Method for preparing special high-purity manganous-manganic oxide for high-end lithium manganate from manganese sulfate

Abstract

The invention belongs to the technical field of new energy materials, and discloses a method for preparing special high-purity manganous-manganic oxide for high-end lithium manganate from manganese sulfate, which is characterized in that manganese sulfate is used as a raw material, seed crystals are prepared firstly and then subjected to oxidative synthesis to enable the seed crystals to grow slowly, any additive is not needed, complex procedures such as roasting, crushing and the like are removed, and the method is suitable for industrial production. The manganous-manganic oxide particles with different particle sizes can be prepared, the prepared manganous-manganic oxide product is high in sphericity degree, controllable in particle size distribution, high in tap density and low in specific surface area, and the process has the advantages of being high in automation degree, improving the physical and chemical properties of manganous-manganic oxide, reducing the impurity content in the product and the like.

Description

Technical Field

[0001] The invention belongs to the field of new materials and relates to the preparation of high-purity manganese tetraoxide, a special positive electrode material for high-end lithium manganate. Background Art

[0002] Lithium manganate is one of the most promising lithium-ion cathode materials. It has the advantages of abundant preparation materials, no pollution, low cost, high safety, and good rate performance. It is an ideal cathode material for power batteries. At present, domestic lithium manganate manufacturers mainly use electrolytic manganese dioxide as the manganese source. However, studies have shown that the electrochemical performance of lithium manganate prepared with manganese tetraoxide as the manganese source is better than that with electrolytic manganese dioxide as the manganese source. Its electrical properties such as capacity, rate, and cycle life have been significantly improved. The performance of lithium manganate prepared with manganese tetraoxide of different indicators as the manganese source is also very different. The tap density of the manganese source is an important influencing factor. "Cao Yalei, Zou Xing. Effect of different apparent density Mn3O4 on the performance of LiMn2O4 cathode materials [J]. Materials Science, 2019, 9(7): 684-690. DOl: 10.12677 / ms.2019.97086." Relevant research has been done on this.

[0003] At present, the production methods of manganese tetraoxide on the market mainly include: using metallic manganese as raw material, oxidation production, and the technical principle is derived from the US patent (US4812302). The main problems of the process are: low technical content, high production cost, poor economic benefit, uneven particle size, large particle size, and generally high content of various impurities; the method of preparing manganese tetraoxide by calcining manganese dioxide and manganese carbonate is not only costly, but also extremely unfriendly to the environment; the traditional production process using manganese sulfate as raw material requires the addition of catalysts and surfactants, and requires complex processes such as roasting and crushing. The prepared manganese tetraoxide is of low grade and cannot meet the standards of manganese tetraoxide for batteries.

[0004] There are two ways to prepare manganese tetraoxide using manganese salt as raw material: ① manganese ions can be directly oxidized to manganese tetraoxide by air at pH = 6.4-7.64; ② manganese ions are first converted into manganese hydroxide precipitation, and then oxidized by air to obtain manganese tetraoxide. Analysis of the pros and cons of the two approaches shows that when manganese ions are directly oxidized by air in MnSO4 solution, a large amount of sulfate ions exist in the system, and sulfate ions are easily mixed in the product, affecting the product quality. In addition, when the pH in the solution is controlled at 6.4-7.64, the reaction formula for oxidation by air is:

[0005] 6Mn 2+ +6H2O+O2=2Mn3O4+12H +

[0006] The reaction process generates a large amount of acid, which rapidly reduces the pH value of the solution. Since the oxidation reaction requires the pH value of the solution to be kept within a narrow range, alkali needs to be continuously added during the reaction process to neutralize the generated acid, which not only increases the difficulty of the operation, but also the alkali will bring in impurities and complicate the process.

[0007] Other methods for preparing manganese tetraoxide using manganese sulfate as raw material are all one-step methods, that is, adding manganese salt into the reaction tank at one time, then introducing air or oxygen for oxidation, and adding alkali to adjust the pH value. The manganese tetraoxide prepared by this method has poor performance and cannot meet the requirements for battery-grade manganese tetraoxide production. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for preparing high-purity manganese tetraoxide dedicated to high-end lithium manganate from manganese sulfate. The method uses manganese sulfate as a raw material, first prepares seed crystals, and then performs oxidation synthesis to slowly grow the seed crystals. The method does not require any additives and eliminates complex processes such as roasting and crushing. Manganese tetraoxide particles of different particle sizes can be prepared. The prepared manganese tetraoxide product has the advantages of high sphericity, controllable particle size distribution, high tap density, low specific surface area, high process automation, improved physical and chemical properties of manganese tetraoxide, reduced impurity content in the product, and the like.

[0009] The present invention adopts the following technical solutions:

[0010] A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate, comprising the following steps:

[0011] 1) Raw material preparation: high-purity manganese sulfate mother liquor from the refining workshop is used, the mother liquor is pumped into a mother liquor storage tank, pure water is added to dilute the solution to an optimum concentration range of 1.0-3.0 mol / L, and the solution is allowed to stand for buffering;

[0012] 2) Heat the base liquid, start stirring, add a certain amount of pure water as the base liquid into the reaction tank, and heat it to the optimal reaction temperature of 50-90°C;

[0013] 3) Seed crystal preparation: a certain amount of reaction mother solution and saline-alkali solution are continuously and slowly added to the microreactor to prepare seed crystals, and after sufficient reaction, the seed crystals flow into the reaction tank for aging;

[0014] 4) Seed oxidation: After the seed crystals are aged, air is introduced to fully oxidize them, and saline-alkali solution is added to control the pH value to always remain in the optimal pH range of 6.4-8.2;

[0015] 5) Seed crystal growth: After the seed crystal oxidation is completed, the reaction mother liquor is continuously added to the reaction tank, and the mother liquor flow rate is controlled to be 50-150 L / h. At the same time, air is introduced for oxidation, and the air flow rate is controlled. At the same time, a saline solution is added, and the saline solution flow rate is controlled to be 20 L / h. The stirring speed is controlled, and the pH value is always controlled to be kept in the optimal pH range. After the mother liquor is added, the oxidation is completed until the manganese ion concentration is lower than 3g / L, which is the end point;

[0016] 6) Dehydration while hot: transfer to a dehydrator for dehydration while hot to obtain a crude product;

[0017] 7) Washing and dehydration: The crude product is transferred to the washing tank, the washing temperature is 80-95℃, the material-water ratio is not less than 1:3, wash twice, each time for 2 hours, and after washing, transfer to the dehydrator for dehydration while hot;

[0018] 8) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying;

[0019] 9) Screening and packaging: The dried product is screened through a screen to obtain manganese tetraoxide product.

[0020] The product particle size, tap density and other indicators obtained by the process of the present invention are good, and a new method can be provided for the preparation of battery-grade manganese tetraoxide.

[0021] Other methods include: preparing seed crystals first, then continuously adding liquid for oxidation synthesis to make the seed crystals grow continuously, and continuously sending samples to detect the particle size of the reaction material during the test, and stopping the material when the opportunity arises, so as to obtain manganese tetraoxide products with different particle sizes.

[0022] The method comprises the following steps: firstly adding part of manganese salt to the reaction tank for oxidation to synthesize manganese tetraoxide seed crystals, and then continuously adding manganese salt for oxidation. Since manganese tetraoxide is insoluble in water, newly generated manganese tetraoxide particles will precipitate and wrap around the original manganese tetraoxide seed crystals.

[0023] Preferably, the mother liquor is high-purity manganese sulfate mother liquor from a refining workshop.

[0024] The use of high-purity manganese sulfate mother liquor from the refining workshop avoids impurities brought by the reaction, and the obtained manganese tetraoxide has higher purity. Reaction media such as ammonium sulfate and ammonia water can be fully utilized during the reaction process, saving production costs.

[0025] Preferably, the amount of mother liquor in step 3) is 0%-50% of the required reaction solution. Preferably, the saline-alkali solution in steps 3)-5) is prepared from one or more of ammonium sulfate, ammonia water, and sodium hydroxide.

[0026] Preferably, in step 5), the stirring speed is 100-450 r / min.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. The present invention uses high-purity manganese sulfate mother liquor as raw material to avoid impurities caused by the reaction, and the obtained manganese tetraoxide has higher purity. Reaction media such as ammonium sulfate and ammonia water can be repeatedly used during the reaction process, saving production costs.

[0029] 2. The preparation method of the present invention is simple, does not require a strict production environment, can be synthesized in a non-closed reactor, and has low requirements on equipment.

[0030] 3. Prepare seed crystals first, then continuously add liquid for oxidation synthesis to make the seed crystals grow continuously, and at the same time continuously detect the particle size of the material and stop the material when the opportunity arises, so that manganese tetraoxide with different particle sizes can also be obtained.

[0031] 4. The prepared manganese tetraoxide product has high sphericity, controllable particle size distribution, high tap density and low specific surface area, which improves the physical and chemical properties of manganese tetraoxide and reduces the impurity content in the product. The particles of the prepared manganese tetraoxide product are spherical, D10≥3um, D50=5-15umn, D90≤20um; the tap density of the manganese tetraoxide product is 2.20-2.80g / cm 3 , specific surface area ≤2.0m 2 / g, total manganese content 70.0-72.0%, moisture content ≤0.2%, sulfate content ≤0.5%, all indicators are excellent, fully in line with the standards of battery-grade manganese tetraoxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of the process of preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate.

[0033] Figure 2 This is a 1000x electron microscope image of trimanganese tetraoxide product 1#* obtained in Example 1.

[0034] Figure 3 This is a 1000x electron microscope image of the trimanganese tetraoxide product 2#* obtained in Example 2.

[0035] Figure 4 This is a 1000x electron microscope image of trimanganese tetraoxide product 3#* obtained in Example 3.

[0036] Figure 5 This is a 1000x electron microscope image of the manganese tetraoxide product 4#* obtained in the comparative example. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention 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 invention and are not used to limit the present invention.

[0038] The present invention will be further described below in conjunction with specific embodiments.

[0039] The method described in the present invention is that the mother liquor used is 1m 3 , the reaction tank is 5m 3 By controlling the reaction conditions, manganese tetraoxide with different particle sizes can be obtained.

[0040] Example 1

[0041] A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate, comprising the following steps:

[0042] 1) Raw material preparation: Put the high-purity manganese sulfate mother liquor from the refining workshop into the mother liquor buffer tank, add pure water to dilute it to 2.0 mol / L for standby use, take 1m 3 The mother liquor is added to the mother liquor tank; sodium hydroxide and ammonium sulfate are dissolved and then prepared with 18-20% ammonia water to prepare a saline solution and added to the saline tank;

[0043] 2) Heating the bottom liquid: Add 1.5 cubic meters of pure water as the bottom liquid to the reaction tank so that it just covers the stirring blades, and heat the bottom liquid to 55±5℃;

[0044] 3) Seed preparation: 200L of mother liquor and saline-alkali solution are slowly introduced into the microreactor to prepare seed crystals, which are then allowed to react fully and then flow into the reaction tank for full aging;

[0045] 4) Seed oxidation: After the seed aging is completed, air is introduced for full oxidation, the air flow rate is controlled at 16-18Nm3 / h, and saline-alkali solution is added to control the pH value to 7.7±0.5;

[0046] 5) Seed growth: After the seed oxidation is completed, the mother liquid is continuously introduced into the reaction tank, and the mother liquid flow rate is controlled at 50L / h, and the air flow rate is controlled at 16-18Nm 3 / h, control the stirring speed at 100r / min, control the reaction temperature at 55±5℃, add saline solution to control the pH value to 7.8±0.5, and continue to introduce air to oxidize to the end point after the mother liquor is added. The end point judgment standard is that the concentration of manganese sulfate in the solution is lower than 3g / L;

[0047] 6) Dehydration while hot: The material is transferred to the dehydrator through the transfer tank and dehydrated while hot to obtain the crude product;

[0048] 7) Product washing: The crude product is transferred to the washing tank, washed twice at a material-water ratio of 1:5 and a washing temperature of 95°C, each time for 2 hours. After washing, it is transferred to the dehydrator through the transfer tank for dehydration while hot;

[0049] 8) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying;

[0050] 9) Screening and packaging: The dried product is screened through a 100-mesh screen to obtain manganese tetraoxide product 1#.

[0051] The obtained manganese tetraoxide product 1# was tested, and the results are shown in Table 1. Figure 2 shown.

[0052] Example 2

[0053] A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate, comprising the following steps:

[0054] 1) Raw material preparation: Put the high-purity manganese sulfate mother liquor from the refining workshop into the mother liquor buffer tank, add pure water to dilute it to 1.0 mol / L for standby use, take 1m 3 The mother liquor is added to the mother liquor tank; sodium hydroxide and ammonium sulfate are dissolved and then prepared with 18-20% ammonia water to prepare a saline solution and added to the saline tank;

[0055] 2) Heating the bottom liquid: Add 1.5 cubic meters of pure water as the bottom liquid to the reaction tank so that it just covers the stirring blades, and heat the bottom liquid to 85±5℃;

[0056] 3) Seed preparation: 200L of mother liquor and saline-alkali solution are slowly introduced into the microreactor to prepare seed crystals, which are then allowed to react fully and then flow into the reaction tank for full aging;

[0057] 4) Seed oxidation: After the seed aging is completed, air is introduced to fully oxidize it, and the air flow rate is controlled at 16-18Nm 3 / h, add saline solution to control pH value = 6.9 ± 0.5;

[0058] 5) Seed growth: After the seed oxidation is completed, the mother liquid is continuously introduced into the reaction tank, and the mother liquid flow rate is controlled at 100L / h and the air flow rate is controlled at 16-18Nm 3 / h, control the stirring speed at 450r / min, control the reaction temperature at 60±5℃, add saline solution to control the pH value to 6.9±0.5, and continue to introduce air to oxidize to the end point after the mother liquor is added. The end point judgment standard is that the concentration of manganese sulfate in the solution is lower than 3g / L;

[0059] 6) Dehydration while hot: The material is transferred to the dehydrator through the transfer tank and dehydrated while hot to obtain the crude product;

[0060] 7) Product washing: The crude product is transferred to the washing tank, washed twice at a material-water ratio of 1:4 and a washing temperature of 85°C, each time for 2 hours. After washing, it is transferred to the dehydrator through the transfer tank for hot dehydration;

[0061] 8) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying;

[0062] 9) Screening and packaging: The dried product is screened through a 100-mesh screen to obtain manganese tetraoxide product 2#.

[0063] The obtained manganese tetraoxide product 2# was tested, and the results are shown in Table 1. Figure 3 shown.

[0064] Example 3

[0065] A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate, comprising the following steps:

[0066] 1) Raw material preparation: Put the high-purity manganese sulfate mother liquor from the refining workshop into the mother liquor buffer tank, add pure water to dilute it to 3.0 mol / L for standby use, take 1m 3 The mother liquor is added to the mother liquor tank; sodium hydroxide and ammonium sulfate are dissolved and then prepared with 18-20% ammonia water to prepare a saline solution and added to the saline tank;

[0067] 2) Heating the bottom liquid: Add 1.5 cubic meters of pure water as the bottom liquid to the reaction tank so that it just covers the stirring blades, and heat the bottom liquid to 70±5℃;

[0068] 3) Seed preparation: 200L of mother liquor and saline-alkali solution are slowly introduced into the microreactor to prepare seed crystals, which are then allowed to react fully and then flow into the reaction tank for full aging;

[0069] 4) Seed oxidation: After the seed aging is completed, air is introduced to fully oxidize it, and the air flow rate is controlled at 16-18Nm 3 / h, add saline solution to control pH value = 7.8 ± 0.5;

[0070] 5) Seed growth: After the seed oxidation is completed, the mother liquid is continuously introduced into the reaction tank, and the mother liquid flow rate is controlled at 150L / h and the air flow rate is controlled at 16-18Nm 3 / h, control the stirring speed at 300r / min, control the reaction temperature at 65±5℃, add saline solution to control the pH value to 7.0±0.5, and continue to introduce air to oxidize to the end point after the mother liquor is added. The end point judgment standard is that the concentration of manganese sulfate in the solution is lower than 3g / L;

[0071] 6) Dehydration while hot: The material is transferred to the dehydrator through the transfer tank and dehydrated while hot to obtain the crude product;

[0072] 7) Product washing: The crude product is transferred to the washing tank, washed twice at a material-water ratio of 1:5 and a washing temperature of 80°C, each time for 2 hours. After washing, it is transferred to the dehydrator through the transfer tank for dehydration while hot;

[0073] 8) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying;

[0074] 9) Screening and packaging: The dried product is screened through a 100-mesh screen to obtain manganese tetraoxide product 3#.

[0075] The obtained manganese tetraoxide product 3# was tested, and the results are shown in Table 1. Figure 4 shown.

[0076] Comparative Example

[0077] A method for preparing high-purity manganese tetraoxide special for high-end lithium manganate from manganese sulfate.

[0078] 1) Raw material preparation: Put the high-purity manganese sulfate mother liquor from the refining workshop into the mother liquor buffer tank, add pure water to dilute it to 3.0 mol / L for standby use, take 1m 3 The mother liquor is added to the mother liquor tank; sodium hydroxide and ammonium sulfate are dissolved and then prepared with 18-20% ammonia water to prepare a saline solution and added to the saline tank;

[0079] 2) Heating the bottom liquid: Add 1.5 cubic meters of pure water as the bottom liquid to the reaction tank so that it just covers the stirring blades, and heat the bottom liquid to 60±5℃;

[0080] 3) Oxidative synthesis: No seed crystals were prepared, that is, the mother liquor was directly introduced into the reaction tank, the mother liquor flow rate was controlled at 50 L / h, and the air flow rate was controlled at 16-18 Nm 3 / h, control the stirring speed at 300r / min, control the reaction temperature at 70±5℃, add saline solution to control the pH value to 7.8±0.5, and continue to introduce air to oxidize to the end point after the mother liquor is added. The end point judgment standard is that the concentration of manganese sulfate in the solution is lower than 3g / L;

[0081] 4) Dehydration while hot: The material is transferred to the dehydrator through the transfer tank and dehydrated while hot to obtain the crude product;

[0082] 5) Product washing: The crude product is transferred to the washing tank, washed twice at a material-water ratio of 1:5 and a washing temperature of 80°C, each time for 2 hours. After washing, it is transferred to the dehydrator through the transfer tank for dehydration while hot;

[0083] 6) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying;

[0084] 7) Screening and packaging: The dried product is screened through a 100-mesh screen to obtain manganese tetraoxide product 4#.

[0085] The obtained manganese tetraoxide product 4# was tested, and the results are shown in Table 1. Figure 5 shown.

[0086] The product data of manganese tetraoxide obtained by the process described in the above embodiment and comparative example are shown in the following table (1):

[0087] Table (1) Product data of manganese tetraoxide obtained by the process described in Examples 1-3 and Comparative Examples

[0088]

[0089] It can be seen from Table (1) that the manganese tetraoxide product prepared by the process of the present invention has high sphericity, controllable particle size distribution, high tap density, and low specific surface area, and has the advantages of improving the physical and chemical properties of manganese tetraoxide and reducing the impurity content in the product. The particles of the manganese tetraoxide product prepared are spherical, D10≥3um, D50=5-15um, D90≤20um; the tap density of the manganese tetraoxide product is 2.20-2.80g / cm 3 , specific surface area ≤2.0㎡ / g, total manganese content 70.0-72.0%, moisture mass ≤0.2%, sulfate content ≤0.5%, all indicators are excellent, fully in line with the standards of battery-grade manganese tetraoxide.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate, characterized in that: The following steps are involved: 1) Raw material preparation: use high-purity manganese sulfate mother liquor from the refining workshop, transfer the mother liquor to the mother liquor storage tank, add pure water to dilute to the optimum solution concentration range of 1.0-3.0 mol / L, and place it in a static buffer; 2) Heat the base liquid, start stirring, add a certain amount of pure water as the base liquid into the reaction tank, and heat it to the optimal reaction temperature of 50-90°C; 3) Seed crystal preparation: a certain amount of reaction mother solution and saline-alkali solution are continuously and slowly added to the microreactor to prepare seed crystals, and after sufficient reaction, the seed crystals flow into the reaction tank for aging; 4) Seed oxidation: After the seed crystals are aged, air is introduced to fully oxidize them, and saline-alkali solution is added to control the pH value to always remain in the optimal pH range of 6.4-8.2; 5) Seed crystal growth: After the seed crystal oxidation is completed, the reaction mother liquor is continuously added to the reaction tank, and the mother liquor flow rate is controlled to be 50-150 L / h. At the same time, air is introduced for oxidation, and the air flow rate is controlled. At the same time, a saline solution is added, and the saline solution addition flow rate is controlled to be 20 L / h. The stirring speed is controlled, and the pH value is always controlled to be kept in the optimal pH range. After the mother liquor is added, the oxidation is completed until the manganese ion concentration is lower than 3g / L, which is the end point; 6) Dehydration while hot: transfer to a dehydrator for dehydration while hot to obtain a crude product; 7) Washing and dehydration: The crude product is transferred to the washing tank, the washing temperature is 80-95℃, the material-water ratio is not less than 1:3, wash twice, each time for 2 hours, and after washing, transfer to the dehydrator for dehydration while hot; 8) Airflow drying: After dehydration, transfer to the finished product workshop for airflow drying; 9) Screening and packaging: The dried product is screened through a screen to obtain manganese tetraoxide product.

2. A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate as claimed in claim 1, characterized in that: The mother liquor is high-purity manganese sulfate mother liquor from the refining workshop.

3. A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate as claimed in claim 1, characterized in that: In step 3), the amount of the mother liquor is 0%-50% of the required reaction solution.

4. A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate as claimed in claim 1, characterized in that: The saline-alkali solution in steps 3)-5) is prepared from one or more of ammonium sulfate, ammonia water and sodium hydroxide.

5. A method for preparing high-purity manganese tetraoxide for high-end lithium manganate from manganese sulfate as claimed in claim 1, characterized in that: In step 5), the stirring speed is 100-450 r / min.

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