Process for preparing lithium manganate by high-temperature solid-phase method

Abstract

The invention discloses a process for preparing lithium manganate by a high-temperature solid-phase method, which comprises the following steps: S1, mixing a manganese source, a lithium source, an additive and grinding balls together, and carrying out mixed material ball milling, so that the materials are uniformly mixed; s2, the materials obtained after ball milling are loaded into a sagger, the materials in the sagger are punched through a puncher to form soaking holes, and the heating uniformity of the materials is improved; s3, the saggar loaded with the material punched by the puncher is fed into a kiln for gradient sintering; and S4, crushing and sieving the sintered material to obtain a lithium manganate finished product. The arrangement of the soaking holes formed by punching the material through the puncher can effectively increase the contact area between the material and the atmosphere and heating energy in the kiln, promote the heat conduction rate and heating uniformity in the material, and improve the uniformity of chemical reaction, phase formation and microstructure of the material, thereby improving the comprehensive performance of the lithium manganate material.

Description

A process for preparing lithium manganese oxide by high-temperature solid-state method Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a process for preparing lithium manganese oxide by a high-temperature solid-state method. Background Technology

[0002] In the field of lithium battery technology, lithium manganese oxide (LiMn2O4) has become an important cathode material for lithium batteries and energy storage due to its low cost, high safety, and environmental friendliness. As a cathode material for lithium-ion batteries, the preparation method of lithium manganese oxide directly affects the material's crystal structure, particle morphology, electrochemical performance, and stability.

[0003] In existing technologies, the main preparation methods for lithium manganese oxide include high-temperature solid-state methods, sol-gel methods, co-precipitation methods, and hydrothermal / solvothermal methods. Among these, the high-temperature solid-state method is commonly used in the industrial production of lithium manganese oxide due to its relatively simple process and ease of industrialization. The high-temperature solid-state method generally includes the processes of mixing and grinding, sintering, and pulverizing and sieving. The essence of solid-state reactions is the diffusion and migration of atoms in the solid state. This process is strongly dependent on temperature. If the sintering temperature is too low, the reaction will be incomplete; if the temperature is too high, the grains will be too large, the specific surface area will decrease, and lithium volatilization will be severe, leading to a decrease in capacity. Under uniform temperature conditions, the reaction in each region can be ensured to start simultaneously and proceed at similar rates. The formation, transformation, and growth of phases occur synchronously throughout the material, avoiding local deviations from the designed formulation. The uniformity of material heating directly determines the uniformity of chemical reactions, phase formation, and microstructure, which is the physical basis for obtaining high-performance, highly consistent, and high-yield products. Uneven heating of materials can also lead to the existence of over-reacted and under-reacted portions within the same batch of material, resulting in significant differences in product performance within the batch.

[0004] During sintering, the mixed raw materials need to be loaded into a sagger and placed in a kiln for sintering. Due to the resistance to mass transfer in solid-phase reactions, in order to ensure uniform temperature and consistent reaction of the raw materials in the sagger during sintering, the existing technology generally increases the uniformity of heating of the materials by reducing the thickness of the materials loaded in the sagger. This not only limits production efficiency, but also causes local overheating and instability of the raw materials in the sagger due to accumulation. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature solid-state method for preparing lithium manganese oxide, which ensures uniform heating of the material in the crucible and improves the uniformity of the material's chemical reaction, phase formation, and microstructure.

[0006] To solve the above-mentioned technical problems, the embodiments of the present invention provide a technical solution as follows: A process for preparing lithium manganese oxide by high-temperature solid-state method, comprising the following steps: S1: mixing manganese source, lithium source, additives and grinding balls together and performing ball milling to make the materials uniformly mixed; S2: loading the ball-milled material into a sagger, and punching the material in the sagger with a punch to form heat-equalizing holes, thereby increasing the uniformity of material heating; S3: sending the sagger containing the punched material into a kiln for gradient sintering; S4: crushing and sieving the sintered material to obtain the finished lithium manganese oxide product; wherein, the sagger is a box structure with one open end, the sagger has a cavity for loading materials, the punch is axially corresponding to the sagger, and multiple top posts are provided facing the open end of the sagger, driving the punch to move closer to the sagger, and the top posts punch the material in the cavity of the sagger to form multiple heat-equalizing holes. The process of preparing lithium manganese oxide is simplified by mixing and grinding the materials in a single step, which can effectively improve the production efficiency of lithium manganese oxide preparation. The setting of forming heat-equalizing holes by punching the materials in the sagger can effectively increase the contact area between the materials and the atmosphere and heating energy in the kiln, promote the rate of heat conduction and heating uniformity inside the materials, and improve the uniformity of chemical reaction, phase formation and microstructure of the materials. The setting of gradient sintering controls grain growth and optimizes crystallinity, so that the sintering of materials is more complete and uniform, and avoids segregation of dopant elements caused by excessively rapid heating.

[0007] Furthermore, in step S1, the manganese source and the lithium source are mixed in a Li / Mn molar ratio of 0.51 to 0.54. The manganese source is manganese dioxide or manganese tetroxide, the lithium source is lithium carbonate, and the additives are aluminum oxide, niobium oxide, and lithium fluoride. Through the optimization of the Li / Mn molar ratio and the synergistic effect of the additives, structural degradation during cycling can be reduced, and cycling stability can be improved.

[0008] Furthermore, the materials are quantified in the following molar ratio: manganese tetroxide: lithium carbonate: aluminum oxide: niobium pentoxide: lithium fluoride = 21.85: (16.88~17.70): (0.4~0.5): (0.06~0.08): (0.6~0.8). By precisely setting the material ratio, manganese dissolution and Jahn-Teller distortion during the preparation of lithium manganese oxide can be effectively controlled, optimizing the crystal structure stability of lithium manganese oxide and thus improving the overall performance of lithium manganese oxide as a cathode material.

[0009] Furthermore, the grinding balls include various sizes of balls, specifically large balls with a diameter of 30±2mm, medium balls with a diameter of 20±2mm, and small balls with a diameter of 15±2mm. The weight ratio of the three types of balls is: large balls: medium balls: small balls = 3:2:1. By setting the ratio of grinding balls with different diameters, the ball milling efficiency can be improved, the particle size distribution of the material can be increased, and the uniformity of material mixing can be effectively improved.

[0010] Furthermore, in step S3, the gradient sintering process involves heating to 400-500℃ at a rate of 3-5℃ / min and holding for 1-3 hours, then heating to 600-650℃ at a rate of 3-5℃ / min and holding for 1-3 hours, and finally heating to 740-760℃ at a rate of 3-5℃ / min and holding for 10-15 hours. By controlling the heating rate and holding time in the gradient sintering process, grain growth is controlled, crystallinity is optimized, and the sintering of the material is more thorough and uniform. This avoids excessively rapid heating that could lead to segregation of dopant elements, which is beneficial for improving the performance of lithium manganese oxide as a cathode material.

[0011] Furthermore, in step S2, the sagger cavity has a rectangular cross-section, the punch includes a base plate, and the top posts are vertically disposed on the plane of the base plate. The free ends of the top posts face the opening end of the cavity and are arranged in a matrix. The punch punches the material inside the sagger, forming matrix-arranged heat-equalizing holes on the material corresponding to the top posts. The matrix arrangement of the top posts increases the uniformity of the heat-equalizing holes in the material, thereby improving the heating rate and uniformity of the material.

[0012] Further, in step S2, the punch includes a substrate and a top post and a cutting plate vertically disposed on the same side of the substrate. The cutting plate includes two intersecting cutting plates intersecting the central axis of the punch and a central surrounding plate disposed coaxially. Multiple top posts are provided between the intersecting cutting plates and the central surrounding plate. The punch punches the material in the sagger so that heat-spreading holes corresponding to the top posts and cutting lines corresponding to the cutting plates are formed on the material. By setting up cross-cutting plates and a central surrounding plate in the cutting plate, as well as a top column between the cross-cutting plates and the central surrounding plate, the puncher can press the material to form corresponding cutting lines and heat-spreading holes. This not only further increases the contact area between the material and the kiln atmosphere and heating energy, promoting the uniformity of material heating and the rate of heat conduction, but also effectively guides the stress distribution of the material, reduces the overall strength of the sintered material, and makes the material easier to break along the cutting path when the bowl is turned over, greatly reducing the risk of material blockage. This facilitates the subsequent crushing of the sintered material and avoids jamming or overload when the rotary mill crushes the material. It is beneficial to improve the operating efficiency of lithium manganese oxide preparation, save energy and reduce consumption, and reduce the production cost of lithium manganese oxide.

[0013] Furthermore, the sagger cavity has a square cross-section, and the axial projection of the cross-cutting plate onto the sagger cavity is the diagonal of the square cross-section of the cavity. The central surrounding plate has a closed annular cross-section, and the cross-cutting plate divides the area enclosed by the central surrounding plate into four equal regions, each region having four top pillars. By using the cross-cutting plate's axial projection onto the sagger cavity as the diagonal of the square cross-section of the cavity, the material cutting line length can be effectively increased, further enhancing the uniformity of material heating.

[0014] Furthermore, a branch cutting plate extends from the intersection of the central surrounding plate and the cross-cutting plate away from the central axis of the punch, and at least one top post is provided between adjacent cross-cutting plates, central surrounding plates, and branch cutting plates. Through the optimized arrangement of the cross-cutting plates, central surrounding plates, branch cutting plates, and top posts, the uneven heating caused by material accumulation is reduced, which can further increase the material loading thickness inside the crucible, improve the production capacity of a single crucible, and thus effectively improve the production efficiency of lithium manganese oxide preparation and reduce production costs.

[0015] Furthermore, the top post has a conical structure or a conical tip, with the pointed end being a free end. By making the free end of the top post a pointed end, the resistance when the top post presses the material can be reduced, the frictional loss on the top post can be reduced, and the stability of the heat-equalizing hole formation can be improved. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0017] Figure 1 is a process flow diagram of the high-temperature solid-state method for preparing lithium manganese oxide in an embodiment of the present invention; Figure 2 is a schematic diagram of the sagger structure in an embodiment of the present invention; Figure 3 is a schematic diagram of the sagger structure loaded with materials in an embodiment of the present invention; Figure 4 is a three-dimensional schematic diagram of the punch in an embodiment of the present invention; Figure 5 is a bottom view of the punch in an embodiment of the present invention; Figure 6 is a three-dimensional schematic diagram of the punch in different embodiments of the present invention; Figure 7 is a schematic diagram of the sagger and punch separated in an embodiment of the present invention; Figure 8 is a schematic diagram of the sagger and punch combined in an embodiment of the present invention; Figure 9 is a schematic diagram of the punch separated from the sagger material after punching in an embodiment of the present invention; Figure 10 is a schematic diagram of the structure of the material inside the sagger after punching in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached drawings: 10, sagger; 11, cavity; 20, material; 201, slit line; 202, heat spreader hole; 30, punch; 31, substrate; 32, top post; 33, cutting plate; 331, cross-cutting plate; 332, central enclosure plate; 333, branch cutting plate. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0020] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0021] As shown in Figure 1, one embodiment of the present invention relates to a process for preparing lithium manganese oxide by a high-temperature solid-state method, comprising the following steps: S1: Mixing manganese source, lithium source, additives, and grinding balls together and performing ball milling to ensure uniform mixing of the materials; the manganese source and the lithium source are mixed in a Li / Mn molar ratio of 0.51 to 0.54, the manganese source is manganese dioxide or manganese tetroxide, the lithium source is lithium carbonate, and the additives are aluminum oxide, niobium oxide, and lithium fluoride. The grinding balls used in the ball mill include large balls, medium balls, and small balls. The diameter of the large balls is 30±2 mm, the diameter of the medium balls is 20±2 mm, and the diameter of the small balls is 15±2 mm. The weight ratio of the three types of grinding balls is: large balls: medium balls: small balls = 3:2:1. Preferably, the grinding balls are zirconia balls or polyurethane balls. During the mixing ball milling process, the powerful impact of large balls breaks up agglomerates and coarse particles, while the dense friction of small balls achieves fine grinding and uniform dispersion. The medium-sized balls perform energy transfer and filling optimization. The three work synergistically to achieve the best mixing effect. This combination can achieve the required mixing uniformity and particle size requirements faster than single-size ball milling, shortening the ball milling time and improving the ball milling efficiency. In particular, for the dispersion of trace additives, the dense friction of small balls makes the material composition highly uniform, increasing the uniformity of material mixing.

[0022] S2: The ball-milled material 20 is loaded into the sagger 10. A punch 30 is used to punch the material 20 inside the sagger 10 to form heat-spreading holes 202, increasing the uniformity of heating of the material 20. As shown in Figure 2-10, the sagger 10 is a box structure with one open end. The sagger 10 has a cavity 11 for loading the material 20. The punch 30 is axially aligned with the sagger 10, and multiple top posts 32 are provided facing the open end of the sagger 10. By moving the punch 30 axially relative to the sagger 10, the top posts 32 can punch the material 20 inside the cavity 11, forming heat-spreading holes 202 on the material 20 that penetrate its surface and interior.

[0023] S3: The sagger 10 containing the punched material 20 is fed into the kiln for gradient sintering; in one example, the gradient sintering is to heat to 400-500℃ at a rate of 3-5℃ / min and hold for 1-3 hours, then heat to 600-650℃ at a rate of 3-5℃ / min and hold for 1-3 hours, and finally heat to 740-760℃ at a rate of 3-5℃ / min and hold for 10-15 hours.

[0024] S4: The sintered material 20 is crushed and sieved to obtain the finished lithium manganese oxide. The sintered material 20 is cooled to room temperature with the furnace, and then crushed using a rotary mill. The material 20 after being processed by the rotary mill is sieved through an 80-200 mesh screen to obtain the finished lithium manganese oxide.

[0025] After ball milling, the material 20 is spread evenly inside the cavity 11 of the sagger 10. Heat transfer proceeds from the surface inwards. The material 20 piled inside the sagger 10 is prone to uneven heating during heating, leading to differences in reaction rates among the materials 20 within the sagger 10. This significantly affects the consistency of the phase transformation of the material 20, resulting in reduced performance and poor performance consistency of the finished lithium manganese oxide product. The high-temperature solid-state method for preparing lithium manganese oxide provided by this invention simplifies the process by performing a single mixing and grinding of the material 20. The use of a punch 30 to create heating holes 202 in the material 20 within the sagger 10 effectively increases the contact area between the material 20 and the kiln atmosphere and heating energy, promoting uniform heating and heat conduction rate, and improving the uniformity of chemical reactions, phase formation, and microstructure. The gradient sintering setting controls grain growth and optimizes crystallinity, resulting in more thorough and uniform sintering of the material and preventing segregation of dopant elements caused by excessively rapid heating.

[0026] As shown in Figure 6, one embodiment relates to a process for preparing lithium manganese oxide by a high-temperature solid-state method. In step S2, the sagger 10 is a box structure with one open end. The cavity 11 surrounding its peripheral wall has a rectangular cross-section. The punch 30 includes a planar substrate 31. Multiple top posts 32 are vertically arranged on the same side of the substrate 31. In use, the punch 30 is axially aligned with the sagger 10. The free end of the top post 32 faces the open end of the sagger 10. The punch 30 is driven to move closer to the sagger 10, so that the top post 32 punches the material 20 in the cavity 11 of the sagger 10 to form multiple heat-spreading holes 202. Preferably, the top posts 32 of the punch 30 are arranged in a matrix. The punch 30 punches the material 20 inside the sagger 10, forming heat-spreading holes 202 on the material 20 in a matrix arrangement corresponding to the top posts 32. The top posts 32 are conical structures or have conical tips, with the sharp end being a free end. By setting the free end to a sharp end, the resistance of the top posts 32 punching the material 20 is reduced, the frictional wear on the top posts 32 is reduced, and the stability of the heat-spreading holes 202 formation is also improved. In one example, the sagger 10 is a cube, and the cross-section of its cavity 11 is square. The top posts 32 of the punch 30 are arranged in a square matrix on the substrate 31.

[0027] As shown in Figures 4-5 and 7-10, one embodiment relates to a process for preparing lithium manganese oxide by a high-temperature solid-state method. In step S2, the punch 30 includes a planar substrate 31. A top post 32 and a cutting plate 33 are vertically arranged on the same side of the planar surface of the substrate 31. The punch 30 is axially corresponding to the sagger 10. The top post 32 and the cutting plate 33 are distributed within the cross-sectional area corresponding to the cavity 11 of the sagger 10. Thus, when the punch 30 is driven to move toward the sagger 10, the cutting plate 33 and the top post 32 can respectively punch the material 20 in the cavity 11 of the sagger 10 to form a cutting line 201 corresponding to the cutting plate 33 and a heat-spreading hole 202 corresponding to the top post 32. Preferably, the top post 32 is a conical structure or has a conical tip, and its sharp end is a free end. The cutting plate 33 includes intersecting cross-cutting plates 331 and a central surrounding plate 332. The cross-cutting plates 331 are thin plates that are vertically fixed to the plane of the substrate 31 by the central axis of the punch 30, and there are at least two of them. The planes of the two cross-cutting plates 331 intersect, and their intersection line coincides with the central axis of the punch 30. The central surrounding plate 332 is formed by the thin plates and is symmetrically arranged with the central axis of the punch 30 as the central axis. The cross section of the central surrounding plate 332 is a closed annular structure. Branch cutting plates 333 extend from the intersection line of the central surrounding plate 332 and the cross-cutting plates 331 away from the central axis. Multiple top posts 32 are provided between adjacent cross-cutting plates 331 and central surrounding plates 332. The specific directional cleaving line 201 formed by the baffle pressing the material 20 not only further increases the contact area between the material 20 and the atmosphere and heating energy in the kiln, promoting the uniformity of heating of the material 20 and the rate of heat conduction, but also effectively guides the stress distribution of the material 20, reduces the overall strength of the material 20 after sintering, and makes it easier for the material 20 to break along the cleaving line 201 path when the bowl is turned over, greatly reducing the risk of material blockage, and facilitating the subsequent crushing of the material 20 after sintering. This avoids jamming or overload when the rotary mill crushes the material 20, which is conducive to improving the operating efficiency of lithium manganese oxide preparation and saving energy and reducing consumption.

[0028] In one example, the cross-section of the cavity 11 of the sagger 10 is square, and the punch 30 is axially aligned with the sagger 10. The cross-cutting plate 331 consists of two thin plates perpendicularly intersecting each other, and the axial projection of the cross-cutting plate 331 onto the cavity 11 of the sagger 10 is the diagonal of the square cross-section of the cavity 11. The cross-section of the central circumferential plate 332 is square, and the plane of the central circumferential plate 332 is perpendicular to the cross-cutting plate 331. Thus, the cross-cutting plate 331 divides the area enclosed by the central circumferential plate 332 into four equal regions. Each region is provided with multiple top posts 32. Preferably, each region has four top posts 32. Outside the area enclosed by the central circumferential plate 332, multiple top posts 32 are provided between the cross-cutting plate 331 and adjacent central circumferential plates 332. Preferably, outside the area enclosed by the central circumferential plate 332, two top posts 32 are provided between the cross-cutting plate 331 and adjacent central circumferential plates 332.

[0029] One embodiment relates to a process for preparing lithium manganese oxide using a high-temperature solid-state method. In step S2, the cutting plate 33 includes a cross-cutting plate 331, a central surrounding plate 332, and branch cutting plates 333 arranged in a cross configuration. The cross-cutting plate 331 is a thin plate that is perpendicularly fixed to the plane of the substrate 31 by the central axis of the punch 30, and at least two cross-cutting plates 331 are provided. The planes of the two cross-cutting plates 331 intersect, and their intersection line coincides with the central axis of the punch 30. The central surrounding plate 332 is formed by a thin plate and is symmetrically arranged about the central axis of the punch 30. The cross-section of the central surrounding plate 332 is a closed annular structure. The branch cutting plate 333 extends from the intersection line of the central surrounding plate 332 and the cross-cutting plate 331 away from the central axis. At least one top post 32 is provided between adjacent cross-cutting plates 331, central surrounding plates 332, and branch cutting plates 333.

[0030] In one example, the sagger 10 cavity 11 has a square cross-section, and the punch 30 is axially aligned with the sagger 10. The cross-cutting plate 331 consists of two thin plates perpendicularly intersecting each other, and the axial projection of the cross-cutting plate 331 onto the sagger 10 cavity 11 is the diagonal of the square cross-section of the cavity 11. The central circumferential plate 332 has a square cross-section, and the plane of the central circumferential plate 332 is perpendicular to the cross-cutting plate 331, thus dividing the area enclosed by the central circumferential plate 332 into four equal regions, each region having multiple top posts 32; preferably, each region has four top posts 32. Outside the area enclosed by the central circumferential plate 332, a branch cutting plate 333 is centrally located between adjacent central circumferential plates 332 and cross-cutting plates 331, and each branch cutting plate 333 has at least one top post 32 between it and an adjacent central circumferential plate 332 or cross-cutting plate 331. By optimizing the arrangement of the cross-cutting plate 331, the central surrounding plate 332, the branch cutting plate 333, and the top column 32, the uniformity of heating of the material 20 is improved through the cleaving line 201 and the heat equalization hole 202, reducing the uneven heating caused by the accumulation of material 20. This can further increase the loading thickness of material 20 in the sagger 10, increase the production capacity of a single sagger 10, and thus effectively improve the production efficiency of lithium manganese oxide preparation and reduce production costs.

[0031] One embodiment involves a high-temperature solid-state method for preparing lithium manganese oxide, wherein the manganese source and the lithium source are mixed in a Li / Mn molar ratio of 0.51 to 0.54, the manganese source is manganese dioxide or manganese tetroxide, the lithium source is lithium carbonate, and the additives are aluminum oxide, niobium oxide, and lithium fluoride. Preferably, the material ratio is manganese tetroxide: lithium carbonate: aluminum oxide: niobium pentoxide: lithium fluoride = 21.85: (16.88-17.70): (0.4-0.5): (0.06-0.08): (0.6-0.8). Through the synergistic effect of the three additives—alumina, niobium pentoxide, and lithium fluoride—the crystal structure stability of lithium manganese oxide is optimized, manganese dissolution and Jahn-Teller distortion are suppressed, structural degradation during cycling is reduced, and cycling stability is improved; that is, through the doping of aluminum oxide, aluminum ions replace Mn. 3+ Ions, reducing Mn 3+ It triggers a significant spontaneous disproportionation reaction, increasing Li +The process improves transport rate and prevents SEI (solid-state electrolyte interface) damage. Coating with lithium niobate and lithium fluoride avoids direct contact with hydrofluoric acid, reducing side reactions at the cathode-electrolyte interface. Soluble LiF alters the chemical equilibrium of the reaction, controlling the reaction direction and limiting the formation of HF and POF3. Therefore, the liquid electrolyte LiPF6 may undergo less oxidative decomposition, resulting in less HF corrosion of the LiMn2O4 cathode. Doping with niobium oxide increases the average oxidation state of manganese to +3.5 or higher, suppressing the Jahn-Teller effect and providing a larger MO bond energy (M represents the metal's oxidation state), enhancing crystal structure stability. The interaction between these additives and electrolytic manganese dioxide and lithium carbonate significantly suppresses structural distortion in lithium manganese oxide, reduces structural degradation during cycling, and improves cycling stability.

[0032] In one example, the preparation and effect verification of lithium manganese oxide according to the high-temperature solid-state method provided by the present invention are as follows: First, the manganese source, lithium source, additives, and grinding balls are mixed together and ball-milled for 3 hours to ensure uniform mixing. Zirconia grinding balls are used, including large, medium, and small balls. The diameter of the large balls is 30±2 mm, the medium balls are 20±2 mm, and the small balls are 15±2 mm. The weight ratio of the three types of grinding balls is: large balls: medium balls: small balls = 3:2:1. The material composition for lithium manganese oxide preparation of samples 1-8 is shown in Table 1, the primary mixing batching table: Table 1 Primary Mixing Batching Table

[0033] Secondly, the ball-milled material 20 is loaded into the sagger 10, and the material 20 inside the sagger 10 is punched by the puncher 30 to form heat-spreading holes 202, so as to increase the heat uniformity of the material 20. Preferably, the puncher 30 is provided with a partition and a top column 32 corresponding to the cavity 11 of the sagger 10. By punching the material 20 inside the sagger 10 with the partition and the top column 32, the cutting line 201 and the heat-spreading hole 202 are formed on the material 20. The processing of the cutting line 201 and the heat-spreading hole 202 can not only effectively increase the contact area between the material 20 and the atmosphere and heat in the kiln, and increase the efficiency and uniformity of heat conduction in the material 20, but also reduce the difficulty of crushing the material 20 after sintering by the cutting line 201, improve the production efficiency of lithium manganese oxide, save energy and reduce consumption, and reduce costs.

[0034] Next, after the material 20 in the sagger 10 is processed by the cutting line 201 and the heat soaking hole 202, it is sequentially sent into the kiln for gradient sintering. The gradient sintering is to heat up to 450℃ at a rate of 4℃ / min and hold for 2 hours, then heat up to 620℃ at a rate of 4℃ / min and hold for 2 hours, and finally heat up to 750℃ at a rate of 4℃ / min and hold for 12 hours.

[0035] Finally, the material after gradient sintering is cooled to room temperature with the furnace, and the material exiting the furnace is crushed using a rotary mill. The material after being processed by the rotary mill is screened through an 80-mesh sieve. The material on the sieve is collected once per hour. The unscreened material is fed back into the rotary mill for secondary crushing, and then screened through a 200-mesh sieve to remove iron, packaged, and obtain the finished lithium manganese oxide product.

[0036] The obtained lithium manganese oxide product was tested for physical and electrochemical properties. The main physical property test results are shown in Table 2. The lithium manganese oxide was assembled into a button cell and its electrochemical performance was tested. The electrochemical performance test results at 25℃ are shown in Table 3 - 25℃ button cell cycle performance test record, and the electrochemical performance test results at 45℃ are shown in Table 4 - 45℃ button cell cycle performance test record.

[0037] Table 2 Physical Performance Test Record Sheet

[0038] As shown in Table 2, the tap density of the lithium manganese oxide finished material provided by this invention is ≥1.88 g / cm³. 3 Specific surface area less than 0.56m² 2 / g, D50 particle size is concentrated in 6~11μm, with good particle size concentration, and all indicators meet industry standards.

[0039] Table 3. 25℃ Button Cycle Performance Test Record Sheet

[0040] As can be seen from the data in Table 3, the lithium manganese oxide provided by this invention, as a positive electrode material, exhibits excellent electrochemical performance under coin cell testing at room temperature (25°C), with a 0.1C discharge capacity and a 1C discharge capacity greater than 117 mAh / g, and a capacity decay rate of less than 0.40% after 100 cycles of 1C / 1C cycling.

[0041] Table 4. 45℃ Button Cycle Performance Test Record

[0042] As shown in Table 4, the lithium manganese oxide provided by this invention, when used as a positive electrode material in a high-temperature 45°C coin cell test, exhibits a 0.2C discharge capacity greater than 116 mAh / g, a 1C discharge capacity greater than 117 mAh / g, and a 1C / 1C 100-cycle charge-discharge decay rate of less than 1.70%, demonstrating excellent electrochemical performance.

[0043] Table 5: Ratio Test Results

[0044] As shown in Table 5, the lithium manganese oxide prepared in this invention, when used as the cathode material in the battery, exhibits excellent rate performance. The capacity retention rate is greater than 99.6% at 5C / 0.5C and greater than 84.3% at 10C / 0.5C.

[0045] Based on the physicochemical performance test data of the above samples, the lithium manganese oxide prepared according to the high-temperature solid-phase method provided by this invention has a concentrated particle size, exhibits good cycle performance at 25℃ and 45℃, excellent rate performance, high performance consistency, and overall good product performance.

[0046] The high-temperature solid-state method for preparing lithium manganese oxide provided by this invention simplifies the preparation process by mixing and grinding the materials in a single step. The use of a punch to create uniform heating holes in the sagger effectively increases the contact area between the material and the kiln atmosphere and heating energy, promoting uniform heating and heat transfer, and improving the uniformity of chemical reactions, phase formation, and microstructure. Furthermore, the gradient sintering process controls grain growth and optimizes crystallinity, resulting in more thorough and uniform sintering and preventing segregation of dopant elements caused by excessively rapid heating. In particular, the specific path cut formed by the material being pressed by the cutting plate not only further increases the contact area between the material and the kiln atmosphere and heating energy, promoting the uniformity of material heating and the rate of heat conduction, but also effectively guides the stress distribution of the material, reduces the overall strength of the sintered material, and makes the material easier to break along the cutting path when the crucible is turned over, greatly reducing the risk of material blockage and facilitating the subsequent crushing of the sintered material. Through the optimized setting of cross-cutting plates, central surrounding plates, branch cutting plates, and top columns, the uneven heating caused by material accumulation is reduced, which can further increase the material loading thickness in the crucible, increase the production capacity of a single crucible, and improve the continuity and stability of the production process, thereby effectively improving the production efficiency of lithium manganese oxide preparation and reducing production costs.

[0047] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A process for preparing lithium manganese oxide via a high-temperature solid-state method, characterized in that, Includes the following steps: S1: Mix the manganese source, lithium source, additives, and grinding balls together and ball mill them to ensure uniform mixing; S2: Load the ball-milled material (20) into a sagger (10), and punch the material (20) in the sagger (10) with a punch (30) to form heat-dissipating holes (202), thereby increasing the uniformity of heating inside the material (20); S3: Send the sagger (10) containing the punched material (20) into a kiln for gradient sintering; S4: Crush and sieve the sintered material (20). Obtain lithium manganese oxide finished product; wherein, the sagger (10) is a box structure with one end open, the sagger (10) is provided with a cavity (11) for loading material (20), the punch (30) is axially corresponding to the sagger (10), and a plurality of top posts (32) are provided facing the opening end of the sagger (10), driving the punch (30) to move closer to the sagger (10), and the top posts (32) punch the material (20) in the cavity (11) of the sagger (10) to form a plurality of heat-equalizing holes (202).

2. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 1, characterized in that, In step S1, the manganese source and the lithium source are mixed in a Li / Mn molar ratio of 0.51 to 0.

54. The manganese source is manganese dioxide or manganese tetroxide, the lithium source is lithium carbonate, and the additives are aluminum oxide, niobium oxide, and lithium fluoride.

3. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 2, characterized in that, The materials are measured and mixed in the following molar ratio: manganese tetroxide: lithium carbonate: aluminum oxide: niobium pentoxide: lithium fluoride = 21.85: (16.88~17.70): (0.4~0.5): (0.06~0.08): (0.6~0.8).

4. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 1, characterized in that, The grinding balls include various sizes of balls, including large balls with a diameter of 30±2mm, medium balls with a diameter of 20±2mm, and small balls with a diameter of 15±2mm. The weight ratio of the three types of balls is: large ball: medium ball: small ball = 3:2:

1.

5. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 1, characterized in that, In step S3, the gradient sintering process involves heating to 400-500°C at a rate of 3-5°C / min and holding for 1-3 hours, then heating to 600-650°C at a rate of 3-5°C / min and holding for 1-3 hours, and finally heating to 740-760°C at a rate of 3-5°C / min and holding for 10-15 hours.

6. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 1, characterized in that, In step S2, the cross-section of the cavity (11) of the sagger (10) is rectangular, the punch (30) includes a base plate (31), the top post (32) is vertically disposed on the plane of the base plate (31), the free end of the top post (32) is disposed facing the opening end of the cavity (11) and arranged in a matrix, and the punch (30) punches the material (20) in the sagger (10) so that heat dissipation holes (202) corresponding to the top post (32) are formed on the material (20).

7. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 1, characterized in that, In step S2, the punch (30) includes a substrate (31) and a top post (32) and a cutting plate (33) vertically disposed on the same side of the substrate (31). The cutting plate (33) includes two intersecting cutting plates (331) intersecting the central axis of the punch (30) and a central surrounding plate (332) coaxially disposed. Multiple top posts (32) are provided between the intersecting cutting plates (331) and the central surrounding plate (332). The punch (30) punches the material (20) in the sagger (10) so that heat-spreading holes (202) corresponding to the top posts (32) and cutting lines (201) corresponding to the cutting plate (33) are formed on the material (20).

8. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 7, characterized in that, The cross-section of the sagger (10) cavity (11) is square, and the axial projection of the cross-cutting plate (331) on the sagger (10) cavity (11) is the diagonal of the square cross-section of the cavity (11); the cross-section of the central enclosure plate (332) is a closed annular structure, and the cross-cutting plate (331) divides the area enclosed by the central enclosure plate (332) into four equal areas, each area having four top pillars (32).

9. The process for preparing lithium manganese oxide by high-temperature solid-state method according to claim 7, characterized in that, A branch cutting plate (333) extends from the intersection of the central enclosure plate (332) and the cross cutting plate (331) away from the central axis of the punch (30), and at least one top post (32) is provided between adjacent cross cutting plates (331), central enclosure plate (332) and branch cutting plates (333).

10. The process for preparing lithium manganese oxide by high-temperature solid-state method according to any one of claims 1-9, characterized in that, The top column (32) is a conical structure or has a conical tip, the sharp end of which is a free end.

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