Preparation method of lithium iron manganese phosphate positive electrode material and lithium battery

Abstract

The present application belongs to the technical field of lithium batteries, and in particular, relates to a method for preparing a lithium iron manganese phosphate positive electrode material and a lithium battery, the method comprising: preparing the lithium iron manganese phosphate positive electrode material based on a high-temperature roasting tower, the high-temperature roasting tower comprising a high-temperature roasting furnace and a sintering furnace, the high-temperature roasting furnace comprising a sprayer, a heater and a particle size regulator, the method comprising: generating a first solution from an iron source, a phosphorus source and hydrochloric acid; generating a second solution from a manganese source and hydrochloric acid; passing a third solution mixed with the first solution, the second solution and a dispersant through a high-temperature roasting furnace to obtain at least two kinds of ferromanganese phosphate precursors with preset particle sizes; sintering the ferromanganese phosphate precursor and a first carbon source once in a first sintering zone to obtain a calcined body; and sintering the calcined body, a lithium source, a dopant and a second carbon source twice in a second sintering zone to obtain the lithium iron manganese phosphate positive electrode material, the particle size of the ferromanganese phosphate precursor can be controlled by adjusting the suspension time of droplets in the heating zone, and the cost is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium batteries, and in particular to a method for preparing a lithium iron manganese phosphate positive electrode material and a lithium battery. Background Art

[0002] At present, the particle size D50 of lithium iron manganese phosphate prepared based on high-temperature calcination tower is within a particle size range, but the lithium iron manganese phosphate positive electrode material within a particle size range cannot meet the needs of the scene, which is far from the 3.6g / cm 3 There is still a gap between the theoretical compaction density and the spray roasting process, the primary sintering process and the secondary sintering process are carried out by independent equipment, which increases the manufacturing cost.

[0003] The existing technology has the problem that the high-temperature roasting tower and preparation method of lithium manganese iron phosphate positive electrode material cannot meet the demand. Summary of the invention

[0004] The embodiments of the present application provide a method for preparing a lithium iron manganese phosphate positive electrode material and a lithium battery, which aim to solve the problem that a high-temperature roasting tower and a preparation method of the lithium iron manganese phosphate positive electrode material cannot meet the demand to a certain extent.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a lithium iron manganese phosphate positive electrode material, characterized in that the lithium iron manganese phosphate positive electrode material is prepared based on a high-temperature roasting tower, the high-temperature roasting tower includes a high-temperature roasting furnace and a sintering furnace connected to each other, the high-temperature roasting furnace includes a sprayer arranged at the top, at least 3 groups of heaters and at least 2 particle size regulators, the heaters are arranged at the upper and middle parts of the outer surface of the high-temperature roasting furnace, the particle size regulator is arranged inside the high-temperature roasting furnace corresponding to the position of the heater, the particle size regulator causes the sprayed droplets to move in reverse to adjust the suspension time of the atomized droplets to control the particle size of the ferromanganese phosphate precursor, and the sintering furnace includes a first sintering zone close to the high-temperature roasting furnace, a second sintering zone away from the high-temperature roasting furnace, and a movable baffle for separating the first sintering zone from the second sintering zone;

[0006] The preparation method comprises:

[0007] S11, mixing an iron source, a phosphorus source and hydrochloric acid to obtain a first solution;

[0008] S12, mixing a manganese source and hydrochloric acid to obtain a second solution;

[0009] S2, passing the first solution, the second solution and a third solution mixed with a dispersant through the high-temperature calcining furnace by a preset atomization method to spray-calculate and granulate to obtain at least two kinds of ferromanganese phosphate precursors with preset particle sizes;

[0010] S3, sintering the ferromanganese phosphate precursor and the first carbon source once in an inert gas atmosphere in the first sintering zone to obtain a lithium ferromanganese phosphate calcined body;

[0011] S4, performing secondary sintering on the lithium iron manganese phosphate calcined body, the lithium source, the dopant and the second carbon source in the inert gas atmosphere of the second sintering zone to obtain a lithium iron manganese phosphate positive electrode material.

[0012] The method for preparing lithium iron manganese phosphate positive electrode material based on a high-temperature roasting tower provided in the embodiment of the present application, since the high-temperature roasting furnace includes a sprayer arranged at the top, at least 3 groups of heaters and at least 2 particle size regulators, the heaters are arranged at the upper part and the middle part of the outer surface of the high-temperature roasting furnace, the particle size regulator is arranged inside the high-temperature roasting furnace corresponding to the position of the heater, and the particle size regulator causes the droplets after spraying to move in reverse to adjust the suspension time of the atomized droplets to control the particle size of the iron manganese phosphate precursor, and respectively form at least 2 kinds of powdered iron manganese phosphates with preset particle sizes Precursor, and when the large-particle precursor and the small-particle precursor are mixed, the small-particle precursor can better fill the gaps between the large-particle precursors, so the large-particle precursor and the small-particle precursor form a graded packing density filling, thereby forming a high-density lithium manganese iron phosphate positive electrode material; at the same time, the present application connects the sintering furnace and the high-temperature roasting furnace in sequence, avoiding the establishment of a separate sintering furnace, reducing the manufacturing cost of the sintering equipment, and the movable baffle between the first sintering zone and the second sintering zone further reduces the material transfer time and improves production efficiency.

[0013] In a second aspect, an embodiment of the present application provides a lithium battery, wherein the lithium battery includes a positive electrode plate, and the positive electrode plate is made of the lithium iron manganese phosphate positive electrode material as described in any one of the contents of the first aspect.

[0014] The lithium battery of the present application uses a positive electrode sheet made of the lithium iron manganese phosphate positive electrode material obtained by the above-mentioned high-temperature roasting furnace and preparation method. Since the conductivity and compaction density of the lithium iron manganese phosphate positive electrode material are improved, the lithium battery has a higher energy density and cycle performance, and the manufacturing cost of the lithium battery is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 is a schematic structural diagram of a high-temperature roasting device provided in one embodiment of the present application;

[0017] Figure 2 It is a schematic flow chart of a method for preparing a lithium iron manganese phosphate positive electrode material provided in one embodiment of the present application;

[0018] Figure 3 It is a top view schematic diagram showing that the jet holes of the spiral air pipe in the particle size regulator provided in one embodiment of the present application are distributed at intervals of preset angles;

[0019] Figure 4 This is a schematic structural diagram of staggered arrangement of jet holes in adjacent circles of a spiral air pipe provided by an embodiment of the present application;

[0020] Figure 5 This is a schematic diagram of a structure in which the jet holes of a spiral air pipe provided by an embodiment of the present application are distributed at preset angles and the diameters of the jet holes of each semicircle increase sequentially;

[0021] Figure 6 This is a schematic structural diagram of an embodiment of the present application in which the jet holes of adjacent circles of a spiral air pipe are staggered and the diameters of the jet holes of each semicircle increase sequentially;

[0022] Figure 7 This is a schematic diagram of a structure in which a nozzle is arranged in an air injection hole of a spiral air pipe provided in an embodiment of the present application;

[0023] Figure 8 It is a top view schematic diagram of a hollowed-out nozzle body provided by an embodiment of the present application;

[0024] Fig. 9 It is a schematic cross-sectional structure diagram of a nozzle in an air jet hole of a spiral air pipe provided by an embodiment of the present application when the nozzle does not perform air jetting;

[0025] Fig.10 It is a schematic cross-sectional structure diagram of a nozzle performing jetting in a jet hole of a spiral air pipe provided in an embodiment of the present application;

[0026] Reference numerals:

[0027] 1. First dissolving tank; 2. Second dissolving tank; 3. Mixing tank; 4. Venturi processor; 5. Pump; 6. Valve; 7. High-temperature roasting tower; 71. Sprayer; 72. Heater; 73. Particle size regulator; 731. Spiral air pipe; 732. Air intake flow regulator; 733. Jet hole; 734. Nozzle; 7341. Guide sleeve; 7342. Nozzle body; 7343. One-way jet block. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0030] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, a~b (i.e. a and b), a~c, b~c, or a~b~c, where a, b, c can be single or multiple, respectively.

[0031] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the implementation regulations of this application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0032] The terms used in the embodiments of the present application are only for the purpose of describing specific implementation rules, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the implementation rules of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0033] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0034] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0035] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0037] At present, the particle size D50 of lithium iron manganese phosphate prepared based on high-temperature calcination tower is within a particle size range, but the lithium iron manganese phosphate positive electrode material within a particle size range cannot meet the needs of the scene, which is far from the 3.6g / cm 3 There is still a gap between the theoretical compaction density and the spray roasting process, the primary sintering process and the secondary sintering process are carried out by independent equipment, which increases the manufacturing cost.

[0038] In order to overcome the above technical problems to a certain extent, Figure 1As shown, a lithium iron manganese phosphate positive electrode material is prepared based on a high-temperature calcination tower 7. The high-temperature calcination tower 7 includes a high-temperature calcination furnace and a sintering furnace connected to each other. The high-temperature calcination furnace includes a sprayer 71 arranged at the top, at least 3 groups of heaters 72 and at least 2 particle size regulators 73. The heaters 72 are arranged at the upper and middle parts of the outer surface of the high-temperature calcination furnace. The particle size regulator 73 is arranged inside the high-temperature calcination furnace corresponding to the position of the heater 72. The particle size regulator 73 allows the sprayed droplets to move in reverse to adjust the suspension time of the atomized droplets to control the particle size of the ferromanganese phosphate precursor. The sintering furnace includes a first sintering zone 74 close to the high-temperature calcination furnace, a second sintering zone 75 away from the high-temperature calcination furnace, and a movable baffle 76 for separating the first sintering zone 74 from the second sintering zone 75. The present application also prepares lithium iron manganese phosphate positive electrode material based on a high-temperature roasting device including a high-temperature roasting tower 7, and the high-temperature roasting device includes a first dissolution tank 1, a second dissolution tank 2, a mixing tank 3, a venturi processor 4, a pump 5, a valve 6, a vertical high-temperature roasting tower 7, a first material conveying tank 8 and a second material conveying tank 9; wherein, the outlet of the first dissolution tank 1 and the outlet of the second dissolution tank 2 are connected to the first inlet of the mixing tank 3, the outlet at the bottom of the mixing tank 3 is connected to the first inlet of the side wall of the venturi processor 4, the outlet at the bottom of the venturi processor 4 is connected to the inlet of the pump 5, the outlet of the pump 5 is respectively connected to the inlet at the top of the high-temperature roasting tower 7 and the second inlet of the side wall of the venturi processor 4, the first outlet near the top of the high-temperature roasting furnace 7 is connected to the third inlet at the top of the venturi processor 4, the first material conveying tank 8 conveys the material to the first sintering zone 74, the second material conveying tank 9 conveys the material to the second sintering furnace 75, and the first sintering zone 74 and the second sintering zone 75 are both provided with at least one group of heaters 72.

[0039] like Figure 2 As shown, the first aspect of the embodiment of the present application provides a method for preparing a lithium manganese iron phosphate positive electrode material, comprising:

[0040] S11, mixing an iron source, a phosphorus source and hydrochloric acid to obtain a first solution.

[0041] S12, mixing a manganese source and hydrochloric acid to obtain a second solution.

[0042] S2, passing the first solution, the second solution and the third solution mixed with the dispersant through a high temperature calcining furnace by a preset atomization method for spray calcining and granulation to obtain at least two kinds of ferromanganese phosphate precursors with preset particle sizes.

[0043] S3, sintering the ferromanganese phosphate precursor and the first carbon source once in an inert gas atmosphere in the first sintering zone 74 to obtain a lithium ferromanganese phosphate calcined body.

[0044] S4, the lithium iron manganese phosphate calcined body, the lithium source, the dopant and the second carbon source are subjected to secondary sintering in the inert gas atmosphere of the second sintering zone 75 to obtain a lithium iron manganese phosphate positive electrode material.

[0045] The method for preparing lithium iron manganese phosphate positive electrode material based on a high-temperature roasting device provided in an embodiment of the present application, since the high-temperature roasting furnace includes a sprayer arranged at the top, at least 3 groups of heaters and at least 2 particle size regulators, the sprayer at the top sprays droplets of atomized mixed solution downward, the heater is arranged at the upper and middle parts of the outer surface of the high-temperature roasting furnace, and the particle size regulator is arranged inside the high-temperature roasting furnace corresponding to the position of the heater, and the particle size regulator causes the sprayed droplets to move in the opposite direction relative to the landing direction of the sprayed droplets, that is, the particle size regulator causes the sprayed droplets to move in the opposite direction toward the top of the high-temperature roasting furnace, thereby causing the droplets to interact with the spray atomization and reverse movement downward from the top, on the one hand, promoting the droplets to generate particles with more uniform particle size, more spherical shape and more thorough particle formation, and on the other hand, by controlling the time for the droplets to perform reverse movement to adjust the suspension time of the atomized droplets to control the particle size of the ferromanganese phosphate precursor, since the particle size regulator is located inside the high-temperature roasting furnace corresponding to the position of the heater, the sprayer The atomized droplets move in the reverse direction in the heating area so that the heating and reverse movement can cooperate with each other. The longer the suspension time caused by the reverse movement, the longer the heating time, resulting in a greater reduction in the liquid component of the droplets and a smaller particle size of the generated particles. The shorter the suspension time caused by the reverse movement, the shorter the heating time, resulting in a smaller reduction in the liquid component of the droplets and a larger particle size of the generated particles, thereby forming at least two kinds of powdered manganese iron phosphate precursors with preset particle sizes. When the large-particle-size precursor and the small-particle-size precursor are mixed, the small-particle-size precursor can better fill the gaps between the large-particle-size precursors, so the large-particle-size precursor and the small-particle-size precursor form a graded packing density filling, thereby forming a high-density manganese iron phosphate lithium positive electrode material. At the same time, the present application connects the first sintering zone, the second sintering zone and the high-temperature roasting furnace in sequence, avoiding the establishment of a separate sintering furnace and reducing the manufacturing cost of the sintering equipment. The movable baffle between the first sintering zone and the second sintering zone further reduces the material transfer time and improves production efficiency.

[0046] In some embodiments, Figure 3As shown, any particle size regulator 73 includes a spiral air pipe 731 and an air intake flow regulator 732 (not shown in the figure), and the spiral air pipe 731 is provided with a plurality of jet holes 733 on one side close to the sprayer 71, and the gas in the spiral air pipe 731 is a carrier gas; step S2 includes: mixing the third solution with the carrier gas and setting the flow rate of the gas-liquid mixture through the sprayer 71 to a preset flow rate, and then adjusting the nozzle of the sprayer 71 to a preset aperture to spray in a preset atomization mode; the droplets of the atomized third solution are sequentially evaporated, dried and calcined in a top-down direction, and the air intake flow rate and / or air intake time of the carrier gas in the spiral air pipe 731 are adjusted by the air intake flow regulator 732 to form at least two kinds of powdered manganese ferrophosphate precursors with preset particle sizes. In this embodiment, the plurality of jet holes 733 arranged on one side of the spiral air pipe 731 near the sprayer 71 will spray the carrier gas according to the pressure of the air inlet flow regulator 732, causing the droplets to move upward in the reverse direction under the action of the reverse jet, thereby adjusting the suspension time of the droplets sprayed downward in the evaporation process, drying process and roasting process, and then adjusting the particle size of the ferromanganese phosphate precursor, thereby increasing the compaction density of the lithium iron manganese phosphate. It can be understood that the shorter the suspension time of the atomized droplets sprayed by the sprayer 71 in the evaporation process, drying process and roasting process, the less the solvent evaporation and pyrolysis of the atomized droplets, which reduces the drying and curing effect of the atomized droplets, so that the particle size of the ferromanganese phosphate precursor will be relatively large; and the longer the suspension time of the atomized droplets sprayed by the sprayer 71 in the evaporation process, drying process and roasting process, the more the solvent evaporation and pyrolysis of the atomized droplets are, which promotes the drying and curing of the atomized droplets, so that the particle size of the ferromanganese phosphate precursor will be relatively small.

[0047] In some embodiments, compared with the prior art that sprays in only one direction, causing the droplets to be affected by gravity during the descent process, the particles of the ferromanganese phosphate precursor cannot form a shape close to a sphere, and the range of controlling the suspension time of the droplets is relatively small; the spiral air pipe 731 is provided with a plurality of jet holes 733 on one side close to the sprayer 71, and the jet holes of the spiral air pipe 731 are distributed at preset angles in a clockwise or counterclockwise direction, such as Figure 3 As shown, or the jet holes of adjacent circles of the spiral air pipe 731 are staggered, as shown in FIG. Figure 4 As shown; thereby, the jet of the spiral air pipe 731 forms a uniformly covered reverse power in the heating zone of the high-temperature roasting furnace 7, so that more spray droplets can perform uniform reverse suspension movement in the heating zone, thereby forming particles of ferromanganese phosphate precursor with more uniform particle size and a shape closer to a sphere, and can control the suspension time in a larger range, thereby forming particles of ferromanganese phosphate precursor within a preset particle size range.

[0048] In one embodiment, since the diameters of the jet holes 733 are the same, the distribution of the jet holes 733 is relatively sparse as the spiral air pipe 731 moves outward, causing the reverse force on the droplets in the local area to be not uniform. Figure 5 As shown, the particle size regulator 73 includes a spiral air pipe 731 and an air intake flow regulator 732. The spiral air pipe 731 is provided with a plurality of jet holes 733 on one side close to the sprayer 71. The diameters of the jet holes in each semicircle of the spiral air pipe 731 increase successively along the spiral air pipe 731 from the inside to the outside. Since the diameter is smaller in the dense area of ​​the inner circle and then increases successively, the jet holes in the outer circle have a larger range of jet influence due to the larger diameter, thereby compensating for the disadvantage that the reverse force received by the droplets in the local area is not uniform enough, so that a uniformly covered reverse force is formed in the heating zone of the high-temperature roasting furnace 7, so that more spray droplets can perform uniform reverse suspension movement in the heating zone, thereby forming particles of ferromanganese phosphate precursor with more uniform particle size and shape closer to a sphere, and being able to control a larger range of suspension time, thereby forming particles of ferromanganese phosphate precursor with a preset particle size range.

[0049] In some embodiments, a plurality of jet holes 733 are provided on one side of the spiral air tube 731 close to the sprayer 71. The jet holes of the spiral air tube 731 are distributed at preset angles in a clockwise or counterclockwise direction and extend from the inside to the outside along the spiral air tube 731. The diameters of the jet holes in each semicircle of the spiral air tube 731 increase successively. Figure 5 Alternatively, the jet holes of adjacent circles of the spiral air pipe 731 are staggered and extend from the inside to the outside along the spiral air pipe 731, as shown in FIG. Figure 6 As shown, the diameter of the jet hole in each semicircular spiral air pipe 731 increases successively; it can further form a more uniformly covered reverse power in the heating zone of the high-temperature roasting furnace 7, so that more spray droplets can perform uniform reverse suspension movement in the heating zone, thereby forming particles of ferromanganese phosphate precursor with more uniform particle size and closer to spherical shape, and can control a larger range of suspension time, thereby forming particles of ferromanganese phosphate precursor within a preset particle size range.

[0050] In one embodiment, since it is necessary to adjust the suspension time of the droplets after spraying, when the jet hole is not jetting outward, some particles of the ferromanganese phosphate precursor will fall into it, causing partial blockage of the jet hole, or the gas ejected from the jet hole can only generate the corresponding reverse power in the area near the jet hole diameter, reducing the reverse power range generated by the jet hole jetting outward; Figure 7As shown, in any of the jet holes 733, a nozzle 734 is provided, and the nozzle 734 includes a guide sleeve 7341, a nozzle body 7342 and a one-way jet block 7343. The nozzle body 7342 is in the shape of an inverted truncated cone with an opening at the bottom, and its diameter gradually increases along the direction from the spiral air pipe 731 to the sprayer 71. The guide sleeve 7341 is an elastic set provided on the outside of the nozzle body 7342. The diameter of the bottom of the nozzle body 7342 away from the sprayer 71 is smaller than the diameter of the corresponding jet hole 733, and the diameter of the top of the nozzle body 7342 close to the sprayer 71 is larger than the diameter of the corresponding jet hole 733. The top of the nozzle body 7342 is a hollow surface, as shown in FIG. Figure 8 As shown; the one-way jet block 7343 is an inverted truncated cone corresponding to the nozzle body 7342, the ratio between the height of the nozzle body 7342 and the height of the one-way jet block 7343 is (3-1.2):1, the height of the nozzle body 7342 is smaller than the diameter of the spiral air pipe 731 and larger than the thickness of the spiral air pipe 731; the guide sleeve 7341 is used to fix the nozzle 734 in the jet hole 733 by interference fit, and prevent the carrier gas from being ejected from the gap between the guide sleeve 7341 and the jet hole 733; as shown Fig. 9 As shown, when the spiral air pipe 731 is not jetting, the one-way jet block 7343 slides into the bottom along the inverted truncated cone of the nozzle body 7342 under the action of gravity, thereby blocking the jet hole 733, thereby avoiding the blockage of the jet hole; as shown in FIG. Fig.10 As shown, when the spiral air pipe 731 is jetting through the jet hole 733, the carrier gas enters from the opening at the bottom of the nozzle body 7342 to blow the one-way jet block 7343 toward the top of the nozzle body 7342, and is ejected through the gap between the one-way jet block 7343 and the nozzle body 7342, providing a reverse power in the opposite direction of the droplet falling direction, and expanding the reverse power range of the jet through the inverted truncated cone shape. It can be understood that along the spiral air pipe 731 extending from the inside to the outside, the diameter of the top of the nozzle body 7342 close to the sprayer 71 can also be gradually increased, so as to form a more uniform reverse power coverage area.

[0051] In some embodiments, the evaporation zone corresponding to the evaporation treatment, the drying zone corresponding to the drying treatment, and the roasting zone corresponding to the roasting treatment are all provided with at least one group of heaters 72 and at least one particle size regulator 73, and the heaters 72 are respectively arranged on the outer surfaces of the high-temperature roasting tower 7 corresponding to the evaporation zone, the drying zone, and the roasting zone, and the evaporation zone, the drying zone, and the roasting zone are respectively provided with at least one particle size regulator 73; or, the evaporation zone corresponding to the evaporation treatment, the drying zone corresponding to the drying treatment, and the roasting zone corresponding to the roasting treatment are all provided with at least one group of heaters 72, and at least two of the evaporation zone, the drying zone, or the roasting zone are each provided with a particle size regulator 73, the heaters 72 are respectively arranged on the outer surfaces of the high-temperature roasting tower 7 corresponding to the evaporation zone, the drying zone, and the roasting zone, and the evaporation zone and the drying zone are respectively provided with at least one particle size regulator 73, or the drying zone and the roasting zone are respectively provided with at least one particle size regulator 73, or the evaporation zone and the roasting zone are respectively provided with at least one particle size regulator 73. The heater 72 is a microwave heater, a gas heater, or a microwave heater and a gas heater; thus, the suspension time of the atomized droplets can be controlled in the evaporation zone, the drying zone and the roasting zone, respectively, further improving the ability to control the suspension time of the atomized droplets in the high-temperature roasting tower 7, and the atomized droplets can be completely processed in each zone to form various required particle sizes of ferromanganese phosphate precursors. For example, the evaporation zone is a microwave heater, the drying zone is a microwave heater, and the roasting zone is a gas heater; or the evaporation zone, the drying zone and the roasting zone are all microwave heaters; or the evaporation zone, the drying zone and the roasting zone are all gas heaters. In addition, the first sintering zone and the second sintering zone are respectively provided with at least one group of heaters, and the heaters of the first sintering zone and the second sintering zone are all gas heaters, which is convenient for reducing energy consumption costs.

[0052] In some embodiments, the movable baffle 76 includes two movable plates arranged along the circumference of the high-temperature roasting tower 7 and two movable supporting parts connecting the movable plates and the inner wall of the high-temperature roasting tower 7. One movable plate corresponds to one movable supporting part. The two movable plates can be opened toward the bottom of the high-temperature roasting tower 7 when the corresponding movable supporting parts are contracted, so as to facilitate the lithium manganese iron phosphate calcined body in the first sintering zone 74 to enter the second sintering zone 75. The two movable plates move toward the top of the high-temperature roasting tower 7 when the corresponding movable supporting parts are extended until the two movable plates are closed to receive the ferromanganese phosphate precursor of the high-temperature roasting furnace.

[0053] In other embodiments, the movable baffle 76 includes a first movable plate and a second movable plate that are meshed with each other, the first movable plate is provided with a plurality of holes, the second movable plate is correspondingly provided with protrusions corresponding to the holes of the first movable plate, the holes of the first movable plate are meshed with the corresponding protrusions, the movable baffle 76 also includes a power device arranged on the inner wall of the high-temperature roasting tower 7, the power device enables the first movable plate and the second movable plate to mesh with each other, the movable plate to receive the ferromanganese phosphate precursor of the high-temperature roasting furnace, and at the same time the lithium ferromanganese phosphate calcined body cannot enter the second sintering zone, the power device enables the first movable plate and the second movable plate to be staggered with each other, and the lithium ferromanganese phosphate calcined body enters the second sintering zone.

[0054] In other embodiments, the movable baffle used to separate the first sintering zone from the second sintering zone is a first movable baffle, and the sintering furnace also includes a second movable baffle used to separate the second sintering zone from the bottom of the high-temperature roasting tower 7, and the second movable baffle is used to reduce the sintering space of the second sintering zone and reduce the energy consumption of secondary sintering.

[0055] In some embodiments, the gas and carrier gas generated by the evaporation treatment, drying treatment and roasting treatment enter the third inlet of the venturi processor 4 through the first outlet near the top of the high-temperature roasting tower 7, and the mixed solution is preheated and concentrated by self-circulation of the venturi processor 4 and the pump 5, and the preheating and concentration is to evaporate 30wt% of the water in the mixed solution. In this embodiment, the first solution, the second solution and the dispersant are uniformly mixed in the mixing tank 3 to obtain a mixed solution, which is sent to the venturi processor 4 for preheating and concentration, which can reduce the viscosity of the mixed solution, reduce the blockage of the sprayer, and concentrate 30wt% of the water in the mixed solution, which can reduce the heating energy consumption of the high-temperature roasting tower 7, thereby reducing the cost of preparing lithium manganese iron phosphate.

[0056] In some embodiments, the preset particle size includes a first preset particle size and a second preset particle size, and the first preset particle size is larger than the second preset particle size. In this embodiment, after the ferromanganese phosphate precursor of the larger first preset particle size is mixed with the ferromanganese phosphate precursor of the smaller second preset particle size, the ferromanganese phosphate precursor of the smaller particle size can be filled into the gap between the ferromanganese phosphate precursors of the larger particle size, thereby increasing the compaction density of the ferromanganese phosphate lithium positive electrode material.

[0057] In some embodiments, the intake flow rate of the carrier gas in the spiral air pipe includes a first intake flow rate and a second intake flow rate, and the first intake flow rate is smaller than the second intake flow rate; the intake flow rate and / or intake time of the carrier gas in the spiral air pipe are adjusted by an intake flow regulator to form at least two powdered ferromanganese phosphate precursors with preset particle sizes, including: the intake flow regulator adjusts the intake flow rate of the carrier gas in the spiral air pipe to the first intake flow rate to form a powdered ferromanganese phosphate precursor with a first preset particle size; the intake flow regulator adjusts the intake flow rate of the carrier gas in the spiral air pipe to the second intake flow rate to form a powdered ferromanganese phosphate precursor with a second preset particle size. In this embodiment, according to the particle size requirement of the ferromanganese phosphate precursor, the carrier gas in the spiral air pipe is adjusted to a smaller first air intake flow rate, which has less hindrance to the descent of the atomized droplets sprayed from the sprayer, and the suspension time of the atomized droplets in the evaporation treatment, drying treatment and roasting treatment is shorter, so that the solvent evaporation and pyrolysis of the atomized droplets are less, which reduces the drying and solidification effects of the atomized droplets, and thus the particle size of the ferromanganese phosphate precursor will be relatively large; while adjusting the carrier gas in the spiral air pipe to a larger second air intake flow rate, there is greater hindrance to the descent of the atomized droplets sprayed from the sprayer, and the suspension time of the atomized droplets in the evaporation treatment, drying treatment and roasting treatment is longer, so that the solvent evaporation and pyrolysis of the atomized droplets are more, which promotes the drying and solidification of the atomized droplets, and thus the particle size of the ferromanganese phosphate precursor will be relatively small.

[0058] In some embodiments, the intake flow rate of the carrier gas in the spiral air pipe is a preset intake flow rate, and the intake time of the carrier gas in the spiral air pipe includes a first intake time and a second intake time, and the first intake time is less than the second intake time; the intake flow rate and / or intake time of the carrier gas in the spiral air pipe are adjusted by an intake flow regulator to form at least 2 powdered ferromanganese phosphate precursors with preset particle sizes, including: the intake flow rate regulator adjusts the intake flow rate of the carrier gas in the spiral air pipe to the preset intake flow rate and maintains the first intake time to form a powdered ferromanganese phosphate precursor with a first preset particle size; the intake flow rate regulator adjusts the intake flow rate of the carrier gas in the spiral air pipe to the preset intake flow rate and maintains the second intake time to form a powdered ferromanganese phosphate precursor with a second preset particle size. In the present embodiment, according to the particle size requirement of the ferromanganese phosphate precursor, when the carrier gas is set to a preset air intake flow rate, the carrier gas in the spiral air pipe is adjusted to a shorter first air intake time, which lessens the descent of the atomized droplets sprayed from the sprayer, and the suspension time of the atomized droplets during the evaporation, drying and roasting treatments is shorter, thereby less solvent evaporation and pyrolysis of the atomized droplets, which reduces the drying and solidification effects of the atomized droplets, and thus the particle size of the ferromanganese phosphate precursor will be relatively large; and when the carrier gas in the spiral air pipe is adjusted to a longer second air intake time, greater descent of the atomized droplets sprayed from the sprayer is resistant to the descent, and the suspension time of the atomized droplets during the evaporation, drying and roasting treatments is longer, thereby more solvent evaporation and pyrolysis of the atomized droplets are more, which promotes the drying and solidification of the atomized droplets, and thus the particle size of the ferromanganese phosphate precursor will be relatively small.

[0059] In some embodiments, the inlet gas flow rate of the carrier gas in the spiral trachea includes a first inlet gas flow rate and a second inlet gas flow rate, the first inlet gas flow rate is less than the second inlet gas flow rate, the inlet gas time of the carrier gas in the spiral trachea includes a first inlet gas time and a second inlet gas time, and the first inlet gas time is less than the second inlet gas time; adjusting the inlet gas flow rate and / or inlet gas time of the carrier gas in the spiral trachea by an inlet gas flow rate regulator to form powdery manganese iron phosphate precursors with at least two preset particle sizes, including: the inlet gas flow rate regulator adjusts the inlet gas flow rate of the carrier gas in the spiral trachea to the first inlet gas flow rate and maintains the first inlet gas time to form a powdery manganese iron phosphate precursor with a first preset particle size; the inlet gas flow rate regulator adjusts the inlet gas flow rate of the carrier gas in the spiral trachea to the second inlet gas flow rate and maintains the second inlet gas time to form a powdery manganese iron phosphate precursor with a second preset particle size. In this embodiment, according to the particle size requirement of the manganese iron phosphate precursor, the carrier gas in the spiral trachea is adjusted to a smaller first inlet gas flow rate and maintained for a shorter first inlet gas time, further reducing the hindrance to the descent of the atomized droplets ejected by the atomizer. The suspension time of the atomized droplets during evaporation treatment, drying treatment and calcination treatment will be shorter, so the solvent evaporation and pyrolysis of the atomized droplets will be further reduced, reducing the drying and solidification effects of the atomized droplets, resulting in a larger particle size of the manganese iron phosphate precursor; while adjusting the carrier gas in the spiral trachea to a larger second inlet gas flow rate and maintaining a longer second inlet gas time, further increases the hindrance to the descent of the atomized droplets ejected by the atomizer. The suspension time of the atomized droplets during evaporation treatment, drying treatment and calcination treatment will be longer, so the solvent evaporation and pyrolysis of the atomized droplets will be further increased, promoting the drying and solidification of the atomized droplets, resulting in a smaller particle size of the manganese iron phosphate precursor.

[0060] In some embodiments, the first preset particle size is 400 nm < D501 ≤ 800 nm; and / or, the second preset particle size is 20 nm ≤ D502 ≤ 200 nm; the first inlet gas flow rate is 5 Nm 3 / h ≤ Q1 ≤ 30 Nm 3 / h, and the second inlet gas flow rate is 40 Nm 3 / h ≤ Q2 ≤ 120 Nm 3 / h. In this embodiment, a smaller first inlet gas flow rate corresponds to a larger first preset particle size, and a larger second inlet gas flow rate corresponds to a smaller second preset particle size; or, a shorter first inlet gas time corresponds to a larger first preset particle size, and a longer second inlet gas time corresponds to a smaller second preset particle size; or, a smaller first inlet gas flow rate and maintaining a shorter first inlet gas time correspond to a larger first preset particle size, and a larger second inlet gas flow rate and maintaining a longer second inlet gas time correspond to a smaller second preset particle size, so as to control the particle size of the manganese iron phosphate precursor by adjusting the inlet gas flow rate and / or inlet gas time of the spiral trachea.

[0061] In some other embodiments, the preset particle size further includes a third preset particle size, the third preset particle size is greater than the second preset particle size and less than the first preset particle size, the intake air flow rate of the carrier gas in the spiral gas pipe further includes a third intake air flow rate, the third intake air flow rate is less than the second intake air flow rate and greater than the first intake air flow rate, the third preset particle size is 300 nm < D503 ≤ 600 nm, and the third intake air flow rate is 30 Nm 3 / h < Q3 < 10 Nm 3 / h. In this embodiment, the third preset particle size is between the second preset particle size and the first preset particle size, the third intake air flow rate is between the first intake air flow rate and the second intake air flow rate, and the third intake air flow rate correspondingly forms the third preset particle size between the larger particles and the smaller particles, so as to realize controlling multiple particle sizes of the iron manganese phosphate precursor by adjusting the intake air flow rate of the spiral gas pipe.

[0062] In some embodiments, the temperature of the calcination treatment is 500 °C to 1000 °C; and / or, the time of the evaporation treatment, the drying treatment and the calcination treatment is 2 min to 5 min. Among them, the temperature of the evaporation treatment is 100 - 200 °C, and the temperature of the drying treatment is 300 - 450 °C. In this embodiment, the evaporation treatment is to evaporate the solvent of the atomized droplets, thereby reducing the particle size of the atomized droplets, and at the same time facilitating the acceleration of the pyrolysis rate after removing the solvent; the drying treatment is to remove the solvent and moisture in the droplets after evaporation, further reducing the particle size of the atomized droplets, and at the same time facilitating the acceleration of the pyrolysis rate after removing the solvent; the calcination treatment is to heat the atomized droplets of the manganese solution, the phosphorus-iron solution and the dispersant to carry out a pyrolysis reaction to release reaction gases and retain solid spherical substances, forming a powdery iron manganese phosphate precursor.

[0063] In some embodiments, the parameters of the first sintering: the sintering temperature is 600 °C to 850 °C, and the constant temperature time during sintering is 0.5 h to 3 h; and / or, the parameters of the second sintering: the sintering temperature is 650 °C to 850 °C, and the constant temperature time during sintering is 6 h to 14 h. Using the first sintering parameters and the second sintering parameters in this embodiment for sintering can effectively carry out the reduction reaction, the first carbon coating and the second carbon coating, thereby improving the carbon coating integrity of the lithium iron phosphate cathode material, and further improving the electrochemical performance of the lithium iron phosphate cathode material.

[0064] In some embodiments, the mass ratio of the dopant to the mass sum of the ferromanganese phosphate precursor, the lithium source, the first carbon source, and the dopant is 0.2% to 2%; and / or, the molar ratio of the lithium element of the lithium source to the phosphorus element of the lithium ferromanganese phosphate positive electrode material is (0.9 to 1.1): 1; and / or, the molar ratio of the sum of the manganese element and the iron element to the phosphorus element in the ferromanganese phosphate precursor is 1: (0.9 to 1.1); and / or, the carbon content of the lithium ferromanganese phosphate positive electrode material is 0.5% to 3%. The mass ratio of the dopant, the molar ratio of the lithium-phosphorus element, the molar ratio of the sum of the manganese-iron element to the phosphorus element, and the carbon content of the present embodiment can avoid excessive or insufficient dopant or carbon content to reduce the conductivity of the lithium ferromanganese phosphate positive electrode material, so that the molar ratio of the lithium-phosphorus element and the molar ratio of the sum of the manganese-iron element to the phosphorus element are in a suitable range, thereby improving the electrochemical performance of the lithium ferromanganese phosphate positive electrode material.

[0065] In some embodiments, the amount of dispersant added is 0.5% to 2.0% of the total mass of the third solution. The mass percentage of the dispersant in this embodiment can effectively disperse the precursor without increasing the cost, thereby forming a precursor that meets the requirements in morphology, crystal form and particle size. For example, the dispersant is polyethylene glycol, which has good water solubility (can effectively disperse particles in a water-based system), low toxicity, biocompatibility, and surface activity (having hydrophobic and hydrophilic parts, which can reduce interfacial tension and stabilize the suspension).

[0066] In some embodiments, the dopant is one or more combinations of titanium dioxide, magnesium oxide, magnesium hydroxide, niobium pentoxide, vanadium pentoxide, ammonium metavanadate, yttrium oxide, and zirconium oxide; and / or, the lithium source is one or more combinations selected from lithium hydroxide, lithium acetate, lithium oxalate, lithium carbonate, lithium tert-butoxide, lithium benzoate, lithium formate, lithium citrate tetrahydrate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, and lithium oxalate; and / or, the iron source comprises one or more combinations of metallic iron powder, metallic iron sheet, metallic iron ingot, red iron oxide, ferric oxide, ferric hydroxide, ferric sulfate, ferric nitrate, ferric phosphate, ferrous oxalate, ferrous oxide, ferric chloride, ferrous chloride, and hydrates thereof; and / or, the manganese source comprises one or more combinations of metallic iron powder, metallic iron sheet, metallic iron ingot, red iron oxide, ferric oxide, ferric hydroxide, ferrous sulfate, ferric nitrate, ferric phosphate, ferrous oxalate, ferrous oxide, ferric chloride, ferrous chloride, and hydrates thereof; Containing one or more combinations of metal manganese powder, metal manganese flakes, metal manganese ingots, manganese monoxide, manganese dioxide, manganese tetraoxide, manganese sulfate, manganese nitrate, manganese phosphate, manganese oxalate, manganese chloride and their hydrates; and / or, the phosphorus source is one or more combinations of ammonium dihydrogen phosphate, phosphoric acid, iron phosphate, lithium dihydrogen phosphate, ammonium phosphate, phosphorus pentoxide, and hydrogen phosphate; and / or, the first carbon source and the second carbon source are one or more combinations of graphite, glucose, sucrose, citric acid, starch, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, polyacrylamide, polyvinyl alcohol, and polyethylene glycol; and / or, the carrier gas or inert gas includes one or more combinations of nitrogen, argon, helium, neon, krypton, and xenon. This embodiment sets the types of dopants, lithium sources, iron sources, manganese sources, phosphorus sources, carbon sources, carrier gases, and dispersants, providing more choices, which is conducive to selection according to specific usage scenario requirements, and at the same time, the production cost is reduced due to the diversification of sources. The types of the first carbon source and the second carbon source may be the same or different, and are selected according to the specific usage scenario requirements, and are not limited in this embodiment.

[0067] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0068] Example 1

[0069] The high-temperature roasting device includes a first dissolving tank 1, a second dissolving tank 2, a mixing tank 3, a venturi processor 4, a pump 5, a valve 6, a vertical high-temperature roasting tower 7, a first material conveying tank 8 and a second material conveying tank 9; wherein the high-temperature roasting tower 7 includes a high-temperature roasting furnace and a sintering furnace connected to each other, the high-temperature roasting furnace includes a sprayer 71 arranged on the top, 6 groups of heaters 72 and 2 particle size regulators 73, the evaporation zone is provided with 3 groups of microwave heaters, the drying zone is provided with 2 groups of microwave heaters, and the roasting zone is provided with 1 group of gas heaters; the evaporation zone and the drying zone are each provided with a particle size regulator 73, and the sintering furnace includes a first sintering zone 74 close to the high-temperature roasting furnace, a second sintering zone 75 away from the high-temperature roasting furnace, and a movable baffle 76 for separating the first sintering zone 74 from the second sintering zone 75.

[0070] The preparation method of the lithium iron manganese phosphate cathode material is as follows:

[0071] S11: Mix 1 part of metal iron sheet, 1 part of ammonium phosphate and 5 parts of hydrochloric acid in terms of molar parts to obtain a first solution.

[0072] S12: Mix 1 part of metal manganese sheet and 5 parts of hydrochloric acid to obtain a second solution.

[0073] S2: Mix the first solution, the second solution and a third solution containing 1.0% of a dispersant based on the total mass of the third solution, and perform spray roasting granulation on the mixture through a two-fluid internal mixing type gas atomization in a high-temperature roasting furnace to obtain a lithium iron manganese phosphate precursor with two preset particle sizes. Among them, the first preset particle size is 600 nm < D501 ≤ 700 nm; the second preset particle size is 200 nm ≤ D502 ≤ 300 nm. The first inlet gas flow rate is 25 Nm 3 / h, and the second inlet gas flow rate is 35 Nm 3 / h. The total suspension time of the evaporation treatment, drying treatment and roasting treatment corresponding to the first preset particle size is 3.5 min, and the total suspension time of the evaporation treatment, drying treatment and roasting treatment corresponding to the second preset particle size is 4.0 min.

[0074] S3: Sinter the lithium iron manganese phosphate precursor and glucose with a carbon content of 0.5% of the lithium iron manganese phosphate cathode material in a nitrogen atmosphere in the first sintering zone 74 to obtain a lithium iron manganese phosphate calcined body. Among them, the parameters of the first sintering are: the sintering temperature is 600 °C, and the constant temperature time during sintering is 0.5 h.

[0075] S4: Sinter the lithium iron manganese phosphate calcined body, lithium oxalate, titanium dioxide and citric acid with a content of 1.0% of the lithium iron manganese phosphate cathode material in a nitrogen atmosphere in the second sintering zone 75 to obtain the lithium iron manganese phosphate cathode material. Among them, the parameters of the second sintering are: the sintering temperature is 650 °C, and the constant temperature time during sintering is 6 h.

[0076] Example 2: The difference from Example 1 is that the inlet gas time is adjusted to control the particle size, and the parameters of the first sintering and the second sintering are adjusted to the upper limit values.

[0077] In step S2, the first preset particle size is 700 nm < D501 ≤ 800 nm; the second preset particle size is 50 nm ≤ D502 ≤ 100 nm. Fix the first inlet gas flow rate at 8 Nm 3 / h, and adjust the first inlet gas time so that the total suspension time of the evaporation treatment, drying treatment and roasting treatment corresponding to the first preset particle size is 3.0 min. Fix the second inlet gas flow rate at 60 Nm 3 / h, and adjust the second intake time so that the total suspension time for the evaporation treatment, drying treatment, and calcination treatment corresponding to the second preset particle size is 5.0 min.

[0078] The parameters for the first sintering in step S3: the sintering temperature is 850 °C, and the constant temperature time during sintering is 3 h.

[0079] The parameters for the second sintering in step S4: the sintering temperature is 850 °C, and the constant temperature time during sintering is 14 h.

[0080] Example 3: The difference from Example 1 is that the intake flow rate and intake time are adjusted to control the particle size, and the parameters for the first sintering and the second sintering are adjusted to intermediate values.

[0081] In step S2, the first preset particle size is 650 nm < D501 ≤ 750 nm; the second preset particle size is 100 nm ≤ D502 ≤ 200 nm. Adjust the first intake flow rate to 25 Nm 3 / h, and adjust the first intake time so that the total suspension time for the evaporation treatment, drying treatment, and calcination treatment corresponding to the first preset particle size is 3.3 min. Adjust the second intake flow rate to 60 Nm 3 / h, and adjust the second intake time so that the total suspension time for the evaporation treatment, drying treatment, and calcination treatment corresponding to the second preset particle size is 4.5 min.

[0082] The parameters for the first sintering in step S3: the sintering temperature is 725 °C, and the constant temperature time during sintering is 1.75 h.

[0083] The parameters for the second sintering in step S4: the sintering temperature is 750 °C, and the constant temperature time during sintering is 10 h.

[0084] Comparative example: The difference from Example 1 is that no particle size regulator is set, the parameters for the first sintering and the second sintering are fixed to intermediate values, and only the manganese iron phosphate precursor and the lithium manganese iron phosphate cathode material with the second preset particle size are formed.

[0085] The manganese iron phosphate precursors prepared in Example 1, Example 2, Example 3, and the comparative example are made into lithium manganese iron phosphate cathode materials and then assembled into coin cells to test the tap density. After testing, the tap densities of Example 1, Example 2, Example 3, and the comparative example are 2.440 g / cm 3 、2.550 g / cm 3 、2.480 g / cm 3 and 2.380 g / cm 3 .

[0086] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0087] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0088] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing a lithium manganese iron phosphate positive electrode material, characterized in that: A lithium iron manganese phosphate positive electrode material is prepared based on a high-temperature roasting tower, wherein the high-temperature roasting tower includes a high-temperature roasting furnace and a sintering furnace connected to each other, wherein the high-temperature roasting furnace includes a sprayer arranged at the top, at least three groups of heaters, and at least two particle size regulators, wherein the heaters are arranged at the upper part and the middle part of the outer surface of the high-temperature roasting furnace, and the particle size regulator is arranged inside the high-temperature roasting furnace corresponding to the position of the heater, wherein the particle size regulator causes the sprayed droplets to move in reverse to adjust the suspension time of the atomized droplets to control the particle size of the ferromanganese phosphate precursor, and the sintering furnace includes a first sintering zone close to the high-temperature roasting furnace, a second sintering zone away from the high-temperature roasting furnace, and a movable baffle for separating the first sintering zone from the second sintering zone; The preparation method comprises: S11, mixing an iron source, a phosphorus source and hydrochloric acid to obtain a first solution; S12, mixing a manganese source and hydrochloric acid to obtain a second solution; S2, passing the first solution, the second solution and a third solution mixed with a dispersant through the high-temperature calcining furnace by a preset atomization method to spray-calculate and granulate to obtain at least two kinds of ferromanganese phosphate precursors with preset particle sizes; S3, sintering the ferromanganese phosphate precursor and the first carbon source once in an inert gas atmosphere in the first sintering zone to obtain a lithium ferromanganese phosphate calcined body; S4, performing secondary sintering on the lithium iron manganese phosphate calcined body, the lithium source, the dopant and the second carbon source in the inert gas atmosphere of the second sintering zone to obtain a lithium iron manganese phosphate positive electrode material; Wherein, any of the particle size regulators comprises a spiral air pipe, and a plurality of jet holes are arranged on one side of the spiral air pipe close to the sprayer, and the diameters of the jet holes in each semicircle of the spiral air pipe increase successively along the spiral air pipe extending from the inside to the outside; The jet holes of the spiral air pipe are distributed at preset angles in a clockwise or counterclockwise direction, or the jet holes of adjacent circles of the spiral air pipe are staggered.

2. The preparation method according to claim 1, characterized in that Any of the particle size regulators further comprises an air intake flow regulator, and the gas in the spiral air pipe is a carrier gas; step S2 comprises: Mixing the third solution with the carrier gas and setting the flow rate of the gas-liquid mixture through the sprayer to a preset flow rate, and then adjusting the nozzle of the sprayer to a preset aperture to spray in a preset atomization mode; The droplets of the atomized third solution are sequentially evaporated, dried and calcined in a top-down direction, and the air intake flow rate and / or air intake time of the carrier gas in the spiral air pipe are adjusted by the air intake flow regulator to form powdered manganese ferrophosphate precursors with at least two preset particle sizes.

3. The preparation method according to claim 2, characterized in that: The preset particle size includes a first preset particle size and a second preset particle size, the first preset particle size is larger than the second preset particle size, the intake flow rate of the carrier gas in the spiral air pipe includes a first intake flow rate and a second intake flow rate, the first intake flow rate is smaller than the second intake flow rate; The powdered ferromanganese phosphate precursor having at least two preset particle sizes is formed by adjusting the intake flow rate and / or intake time of the carrier gas in the spiral air pipe through the intake flow rate regulator, comprising: The air intake flow rate regulator adjusts the air intake flow rate of the carrier gas in the spiral air pipe to the first air intake flow rate to form the powdered manganese ferrophosphate precursor with the first preset particle size; The air intake flow rate regulator adjusts the air intake flow rate of the carrier gas in the spiral air pipe to the second air intake flow rate to form the powdered manganese ferrophosphate precursor with the second preset particle size.

4. The preparation method according to claim 2, characterized in that: The preset particle size includes a first preset particle size and a second preset particle size, the first preset particle size is larger than the second preset particle size, the intake flow rate of the carrier gas in the spiral air pipe is the preset intake flow rate, the intake time of the carrier gas in the spiral air pipe includes a first intake time and a second intake time, the first intake time is smaller than the second intake time; The powdered ferromanganese phosphate precursor having at least two preset particle sizes is formed by adjusting the intake flow rate and / or intake time of the carrier gas in the spiral air pipe through the intake flow rate regulator, comprising: The air intake flow rate regulator adjusts the air intake flow rate of the carrier gas in the spiral air pipe to the preset air intake flow rate and maintains the first air intake time to form the powdered manganese ferrophosphate precursor with the first preset particle size; The air intake flow regulator adjusts the air intake flow of the carrier gas in the spiral air pipe to the preset air intake flow and maintains the second air intake time to form the powdered manganese ferrophosphate precursor with the second preset particle size.

5. The preparation method according to claim 2, characterized in that: The preset particle size includes a first preset particle size and a second preset particle size, the first preset particle size is larger than the second preset particle size, the intake flow rate of the carrier gas in the spiral air pipe includes a first intake flow rate and a second intake flow rate, the first intake flow rate is smaller than the second intake flow rate, the intake time of the carrier gas in the spiral air pipe includes a first intake time and a second intake time, the first intake time is smaller than the second intake time; The powdered ferromanganese phosphate precursor having at least two preset particle sizes is formed by adjusting the intake flow rate and / or intake time of the carrier gas in the spiral air pipe through the intake flow rate regulator, comprising: The air intake flow rate regulator adjusts the air intake flow rate of the carrier gas in the spiral air pipe to the first air intake flow rate and maintains the first air intake time to form the powdered manganese ferrophosphate precursor with the first preset particle size; The air intake flow regulator adjusts the air intake flow of the carrier gas in the spiral air pipe to the second air intake flow and maintains the second air intake time to form the powdered manganese ferrophosphate precursor with the second preset particle size.

6. The preparation method according to any one of claims 4 to 5, characterized in that The first preset particle size is 600 nm <D501≦800 nm; And / or, the second preset particle size is 50 nm≦D502≦300 nm.

7. The preparation method according to claim 2, characterized in that The parameters of the primary sintering are as follows: the sintering temperature is 600°C to 850°C, and the constant temperature time during sintering is 0.5 h to 3 h; And / or, the parameters of the secondary sintering are: sintering temperature is 650°C to 850°C, and the constant temperature time during sintering is 6 h to 14 h; And / or, the calcination temperature is 500°C to 1000°C; And / or, the total time of the evaporation treatment, the drying treatment and the calcination treatment is 2 min to 5 min.

8. The preparation method according to claim 1, characterized in that: The mass ratio of the dopant to the ferromanganese phosphate precursor, the lithium source, the first carbon source, and the dopant is 0.2% to 2%; And / or, the molar ratio of the lithium element of the lithium source to the phosphorus element of the lithium iron manganese phosphate positive electrode material is (0.9-1.1):1; And / or, the molar ratio of the sum of manganese and iron elements to phosphorus in the ferromanganese phosphate precursor is 1:(0.9-1.1); And / or, the carbon content of the lithium manganese iron phosphate positive electrode material is 0.5%~3%.

9. The preparation method according to claim 2, characterized in that: The dopant is one or a combination of titanium dioxide, magnesium oxide, magnesium hydroxide, niobium pentoxide, vanadium pentoxide, ammonium metavanadate, yttrium oxide, and zirconium oxide; and / or, the lithium source is one or a combination of lithium hydroxide, lithium acetate, lithium oxalate, lithium carbonate, lithium tert-butoxide, lithium benzoate, lithium formate, lithium citrate tetrahydrate, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate and lithium oxalate; And / or, the iron source comprises one or a combination of metallic iron powder, metallic iron flakes, metallic iron ingots, red iron oxide, ferric oxide, ferric oxyhydroxide, ferric sulfate, ferric nitrate, ferric phosphate, ferrous oxalate, ferric oxide, ferric chloride, ferrous chloride and ferrous chloride hydrate; And / or, the manganese source comprises one or a combination of metallic manganese powder, metallic manganese flakes, metallic manganese ingots, manganese monoxide, manganese dioxide, manganese tetraoxide, manganese sulfate, manganese nitrate, manganese phosphate, manganese oxalate, manganese chloride and manganese chloride hydrate; and / or, the phosphorus source is one or a combination of diammonium phosphate, phosphoric acid, iron phosphate, lithium dihydrogen phosphate, ammonium phosphate, phosphorus pentoxide, and hydrogen phosphate; And / or, the first carbon source and the second carbon source are one or a combination of graphite, glucose, sucrose, citric acid, starch, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, polyacrylamide, polyvinyl alcohol, polyethylene glycol; And / or, the carrier gas or the inert gas includes one or more combinations of nitrogen, argon, helium, neon, krypton, and xenon.

10. A lithium battery, characterized in that: The lithium battery comprises a positive electrode plate, and the positive electrode plate is made of the lithium iron manganese phosphate positive electrode material as described in any one of claims 1 to 9.

Images