TWI840972B - Positive electrode material semi-finished product, positive electrode material preparation method and preparation device - Google Patents

Abstract

The present invention provides a cathode material semi-finished product, a cathode material preparation method and a preparation device. The sintering reactor for preparing cathode materials of the present invention comprises a reactor shell, a heater, a feed port, a discharge port and at least two material carriers connected in series, the feed port and the discharge port are located at two ends of the reactor shell, the heater and the material carrier are located in the reactor shell, the heater is used to heat the material, the material carrier is used to transport the material from the feed port to the discharge port, and the material carrier can vibrate. The cathode material preparation method of the present invention comprises a granulation section and a sintering section. After granulation by the method of the present invention, the particles have fluidity and a higher particle density, which is conducive to the infiltration of oxygen or air between the raw material particles and also conducive to the conduction of heat into the particles, thereby improving the consistency of product quality and reducing the reaction sintering time.

Description

Positive electrode material semi-finished product, positive electrode material preparation method and preparation device

The invention belongs to the field of positive electrode materials, and relates to a positive electrode material semi-finished product, a positive electrode material preparation method and a preparation device.

The current mainstream technology uses dry mixing of precursors and lithium salts or static sintering after granulation to prepare cathode materials. In terms of ingredients, direct dry mixing can easily lead to uneven distribution of lithium salts and precursors, resulting in areas where lithium salts are missing. The diffusion path of lithium ions in the precursor will be too long, greatly increasing the reaction time. After granulation by traditional methods, the pores between particles are large, which is not conducive to heat conduction inside the particles. In terms of sintering, static sintering has defects in heat and mass transfer, uneven thermal field, long reaction time, hard agglomeration between particles during sintering, difficult to crush, and poor product consistency; at the same time, the sintering production process usually uses a sagger to load powder, the use of saggers increases energy consumption and production auxiliary material costs, and also adds two loading and unloading processes. Recently, the use of fluidized bed technology to achieve positive electrode material sintering has emerged. However, the existing fluidized bed sintering technology has restrictions on particle size and specific gravity, and has high process requirements. In addition, fluidizing the powder through airflow can easily cause excessive dynamics between particles, resulting in particle breakage, high loss rate, and is not conducive to particle fusion and grain boundary migration, making it difficult to obtain products with target particle size.

In view of the above problems, the present invention provides a method and device for preparing a cathode material semi-finished product, as well as a method and device for processing the cathode material semi-finished product into a cathode material. The cathode material preparation method of the present invention includes a granulation section and a sintering section. After granulation using the method of the present invention, the particles have fluidity and a higher particle density, which is conducive to oxygen or air infiltration between the raw material particles and heat conduction to the inside of the particles, which can improve product quality consistency and reduce reaction sintering time. Specifically, one aspect of the present invention provides a sintering reactor for preparing positive electrode materials, the sintering reactor comprising a reactor shell, a heater, a feed port, a discharge port and at least two material carriers connected in series, the feed port and the discharge port are located at two ends of the reactor shell, the heater and the material carrier are located in the reactor shell, the heater is used to heat the material, the at least two material carriers connected in series are used to transport the material from the feed port to the discharge port, and the material carrier can vibrate. In one or more embodiments, the material carrier can vibrate with variable frequency. In one or more embodiments, the material carrier has an inclination angle of 40-75°, preferably 45-70°, with respect to the horizontal plane. In one or more embodiments, there is no tilt angle between the material carrier and the horizontal plane. In one or more embodiments, the number of the material carriers is 3-20, preferably 10-15. In one or more embodiments, the sintering reactor further includes a reciprocating motor and a crankshaft, and the crankshaft connects the reciprocating motor and the material carrier. In one or more embodiments, the sintering reactor further includes a lifting support rod, and the lifting support rod is connected to the reactor shell. In one or more embodiments, the sintering reactor further includes a heat preservation layer, and the heat preservation layer is arranged above the heater. Another aspect of the present invention provides a cathode material preparation system, which includes a granulation device and a sintering reactor as described in any embodiment of the present invention; preferably, the granulation device is a spray fusion machine. Another aspect of the present invention provides a cathode material preparation method, which includes using the sintering reactor or cathode material preparation system as described in any embodiment of the present invention to prepare the cathode material. Another aspect of the present invention provides a method for preparing a semi-finished cathode material, the method comprising a granulation step, the granulation step comprising: coating a lithium hydroxide precursor and/or a lithium carbonate precursor on the surface of one or more of a cathode material, an oxide precursor and a lithium oxide precursor to obtain coated particles, calcining the coated particles , the lithium hydroxide precursor and/or lithium carbonate precursor on the surface of the coated particles are converted into lithium oxide precursors to obtain calcined particles. If the calcined particles do not reach the target particle size, the lithium hydroxide precursor and/or lithium carbonate precursor are coated again on the surface of the calcined particles, and then calcined until the calcined particles reach the target particle size. In one or more embodiments, the particle size of one or more of the positive electrode material, oxide precursor and lithium oxide precursor to be coated is 1.5-6μm, preferably 2-3μm. In one or more embodiments, the particle size of the lithium hydroxide precursor and/or lithium carbonate precursor as the coating agent is 20-250 nm, preferably 100-200 nm. In one or more embodiments, two or more coatings and calcinations are performed during the coating process. In one or more embodiments, each coating and calcination increases the particle size of the particles by 0.3-0.9 μm, preferably 0.4-0.8 μm. In one or more embodiments, the coating and calcination are performed by spray fusion. In one or more embodiments, a dispersion of a lithium hydroxide precursor and/or a lithium carbonate precursor is used for spraying, and the concentration of the dispersion is preferably 1-10wt%. In one or more embodiments, the stirring speed during fusion is 1200±200rpm. In one or more embodiments, the heating temperature during fusion is 500±50℃. In one or more embodiments, the heating time during fusion is 1±0.2 hours. In one or more embodiments, the target particle size of the calcined particles is 3.5-8μm, preferably 4-5μm. In one or more embodiments, a lithium hydroxide precursor is used for coating. Another aspect of the present invention provides a method for preparing a positive electrode material, the method comprising a granulation step and a sintering step, the granulation step being as described in any embodiment of the present invention, and the sintering step comprising: sintering the calcined particles having a target particle size obtained in the granulation step. In one or more embodiments, the sintering temperature is 800-1200°C, preferably 900±50°C. In one or more embodiments, in the sintering step, the sintering is performed using a sintering reactor as described in any embodiment of the present invention. Another aspect of the present invention provides a positive electrode material semi-finished particle, which is a calcined particle with a target particle size prepared by the method for preparing a positive electrode material semi-finished product described in any embodiment of the present invention. In one or more embodiments, the particle size of the positive electrode material semi-finished particle is 3.5-8μm, preferably 4-5μm. Another aspect of the present invention provides a positive electrode material, which is prepared by the method for preparing a positive electrode material described in any embodiment of the present invention. In one or more embodiments, the particle size of the positive electrode material ranges from 3500-8000nm, preferably from 4000-4500nm. In one or more embodiments, the cathode material is a cathode material with a core-shell structure or without a core-shell structure, the core layer material and the shell layer material of the cathode material with a core-shell structure are each independently a ternary nickel-cobalt-manganese cathode material, a ternary nickel-cobalt-aluminum cathode material, or a quaternary nickel-cobalt-manganese-aluminum cathode material, and the cathode material without a core-shell structure is a ternary nickel-cobalt-manganese cathode material, a ternary nickel-cobalt-aluminum cathode material, or a quaternary nickel-cobalt-manganese-aluminum cathode material.

In order to enable those skilled in the art to understand the features and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and the application. Unless otherwise specified, all technical and scientific terms used in this document are the common meanings understood by those skilled in the art for the present invention. In case of conflict, the definitions in this specification shall prevail. The theories or mechanisms described and disclosed in this document, whether right or wrong, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism. Herein, "comprising", "including", "containing", "having" and similar terms cover the meanings of "consisting essentially of" and "consisting of", for example, when "A comprises B and C" is disclosed herein, "A consists essentially of B and C" and "A consists of B and C" should be considered to have been disclosed herein. Herein, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible secondary ranges and individual numerical values within the range (including integers and fractions). Herein, in order to make the description concise, not all possible combinations of various technical features in various embodiments or embodiments are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification. When the positive electrode material is produced by conventional methods, the powder will be hard agglomerated after high-temperature sintering, which is difficult to crush and easily produces fine powder, affecting the quality. The present invention solves the problems of long reaction time between the positive electrode material precursor and the lithium salt, high energy consumption, and poor product quality consistency through a new granulation and dynamic high-temperature sintering method. The granulation section is shown in FIG1 . The present invention adopts a special granulation process, with one or more of the cathode material, oxide precursor and lithium-containing oxide precursor as the core, and the lithium-containing hydroxide precursor and/or the lithium-containing carbonate precursor as the shell. The lithium-containing hydroxide precursor and/or the lithium-containing carbonate precursor are coated on one or more surfaces of the cathode material, oxide precursor and lithium-containing oxide precursor. After high-temperature calcination, dehydration and degassing, the lithium-containing hydroxide precursor and/or the lithium-containing carbonate precursor are transformed into the lithium-containing oxide precursor to form particles with increased particle size. In some embodiments, the particles with increased particle size are used as new cores for the next coating, and are coated and calcined multiple times until the obtained particles reach the target particle size. In the present invention, a single coating and calcination can be performed, or multiple coating and calcination (twice or more, for example, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times) can be performed. Single coating and calcination can improve the interface and optimize the electrochemical properties. Multiple coating and calcination can improve the density and uniformity of granulation, shorten the sintering time, and improve the electrochemical properties. After granulation using the method of the present invention, the particles have fluidity and a higher particle density, which is conducive to the infiltration of oxygen or air between the raw material particles and the heat conduction to the inside of the particles, which can improve the quality consistency and reduce the reaction sintering time. In the present invention, the calcined particles with the target particle size can be used as a positive electrode material semi-finished product. Figure 2 shows the difference between the granulation process in some embodiments of the present invention and the granulation process of the prior art. In some embodiments, the present invention obtains particles with a target particle size by repeatedly coating one or more surfaces of the positive electrode material, the oxide precursor and the lithium-containing oxide precursor with a lithium hydroxide precursor and/or a lithium carbonate precursor and then calcining them in a cycle, while the prior art obtains particles with a target particle size by calcining the lithium hydroxide precursor or the lithium carbonate precursor in one step. The positive electrode material, the oxide precursor and the lithium-containing oxide precursor used as the core of the granulation stage of the present invention can be single crystal particles or polycrystalline particles. The D50 particle size of the single crystal particles can be 2-5 μm, such as 2.3 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm. The D50 particle size of the polycrystalline particles can be 10-15 μm, such as 11 μm, 12 μm, 13 μm, 14 μm. Using single crystal particles and polycrystalline particles with a D50 particle size within the above range as cores is beneficial for obtaining a good granulation effect. In some embodiments, the present invention uses single crystal particles of positive electrode material as cores. In some embodiments, the oxide precursor is a transition metal oxide. In some embodiments, the lithium-containing oxide precursor is a complex or mixture of (1) Li ₂ O and (2) a transition metal oxide. In some embodiments, the lithium oxide precursor is a mixture of (1) Li ₂ O and (2) a transition metal oxide. In some embodiments, the lithium hydroxide precursor is a complex or mixture of (1) a lithium salt (e.g., LiOH, Li ₂ CO ₃ ) and (2) a transition metal hydroxide. In some embodiments, the lithium hydroxide precursor is a mixture of (1) a lithium salt (e.g., LiOH, Li ₂ CO ₃ ) and (2) a transition metal hydroxide. In some embodiments, the lithium carbonate precursor is a complex or mixture of (1) a lithium salt (e.g., LiOH, Li ₂ CO ₃ ) and (2) a transition metal carbonate. In some embodiments, the lithium carbonate precursor is a mixture of (1) a lithium salt (e.g., LiOH, Li ₂ CO ₃ ) and (2) a transition metal carbonate. In the present invention, the cathode material, the oxide precursor, the lithium oxide precursor, the lithium hydroxide precursor, and the lithium carbonate precursor may be doped, and the doping elements include but are not limited to one or more of Al, Zr, Sr, Mg, Ti, B, ytterbium, halogen, Mo, Cu, V, Ca, Ru, W, Os, Fe, Ga, In, P, Cr, Ce, Nb, Y, Sn, Ta, Ni, Co, Mn, Si, Ba, etc. In the present invention, the metal elements in the transition metal oxide, transition metal hydroxide and transition metal carbonate may be one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, for example, nickel cobalt manganese, nickel cobalt aluminum, nickel cobalt manganese aluminum, iron, manganese iron, cobalt, manganese, titanium, nickel cobalt, nickel manganese and the like. Preferably, the transition metal oxide, transition metal hydroxide and transition metal carbonate contain at least two metal elements selected from nickel, cobalt, manganese, aluminum, iron and titanium, such as nickel cobalt manganese, nickel cobalt aluminum, nickel cobalt manganese aluminum, manganese iron, nickel cobalt, nickel manganese and the like. In addition to being used to prepare nickel-cobalt-manganese ternary cathode materials and nickel-cobalt-aluminum ternary cathode materials, the present invention can also be used to prepare other cathode materials, such as lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganate, lithium titanium oxide, nickel-cobalt-manganese-aluminum quaternary cathode material (NCMA), nickel-cobalt binary cathode material (NC), nickel-manganese binary cathode material (NM), etc. In the present invention, the lithium salt can be one or more selected from lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium oxide, lithium sulfate, lithium bisulfate, lithium fluoride, lithium chloride, lithium bromide, lithium nitrate, lithium acetate and lithium peroxide, preferably one or more selected from lithium hydroxide, lithium carbonate, lithium bicarbonate and lithium oxide, more preferably one or both selected from lithium hydroxide and lithium carbonate. In some embodiments, the lithium oxide precursor, lithium hydroxide precursor or lithium carbonate precursor contains substantially one lithium salt, and the “substantially one lithium salt” refers to only one lithium salt, or a mixture of two or more lithium salts, wherein one lithium salt accounts for at least 90 wt % of the total lithium salt. The positive electrode material may have a layered structure or a spinel structure. In some embodiments, the cathode material is selected from lithium metal oxide having a layered structure, lithium spinel, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, nickel cobalt manganese ternary cathode material, nickel cobalt aluminum ternary cathode material, lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganate, lithium titanium oxide, nickel cobalt manganese aluminum quaternary cathode material (NCMA), nickel cobalt binary cathode material (NC), nickel manganese binary cathode material (NM). Examples of positive electrode materials include Li1 ₊ iM1 _{-iO2 +m} , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, i is 0-0.2, such as 0, 0.01, 0.025, 0.05, 0.1, and m is 0-1, such as 0, 0.05, 0.1, 0.2, 0.5. For example, the cathode material may be Li1 ₊ iM1 _{-iO2 ,} wherein M is _NixCoyMnz or _NixCoyAlz , x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, _0.8 , 0.88, y is 0.01-0.4, such as 0.02, 0.05 _{, 0.09} , _0.1 , 0.2, 0.3, z is 0.01-0.4, such as 0.02, 0.03, 0.05, 0.1, 0.2, 0.3, i is 0-0.2, such as 0, 0.01, 0.025, _0.05 , _0.1 ; or, M _{is NiaCobMncAld} , a+b+c+d=1, a is 0.3-0.95, such as 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, b is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, c is 0.001-0.2, such as 0.002, 0.004, 0.005, 0.01, 0.05, 0.1, d is 0.001-0.2, such as 0.002, 0.005, 0.01, 0.02, 0.05, 0.1. Examples of oxide precursors include MO _2+m , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, and m is 0-1, such as 0, 0.05, 0.1, 0.2, 0.5. For example, the oxide precursor can be _MO2 , wherein M is _NixCoyMnz or _{NixCoyAlz ,} x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, 0.8, y is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2 _{, 0.3} , and z is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, _0.3 . Examples of lithium carbonate precursors include mixtures of lithium salts (e.g., LiOH, Li ₂ CO ₃ ) and M(CO ₃ ) _1+n , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, and n is 0-0.5, e.g., 0, 0.025, 0.05, 0.1, 0.25. For example, the lithium carbonate precursor can be a mixture of a lithium salt (such as LiOH, Li ₂ CO ₃ ) and MCO ₃ , wherein M is Ni _x Co _y Mn _z or Ni _x Co _y Al _z , x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, 0.8, y is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3, and z is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3. Examples of lithium-containing oxide precursors include mixtures of _Li2O and MO2 _+m , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, and m is 0-1, such as 0, 0.05, 0.1, 0.2, 0.5. For example, the lithium-containing oxide precursor may be a mixture of _Li2O and _MO2 , wherein M is _{NixCoyMnz or NixCoyAlz} , x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, _0.8 , y is 0.01-0.4, such as 0.02, 0.05, 0.1, _0.2 , _0.3 , and z is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3. Examples of lithium hydroxide-containing precursors include mixtures of lithium salts (e.g., LiOH, Li ₂ CO ₃ ) and M(OH) _2+m , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron, and titanium, and m is 0-1, e.g., 0, 0.05, 0.1, 0.2, 0.5. For example, the lithium hydroxide precursor can be a mixture of a lithium salt (such as LiOH, Li ₂ CO ₃ ) and M(OH) ₂ , wherein M is Ni _x Co _y Mn _z or Ni _x Co _y Al _z , x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, 0.8, y is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3, and z is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3. Examples of lithium carbonate precursors include mixtures of lithium salts (e.g., LiOH, Li ₂ CO ₃ ) and M(CO ₃ ) _1+n , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, and n is 0-0.5, e.g., 0, 0.025, 0.05, 0.1, 0.25. For example, the lithium carbonate precursor can be a mixture of a lithium salt (such as LiOH, Li ₂ CO ₃ ) and MCO ₃ , wherein M is Ni _x Co _y Mn _z or Ni _x Co _y Al _z , x+y+z=1, x is 0.3-0.9, such as 0.4, 0.5, 0.6, 0.7, 0.8, y is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3, and z is 0.01-0.4, such as 0.02, 0.05, 0.1, 0.2, 0.3. In the present invention, the cathode material, oxide precursor or lithium-containing oxide precursor as the core in the granulation section and the lithium-containing hydroxide precursor or lithium-containing carbonate precursor as the shell can correspond to the same type or different types of cathode materials. When corresponding to the same type of cathode materials, the ratio of transition metal elements in the core and the shell can be the same or different. Therefore, the cathode material prepared by the present invention can be a cathode material with a core-shell structure or a cathode material without a core-shell structure. When the cathode material is a cathode material with a core-shell structure, the shell material and the core material of the cathode material can be different types of cathode materials, or cathode materials of the same type but with different ratios of transition metal elements, for example, the shell material and the core material of the cathode material can be independently selected from nickel-cobalt-manganese ternary cathode material, nickel-cobalt-aluminum ternary cathode material, and nickel-cobalt-manganese-aluminum quaternary cathode material. In some embodiments, the prepared cathode material is nickel-cobalt-manganese ternary cathode material or nickel-cobalt-aluminum ternary cathode material. In some embodiments, the prepared cathode material has a core-shell structure, wherein the core layer material is a nickel-cobalt-aluminum ternary cathode material or a nickel-cobalt-manganese-aluminum quaternary cathode material, and the shell layer material is a nickel-cobalt-manganese ternary cathode material. In the present invention, various cathode materials and their precursor feeds can be used. For example, when preparing a nickel-cobalt-manganese ternary cathode material, an oxide precursor containing nickel, cobalt and manganese (e.g., a chemical formula of Ni _x Co _y Mn _z O ₂ , wherein x+y+z=1), a lithium-containing oxide precursor containing nickel, cobalt and manganese (e.g., a mixture of a transition metal oxide with a chemical formula of Ni _x Co _y Mn _z O ₂ and Li ₂ O, wherein x+y+z=1) and/or a cathode material containing nickel, cobalt and manganese (e.g., a chemical formula of LiNi _x Co _y Mn _z O ₂ , wherein x+y+z=1) can be used as a core, and a lithium-containing hydroxide precursor containing nickel, cobalt and manganese (e.g., a transition metal hydroxide with a chemical formula of Ni _x Co _y Mn _z (OH) ₂ and a selected from LiOH and Li ₂ CO ₃ , wherein x+y+z=1) and/or a lithium carbonate precursor containing nickel, cobalt and manganese (e.g., a transition metal carbonate with a chemical formula of Ni _x Co _y Mn _z CO ₃ and a mixture of one or two selected from LiOH and Li ₂ CO ₃ , wherein x+y+z=1) as a coating agent feed; when preparing a nickel-cobalt-aluminum ternary cathode, an oxide precursor containing nickel, cobalt and aluminum (e.g., a chemical formula of Ni _x Co _y Al _z O ₂ , wherein x+y+z=1), a lithium oxide precursor containing nickel, cobalt and aluminum (e.g., a transition metal oxide with a chemical formula of Ni _x Co _y Al _z O ₂ and Li ₂ O, wherein x+y+z=1) and/or a cathode material containing nickel, cobalt and aluminum (for example, a chemical formula of LiNi _x Co _y Al _z O ₂ , wherein x+y+z=1) is used as a core, and a lithium hydroxide precursor containing nickel, cobalt and aluminum (for example, a mixture of a transition metal hydroxide with a chemical formula of Ni _x Co _y Al _z (OH) ₂ and one or two selected from LiOH and Li ₂ CO ₃ , wherein x+y+z=1) and/or a lithium carbonate precursor containing nickel, cobalt and aluminum (for example, a mixture of a transition metal carbonate with a chemical formula of Ni _x Co _y Al _z CO ₃ and one or two selected from LiOH and Li ₂ CO ₃ , wherein x+y+z=1) is used as a coating agent feed. In the present invention, a lithium hydroxide precursor and/or a lithium carbonate precursor are coated on the surface of one or more of a positive electrode material, an oxide precursor and a lithium oxide precursor in a granulation stage to obtain coated particles, and then the coated particles are subjected to high-temperature calcination, dehydration and degassing to convert the lithium hydroxide precursor and/or the lithium carbonate precursor on the surface of the coated particles into a lithium oxide precursor, so that the coated particles are converted as a whole into particles with an increased particle size (calcined particles). In some preferred embodiments, the calcined particles are used as cores, and the surface is coated with a lithium hydroxide precursor and/or a lithium carbonate precursor again, and then calcined again, and the process is repeated until the calcined particles reach the target particle size. In the present invention, in some preferred embodiments, at least two coating and calcining operations are performed by controlling the coating amount. Multiple coating and calcining operations are beneficial to making the coated particles dense in structure, and the grain boundaries are easy to fuse during sintering, and the time is shortened. In the present invention, "one or more of positive electrode materials, oxide precursors and lithium-containing oxide precursors" means a material or a mixture of materials selected from the following: one or more positive electrode materials, one or more oxide precursors, and one or more lithium-containing oxide precursors, which can be used as the core to be coated. "Lithium-containing hydroxide precursors and/or lithium-containing carbonate precursors" means one or more lithium-containing hydroxide precursors, one or more lithium-containing carbonate precursors, or a mixture of one or more lithium-containing hydroxide precursors and one or more lithium-containing carbonate precursors, which can be used as coating agents. In the present invention, lithium-containing hydroxide precursors are preferably used for coating. In the present invention, the metal elements contained in one or more of the positive electrode material, oxide precursor and lithium-containing oxide precursor as the core and the lithium-containing hydroxide precursor and/or lithium-containing carbonate precursor as the shell (coating agent) may be the same or different. For example, a lithium-containing hydroxide precursor containing nickel, cobalt and aluminum may be coated on the surface of an oxide precursor containing nickel, cobalt and manganese. In some embodiments, one or more of the cathode material, oxide precursor and lithium-containing oxide precursor as the core contains the same type of metal element other than lithium as the lithium-containing hydroxide precursor and/or lithium-containing carbonate precursor as the shell (coating agent), such as nickel, cobalt and manganese. When one or more of the cathode material, oxide precursor and lithium-containing oxide precursor as the core contains the same type of metal element other than lithium as the lithium-containing hydroxide precursor and/or lithium-containing carbonate precursor as the shell (coating agent), the ratios of the metal elements other than lithium may be the same or different. For example _, a mixture of _{Ni0.8Co0.1Mn0.1} (OH) ₂ and LiOH as a lithium _hydroxide precursor can be coated on the surface of one _{or more of} an oxide precursor _{Ni0.8Co0.1Mn0.1O2} having the same ratio of metal elements other than lithium, a mixture of a lithium _{oxide precursor Li2O and Ni0.8Co0.1Mn0.1O2 , and} a positive _electrode material _{LiNi0.8Co0.1Mn0.1O2 . Alternatively} , _a mixture of _{Ni0.5Co0.2Mn0.3} (OH) ₂ and _LiOH as a lithium hydroxide precursor can be coated on an oxide precursor _{Ni0.8Co0.1Mn0.1O2 having a} different ratio _of metal elements other than _{lithium .} , a mixture of lithium-containing oxide precursor Li ₂ O and Ni _0.8 Co _0.1 Mn _0.1 O ₂ , and a positive electrode material LiNi _0.8 Co _0.1 Mn _0.1 O _2. In the present invention, the particle size of one or more of the positive electrode material to be coated, the oxide precursor, and the lithium-containing oxide precursor as the core of the first coating is preferably 1.5-6μm, for example, 2μm, 2.3μm, 2.5μm, 3μm, 4μm, 5μm. The particle size of the lithium hydroxide precursor and/or lithium carbonate precursor as a coating agent is preferably 20-250 nm, for example 30 nm, 50 nm, 100 nm, 120 nm, 140 nm, 150 nm, 160 nm, 180 nm, 200 nm. In the present invention, when the lithium hydroxide precursor as a coating agent is a mixture of a lithium salt and a transition metal hydroxide, the particle size of the lithium hydroxide precursor as a coating agent refers to the particle size of the transition metal hydroxide in the mixture. When the lithium carbonate precursor as a coating agent is a mixture of a lithium salt and a transition metal carbonate, the particle size of the lithium carbonate precursor as a coating agent refers to the particle size of the transition metal carbonate in the mixture. When the particle size of the core coated for the first time is significantly different from the target particle size of the calcined particles, it is preferred to perform coating and calcination multiple times (twice or more, for example, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times). Each coating and calcination preferably increases the particle size of the particles by 0.3-0.9 μm, for example, by 0.4 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm. The target particle size of the particles after calcination is preferably 3.5-8 μm, for example, 3.7 μm, 4 μm, 4.2 μm, 4.4 μm, 4.5 μm, 4.8 μm, 5 μm, 6 μm, 7 μm. Controlling the aforementioned particle size values within the aforementioned range is conducive to coating, improving the fluidity of the particles, making the particle density greater, and facilitating the infiltration of oxygen or air between the raw material particles, and also facilitating heat conduction to the inside of the particles, which can improve quality consistency and reduce the reaction sintering time. If the one-time coating thickness is too large, it is easy to contain fine powder, poor fluidity, and it is difficult to form particles of uniform size. In this article, unless otherwise specified, the particle size refers to the median particle size. The median particle size of the particles can be measured by microscopy. In some embodiments, the particle size of one or more of the positive electrode material, oxide precursor and lithium-containing oxide precursor to be coated is 2-3 μm, the particle size of the lithium-containing hydroxide precursor and/or lithium-containing carbonate precursor as the coating agent is 100-200 nm, and the coating and calcination operations are performed three to five times (e.g., three, four or five times), and each coating and calcination operation preferably increases the particle size of the particles by 0.4-0.8 μm, thereby obtaining calcined particles with a target particle size of 4-5 μm. In the present invention, it is preferred to use a spray fusion method for coating and calcining, that is, the coating can be achieved by spraying a dispersion formed by a lithium hydroxide precursor and/or a lithium carbonate precursor in a solvent (such as water) onto one or more surfaces of the positive electrode material, the oxide precursor and the lithium oxide precursor, and then calcining is performed by fusion. The concentration (solid content) of the dispersion is preferably 1-10wt%, such as 2wt%, 2.5wt%, 3wt%, 4wt%, 5wt%, 7.5wt%, which is conducive to the atomization of the dispersion and the realization of uniform coating. Fusion refers to the operation in which the material surface reaches a mechanical molten coating state under the action of extrusion and shear force under high-speed rotation. A spray fusion machine may be used for the spray fusion operation. The structure of the spray fusion machine may be known in the art. The stirring speed during fusion may be 1200±200 rpm, the heating temperature may be 500±50°C, and the heating time may be 1±0.2 hours. The spray fusion operation may be performed multiple times until the particle size reaches the process design target. In some embodiments, a dispersion of a lithium hydroxide precursor and/or a lithium carbonate precursor is pumped into a centrifugal spray nozzle by a peristaltic pump, mixed and coated with one or more of a cathode material, an oxide precursor and a lithium oxide precursor, to obtain coated particles, and then the stirring device and heating device of the fusion machine are turned on to perform high-temperature calcination, dehydration and degassing to obtain calcined particles. The calcined particles prepared by the granulation process of the present invention are a semi-finished cathode material, and the particle size is preferably 3.5-8μm, for example, 3.7μm, 4μm, 4.5μm, 5μm, 6μm. The particles have excellent fluidity (non-sticky) and a large particle density (2.0 g/cm ³ to 2.8 g/cm ³ ), which is conducive to the infiltration of oxygen or air between the raw material particles and the conduction of heat into the particles, which can improve the quality consistency and reduce the reaction sintering time. Sintering section The present invention sintered the precursor particles (e.g., the calcined particles with the target particle size obtained in the granulation section) into the positive electrode material in the sintering section. The sintering can be static sintering or dynamic sintering, preferably dynamic sintering. Dynamic sintering can be performed using dynamic sintering equipment known in the art, such as a fluidized bed, and is preferably performed in the sintering reactor of the present invention. The sintering reactor of the present invention is a moving bed reactor. The sintering reactor of the present invention includes a reactor shell, a heater, a feed port, a discharge port, and at least two material carriers connected in series. The reactor shell is a cylindrical container, and its cross-section can be circular, elliptical, square, polygonal, etc. The feed port and the discharge port are located at both ends of the reactor shell. The heater is located in the reactor shell and is used to heat the material. The material carrier is in the shape of a groove, including a carrier plate and protrusions located on both sides of the carrier plate to prevent the material from falling out. The material of the material carrier can be ceramic. The material carrier is located in the reactor shell, and the two ends of the series material carrier are respectively connected to the feed port and the discharge port, and are used to transport the material from the feed port to the discharge port. The material carrier can preferably vibrate to make the raw material powder in the material carrier dynamic. In some embodiments, the sintering reactor includes a reciprocating motor and a crankshaft, and the crankshaft connects the reciprocating motor and the material carrier to achieve the vibration of the material carrier. Preferably, the material carrier can be vibrated with variable frequency to avoid resonance between the powder and the material carrier during vibration, so that turbulence can be achieved during the powder transmission process, ensuring that the material is flipped up and down, thereby ensuring the consistency of product quality. In some embodiments, the frequency of the reciprocating motor is variable frequency, so that the material carrier vibrates at different frequencies within a certain period of time. In some embodiments, the sintering reactor includes two or more material carriers, which are connected in series along the direction from the feed port to the discharge port. The number of material carriers can be 3 or more, for example, 3-20, 10-15, or 12. In some embodiments, the sintering reactor includes a number of reciprocating motors and crankshafts equal to the number of material carriers, and each material carrier is independently connected to a reciprocating motor through a crankshaft. There may or may not be a tilt angle between the material carrier and the horizontal plane. Preferably, the material carrier has a certain tilt angle so that the powder can be transferred downward along the carrier under its own weight. The tilt angle of the material carrier can be 40-75°, for example, 45-70°, 55-75°, 60-70°, 60°, 61°, 62°, 63°, 64°, 65°, 70°. In some embodiments, the tilt angle of the material carrier is adjusted according to the repose angle of the calcined particles so that the material can be transferred downward along the carrier under the condition of dead weight. The tilt angle of the material carrier can be set to be 1-10° less than the repose angle of the calcined particles, for example, 2°, 3°, 4°, 5°. In the present invention, the repose angle of the calcined particles can be 45-85°, for example, 50°, 52°, 60°, 66°, 67°, 68°, 70°, 71°, 75°. Herein, the angle of repose is the angle between the free surface and the horizontal plane when the free surface of the powder accumulation body is in an extreme state of equilibrium. In some embodiments, the sintering reactor has a lifting function so that the material carrier has a certain tilt angle. In some embodiments, the sintering reactor includes a lifting support rod, which is connected to the reactor shell and is used to make the material carrier have a certain tilt angle. In some embodiments, the sintering reactor includes a fixed support rod and a lifting support rod, one of the fixed support rod and the lifting support rod is connected to the side of the reactor shell close to the discharge port, and the other is connected to the side of the reactor shell close to the feed port. The tilt of the reactor shell is achieved by the height difference between the fixed support rod and the lifting support rod, so that the material carrier has a certain tilt angle. In some embodiments, the sintering reactor includes a base, and one end of the lifting support rod and the optional fixed support rod is connected to the reactor shell, and the other end is connected to the base. The present invention makes the material dynamic through the mechanical vibration of the material carrier with a certain tilt angle, and realizes the following functions: 1. Make the high-temperature gas fully contact with the material and react evenly; 2. There is displacement between the particles to avoid hard agglomeration of particles; 3. The powder flows on the carrier with a tilt angle to realize material transmission and continuous production. The heater is preferably arranged on the upper part of the material carrier. In some embodiments, the heater is arranged in the reactor shell along the entire length from the feed port to the discharge port. In some embodiments, the sintering reactor includes a thermal insulation layer, and the thermal insulation layer is arranged above the heater. The heater is preferably arranged so that the thermal field temperature of the material carrier reaches 800-1200°C, for example, 900±50°C. As shown in FIG3 , in some embodiments, the sintering reactor of the present invention includes a reactor shell, a heat preservation layer 1, a heater 2, a feed port 3, a discharge port 4, two or more material carriers 5, two or more reciprocating motors and crankshafts 6, a fixed support rod 7, a lifting support rod 8 and a base 9. The feed port 3 and the discharge port 4 are arranged at the two ends of the reactor shell, the insulation layer 1, the heater 2 and the material carrier 5 are arranged in the reactor shell, the insulation layer 1 is located on the upper part of the heater 2, the heater 2 is located on the upper part of the material carrier 5, the two ends of the material carrier 5 are connected to the feed port 3 and the discharge port 4 respectively, the heater 2 and the insulation layer 1 are arranged in the reactor shell from the feed port to the discharge port in the entire length direction, The number of reciprocating motors and crankshafts 6 is equal to that of material carriers 5. Each material carrier 5 is independently connected to a reciprocating motor through a crankshaft. The reciprocating motor is preferably variable frequency. One end of the fixed support rod 7 and the lifting support rod 8 is connected to the side of the reactor shell near the discharge port, and the other end is connected to the base 9. One end of the other is connected to the side of the reactor shell near the feed port, and the other end is connected to the base 9. When the sintering reactor of the present invention is used, the material (such as calcined particles) is input into the material carrier from the feed port, and the heater heats to generate high-temperature gas. The material reacts with the high-temperature gas on the material carrier while flowing toward the discharge port. The reaction is complete at the discharge port to obtain the target product (such as positive electrode material). The thermal field temperature (sintering temperature) of the material carrier is preferably 800-1200°C, for example 900±50°C. In the embodiment using the precursor as the core in the granulation section, the sintering temperature is preferably 920±20°C. In the embodiment using the cathode material single crystal particles as the core in the granulation section, the sintering temperature is preferably 870±20°C. In some embodiments, the sintering reactor further includes a feed bin and a conveying device, and the feed bin is connected to the feed port through the conveying device. The conveying device can be a screw. When using the sintering reactor, feed the material into the bin, start the reciprocating motor, and adjust the amplitude and vibration frequency. The material is transported to the first-stage material carrier by a conveying device (e.g., a screw), and then the material is transferred from the first-stage material carrier to the lower material carrier. The material undergoes a sintering reaction during the transfer process. In a preferred embodiment, the particle size of the cathode material of the present invention is in the range of 3000-8000 nm, for example, in the range of 3500-8000 nm, 4000-4500 nm, and the particle size is distributed in a narrow area, showing good particle size consistency. The chemical composition, tap density, specific surface area and other qualities of the cathode material of the present invention also show good consistency, and the variance of the element quality fraction (for example, for the nickel-chromium-manganese ternary cathode material, including Ni quality fraction, Co quality fraction, Mn quality fraction, Li quality fraction), tap density, and specific surface area can be controlled within 2%, preferably within 1.5%. The cathode material of the present invention also has improved initial discharge capacity and first coulomb efficiency. Compared with the existing technology, the present invention has the following characteristics: 1. The present invention adopts one or more coating calcination granulation methods, which can realize particle size control and improve particle density. The particle size of the finished powder can be controlled during the granulation process, and the particle size concentration is high; 2. The present invention adopts dynamic sintering, which has a wide range of requirements for powder particle size and can realize the dynamic sintering of low-strength powder and ultrafine powder; 3. The present invention avoids particle fusion by vibrating the material carrier, and realizes dynamic sintering and continuous transmission of materials; 4. The present invention obtains dense spherical powders through granulation, and can adjust the inclination and vibration frequency of the material carrier by measuring the material repose angle to ensure that the material is transmitted at a certain speed, realizing continuous production without the need for a sack; 5. The present invention does not need to go through a pulverization process after the sintering reaction or can significantly weaken the pulverization process to reduce losses; 6. The preparation method of the present invention can improve the consistency of the quality (chemical composition, tap density, specific surface area) of the positive electrode material, make the particle size of the positive electrode material distributed in a narrow area, and improve the initial discharge capacity and first coulombic efficiency of the positive electrode material. The following is a detailed description of the present invention in conjunction with specific embodiments, which does not limit the scope of protection of the present invention. The scope of protection of the present invention is limited only by the claims, and any omissions, substitutions or modifications made by technical personnel in this field on the basis of the embodiments disclosed in the present invention will fall within the scope of protection of the present invention. Unless otherwise specified, the instruments and equipment used in the following examples are conventional instruments and equipment in this field. The experimental methods in the following examples that do not specify specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercially available products, unless otherwise specified, and their specifications are the specifications commonly used in this field. Example 1: Granulation: The oxide precursor Ni _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.3μm, the maximum particle size is 3.2μm) is placed in a spray fusion machine, and the hydroxide precursor Ni _0.8 Co _0.1 Mn _0.1 (OH) with a particle size of 150nm is placed in a spray fusion machine. ₂ was mixed with the crushed LiOH to form a mixed solution (concentration of 2.5wt%, solvent is water), and the mixed solution was pumped into the centrifugal spray nozzle by a peristaltic pump, mixed and coated with the oxide precursor, the stirring device in the fusion machine was turned on, the stirring speed was 1200rpm, the heating device in the fusion machine was turned on, the temperature was raised to 500℃, and kept warm for 1 hour. After removing the water, the gas was cooled to 60℃, and the particle size D50 was sampled and tested to be 2.8μm. The mixed solution was pumped into the centrifugal spray nozzle again, and the spray fusion operation was repeated twice, and the increment of the particle size D50 after each spray fusion was controlled to be 0.7μm. Finally, the powder particle size D50 was measured to be 4.2μm, reaching the target particle size of the process design. Under the electron microscope, the particle size was uniform, the particles did not stick to the wall, and the fluidity was good. Sintering: The calcined particles were sintered using the sintering reactor shown in Figure 3. The sintering reactor includes a reactor shell, an insulation layer 1, a heater 2, a feed port 3, a discharge port 4, 12 material carriers 5 connected in series (only 7 are shown in Figure 3), 12 reciprocating motors and crankshafts 6 (only 7 are shown in Figure 3), a fixed support rod 7, a lifting support rod 8, a base 9, a feed bin (not shown in Figure 3) and a screw (not shown in Figure 3). The feed port 3 and the discharge port 4 are arranged at the two ends of the reactor shell, the insulation layer 1, the heater 2 and the material carrier 5 are arranged in the reactor shell, the insulation layer 1 is located on the upper part of the heater 2, the heater 2 is located on the upper part of the material carrier 5, the two ends of the material carrier 5 are connected to the feed port 3 and the discharge port 4 respectively, the heater 2 and the insulation layer 1 are arranged in the reactor shell from the feed port to the discharge port. In the length direction, each material carrier 5 is independently connected to a reciprocating motor through a crankshaft. The reciprocating motor is preferably a variable frequency type. One end of the fixed support rod 7 is connected to the side of the reactor shell near the discharge port, and the other end is connected to the base 9. One end of the lifting support rod 8 is connected to the side of the reactor shell near the feed port, and the other end is connected to the base 9. The feed bin is connected to the feed port through a screw. The repose angle of the particles after calcination is measured to be 67°, and the inclination angle of each material carrier in the sintering reactor is adjusted to an angle of 65° with the horizontal. There are 12 vibrating carriers inside the sintering reactor. The heater is turned on, and the thermal field temperature of material carriers No. 4-9 is 920℃. After the temperature rises to the reaction temperature, the calcined particles are put into the feed bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the primary material carrier by a screw. The vibration frequency and amplitude are adjusted. After 5 hours, the material begins to be discharged from the discharge port. The products of five time periods were subjected to the following tests: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 0.8%, Co mass fraction variance was 1.5%, Mn mass fraction variance was 1.5%, and Li mass fraction variance was 0.5%; (2) The particle size was measured by scanning electron microscope (SEM). Ten different areas were selected for measurement. The results showed that the particle size was distributed in a narrow area of 4000-4500 nm; (3) The tap density was measured. The results showed that the tap density variance was 1.5%; (4) The specific surface area was measured. The results showed that the specific surface area variance was 1.2%; (5) Measuring buckle charge (2.8-4.3V/0.1C). The test method is as follows: the positive electrode material, conductive agent SP and binder PVDF prepared in Example 1 are uniformly mixed at a mass ratio of 95:2.5:2.5, and then added to NMP to prepare a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil, dried, and rolled to obtain a positive electrode sheet with a compaction density of 3.52g/ ^cm3 ; then the buckle half-cell is assembled in an argon glove box, and its electrochemical properties are tested. The capacity and the first coulombic efficiency are tested at 0.1C charge and discharge in an environment of 25°C, and then a 1C charge and discharge cycle test is performed. The number of cycles is 50. The results show that the initial discharge capacity is 212 mAh/g, the first coulombic efficiency is 90%. Example 2: Granulation: Fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.5μm, the maximum particle size is 2.8μm) is put into a spray fusion machine, and the hydroxide precursor Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ with a particle size of 150nm is mixed with the crushed LiOH to form a solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump to mix with the fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Mixing and coating, turn on the stirring device in the fusion machine, the stirring speed is 1200rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and test the particle size D50 is 2.9μm. Pump the mixed solution into the centrifugal spray nozzle again, repeat the spray fusion operation twice, and control the particle size D50 increment after each spray fusion to be 0.75μm. Finally, the powder particle size D50 is measured to be 4.4μm, reaching the target particle size of the process design. Under the electron microscope, the particle size is uniform, the particles do not stick to the wall, and the fluidity is good. Sintering: Use the sintering reactor in Example 1 to sinter the calcined particles. The repose angle of the calcined particles is measured to be 68°, and the inclination angle of the material carrier in the sintering reactor is adjusted to 63° with the horizontal. There are 12 vibrating carriers inside the sintering reactor. Turn on the heater, and the thermal field temperature of material carriers No. 4-9 is 870°C. After the temperature rises to the reaction temperature, the calcined particles are put into the feed bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the primary material carrier by a screw. The vibration frequency and amplitude are adjusted. After 3 hours, the material begins to be discharged from the discharge port. The products of five time periods were subjected to the following tests: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP), and the results showed that the variance of Ni mass fraction was 0.9%, Co mass fraction variance was 1.3%, Mn mass fraction variance was 1.4%, and Li mass fraction variance was 0.5%; (2) The particle size was measured by scanning electron microscope (SEM), and 10 different areas were selected for measurement. The results showed that the particle size was distributed in a narrow area of 4200~4500nm; (3) The tap density was measured, and the results showed that the tap density variance was 1.5%; (4) The specific surface area was measured, and the results showed that the specific surface area variance was 1.2%; (5) Measuring the discharge capacity (2.8-4.3V/0.1C), the test method is the same as that of Example 1, wherein the compaction density is 3.51g/ ^cm3 , the results show that the initial discharge capacity is 195 mAh/g, and the first coulombic efficiency is 90.5%. Example 3: Granulation: Fine powder single crystal LiNi _0.88 Co _0.09 Al _0.03 O ₂ (particle size D50 is 3.8μm, the maximum particle size is 4.3μm) is placed in a spray fusion machine, and a hydroxide precursor Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ with a particle size of 50nm is mixed with the crushed LiOH to form a solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump to mix with the fine powder single crystal LiNi _0.88 Co _0.09 Al _0.03 O ₂ Mixing and coating, turn on the stirring device in the fusion machine, the stirring speed is 1200rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and detect the particle size D50 is 4.2μm. The process design target particle size is achieved, the particle size is uniform under the electron microscope, the particles do not stick to the wall, and the fluidity is good. Sintering: Use the sintering reactor in Example 1 to sinter the calcined particles. The repose angle of the calcined particles is measured to be 70°, and the inclination angle of the material carrier in the sintering reactor is adjusted to 65° with the horizontal. There are 12 vibrating platforms inside the sintering reactor. The heater is turned on, and the thermal field temperature of material platforms 4-9 is 870℃. After the temperature rises to the reaction temperature, the calcined particles are put into the feeding bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the first-level material platform by a screw. The vibration frequency and amplitude are adjusted. After 3 hours, the material begins to be discharged from the discharge port. The products of five time periods were subjected to the following tests: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 0.8%, Co mass fraction variance was 1.2%, Al mass fraction variance was 1.2%, and Li mass fraction variance was 0.6%. (2) The particle size was measured by scanning electron microscope (SEM). Ten different areas were selected for measurement. The results showed that the particle size was distributed in a narrow area of 3200-4500 nm. (3) The tap density was measured. The results showed that the tap density variance was 1.7%. (4) The specific surface area was measured. The results showed that the specific surface area variance was 1.5%. (5) Measuring the discharge capacity (2.8-4.3V/0.1C), the test method is the same as that of Example 1, wherein the compaction density is 2.47g/cm ³ , the results show that the initial discharge capacity is 203.5 mAh/g, and the first coulombic efficiency is 90.2%. Example 4: Granulation: Fine powder single crystal LiNi _0.9 Co _0.05 Mn _0.004 Al _0.01 O ₂ (particle size D50 is 3.4 μm, the maximum particle size is 3.9 μm) is placed in a spray fusion machine, and a hydroxide precursor Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ with a particle size of 30 nm is mixed with the crushed LiOH to form a solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump to mix with the fine powder single crystal LiNi _0.9 Co _0.05 Mn _0.004 Al _0.01 O ₂ Mixing and coating, turn on the stirring device in the fusion machine, the stirring speed is 1200rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and detect the particle size D50 is 3.7μm. The process design target particle size is achieved, the particle size is uniform under the electron microscope, the particles do not stick to the wall, and the fluidity is good. Sintering: Use the sintering reactor in Example 1 to sinter the calcined particles. The repose angle of the calcined particles is measured to be 71°, and the inclination angle of the material carrier in the sintering reactor is adjusted to 65° with the horizontal. There are 12 vibrating platforms inside the sintering reactor. The heater is turned on, and the thermal field temperature of material platforms 4-9 is 870℃. After the temperature rises to the reaction temperature, the calcined particles are put into the feeding bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the first-level material platform by a screw. The vibration frequency and amplitude are adjusted. After 3 hours, the material begins to be discharged from the discharge port. The products of five time periods were subjected to the following tests: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 0.6%, Co mass fraction variance was 1.1%, Mn mass fraction variance was 1.7%, Al mass fraction variance was 1.3%, and Li mass fraction variance was 0.4%. (2) The particle size was measured by scanning electron microscope (SEM). Ten different areas were selected for measurement. The results showed that the particle size was distributed in a narrow area of 3100-4100 nm. (3) The tap density was measured. The results showed that the tap density variance was 1.4%. (4) The specific surface area was measured. The results showed that the specific surface area variance was 1.3%. (5) Measuring the discharge capacity (2.8-4.3V/0.1C), the test method is the same as that of Example 1, wherein the compaction density is 2.45g/ ^cm3 , the results show that the initial discharge capacity is 212.5 mAh/g, and the first coulombic efficiency is 88.5%. Example 5: Granulation: Single crystal particles of LiNi _0.8 Co _0.1 Al _0.1 O ₂ (particle size D50 is 2.4 μm, the largest particle size is 2.6 μm) are placed in a spray fusion machine, carbonate precursor Ni _0.8 Co _0.1 Al _0.1 CO ₃ with a particle size of 150 nm is mixed with nano-LiOH to form a solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump and mixed with Ni _0.8 Co _0.1 Al _0.1 CO ₃ Mixing and coating, turn on the stirring device in the fusion machine, the stirring speed is 1200rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and test the particle size D50 is 2.8μm. Pump the mixed solution into the centrifugal spray nozzle again, repeat the spray fusion operation four times, and control the particle size D50 increment after each spray fusion to be 0.5μm. Finally, the powder particle size D50 is measured to be 4.8μm, reaching the target particle size of the process design. Under the electron microscope, the particle size is uniform, the particles do not stick to the wall, and the fluidity is good. Sintering: Use the sintering reactor in Example 1 to sinter the calcined particles. The repose angle of the calcined particles is measured to be 52°, and the inclination angle of the material carrier in the sintering reactor is adjusted to 45° with the horizontal. There are 12 vibrating carriers inside the sintering reactor. Turn on the heater, and the thermal field temperature of material carriers No. 4-9 is 870°C. After the temperature rises to the reaction temperature, the calcined particles are put into the feed bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the first-level material carrier by a screw. The vibration frequency and amplitude are adjusted. After 7 hours, the material begins to be discharged from the discharge port. The buckling charge (2.8-4.3V/0.1C) was measured using the same test method as in Example 1, wherein the compaction density was 3.51g/cm ³ . The results showed that the initial discharge capacity was 203 mAh/g and the first coulombic efficiency was 89.5%. Example 6: Granulation: Fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.5 μm, maximum particle size is 2.8 μm) is placed in a spray fusion machine, and a hydroxide precursor Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ with a particle size of 150 nm is mixed with the crushed LiOH to form a mixed solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump to mix with the fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ Mixing and coating, turn on the stirring device in the fusion machine, the stirring speed is 1200rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and test the particle size D50 is 2.9μm. Pump the mixed solution into the centrifugal spray nozzle again, repeat the spray fusion operation twice, and control the particle size D50 increment after each spray fusion to be 0.75μm. Finally, the powder particle size D50 is measured to be 4.4μm, reaching the target particle size of the process design. Under the electron microscope, the particle size is uniform, the particles do not stick to the wall, and the fluidity is good. Sintering: Put the coated granulated material into a ceramic sack, enter into an oxygen atmosphere furnace, and heat to 870°C at 10°C/min under pure oxygen conditions. Sinter for 5 hours. After the reaction is completed, cool the material and pass it through an 800-mesh screen to obtain the positive electrode material. The products at five points were tested as follows: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 0.8%, Co mass fraction variance was 1.3%, Mn mass fraction variance was 1.4%, and Li mass fraction variance was 0.5%; (2) The particle size was measured by scanning electron microscope (SEM). Five different areas were selected for measurement. The results showed that the particle size was distributed in the range of 1.8-18 μm; (3) The tap density was measured. The results showed that the tap density variance was 2.5%; (4) The specific surface area was measured. The results showed that the specific surface area variance was 3.2%; (5) Measure the charge-off voltage (2.8-4.3V/0.1C), the test method is the same as that of Example 1, wherein the compacted density is 3.45g/ ^cm3 , the result shows that the initial discharge capacity is 192 mAh/g, and the first coulombic efficiency is 87.5%. Example 7: Granulation: The oxide precursor Ni _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.3μm, the maximum particle size is 3.2μm) is put into a spray fusion machine, and the hydroxide precursor Ni _0.8 Co _0.1 Mn _0.1 (OH) with a particle size of 150nm is put into a spray fusion machine. ₂ was mixed with the crushed LiOH to form a mixed solution (concentration of 2.5wt%, solvent is water), and the mixed solution was pumped into the centrifugal spray nozzle by a peristaltic pump, mixed and coated with the oxide precursor, the stirring device in the fusion machine was turned on, the stirring speed was 1200rpm, the heating device in the fusion machine was turned on, the temperature was raised to 500℃, and kept warm for 1 hour. After dehydration, the gas was cooled to 60℃, and the particle size D50 was 2.8μm for sampling and detection. A hydroxide precursor Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ with a particle size of 150 nm was mixed with crushed LiOH to form a mixed solution (concentration of 7.5wt%, solvent is water), and the mixed solution was pumped into a centrifugal spray nozzle by a peristaltic pump, and the particles obtained by the previous coating and calcination were sprayed and fused again, and the particle size D50 increment was controlled to be 1.4μm. Finally, the powder particle size D50 was measured to be 4.2μm. Under an electron microscope, the particles contained ultrafine nanoparticles with low particle strength and easy to break. It is inferred that they are particles formed by the coating material itself. Sintering: The calcined particles were sintered using the sintering reactor in Example 1. The repose angle of the calcined particles is determined to be 75°, and the inclination angle of the material carrier in the sintering reactor is adjusted to 70° with the horizontal. There are 12 vibrating carriers inside the sintering reactor. The heater is turned on, and the thermal field temperature of material carriers No. 4-9 is 920℃. After the temperature rises to the reaction temperature, the calcined particles are put into the feed bin of the sintering reactor, the reciprocating motor is turned on, and the calcined particles are transported to the first-level material carrier by a screw. The vibration frequency and amplitude are adjusted. After 10 hours, the material begins to be discharged from the discharge port. The products at five points were tested as follows: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 2.1%, Co mass fraction variance was 2.1%, Mn mass fraction variance was 2.5%, and Li mass fraction variance was 3.7%. (2) The particle size was measured by scanning electron microscope (SEM). Five different areas were selected for measurement. The results showed that the particle size was distributed in the range of 1 to 13 μm. (3) The tap density was measured. The results showed that the tap density variance was 4.5%. (4) The specific surface area was measured. The results showed that the specific surface area variance was 3.2%. (5) The discharge capacity (2.8-4.3V/0.1C) was measured by the same test method as in Example 1, wherein the compacted density was 3.32g/cm ³ , and the results showed that the initial discharge capacity was 195 mAh/g and the first coulombic efficiency was 86.5%. Comparative Example 1: The hydroxide precursor Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ and LiOH were added into a high-speed mixer at a molar ratio of 1:1.05, and mixed thoroughly and evenly for 2 hours. The mixture was then placed into a ceramic jar and placed into an oxygen atmosphere furnace. Under pure oxygen conditions, the temperature was raised to 550°C at 10°C/min, kept at this temperature for 1 hour, and then raised to 920°C at 5°C/min, kept at this temperature for 9 hours, and sintered. After the reaction was completed, the mixture was cooled. After taking out, the material was crushed and screened to obtain a calcined product with a D50 particle size of 4.2μm and a yield of 90%. 0.3wt% of coating agent (a mixture of Ni _0.8 Co _0.1 Mn _0.1 (OH) ₂ and LiOH) was added to the calcined product, fully mixed with a high-speed mixer, put into a ceramic sack, and put into an oxygen atmosphere furnace. Under pure oxygen conditions, the temperature was raised to 920℃ at 10℃/min and calcined for 10 hours. After the reaction was completed, the material was cooled and passed through an 800-mesh screen to obtain a positive electrode material. The products at five points were tested as follows: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 0.9%, Co mass fraction variance was 2.1%, Mn mass fraction variance was 1.8%, and Li mass fraction variance was 1.5%. (2) The particle size was measured by scanning electron microscope (SEM). Five different areas were selected for measurement. The results showed that the particle size was distributed in the range of 1.3-18 μm. (3) The tap density was measured. The results showed that the tap density variance was 2.5%. (4) The specific surface area was measured. The results showed that the specific surface area variance was 3.2%. (5) Measuring the discharge capacity (2.8-4.3V/0.1C), the test method is the same as that of Example 1, wherein the compaction density is 3.35g/ ^cm3 , the results show that the initial discharge capacity is 201 mAh/g, and the first coulombic efficiency is 88.5%. Comparative Example 2: Granulation: Fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.5μm, maximum particle size is 2.8μm) is placed in a spray fusion machine, and a hydroxide precursor Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ with a particle size of 150nm is mixed with the crushed LiOH to form a solution (concentration is 2.5wt%, solvent is water), and the mixed solution is pumped into a centrifugal spray nozzle by a peristaltic pump to mix with the fine powder single crystal LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (particle size D50 is 2.5μm, the largest particle is 2.8μm) mixed coating, turn on the stirring device in the fusion machine, the stirring speed is 800rpm, turn on the heating device in the fusion machine, the temperature rises to 500℃, keep warm for 1 hour, remove moisture, cool the gas to 60℃, sample and detect the particle size D50 is 4.4μm. Under the electron microscope, the particles contain ultrafine particles and have poor fluidity. Sintering: Put the coated and granulated materials into a ceramic sack, enter the oxygen atmosphere furnace, under pure oxygen conditions, heat to 870℃ at 10℃/min, sinter for 10 hours, cool the materials after the reaction, pass through an 800-mesh screen, and obtain the positive electrode material. The products at five points were tested as follows: (1) The chemical composition was measured by inductively coupled plasma spectrometer (ICP). The results showed that the variance of Ni mass fraction was 1.8%, Co mass fraction variance was 2.1%, Mn mass fraction variance was 2.2%, and Li mass fraction variance was 2.2%; (2) The particle size was measured by scanning electron microscope (SEM). Five different areas were selected for measurement. The results showed that the particle size was distributed in the range of 1.8-19 μm; (3) The tap density was measured. The results showed that the tap density variance was 3.8%; (4) The specific surface area was measured. The results showed that the specific surface area variance was 4.1%; (5) The buckling charge (2.8-4.3V/0.1C) was measured by the same test method as in Example 1, wherein the compacted density was 3.41g/cm ³ , and the results showed that the initial discharge capacity was 188 mAh/g, and the first coulombic efficiency was 87%. The cathode materials prepared in Example 1 and Comparative Example 1 have a core-shell structure with similar components. It can be seen from the experimental results of Example 1 and Comparative Example 1 that the preparation method of the present invention can make the prepared cathode materials have higher consistency in quality such as chemical composition, tap density, specific surface area, etc., narrower particle size distribution, a more orderly layered structure, and better initial discharge capacity and first coulombic efficiency. By comparing the results of Example 1 and Example 7, it can be seen that controlling the thickness of a single coating and avoiding excessive thickness of a single coating is beneficial to improving the uniformity of the positive electrode material (consistency of chemical composition, particle size, tap density, and specific surface area) and improving electrical performance. By comparing the results of Example 2 and Example 6, it can be seen that the use of the sintering reactor of the present invention can improve the uniformity of the positive electrode material (consistency of particle size, tap density, and specific surface area) and improve electrical performance. By comparing Example 6 and Comparative Example 2, it can be seen that the use of the granulation process of multiple coating and calcination of the present invention can improve the uniformity of the positive electrode material (consistency of chemical composition, particle size, tap density, and specific surface area) and improve electrical performance.

1: Insulation layer 2: Heater 3: Inlet 4: Outlet 5: Material carrier 6: Reciprocating motor and crankshaft 7: Fixed support rod 8: Lifting support rod 9: Base

[Figure 1] is a schematic diagram of the granulation process of the present invention. [Figure 2] is a comparative schematic diagram of the granulation technology in some embodiments of the present invention and the prior art. [Figure 3] is a structural schematic diagram of a sintering reactor of the present invention. In Figure 3, 1 is a heat preservation layer, 2 is a heater, 3 is a feed port, 4 is a discharge port, 5 is a material carrier, 6 is a reciprocating motor and a crankshaft, 7 is a fixed support rod, 8 is a lifting support rod, and 9 is a base.

Claims (10)

A sintering reactor for preparing positive electrode materials, wherein the sintering reactor includes a reactor shell, a heater, a feed port, a discharge port and at least two serially connected material carriers, the feed port and the discharge port are located at two ends of the reactor shell, the heater and the material carrier are located inside the reactor shell, the heater is used to heat the material, the at least two serially connected material carriers are used to transport the material from the feed port to the discharge port, and the material carrier can vibrate. The sintering reactor as described in claim 1, wherein the sintering reactor has one or more of the following features: the material carrier can be subjected to variable frequency vibration; the material carrier has an angle of 40-75° with the horizontal plane, or there is no tilt angle between the material carrier and the horizontal plane; the number of the material carriers is 3-20; the sintering reactor also includes a reciprocating motor and a crankshaft, the crankshaft connecting the reciprocating motor and the material carrier; the sintering reactor also includes a lifting support rod, the lifting support rod is connected to the reactor shell; the sintering reactor also includes a heat preservation layer, the heat preservation layer is arranged above the heater. A cathode material preparation system, wherein the cathode material preparation system comprises a granulation device and a sintering reactor as described in claim 1 or 2. A method for preparing a positive electrode material, wherein the method includes preparing the positive electrode material using the sintering reactor described in claim 1 or 2 or the positive electrode material preparation system described in claim 3. A method for preparing a semi-finished cathode material, wherein the method comprises a granulation step, wherein the granulation step comprises: coating a lithium hydroxide precursor and/or a lithium carbonate precursor on Li _1+i M _1-i O _2+m , MO _2+m , and Li ₂ O and MO _2+m , wherein M is one or more selected from nickel, cobalt, manganese, aluminum, iron and titanium, i is 0-0.2, m is 0-1, to obtain coated particles, calcining the coated particles to convert the lithium hydroxide precursor and/or the lithium carbonate precursor on the surface of the coated particles into the lithium oxide precursor to obtain calcined particles, and if the calcined particles are If the calcined particles do not reach the target particle size, the surface of the calcined particles is again coated with a lithium hydroxide precursor and/or a lithium carbonate precursor, and then calcined until the calcined particles reach the target particle size; the lithium hydroxide precursor is a complex or mixture of a lithium salt and a transition metal hydroxide, and the lithium carbonate precursor is a complex or mixture of a lithium salt and a transition metal carbonate. The preparation method as described in claim 5, wherein the preparation method has one or more of the following characteristics: the particle size of one or more of Li _1+i M _1-i O _2+m , MO _2+m , and a mixture of Li ₂ O and MO _2+m to be coated is 1.5-6 μm; the particle size of the lithium hydroxide precursor and/or the lithium carbonate precursor as the coating agent is 20-250 nm; two or more coatings and calcinations are performed during the coating process; each coating and calcination increases the particle size of the particles by 0.3-0.9 μm; The coating and calcination are carried out by spray fusion; the stirring speed during fusion is 1200±200rpm, the heating temperature is 500±50℃, and the heating time is 1±0.2 hours; the concentration of the dispersion of the lithium hydroxide precursor and/or the lithium carbonate precursor used for spraying is 1-10wt%; the target particle size of the particles after calcination is 3.5-8μm; and the lithium hydroxide precursor is used for coating. A method for preparing a positive electrode material, wherein the method comprises a granulation step and a sintering step, the granulation step is as described in claim 5 or 6, and the sintering step comprises: sintering the calcined particles with a target particle size obtained in the granulation step; the sintering temperature is 800-1200°C. The preparation method as described in claim 7, wherein in the sintering step, the sintering is performed using the sintering reactor described in claim 1 or 2. A semi-finished positive electrode material particle, wherein the semi-finished positive electrode material particle is a calcined particle with a target particle size prepared by the preparation method described in claim 5 or 6; the particle size of the semi-finished positive electrode material particle is 3.5-8μm. A cathode material prepared by the preparation method described in claim 7 or 8, wherein the particle size of the cathode material ranges from 3500 to 8000 nm; the cathode material is a cathode material with a core-shell structure or a cathode material without a core-shell structure, the core layer material and the shell layer material of the cathode material with a core-shell structure are independently a ternary nickel-cobalt-manganese cathode material, a ternary nickel-cobalt-aluminum cathode material or a quaternary nickel-cobalt-manganese-aluminum cathode material, and the cathode material without a core-shell structure is a ternary nickel-cobalt-manganese cathode material, a ternary nickel-cobalt-aluminum cathode material or a quaternary nickel-cobalt-manganese-aluminum cathode material.