Coated doped lithium manganese iron phosphate gradient temperature control preparation equipment and method

Abstract

The invention relates to the technical field of lithium battery positive electrode material preparation, in particular to coated doped type lithium manganese iron phosphate gradient temperature control preparation equipment and method.The equipment comprises five temperature control bins arranged side by side, a sintering bin, a vertical flow guide plate, a unique temperature control gas inlet assembly and the like work cooperatively, the temperature control gas inlet assembly can flexibly adjust the gas state, and the temperature control gas inlet assembly can control the temperature of the lithium manganese iron phosphate; the preparation method comprises the following steps: firstly, mixing a lithium source, a manganese source and the like with a specific composite carbon source, and performing spray drying to obtain precursor particles; according to the preparation method, the defects of a traditional preparation technology in the aspects of temperature control and coating forming are overcome, accurate gradient temperature control can be achieved, the temperature uniformity can be improved, the coating effect can be optimized, and the preparation method is suitable for industrial production. And the performance of the lithium manganese iron phosphate positive electrode material is remarkably improved.

Description

Equipment and Method for Gradient Temperature Control of Coated Doped Lithium Manganese Iron Phosphate Technical Field

[0001] This invention relates to the field of lithium battery cathode material preparation technology, specifically to a gradient temperature controlled preparation device and method for coated and doped lithium manganese iron phosphate. Background Technology

[0002] With the rapid development of industries such as electric vehicles and portable electronic devices, the demand for high-performance batteries is increasing. Lithium-ion batteries, as the most widely used rechargeable batteries, rely heavily on the performance of their cathode materials, which directly determine the overall performance of the battery. Lithium manganese iron phosphate (LFP) has become one of the most promising cathode materials for lithium-ion batteries due to its high theoretical specific capacity, good thermal stability, environmental friendliness, and abundant resources. Currently, traditional lithium battery cathode material preparation equipment struggles to achieve precise gradient temperature control. The preparation of LFP requires several key temperature stages, including preheating and solvent removal at 300-400℃. This stage removes moisture and unstable compounds from the precursor, preparing it for subsequent processes. The crystallization reaction creates favorable conditions; however, traditional equipment experiences significant temperature fluctuations, making it impossible to precisely maintain this temperature range. This leads to insufficient or excessive desolvation, affecting subsequent crystallization. In the phase-forming crystallization stage at 600-680℃, extremely high temperature precision is required. Even minute temperature deviations can result in incomplete crystal structure, lattice defects, and consequently reduced electrochemical performance. Excessively high temperatures may cause crystal growth to be too rapid, forming coarse grains, reducing grain boundaries, and decreasing lithium-ion diffusion channels. Conversely, excessively low temperatures may lead to incomplete crystallization, preventing the material's specific capacity from reaching the theoretical value. Furthermore, the double-layer temperature difference-induced secondary diffusion stage at 680-800℃ requires precise temperature control. Precisely controlling the temperature difference between the upper and lower layers within 30-50℃ is challenging with traditional equipment. This makes it difficult to establish an ideal low-high-low concentration gradient of Mn / Fe elements along the radial direction, affecting the material's ion transport performance and structural stability. The slow cooling annealing stage at 400℃ is equally important, as it eliminates internal stress and stabilizes the crystal structure. However, traditional equipment struggles to precisely control the cooling rate; excessively fast or slow cooling can lead to stress concentration within the material, causing structural collapse during charging and discharging and reducing battery cycle life. Furthermore, existing equipment suffers from poor temperature uniformity during the sintering of lithium battery electrode materials due to its internal structural design. The unreasonable temperature control results in uneven heat transfer and varying degrees of heating in different parts of the material. Areas closer to the heating source have higher temperatures, while areas farther away have lower temperatures. This prevents the lithium manganese iron phosphate precursor particles from receiving uniform heat treatment during sintering, thus affecting the overall performance of the material. Particularly during particle coating, the uneven temperature can damage the integrity and uniformity of the carbon layer coating, reducing the material's electrochemical performance. In summary, existing lithium manganese iron phosphate preparation equipment has significant shortcomings in terms of the accuracy, uniformity, and flexibility of temperature control. Therefore, this invention discloses a gradient temperature control preparation device and method for coated and doped lithium manganese iron phosphate. Summary of the Invention

[0003] To address the issue raised in the background art regarding the uneven heat transfer and varying degrees of heating in different parts of the material during the sintering of lithium battery cathode materials due to unreasonable internal equipment design, the following solutions are proposed: areas closer to the heating source experience higher temperatures while areas farther away experience lower temperatures. This prevents the lithium manganese iron phosphate precursor particles from receiving uniform heat treatment during sintering, thus affecting the overall performance of the material. Particularly during particle coating, this uneven temperature distribution can compromise the integrity and uniformity of the carbon layer coating, reducing the material's electrochemical performance.

[0004] This invention provides a gradient temperature control equipment and method for coated and doped lithium manganese iron phosphate, comprising: a temperature control chamber, five temperature control chambers arranged side by side, wherein a first support plate and a second support plate are respectively installed on the temperature control chambers located at the first and last ends; a sintering chamber, wherein through holes are opened at the center of the heat insulation chamber walls at both ends of the temperature control chamber, the sintering chamber is arranged horizontally through the through holes, the sintering chamber and the through holes are coaxial, and the outer wall of the sintering chamber is clearance-fitted with the hole wall of the through holes; vertical guide plates, multiple vertical guide plates are arranged side by side vertically inside the temperature control chamber, the vertical guide plates are arranged side by side below the outer wall of the sintering chamber, and the bottom of the vertical guide plates extends from the center to both sides in a stepped manner; and a temperature control air intake assembly, wherein a load-bearing plate is fixed to the bottom of the temperature control chamber, and a temperature control air intake assembly is installed on the load-bearing plate, the temperature control air intake assembly is located below the vertical guide plates, and is used for temperature regulation inside the temperature control chamber.

[0005] As a further improvement to this technical solution, the temperature-controlled air intake assembly includes a transverse diversion guide plate, an air intake box, supporting ribs, a sealing plate, a lifting cylinder, a lifting rod, a tray, an extension arm, a lifting plate, a flow-limiting plate, and a linkage rod. The air intake box is installed at the bottom of the load-bearing plate, and an air intake hole is opened in the middle of the load-bearing plate. Multiple transverse diversion guide plates are vertically arranged at the air intake hole position. The height of the transverse diversion guide plates increases stepwise from the side to the middle. The top of each transverse diversion guide plate is provided with a bent part facing the side wall of the temperature-controlled chamber. The upper side of the air intake hole is fixed in parallel. There are multiple support ribs, which are located on both sides of the bottom of the vertical edge of the transverse diversion guide plate. An air passage is formed between two support ribs located on one side of the vertical wall of one of the transverse diversion guide plates. A push rod is vertically arranged between two support ribs. A sealing plate is fixed to the top of the push rod. The sealing plate is used to open and close the air passage. A tray is set inside the air intake box. The bottom end of the push rod is fixed to the top side of the tray. A push cylinder is installed at the bottom of the air intake box. The telescopic rod of the push cylinder passes through the bottom side wall of the air intake box. The top end of the telescopic rod of the push cylinder is fixed to the bottom side of the tray.

[0006] As a further improvement to this technical solution, a linkage rod is vertically fixed at the top center of the tray. The linkage rod is located between the two highest transverse diversion guide plates. A flow limiting plate is hinged to the opposing arc surfaces of the two highest transverse diversion guide plates. A push plate is fixed to the top of the linkage rod, and an extension arm is hinged between the push plate and the flow limiting plate.

[0007] As a further improvement to this technical solution, an air inlet is provided on one side of the air inlet box, and the air inlet is connected to an external air pump through a conduit, and an airflow valve is installed on the conduit; an exhaust port is provided on the top of the temperature control chamber, and the exhaust port is connected to an exhaust pipe, and a first guide pipe is connected to the exhaust pipe.

[0008] As a further improvement to this technical solution, two sets of roller frames are installed on the top side of the first support plate, and support rollers are rotatably installed on the roller frames. Both support rollers are set on the bottom side of one end of the sintering chamber, and the support rollers are used to support the rolling of one end of the sintering chamber.

[0009] A drive gear ring is mounted on one side of the outer wall of the sintering chamber. A drive motor is mounted on the top side of the first support plate. A drive gear is mounted on the output shaft of the drive motor. The drive gear meshes with the drive gear ring. A first sealing cover is mounted on the top side of the first support plate. One side of the first sealing cover seals one end port of the sintering chamber. A sliding sealing sleeve is provided between the outer wall of the end of the first sealing cover and the inner wall of one end of the sintering chamber. A feed pipe is mounted on the first sealing cover. A main control box is mounted on the first support plate.

[0010] As a further improvement to this technical solution, two sets of roller frames are synchronously installed on the second support plate. Support rollers are rotatably installed on the roller frames. Both support rollers are located on the bottom side of one end of the sintering chamber. The support rollers are used to support the other end of the sintering chamber. A second sealing cover is fixed on the second support plate. The port of the second sealing cover is connected to the other port of the sintering chamber. A discharge pipe is connected to the second sealing cover. The discharge pipe is connected to the other end cavity of the sintering chamber.

[0011] As a further improvement to this technical solution, a threaded auger is provided on the inner wall of the sintering chamber. The auger is used for the zoned conveying of materials. Heating wires are arranged in parallel inside the temperature control chamber. The heating wires are located on the outside of the sintering chamber. A temperature measuring probe is installed inside the temperature control chamber along the axial direction of the sintering chamber. The temperature measuring probe is used to detect the temperature of the sintering chamber.

[0012] A gradient temperature controlled preparation method for coated and doped lithium manganese iron phosphate includes the following steps: S1: Lithium source, manganese source, iron source, phosphorus source, and dopant are mixed with a composite carbon source, wherein the composite carbon source is composed of glucose, citric acid, and asphalt in a mass ratio of 6:3:1, with a total addition amount of 5-10 wt%. The mixture is then spray-dried to obtain multi-layer carbon source doped element gradient coated lithium manganese iron phosphate precursor particles; S2: The precursor particles are continuously fed into a rotary sintering equipment with five temperature-controlled chambers, sequentially performing the following steps: Zone 1 preheating and solvent removal at 300-400℃, Zone 2... Phase crystallization at 600-680℃, secondary diffusion of elements induced by temperature difference at 680-800℃ in three zones with an upper and lower temperature difference ΔT=30-50℃, slow cooling annealing at 680℃ to 400℃ in four zones, and graphitization at 400℃ in five zones. Each of the five temperature control chambers is equipped with an independent heating wire and a temperature control air intake component. The flow limiting plate is linked by a lifting cylinder to switch between laminar flow heating and high-speed cooling airflow modes in real time. S3: After discharge, the material is crushed and sieved to obtain lithium manganese iron phosphate cathode material with Mn / Fe exhibiting radial low, high, and low concentration gradients and carbon layer graphitization.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows: By setting up five temperature-controlled chambers and equipping them with independent heating wires and gas-electric coupling temperature control systems, it is possible to precisely achieve the temperature requirements of different stages, such as preheating and desolvation at 300-400℃, phase crystallization at 600-680℃, secondary diffusion of elements induced by the upper and lower double-layer temperature difference at 680-800℃, slow cooling annealing at 400℃, and graphitization at 400℃. Precise temperature control ensures that the lithium manganese iron phosphate precursor particles can undergo sufficient and appropriate reactions at each stage, which helps to form a well-formed crystal structure and elemental composition. The temperature-controlled air intake assembly works in conjunction with the vertical and horizontal flow dividers. When it is necessary to increase the temperature and uniformity, the temperature-controlled air intake assembly opens the air passage through structures such as the lifting cylinder and the lifting rod. The gas is guided by the horizontal flow divider to form laminar flow at different heights, and then guided vertically upward by the vertical flow divider. Combined with the heating wire, this makes the outer surface of the sintering chamber more evenly heated. When the temperature is reduced, the temperature-controlled air intake assembly retracts the lifting cylinder and adjusts the spacing of the flow restrictors to accelerate the exhaust airflow and form a high-speed airflow. This airflow carries away the heat from the bottom of the sintering chamber, ensuring the uniformity of the cooling process.

[0014] The temperature-controlled air intake assembly can flexibly adjust the temperature of the sintering chamber by controlling the gas flow rate and flow rate, and switching between laminar flow heating and high-speed cooling airflow modes. It can also flexibly adjust the temperature, gas flow rate and other parameters of each temperature-controlled chamber through the main control box according to the characteristics of different batches of lithium manganese iron phosphate precursor particles, so as to meet diverse production needs and enhance the versatility and adaptability of the equipment.

[0015] During the sintering process, precise temperature control and uniform heat distribution promote the formation of low, high, and low concentration gradients of Mn / Fe along the radial direction. At the same time, the carbon layer is fully graphitized and coated. This coating structure and element distribution can effectively improve the electrochemical performance of lithium manganese iron phosphate cathode material, improve the charge and discharge capacity, cycle stability, and rate performance of the battery, and enhance the conductivity of the material. A reasonable Mn / Fe concentration gradient helps to optimize the crystal structure of the material and improve the diffusion rate of lithium ions. Attached Figure Description

[0016] Figure 1 is a three-dimensional schematic diagram of the overall temperature control structure of the present invention; Figure 2 is a three-dimensional schematic diagram of the structure at both ends of the temperature control chamber of the present invention; Figure 3 is a three-dimensional schematic diagram of the sintering chamber flipping drive structure of the present invention; Figure 4 is a three-dimensional schematic diagram of the exterior of the temperature control chamber of the present invention; Figure 5 is a three-dimensional schematic diagram of the internal structure of the temperature control chamber of the present invention; Figure 6 is a cross-sectional structural diagram of the temperature control chamber of the present invention, indicating the gas flow direction in the heating state; Figure 7 is a cross-sectional structural diagram of the temperature control chamber of the present invention, indicating the gas flow direction in the cooling state; Figure 8 is a structural diagram of the temperature control air intake structure in the heating state of the present invention; Figure 9 is a structural diagram of the temperature control air intake structure in the cooling state of the present invention.

[0017] The labels in the diagram represent the following: 1. Temperature control chamber; 2. First support plate; 3. Drive motor; 4. First sealing cover; 5. Feed pipe; 6. Main control box; 7. Drive gear ring; 8. Sintering chamber; 9. Second sealing cover; 10. Discharge pipe; 11. Second support plate; 12. Support roller; 13. Roller frame; 14. Drive gear; 15. Temperature probe; 16. Heating wire; 17. Exhaust pipe; 18. First guide pipe; 19. Screwdriver; 21. Vertical guide plate; 22. Horizontal diversion guide plate; 23. Air inlet box; 24. Support rib; 25. Sealing plate; 26. Load-bearing plate; 27. Insulated chamber wall; 28. Lifting cylinder; 29. ​​Lifting rod; 30. Tray; 33. Extension arm; 34. Lifting plate; 35. Flow limiting plate; 36. Linkage rod. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the preparation of lithium-ion battery cathode materials, temperature control and related process steps have severely hindered the full realization of the performance of lithium-ion phosphate materials and their large-scale commercial application. From the perspective of temperature control, precise gradient temperature control is a key challenge in the preparation of lithium-ion phosphate. The synthesis of lithium-ion phosphate requires multiple specific temperature stages during the preparation of lithium-ion battery cathode materials. Therefore, this invention provides a gradient temperature control preparation device for coated and doped lithium-ion phosphate, as shown in Figures 1-9. It includes a temperature control chamber 1, with five temperature control chambers 1 arranged side-by-side. The temperature control chambers at both ends are respectively equipped with a first support plate 2 and a second support plate 11. A sintering chamber 8 is also provided. The heat-insulating chamber wall 27 has a through hole at its center. The sintering chamber 8 is arranged horizontally through the through hole. The sintering chamber 8 and the through hole are coaxial. The outer wall of the sintering chamber 8 is clearance-fitted with the wall of the through hole. Vertical guide plates 21 are arranged in parallel vertically inside the temperature control chamber 1. The vertical guide plates 21 are arranged in parallel below the outer wall of the sintering chamber 8. The bottom of the vertical guide plates 21 extends from the center to both sides in a stepped manner. Temperature control air intake assembly is fixed at the bottom of the temperature control chamber 1. A load-bearing plate 26 is fixed on the load-bearing plate 26. The temperature control air intake assembly is installed on the load-bearing plate 26. The temperature control air intake assembly is located below the vertical guide plates 21 and is used to regulate the temperature inside the temperature control chamber 1.

[0020] During the sintering process of lithium manganese iron phosphate precursor particles with multi-layer carbon source doping element gradient coating, the particles undergo a four-stage controllable gradient heat treatment: preheating and desolvation at 300-400℃, phase crystallization at 600-680℃, secondary element diffusion induced by a double-layer temperature difference at 680-800℃, and slow cooling annealing at 400℃. This process creates a low-high-low concentration gradient of Mn / Fe along the radial direction, while ensuring complete graphitization of the carbon layer. During the sintering process of the lithium manganese iron phosphate precursor particles, five temperature-controlled chambers 1 are set up. With the rotation of the sintering chamber 8, the particles are fed into different sections of the temperature-controlled chambers 1 within the sintering chamber 8. Each sintering chamber 8 is equipped with a heating environment of different temperatures. During the axial movement of the material along the sintering chamber 8, it passes through the temperature-controlled chamber 1 in different temperature control sections. With the cooperation of the temperature-controlled air intake component, the outer wall temperature of different sections of the sintering chamber 8 can be adjusted. In conjunction with the heating wire 16, heat is transferred to the sintering chamber 8 and the material in the furnace through heat conduction. At the same time, the convection of the gas can make the heat distribution in the furnace more uniform and accelerate the heat transfer speed, which helps to increase or decrease the furnace temperature. The rate of temperature change can also be adjusted by controlling the gas flow rate. The temperature is controlled by the heat transfer of the gas, thus optimizing the temperature control and sintering effect.

[0021] The temperature-controlled air intake assembly includes a transverse flow divider plate 22, an air intake box 23, supporting ribs 24, a sealing plate 25, a lifting cylinder 28, a lifting rod 29, a tray 30, an extension arm 33, a lifting plate 34, a flow-limiting plate 35, and a linkage rod 36. The air intake box 23 is installed at the bottom of the load-bearing plate 26. An air intake hole is opened in the middle of the load-bearing plate 26. Multiple transverse flow divider plates 22 are vertically arranged at the air intake hole. The height of the transverse flow divider plates 22 increases stepwise from the side to the middle. The top of each transverse flow divider plate 22 is provided with a bent part facing the side wall of the temperature-controlled chamber 1. Multiple supporting ribs 24 are fixed side by side on the upper side of the air intake hole. The supporting ribs 24 are located on both sides of the bottom of the vertical edge of the transverse diversion guide plate 22. An air passage is formed between two supporting ribs 24 located on one side of the vertical wall of one of the transverse diversion guide plates 22. A push rod 29 is vertically arranged between the two supporting ribs 24. A sealing plate 25 is fixed to the top of the push rod 29. The sealing plate 25 is used to open and close the air passage. A tray 30 is arranged inside the air intake box 23. The bottom end of the push rod 29 is fixed to the top side of the tray 30. A push cylinder 28 is installed at the bottom of the air intake box 23. The telescopic rod of the push cylinder 28 passes through the bottom side wall of the air intake box 23. The top end of the telescopic rod of the push cylinder 28 is fixed to the bottom side of the tray 30.

[0022] A linkage rod 36 is vertically fixed at the top center of the tray 30. The linkage rod 36 is located between the two highest transverse diversion guide plates 22. A flow limiting plate 35 is hinged to the opposing arc surfaces of the two highest transverse diversion guide plates 22. A push plate 34 is fixed at the top of the linkage rod 36. An extension arm 33 is hinged between the push plate 34 and the flow limiting plate 35.

[0023] The air intake process is divided into two stages: 1) When it is necessary to increase the temperature and uniformity of the sintering chamber 8, the push cylinder 28 extends to lift the tray 30 upwards. With the cooperation of the push rod 29, the sealing plate 25 is lifted, so that the air passage formed by the two adjacent support ribs 24 is connected vertically. The air rises from the air intake box 23 along the air passage, and under the guidance of the bend at the top of the transverse diversion guide plate 22, the gas diffuses to both sides. By utilizing the different heights of the bends of the transverse diversion guide plate 22, laminar flow at different heights can be formed. Among them, the linkage rod 36 is in the rising process This causes the pusher plate 34 to rise synchronously, and with the cooperation of the extension arm 33, pushes the flow-limiting plates 35 on both sides to a vertical position, making the space between the two highest transverse diversion guide plates 22 also a passage, in conjunction with auxiliary air intake; after laminar flow reaches the stepped vertical guide plate 21, the airflow can be guided vertically upward by the vertical guide plate 21. Under the combined guiding action of the transverse diversion guide plate 22 and the vertical guide plate 21, the airflow can be diverted and move upward in parallel vertical directions; with the cooperation of the airflow, the airflow is heated by the heating wire 16 and then acts on the sintering chamber. 8. This makes the outer surface of the sintering chamber 8 heat up more evenly, and with the help of airflow, it can effectively improve the heating effect of the sintering chamber 8; thereby improving the sintering effect of lithium manganese iron phosphate precursor particles; 2) When it is necessary to reduce the external temperature of the sintering chamber 8, the push cylinder 28 is used to retract, pulling the tray 30 downward. With the help of the push rod 29, the sealing plate 25 is pulled downward, sealing the air passage formed by two adjacent support ribs 24; wherein, during the process of the tray 30 falling, the linkage rod 36 is pulled downward, and with the linkage of the extension arm 33 When closed, the gap between the two flow-limiting plates 35 is reduced, and the top gap between the two flow-limiting plates 35 is reduced. The airflow is transported upward through the channel formed by the two highest transverse diversion guide plates 22. The exhaust area is reduced by the two flow-limiting plates 35, which can accelerate the exhaust airflow and form a high-speed airflow. The high-speed airflow acts on the bottom of the sintering chamber 8 in the vertical direction. Through the operation of the high-speed airflow, the temperature on the outer side of the bottom of the sintering chamber 8 can be lost, thereby achieving a cooling effect on the outer wall of the sintering chamber 8, avoiding over-sintering of the lithium manganese iron phosphate precursor particles, and better ensuring the temperature control effect of sintering.

[0024] An air inlet is provided on one side of the air inlet box 23, which is connected to an external air pump through a conduit. An airflow valve is installed on the conduit. An exhaust port is provided on the top of the temperature control chamber 1, which is connected to an exhaust pipe 17. A first guide pipe 18 is connected to the exhaust pipe 17. During operation, during the air intake process, the external air pump operates, and air is then introduced into the air inlet box 23 through the conduit. The air intake volume is adjusted by adjusting the flow rate of the airflow valve. After the gas operation, it moves upward along the outer circumference of the sintering chamber 8. The airflow flows out through the exhaust pipe 17 and is discharged through the first guide pipe 18, thereby achieving fine adjustment of the external temperature of the sintering chamber 8 and regulating the sintering temperature inside the chamber.

[0025] Two sets of roller frames 13 are installed on the top side of the first support plate 2. Support rollers 12 are rotatably installed on the roller frames 13. Both support rollers 12 are set on the bottom side of one end of the sintering chamber 8. The support rollers 12 are used to support the rolling of one end of the sintering chamber 8. During the sintering operation, the material moves along the axial direction of the sintering chamber 8. When passing through different temperature control chambers 1, the corresponding processing temperature is different. During the movement of the lithium manganese iron phosphate precursor particles, the lithium manganese iron phosphate precursor particles are sintered at different levels. During the installation operation of the sintering chamber 8, the two support rollers 12 support one end of the sintering chamber 8 to facilitate the rolling operation of the sintering chamber 8.

[0026] A drive gear ring 7 is mounted on the outer wall of one end of the sintering chamber 8. A drive motor 3 is mounted on the top side of the first support plate 2. A drive gear 14 is mounted on the output shaft of the drive motor 3. The drive gear 14 meshes with the drive gear ring 7. A first sealing cover 4 is mounted on the top side of the first support plate 2. One side of the first sealing cover 4 seals one end port of the sintering chamber 8. A sliding sealing sleeve is provided between the outer wall of the end of the first sealing cover 4 and the inner wall of one end of the sintering chamber 8. A feed pipe 5 is mounted on the first sealing cover 4. A main control box 6 is mounted on the first support plate 2. During operation, in order to better drive the rotation of the sintering chamber 8, the drive motor 3 drives the drive gear 14 to rotate. With the rotation of the drive gear ring 7, the sintering chamber 8 can be rolled. During feeding, the material is fed through the feed pipe 5. The lithium manganese iron phosphate precursor particles enter the sintering chamber 8. During the rotation of the sintering chamber 8, the sintering and conveying of the lithium manganese iron phosphate precursor particles is realized.

[0027] Two sets of roller frames 13 are synchronously installed on the second support plate 11. Support rollers 12 are rotatably installed on the roller frames 13. Both support rollers 12 are set on the bottom side of one end of the sintering chamber 8. The support rollers 12 are used to support the other end of the sintering chamber 8. A second sealing cover 9 is fixed on the second support plate 11. The port of the second sealing cover 9 is connected to the other port of the sintering chamber 8. A discharge pipe 10 is connected to the second sealing cover 9. The discharge pipe 10 is connected to the other end cavity of the sintering chamber 8. During operation, during the rotation of the sintering chamber 8, the other end of the sintering chamber 8 is also provided with support rollers 12 for supporting the rotation of the sintering chamber 8. With the cooperation of the support rollers 12 on the second support plate 11, the stable rotation of the sintering chamber 8 can be ensured. After the lithium manganese iron phosphate precursor particles are coated and sintered, they are discharged through the discharge pipe 10 on the second sealing cover 9 to realize the discharge.

[0028] The inner wall of the sintering chamber 8 is provided with a threaded auger 19, which is used for the zoned conveying of materials. Heating wires 16 are arranged side-by-side inside the temperature control chamber 1, located on the outer side of the sintering chamber 8. A temperature probe 15 is installed inside the temperature control chamber 1 along the axial direction of the sintering chamber 8 to detect the temperature of the sintering chamber 8. During operation, the rotation of the sintering chamber 8, in conjunction with the auger 19, ensures that the lithium manganese iron phosphate precursor particles move along the axial direction of the sintering chamber 8. During the radial movement along the sintering chamber 8, the lithium manganese iron phosphate precursor particles pass through different sections, achieving the coating and sintering of the lithium manganese iron phosphate precursor particles. During the sintering process, the sintering chamber 8 is heated by the heating wire 16, and heat conduction is achieved through the sintering chamber 8, thereby realizing the coating operation of the lithium manganese iron phosphate precursor particles. During the heating process, the temperature of the outer wall of the sintering chamber 8 is monitored in real time by the temperature probe 15. The monitored real-time temperature information is transmitted to the main control box 6, which provides real-time feedback, adjusts the power of the heating wire 16, and controls the air intake parameters in conjunction with the heating wire 16.

[0029] A gradient temperature controlled preparation method for coated and doped lithium manganese iron phosphate includes the following steps: S1: Mixing lithium source, manganese source, iron source, phosphorus source, and dopant with a composite carbon source, wherein the composite carbon source is composed of glucose, citric acid, and asphalt in a mass ratio of 6:3:1, with a total addition amount of 5-10 wt%, and spray drying to obtain multi-layer carbon source doped element gradient coated lithium manganese iron phosphate precursor particles; S2: Continuously feeding the precursor particles into a rotary sintering equipment with five temperature control chambers 1, wherein the temperature control chambers are: Zone 1 preheating and desolvation at 300-400℃, Zone 2 at 600℃, etc. -680℃ phase crystallization, three zones 680-800℃ with a temperature difference ΔT=30-50℃ for induced secondary diffusion of elements, four zones 680℃ to 400℃ slow cooling annealing, five zones 400℃ heat preservation graphitization, the five temperature control chambers 1 are all equipped with independent heating wires 16 and temperature control air intake components, and the two airflow modes of laminar flow heating and high-speed cooling are switched in real time by the push cylinder 28 and the flow limiting plate 35; S3: after discharge, the material is crushed and sieved to obtain lithium manganese iron phosphate cathode material with Mn / Fe in radial low, high, low concentration gradient and carbon layer graphitization.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A temperature-controlled equipment for coated and doped lithium manganese iron phosphate gradient temperature control, characterized in that: Includes a temperature control chamber (1), five temperature control chambers (1) arranged side by side, wherein the temperature control chambers (1) located at the first and last ends are respectively equipped with a first support plate (2) and a second support plate (11); a sintering chamber (8), wherein the heat insulation walls (27) at both ends of the temperature control chamber (1) are provided with through holes at the center, the sintering chamber (8) is arranged horizontally through the through holes, the sintering chamber (8) and the through holes are coaxial, and the outer wall of the sintering chamber (8) is fitted with the hole wall of the through hole with a clearance fit; a vertical guide plate (21), wherein... The temperature control chamber (1) has multiple vertical guide vanes (21) arranged in parallel inside. The vertical guide vanes (21) are arranged in parallel below the outer wall of the sintering chamber (8). The bottom of the vertical guide vanes (21) extends from the center to both sides in a stepped manner. Temperature control air intake component: The bottom of the temperature control chamber (1) is fixed with a load-bearing plate (26). The load-bearing plate (26) is equipped with a temperature control air intake component. The temperature control air intake component is located below the vertical guide vanes (21) and is used to regulate the temperature inside the temperature control chamber (1).

2. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 1, characterized in that: The temperature-controlled air intake assembly includes a transverse diversion guide plate (22), an air intake box (23), supporting ribs (24), a sealing plate (25), a lifting cylinder (28), a lifting rod (29), a tray (30), an extension arm (33), a lifting plate (34), a flow limiting plate (35), and a linkage rod (36). The air intake box (23) is installed at the bottom of the load-bearing plate (26). An air intake hole is opened in the middle of the load-bearing plate (26). Multiple transverse diversion guide plates (22) are vertically arranged at the air intake hole. The height of the transverse diversion guide plates (22) increases stepwise from the side to the middle. The top of each transverse diversion guide plate (22) is provided with a bent part facing the side wall of the temperature-controlled chamber (1). Multiple supporting ribs (24) are fixed side by side on the upper side of the air intake hole. The supporting ribs (24) are located on both sides of the bottom of the vertical side of the transverse diversion guide plate (22). An air passage is formed between two supporting ribs (24) located on one side of the vertical wall of one of the transverse diversion guide plates (22). A push rod (29) is vertically arranged between the two supporting ribs (24). A sealing plate (25) is fixed at the top of the push rod (29). The sealing plate (25) is used to open and close the air passage. A tray (30) is arranged inside the air inlet box (23). The bottom end of the push rod (29) is fixed to the top side of the tray (30). A push cylinder (28) is installed at the bottom of the air inlet box (23). The telescopic rod of the push cylinder (28) passes through the bottom side wall of the air inlet box (23). The top end of the telescopic rod of the push cylinder (28) is fixed to the bottom side of the tray (30).

3. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 2, characterized in that: A linkage rod (36) is vertically fixed at the top center of the tray (30). The linkage rod (36) is located between the two highest transverse diversion guide plates (22). A flow limiting plate (35) is hinged to the opposing arc surfaces of the two highest transverse diversion guide plates (22). A push plate (34) is fixed at the top of the linkage rod (36). An extension arm (33) is hinged between the push plate (34) and the flow limiting plate (35).

4. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 2, characterized in that: An air inlet is provided on one side of the air inlet box (23), and the air inlet is connected to an external air pump through a conduit. An air flow valve is installed on the conduit. An exhaust hole is provided on the top of the temperature control chamber (1), and the exhaust hole is connected to an exhaust pipe (17). A first guide pipe (18) is connected to the exhaust pipe (17). During operation, during the air intake process, the external air pump operates, and then air is introduced into the air inlet box (23) through the conduit. The air intake volume is adjusted by adjusting the flow rate of the air flow valve.

5. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 1, characterized in that: Two sets of roller frames (13) are installed on the top side of the first support plate (2). Support rollers (12) are rotatably installed on the roller frames (13). Both support rollers (12) are set on the bottom side of one end of the sintering chamber (8). The support rollers (12) are used to support the rolling of one end of the sintering chamber (8).

6. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 5, characterized in that: A drive gear ring (7) is mounted on one side of the outer wall of the sintering chamber (8). A drive motor (3) is mounted on the top side of the first support plate (2). A drive gear (14) is mounted on the output shaft of the drive motor (3). The drive gear (14) meshes with the drive gear ring (7). A first sealing cover (4) is mounted on the top side of the first support plate (2). One side of the first sealing cover (4) is sealed at one end of the sintering chamber (8). A sliding sealing sleeve is provided between the outer wall of the end of the first sealing cover (4) and the inner wall of one end of the sintering chamber (8). A feed pipe (5) is mounted on the first sealing cover (4). A main control box (6) is mounted on the first support plate (2).

7. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 1, characterized in that: Two sets of roller frames (13) are synchronously installed on the second support plate (11). Support rollers (12) are rotatably installed on the roller frames (13). Both support rollers (12) are set on the bottom side of one end of the sintering chamber (8). The support rollers (12) are used to support the other end of the sintering chamber (8). A second sealing cover (9) is fixed on the second support plate (11). The port of the second sealing cover (9) is connected to the other port of the sintering chamber (8). A discharge pipe (10) is connected to the second sealing cover (9). The discharge pipe (10) is connected to the other end cavity of the sintering chamber (8).

8. The coated and doped lithium manganese iron phosphate gradient temperature control equipment according to claim 7, characterized in that: The inner wall of the sintering chamber (8) is provided with a threaded auger (19), which is used for the partitioned conveying of materials. The temperature control chamber (1) is provided with heating wires (16) arranged in parallel inside, which are located on the outside of the sintering chamber (8). The temperature control chamber (1) is provided with a temperature probe (15) installed along the axial direction of the sintering chamber (8) inside, which is used to detect the temperature of the sintering chamber (8).

9. A gradient temperature controlled preparation method for coated doped lithium manganese iron phosphate, characterized in that, The coated and doped lithium manganese iron phosphate gradient temperature controlled preparation equipment according to claims 1-8 is applied to the coated and doped lithium manganese iron phosphate gradient temperature controlled preparation method, which includes the following steps: S1: mixing lithium source, manganese source, iron source, phosphorus source and dopant with composite carbon source, wherein the composite carbon source is composed of glucose, citric acid and asphalt in a mass ratio of 6:3:1, and the total addition amount is 5-10 wt%, and spray drying to obtain multi-layer carbon source doped element gradient coated lithium manganese iron phosphate precursor particles; S2: the precursor The particles are continuously fed into a rotary sintering equipment with five temperature-controlled chambers (1), in the following order: Zone 1: preheating and desolvation at 300-400℃; Zone 2: phase crystallization at 600-680℃; Zone 3: secondary diffusion of elements induced by temperature difference at 680-800℃ with an upper and lower temperature difference ΔT=30-50℃; Zone 4: slow cooling annealing at 680℃ to 400℃; Zone 5: heat preservation and graphitization at 400℃; S3: after discharge, the material is crushed and sieved to obtain lithium manganese iron phosphate cathode material with Mn / Fe in radial low, high, and low concentration gradients and carbon layer graphitization.

10. The method for preparing coated and doped lithium manganese iron phosphate with gradient temperature control according to claim 9, characterized in that, In S2, each of the five temperature control chambers (1) is equipped with an independent heating wire (16) and a temperature control air intake assembly. The two airflow modes of laminar flow heating and high-speed cooling are switched in real time by the push cylinder (28) and the flow limiting plate (35).

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