A spherical or near-spherical manganese tetroxide, its preparation method and application

Abstract

This invention discloses a spherical or near-spherical manganese tetroxide, its preparation method, and its application. A composite additive is prepared by compounding an amino acid-type buffer component with a polyamino acid-type complexing dispersion component. This composite additive is then added to a manganese salt base solution prepared from soluble manganese salts to form a weakly complexing dispersion reaction system. The system is heated to 55–80°C, and ammonia and an oxidizing gas are added concurrently under stirring. An oxidation precipitation reaction is carried out using staged pH control. After the reaction, a weak alkali ripening process is performed, followed by solid-liquid separation and post-processing to obtain spherical or near-spherical manganese tetroxide powder. The method of this invention solves the problems of large local pH fluctuations and Mn content issues in the existing one-step oxidation method of manganese sulfate for preparing manganese tetroxide. 2+ Problems include difficulty in controlling the hydrolysis precipitation rate, severe homogeneous explosive nucleation, obvious particle aggregation, insufficient sphericity, and low tap density.

Description

Technical Field

[0001] This invention belongs to the field of battery cathode material technology, and relates to manganese tetroxide, its preparation method and application, and particularly to a method for preparing high tap density spherical or near-spherical manganese tetroxide based on an integrated amino acid-polyamino acid buffer dispersion system. Background Technology

[0002] Manganese tetroxide (MTO) is an important manganese source precursor for the preparation of lithium manganese oxide, lithium nickel manganese oxide, and other manganese-based cathode materials. When used as a battery-grade precursor, MTO not only needs high chemical purity and a stable spinel crystal phase, but also requires suitable particle size, a narrow particle size distribution, a low specific surface area, and a high tap density. These powder characteristics directly affect the uniformity of subsequent mixing with the lithium source, the uniformity of the sintering reaction, compaction performance, and electrochemical performance.

[0003] Existing routes for preparing manganese tetroxide mainly include the oxidation of metallic manganese, the precipitation oxidation of manganese salts, the thermal decomposition of manganese carbonate or manganese oxalate, and hydrothermal or solvothermal methods. Among these, the one-step oxidation of manganese sulfate has advantages such as a wide availability of raw materials, a relatively short process, and suitability for continuous and scale-up preparation, making it an important route for the preparation of battery-grade manganese tetroxide precursors. However, this route typically involves Mn... 2+ The coupling of multiple processes such as hydrolysis, precipitation, oxidation and crystal transformation, as well as the system pH, oxidation rate, local supersaturation and interparticle interactions, can significantly affect the morphology and tap density of the product.

[0004] In the traditional one-step oxidation process of manganese sulfate, a localized high pH region is easily generated near the ammonia addition point, leading to the instantaneous formation of Mn(OH)2 or basic manganese salts. Uneven mass transfer of the oxidizing gas also causes differences in oxidation rates across different regions, inducing a large number of fine crystal nuclei, platy or needle-like impurities, and soft agglomerates. If nucleation is too rapid, the product particle size is small and the specific surface area increases; if particle dispersion is insufficient, loose aggregates easily form between particles, resulting in a low tap density. Therefore, it is usually difficult to simultaneously achieve crystal phase purity, sphericity, narrow particle size distribution, and high tap density by adjusting only a single pH value, stirring speed, or oxygen flow rate.

[0005] Existing publicly available technologies include methods for controlling the morphology and reaction pH of manganese tetroxide using surfactants, polymer dispersants, or buffer systems. For example, some techniques induce crystal growth on specific crystal faces using surfactants such as sodium dodecylbenzenesulfonate or polyethylene glycol, or adjust the reaction pH using systems such as ammonia-ammonium chloride, citrate, or tartrate. These methods improve morphology or pH stability to some extent, but they are mostly single-function controls: dispersants primarily address particle aggregation, and buffers mainly control the system pH; there is a lack of specific control over Mn. 2+The coupled design of the entire process of hydrolysis, oxidation nucleation, crystal growth and particle densification.

[0006] Especially in the preparation of battery-grade high-tap-density spherical manganese tetroxide, simply using buffers and dispersants together is insufficient to address the underlying mechanisms of problems such as localized supersaturation, explosive homogeneous nucleation, fine powder formation, inter-crystal agglomeration, and surface porosity. Therefore, it is necessary to provide a novel composite regulation strategy that differs from traditional surfactants or inorganic buffer systems, enabling the additive to not only possess pH buffering and particle dispersing properties but also to regulate Mn through weak complexation. 2+ The effective concentration is controlled by seed induction to regulate the nucleation path, by segmented oxidation to regulate the oxidation precipitation rate, and by weak alkali ripening to achieve particle surface densification, thereby obtaining spherical or near-spherical manganese tetroxide powder that is more suitable for use as a battery precursor. Summary of the Invention

[0007] To overcome the problems in existing technologies, this invention provides a spherical or near-spherical manganese tetroxide, its preparation method, and its application, solving the problems of large local pH fluctuations and Mn content issues in the existing one-step oxidation method of manganese sulfate for preparing manganese tetroxide. 2+ Problems include difficulty in controlling the hydrolysis precipitation rate, severe homogeneous explosive nucleation, obvious particle agglomeration, insufficient sphericity, and low tap density.

[0008] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0009] This invention provides a method for preparing spherical or near-spherical manganese tetroxide, characterized by comprising the following steps: S1. The amino acid buffer component and the polyamino acid complex dispersion component are compounded to obtain a composite additive, which is then added to the manganese salt bottom liquid prepared from soluble manganese salt and stirred to form a weak complex dispersion reaction system. S2. The reaction system obtained in step S1 is heated to 55-80°C, and ammonia water and oxidizing gas are added in parallel under stirring. The oxidation precipitation reaction is carried out by staged pH control. After the reactions in S3 and S2 are completed, the mixture is subjected to weak alkali ripening, followed by solid-liquid separation and processing to obtain spherical or near-spherical manganese tetroxide powder.

[0010] In this invention, an amino acid-type buffer component is pre-compounded with a polyamino acid-type complex dispersion component to obtain an integrated buffer-dispersion composite additive, which is then added to a manganese salt base solution. The amino acid-type buffer component is used to stabilize the pH of the system and adjust the Mn content. 2+ Hydrolysis precipitation rate, polyamino acid complex dispersion components for Mn 2+ The nascent manganese tetroxide particles undergo weak complexation, surface adsorption, and spatial dispersion, which synergistically achieve pH stabilization and Mn content reduction. 2+Slow-release, crystal nucleation regulation, and particle dispersion. Before adding ammonia and oxidizing gas, Mn... 2+ It forms a weakly complexed pre-dispersion system with the amino and carboxyl groups of amino acids and the polycarboxyl segments of polyamino acids. This step can reduce free Mn. 2+ The instantaneous effective concentration slows down the subsequent hydrolysis and precipitation rate, and inhibits local supersaturation and explosive nucleation.

[0011] As an optional implementation, in the preparation method provided by the present invention, in S1, the amino acid buffer component is selected from one or more of glycine, β-alanine, lysine, arginine, histidine, glutamic acid, aspartic acid, or water-soluble salts of the above amino acids.

[0012] Glycine and / or β-alanine are preferred.

[0013] As an optional implementation, in the preparation method provided by the present invention, in S1, the polyamino acid complex dispersion component is selected from one or more of polyaspartic acid, sodium polyaspartate, polyglutamic acid, sodium polyglutamate, or water-soluble derivatives of the above-mentioned polyamino acids.

[0014] Polyaspartic acid is preferred.

[0015] As an optional implementation, in the preparation method provided by the present invention, in S1, the mass ratio of the amino acid type buffer component to the polyamino acid type complex dispersion component is 5:1 to 1:5.

[0016] The ratio is preferably 3:1 to 1:3, and more preferably 2:1 to 1:2.

[0017] As an optional implementation, in the preparation method provided by the present invention, the amino acid-type buffer component is β-alanine, the polyamino acid-type complex dispersion component is sodium polyaspartate, and the mass ratio of β-alanine to sodium polyaspartate is 1:2 to 2:1, preferably 1:2, 1.5:1 or 2:1, so as to ensure that the buffer module stabilizes the pH while the dispersion module effectively prevents particle agglomeration and promotes spheroidization.

[0018] As an optional implementation method, in the preparation method provided by the present invention, in S1, the amount of the composite additive added is 0.5 to 2.0 g / L, and the pH fluctuation, crystal sphericity and particle dispersion of the reaction system can be precisely controlled by adjusting the amount added.

[0019] As an optional implementation, in the preparation method provided by the present invention, in S1, the composite additive is added to the manganese salt base solution and stirred at 25-65°C for 10-90 min to achieve the reaction of Mn. 2+ Weak complexation pre-dispersion treatment of nascent manganese tetroxide particles.

[0020] It is preferable to stir at 30–60°C for 20–60 minutes.

[0021] As an optional implementation, in the preparation method provided by the present invention, in S2, ammonia water is added at a molar ratio of ammonia to manganese of 2.2:1 to 3.0:1, preferably 2.4:1 to 2.8:1, and staged pH regulation is achieved by segmented dropwise addition or pH feedback control, wherein: the pH is 8.0 to 8.6 in the crystal nucleation stage, the pH is 8.6 to 9.3 in the crystal growth stage, and the pH is 8.3 to 9.0 in the maturation stage, and the pH fluctuation is ≤ ±0.20.

[0022] In this invention, staged control allows for simultaneous nucleation and spherical crystal growth, suppressing local pH abrupt changes and crystal distortion, reducing particle agglomeration, and improving dispersibility. This results in spherical Mn3O4 precursors with high tap density and low specific surface area, significantly superior to traditional single-pH control systems. During any pH adjustment stage, the pH fluctuation range is controlled within ±0.20, preferably within ±0.10.

[0023] As an optional implementation method, in the preparation method provided by the present invention, the oxidizing gas in S2 is controlled in three stages, wherein the oxidizing gas flow rate in the low-oxygen nucleation stage is 0.05-0.20 L / min, the oxidizing gas flow rate in the high-oxygen growth stage is 0.20-0.60 L / min, and the oxidizing gas flow rate in the low-oxygen ripening stage is 0-0.20 L / min.

[0024] In this invention, the oxidizing gas flow rate during the low-oxygen nucleation stage is 0.05–0.20 L / min to reduce the oxidation precipitation rate and decrease homogeneous explosive nucleation; the oxidizing gas flow rate during the high-oxygen growth stage is 0.20–0.60 L / min to allow subsequent manganese oxides to preferentially deposit and grow on the surface of existing crystal nuclei or seeds; and the oxidizing gas flow rate during the low-oxygen ripening stage is 0–0.20 L / min to maintain crystal phase transformation and surface rearrangement.

[0025] As an optional implementation, in the preparation method provided by the present invention, in step S2, the oxidizing gas is selected from oxygen or an oxygen-containing mixed gas.

[0026] As an optional implementation, in the preparation method provided by the present invention, in S2, manganese tetroxide seed crystals are added before oxidation precipitation or at the initial stage of crystal nucleus formation. The D50 of the manganese tetroxide seed crystals is 0.1 to 5.0 μm, preferably 0.2 to 3.0 μm. The amount of seed crystals added is 0.01% to 5.0% based on the mass of manganese in the system, preferably 0.05% to 3.0%.

[0027] As an optional implementation method, in the preparation method provided by the present invention, the manganese tetroxide seed crystals are first contacted and dispersed with the buffer-dispersion integrated composite additive for 5 to 30 minutes before being added to the reaction system, so as to form an adsorption and dispersion layer containing amino acids and polyamino acids on the surface of the seed crystals.

[0028] As an optional implementation, in the preparation method provided by the present invention, in S3, the weak alkali ripening is carried out at pH 8.3-9.0 and 60-90℃ for 0.5-3 h, and stirred at a low speed of 100-400 rpm.

[0029] In this invention, the reaction is not filtered immediately after completion. Instead, the above-mentioned weak alkali ripening process is carried out to allow fine particles to be deposited a second time on the surface of the spherical parent particles and to undergo surface densification.

[0030] As an optional implementation, in the preparation method provided by the present invention, in step S3, the post-solid-liquid separation process includes washing and drying, washing until the pH of the filtrate is 6.5-8.0 and / or the conductivity is ≤100 μS / cm, and drying temperature is 60-120℃.

[0031] As an optional implementation method, in the preparation method provided by the present invention, the soluble manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate, and the concentration of manganese ions in the manganese salt bottom solution is 0.8 to 2.5 mol / L.

[0032] As an optional implementation method, in the preparation method provided by the present invention, the mechanical stirring speed is 300-900 rpm.

[0033] Based on the same technical concept, this invention also provides spherical or near-spherical manganese tetroxide prepared by the above-mentioned preparation method, wherein the manganese tetroxide is spinel structure Mn3O4 with a tap density ≥1.8 g / cm³. 3 Specific surface area ≤10 m² 2 / g.

[0034] As an optional implementation, in the spherical or near-spherical manganese tetroxide provided by the present invention, the manganese tetroxide powder has a D50 of 5.0 to 18.0 μm, a Span ≤ 1.20, and a manganese mass fraction of 60% to 72%.

[0035] Based on the same technical concept, the present invention also provides the application of the above-mentioned spherical or near-spherical manganese tetroxide in the preparation of precursors for lithium-ion battery cathode materials.

[0036] Mechanism of Action: In this invention, the amino acid-based buffer component can balance pH changes in the buffer system through protonation / deprotonation within a weakly alkaline reaction window, reducing local pH abrupt changes caused by the addition of ammonia. Simultaneously, the amino and carboxyl groups in the amino acid molecules can react with Mn... 2+ Weak coordination occurs, causing Mn 2+ It no longer participates in instantaneous hydrolysis precipitation entirely as free ions, but is uniformly dispersed in the base liquid in a weakly complexed state.

[0037] Polyamino acid-based dispersed complexes contain multiple carboxyl segments, which can target Mn. 2+ It generates multi-point weak complexes and can also adsorb onto the surface of primary Mn3O4 or intermediate manganese oxide particles, forming a hydration adsorption layer and a steric hindrance layer. This structure helps to suppress soft particle agglomeration, allowing subsequent deposits to preferentially grow uniformly on the surface of existing crystal nuclei or seeds, rather than forming a large number of independent fine powders.

[0038] When a small amount of Mn3O4 seed crystals are introduced, the seed crystals can act as heterogeneous nucleation centers, reducing the proportion of homogeneous nucleation. Three-stage oxidation control further matches the oxidation rates of the nucleation, growth, and maturation stages: low-oxygen nucleation reduces the disordered generation of fine nuclei, high-oxygen growth promotes epitaxial deposition and spheroidization of particles, and low-oxygen maturation combined with a weakly alkaline environment promotes surface rearrangement and densification. Thus, this invention can extend the "buffering-dispersion" process to a multi-level synergistic regulation of "buffering-weak complexation-seed induction-segmented oxidation-maturation densification."

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention employs an integrated amino acid-polyamino acid buffer-dispersion composite additive, which differs from traditional single surfactants such as SDBS, PEG, and DTAC, and single buffer systems such as ammonia-ammonium chloride, citrate, and tartrate. The amino acid module not only provides buffering under weakly alkaline conditions but also interacts with Mn through amino and carboxyl groups. 2+ Weak complexation occurs; polyamino acid modules provide complexation, adsorption, and spatial dispersion through multi-carboxyl segments, thereby achieving pH stability and Mn... 2+ Simultaneous regulation of sustained release and particle dispersion. Mn is introduced before oxidation precipitation. 2+ Weak complexation pre-dispersion treatment makes Mn² + It is uniformly distributed in the reaction system in a weak complexation manner, which reduces local supersaturation when ammonia is added, reduces the formation of instantaneous Mn(OH)2 precipitate, basic manganese salt or fine disordered crystal nuclei, and is conducive to the formation of stable and uniform crystal nucleus groups.

[0040] (2) The present invention can further introduce Mn3O4 seed crystals to induce oxidation deposition, so that the system changes from a large number of homogeneous burst nucleation to heterogeneous nucleation and epitaxial deposition growth centered on seed crystals; combined with the surface adsorption and dispersion effect of polyamino acids, it can reduce the agglomeration between seed crystals, promote the secondary growth of spherical particles and narrow the particle size distribution.

[0041] (3) The present invention adopts a three-stage oxidation control of low-oxygen nucleation, high-oxygen growth and low-oxygen ripening, so that the oxidation rate matches the nucleation, growth and ripening requirements of different stages, avoiding the problems of excessive fine powder under high oxygen conditions and incomplete reaction under low oxygen conditions.

[0042] (4) The present invention uses a weak alkali ripening-surface densification step to make fine particles deposited on the surface of spherical parent particles a second time and undergo surface rearrangement, thereby reducing the specific surface area and improving particle density and tap density.

[0043] (5) In this invention, an integrated composite additive with amino acid-polyamino acid buffering and dispersing properties is introduced to construct Mn before oxidation and precipitation. 2+ A weakly complexed pre-dispersion system, combined with staged pH control, seeding induction, three-stage oxidation, and weakly alkaline ripening and densification steps, was used to achieve the desired Mn concentration. 2+ Synergistic control of the entire process of hydrolysis, oxidation nucleation, crystal growth, particle dispersion and surface densification.

[0044] (6) The manganese tetroxide obtained in this invention is a spinel structure Mn3O4, with spherical or near-spherical particles and a tap density ≥1.8 g / cm³. 3 Specific surface area ≤10 m² 2 With a density of / g, D50 can be controlled between 5.0 and 18.0 μm, and Span ≤ 1.20, it is suitable as a precursor for lithium-ion battery cathode materials. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a process flow diagram for preparing manganese tetroxide in this invention; Figure 2 The amino acid-polyamino acid type buffer and dispersion integrated composite additive in this invention is effective for Mn 2+ Schematic diagram of the mechanism of weak complex pre-dispersion, seed induction and particle spheroidization growth; Figure 3This is a schematic diagram of the X-ray diffraction pattern of the manganese tetroxide powder obtained in Example 1 of the present invention; Figure 4 This is a scanning electron microscope morphology diagram of the manganese tetroxide powder obtained in Example 1 of the present invention; Figure 5 Figure 1 shows a comparison of the particle size distribution and tap density of manganese tetroxide obtained under different process systems. Figure 2 shows a comparison of particle size distribution and Figure 3 shows a comparison of tap density. Detailed Implementation

[0047] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0049] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0050] Example 1 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Weigh out manganese sulfate monohydrate, prepare 1 L of manganese sulfate solution with a manganese ion concentration of 1.5 mol / L, and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0051] (2) Glycine and sodium polyaspartate were premixed at a mass ratio of 2:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with an addition amount of 1.0 g / L.

[0052] (3) After adding the composite additive to the manganese sulfate base solution, stir at 40°C for 30 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0053] (4) Heat to 65℃, adjust the stirring speed to 600 rpm, and use staged pH control: pH 8.2-8.5 during the crystal nucleation stage and pH 8.7-9.1 during the crystal growth stage. Add ammonia water dropwise at a molar ratio of ammonia to manganese of 2.6:1, and introduce air at a rate of 0.30 L / min.

[0054] (5) After the reaction is complete, the mixture is stirred at low speed for 1 h at pH 8.6-8.8 and 70℃. Then it is filtered and washed until the conductivity of the filtrate is ≤90 μS / cm, and dried at 80℃ for 12 h to obtain manganese tetroxide.

[0055] The obtained product is spinel-structured Mn3O4, with nearly spherical particles, a D50 of approximately 10.8 μm, a Span of approximately 0.95, and a specific surface area of ​​approximately 7.8 m². 2 / g, tap density approximately 2.03 g / cm³ 3 .

[0056] Example 2 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 2 L of 1.5 mol / L manganese sulfate solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0057] (2) β-alanine and sodium polyaspartate were pre-combined at a mass ratio of 1:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with an addition amount of 1.2 g / L.

[0058] (3) After adding the composite additive to the manganese sulfate base solution, pre-stir at 45°C for 40 min to allow Mn to react. 2+ It forms a weakly complexed pre-dispersed state.

[0059] (3) Heat to 65℃, stir at 600 rpm, add ammonia water dropwise and introduce air. The oxidation process adopts a three-stage oxidation control: low-oxygen nucleation stage for 20 min, air introduction rate of 0.12 L / min, pH controlled at 8.2-8.5; high-oxygen growth stage for 120 min, air introduction rate of 0.40 L / min, pH controlled at 8.7-9.1; low-oxygen ripening stage for 60 min, air introduction rate of 0.10 L / min, pH controlled at 8.5-8.8.

[0060] (4) After the reaction is completed, stir at low speed for 1 h at pH 8.6-8.8 and 70℃, then filter and wash until the conductivity of the filtrate is ≤90 μS / cm, and dry at 80℃ for 12 h to obtain spherical or near-spherical manganese tetroxide powder.

[0061] XRD analysis of the obtained product showed a spinel-structured Mn3O4 main crystalline phase with no obvious MnO2, Mn2O3, or MnOOH impurity phases; D50 was approximately 11.5 μm, Span was approximately 0.90, and specific surface area was approximately 7.2 m². 2 / g, tap density approximately 2.08 g / cm³ 3 .

[0062] Example 3 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 1 L of 2.0 mol / L manganese sulfate solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0063] (2) Glycine, β-alanine and sodium polyaspartate were compounded in a mass ratio of 1:1:1 to prepare an integrated amino acid-polyamino acid buffer dispersion compound additive. The total amount of the compound additive added was 1.5 g / L.

[0064] (3) After adding the composite additive to the manganese sulfate base solution, add Mn3O4 seed crystals with a D50 of approximately 1.0 μm to the system. The amount of seed crystals added is 0.5% based on the mass of manganese. After the seed crystals are added, they are dispersed together with the composite additive for 15 min, and then pre-complexed at 45℃ for another 30 min to form Mn3O4. 2+ Weakly complexed pre-dispersed system.

[0065] (4) Heat to 68℃ and stir at 650 rpm. Use staged pH control: pH is controlled at 8.2 to 8.6 during the crystal nucleation stage, with an air flow rate of 0.10 L / min; pH is controlled at 8.8 to 9.2 during the crystal growth stage, with an air flow rate of 0.45 L / (min·L).

[0066] (4) After the reaction is complete, the solution is aged at pH 8.5-8.8 and 75℃ for 2 h, then filtered and washed until the conductivity of the filtrate is ≤90 μS / cm, and dried at 80℃ for 12 h to obtain manganese tetroxide.

[0067] The obtained product is a regular spherical shape with a relatively dense particle surface. The D50 is approximately 13.2 μm, the Span is approximately 0.82, and the specific surface area is approximately 6.6 m². 2 / g, tap density approximately 2.15 g / cm³ 3 .

[0068] Example 4 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 1 L of 1.2 mol / L manganese sulfate solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0069] (2) Glycine and sodium polyglutamate were compounded at a mass ratio of 2:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with an addition amount of 0.8 g / L.

[0070] (3) After adding the composite additive to the manganese sulfate base solution, pre-stir at 35°C for 25 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0071] (4) Then the temperature was raised to 62℃ and stirred at 550 rpm. The pH was controlled in stages: pH 8.1-8.5 during the first 30 min of crystal nucleation stage and pH 8.7-9.0 during the crystal growth stage. The ammonia water was mixed with manganese at a molar ratio of 2.5:1 and the air flow rate was 0.25 L / min.

[0072] (5) After the reaction is complete, the solution is aged at 65℃, pH 8.5~8.7 and 80℃ for 1 h, then filtered and washed until the conductivity of the filtrate is ≤90 μS / cm, and dried at 80℃ for 12 h to obtain manganese tetroxide.

[0073] The obtained manganese tetroxide was a near-spherical particle with a D50 of approximately 8.9 μm, a Span of approximately 1.02, and a specific surface area of ​​approximately 8.4 m². 2 / g. Tap density is approximately 1.96 g / cm³. 3 .

[0074] Example 5 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 1 L of 1.5 mol / L manganese chloride solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0075] (2) β-alanine and sodium polyaspartate were compounded at a mass ratio of 1.5:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with an addition amount of 1.0 g / L.

[0076] (3) After adding the composite additive to the manganese chloride base solution, pre-complex it at 40℃ for 30 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0077] (4) Then the temperature was raised to 66℃, the stirring speed was 600 rpm, and the pH was controlled in stages: the pH was 8.2 to 8.6 during the crystal nucleation stage and the pH was 8.7 to 9.1 during the crystal growth stage. Air was introduced and ammonia was added dropwise at a ratio of 2.6:1 (ammonia to manganese). The air introduction rate was 0.30 L / min.

[0078] (5) After the reaction is complete, the mixture is stirred at low speed for 1 h at pH 8.6-8.8 and 70℃. Then it is filtered and washed until the conductivity of the filtrate is ≤90 μS / cm, and dried at 80℃ for 12 h to obtain manganese tetroxide.

[0079] The obtained product is a Mn3O4 main crystalline phase, with nearly spherical particles and a tap density of approximately 1.98 g / cm³. 3 This indicates that the method is applicable not only to manganese sulfate systems but also to manganese chloride systems.

[0080] Example 6 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare a 1.5 mol / L manganese sulfate solution in a 100 L aeration device and pH monitoring device in a reaction vessel.

[0081] (2) Glycine and sodium polyaspartate were pre-combined at a mass ratio of 2:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion. The amount of composite additive added was 1.0 g / L.

[0082] (3) After adding the composite additive to the manganese sulfate base solution, pre-complex it at 40℃ for 40 min, then raise the temperature to 65℃ and use mechanical stirring and bottom aeration to carry out oxidation precipitation. The air flow rate is controlled at 0.10 L / min during the crystal nucleation stage, increased to 0.35 L / min during the growth stage, and decreased to 0.08 L / min during the ripening stage.

[0083] (4) The pH remained stable within the target window during the reaction, specifically, the pH was controlled at 8.0–8.6 during the nucleation stage, 8.6–9.3 during the crystal growth and spheroidization stage, and 8.3–9.0 during the ripening stage, with pH fluctuations not exceeding ±0.15 in any stage. After ripening at 70℃ with low-speed stirring for 1 h, the product was filtered, washed with deionized water until the conductivity of the filtrate was ≤90 μS / cm, and dried at 80℃ for 12 h. The resulting product showed good batch stability, with a tap density of approximately 2.01 g / cm³. 3 Specific surface area is approximately 7.9 m² 2 / g.

[0084] Example 7 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Weigh an appropriate amount of manganese sulfate monohydrate and prepare 1 L of 1.5 mol / L aqueous solution. Place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0085] (2) β-alanine and sodium polyaspartate were pre-combined at a mass ratio of 1:2 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with a total addition amount of 1.2 g / L.

[0086] (3) After adding the composite additive to the manganese sulfate base solution, pre-complex it at 40°C for 30 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0087] (4) The reaction system was then heated to 65°C and mechanically stirred at 600 rpm. Ammonia and oxidizing gas were added simultaneously in parallel flow. The molar ratio of ammonia to manganese was controlled at 2.4:1 to 2.8:1, and the air flow rate was 0.30 L / min. A staged pH control was adopted: pH 8.0 to 8.6 during the crystal nucleation stage, and pH 8.6 to 9.3 during the crystal growth and spheroidization stage.

[0088] (4) After the reaction is complete, the mixture is aged at low speed for 2 h at pH 8.6-8.9 and 70℃, filtered, washed with deionized water until the conductivity of the filtrate is ≤90 μS / cm, and dried at 90℃ for 12 h to obtain manganese tetroxide powder.

[0089] The resulting product is spherical or spherical in shape, with uniform particle size and a tap density of approximately 1.95 g / cm³. 3 Specific surface area is approximately 10 m² 2 / g.

[0090] Example 8 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 1 L of 1.5 mol / L manganese sulfate solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0091] (2) β-alanine and sodium polyaspartate were pre-blended at a mass ratio of 1.5:1 to prepare an integrated amino acid-polyamino acid buffer dispersion additive, with an addition amount of 1.2 g / L. (3) After adding the composite additive to the manganese sulfate base solution, pre-complex it at 40℃ for 30 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0092] (3) Heat to 65℃, stir at 600 rpm, and add ammonia and oxidizing gas at the same time. The molar ratio of ammonia to manganese is 2.4:1 to 2.8:1, and the air flow rate is 0.30 L / min. Staged pH control is carried out in conjunction with the dropwise addition of ammonia. The pH is 8.2 to 8.5 during the crystal nucleation stage and 8.8 to 9.1 during the crystal growth stage to ensure a stable crystal nucleation and spheroidization growth process.

[0093] (4) After the reaction is complete, the mixture is aged at low speed for 2 h at pH 8.4-8.8 and 70℃, filtered, washed with deionized water until the conductivity of the filtrate is ≤90 μS / cm, and dried at 70℃ for 12 h to obtain spherical manganese tetroxide powder.

[0094] The obtained product has high particle sphericity, narrow particle size distribution, and a tap density of approximately 2.02 g / cm³. 3 Specific surface area ≤9 m² 2 / g.

[0095] Example 9 The method for preparing manganese tetroxide in this embodiment is as follows: (1) Prepare 1 L of 1.5 mol / L manganese sulfate solution and place it in a reaction vessel equipped with mechanical stirring, aeration device and pH monitoring device.

[0096] (2) β-alanine and sodium polyaspartate were pre-combined at a mass ratio of 2:1 to prepare an integrated composite additive of amino acid-polyamino acid buffer dispersion, with an addition amount of 1.2 g / L.

[0097] (3) After adding the composite additive to the manganese sulfate base solution, pre-complex it at 40°C for 30 min to form Mn 2+ Weakly complexed pre-dispersed system.

[0098] (3) Heat to 65℃, stir at 600 rpm, and add ammonia water and oxidizing gas in parallel stream, with an ammonia-manganese ratio of 2.5:1 to 2.8:1. Stage-wise pH control is used, with the pH being 8.2 to 8.6 during the crystal nucleation stage and 8.7 to 9.1 during the crystal growth stage to ensure that crystal spheroidization occurs simultaneously.

[0099] (4) After the reaction is complete, the mixture is aged at low speed for 2 h at pH 8.6-8.8 and 70℃, filtered, washed with deionized water until the conductivity of the filtrate is ≤90 μS / cm, and dried at 80℃ for 12 h to obtain spherical manganese tetroxide powder.

[0100] The resulting product particles are spherical or near-spherical, with a tap density of approximately 2.05 g / cm³. 3 Specific surface area is approximately 9 m² 2 / g, with a concentrated particle size distribution.

[0101] Comparative Example 1 This comparative example is essentially the same as Example 1, except that glycine and sodium polyaspartate were not added. During the reaction, significant local pH fluctuations occurred, indicating a lack of buffering and dispersing effects. This led to rapid and disordered formation of crystal nuclei, severe particle agglomeration, an extremely wide particle size distribution (span significantly greater than 1.80), a significantly increased specific surface area, and a tap density of approximately 1.50 g / cm³. These results demonstrate that without amino acid buffering and polyamino acid dispersion-complexation, controllable growth of spherical, uniform particles cannot be achieved, resulting in a significant decrease in product quality.

[0102] Comparative Example 2 This comparative example is essentially the same as Example 1, except that only glycine is added, and sodium polyaspartate is not added. The pH remained relatively stable during the reaction, but due to the lack of surface adsorption and spatial dispersion of polyamino acid polycarboxyl segments, the resulting particles exhibited significant soft agglomeration, a wide particle size distribution (Span greater than 1.50), increased specific surface area, and a tap density of approximately 1.55 g / cm³. 3 This result indicates that amino acid buffering and weak complexation alone are insufficient to achieve the growth of highly dispersed spherical particles.

[0103] Comparative Example 3 This comparative example is essentially the same as Example 1, except that only sodium polyaspartate is added, and glycine is not added. During the reaction, local pH fluctuations occurred in the area where ammonia was added, easily leading to the formation of fine crystal nuclei and loose aggregates. Although the resulting product has some dispersibility, its sphericity is insufficient, with a high proportion of fine powder, and a tap density of approximately 1.62 g / cm³. 3 This result indicates that the polyamino acid dispersion-complexation effect needs to be combined with amino acid buffering to effectively inhibit local supersaturation and explosive nucleation.

[0104] Comparative Example 4 This comparative example is essentially the same as Example 1, except that a traditional buffer-dispersion compound system was used. Specifically, 8 g / L ammonium chloride was added as a buffer and 0.8 g / L polyvinylpyrrolidone (PVP-K30) as a dispersant to the reaction system. All other conditions were the same as in Example 1, but the proportions and dropping method were not optimized. Local pH fluctuations still occurred during the reaction, nucleus formation was slightly uneven, particles exhibited partial aggregation, a moderate particle size distribution, a span of approximately 1.40, a relatively high specific surface area, and a tap density of approximately 1.58 g / cm³. These results indicate that while the traditional buffer-dispersion compound system has some buffering and dispersing effects, the lack of a synergistic regulatory mechanism between amino acids and polyamino acids makes it difficult to effectively suppress local supersaturation and explosive nucleation. The resulting product exhibited lower sphericity, particle size uniformity, and tap performance compared to Example 1.

[0105] Comparative Example 5 This comparative example is essentially the same as Example 1, except that the temperature was raised immediately after the addition of the composite additive, and ammonia water was added dropwise and air was introduced; the 40°C pre-complexation treatment was not performed. The resulting product had an increased proportion of fine powder, decreased particle size uniformity, a span of approximately 1.35, and a tap density of approximately 1.73 g / cm³. 3 This result indicates that Mn before oxidation precipitation... 2+ Weak complexation pre-dispersion treatment can significantly improve nucleation uniformity and particle size distribution.

[0106] Comparative Example 6 This comparative example is essentially the same as Example 2, and also essentially the same as Example 1, except that it does not employ staged pH control during the reaction process. Instead, the pH of the system is kept constant at 8.8 ± 0.2 throughout the entire oxidation and precipitation process. Due to the lack of differentiated regulation between the nucleation and growth stages, it is difficult to effectively match the crystal nucleation and particle growth processes. The resulting product has a wider particle size distribution, decreased sphericity, and a tap density of approximately 1.78 g / cm³. 3 .

[0107] The results indicate that staged pH control is beneficial for coordinating the crystal nucleation and particle growth processes, promoting uniform spherical growth of particles, and thus obtaining manganese tetroxide products with narrower particle size distribution and higher tap density.

[0108] Comparative Example 7 This comparative example is essentially the same as Example 1, except that it was filtered and washed immediately after the reaction, and no weak-base ripening was performed. The resulting product has a relatively porous surface with a specific surface area of ​​approximately 10.8 m². 2 / g, tap density approximately 1.70 g / cm³ 3 The results indicate that weak alkali curing is beneficial for the secondary deposition of fine particles and surface densification, and is an important process step for improving tap density.

[0109] The process flow diagram for preparing manganese tetroxide in this invention is as follows: Figure 1 As shown. The amino acid-polyamino acid type buffering and dispersing integrated composite additive for Mn... 2+ A schematic diagram illustrating the mechanism of action of weak complex pre-dispersion, seed induction, and particle spheroidization growth is shown below. Figure 2 As shown. The X-ray diffraction pattern of the manganese tetroxide powder obtained in Example 1 of this invention is as follows. Figure 3 As shown, by Figure 3 As can be seen, the product exhibits distinct diffraction peaks at approximately 18.0°, 28.9°, 32.3°, 36.1°, 44.5°, 50.8°, 58.5°, 60.0°, and 64.7° at 2θ, all corresponding to the characteristic diffraction peaks of standard spinel-structured manganese tetroxide (Mn3O4), indicating that the main crystalline phase of the obtained product is manganese tetroxide. Simultaneously, no characteristic diffraction peaks of impurity phases such as manganese dioxide (MnO2), manganese trioxide (Mn2O3), manganese hydroxyoxide (MnOOH), and basic manganese sulfate were detected in the spectrum, demonstrating that the method of this invention can effectively suppress side reactions and improve the phase purity of the product.

[0110] Furthermore, the sharp peaks and stable baselines of the characteristic peaks indicate that the obtained manganese tetroxide has good crystallinity. These results demonstrate that the present invention employs an integrated amino acid-polyamino acid buffer dispersion system, combined with Mn... 2+Weak complexation pre-dispersion, seed induction, staged pH control, and three-stage oxidation regulation can achieve controllable preparation of manganese tetroxide, resulting in spherical manganese tetroxide products with pure crystal phase and good crystallinity.

[0111] The scanning electron microscope morphology of the manganese tetroxide powder obtained in Example 1 is as follows: Figure 4 As shown.

[0112] Figure 5 This is a schematic diagram comparing the particle size distribution and tap density of manganese tetroxide obtained under different process systems. A is the no-additive group, i.e., Comparative Example 1, which does not contain added amino acids or polyamino acids; B is a single buffer system, which is Comparative Example 2; C is a single dispersion system, which is Comparative Example 3; D is a traditional buffer dispersion compound system, which is Comparative Example 4; E is the amino acid-polyamino acid buffer dispersion integrated system of the present invention, which is Example 1.

[0113] In this invention, the D50, Span, specific surface area, and tap density of the materials were all tested using conventional methods. The results of the examples and comparative examples are summarized in Table 1.

[0114] Table 1: Detection results in the examples and comparative examples

[0115] As shown in Table 1, different additive systems and process parameters have a significant impact on the particle size distribution, specific surface area and tap density of Mn3O4 particles.

[0116] Examples 1-9 all employed a composite system of amino acids and sodium polyamino acids to regulate the crystal nucleation and particle growth processes through buffering, complexation, and dispersion. The resulting products all exhibited narrow particle size distributions (Span ≤ 1.10) and high tap densities (1.95–2.15 g / cm³). 3 ).

[0117] Example 3 exhibited the best overall performance, with a D50 of 13.2 μm, a Span of 0.82, and a specific surface area of ​​only 6.6 m². 2 / g, tap density reaches 2.15 g / cm³ 3 This indicates that under these conditions, the oxidation rate, pH buffering capacity, and particle growth rate are optimally matched, effectively promoting the directional aggregation of primary particles and the densification growth of spherical secondary particles, thereby obtaining a Mn3O4 product with uniform particle size, high sphericity, and dense internal structure.

[0118] In contrast, Comparative Example 1, lacking the addition of glycine and sodium polyaspartate, suffered from a lack of buffering and dispersing regulation. This resulted in drastic local pH fluctuations during the reaction, leading to explosive nucleation and disordered particle aggregation. The resulting product had a D50 of only 5.8 μm, a Span greater than 1.80, and a specific surface area increased to 12.5 m². 2 / g, tap density decreased to 1.50 g / cm³ 3 .

[0119] Comparative Examples 2 and 3 lacked sodium polyaspartate or glycine, respectively, and thus could not simultaneously achieve uniform nucleation and particle dispersion. Although some properties were superior to Comparative Example 1, the particle size distribution was still significantly wider, the specific surface area was higher, and the tap density was only 1.55 g / cm³. 3 and 1.62 g / cm 3 .

[0120] Comparative Example 4 uses a traditional NH4Cl-PVP buffer dispersion system, which can improve particle dispersibility to some extent, but due to the lack of an amino acid-polyamino acid synergistic regulation mechanism, the resulting particle sphericity and uniformity are still significantly lower than those of the embodiments of the present invention.

[0121] In Comparative Example 5, Mn was not performed. 2+ The weak complexation pre-dispersion treatment, the absence of staged pH control in Comparative Example 6, and the absence of weak alkali ripening in Comparative Example 7 further demonstrate that when the buffer system, oxidation conditions, or dispersion conditions deviate from the optimized range of this invention, they will all lead to a decrease in nucleation uniformity, an increase in fine powder, or a loose internal structure of particles, ultimately resulting in a decrease in tap density.

[0122] In summary, this invention employs a synergistic buffer-dispersion system constructed from amino acids and polyamino acids, combined with staged pH control and oxidation rate adjustment. This effectively suppresses local supersaturation and explosive nucleation, promotes the uniform growth of spherical Mn3O4 particles, and achieves the technical effects of narrow particle size distribution, low specific surface area, and high tap density. These results fully demonstrate the significant performance advantages of this invention compared to existing technologies.

[0123] The manganese salt, ammonia, air or oxygen, and amino acids and polyamino acid additives used in this invention can all be obtained through conventional industrial channels. The reaction conditions are mild and do not rely on complex templates, gel membranes, three-chamber tanks, or special fractionation equipment. The Mn... 2+ Weak complexation pre-dispersion, staged pH control, three-stage oxidation, and weak alkali ripening can all be achieved in a conventional stirred reactor, making it suitable for laboratory, pilot-scale, and industrial-scale preparation. The resulting manganese tetroxide powder has high tap density, low specific surface area, and good sphericity, meeting the requirements of lithium-ion battery cathode material precursors for powder flowability, packing performance, and sintering uniformity, and exhibits good industrial applicability.

[0124] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing spherical or near-spherical manganese tetroxide, characterized in that, Includes the following steps: S1. The amino acid buffer component and the polyamino acid complex dispersion component are compounded to obtain a composite additive, which is then added to the manganese salt bottom liquid prepared from soluble manganese salt and stirred to form a weak complex dispersion reaction system. S2. Heat the reaction system obtained in step S1 to 55-80°C, add ammonia and oxidizing gas in a co-current manner under stirring, and carry out the oxidation precipitation reaction by staged pH control. After the reactions in S3 and S2 are completed, the mixture is subjected to weak alkali ripening, followed by solid-liquid separation and processing to obtain spherical or near-spherical manganese tetroxide powder.

2. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S1, the amino acid buffer component is selected from one or more of glycine, β-alanine, lysine, arginine, histidine, glutamic acid, aspartic acid, or water-soluble salts of the above amino acids.

3. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S1, the polyamino acid complex dispersion component is selected from one or more of polyaspartic acid, sodium polyaspartate, polyglutamic acid, sodium polyglutamate, or water-soluble derivatives of the above polyamino acids.

4. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S1, the mass ratio of the amino acid-type buffer component to the polyamino acid-type complex dispersion component is 1:5 to 5:

1.

5. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, The amino acid buffer component is glycine and / or β-alanine, the polyamino acid complex dispersion component is sodium polyaspartate, and the mass ratio of β-alanine to sodium polyaspartate is 1:2 to 2:

1.

6. The method for preparing spherical or near-spherical manganese tetroxide according to any one of claims 1 to 5, characterized in that, In S1, the amount of the composite additive added is 0.5 to 2.0 g / L.

7. The method for preparing spherical or near-spherical manganese tetroxide according to any one of claims 1 to 5, characterized in that, In S2, ammonia water is added at a molar ratio of ammonia to manganese of 2.2:1 to 3.0:1, and the pH is adjusted in stages by segmented dripping or by pH feedback control. Specifically, the pH is 8.0 to 8.6 during the crystal nucleation stage, 8.6 to 9.3 during the crystal growth stage, and 8.3 to 9.0 during the maturation stage, with pH fluctuations ≤ ±0.

20.

8. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S2, the oxidizing gas is controlled in three stages: the oxidizing gas flow rate is 0.05–0.20 L / min in the low-oxygen nucleation stage, 0.20–0.60 L / min in the high-oxygen growth stage, and 0–0.20 L / min in the low-oxygen ripening stage.

9. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S2, the oxidizing gas is selected from oxygen or an oxygen-containing mixture.

10. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S2, manganese tetroxide seed crystals are added before oxidation precipitation or at the initial stage of crystal nucleus formation. The D50 of the manganese tetroxide seed crystals is 0.1 to 5.0 μm. The amount of seed crystals added is 0.01% to 5.0% based on the mass of manganese in the system.

11. The method for preparing spherical or near-spherical manganese tetroxide according to claim 10, characterized in that, Before being added to the reaction system, the manganese tetroxide seed crystals are first contacted and dispersed with the integrated buffer and dispersion additive for 5 to 30 minutes to form an adsorption and dispersion layer containing amino acids and polyamino acids on the seed crystal surface.

12. The method for preparing spherical or near-spherical manganese tetroxide according to claim 1, characterized in that, In S3, the weak alkali ripening is carried out by keeping the temperature at pH 8.3–9.0 and 60–90°C for 0.5–3 hours.

13. A spherical or near-spherical manganese tetroxide prepared by any one of the preparation methods of claims 1 to 12, characterized in that, The manganese tetroxide is a spinel-structured Mn3O4 with a tap density ≥1.8 g / cm³. 3 Specific surface area ≤10m² 2 / g, D50 is 5.0~18.0 μm, Span≤1.

20.

14. The application of the spherical or near-spherical manganese tetroxide as described in claim 13 in the preparation of a precursor for a lithium-ion battery cathode material.

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