Method for drying positive electrode material and method for producing the same

Abstract

This invention discloses a method for preparing cathode materials, specifically a method for drying and producing cathode materials. The drying method includes: rapid heating: rapidly raising the temperature of the ternary cathode material containing water to 100–110°C; slow heating: slowly raising the temperature of the ternary cathode material to 118–122°C, then adjusting the vacuum to -50 kPa–-80 kPa; pressure relief vacuum cycle: performing 5–7 pressure relief vacuum operations, each lasting 10–12 minutes. Each pressure relief vacuum operation involves: introducing nitrogen to adjust the vacuum to -22 kPa–-18 kPa for 1–6 minutes, then stopping the nitrogen supply and increasing the vacuum pump power to restore the vacuum to -50 kPa–-80 kPa; quantitative drying: raising the temperature to 145–155°C until the target moisture content is achieved. This drying method is time-efficient and yields good drying results.

Description

Technical Field

[0001] This invention relates to the field of cathode material preparation technology, and more specifically, to a drying method for cathode materials and a production method thereof. Background Technology

[0002] The effect of moisture content on powder flowability is an important factor that is often overlooked.

[0003] When powder is dry, its flowability is generally good. However, if it is too dry, electrostatic attraction will cause particles to attract each other, reducing flowability. When it contains a small amount of moisture, the moisture is adsorbed onto the particle surface and exists as surface-adsorbed water, which has little impact on the flowability of the powder. As the moisture content increases, a water film forms around the adsorbed water on the particles, increasing the resistance to relative movement between particles and causing the flowability of the powder to decrease.

[0004] When ternary cathode powder material with a water content of about 10% by mass is squeezed and moved in a plow dryer under the external force of the plow dryer, the cathode powder is prone to friction due to excessive friction, which causes friction between the powder particles (about 10μm in diameter). The surface structure of the particles is damaged, and even the particles may break, which in turn affects the performance of the cathode material. After being made into a battery, it is easy to generate gas, which deteriorates the battery performance and creates safety hazards.

[0005] Secondly, during the drying process of the plow blade, the external force of the plow blade, when the initial moisture content is relatively high, can easily cause the powder material to agglomerate into balls. The agglomerated balls are heated unevenly inside and out, and after the agglomerated balls are heated and clump together, they are difficult to break apart under the impact of the plow blade. This uneven drying affects the coating of the material with surface-modifying additives in subsequent processes.

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

[0007] The purpose of this invention is to provide a drying method for positive electrode materials and a production method thereof.

[0008] This invention is implemented as follows:

[0009] In a first aspect, the present invention provides a method for drying a positive electrode material, comprising:

[0010] Rapid heating: Control the heating rate of the dryer containing the hydrated ternary cathode material to be 2.0-3.0℃ / min, so that the temperature of the hydrated ternary cathode material can be rapidly increased to 100-110℃;

[0011] Slow heating: Control the heating rate of the dryer to 1.0~2.0℃ / min, so that the temperature of the ternary cathode material is slowly increased to 118~122℃, and then the vacuum degree is adjusted to -50kPa~-80kPa;

[0012] Depressurization vacuum cycle: Perform 5 to 7 depressurization vacuum operations, each lasting 10 to 12 minutes. The depressurization vacuum operation is performed as follows: nitrogen gas is introduced to adjust the vacuum level to -22 kPa to -18 kPa for 1 to 6 minutes. Then, nitrogen gas is introduced and the vacuum pump power is increased to restore the vacuum level to -50 kPa to -80 kPa.

[0013] Quantitative drying: Increase the temperature to 145-155℃ until the target moisture content is achieved;

[0014] The dryer has a built-in agitator, and the entire drying process is carried out with continuous stirring.

[0015] In an optional implementation, the agitator speed inside the dryer during rapid heating is 19–21 Hz;

[0016] During the slow heating process, the agitator speed inside the dryer is 34-36 Hz.

[0017] During the depressurization vacuum cycle, the agitator speed inside the dryer is 34–36 Hz.

[0018] During quantitative drying, the agitator inside the dryer rotates at a speed of 40–50 Hz.

[0019] In an optional embodiment, a preheating step is included before the rapid heating step. The preheating step involves heating the dryer without the hydrated ternary cathode material to 55-65°C, and then placing the hydrated ternary cathode material into the dryer after preheating.

[0020] In an optional implementation, the vacuum level of the dryer is -19 to -21 kPa during the rapid heating process;

[0021] Optionally, during the quantitative drying process, the vacuum level inside the dryer is -85 to -95 kPa.

[0022] In an optional embodiment, the water content of the hydrated ternary cathode material is 7-15%.

[0023] In an optional implementation, during the depressurization vacuum cycle, the nitrogen gas introduced is preheated nitrogen gas with a temperature of 80–100°C.

[0024] In an optional embodiment, the dryer has a heating jacket, which is heated by introducing high-temperature steam into the heating jacket. During the rapid heating phase, the high-temperature steam flow rate is set to the maximum; during the slow heating phase and the depressurization vacuum circulation phase, the high-temperature steam flow rate is set to 65-75% of the maximum flow rate; and during the quantitative drying phase, the high-temperature steam flow rate is set to 45-55% of the maximum flow rate.

[0025] In an optional implementation, after quantitative drying is completed, the dried material is placed in a cooling tank and sealed for cooling.

[0026] Secondly, the present invention provides a method for producing a ternary cathode material, including a drying method as described in any of the foregoing embodiments.

[0027] The present invention has the following beneficial effects:

[0028] The drying method provided in this invention divides the drying process into multiple stages. In the rapid heating stage, the temperature of the ternary cathode material containing water is rapidly increased to 100-110°C, which can effectively prevent the ternary cathode material from agglomerating. In the slow heating stage, the vacuum degree is controlled to keep the ternary cathode material in a high vacuum environment, allowing moisture to escape quickly and promoting faster drying. The pressure relief vacuum circulation operation allows the moisture in the small particles that agglomerate due to stirring in the dryer to escape after pressure relief, which can reduce the proportion of micro-agglomeration and improve the uniformity of drying. Finally, quantitative drying is performed by heating to ensure thorough drying.

[0029] Therefore, the drying method provided in this embodiment of the invention performs multi-stage drying operations, which avoids balling and clumping of ternary cathode materials with high moisture content during the drying process, avoids uneven drying caused by this, improves the uniformity of the coating of cathode materials on the surface of subsequent processes, thereby improving the performance of ternary cathode materials, while also improving the uniformity of drying, reducing drying time, and reducing costs and increasing efficiency. Detailed Implementation

[0030] 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.

[0031] The drying method and production method of the cathode material provided in the embodiments of the present invention will be described in detail below.

[0032] This invention provides a method for drying a positive electrode material, comprising:

[0033] Rapid heating: Control the heating rate of the dryer containing the hydrated ternary cathode material to be 2.0-3.0℃ / min, so that the temperature of the hydrated ternary cathode material can be rapidly increased to 100-110℃;

[0034] Slow heating: Control the heating rate of the dryer to 1.0~2.0℃ / min, so that the temperature of the ternary cathode material is slowly increased to 118~122℃, and then the vacuum degree is adjusted to -50kPa~-80kPa;

[0035] Depressurization vacuum cycle: Perform 5 to 7 depressurization vacuum operations, each lasting 10 to 12 minutes. The operation method for each depressurization vacuum cycle is as follows: introduce nitrogen to adjust the vacuum level to -22 kPa to -18 kPa for 1 to 6 minutes, then stop introducing nitrogen and increase the vacuum pump power to restore the vacuum level to -50 kPa to -80 kPa.

[0036] Quantitative drying: Increase the temperature to 145-155℃ until the target moisture content is achieved;

[0037] The dryer has a built-in agitator, and the entire drying process is carried out with continuous stirring.

[0038] The drying method provided in this invention divides the drying process into multiple stages. In the rapid heating stage, the temperature of the ternary cathode material containing water is rapidly increased to 100-110°C, which can effectively prevent the ternary cathode material from agglomerating. In the slow heating stage, the vacuum degree is controlled to keep the ternary cathode material in a high vacuum environment, allowing moisture to escape quickly and promoting faster drying. The pressure relief vacuum circulation operation allows the moisture in the small particles that agglomerate due to stirring in the dryer to escape after pressure relief, which can reduce the proportion of micro-agglomeration and improve the uniformity of drying. Finally, quantitative drying is performed by heating to ensure thorough drying.

[0039] Therefore, the drying method provided in this embodiment of the invention performs multi-stage drying operations, which avoids balling and clumping of ternary cathode materials with high moisture content during the drying process, avoids uneven drying caused by this, improves the uniformity of the coating of cathode materials on the surface of subsequent processes, thereby improving the performance of ternary cathode materials, while also improving the uniformity of drying, reducing drying time, and reducing costs and increasing efficiency.

[0040] Specifically, the drying method is as follows:

[0041] S1, Preheating

[0042] The dryer is preheated to 55–65°C (e.g., 55°C, 60°C, or 65°C).

[0043] Optionally, in a preferred embodiment of this application, the dryer used has a heating jacket, and heating is achieved by introducing high-temperature steam into the heating jacket.

[0044] Furthermore, the dryer is a plow dryer, in which the plow blades (agitators) inside the dryer rotate and turn the material during the drying process to ensure thorough and uniform drying.

[0045] S2, Rapid Heating

[0046] The hydrated ternary cathode material is placed in a dryer, and the dryer is heated rapidly. The heating rate of the dryer for the hydrated ternary cathode material is 2.0 to 3.0 °C / min (e.g., 2.0 °C / min, 2.5 °C / min, or 3.0 °C / min), so that the temperature of the hydrated ternary cathode material is rapidly increased to 100 to 110 °C (e.g., 100 °C, 105 °C, or 110 °C).

[0047] The method to achieve rapid heating in this stage is to maximize the flow rate of high-temperature steam.

[0048] Preferably, to further ensure that no balls or clumps form during the drying process, the agitator speed inside the dryer is 19–21 Hz (e.g., 19 Hz, 20 Hz, or 21 Hz) during rapid heating.

[0049] Preferably, to further improve the drying effect, the vacuum degree of the dryer in this step is -19 to -21 MPa (e.g., -19 MPa, -20 MPa or -21 MPa).

[0050] In this step, a low vacuum degree, increased heating rate, and low stirring intensity are first adopted to allow the material to heat up quickly and uniformly. The heat conduction of the ternary powder, water, and air is utilized. When the moisture content is high, the friction between the materials is relatively large and the material flowability is poor. The low stirring intensity can reduce the friction intensity between the ternary cathode powder particles, thereby reducing the generation of micro powder and improving the performance of the ternary cathode material. At the same time, it improves the uniformity of drying, reduces drying time, and reduces costs and increases efficiency.

[0051] S3, Slow Heating

[0052] Once the temperature of the ternary cathode material inside the dryer reaches 100–110°C (e.g., 100°C, 105°C, or 110°C), control the heating rate of the dryer to 1.0–2.0°C / min (e.g., 1.0°C / min, 1.5°C / min, or 2.0°C / min), allowing the temperature of the ternary cathode material to slowly rise to 118–122°C (e.g., 118°C, 120°C, or 122°C). Then, adjust the vacuum level to -50 kPa to -80 kPa (e.g., -50 kPa, -60 kPa, -70 kPa, or -80 kPa).

[0053] The method to achieve slow heating in this stage is to increase the flow rate of high-temperature steam to 65-75% of the maximum flow rate.

[0054] Preferably, to further ensure that no balls or clumps form during the drying process, the agitator speed inside the dryer is 34–36 Hz (e.g., 34 Hz, 35 Hz, or 36 Hz) during the slow heating process.

[0055] S4, Pressure Relief Vacuum Cycle

[0056] Perform 5 to 7 (e.g., 5, 6, or 7) depressurization vacuum operations, each lasting 10 to 12 minutes (e.g., 10, 11, or 12 minutes). Each depressurization vacuum operation is performed as follows: preheated nitrogen is introduced to adjust the vacuum level to -22 kPa to -18 kPa (e.g., -22 kPa, -20 kPa, or -18 kPa) for 1 to 6 minutes (e.g., 1 minute, 2 minutes, 4 minutes, or 6 minutes). Then, the nitrogen supply is stopped and the vacuum pump power is increased to restore the vacuum level to -50 kPa to -80 kPa (e.g., -50 kPa, -60 kPa, -70 kPa, or -80 kPa).

[0057] By performing 5 to 7 vacuum decompression operations, the moisture in the small particles that agglomerate due to stirring in the dryer can be released after decompression, which can reduce the proportion of micro-agglomeration into spheres, improve the uniformity of drying, and thus ensure thorough drying and effectively prevent drying from clumping.

[0058] During this stage, the temperature inside the dryer is maintained at 118–122°C (e.g., 118°C, 120°C, or 122°C).

[0059] Preferably, to further ensure that no balls or clumps form during the drying process, the stirrer speed is 34–36 Hz (e.g., 34 Hz, 35 Hz, or 36 Hz) in this step.

[0060] Preferably, in this step, in order to avoid the temperature of the drying function decreasing, the nitrogen gas introduced is preheated nitrogen gas with a temperature of 80-100°C (e.g., 80°C, 90°C or 100°C).

[0061] S5, quantitative drying

[0062] After depressurization and vacuum circulation, raise the dryer temperature to 145–155°C (e.g., 145°C, 150°C, or 155°C) and keep it at that temperature until the target moisture content is achieved.

[0063] Preferably, to further ensure that no balls or clumps form during the drying process, the stirrer speed is 40-50 Hz (e.g., 40 Hz, 45 Hz or 50 Hz) in this step.

[0064] Optionally, in this stage, the high-temperature steam flow rate is increased to 45-55% (e.g., 45%, 50% or 55%) of the maximum flow rate, so that the temperature rises to 145-155°C (e.g., 145°C, 150°C or 155°C).

[0065] Optionally, the moisture content of the dried hydrated ternary cathode material is 7–15%.

[0066] Optionally, to ensure better drying results, the vacuum level inside the dryer in this step is -85 to -95 kPa (e.g., -85 kPa, -90 kPa, or -95 kPa).

[0067] The production method of ternary cathode material provided in the embodiments of the present invention includes the drying method provided in the embodiments of the present invention.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] Example 1

[0070] This embodiment provides a drying method, including:

[0071] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 60°C.

[0072] The NCM811 polycrystalline spherical cathode material was placed in a plow dryer, and the moisture content of the NCM811 polycrystalline spherical cathode material was 7.1%.

[0073] The steam flow rate of the dryer is adjusted to the maximum, and the NCM811 polycrystalline spherical cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the NCM811 polycrystalline spherical material to 100℃. During this stage, the vacuum degree is adjusted to -20kPa and the stirring speed of the dryer is 20Hz.

[0074] Adjust the steam flow rate of the dryer to 70% of the maximum, so that the dryer heats up to 118°C at a heating rate of about 2.5°C / min. During this process, the vacuum degree is adjusted to -60kPa and the drying speed is adjusted to 35Hz.

[0075] Five depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -20 kPa for 6 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -60 kPa, which took about 4 minutes.

[0076] Adjust the steam flow rate of the dryer to 50% of the maximum, and heat the dryer to 145℃ at a heating rate of about 2.0℃ / min. In this step, the stirring speed of the plow dryer is adjusted to 45Hz and the vacuum degree is -85kPa, until the moisture content of the positive electrode material is 0.11%.

[0077] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process, from the initial placement of the ternary cathode material in the desiccant, takes a total of 115 minutes.

[0078] Example 2

[0079] This embodiment provides a drying method, including:

[0080] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 55°C.

[0081] The NCM805 single crystal cathode material was placed in a plow dryer, and the water content of the NCM805 single crystal cathode material was 7.1%.

[0082] The steam flow rate of the dryer is adjusted to the maximum, and the NCM805 single crystal cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the temperature of the NCM805 single crystal cathode material to 100℃. During this stage, the vacuum degree is adjusted to -20kPa and the stirring speed of the dryer is 20Hz.

[0083] Adjust the steam flow rate of the dryer to 70% of the maximum, so that the dryer heats up to 118°C at a heating rate of about 2.5°C / min. During this process, the vacuum degree is adjusted to -50kPa and the drying speed is adjusted to 35Hz.

[0084] Five depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -20 kPa for 6 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -60 kPa, which took about 4 minutes.

[0085] Adjust the steam flow rate of the dryer to 50% of the maximum, and heat the dryer to 145℃ at a heating rate of about 2.0℃ / min. In this step, the stirring speed of the plow dryer is adjusted to 45Hz and the vacuum degree is -85kPa, until the moisture content of the positive electrode material is 0.12%.

[0086] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process takes 160 minutes.

[0087] Example 3

[0088] This embodiment provides a drying method, including:

[0089] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 65°C.

[0090] The NCM811 polycrystalline spherical cathode material was placed in a plow dryer, and the moisture content of the NCM811 polycrystalline spherical cathode material was 9.25%.

[0091] The steam flow rate of the dryer is adjusted to the maximum, and the NCM811 polycrystalline spherical cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the NCM811 polycrystalline spherical material to 110℃. During this stage, the vacuum degree is adjusted to -19kPa and the stirring speed of the dryer is 19Hz.

[0092] Adjust the steam flow rate of the dryer to 65% of the maximum, so that the dryer heats up to 118°C at a heating rate of about 2.2°C / min. During this process, the vacuum degree is adjusted to -80kPa and the drying speed is adjusted to 34Hz.

[0093] Five depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -22 kPa for 5 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -80 kPa, which took about 5 minutes.

[0094] Adjust the steam flow rate of the dryer to 45% of the maximum, and heat the dryer to 155℃ at a heating rate of about 1.8℃ / min. In this step, the stirring speed of the plow dryer is adjusted to 40Hz and the vacuum degree is -95kPa, until the moisture content of the positive electrode material is 0.17%.

[0095] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process takes 130 minutes.

[0096] Example 4

[0097] This embodiment provides a drying method, including:

[0098] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 65°C.

[0099] The NCM805 single crystal cathode material was placed in a plow dryer, and the water content of the NCM805 single crystal cathode material was 9.25%.

[0100] The steam flow rate of the dryer is adjusted to the maximum, and the NCM805 single crystal cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the temperature of the NCM805 single crystal cathode material to 100℃. During this stage, the vacuum degree is adjusted to -20kPa and the stirring speed of the dryer is 20Hz.

[0101] Adjust the steam flow rate of the dryer to 75% of the maximum, so that the dryer heats up to 120°C at a heating rate of about 2.6°C / min. During this process, the vacuum degree is adjusted to -70kPa and the drying speed is adjusted to 36Hz.

[0102] Seven depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -20 kPa for 5 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -70 kPa, which took about 5 minutes.

[0103] Adjust the steam flow rate of the dryer to 45% of the maximum, and heat the dryer to 150°C at a heating rate of about 1.8°C / min. In this step, the stirring speed of the plow dryer is adjusted to 45Hz and the vacuum degree is -90kPa, until the moisture content of the positive electrode material is 0.18%.

[0104] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process takes 180 minutes.

[0105] Example 5

[0106] This embodiment provides a drying method, including:

[0107] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 60°C.

[0108] The NCM811 polycrystalline spherical cathode material was placed in a plow dryer, and the moisture content of the NCM811 polycrystalline spherical cathode material was 12.21%.

[0109] The steam flow rate of the dryer is adjusted to the maximum, and the NCM811 polycrystalline spherical cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the temperature of the NCM811 polycrystalline spherical material to 105℃. During this stage, the vacuum degree is adjusted to -21kPa and the stirring speed of the dryer is 21Hz.

[0110] Adjust the steam flow rate of the dryer to 65% of the maximum, so that the dryer heats up to 122°C at a heating rate of about 2.2°C / min. During this process, the vacuum degree is adjusted to -60kPa and the drying speed is adjusted to 36Hz.

[0111] Six depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -20 kPa for 6 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -60 kPa, which took about 4 minutes.

[0112] Adjust the steam flow rate of the dryer to 50% of the maximum, and heat the dryer to 145℃ at a heating rate of about 2.0℃ / min. In this step, the stirring speed of the plow dryer is adjusted to 45Hz and the vacuum degree is -85kPa, until the moisture content of the positive electrode material is 0.14%.

[0113] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process, from the initial placement of the ternary cathode material in the desiccant, takes a total of 140 minutes.

[0114] Example 6

[0115] This embodiment provides a drying method, including:

[0116] The plow dryer is preheated. During the preheating process, high-temperature steam is introduced into the jacket of the dryer to bring the temperature of the dryer to 65°C.

[0117] The NCM805 single crystal cathode material was placed in a plow dryer, and the water content of the NCM805 single crystal cathode material was 12.21%.

[0118] The steam flow rate of the dryer is adjusted to the maximum, and the NCM805 single crystal cathode material placed in the plow dryer is rapidly heated at a rate of about 3.0℃ / min to raise the temperature of the NCM805 single crystal cathode material to 100℃. During this stage, the vacuum degree is adjusted to -20kPa and the stirring speed of the dryer is 20Hz.

[0119] Adjust the steam flow rate of the dryer to 75% of the maximum, so that the dryer heats up to 118°C at a heating rate of about 2.6°C / min. During this process, the vacuum degree is adjusted to -70kPa and the drying speed is adjusted to 35Hz.

[0120] Seven depressurization vacuum cycles were performed, each lasting 10 minutes. The depressurization vacuum operation was performed as follows: preheated nitrogen was introduced to adjust the vacuum level to -20 kPa for 5 minutes, then the nitrogen was introduced and the vacuum pump power was increased to restore the vacuum level to -60 kPa, which took about 5 minutes.

[0121] Adjust the steam flow rate of the dryer to 45% of the maximum, and heat the dryer to 145℃ at a heating rate of about 1.8℃ / min. In this step, the stirring speed of the plow dryer is adjusted to 45Hz and the vacuum degree is -85kPa, until the moisture content of the positive electrode material is 0.15%.

[0122] In step six above, the drying process is completed by removing the material from the plow dryer and then placing it in a cooling tank. The entire drying process takes 200 minutes.

[0123] Comparative Example 1

[0124] The existing method was used to dry NCM811 polycrystalline spherical cathode material. The drying steps were as follows: the moisture content of the NCM811 polycrystalline spherical cathode material before drying was 7.1%. During the drying process, the steam flow rate of the plow dryer was always at the maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.12%. The total drying time was 150 min, thus completing the drying of the NCM811 polycrystalline spherical cathode material.

[0125] Comparative Example 2

[0126] The existing method was used to dry the NCM805 single crystal cathode material. The drying steps were as follows: the moisture content of the NCM805 single crystal cathode material before drying was 7.1%. During the drying process, the steam flow rate of the plow dryer was always at the maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.13%. The total drying time was 180 min, thus completing the drying of the NCM805 single crystal cathode material.

[0127] Comparative Example 3

[0128] The existing method was used to dry the NCM811 polycrystalline spherical cathode material. The drying steps were as follows: the moisture content of the NCM811 polycrystalline spherical cathode material before drying was 9.25%. During the drying process, the steam flow rate of the plow dryer was always at its maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.17%. The total drying time was 160 min, thus completing the drying of the NCM811 polycrystalline spherical cathode material.

[0129] Comparative Example 4

[0130] The existing method was used to dry the NCM805 single crystal cathode material. The drying steps were as follows: the moisture content of the NCM805 single crystal cathode material before drying was 9.25%. During the drying process, the steam flow rate of the plow dryer was always at the maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.17%. The total drying time was 205 min, thus completing the drying of the NCM805 single crystal cathode material.

[0131] Comparative Example 5

[0132] The existing method was used to dry the NCM811 polycrystalline spherical cathode material. The drying steps were as follows: the moisture content of the NCM811 polycrystalline spherical cathode material before drying was 12.21%. During the drying process, the steam flow rate of the plow dryer was always at its maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.14%. The total drying time was 180 min, thus completing the drying of the NCM811 polycrystalline spherical cathode material.

[0133] Comparative Example 6

[0134] The existing method was used to dry the NCM805 single crystal cathode material. The drying steps were as follows: the moisture content of the NCM805 single crystal cathode material before drying was 12.21%. During the drying process, the steam flow rate of the plow dryer was always at the maximum, the vacuum degree was adjusted to -85 kPa, the stirring frequency was 35 Hz, and the moisture content was reduced to 0.15%. The total drying time was 240 min, thus completing the drying of the NCM805 single crystal cathode material.

[0135] Experimental Example

[0136] The moisture content of each embodiment and comparative example before and after drying was tested, and the results are recorded in Table 1.

[0137] Table 1. Moisture content before and after drying in each embodiment and comparative example.

[0138]

[0139]

[0140] As can be seen from the table above, the drying methods provided in the various embodiments of the present invention have a lower moisture content after drying, while requiring less drying time compared to the corresponding comparative examples (prior art).

[0141] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 drying method of a positive electrode material, characterized by, include: Rapid heating: Control the heating rate of the dryer containing the hydrated ternary cathode material to be 2.0~3.0℃ / min, so that the temperature of the hydrated ternary cathode material can be rapidly increased to 100~110℃; Slow heating: Control the heating rate of the dryer to 1.0~2.0℃ / min, so that the temperature of the ternary cathode material is slowly increased to 118~122℃, and then the vacuum degree is adjusted to -50kPa~-80kPa; Pressure relief vacuum cycle: Perform 5 to 7 pressure relief vacuum operations, each lasting 10 to 12 minutes. Each pressure relief vacuum operation is performed as follows: nitrogen gas is introduced to adjust the vacuum level to -22 kPa to -18 kPa for 1 to 6 minutes. Then, nitrogen gas is introduced and the vacuum pump power is increased to restore the vacuum level to -50 kPa to -80 kPa. Quantitative drying: Increase the temperature to 145~155℃ until the target moisture content is achieved; The dryer has a built-in agitator, and the entire drying process is carried out with continuous stirring.

2. The drying method according to claim 1, characterized in that, During the rapid heating process, the agitator inside the dryer rotates at 19~21Hz; During the slow heating process, the agitator speed inside the dryer is 34~36Hz; During the depressurization vacuum cycle, the agitator speed inside the dryer is 34~36Hz; During quantitative drying, the agitator inside the dryer rotates at a speed of 40~50Hz.

3. The drying method according to claim 1, characterized in that, Before the rapid heating step, there is also a preheating step, which involves heating the dryer without the hydrated ternary cathode material to 55~65℃. After the preheating is completed, the hydrated ternary cathode material is placed in the dryer.

4. The drying method according to claim 1, characterized by, During the rapid heating process, the vacuum degree of the dryer is -19~-21KPa; During the quantitative drying process, the vacuum degree inside the dryer is -85 to -95 kPa.

5. The drying method according to claim 1, characterized in that, The water content of the aqueous ternary cathode material is 7-15%.

6. The drying method according to claim 1, characterized in that, During the depressurization vacuum cycle, the nitrogen gas introduced is preheated nitrogen gas with a temperature of 80~100℃.

7. The drying method according to claim 1, characterized in that, The dryer has a heating jacket, which is heated by introducing high-temperature steam into the heating jacket. During the rapid heating stage, the high-temperature steam flow rate is turned up to the maximum; during the slow heating stage and the depressurization vacuum circulation stage, the high-temperature steam flow rate is turned up to 65-75% of the maximum flow rate; and during the quantitative drying stage, the high-temperature steam flow rate is turned up to 45-55% of the maximum flow rate.

8. The drying method according to claim 1, characterized in that, After quantitative drying is completed, the dried material is placed in a cooling tank and sealed for cooling.

9. A method for producing a ternary cathode material, characterized in that, Including the drying method as described in any one of claims 1 to 8.

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