Method for preparing sphere-like battery grade manganous-manganic oxide

Abstract

The invention discloses a method for preparing sphere-like battery grade manganous-manganic oxide, manganous-manganic oxide is directly obtained through a one-step method, and meanwhile, on-line changes of parameters of manganous-manganic oxide crystals in different growth stages are specifically controlled and changed according to growth characteristics of manganous-manganic oxide crystal particles. And the growth process of the manganous-manganic oxide crystal is regulated and controlled, so that the particle size of the product is controlled, the shape of the product is optimized, and finally the manganous-manganic oxide product with uniform and controllable particle size and good morphological characteristics is obtained. Besides, according to the invention, a corresponding scheme can be formulated according to the particle size of a target product to obtain a product meeting the requirement, and the fine control of the Mn3O4 preparation process is realized. The method has the advantages of short process, simplicity in operation, low energy consumption and the like.

Description

Technical Field

[0001] The invention relates to the preparation of battery materials, in particular to a method for preparing spherical battery-grade manganese tetraoxide, and belongs to the technical field of battery material production and preparation. Background Art

[0002] In recent years, with the development of green industries such as new energy vehicles, lithium manganese oxide (LiMn2O4) as a positive electrode material for power lithium-ion batteries has attracted more and more attention due to its advantages such as low price, good safety performance and no pollution to the environment. At present, the production of lithium manganese oxide mainly uses electrolytic manganese dioxide as the manganese source, and solid-phase sintering with lithium carbonate and corresponding additives. Due to the defects of electrolytic manganese dioxide such as poor particle morphology, the prepared lithium manganese oxide material has problems such as low gram capacity, poor cycle performance and poor high temperature performance. Mn3O4 and LiMn2O4 have the same spinel structure. When LiMn2O4 is prepared from Mn3O4, no drastic structural changes will occur, and the material structure is more stable; the prepared LiMn2O4 has better electrochemical properties, and the gram capacity, high temperature performance, cycle performance and other aspects have been significantly improved: Therefore, using Mn3O4 to replace electrolytic manganese dioxide to produce LiMn2O4 is the current development trend.

[0003] The preparation methods of Mn3O4 mainly include roasting method, reduction method, oxidation method, manganese salt method, etc. At present, the metal manganese powder suspension oxidation method is mostly used. This method is relatively mature, but the production cost is high, the purity is low, and the particle size is uneven. In recent years, the manganese salt method has attracted widespread attention due to the advantages of low raw material cost. The preparation of Mn3O4 by the manganese salt method is usually carried out in two steps. The first step is to add an alkaline precipitant to the manganese salt to obtain Mn(OH)2 precipitation. After filtering and washing, Mn(OH)2 is slurried and oxidized to obtain Mn3O4 particles. The two-step oxidation method requires the use of inert gas for protection throughout the preparation stage of Mn(OH)2. The process flow is relatively complex, and the product morphology and particle size are also difficult to control. Since the particle size, morphology, impurity content and other indicators of the manganese source directly affect the electrical properties of lithium manganate materials, it is of great significance to develop a battery-grade manganese tetraoxide preparation method with a short process, simple operation and controllable particle size in view of the various deficiencies in the prior art. Summary of the invention

[0004] In view of the problem in the prior art that the existing manganese salt method for preparing Mn3O4 has the problem that the product morphology and particle size are difficult to control, which leads to the influence on the electrical properties of the electrode material, the present invention provides a method for preparing quasi-spherical battery-grade manganese tetraoxide, in which manganese tetraoxide is directly obtained by a one-step method, and at the same time, according to the growth characteristics of manganese tetraoxide crystal particles, the online changes of parameters of manganese tetraoxide crystals at different growth stages are targetedly controlled and changed, thereby regulating the growth process of manganese tetraoxide crystals, thereby controlling the product particle size and optimizing its shape, and finally obtaining a manganese tetraoxide product with uniform and controllable particle size and good morphological characteristics.

[0005] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0006] A method for preparing spherical battery-grade manganese tetraoxide, the method comprising:

[0007] 1) A primary judgment model of the flow rate of the ammonia solution to be introduced once is established according to the target particle size of the product, the concentration of the manganese salt solution, the predetermined flow rate of the manganese salt solution per unit time, and the concentration of the ammonia solution, and the flow rate of the ammonia solution to be introduced once per unit time in a stirring reaction is obtained according to the primary judgment model. Deionized water is added to a reaction vessel and heated as a reaction base liquid, and then the manganese salt solution is added to the reaction vessel under the condition of the participation of an oxidant, and the ammonia solution is simultaneously added according to the obtained flow rate to be introduced once to carry out a stirring reaction.

[0008] 2) According to the target particle size of the product, the concentration of the manganese salt solution, the predetermined flow rate of the manganese salt solution per unit time, the concentration of the ammonia solution, the flow rate of the ammonia solution once, the stirring rate of the first stirring reaction, and the predetermined stirring rate of the second stirring reaction, a calculation model and a secondary judgment model for the flow rate of the ammonia solution twice should be established, and the flow rate of the ammonia solution twice per unit time in the second stirring reaction is obtained according to the calculation model and the secondary judgment model. After the first stirring reaction is completed, the rate is adjusted and the real-time flow rate of the ammonia solution is adjusted according to the obtained second flow rate to be introduced, and then the second stirring reaction is carried out.

[0009] 3) After the secondary stirring reaction is completed, the stirring rate is reduced and the addition of the manganese salt solution and the ammonia solution is stopped until the reaction is completed. The solid product after the reaction is separated, and the solid product is sequentially washed and dried to obtain a battery-grade manganese tetraoxide product.

[0010] Preferably, in step 1), the primary judgment model is:

[0011] a) When D<10μm, 0.2≤(V2·C2) / (V1·C1)≤0.8 per unit time.

[0012] b) When 10 μm ≤ D ≤ 25 μm, 2.0 ≤ (V2·C2) / (V1·C1) ≤ 3.2 per unit time.

[0013] Wherein, D is the D50 of the target product, in μm. C1 is the concentration of the manganese salt solution, in mol / L. C2 is the concentration of the ammonia water solution, in mol / L. V1 is the predetermined feeding flow rate of the manganese salt solution, in L / h. V2 is the primary feeding flow rate of the ammonia water solution, in L / h.

[0014] Preferably, in step 2), the calculation model is:

[0015] D = [1453C2V2(8846 + r2) + 48038C2V x (8102 + r1)] / [(8102 + r1)(8846 + r2)C1V1] - 0.305(1)

[0016] D1 = kD (2)

[0017] In formula (1), D is the D50 of the target product, in μm. C1 is the concentration of the manganese salt solution, in mol / L. C2 is the concentration of the ammonia water solution, in mol / L. V1 is the predetermined feeding flow rate of the manganese salt solution, in L / h. V2 is the primary feeding flow rate of the ammonia water solution, in L / h. V x is the secondary feeding flow rate of the ammonia water solution, in L / h. r1 is the stirring rate during the primary stirring reaction, in r / min. r2 is the stirring rate during the secondary stirring reaction, in r / min. In formula (2), D1 is the actual measured value of the product D50, in μm. k is the error coefficient, with a value range of 0.95 - 1.05. The reliability of the above formula is judged based on the value of k.

[0018] Preferably, the secondary judgment model is:

[0019] c) When D ≤ 5 μm, 0.4 ≤ (V x ·C2) / (V1·C1) ≤ 1.0 per unit time.

[0020] d) When 5 μm < D ≤ 10 μm, 1.2 ≤ (V x ·C2) / (V1·C1) ≤ 2.0 per unit time.

[0021] e) When 10 μm < D ≤ 25 μm, 2.5 ≤ (V x ·C2) / (V1·C1) ≤ 4.0 per unit time.

[0022] And in c), d), and e): (V x ·C2) / (V1·C1) - (V2·C2) / (V1·C1) ≥ 0.2.

[0023] Preferably, in step 1), the manganese salt solution is one or more of manganese sulfate solution, manganese chloride solution, manganese nitrate solution, and manganese acetate solution, preferably manganese sulfate solution.

[0024] Preferably, in step 1), the oxidant is one or more of air, oxygen, ozone, preferably oxygen (it should be noted that the oxygen generally refers to an oxygen-containing gas having an oxygen content greater than that of air, preferably an oxygen-containing gas having an oxygen content of not less than 50%, and further preferably an oxygen-containing gas having an oxygen content of not less than 80%, such as pure oxygen).

[0025] Preferably, in step 1), the concentration of the manganese salt solution is 1 to 5 mol / L, preferably 1.5 to 4.5 mol / L, more preferably 2 to 4 mol / L. The predetermined flow rate of the manganese salt solution is 1 to 10 L / h, preferably 1.5 to 8 L / h, more preferably 2 to 6 L / h.

[0026] Preferably, in step 1), the concentration of the aqueous ammonia solution is 1 to 5 mol / L, preferably 1.5 to 4.5 mol / L, and more preferably 2 to 4 mol / L.

[0027] Preferably, in step 1), the heating is to heat the reaction base liquid to 45-85°C, preferably 50-80°C, more preferably 55-75°C.

[0028] Preferably, in step 1), the manganese salt solution and the ammonia solution are preheated independently before being added to the reaction vessel. Preferably, the temperature of the manganese salt solution and the ammonia solution after preheating is consistent with the temperature of the reaction base solution after heating.

[0029] Preferably, in step 1), the stirring rate during the stirring reaction is not less than 400 r / min, preferably 600-800 r / min, more preferably 650-750 r / min. The duration of the stirring reaction is not more than 8 h, preferably 1-6 h, more preferably 2-4 h.

[0030] Preferably, in step 2), the stirring rate during the secondary stirring reaction is not less than 200 r / min, preferably 400-800 r / min, more preferably 450-700 r / min. The duration of the secondary stirring reaction is not less than 2 h, preferably 3-24 h, more preferably 5-20 h.

[0031] It should be noted that the increase in stirring rate will inhibit the adhesion of solute particles and the agglomeration of fine grains, thereby inhibiting the growth of secondary particles. Therefore, when preparing products with larger particle sizes, it is generally necessary to appropriately reduce the secondary stirring rate.

[0032] Preferably, in step 3), the stirring rate after reducing the stirring rate is not higher than 500 r / min, preferably 100 to 400 r / min, more preferably 150 to 300 r / min.

[0033] Preferably, in step 3), the washing is performed with deionized water, preferably 1 to 10 times with deionized water, more preferably 2 to 8 times with deionized water.

[0034] In the present invention, a manganese tetraoxide product with a target particle size is directly prepared by a one-step method. First, a manganese salt solution of a certain concentration (for example, a manganese sulfate solution with a concentration of 1 to 5 mol / L, generally prepared by adding high-purity monohydrate manganese sulfate solid to deionized water) and an ammonia solution of a certain concentration (for example, an ammonia solution with a concentration of 1 to 5 mol / L, generally prepared by adding concentrated ammonia water to deionized water) are prepared, and then they are continuously added to a reactor at a certain flow rate for a preliminary reaction, and an oxidant is added during the reaction (for example, pure oxygen is continuously introduced); after the preliminary reaction is completed (for example, after stirring the reaction for 2 to 5 hours), according to the size of the target particle size of the product, the real-time addition amount of ammonia water is selectively adjusted and then the reaction is carried out to obtain a manganese tetraoxide product with a target particle size, uniform morphology and extremely low impurity content.

[0035] In the present invention, a sufficient amount of deionized water is added to the reactor as a base liquid in advance and preheated to the reaction temperature, the purpose of which is to control the reaction temperature to the set temperature; further, the manganese salt solution and the ammonia solution are also preheated to the reaction temperature before the reaction, the purpose of which is to reduce the impact of large temperature changes on the reaction.

[0036] In the present invention, a one-step method is used to directly obtain Mn3O4, and the reactions occurring during the preparation process are mainly:

[0037] 6Mn 2+ +O2+12NH3·H2O=2Mn3O4+12NH4 + +6H2O

[0038] During the reaction, Mn 2+ Under the action of oxidant, Mn3O4 and H + Ammonia has two main functions in the system. One is to neutralize the H generated in the solution. + , to avoid the continuous decrease of system pH, which would affect the physical phase and reaction rate of the product; secondly, with Mn 2+ Coordinate to form complexes and regulate the system Mn 2+ In this method, which is a one-step process, by controlling the appropriate reaction conditions, Mn 2+It is directly oxidized to Mn3O4. This method has a short process and simple operation. The particle size of the obtained product is controllable, the morphology is uniform and good, and the impurity content is extremely low.

[0039] In the present invention, the growth process of Mn3O4 crystals in the reaction solution mainly undergoes the following processes. First, the monomer concentration gradually increases to a saturated state in the system; when the monomer concentration exceeds a certain limit, a large amount of nucleation begins, and this process is the nucleation stage; then the monomer concentration drops sharply, and the nucleation reaction ends; after nucleation, the nanoparticles continue to grow through diffusion between monomer molecules until a complete crystal structure is finally formed. Since different growth stages of crystals have different characteristics, the experimental parameters have different effects on their growth in this process. Therefore, the crystal nucleation and growth process is refined and designed, and the particle size and shape of the product are regulated by fine control of the process parameters. In other words, the present invention divides the growth of Mn3O4 into multiple stages, and controls the Mn3O4 product of the target particle size by finely regulating the temperature, stirring speed, and liquid inlet flow rate of each stage, and optimizes its shape.

[0040] In the present invention, under given working conditions, the particle size of the product is controlled mainly by controlling the flow rate of ammonia water at different stages of the reaction, and at the same time, a corresponding plan can be formulated according to the particle size of the target product to obtain a product that meets the requirements, thereby achieving refined control of the Mn3O4 preparation process. The main process is: set D to be the D50 of the target product, μm. C1 is the concentration of the manganese salt solution, mol / L. C2 is the concentration of the ammonia solution, mol / L. V1 is the initial addition rate of the manganese salt solution, L / h. V2 is the initial addition rate of the ammonia solution, L / h. r1 is the stirring rate during the initial reaction, r / min. r2 is the stirring rate of the reaction after adjusting the flow rate of the ammonia solution, r / min. Then the addition rate V after the flow rate of the ammonia solution is adjusted x (mol / L) should satisfy the following formula:

[0041] D=[1453C2V2(8846+r2)+48038C2V x (8102+r1)] / [(8102+r1)(8846+r2)C1V1]-0.305(1)

[0042] Furthermore, in order to achieve fine control of the product particle size, during the entire reaction process, the molar ratio of the amount of ammonia water and the amount of manganese salt added per unit time in the initial reaction (i.e., the first-stage reaction) is set to m1. The molar ratio of the amount of ammonia water and the amount of manganese salt added per unit time after the amount of ammonia solution added is adjusted (i.e., the second-stage reaction) is set to m2. Then:

[0043] a) When D < 10 μm, 0.2 ≤ (V2·C2) / (V1·C1) ≤ 0.8 per unit time.

[0044] b) When 10 μm ≤ D ≤ 25 μm, 2.0 ≤ (V2·C2) / (V1·C1) ≤ 3.2 per unit time.

[0045] c) When D ≤ 5 μm, 0.4 ≤ (V x ·C2) / (V1·C1) ≤ 1.0.

[0046] d) When 5 μm < D ≤ 10 μm, 1.2 ≤ (V x ·C2) / (V1·C1) ≤ 2.0.

[0047] e) When 10 μm < D ≤ 25 μm, 2.5 ≤ (V x ·C2) / (V1·C1) ≤ 4.0.

[0048] And in c), d), and e): (V x ·C2) / (V1·C1) - (V2·C2) / (V1·C1) ≥ 0.2.

[0049] That is to say, through the above process, the actual particle size of Mn3O4 directly prepared by the one-step method in the present invention is highly matched with the target particle size D, and the product morphology is basically spherical or quasi-spherical.

[0050] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0051] 1: According to the growth characteristics of manganese tetraoxide crystal particles, the present invention precisely regulates the changes in process parameters at different growth stages of manganese tetraoxide particles, and then regulates the growth process of manganese tetraoxide crystals to achieve the goal of precisely controlling the particle size of the product and optimizing its shape. In addition, the present invention can also formulate corresponding schemes according to the particle size of the target product to obtain products that meet the requirements, realizing the refined control of the Mn3O4 preparation process.

[0052] 2: The present invention directly prepares battery-grade manganese tetraoxide products by the one-step method, which has the advantages of short process, simple operation, and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is the SEM image of the product obtained in Example 3 at ×2000.

[0054] Figure 2 It is the SEM image of the product obtained in Example 3 at ×8000.

[0055] Figure 3This is the SEM image of the product obtained in Example 3 at ×15000.

[0056] Figure 4 This is the XRD pattern of the product obtained in Example 3. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0058] Example 1

[0059] Preparation of manganese tetraoxide with a D50 of 4.0 μm:

[0060] Weigh manganese sulfate monohydrate and add an appropriate amount of deionized water to prepare a manganese sulfate solution with a concentration of 1.2 mol / L; measure concentrated ammonia water and add an appropriate amount of deionized water thereto to prepare an ammonia solution with a concentration of 1.2 mol / L.

[0061] 5 L of deionized water was added to the reactor and heated to 60 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 1.0 L / h and ammonia solution was added to the reactor at a flow rate of 0.4 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 800 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3 h.

[0062] After the initial reaction is completed, the flow rate of the ammonia solution to be adjusted is calculated according to the above parameters and formula (1), wherein the stirring rate of the secondary reaction is 800 r / min, and the flow rate of the ammonia solution after adjustment should be 0.85 L / h. After adjusting the flow rate and stirring rate of the ammonia solution, the secondary reaction is carried out for 11 hours. After the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 200 r / min, and the aging reaction is carried out for 1 hour. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0063] Example 2

[0064] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0065] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.2 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.0 mol / L.

[0066] Add 6 L of deionized water to the reactor and heat it to 70 ° C. Then, add manganese sulfate solution at a flow rate of 2.5 L / h and ammonia solution at a flow rate of 1.0 L / h to the reactor. At the same time, turn on the stirring device of the reactor (set the stirring rate to 700 r / min) and introduce sufficient pure oxygen into the reactor for preliminary reaction. The reaction time is 3 h.

[0067] After the initial reaction is completed, the flow rate of the ammonia solution to be adjusted is calculated according to the above parameters and formula (1), wherein the stirring rate of the secondary reaction is 600 r / min, and the flow rate of the ammonia solution after adjustment should be 2.42 L / h. After adjusting the flow rate and stirring rate of the ammonia solution, the secondary reaction is carried out for 10 hours. After the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 150 r / min, and the aging reaction is carried out for 1 hour. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0068] Example 3

[0069] Preparation of manganese tetraoxide with a D50 of 14.0 μm:

[0070] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to prepare a manganese sulfate solution with a concentration of 1.5 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to prepare an ammonia solution with a concentration of 3.0 mol / L.

[0071] 7 L of deionized water was added to the reactor and heated to 80 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 1.8 L / h and ammonia solution was added to the reactor at a flow rate of 2.2 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 600 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 4 h.

[0072] After the initial reaction is completed, the flow rate of the ammonia solution to be adjusted is calculated according to the above parameters and formula (1), wherein the stirring rate of the secondary reaction is 500 r / min, and the flow rate of the ammonia solution after adjustment should be 2.44 L / h. After adjusting the flow rate and stirring rate of the ammonia solution, the secondary reaction is carried out for 10 hours. After the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min, and the aging reaction is carried out for 1 hour. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0073] Example 4

[0074] Preparation of manganese tetraoxide with a D50 of 18.0 μm:

[0075] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 2.0 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 4.0 mol / L.

[0076] 8 L of deionized water was added to the reactor and heated to 75 °C. Then, manganese sulfate solution and ammonia solution were added to the reactor at a flow rate of 2.0 L / h and 2.8 L / h, respectively. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 600 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 4 h.

[0077] After the initial reaction is completed, the flow rate of the ammonia solution to be adjusted is calculated according to the above parameters and formula (1), wherein the stirring rate of the secondary reaction is 400 r / min, and the flow rate of the ammonia solution after adjustment should be 3.44 L / h. After adjusting the flow rate and stirring rate of the ammonia solution, the secondary reaction is carried out for 10 hours. After the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min, and the aging reaction is carried out for 1 hour. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0078] Example 5

[0079] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0080] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0081] 6 L of deionized water was added to the reactor and heated to 65 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 2.2 L / h and ammonia solution was added to the reactor at a flow rate of 0.9 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 700 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3.5 h.

[0082] After the initial reaction is completed, the flow rate of the ammonia solution to be adjusted is calculated according to the above parameters and formula (1), wherein the stirring rate of the secondary reaction is 600 r / min, and the flow rate of the ammonia solution after adjustment should be 2.37 L / h. After adjusting the flow rate and stirring rate of the ammonia solution, the secondary reaction is carried out for 11 hours. After the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min, and the aging reaction is carried out for 1 hour. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0083] Example 6

[0084] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0085] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0086] 6 L of deionized water was added to the reactor and heated to 65 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 2.2 L / h and ammonia solution was added to the reactor at a flow rate of 0.2 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 700 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3.5 h.

[0087] After the initial reaction is completed, the stirring rate of the secondary reaction is adjusted to 600 r / min, the flow rate of the ammonia water is adjusted to 2.37 L / h, and the duration of the secondary reaction is 11 h; after the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min and the aging reaction is carried out for 1 h. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0088] Example 7

[0089] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0090] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0091] 6 L of deionized water was added to the reactor and heated to 65 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 2.2 L / h and ammonia solution was added to the reactor at a flow rate of 1.32 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 700 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3.5 h.

[0092] After the initial reaction is completed, the stirring rate of the secondary reaction is adjusted to 600 r / min, the flow rate of the ammonia water is adjusted to 2.37 L / h, and the duration of the secondary reaction is 11 h; after the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min and the aging reaction is carried out for 1 h. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0093] Example 8

[0094] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0095] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0096] 6 L of deionized water was added to the reactor and heated to 65 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 2.2 L / h and ammonia solution was added to the reactor at a flow rate of 0.9 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 700 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3.5 h.

[0097] After the initial reaction is completed, the stirring rate of the secondary reaction is adjusted to 600 r / min, the flow rate of the ammonia water is adjusted to 1.46 L / h, and the duration of the secondary reaction is 11 h; after the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min and the aging reaction is carried out for 1 h. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0098] Example 9

[0099] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0100] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0101] 6 L of deionized water was added to the reactor and heated to 65 °C. Then, manganese sulfate solution was added to the reactor at a flow rate of 2.2 L / h and ammonia solution was added to the reactor at a flow rate of 0.9 L / h. At the same time, the stirring device of the reactor was turned on (the stirring rate was set to 700 r / min) and a sufficient amount of pure oxygen was introduced into the reactor for a preliminary reaction. The reaction time was 3.5 h.

[0102] After the initial reaction is completed, the stirring rate of the secondary reaction is adjusted to 600 r / min, the flow rate of the ammonia water is adjusted to 3.52 L / h, and the duration of the secondary reaction is 11 h; after the secondary reaction is completed, the addition of the manganese sulfate solution and the ammonia solution is stopped, the stirring rate is reduced to 100 r / min and the aging reaction is carried out for 1 h. After the aging is completed, the reaction slurry is filtered, and the solid product is washed 3 times with deionized water and then dried to obtain the manganese tetraoxide product.

[0103] Comparative Example 1

[0104] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0105] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0106] The prepared manganese sulfate solution and ammonia solution were added to the reactor at a volume ratio of 1:1 at one time, the reaction temperature was 65°C, and after the precipitation was completed, air was introduced through an oxygen pump, the oxidation pH was controlled at 7-8, and the oxidation time was 4 hours. After the reaction was completed, the reaction slurry was filtered, the solid product was washed 3 times with deionized water, and then dried to obtain the manganese tetraoxide product.

[0107] Comparative Example 2

[0108] Preparation of manganese tetraoxide with a D50 of 8.0 μm:

[0109] Manganese sulfate monohydrate was weighed and an appropriate amount of deionized water was added to obtain a manganese sulfate solution with a concentration of 1.4 mol / L; concentrated ammonia water was measured and an appropriate amount of deionized water was added thereto to obtain an ammonia solution with a concentration of 2.1 mol / L.

[0110] 6L of deionized water was added to the reactor and heated to 65°C, and then the trimanganese tetraoxide prepared in Example 1 was added to the reactor as a seed, and manganese sulfate solution was added at a flow rate of 2.2L / h and ammonia solution was added at a flow rate of 2.37L / h, and the stirring device of the reactor was turned on (the stirring rate was set to 600r / min) and a sufficient amount of pure oxygen was passed into the reactor to react, and the reaction time was 11h. After the reaction was completed, the addition of manganese sulfate solution and ammonia solution was stopped, the stirring rate was reduced to 100r / min for aging reaction for 1h, and after aging, the reaction slurry was filtered, and the solid product was washed 3 times with deionized water and then dried to obtain trimanganese tetraoxide product.

[0111] The manganese tetraoxide products obtained in each embodiment and comparative example were tested, and the performance data of each product were compared as follows:

[0112]

[0113] Application Examples

[0114] The manganese tetraoxide prepared in each embodiment and comparative example was fully mixed with lithium carbonate, wherein the lithium content was 5%. The mixed powder was pre-calcined at 500°C for 5 hours and then calcined at 800°C for 10 hours to obtain an iron-doped lithium manganate positive electrode material. Then, button cells were prepared using the lithium manganate positive electrode material as a raw material, and their electrochemical properties were tested as shown below:

[0115]

[0116]

[0117] In summary, the present invention can accurately produce a manganese tetraoxide product with controllable particle size according to the coupling of the primary judgment model and the secondary judgment model combined with the ammonia adjustment calculation model, that is, by regulating the growth process of the manganese tetraoxide crystals, the particle size of the product is controlled and its shape is optimized, and finally a manganese tetraoxide product with uniform and controllable particle size and good morphological characteristics is obtained, thereby realizing refined control of the Mn3O4 preparation process, which is beneficial to promoting and improving the effectiveness of Mn3O4 materials in lithium manganate materials.

Claims

1. A method for preparing spherical battery-grade manganese tetraoxide, characterized in that: The method includes: 1) establishing a primary judgment model of the flow rate of the ammonia solution to be introduced once according to the target particle size of the product, the concentration of the manganese salt solution, the predetermined flow rate of the manganese salt solution per unit time, and the concentration of the ammonia solution, and obtaining the flow rate of the ammonia solution to be introduced once per unit time in a stirring reaction according to the primary judgment model; adding deionized water to a reaction container and heating it as a reaction base liquid, and then adding the manganese salt solution to the reaction container under the condition of the participation of an oxidant, and simultaneously adding the ammonia solution according to the obtained flow rate to be introduced once to carry out a stirring reaction; 2) establishing a calculation model and a secondary judgment model for the secondary flow rate of the ammonia solution according to the target particle size of the product, the concentration of the manganese salt solution, the predetermined flow rate of the manganese salt solution per unit time, the concentration of the ammonia solution, the primary flow rate of the ammonia solution, the stirring rate of the primary stirring reaction, and the predetermined stirring rate of the secondary stirring reaction, and obtaining the secondary flow rate of the ammonia solution per unit time in the secondary stirring reaction according to the calculation model and the secondary judgment model; after the primary stirring reaction is completed, adjusting the rate and adjusting the real-time flow rate of the ammonia solution according to the obtained secondary flow rate to be introduced, and then conducting a second stirring reaction; 3) After the secondary stirring reaction is completed, the stirring rate is reduced and the addition of the manganese salt solution and the ammonia solution is stopped until the reaction is completed; the solid product after the reaction is separated, and the solid product is sequentially washed and dried to obtain a battery-grade manganese tetraoxide product.

2. The method according to claim 1, characterized in that: In step 1), the primary judgment model is: a) When D<10μm, 0.2≤(V2·C2) / (V1·C1)≤0.8 per unit time; b) When 10μm≤D≤25μm, 2.0≤(V2·C2) / (V1·C1)≤3.2 per unit time; Wherein, D is the D50 of the target product, μm; C1 is the concentration of the manganese salt solution, mol / L; C2 is the concentration of the ammonia solution, mol / L; V1 is the predetermined flow rate of the manganese salt solution, L / h; V2 is the one-time flow rate of the ammonia solution, L / h.

3. The method according to claim 1 or 2, characterized in that: In step 2), the calculation model is: D=[1453C2V2(8846+r2)+48038C2V x (8102+r1)] / [(8102+r1)(8846+r2)C1V1]-0.305 (1) In formula (1), D is the D50 of the target product, μm; C1 is the concentration of the manganese salt solution, mol / L; C2 is the concentration of the ammonia solution, mol / L; V1 is the predetermined flow rate of the manganese salt solution, L / h; V2 is the flow rate of the ammonia solution once introduced, L / h; V x is the secondary flow rate of ammonia solution, L / h; r1 is the stirring rate during the first stirring reaction, r / min; r2 is the stirring rate during the second stirring reaction, r / min; The secondary judgment model is: c) When D≤5μm, 0.4≤(V x ·C2) / (V1·C1)≤1.0; d) When 5μm < D ≤ 10μm, 1.2 ≤ (V x ·C2) / (V1·C1) ≤ 2.0 within a unit time; e) When 10 μm < D ≤ 25 μm, 2.5 ≤ (V x ·C2) / (V1·C1) ≤ 4.0 within a unit time; And in c), d), e): (V x ·C2) / (V1·C1)-(V2·C2) / (V1·C1)≥0.

2.

4. The method according to any one of claims 1 to 3, characterized in that: In step 1), the manganese salt solution is one or more of manganese sulfate solution, manganese chloride solution, manganese nitrate solution, and manganese acetate solution, preferably manganese sulfate solution; and / or In step 1), the oxidant is one or more of air, oxygen and ozone, preferably oxygen.

5. The method according to any one of claims 1 to 4, characterized in that: In step 1), the concentration of the manganese salt solution is 1 to 5 mol / L, preferably 1.5 to 4.5 mol / L, more preferably 2 to 4 mol / L; the predetermined flow rate of the manganese salt solution is 1 to 10 L / h, preferably 1.5 to 8 L / h, more preferably 2 to 6 L / h; and / or In step 1), the concentration of the aqueous ammonia solution is 1 to 5 mol / L, preferably 1.5 to 4.5 mol / L, and more preferably 2 to 4 mol / L.

6. The method according to any one of claims 1 to 5, characterized in that: In step 1), the heating is to heat the reaction base liquid to 45-85°C, preferably 50-80°C, more preferably 55-75°C.

7. The method according to any one of claims 1 to 6, characterized in that: In step 1), the manganese salt solution and the ammonia solution are independently preheated before being added to the reaction vessel; preferably, the temperature of the manganese salt solution and the ammonia solution after preheating is consistent with the temperature of the reaction base solution after heating.

8. The method according to any one of claims 1 to 7, characterized in that: In step 1), the stirring rate during one stirring reaction is not less than 400 r / min, preferably 600-800 r / min; the duration of one stirring reaction is not more than 8 h, preferably 1-6 h.

9. The method according to any one of claims 1 to 8, characterized in that: In step 2), the stirring rate during the secondary stirring reaction is not less than 200 r / min, preferably 400-800 r / min; the duration of the secondary stirring reaction is not less than 2 h, preferably 3-24 h.

10. The method according to any one of claims 1 to 9, characterized in that: In step 3), the stirring rate after reducing the stirring rate is not higher than 500 r / min, preferably 100 to 400 r / min, more preferably 100 to 200 r / min; and / or In step 3), the washing is performed with deionized water, preferably 1 to 10 times with deionized water, more preferably 2 to 8 times with deionized water.

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