Mixing and sintering system, method for preparing powder by using same and positive electrode material

Abstract

The application discloses a mixing and sintering system, a method for preparing powder by using the same and a positive electrode material, and the system comprises a reactor body with a stirring device inside, the stirring device comprises one or more stirring rods, and the free end of the stirring rod is adjustable in distance from the inner wall of the reactor body. The method is to add raw materials into the reactor body, adjust the distance between the free end of the stirring rod and the inner wall of the reactor body to 1-10 cm, complete mixing at a first rotating speed, adjust the distance between the free end of the stirring rod and the inner wall of the reactor body to 0-0.1 cm, and perform mechanical heat generation at a second rotating speed to make the temperature of the reactor body reach 700-1500 DEG C, wherein the second rotating speed is greater than the first rotating speed. The application utilizes mechanical method to generate high heat for sintering, realizes raw material mixing and sintering by changing the distance between the stirring rod and the inner wall of the reactor body and the rotating speed, and the kiln equipment is omitted, so that the processing cost of the lithium ion positive electrode material is greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heating reaction, and particularly relates to a mixing and sintering system, a method for preparing a powder by using the same, and a positive electrode material. BACKGROUND

[0002] Lithium ion positive electrode materials are widely used in 3C, energy storage, electric vehicles and other fields due to their high energy density, high energy conversion efficiency, high working voltage, long cycle life, no memory effect and other advantages. At present, the preparation of lithium ion positive electrode materials mainly adopts a solid phase sintering method, and in actual production, a kiln (such as a push plate furnace, a roller furnace, a box furnace or a rotary kiln) is mainly used to realize the sintering. Due to the long length of the kiln equipment, which can reach more than 20 meters, the volume is large, the energy consumption is high, and the consumption of site, equipment and energy will be caused. SUMMARY

[0003] The application provides a mixing and sintering system, a method for preparing a powder by using the same, and a positive electrode material. High heat is generated by a mechanical method to sinter the lithium ion positive electrode material. By changing the distance between the stirring rod and the inner wall of the reactor body, as well as the rotating speed and time, the raw material mixing and sintering synthesis are realized. The process transmission of the material is saved, the mixing and sintering reaction processes are combined to a great extent, and the kiln equipment is removed, so that the processing cost of the lithium ion positive electrode material is greatly reduced.

[0004] The technical scheme of the application is as follows:

[0005] A mixing and sintering system comprises a reactor body and a driving device. The reactor body has a stirring device inside; the driving device is arranged outside the reactor body and connected with the stirring device to drive the stirring device.

[0006] The stirring device comprises one or more stirring rods, and the distance between the free end of the stirring rod and the inner wall of the reactor body is adjustable to form a first working state or a second working state.

[0007] Further, when the distance between the free end of the stirring rod and the inner wall of the reactor body is greater than 1 cm, the stirring rod can scatter and mix the material to form the first working state; when the distance between the free end of the stirring rod and the inner wall of the reactor body is less than 1 cm, the free end of the stirring rod can generate heat by friction with the reactor body to form the second working state.

[0008] Further, the free end of the stirring rod has a friction part, and when the stirring rod is in the second working state, the friction part is in contact with the inner wall of the reactor body.

[0009] Preferably, the reactor body has an axially arranged rotating shaft, and the opposite end of the free end of the stirring rod is connected to the rotating shaft; the friction part is a friction roller, and the axis of the friction roller is parallel to the axis of the rotating shaft. Rotation of the rotating shaft enables the free end of the stirring rod to rotate, thereby stirring the material and mechanically generating heat by friction with the inner wall of the reactor body.

[0010] Preferably, the stirring rod can be distributed in multiple layers along the axis of the rotating shaft, or uniformly distributed in each layer.

[0011] More preferably, the length of the friction roller is 1 / 3-2 / 3 of the height of the reactor body; the ratio of the diameter d of the friction roller to the length L of the friction roller is 1 / 3-1 / 2.

[0012] More preferably, when the stirring rod is in the second working state, the distance between the friction roller and the inner wall of the reactor body is 0-0.1 cm.

[0013] Through the above parameter settings, the effect of mechanical heat generation can be maximized to generate high heat.

[0014] Further, the system further comprises a temperature detection device and a control device, the temperature detection device comprises a detection end and an output end, the detection end is located inside the reactor body, and the output end is signal connected with the control device.

[0015] The control device is also signal connected with the driving device and the stirring rod respectively, and the control device can adjust the rotating speed of the driving device and the distance between the free end of the stirring rod and the inner wall of the reactor body according to the signal of the detection end.

[0016] Further, the stirring rod comprises an inner tube and an outer tube connected with each other by threads or buckles, the inner tube is signal connected with the control device, and the control device can control the inner tube to rotate or stretch to adjust the length of the stirring rod, so as to adjust the distance between the stirring rod and the inner wall of the reactor body. In addition, any other means that can achieve the purpose can also be used.

[0017] The application also provides a method for preparing a powder by using the mixing and sintering system, comprising the following steps:

[0018] Mixing: the raw materials are added into the reactor body, the distance between the free end of the stirring rod and the inner wall of the reactor body is adjusted to 1-10 cm, and the mixing is completed at a first rotating speed;

[0019] Sintering: the distance between the free end of the stirring rod and the inner wall of the reactor body is adjusted to be 0-0.1 cm, mechanical heat generation is carried out at a second rotating speed to make the temperature T of the inner wall of the reactor body reach a range of 700-1500 DEG C, wherein the second rotating speed is greater than the first rotating speed.

[0020] Further, the raw material comprises a precursor of the positive electrode material and a lithium source, wherein the molar ratio of the precursor in terms of Me and the lithium source in terms of Li satisfies n(Li):n(Me)=0.95-1.30:1, wherein Me is a collective term of metal elements in the precursor.

[0021] Preferably, the positive electrode material is selected from one or more of a multi-element positive electrode material, lithium cobaltate, lithium iron phosphate or lithium manganese iron phosphate.

[0022] Preferably, the first rotating speed ranges from 300-600 rpm, and the mixing time is 1-90 min.

[0023] Preferably, the second rotating speed ranges from 3000-10000 rpm, and the sintering time is 0.5-10 h.

[0024] During the mixing and sintering processes, the temperature detection device in the system detects the temperature in the reactor body and feeds back to the control device, which adjusts the length of the stirring rod according to the temperature through the driving device to control the distance between the free end of the stirring rod and the inner wall of the reactor body, and adjusts the rotating speed of the stirring rod through the driving device. The control of the distance and the rotating speed can realize accurate control of the temperature in the reactor after mechanical heat generation. Meanwhile, the specific rotating speed can be slightly different according to the material of the free end of the stirring rod.

[0025] When the sintering is a pre-sintering reaction, the second rotating speed generally ranges from 3500-4500 rpm, and the temperature T of the inner wall of the reactor body generally ranges from 700-850 DEG C.

[0026] When the sintering is a synthesis reaction, the second rotating speed generally ranges from 5000-8000 rpm, the temperature T of the inner wall of the reactor body generally ranges from 1000-1200 DEG C, and the sintering time is about 30-90 min.

[0027] The application also provides a positive electrode material prepared by the mixing and sintering system or the method for preparing a powder by the mixing and sintering system.

[0028] Preferably, the aspect ratio of the positive electrode material is 0.98-1.03.

[0029] Preferably, the average particle size of the positive electrode material is 3-500 microns.

[0030] The present application combines the mixing and sintering of raw materials into one step by designing a stirring device with adjustable distance from the inner wall of the reactor, adding the precursor of the positive electrode material and lithium salt into the reactor in a certain ratio, and changing the distance of the stirring rod from the inner wall of the reactor, as well as the rotation speed and time. This not only saves the process transmission of materials, but also replaces the traditional kiln equipment for solid phase reaction, thereby greatly reducing the processing cost of lithium ion positive electrode materials. In addition, the positive electrode material obtained by traditional sintering has large particle size difference and is not uniform, while the positive electrode material prepared by the system and method of the present application has round and balanced particle size, high energy density and compaction density, and the performance is obviously improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0032] Figure 1 It is a schematic diagram of one of the structures of the mixing and sintering system of Example 1 of the present application.

[0033] Figure 2 It is a SEM image of the lithium ion battery positive electrode material prepared in Example 2 of the present application.

[0034] Figure 3 It is a SEM image of the lithium ion battery positive electrode material prepared in Comparative Example 1 of the present application.

[0035] Explanation of reference signs:

[0036] 1-reactor body; 2-rotating shaft; 3-stirring rod; 4-friction roller; 5-control device; 6-driving device; 7-temperature detection device. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0038] Example 1

[0039] A mixing and sintering system, such as Figure 1 As shown, the reactor includes a reactor body 1 and a drive device 6. The reactor body 1 contains a stirring device; the drive device 6 is located outside the reactor body 1 and connected to the stirring device, used to drive the stirring device. In this embodiment, the reactor body 1 is cylindrical, and the drive device 6 is located above the reactor body 1.

[0040] The stirring device includes one or more stirring rods 3, the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 is adjustable to form a first working state or a second working state. In this embodiment, there are multiple stirring rods 3. Figure 1 The image shown is only one of them and is for illustrative purposes only.

[0041] When the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 is greater than 1 cm, the stirring rod 3 can disperse and mix the material, forming the first working state; when the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 is less than 1 cm, the free end of the stirring rod 3 can generate heat through friction with the reactor body 1, forming the second working state.

[0042] The free end of the stirring rod 3 has a friction part, which contacts the inner wall surface of the reactor body 1 when the stirring rod 3 is in the second working state.

[0043] In this embodiment, the reactor body 1 has an axially arranged rotating shaft 2, and the opposite ends of the free ends of the stirring rod 3 are connected to the rotating shaft 2. In this embodiment, the friction part is a friction roller 4, and the axis of the friction roller 4 is parallel to the axis of the rotating shaft 2. The rotation of the rotating shaft 2 causes the free ends of the stirring rod 3 to rotate, thereby stirring the material and generating mechanical heat through friction with the inner wall of the reactor body 1.

[0044] In a preferred embodiment, the stirring rod 3 may be distributed in multiple layers along the axial direction of the rotating shaft 2, or each layer may be evenly distributed.

[0045] In this embodiment, the length of the friction roller 4 is 1 / 3 of the height of the reactor body 1; the ratio of the diameter d of the friction roller 4 to its length L is between 1 / 3; when the stirring rod 3 is in the second working state, the distance between the friction roller 4 and the inner wall of the reactor body 1 is in the range of 0-0.1cm.

[0046] The mixing and sintering system also includes a temperature detection device 7 and a control device 5. The temperature detection device 7 includes a detection end and an output end. The detection end is located inside the reactor body 1, and the output end is connected to the control device 5 via a signal.

[0047] The control device 5 is also signal connected with the driving device 6 and the stirring rod 3 respectively, and the control device 5 can adjust the rotating speed of the driving device 6 and the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 according to the signal of the detection end.

[0048] In this embodiment, the stirring rod 3 comprises an inner tube and an outer tube which are connected with each other through threads, and the inner tube is signal connected with the control device 5, and the control device 5 can control the inner tube to make rotating motion or telescopic motion to adjust the length of the stirring rod 3, so as to adjust the distance between the stirring rod 3 and the inner wall of the reactor body 1.

[0049] Embodiment 2

[0050] This embodiment provides a method for preparing powder by using the mixing and sintering system in embodiment 1, which comprises the following steps:

[0051] Mixing: the cobalt oxide and the battery-grade lithium carbonate are added into the reactor body 1, the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 is adjusted to 2 cm, and the mixing is completed by stirring at a first rotating speed of 500 rpm for 60 min;

[0052] Sintering: the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 is adjusted to 0.01 cm, and the mechanical heat generation is performed by stirring at a second rotating speed of 8000 rpm for 65 min, so that the temperature of the inner wall of the reactor body 1 reaches 1000±1℃.

[0053] In this embodiment, the adding amount of the cobalt oxide and the battery-grade lithium carbonate is 1.050 in terms of Li / Me molar ratio.

[0054] During the mixing or mechanical heat generation, the temperature detection device 7 in the mixing and sintering system detects the temperature in the reactor body 1 and feeds back to the control device 5, and the control device 5 adjusts the length of the stirring rod 3 by the driving device 6 according to the temperature, so as to control the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1, and at the same time, adjusts the rotating speed of the stirring rod 3 by the driving device 6. The control of the distance and the rotating speed can realize the accurate control of the internal temperature of the reactor after the mechanical heat generation. In this embodiment, the free end of the stirring rod 3 is the friction roller 4.

[0055] In this embodiment, the material after the mixing and synthesis reaction is conveyed to the subsequent process through the pipeline, and the lithium ion positive electrode material lithium cobaltate is prepared, and the aspect ratio of the lithium cobaltate is 0.99, and the average particle size is 8.2 microns. The SEM electron microscope photo of the lithium cobaltate is shown in Figure 2

[0056] Embodiment 3

[0057] ​The difference between this embodiment and embodiment 2 is that the distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 in the sintering step is 0.08 cm, the second rotation speed is 4000 rpm, and the holding time of the second rotation speed is 1 h. The sintering step is used for the pre-sintering reaction of the positive electrode material. In this embodiment, the temperature of the pre-sintering reaction is 800 ℃. The pre-sintering reaction can prevent the local growth of particles, cause the problem of too large size difference, and also reduce the hardness of the material, facilitate the subsequent crushing process, and make the physical mixing of the raw materials reach the degree of chemical mixing, which is beneficial to the subsequent synthesis reaction. After the pre-sintering reaction in this embodiment is completed, it can be transferred to a traditional sintering furnace for high-temperature solid-phase sintering, or the rotation speed and / or distance can be adjusted to continue the synthesis reaction in the mixing and sintering system described in embodiment 1.

[0058] Embodiment 4

[0059] The difference between this embodiment and embodiment 2 is that the raw materials in the mixing step are the precursors of the ternary positive electrode material and battery-grade lithium carbonate, and the addition amount of the precursors of the ternary positive electrode material and battery-grade lithium carbonate is 1 in terms of Li / Me molar ratio. The distance between the free end of the stirring rod 3 and the inner wall of the reactor body 1 in the sintering step is 0.03 cm, the second rotation speed is 7500 rpm, and the sintering time is 90 min. The sintering step is used for the synthesis reaction of the multi-element positive electrode material. The temperature of the synthesis reaction is 1200 ℃. The aspect ratio of the obtained ternary positive electrode material is 1.02, and the average particle size is 11.2 microns.

[0060] Comparative Example 1

[0061] A preparation method of a lithium ion positive electrode material: cobalt oxide and battery-grade lithium carbonate are added into a high-speed mixer in a ratio of Li / Me=1.050 for mixing; the mixed material is put into a roller furnace for synthesis reaction, the sintering temperature is 1000 ℃, and the synthesis time is 18 h; after sintering is completed, the material is powdered through an air flow mill device; the crushed material is conveyed to the subsequent process through a pipeline to prepare lithium ion positive electrode material lithium cobaltate. The SEM electron microscope photo of the lithium cobaltate is as shown in Figure 3 .

[0062] From Figure 2 and Figure 3 It can be seen from the comparison that the positive electrode material particles prepared by the present application are round and uniform in size, while the positive electrode material particles prepared by the conventional high-temperature solid-phase method of comparative example 1 have large size difference and are not uniform.

[0063] The particle size D50, tap density TD, and half-cell capacity of the lithium cobaltate obtained in embodiment 2 and comparative example 1 are shown in Table 1.

[0064] Table 1 Comparison of physical and chemical properties of lithium cobaltate obtained in embodiment 2 and comparative example 1

[0065]

[0066] As can be seen from Table 1, the mechanical method for synthesizing the lithium ion positive electrode material in Example 2 is extremely close to the performance of the lithium ion positive electrode material prepared by the traditional method, and meets the production standard.

[0067] Please note that the technical features of the above examples can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A lithium-ion cathode material mixing and sintering system, comprising: The reactor body contains an internal stirring device; A drive device, located outside the reactor body and connected to the stirring device, is used to drive the stirring device; The stirring device is characterized in that it includes one or more stirring rods, the distance between the free end of the stirring rod and the inner wall of the reactor body is adjustable to form a first working state or a second working state. When the distance between the free end of the stirring rod and the inner wall of the reactor body is greater than 1 cm, the stirring rod can disperse and mix the material to form the first working state. When the distance between the free end of the stirring rod and the inner wall of the reactor body is in the range of 0.01-0.1cm, the free end of the stirring rod can generate heat through friction with the reactor body, forming the second working state; The free end of the stirring rod has a friction part; The friction part is a friction roller; It also includes temperature detection devices and control devices; The control device is also connected to the drive device and the stirring rod respectively. The control device can adjust the rotation speed of the drive device and the distance between the free end of the stirring rod and the inner wall of the reactor body according to the signal of the detection end of the temperature detection device located inside the reactor body, so as to achieve accurate control of the internal temperature of the reactor after mechanical heating.

2. The lithium ion cathode material mixing and sintering system according to claim 1, characterized in that, The reactor body has an axially arranged rotating shaft, and the opposite ends of the free ends of the stirring rod are connected to the rotating shaft; the axis of the friction roller is parallel to the axis of the rotating shaft.

3. The lithium ion cathode material mixing and sintering system according to claim 2, characterized in that, The length of the friction roller is 1 / 3 to 2 / 3 of the height of the reactor body; The ratio of the diameter d of the friction roller to the length L of the friction roller is between 1 / 3 and 1 / 2.

4. The lithium ion cathode material mixing and sintering system of claim 1, wherein, The temperature detection device includes a detection end and an output end. The detection end is located inside the reactor body, and the output end is connected to the control device via a signal connection.

5. The lithium-ion cathode material mixing and sintering system according to claim 4, characterized in that, The stirring rod includes an inner tube and an outer tube connected to each other by threads or snaps. The inner tube is signal-connected to the control device, which can control the inner tube to rotate or extend to adjust the length of the stirring rod.

6. A method for preparing powder using the lithium-ion cathode material mixing and sintering system according to any one of claims 1-5, characterized in that, Includes the following steps: Mixing: Add the raw materials into the reactor body, adjust the distance between the free end of the stirring rod and the inner wall of the reactor body to be greater than 1cm and less than or equal to 10cm, and complete the mixing at the first rotation speed; Sintering: Adjust the distance between the free end of the stirring rod and the inner wall of the reactor body to 0.01-0.1cm, and perform mechanical heating at the second rotation speed so that the temperature T inside the reactor body reaches the range of 700℃≤T≤1500℃, wherein the second rotation speed is greater than the first rotation speed.

7. The method according to claim 6, characterized in that, The raw materials include a precursor for the cathode material and a lithium source, wherein the molar ratio of the precursor (calculated as Me) to the lithium source (calculated as Li) satisfies n(Li):n(Me) = 0.95-1.30:1, and Me is a general term for the metal elements in the precursor.

8. The method according to claim 7, characterized in that, The cathode material is selected from one of the following: multi-element cathode materials, lithium cobalt oxide, lithium iron phosphate, or lithium manganese iron phosphate.

9. The method according to claim 7, characterized in that, The first rotational speed ranges from 300 to 600 rpm, and the mixing time is 1 to 90 minutes.

10. The method according to claim 7, characterized in that, The second rotational speed ranges from 3000 to 10000 rpm, and the sintering time is 0.5 to 10 hours.

11. The method according to claim 6, characterized in that, The sintering is used for the pre-sintering reaction of the cathode material, the second rotation speed ranges from 3500 to 4500 rpm, and the internal temperature T of the reactor body ranges from 700 to 850℃.

12. The method according to claim 6, characterized in that, The sintering is a synthesis reaction, the second rotation speed ranges from 5000 to 8000 rpm, the internal temperature T of the reactor body ranges from 1000 to 1200℃, and the sintering time is 30 to 90 minutes.

13. A positive electrode material, characterized in that, The lithium-ion cathode material is prepared by any one of the lithium-ion cathode material mixing and sintering systems according to any one of claims 1-5, or by any one of claims 6-12.

14. The cathode material according to claim 13, characterized in that, The aspect ratio of the positive electrode material is 0.98-1.

03.

15. The cathode material according to claim 13, characterized in that, The average particle size of the cathode material is 3-500 micrometers.

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