Preparation method and application of modified sea urchin type manganous-manganic oxide

Abstract

The invention provides a preparation method and application of modified'sea urchin type 'manganous-manganic oxide, ammonia water is used as a main precipitator, manganese sulfate, the precipitator and a complexing agent are added into an alkaline base solution, filtering, washing and drying are performed after reaction to obtain'sea urchin type' manganous-manganic oxide, and the modified'sea urchin type 'manganous-manganic oxide is obtained by modifying the surfaces of particles on the basis. Al, Mg, Ti, Zn and other elements are introduced through liquid phase doping, a wrapping layer is formed on the surface of the sea urchin type manganous-manganic oxide, and the electrochemical performance and stability of the lithium manganate material can be further improved. The invention provides modified sea urchin-type manganous-manganic oxide with primary crystal grains larger than 300 nm, and the manganous-manganic oxide can effectively reduce the erosion effect of electrolyte by means of high-crystallinity and large-size conical crystal grains.

Description

Technical Field

[0001] The present application belongs to the technical field of energy materials, and in particular relates to a preparation method and application of modified "sea urchin-type" manganese tetraoxide. Background Art

[0002] Spinel lithium manganese oxide (LiMn2O4) is known as one of the most promising positive electrode materials for lithium-ion batteries due to its high operating voltage, environmental friendliness, low cost, abundant resources, and good safety performance. However, it suffers from severe capacity decay during the cycle at high temperatures. 3+ The related Jahn-Teller distortion will lead to huge volume change and severe capacity decay under deep discharge state. In addition, under the corrosion of electrolyte, Mn 3+ The disproportionation reaction of Mn is intensified, producing soluble Mn 2+ , destroying the LiMn2O4 structure, and thus deteriorating the performance of the battery. Currently, the dissolution of Mn is mainly reduced by element doping, surface coating or single crystallization. As one of the main raw materials of lithium manganate, manganese tetraoxide has a similar spinel structure to lithium manganate and has good structural inheritance during the sintering process. Therefore, the size of the primary grains of lithium manganate can be controlled by regulating the primary grain size of manganese tetraoxide. Larger primary grains can effectively reduce the dissolution of Mn and improve the high-temperature capacity retention rate of lithium manganate. The primary grains of the mainstream manganese tetraoxide material on the market are relatively small, and their size is generally less than 100nm. The lithium manganate positive electrode material prepared by this material has a more sufficient contact with the electrolyte, which is conducive to the diffusion of lithium ions and is of great help to improve the discharge capacity of lithium manganate. However, the lithium manganate positive electrode material prepared by this material will aggravate the Mn under the erosion of the electrolyte. 3+ disproportionation reaction to produce soluble Mn 2+ , destroying the LiMn2O4 structure and thus deteriorating the performance of the battery. Summary of the invention

[0003] The present application provides a preparation method and application of a modified "sea urchin type" manganese tetraoxide, which aims to solve the problem that the primary grains of lithium manganate positive electrode material products are small and easily corroded by electrolyte, destroying the LiMn2O4 structure.

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

[0005] S1. Prepare base liquid: mix water, precipitant and complexing agent to prepare base liquid;

[0006] S2, preparing manganese tetraoxide: adding manganese sulfate, a precipitant and a complexing agent to the base liquid, filtering, washing and drying after the reaction to obtain "sea urchin type" manganese tetraoxide;

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

[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 ammonia water, ammonium sulfate, tetrasodium iminodisuccinate, ethylenediaminediacetic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid disodium salt, ethylenediaminetetraacetic acid tetrasodium salt, diethyltriaminepentaacetic acid, nitrilotriacetic acid and other aminocarboxylic acid chelating agents. One or more combinations thereof.

[0009] In order to reduce the reaction rate and increase the size of the primary crystals, the present invention uses ammonia water as the main precipitant. Ammonia water is a weak base, which is more favorable than strong alkaline sodium hydroxide / potassium hydroxide in reducing the reaction rate and promoting the preferential growth of the primary crystals. In addition, the complexing agent of the present invention is an ammonium salt or an aminocarboxylic acid chelating agent, NH 4+ The increase in content will enhance the complexation with Mn and avoid Mn 2+ Directly with OH - Aminocarboxylic acid chelating agents react with Mn 2+ , Ca 2+ Mg 2+ +2-valent metal cations have a strong chelating effect, which can reduce the reaction rate and 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 base solution is 8.8-9.5. The purpose of adding a small amount of precipitant and complexing agent to the base solution is to control the pH value, keep it close to the pH of the subsequent reactants, reduce the fluctuation of the pH value, and facilitate the uniform growth of the primary grains.

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

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

[0013] In some embodiments, the mass ratio of manganese tetraoxide, water, complexing agent and dispersant in S3 is: 1: (3.3-5): (0.1-0.2): (0.03-0.15). The purpose of adding complexing agent and dispersant in advance to the product of S2 is to better form a modified coating layer on the surface of manganese tetraoxide, which is conducive to uniform dispersion of particles, prevent particle agglomeration, and prevent the formation of new crystal nuclei. The second addition of precipitant is used to precipitate metal salt ions mainly composed of manganese ions. The complexing agent can control the precipitation rate of metal salt ions. The combined use of precipitant and complexing agent can effectively regulate the particle nucleation rate and growth rate, which is conducive to the stability of the modified coating layer and the uniformity of the doping elements. The addition in batches 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 a combination of one or more of Al, Mg, Zn, Cu, Fe, Ti, Ni, Co, etc., the mass concentration of the mixed metal salt is 0.5-3 mol / L, the molar ratio of manganese in manganese sulfate to other metals is 1:0.01-0.5; the concentrated manganese tetraoxide has a solid content of ≥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 polyether sulfate, sodium dodecylbenzene sulfonate, etc.

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

[0017] The synthesis reaction equations of S2 and S3 of the present invention are consistent, and the difference is that S3 is grown in situ on the basis of S2.

[0018] Mn 2+ +2OH - →Mn(OH)2↓

[0019] 6Mn(OH)2+O2→2Mn3O4+6H2O

[0020] In step S3, the increase in solid content promotes the formation of new primary particles induced by crystal nuclei, which will inhibit the preferential growth of existing primary particles to a certain extent, and lowering the reaction pH is conducive to slowing down the rate of new crystal nucleation. The above methods can effectively reduce the c-axis length of the manganese tetraoxide unit cell, making the unit cell volume of manganese tetraoxide smaller, which is more conducive to the diffusion of lithium ions and improves the electrochemical performance. In addition, the use of liquid phase doping can achieve nanoscale mixing of manganese sulfate solution and doping element solution, making doping more uniform, and the introduction of doping elements can reduce Mn 3+ Disproportionation reaction and John-Teller effect are beneficial to the improvement of electrochemical performance.

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

[0022] In some embodiments, the method for preparing the lithium manganate positive electrode material product is: adding modified "sea urchin type" manganese tetraoxide and lithium carbonate in a molar ratio of Li / Mn of 0.53:1, calcining at 750-780°C for 12-24h in an air atmosphere, and obtaining the lithium manganate positive electrode material product after crushing and grading.

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

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

[0025] 1. The present invention provides a modified "sea urchin type" manganese tetraoxide with a primary grain size greater than 300 nm. The manganese tetraoxide can effectively reduce the erosion of the electrolyte by virtue of its high crystallinity and large-sized conical grains. In addition, by modifying the surface of the particles 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 tetraoxide, which can further improve the electrochemical performance and stability of the lithium manganate material.

[0026] 2. The modified "sea urchin-type" manganese tetraoxide provided by the present invention has dense and large primary grains, which are significantly helpful in improving the cycle performance of lithium manganate. By in-situ doping and coating on the surface of the "sea urchin-type" manganese tetraoxide, firstly, the obvious core-shell structure can significantly improve the high-temperature cycle performance of lithium manganate, and secondly, this method can reduce the c-axis length of manganese tetraoxide and shorten the transmission distance of lithium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 , Figure 2 1 is a SEM image of the manganese tetraoxide sample of Example 1 at different magnifications;

[0029] Figure 3 , Figure 4 1 is a SEM image of the manganese tetraoxide sample of Comparative Example 1 at different magnifications;

[0030] Figure 5 , Figure 6 These are SEM images of the trimanganese tetraoxide sample of Comparative Example 3 at different magnifications. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

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

[0034] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the implementation regulations of this application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0035] The terms used in the embodiments of the present application are only for the purpose of describing specific implementation rules, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the implementation rules of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0036] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0037] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0038] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0040] The technical solution of the present application is illustrated below through specific embodiments and comparative examples.

[0041] In order to enable the above implementation details and operations of the present application to be clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the embodiments of the present application, the above technical solutions are illustrated by means of multiple embodiments below.

[0042] Embodiment 1:

[0043] A preparation method and application of modified "sea urchin type" manganese tetraoxide, comprising the following steps:

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

[0045] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 200g / L manganese sulfate solution, 20wt% ammonia solution and 30g / L nitrilotriacetic acid solution were added to the reactor in parallel, air was used as the oxidant, the reaction temperature was 70°C, the reaction pH was 9.0, the concentration of nitrilotriacetic acid in the system was 10g / L, the reaction time was 9h, and the mixed solution was washed, filtered and dried to obtain a primary crystal size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0046] S3 "sea urchin type" manganese tetraoxide surface modification. In a reactor, the manganese tetraoxide product is mixed with water, 30g / L nitrilotriacetic acid solution and hexadecyltrimethyl quaternary ammonium 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 6g / L, and the temperature is 70°C. A 2.2mol / L mixed metal sulfate solution (the molar ratio of Mn:Al is 10:3), a 20wt% ammonia solution, and a 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, and air is used as an oxidant. The reaction temperature is 70°C, the reaction pH is 8.5, the concentration of nitrilotriacetic acid is 6g / L, and the concentration equipment is turned on to make the solid content of the manganese tetraoxide material 21%, and the reaction time is 15h. The mixed solution is filtered, washed and dried to obtain the modified "sea urchin type" manganese tetraoxide.

[0047] The modified "sea urchin type" manganese tetraoxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained after crushing and grading.

[0048] Embodiment 2:

[0049] A preparation method and application of modified "sea urchin type" manganese tetraoxide, comprising the following steps:

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

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

[0052] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 200g / L manganese sulfate solution, 20wt% ammonia solution and 30g / L ethylenediaminetetraacetic acid tetrasodium solution were added to the reactor in parallel, air was used as the oxidant, the reaction temperature was 70°C, the reaction pH was 9.0, the concentration of ethylenediaminetetraacetic acid tetrasodium in the system was 10g / L, the reaction time was 9h, and the mixed solution was washed, filtered and dried to obtain a primary grain size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0053] S3 "sea urchin type" surface modification of manganese tetraoxide. In a reactor, the manganese tetraoxide product is mixed with water, 30g / L nitrilotriacetic acid solution and sodium dodecylbenzene sulfonate 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 6g / L, and the temperature is 70°C. A 2.2mol / L mixed metal sulfate solution (Mn:Al:Zn=10:2.5:0.1), a 20wt% ammonia solution, and a 30g / L tetrasodium ethylenediaminetetraacetic acid solution are added to the reactor in parallel, and air is used as an oxidant. The reaction temperature is 70°C, the reaction pH is 8.5, the concentration of tetrasodium ethylenediaminetetraacetic acid is 6g / L, and the concentration equipment is turned on to make the solid content of the manganese tetraoxide material 21%, and the reaction time is 15h. The mixed solution is filtered, washed and dried to obtain the modified "sea urchin type" manganese tetraoxide.

[0054] The modified "sea urchin type" manganese tetraoxide and lithium carbonate were mixed evenly at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained after crushing and grading.

[0055] Embodiment 3:

[0056] A preparation method and application of modified "sea urchin type" manganese tetraoxide, comprising the following steps:

[0057] The present invention is different from Example 1 in that the concentrations of manganese sulfate and ammonia water, the reaction pH and the solid content are changed.

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

[0059] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 120g / L manganese sulfate solution, 25wt% ammonia solution and 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, air is used as the oxidant, the reaction temperature is 70°C, the reaction pH is 8.8, the concentration of nitrilotriacetic acid in the system is 10g / L, the reaction time is 6-15h, and the mixed solution is washed, filtered and dried to obtain a primary grain size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0060] S3 Surface modification of "sea urchin type" manganese tetraoxide. In a reactor, the manganese tetraoxide product is mixed with water, 30g / L nitrilotriacetic acid solution and hexadecyltrimethyl quaternary ammonium bromide in a mass ratio of 1:2.3:0.1:0.1 to prepare a mixed solution with a solid content of 30% and a complexing agent concentration of 6g / L, and the temperature is 70°C. A 2.2mol / L mixed metal sulfate solution (the molar ratio of Mn:Al is 10:3), a 25wt% ammonia solution, and a 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, and air is used as an oxidant. The reaction temperature is 70°C, the reaction pH is 8.6, the concentration of nitrilotriacetic acid is 6g / L, and the concentration equipment is turned on to make the solid content of the manganese tetraoxide material 25%, and the reaction time is 15h. The mixed solution is filtered, washed and dried to obtain the modified "sea urchin type" manganese tetraoxide.

[0061] The manganese tetraoxide and lithium carbonate were uniformly mixed at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained through crushing and classification.

[0062] Comparative Example 1:

[0063] A preparation method and application of manganese tetraoxide, comprising the following steps:

[0064] The difference between this comparative example and Example 1 is that there is no S3 manganese tetraoxide surface modification step.

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

[0066] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 200g / L manganese sulfate solution, 20wt% ammonia solution and 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, air is used as the oxidant, the reaction temperature is 70°C, the reaction pH is 9.0, the concentration of nitrilotriacetic acid in the system is 10g / L, the reaction time is 6-15h, and the mixed solution is washed, filtered and dried to obtain a primary grain size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0067] Comparative Example 2:

[0068] A preparation method and application of manganese tetraoxide, comprising the following steps:

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

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

[0071] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 200g / L manganese sulfate solution, 30% NaOH solution and 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, air is used as the oxidant, the reaction temperature is 70°C, the reaction pH is 9.0, the concentration of nitrilotriacetic acid in the system is 10g / L, the reaction time is 6-15h, and the mixed solution is washed, filtered and dried to obtain a primary crystal size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0072] S3 Surface modification of "sea urchin type" manganese tetraoxide. In a reactor, the manganese tetraoxide product is mixed with water, 30g / L nitrilotriacetic acid solution and hexadecyltrimethyl quaternary ammonium 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 6g / L, and the temperature is 70°C. A 2.2M mixed metal sulfate solution (the molar ratio of Mn:Al is 10:3), a 30% NaOH solution, and a 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, and air is used as an oxidant. The reaction temperature is 70°C, the reaction pH is 8.5, the concentration of nitrilotriacetic acid is 6g / L, and the concentration equipment is turned on to make the solid content of the manganese tetraoxide material 21%, and the reaction time is 15h. The mixed solution is filtered, washed and dried to obtain the modified "sea urchin type" manganese tetraoxide. The manganese tetraoxide and lithium carbonate were uniformly mixed at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained through crushing and classification.

[0073] The manganese tetraoxide and lithium carbonate were uniformly mixed at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained through crushing and classification.

[0074] Comparative Example 3:

[0075] A preparation method and application of manganese tetraoxide, comprising the following steps:

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

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

[0078] S2 Preparation of "sea urchin type" manganese tetraoxide. The base liquid, 200g / L manganese sulfate solution, 20wt% ammonia solution and 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, air is used as the oxidant, the reaction temperature is 70°C, the reaction pH is 9.0, the concentration of nitrilotriacetic acid in the system is 10g / L, the reaction time is 6-15h, and the mixed solution is washed, filtered and dried to obtain a primary grain size of 300-700nm and a truncated octahedral "sea urchin type" manganese tetraoxide.

[0079] S3 "sea urchin type" manganese tetraoxide surface modification. In a reactor, the manganese tetraoxide product is mixed with water, 30g / L nitrilotriacetic acid solution and hexadecyltrimethyl quaternary ammonium 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 6g / L, and the temperature is 70°C. A 2.2M mixed metal sulfate solution (the molar ratio of Mn:Al is 10:3), a 20wt% ammonia solution, and a 30g / L nitrilotriacetic acid solution are added to the reactor in parallel, and air is used as an oxidant. The reaction temperature is 70°C, the reaction pH is 8.5, the concentration of nitrilotriacetic acid is 6g / L, and the concentration equipment is turned on to make the solid content of the manganese tetraoxide material 8%, and the reaction time is 15h. The mixed solution is filtered, washed and dried to obtain the modified "sea urchin type" manganese tetraoxide. The manganese tetraoxide and lithium carbonate were uniformly mixed at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained through crushing and classification.

[0080] The manganese tetraoxide and lithium carbonate were uniformly mixed at a molar ratio of Li / Mn of 0.53, calcined at 780° C. for 12 h in an air atmosphere, and the lithium manganate product was obtained through crushing and classification.

[0081] SEM comparison of manganese tetraoxide particles of Example 1 and Comparative Example 1 Figure 1 , 2 and Figure 3 , 4 As shown, it can be found that Comparative Example 1 is a "sea urchin-type" manganese tetraoxide sample, and the primary crystals are truncated octahedrons of about 600 nm, while Example 1 forms a coating layer on the surface of the "sea urchin-type" manganese tetraoxide sample. SEM comparison of manganese tetraoxide particles in Example 1 and Comparative Example 3 Figure 1 , 2 and Figure 5 , 6 As shown, it can be seen that when the content of trimanganese tetraoxide in the system is low, there is a tendency for a coating layer to form on the particle surface, but an obvious ridge structure can be seen. Therefore, the ammonia water and aminocarboxylic acid complexing agent used in the present invention are conducive to the growth of primary crystals, and a trimanganese tetraoxide product with larger primary crystals can be prepared. Moreover, through the violent collision between particles in an environment with a high solid content, a coating layer is in situ grown on the surface of the "sea urchin-type" trimanganese tetraoxide, constructing an obvious core-shell structure.

[0082] Performance test: With lithium sheet as negative electrode, the lithium manganate positive electrode material prepared in the embodiment and comparative example as positive electrode, a secondary button battery of model CR2025 is prepared. At a voltage of 3.0-4.2V, first 0.2C charge / 0.2C discharge for two cycles, and then a cyclic discharge test is carried out under 1C charge / 1C discharge conditions to test the first charge and discharge efficiency and 1C first discharge capacity. The test results are shown in Table 1: Compared with comparative example 1, the discharge capacity and capacity retention rate of embodiments 1-3 are significantly improved, which is mainly due to the fact that the modified manganese tetraoxide has an in-situ coating layer, which can reduce the dissolution of manganese, and the intact small grains inside the coating layer are conducive to the diffusion of lithium ions, which can increase the capacity of lithium manganate. The capacity retention rate of embodiment 1 is higher than that of comparative example 2, which shows that the use of ammonia water as a precipitant and an aminocarboxylic acid chelating agent as a complexing agent can improve the crystallinity of manganese tetraoxide and promote the formation of large-particle crystals, which is conducive to reducing the dissolution of manganese and the corrosion of the electrolyte, and improving the capacity retention rate of lithium manganate. The discharge capacity and capacity retention rate 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 collision between particles is not intense enough during the modification process, a large number of small octahedral primary grains exist on the surface of the particles, and an obvious coating layer cannot be constructed, which leads to the still obvious dissolution effect of manganese and a relatively low capacity retention rate.

[0083] Table 1: Performance test results of the embodiments

[0084]

[0085]

[0086] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0087] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for preparing modified "sea urchin type" manganese tetraoxide, characterized in that: The following steps are involved: S1. Prepare base liquid: mix water, precipitant and complexing agent to prepare base liquid; S2, preparing manganese tetraoxide: adding manganese sulfate, a precipitant and a complexing agent to the base liquid, filtering, washing and drying after the reaction to obtain "sea urchin type" manganese tetraoxide; S3. Surface modification of trimanganese tetraoxide: the trimanganese tetraoxide is mixed with water, a complexing agent and a dispersant in a reaction kettle; at the same time, a mixed metal salt solution, a complexing agent and a precipitant are added to the reaction kettle in parallel, and concentrated to make the solid content of trimanganese tetraoxide reach a set value. After the reaction, the trimanganese tetraoxide is filtered, washed and dried to obtain modified "sea urchin type" trimanganese tetraoxide.

2. The preparation method according to claim 1, characterized in that: 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 a combination of one or more 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 nitrilotriacetic acid.

3. The preparation method according to claim 1, characterized in that: 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 base solution is 8.8-9.

5.

4. The preparation method according to claim 1, characterized in that: The reaction conditions in S2 are: air or oxygen as oxidant, pH=8.5-9.2, reaction temperature 50-80°C, reaction time 6-15h.

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

6. The preparation method according to claim 1, characterized in that: The mass ratio of trimanganese tetraoxide, 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 mixed metal salt solution in S3 is a mixture of manganese sulfate solution and other metal salt solutions, the other metals are a combination of one or more 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 manganese sulfate is 1:0.01-0.5; the concentrated manganese tetraoxide has a solid content of ≥15%; the dispersant in S3 is: hexadecyltrimethylammonium bromide, sodium stearate, polyethylene glycol, sodium lauryl polyether sulfate, sodium dodecylbenzene sulfonate, etc.

8. The preparation method according to claim 1, characterized in that: The reaction conditions in S3 are: air or oxygen as oxidant, pH=8.0-8.7, reaction temperature 60-80°C, reaction time 10-18h.

9. An application of the modified "sea urchin type" manganese tetraoxide as claimed in claim 1, characterized in that: Used to prepare lithium manganese oxide positive electrode material products.

10. The use according to claim 9, characterized in that: The method for preparing lithium manganate products is: adding modified "sea urchin type" manganese tetraoxide and lithium carbonate in a molar ratio of Li / Mn of 0.53:1, calcining at 750-780°C for 12-24h in an air atmosphere, and obtaining a lithium manganate positive electrode material product after crushing and grading.

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