Preparation method and application of modified "sea urchin-type" manganese tetraoxide

Abstract

This invention provides a method for preparing and applying modified "sea urchin-type" manganese tetroxide. The method uses ammonia as the main precipitant, adding manganese sulfate, the precipitant, and a complexing agent to an alkaline solution. After reaction, the solution is filtered, washed, and dried to obtain "sea urchin-type" manganese tetroxide. Further surface modification is achieved by introducing elements such as Al, Mg, Ti, and Zn through liquid-phase doping, forming a coating layer on the surface of the "sea urchin-type" manganese tetroxide. This further improves the electrochemical performance and stability of lithium manganese oxide materials. The invention provides modified "sea urchin-type" manganese tetroxide with primary grains larger than 300 nm. This manganese tetroxide, with its highly crystalline, large-sized conical grains, effectively reduces the corrosive effect of the electrolyte.

Description

Technical Field

[0001] This application belongs to the field of energy materials technology, and in particular relates to a method for preparing and applying modified "sea urchin-type" manganese tetroxide. Background Technology

[0002] Lithium spinel manganese oxide (LiMn2O4) is hailed as one of the most promising cathode materials for lithium-ion batteries due to its advantages such as high operating voltage, environmental friendliness, low cost, abundant resources, and good safety performance. However, it suffers from severe capacity decay during high-temperature cycling, and its high-spin Mn content... 3+ The associated Jahn-Teller distortion leads to significant volume changes and severe capacity decay under deep discharge conditions. Furthermore, under the corrosive effects of the electrolyte, Mn... 3+ The disproportionation reaction is intensified, producing soluble Mn. 2+ Mn dissolution damages the LiMn2O4 structure, thus deteriorating battery performance. Currently, the main methods to reduce Mn dissolution are elemental doping, surface coating, or single crystallization. Manganese tetroxide (MtO), as one of the main raw materials for lithium manganese oxide, exhibits good structural inheritance during sintering due to its similar spinel-type structure to lithium manganese oxide. Therefore, by controlling the primary grain size of MtO, the primary grain size of lithium manganese oxide can be controlled. Larger primary grains can effectively reduce Mn dissolution and improve the high-temperature capacity retention of lithium manganese oxide. Currently, the primary grains of mainstream MtO materials on the market are relatively small, generally less than 100 nm. Lithium manganese oxide cathode materials prepared with this material have sufficient contact with the electrolyte, which is beneficial for lithium-ion diffusion and greatly helps to improve the discharge capacity of lithium manganese oxide. However, the lithium manganese oxide cathode materials prepared with this material will exacerbate Mn dissolution under the erosion of the electrolyte. 3+ The disproportionation reaction produces soluble Mn. 2+ This damages the LiMn2O4 structure, thereby deteriorating the battery performance. Summary of the Invention

[0003] This application provides a method for preparing and applying modified "sea urchin-type" manganese tetroxide, which aims to solve to some extent the problem of small primary grain size of lithium manganese oxide cathode material products, which are easily eroded by electrolyte and have their LiMn2O4 structure destroyed.

[0004] In a first aspect, this application provides a method for preparing modified "sea urchin-type" manganese tetroxide, comprising the following steps:

[0005] S1. Preparation of the base solution: Mix water, precipitant, and complexing agent to prepare the base solution;

[0006] S2. Preparation of manganese tetroxide: Manganese sulfate, precipitant and complexing agent are added to the bottom liquid. After reaction, the mixture is filtered, washed and dried to obtain "sea urchin type" manganese tetroxide.

[0007] S3. Surface modification of manganese tetroxide: The above-mentioned manganese tetroxide is mixed with water, complexing agent and dispersant in a reaction vessel; at the same time, the mixed metal salt solution, complexing agent and precipitant are added to the reaction vessel in parallel flow and concentrated to make the solid content of manganese tetroxide reach the set value. After the reaction, the mixture is filtered, washed and dried to obtain modified "sea urchin type" manganese tetroxide.

[0008] In one embodiment, the concentration of the manganese sulfate solution is 100-400 g / L; the precipitant is ammonia water with a concentration of 10-35 wt%; the concentration of the complexing agent is 5-50 g / L, and the complexing agent includes one or more combinations of aminocarboxylic acid chelating agents such as ammonia water, ammonium sulfate, tetrasodium iminodisuccinate, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, and aminotriacetic acid.

[0009] To reduce the reaction rate and increase the size of primary crystals, this invention uses ammonia as the main precipitant. Ammonia, being a weak base, is more effective than strongly alkaline sodium hydroxide / potassium hydroxide in reducing the reaction rate and promoting the preferential growth of primary crystals. Furthermore, the complexing agent in this invention is an ammonium salt or an aminocarboxylic acid chelating agent. 4+ Increasing the content will enhance the complexation with Mn, thus preventing Mn from forming. 2+ Directly with OH - A reaction occurs. Aminocarboxylic acid chelating agents will react with Mn. 2+ Ca 2+ Mg 2+ Divalent metal cations have a strong chelating effect, which can reduce the reaction rate and reduce the precipitation of calcium and magnesium impurities.

[0010] In some embodiments, the molar ratio of water:precipitant:complexing agent in S1 is 550:(0.05-0.1):(0.15-0.3), and the pH of the substrate is 8.8-9.5. The purpose of adding a small amount of precipitant and complexing agent to the substrate is to control the pH value, keeping it close to the pH of subsequent reactants, reducing pH fluctuations, and promoting uniform growth of primary crystals.

[0011] In some embodiments, the reaction conditions in S2 are: air or oxygen as the oxidant, pH = 8.5-9.2, reaction temperature 50-80°C, and reaction time 6-15h.

[0012] In some embodiments, the primary grain size of manganese tetroxide in S2 is 300-700 nm, and the crystal morphology is truncated octahedron.

[0013] In some embodiments, the mass ratio of manganese tetroxide, water, complexing agent, and dispersant in S3 is 1:(3.3-5):(0.1-0.2):(0.03-0.15). The purpose of pre-adding the complexing agent and dispersant to the product in S2 is to better form a modified coating layer on the surface of manganese tetroxide, which is beneficial for uniform particle dispersion, prevents particle agglomeration, and prevents the formation of new crystal nuclei. The second addition of the precipitant is used to precipitate metal salt ions, mainly manganese ions. The complexing agent can control the precipitation rate of metal salt ions. The combined use of the precipitant and complexing agent can effectively regulate the particle nucleation rate and growth rate, which is beneficial for the stability of the modified coating layer and the uniformity of doped elements. The phased addition plays a comprehensive role in controlling the particle nucleation rate and growth rate.

[0014] In some embodiments, the mixed metal salt solution in S3 is a mixture of manganese sulfate solution and other metal salt solutions. The other metals are one or more combinations of Al, Mg, Zn, Cu, Fe, Ti, Ni, Co, etc. The mass concentration of the mixed metal salt is 0.5-3 mol / L, and the molar ratio of manganese to other metals in the manganese sulfate is 1:0.01-0.5. The concentrated manganese tetroxide has a solid content ≥15%. The purpose of concentration is to increase the collision frequency of particles.

[0015] In some embodiments, the dispersant in S3 is: hexadecyltrimethylammonium bromide, sodium stearate, polyethylene glycol, sodium lauryl ether sulfate, sodium dodecylbenzene sulfonate, etc.

[0016] In some embodiments, the reaction conditions in S3 are: air or oxygen as the oxidant, pH = 8.0-8.7, reaction temperature 60-80°C, and reaction time 10-18h.

[0017] The synthesis reaction equations for S2 and S3 in this invention are the same, the difference being that S3 is an in-situ growth based on S2.

[0018] Mn 2+ +2OH - →Mn(OH)2↓

[0019] 6Mn(OH)2 + O2 → 2Mn3O4 + 6H2O

[0020] In step S3, increasing the solid content promotes the formation of new primary particles induced by crystal nuclei, which to some extent inhibits the preferential growth of existing primary particles. Furthermore, lowering the reaction pH helps slow down the formation rate of new crystal nuclei. These methods effectively reduce the c-axis length of the manganese tetroxide (Mn3O4) unit cell, resulting in a smaller Mn3O4 unit cell volume, which is more conducive to lithium-ion diffusion and improves electrochemical performance. In addition, using liquid-phase doping allows for nanoscale mixing of manganese sulfate solution and dopant solution, resulting in more uniform doping. The introduction of dopant elements can reduce the amount of Mn... 3+ Disproportionation and the John-Teller effect are beneficial to improving electrochemical performance.

[0021] In a second aspect, the present invention provides an application of modified "sea urchin-type" manganese tetroxide as described in the first aspect, characterized in that it is used to prepare lithium manganese oxide cathode material products.

[0022] In some embodiments, the method for preparing the lithium manganese oxide cathode material product is as follows: modified "sea urchin type" manganese tetroxide and lithium carbonate are added at a molar ratio of Li / Mn of 0.53:1, calcined at 750-780°C for 12-24 hours in an air atmosphere, and then crushed and graded to obtain the lithium manganese oxide cathode material product.

[0023] It is understood that the beneficial effects of the second and third aspects mentioned above can be found in the relevant descriptions in the first aspect above, and will not be repeated here.

[0024] Compared with the prior art, the beneficial effects of this application are as follows:

[0025] 1. This invention provides modified "sea urchin-type" manganese tetroxide with primary grains larger than 300 nm. This manganese tetroxide, with its highly crystalline, large-sized conical grains, can effectively reduce the corrosive effect of the electrolyte. Furthermore, by modifying the particle surface and introducing elements such as Al, Mg, Ti, and Zn through liquid-phase doping, a coating layer is formed on the surface of the "sea urchin-type" manganese tetroxide, which can further improve the electrochemical performance and stability of lithium manganese oxide materials.

[0026] 2. The modified "sea urchin-type" manganese tetroxide provided by this invention has a dense and large primary grain size that significantly helps to improve the cycling performance of lithium manganese oxide. Furthermore, by in-situ doping and coating the surface of the "sea urchin-type" manganese tetroxide, firstly, the obvious core-shell structure can significantly improve the high-temperature cycling performance of lithium manganese oxide, and secondly, this method can reduce the c-axis length of manganese tetroxide and shorten the lithium ion transport distance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 , Figure 2 These are SEM images of the manganese tetroxide sample from Example 1 at different magnifications;

[0029] Figure 3 , Figure 4 These are SEM images of the manganese tetroxide sample from Comparative Example 1 at different magnifications.

[0030] Figure 5 , Figure 6 These are SEM images of the manganese tetroxide sample from Comparative Example 3 at different magnifications. Detailed Implementation

[0031] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0033] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, a~b (i.e., a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple.

[0034] The terms "first" and "second" are used only to describe the purpose and to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the provisions of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0035] The terminology used in the embodiments of this application is for the purpose of describing particular implementations only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the implementations of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0036] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0037] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0038] 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.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0040] The technical solution of this application will be illustrated below through specific embodiments and comparative examples.

[0041] In order to enable those skilled in the art to clearly understand the above-described implementation details and operations of this application, and to demonstrate the significant improvement in performance of the embodiments of this application, the above technical solutions are illustrated below through multiple embodiments.

[0042] Example 1:

[0043] A method for preparing and applying modified "sea urchin-type" manganese tetroxide includes the following steps:

[0044] Preparation of S1 solution: Water, 20wt% ammonia solution and 30g / L nitric acid solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.2.

[0045] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 200 g / L manganese sulfate solution, 20 wt% ammonia solution, and 30 g / L nitric acid solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 9.0, the concentration of nitric acid in the system was 10 g / L, and the reaction time was 9 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" manganese tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0046] Surface modification of S3 "sea urchin-type" manganese tetroxide. In a reactor, manganese tetroxide product was mixed with water, 30 g / L nitric acid solution, and hexadecyltrimethylammonium bromide in a mass ratio of 1:3:0.1:0.08 to prepare a mixed solution with a solid content of 25% and a complexing agent concentration of 6 g / L. The temperature was 70℃. A 2.2 mol / L mixed metal sulfate solution (Mn:Al molar ratio of 10:3), a 20 wt% ammonia solution, and a 30 g / L nitric acid solution were added concurrently to the reactor, with air used as the oxidant. The reaction temperature was 70℃, the reaction pH was 8.5, the nitric acid concentration was 6 g / L, and a concentration device was activated to achieve a solid content of 21% in the manganese tetroxide material. The reaction time was 15 h. After filtration, washing, and drying, the modified "sea urchin-type" manganese tetroxide was obtained.

[0047] The modified "sea urchin type" manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, calcined at 780°C for 12 hours in air, and then crushed and graded to obtain lithium manganese oxide product.

[0048] Example 2:

[0049] A method for preparing and applying modified "sea urchin-type" manganese tetroxide includes the following steps:

[0050] The difference between this embodiment and Embodiment 1 is that ammonium sulfate and tetrasodium ethylenediaminetetraacetic acid complexing agent are used instead of aminotriacetic acid complexing agent, and the mixed metal sulfate solution is (Mn∶Al∶Zn=10∶2.5∶0.1).

[0051] Preparation of S1 solution: Water, 20wt% ammonia solution and 50g / L ammonium sulfate solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.2.

[0052] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 200 g / L manganese sulfate solution, 20 wt% ammonia solution, and 30 g / L tetrasodium ethylenediaminetetraacetate solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 9.0, the concentration of tetrasodium ethylenediaminetetraacetate in the system was 10 g / L, and the reaction time was 9 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" Manganese Tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0053] Surface modification of S3 "sea urchin-type" manganese tetroxide. In a reactor, manganese tetroxide was mixed with water, 30 g / L ammoniatriacetic acid solution, and sodium dodecylbenzenesulfonate in a mass ratio of 1:3:0.1:0.08 to prepare a mixed solution with a solid content of 25% and a complexing agent concentration of 6 g / L. The temperature was 70℃. A 2.2 mol / L mixed metal sulfate solution (Mn:Al:Zn = 10:2.5:0.1), a 20 wt% ammonia solution, and a 30 g / L tetrasodium ethylenediaminetetraacetate solution were added concurrently to the reactor, with air used as the oxidant. The reaction temperature was 70℃, the reaction pH was 8.5, the concentration of tetrasodium ethylenediaminetetraacetate was 6 g / L, and a concentration device was activated to achieve a solid content of 21% in the manganese tetroxide material. The reaction time was 15 h. After filtration, washing, and drying, the modified "sea urchin-type" manganese tetroxide was obtained.

[0054] The modified "sea urchin type" manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, calcined at 780°C for 12 hours in air, and then crushed and graded to obtain lithium manganese oxide product.

[0055] Example 3:

[0056] A method for preparing and applying modified "sea urchin-type" manganese tetroxide includes the following steps:

[0057] The difference between this invention and Example 1 is that the concentrations of manganese sulfate and ammonia, the reaction pH, and the solid content were changed.

[0058] Preparation of S1 solution: Water, 25wt% ammonia solution and 30g / L nitric acid solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.0.

[0059] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 120 g / L manganese sulfate solution, 25 wt% ammonia solution, and 30 g / L nitric acid solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 8.8, the concentration of nitric acid in the system was 10 g / L, and the reaction time was 6-15 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" manganese tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0060] Surface modification of S3 "sea urchin-type" manganese tetroxide. A mixed solution of manganese tetroxide, water, 30 g / L nitric acid triacetic acid solution, and hexadecyltrimethylammonium bromide in a mass ratio of 1:2.3:0.1:0.1 was prepared in a reactor at 70°C. The solution contained 30% solids and 6 g / L complexing agent. A 2.2 mol / L mixed metal sulfate solution (Mn:Al molar ratio 10:3), 25 wt% ammonia solution, and 30 g / L nitric acid triacetic acid solution were added concurrently to the reactor, with air used as the oxidant. The reaction temperature was 70°C, the reaction pH was 8.6, and the nitric acid concentration was 6 g / L. A concentration device was activated to reduce the solids content of the manganese tetroxide to 25%, and the reaction time was 15 h. The mixed solution was filtered, washed, and dried to obtain the modified "sea urchin-type" manganese tetroxide.

[0061] The above-mentioned manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, and calcined at 780°C for 12 hours in air atmosphere. After crushing and grading, lithium manganese oxide product was obtained.

[0062] Comparative Example 1:

[0063] A method for preparing manganese tetroxide and its application, comprising the following steps:

[0064] The difference between this comparative example and Example 1 is that the S3 manganese tetroxide surface modification step is omitted.

[0065] Preparation of S1 solution: Water, 20wt% ammonia solution and 30g / L nitric acid solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.2.

[0066] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 200 g / L manganese sulfate solution, 20 wt% ammonia solution, and 30 g / L nitric acid solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 9.0, the concentration of nitric acid in the system was 10 g / L, and the reaction time was 6-15 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" manganese tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0067] Comparative Example 2:

[0068] A method for preparing manganese tetroxide and its application, comprising the following steps:

[0069] The difference between this comparative example and Example 1 is that a strongly alkaline NaOH is used as the precipitant.

[0070] Preparation of S1 solution: Water, 30% NaOH solution, and 30 g / L nitric acid solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.2.

[0071] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 200 g / L manganese sulfate solution, 30% NaOH solution, and 30 g / L nitric acid solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 9.0, the concentration of nitric acid in the system was 10 g / L, and the reaction time was 6-15 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" manganese tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0072] Surface modification of S3 "sea urchin-type" manganese tetroxide. In a reactor, manganese tetroxide product was mixed with water, 30 g / L nitric acid solution, and hexadecyltrimethylammonium bromide in a mass ratio of 1:3:0.1:0.08 to prepare a mixed solution with a solid content of 25% and a complexing agent concentration of 6 g / L. The temperature was 70℃. A 2.2M mixed metal sulfate solution (Mn:Al molar ratio of 10:3), 30% NaOH solution, and 30 g / L nitric acid solution were added to the reactor concurrently, with air used as the oxidant. The reaction temperature was 70℃, the reaction pH was 8.5, the nitric acid concentration was 6 g / L, and a concentration device was activated to achieve a solid content of 21% in the manganese tetroxide material. The reaction time was 15 h. After filtration, washing, and drying, the modified "sea urchin-type" manganese tetroxide was obtained. The above-mentioned manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, and calcined at 780°C for 12 hours in air atmosphere. After crushing and grading, lithium manganese oxide product was obtained.

[0073] The above-mentioned manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, and calcined at 780°C for 12 hours in air atmosphere. After crushing and grading, lithium manganese oxide product was obtained.

[0074] Comparative Example 3:

[0075] A method for preparing manganese tetroxide and its application, comprising the following steps:

[0076] The difference between this comparative example and Example 1 is that the solid content of manganese tetroxide in step S3 is 8% (less than 15%).

[0077] Preparation of S1 solution: Water, 20wt% ammonia solution and 30g / L nitric acid solution were mixed in a molar ratio of 550:0.1:0.18 to prepare the base solution, and the pH of the base solution was controlled at 9.2.

[0078] Preparation of S2 "Sea Urchin Type" Manganese Tetraoxide: The base solution was added concurrently to a reaction vessel with 200 g / L manganese sulfate solution, 20 wt% ammonia solution, and 30 g / L nitric acid solution. Air was used as the oxidant. The reaction temperature was 70℃, the pH was 9.0, the concentration of nitric acid in the system was 10 g / L, and the reaction time was 6-15 h. After washing, pressure filtration, and drying, the mixed solution yielded "Sea Urchin Type" manganese tetraoxide with a primary crystal size of 300-700 nm and a morphology of truncated octahedrons.

[0079] Surface modification of S3 "sea urchin-type" manganese tetroxide. In a reactor, manganese tetroxide product was mixed with water, 30 g / L nitric acid solution, and hexadecyltrimethylammonium bromide in a mass ratio of 1:5.6:0.1:0.12 to prepare a mixed solution with a solid content of 15% and a complexing agent concentration of 6 g / L. The temperature was 70℃. A 2.2M mixed metal sulfate solution (Mn:Al molar ratio of 10:3), 20 wt% ammonia solution, and 30 g / L nitric acid solution were added to the reactor concurrently, with air used as the oxidant. The reaction temperature was 70℃, the reaction pH was 8.5, the nitric acid concentration was 6 g / L, and a concentration device was activated to reduce the solid content of the manganese tetroxide material to 8%. The reaction time was 15 h. After filtration, washing, and drying, the modified "sea urchin-type" manganese tetroxide was obtained. The above-mentioned manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, and calcined at 780°C for 12 hours in air atmosphere. After crushing and grading, lithium manganese oxide product was obtained.

[0080] The above-mentioned manganese tetroxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, and calcined at 780°C for 12 hours in air atmosphere. After crushing and grading, lithium manganese oxide product was obtained.

[0081] SEM comparison of manganese tetroxide particles in Example 1 and Comparative Example 1 Figure 1 , 2 and Figure 3 , 4 As shown, Comparative Example 1 is a "sea urchin-type" manganese tetroxide sample, with primary grains being truncated octahedrons of approximately 600 nm. In contrast, Example 1 shows a coating layer formed on the surface of the "sea urchin-type" manganese tetroxide sample. A SEM comparison of the manganese tetroxide particles in Example 1 and Comparative Example 3 is shown below. Figure 1 , 2 and Figure 5 , 6 As shown, when the content of manganese tetroxide in the system is low, there is a tendency for a coating layer to form on the particle surface, but a distinct prismatic structure is visible. Therefore, the ammonia and aminocarboxylic acid complexing agents used in this invention are beneficial to the growth of primary grains, enabling the preparation of manganese tetroxide products with larger primary grains. Furthermore, through the intense collisions between particles in a high solids content environment, a coating layer grows in situ on the surface of the "sea urchin-type" manganese tetroxide, constructing a distinct core-shell structure.

[0082] Performance Testing: Secondary button batteries (model CR2025) were prepared using lithium foil as the negative electrode and the lithium manganese oxide positive electrode materials prepared in the examples and comparative examples as the positive electrode. Under a voltage of 3.0–4.2V, the batteries underwent two cycles of 0.2C charging / discharging, followed by 1C charging / discharging. The initial charge / discharge efficiency and the initial 1C discharge capacity were tested. The results are shown in Table 1. Compared to Comparative Example 1, the discharge capacity and capacity retention of Examples 1-3 were significantly improved. This is mainly due to the in-situ coating layer of modified manganese tetroxide, which reduces manganese dissolution. Furthermore, the intact small-particle crystals within the coating layer facilitate lithium-ion diffusion, thus improving the capacity of lithium manganese oxide. The capacity retention of Example 1 was higher than that of Comparative Example 2. This indicates that using ammonia as a precipitant and aminocarboxylic acid chelating agents as complexing agents can improve the crystallinity of manganese tetroxide and promote the formation of large primary crystal particles, which helps reduce manganese dissolution and electrolyte corrosion, thereby improving the capacity retention of lithium manganese oxide. The discharge capacity and capacity retention of Example 1 are higher than those of Comparative Example 3. This is mainly because the solid content of Comparative Example 3 is only 8%, the particle-particle collision is not intense enough during the modification process, there are a large number of small primary octahedral grains on the particle surface, and it is impossible to build a clear coating layer. This results in the manganese dissolution effect still being more obvious and the capacity retention is relatively low.

[0083] Table 1: Performance Test Results of Examples

[0084]

[0085]

[0086] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0087] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing modified "sea urchin-type" manganese tetroxide, characterized in that, Includes the following steps: S1. Preparation of the base solution: Mix water, precipitant, and complexing agent to prepare the base solution, wherein the pH of the base solution is 8.8-9.5; S2. Preparation of manganese tetroxide: Add manganese sulfate solution, precipitant and complexing agent to the bottom solution. After reaction, filter, wash and dry to obtain "sea urchin type" manganese tetroxide. The oxidant in the reaction is air or oxygen, and the pH of the reaction is 8.5-9.

2. S3. Surface modification of manganese tetroxide: The above-mentioned manganese tetroxide is mixed with water, complexing agent, and dispersant in a reaction vessel; simultaneously, a mixed metal salt solution, complexing agent, and precipitant are added to the reaction vessel in a co-current flow and concentrated to make the solid content of manganese tetroxide ≥15wt%. After the reaction, the mixture is filtered, washed, and dried to obtain modified "sea urchin type" manganese tetroxide. The mixed metal salt solution is a mixture of manganese sulfate solution and other metal salt solutions. The metals in the other metal salts are one or more combinations of Al, Mg, Zn, Cu, Fe, Ti, Ni, and Co. The concentration of the mixed metal salt is 0.5-3mol / L, and the molar ratio of manganese in manganese sulfate to the metals in other metal salts is 1:0.01-0.

5. The oxidant in the reaction is air or oxygen, and the pH of the reaction is 8.0-8.

7. The precipitant is ammonia, and the complexing agent includes one or more combinations of ammonia, ammonium sulfate, tetrasodium iminodisuccinate, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetic acid, tetrasodium ethylenediaminetetraacetic acid, diethyltriaminepentaacetic acid, and aminotriacetic acid.

2. The preparation method according to claim 1, characterized in that, The concentration of the manganese sulfate solution in S2 is 100-400 g / L; the concentration of the precipitant in S1, S2, and S3 is 10-35 wt%; and the concentration of the complexing agent in S1, S2, and S3 is 5-50 g / L.

3. The preparation method according to claim 1, characterized in that, The molar ratio of water to precipitant to complexing agent in S1 is 550: (0.05-0.1): (0.15-0.3).

4. The preparation method according to claim 1, characterized in that, The reaction conditions described in S2 are: reaction temperature 50-80℃, reaction time 6-15h.

5. The preparation method according to claim 1, characterized in that, The primary grain size of manganese tetroxide described in S2 is 300-700 nm, and the crystal morphology is truncated octahedron.

6. The preparation method according to claim 1, characterized in that, The mass ratio of manganese tetroxide, water, complexing agent and dispersant in S3 is 1: (3.3-5): (0.1-0.2): (0.03-0.15).

7. The preparation method according to claim 1, characterized in that, The dispersant mentioned in S3 is: cetyltrimethylammonium bromide, sodium stearate, polyethylene glycol, sodium lauryl ether sulfate, and sodium dodecylbenzene sulfonate.

8. The preparation method according to claim 1, characterized in that, The reaction conditions described in S3 are: reaction temperature 60-80℃, reaction time 10-18h.

9. An application of the modified "sea urchin-type" manganese tetroxide as described in claim 1, characterized in that, Used to prepare lithium manganese oxide cathode materials.

10. The application according to claim 9, characterized in that, The method for preparing lithium manganese oxide products is as follows: modified "sea urchin type" manganese tetroxide and lithium carbonate are added at a molar ratio of Li / Mn of 0.53:1, calcined at 750~780℃ for 12~24h in an air atmosphere, and then crushed and graded to obtain lithium manganese oxide cathode material products.

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