer, and the primary grain size N is the primary grain size obtained by calculating the average of the major and minor axes of at least 50 primary grains in the material electron microscope image statistics and then taking the arithmetic mean.

[0008] Secondly, the present invention provides a method for preparing a ternary single-crystal material for lithium-ion batteries, comprising the following steps: mixing a nickel-cobalt-manganese compound with a lithium compound in a certain proportion and performing a first sintering to obtain a first material; mixing the first material with a lithium compound in a certain proportion and adding a nitride, mixing and mechanically granulating, and performing a second sintering to obtain a second material; pulverizing the second material to obtain a third material; and mixing the third material with an inert element and performing a third sintering to obtain a ternary single-crystal material.

[0009] In some preferred embodiments, the nickel-cobalt-manganese compound and the lithium compound are mixed, wherein the molar ratio of lithium to the molar ratio of transition metal in the nickel-cobalt-manganese compound is 0.5-0.95; the first material and the lithium compound are mixed, wherein the molar ratio of lithium to the molar ratio of transition metal in the first material is 1.0-1.1.

[0010] In some preferred embodiments, the nickel-cobalt-manganese compound is selected from at least one of nickel-cobalt-manganese hydroxide or nickel-cobalt-manganese oxide, wherein the molar number of nickel element accounts for 0.6-0.95% of the total molar number of the three transition metals nickel, cobalt, and manganese; the lithium compound is selected from at least one of lithium carbonate or lithium hydroxide.

[0011] In some preferred embodiments, the nitride is selected from at least one of aluminum nitride and boron nitride, and the addition ratio of the nitride is 300-4000 ppm.

[0012] In some preferred embodiments, the inert element is selected from at least one of aluminum, titanium or tungsten, and the coating amount of the inert element is 300-3000 ppm.

[0013] In some preferred embodiments, the mixing is performed using a high-speed mixer with a mixing time of 5-20 minutes and a rotation speed of 200-600 r / min.

[0014] In some preferred embodiments, the granulation is performed using a roller granulator with a granulation pressure of 10-40 MPa, a roller gap of 0.5-2.0 mm, and a feeding frequency of 10-45 Hz.

[0015] In some preferred embodiments, the first sintering, the second sintering, and the third sintering are all carried out in a high-temperature roller furnace, and the sintering is carried out in air or an oxygen-enriched atmosphere; the temperature of the first sintering is 600-900℃, and the sintering time is 14-20h; the temperature of the second sintering is 800-980℃, and the sintering time is 20-25h; the temperature of the third sintering is 400-600℃, and the sintering time is 14-20h.

[0016] In some preferred embodiments, the crushing is performed using an airflow crusher with a crushing pressure of 0.1-0.7 MPa and a feeding frequency of 5-50 Hz.

[0017] The present invention has the following beneficial effects: This invention utilizes nickel-cobalt-manganese precursors, lithium carbonate, and lithium hydroxide as raw materials, and introduces nitrides as a highly efficient thermally conductive medium during the preparation process. Combined with mechanical granulation to enhance powder-to-powder contact, this significantly improves the thermal uniformity of the material during preparation, successfully producing a ternary cathode material with a dispersibility of 1-1.3. This material exhibits excellent dispersion characteristics, effectively improving the cycle performance and safe lifespan of the battery. Furthermore, this invention establishes a quantitative formula relating grain size to particle size data, enabling precise evaluation of primary grain dispersibility. The overall process is simple, highly operable, and possesses promising prospects for large-scale production. Detailed Implementation

[0018] 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.

[0019] The following is a detailed description of a ternary single-crystal material for lithium-ion batteries and its preparation method proposed in this invention.

[0020] In a first aspect, the present invention proposes a ternary single-crystal material for lithium-ion batteries obtained by the above preparation method, wherein the hard agglomeration degree S of the ternary single-crystal material is 1-1.3, preferably 1-1.2.

[0021] The hard agglomeration degree S is calculated using the following formula:

[0022] Where D[2,1] is the average area diameter of the sample tested by the Malvern 3000 laser particle size analyzer, and the primary grain size N is the primary grain size obtained by calculating the average of the major and minor axes of at least 50 primary grains in the material electron microscope image statistics and then taking the arithmetic mean.

[0023] The principle of the characterization method is as follows: During particle size testing, some hard agglomerates of grains cannot be dissociated, resulting in the measured particle size being the result of agglomeration. In contrast, a single grain size test measures the long and short axes of each sub-grain, and the overall data represents the dispersed grain size. The ratio of these two measurements characterizes the single grain dispersion; the closer the ratio is to 1, the more dispersed the sample is theoretically.

[0024] Secondly, the present invention provides a method for preparing ternary single-crystal materials for lithium-ion batteries: S1. The nickel-cobalt-manganese compound and the lithium compound are mixed in a certain proportion and sintered for the first time to obtain the first material.

[0025] In an optional embodiment, the nickel-cobalt-manganese compound is selected from at least one of nickel-cobalt-manganese hydroxide and nickel-cobalt-manganese oxide, wherein the molar number of nickel element accounts for 0.6-0.95 of the total molar number of the three transition metals nickel, cobalt, and manganese; the lithium compound is selected from at least one of lithium carbonate or lithium hydroxide; and when the nickel-cobalt-manganese compound and the lithium compound are mixed, the ratio of the molar number of lithium element to the molar number of transition metals in the nickel-cobalt-manganese compound is 0.5-0.95, preferably 0.7-0.9.

[0026] In an optional embodiment, the temperature of the first sintering is 600-900°C, and the sintering time is 14-20 hours.

[0027] S2. The first material and lithium compound are mixed in a certain proportion and nitride is added. The mixture is then mechanically granulated and sintered a second time to obtain the second material.

[0028] In an optional embodiment, the first material and the lithium compound are mixed, wherein the ratio of the molar number of lithium element to the molar number of transition metal in the first material is 1.0-1.1, preferably 1.02-1.06; the nitride is selected from at least one of aluminum nitride and boron nitride, and the addition ratio of the nitride is 300-4000 ppm, preferably 500-2000 ppm.

[0029] In an optional embodiment, the granulation is performed using a roller granulator with a granulation pressure of 10-40 MPa, a roller gap of 0.5-2.0 mm, and a feeding frequency of 10-45 Hz; the second sintering temperature is 800-980℃, and the sintering time is 20-25 h.

[0030] S3. The second material is crushed to obtain the third material.

[0031] In an optional embodiment, the crushing is performed using an airflow crusher with a crushing pressure of 0.1-0.7 MPa and a feeding frequency of 5-50 Hz.

[0032] In some preferred embodiments, the primary grain size N of the third material is ≥1.0, preferably 1.4≤N≤2.5.

[0033] S4. The third material is mixed with an inert element and sintered for the third time to obtain a ternary single crystal material.

[0034] In an optional embodiment, the inert element is selected from at least one of aluminum, titanium or tungsten, and the coating amount of the inert element is 300-3000 ppm, preferably 500-2000 ppm.

[0035] In an optional embodiment, the temperature of the third sintering is 400-600°C, and the sintering time is 14-20 hours.

[0036] It should be noted that in the preparation method, all mixing operations are carried out using a high-speed mixer with a mixing time of 5-20 minutes and a rotation speed of 200-600 r / min; all sintering operations are carried out using a high-temperature roller furnace, and the sintering is carried out in air or oxygen-enriched atmosphere.

[0037] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0038] Example 1 This embodiment provides a method for preparing a ternary single-crystal material for lithium-ion batteries, which includes the following raw materials: Nickel-cobalt-manganese hydroxide precursor: Ni 0.8 Co 0.1 Mn 0.1 (OH)2, the molar ratio is ; Lithium compounds: Lithium hydroxide (LiOH·H2O); Nitride additive: Aluminum nitride (AlN); Source of coating element: aluminum oxide (Al2O3); Includes the following steps: S1. The precursor and lithium hydroxide are mixed at a lithium to transition metal molar ratio (Li / Me) of 0.8. The mixture is sintered at 600°C for 15 hours under an oxygen-rich atmosphere and then cooled in the furnace to obtain the first material.

[0039] S2. The first material and lithium hydroxide are mixed at a ratio of Li / Me = 1.04, and 1000 ppm of aluminum nitride additive is added. The mixture is then mixed for 10 minutes at 400 r / min using a high-speed mixer. The mixture is then mechanically granulated using a roller granulator at a pressure of 20 MPa, a roller gap of 1.0 mm, and a feeding frequency of 25 Hz. Finally, the mixture is sintered at 900℃ for 22 hours in an oxygen-enriched atmosphere to obtain the second material.

[0040] S3. The second material is crushed using an air jet crusher at a crushing pressure of 0.3 MPa and a feeding frequency of 20 Hz to obtain the third material.

[0041] S4. The third material is mixed with 1500 ppm of alumina and sintered at 500°C for 16 hours in air atmosphere to obtain the final ternary cathode material.

[0042] The ternary cathode material prepared in Example 1 was subjected to dispersibility testing: Malvern laser particle size analyzer measured D[2,1]: 3.12 μm.

[0043] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 2.61 μm.

[0044] The dispersion index S = D[2,1] / N = 3.12 / 2.61≈1.20 is calculated.

[0045] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 91.5%.

[0046] Comparative Example 1 This comparative example provides a method for preparing ternary single-crystal materials for lithium-ion batteries. The raw materials and steps are the same as in Example 1, except that aluminum nitride is not added as an additive.

[0047] The ternary cathode material prepared in Comparative Example 1 was subjected to dispersibility testing: Malvern laser particle size analyzer measured D[2,1]: 3.79 μm.

[0048] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 2.55 μm.

[0049] The dispersion index S = D[2,1] / N = 3.79 / 2.55≈1.49 is calculated.

[0050] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 88.7%.

[0051] Example 2 This embodiment provides a method for preparing a ternary single-crystal material for lithium-ion batteries, which includes the following raw materials: Nickel-cobalt-manganese hydroxide precursor: Ni 0.6 Co 0.2 Mn 0.2 (OH)2, the molar ratio is ; Lithium compounds: Lithium hydroxide (Li₂CO₃); Nitrogen compound additive: Boron nitride (BN); Coating element source: titanium dioxide (TiO2); Includes the following steps: S1. The precursor and lithium hydroxide are mixed at a lithium to transition metal molar ratio (Li / Me) of 0.85. The mixture is sintered at 800°C for 18 hours under an oxygen-rich atmosphere and then cooled in the furnace to obtain the first material.

[0052] S2. The first material and lithium hydroxide are mixed at a ratio of Li / Me = 1.06, and 500 ppm of boron nitride additive is added. The mixture is then mixed for 8 minutes at 500 r / min using a high-speed mixer. The mixture is then mechanically granulated using a roller granulator at a pressure of 30 MPa, a roller gap of 1.0 mm, and a feeding frequency of 25 Hz. Finally, the mixture is sintered at 920℃ for 24 hours in an air atmosphere to obtain the second material.

[0053] S3. The second material is crushed using an air jet crusher at a crushing pressure of 0.4 MPa and a feeding frequency of 20 Hz to obtain the third material.

[0054] S4. The third material is mixed with 800 ppm of titanium dioxide and sintered at 450°C for 18 hours in air atmosphere to obtain the final ternary cathode material.

[0055] The ternary cathode material prepared in Example 2 was subjected to dispersibility testing: Malvern laser particle size analyzer measured D[2,1]: 2.05 μm.

[0056] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 1.85 μm.

[0057] The dispersion index S = D[2,1] / N = 2.05 / 1.85≈1.11 is calculated.

[0058] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 93.8%.

[0059] Comparative Example 2 This comparative example provides a method for preparing ternary single-crystal materials for lithium-ion batteries. The raw materials and steps are the same as in Example 1, except that boron nitride is not added as an additive.

[0060] The ternary cathode material prepared in Comparative Example 2 was subjected to dispersibility testing: Malvern laser particle size analyzer measured D[2,1]: 2.39 μm.

[0061] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 1.9 μm.

[0062] The dispersion index S = D[2,1] / N = 2.39 / 1.9≈1.25 is calculated.

[0063] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 91.1%.

[0064] Example 3 This embodiment provides a method for preparing a ternary single-crystal material for lithium-ion batteries, which includes the following raw materials: Nickel-cobalt-manganese hydroxide precursor: Ni 0.9 Co 0.05 Mn 0.05 (OH)2, the molar ratio is ; Lithium compounds: Lithium hydroxide (LiOH·H2O); Nitride additive: Aluminum nitride (AlN) and boron nitride (BN) are mixed in a 1:1 mass ratio; Source of coating element: aluminum oxide (Al2O3); Includes the following steps: S1. The precursor and lithium hydroxide are mixed at a lithium to transition metal molar ratio (Li / Me) of 0.75. The mixture is sintered at 720°C for 14 hours under an oxygen-rich atmosphere and then cooled in the furnace to obtain the first material.

[0065] S2. The first material and lithium hydroxide are mixed at a ratio of Li / Me = 1.02, and 600 ppm of AlN / BN mixed additive is added. The mixture is stirred for 15 minutes at 550 r / min using a high-speed mixer. Then, mechanical granulation is carried out using a roller granulator at a pressure of 35 MPa, a roller gap of 0.8 mm, and a feeding frequency of 25 Hz. Finally, the mixture is sintered at 840℃ for 20 hours in an oxygen-enriched atmosphere to obtain the second material.

[0066] S3. The second material is crushed using an air jet crusher at a crushing pressure of 0.2 MPa and a feeding frequency of 15 Hz to obtain the third material.

[0067] S4. The third material is mixed with 1000 ppm of alumina and sintered at 480°C for 15 hours in an oxygen-rich atmosphere to obtain the final ternary cathode material.

[0068] The dispersibility of the ternary cathode material prepared in Example 3 was tested. Malvern laser particle size analyzer measured D[2,1]: 1.94 μm.

[0069] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 1.7 μm.

[0070] The dispersion index S = D[2,1] / N = 1.94 / 1.7≈1.14 is calculated.

[0071] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 90.2%.

[0072] Comparative Example 3 This comparative example provides a method for preparing a ternary single-crystal material for lithium-ion batteries. The raw materials and steps are the same as in Example 1, except that mechanical granulation is not performed during the preparation of the second material.

[0073] The ternary cathode material prepared in Comparative Example 3 was subjected to dispersibility testing: Malvern laser particle size analyzer measured D[2,1]: 2.49 μm.

[0074] Scanning electron microscopy (SEM) was used to analyze 100 primary grains, and the average size N was calculated to be 1.75 μm.

[0075] The dispersion index S = D[2,1] / N = 2.49 / 1.75≈1.42 is calculated.

[0076] Electrochemical performance: Sample A was made into a battery and tested. After 500 cycles at 1C rate within a voltage range of 2.8-4.3V, the capacity retention rate was 86.6%.

[0077] Based on the above experimental results, it can be seen that the ternary cathode material preparation method proposed in this invention exhibits significant advantages in both material dispersibility and electrochemical performance. In Example 1, by introducing aluminum nitride as a thermally conductive additive and combining it with a mechanical granulation process, the dispersibility index S of the prepared material was 1.20, which is superior to that of Comparative Example 1 without aluminum nitride (S=1.49). Further electrochemical testing showed that Example 1 maintained a capacity retention of 91.5% after 500 cycles at 1C, significantly higher than the 88.7% of Comparative Example 1, indicating that the addition of aluminum nitride effectively improved the structural uniformity and cycle stability of the material. In Example 2, boron nitride was used as an additive, and its dispersibility index S was further optimized to 1.11. After 500 cycles, the capacity retention reached 93.8%, significantly higher than that of Comparative Example 2 without boron nitride (91.1%), indicating that different nitrides as thermally conductive agents all contribute to improving the particle dispersibility and electrochemical performance of the material. In Example 3, aluminum nitride and boron nitride were used in combination. The dispersibility index was 1.14 and the capacity retention rate was 90.2%, which was still better than the comparative example 3 (S=1.42, capacity retention rate 86.6%) without mechanical granulation. This further verified the important role of mechanical granulation in enhancing particle contact and optimizing thermal uniformity.

[0078] In summary, by introducing nitride thermal conductive agents and mechanical granulation process, this invention can systematically improve the dispersibility of ternary materials and effectively improve the cycle life and capacity retention of batteries, demonstrating good process controllability and potential for large-scale production.

[0079] 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 ternary single-crystal material for lithium-ion batteries, characterized in that, The hard agglomeration degree S of the ternary single crystal material is 1-1.3; The hard agglomeration degree S is calculated using the following formula: Where D[2,1] is the average area diameter of the sample tested by the laser particle size analyzer, and the primary grain size N is the primary grain size obtained by calculating the average of the major and minor axes of at least 50 primary grains in the material electron microscope image statistics and then taking the arithmetic mean.

2. A method for preparing a ternary single-crystal material for lithium-ion batteries as described in claim 1, characterized in that, Includes the following steps: The first material is obtained by first sintering a nickel-cobalt-manganese compound and a lithium compound in a certain proportion. The first material is mixed with a lithium compound in a certain proportion and nitride is added. The mixture is then mechanically granulated and sintered a second time to obtain the second material. The second material is then pulverized to obtain the third material. The third material is then mixed with an inert element and sintered a third time to obtain the ternary single crystal material.

3. The method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The nickel-cobalt-manganese compound and the lithium compound are mixed, wherein the ratio of the molar number of lithium element to the molar number of transition metal in the nickel-cobalt-manganese compound is 0.5-0.95; the first material and the lithium compound are mixed, wherein the ratio of the molar number of lithium element to the molar number of transition metal in the first material is 1.0-1.

1.

4. The method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The nickel-cobalt-manganese compound is selected from at least one of nickel-cobalt-manganese hydroxide or nickel-cobalt-manganese oxide, wherein the molar number of nickel element accounts for 0.6-0.95% of the total molar number of the three transition metals nickel, cobalt, and manganese; the lithium compound is selected from at least one of lithium carbonate or lithium hydroxide.

5. The method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The nitride is selected from at least one of aluminum nitride and boron nitride, and the addition ratio of the nitride is 300-4000 ppm.

6. The method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The inert element is selected from at least one of aluminum, titanium or tungsten, and the coating amount of the inert element is 300-3000 ppm.

7. The method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The mixing process employs a high-speed mixer with a mixing time of 5-20 minutes and a rotation speed of 200-600 r / min.

8. A method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The granulation process uses a roller granulator with a granulation pressure of 10-40 MPa, a roller gap of 0.5-2.0 mm, and a feeding frequency of 10-45 Hz.

9. A method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The first, second, and third sintering processes all employ a high-temperature roller furnace, and all sintering is carried out in air or an oxygen-enriched atmosphere. The temperature of the first sintering is 600-900℃, and the sintering time is 14-20 hours. The temperature of the second sintering is 800-980℃, and the sintering time is 20-25 hours. The temperature of the third sintering is 400-600℃, and the sintering time is 14-20 hours.

10. A method for preparing a ternary single-crystal material for lithium-ion batteries according to claim 2, characterized in that, The crushing process uses an airflow crusher with a crushing pressure of 0.1-0.7 MPa and a feeding frequency of 5-50 Hz.

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