Preparation method of iron oxide material for battery
Through the normal pressure hydrothermal synthesis method, iron oxide materials for batteries are prepared by titanium dioxide industry by-product green alum, which solves the problem of difficult impurities and wastewater in the existing technology, realizes the controllability of product hue and apparent viscosity, and significantly improves the performance and stability of battery materials.
Patent Information
- Application Number
- CN202510515678.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-06-24
AI Technical Summary
In the prior art, the preparation method of iron oxide materials for batteries has problems of difficult impurities, wastewater problems, and product hue and apparent viscosity discomfort, which is difficult to meet the strict quality requirements of lithium battery materials.
Using the normal pressure hydrothermal synthesis method, using the by-product of titanium dioxide industry as raw material, magnesium ions are removed by selective addition of fluorine-containing ion solution, combined with the mixing and oxidation reaction of dispersant and ferrous nitrate solution, the pH value and reaction conditions are adjusted, and iron oxide materials for batteries with D50 of 40-60 nm and apparent viscosity of 75-95 Pa·s are prepared.
It effectively removes impurities and ions in iron oxide materials, controls the hue and apparent viscosity of the product, significantly improves the performance and stability of the battery material, reduces environmental pollution, and conforms to the concept of green chemistry.
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Figure BDA0005372497470000061
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium battery materials. More specifically, it relates to a process for preparing iron oxide materials for batteries by an atmospheric pressure hydrothermal synthesis method using by - product green vitriol from the titanium dioxide industry as raw material. Background Art
[0002] Iron oxide materials for batteries are key precursors for preparing lithium iron phosphate (LFP) cathode materials and lithium - ion battery anode materials. Their quality requirements are strict: 1) Low impurity ion content: For cathode materials, the content of elements such as chromium, manganese, sodium, and potassium should be less than 50 ppm; for anode materials, the content of elements such as chromium, magnesium, and manganese should be less than 100 ppm.
[0003] 2) Uniform particle size distribution: D50 needs to be controlled within 40 - 60 nm, which directly affects the electrochemical performance of battery materials. 3) Appropriate apparent viscosity: The optimal apparent viscosity is 80 ± 15 Pa·s to ensure uniform dispersion of the material in the slurry.
[0004] In the prior art, the mixed - acid method (reacting metal iron scraps with nitric acid and sulfuric acid) has problems such as high cost, difficult impurity control, and ammonia - nitrogen - containing sewage, and the obtained products are mainly used in the pigment field. The traditional hydrothermal method uses by - product green vitriol (ferrous sulfate heptahydrate) from titanium dioxide as raw material. Although it can reduce the impurity content, it has defects such as long reaction time, yellowish product hue (reddish - yellow or yellowish - red hue), and high apparent viscosity.
[0005] Therefore, it is necessary to develop an improved atmospheric pressure hydrothermal synthesis process to prepare iron oxide materials for batteries with low impurity content, controllable hue (orange - red or pure red), and appropriate apparent viscosity. Summary of the Invention
[0006] Aiming at the above - mentioned problems existing in the prior art, the technical problem to be solved by the present invention is to provide a preparation method of iron oxide materials for batteries, which can comprehensively utilize green vitriol resources and reduce environmental pollution.
[0007] To solve the above - mentioned technical problems, the technical solution adopted by the present invention is as follows:
[0008] A preparation method of iron oxide materials for batteries, comprising the following steps:
[0009] (1) Dissolve by - product green vitriol from the titanium dioxide industry in water, add reduced iron powder, stir at 85 - 95 °C, and filter to obtain a ferrous sulfate solution;
[0010] (2) Selectively add a fluoride - ion - containing solution to the ferrous sulfate solution obtained in step (1) to remove magnesium ions, and filter to obtain a solution;
[0011] (3) Mix the solution obtained in step (2) with a dispersant and a ferrous nitrate solution evenly at room temperature, introduce air for an oxidation reaction, add liquid alkali to adjust the pH, and stop the reaction when the solution pH reaches 8 - 9.5 to obtain a solution containing crystal seeds;
[0012] (4) Add a ferrous nitrate solution, the ferrous sulfate solution prepared in step (1), and a viscosity regulator to the solution containing crystal seeds obtained in step (3), adjust the pH to 5 - 6 for reaction, and obtain an iron oxide material for batteries with a D50 of 40 - 60 nm and an apparent viscosity of 75 - 95 Pa·s through post-treatment.
[0013] Preferably, in step (1), the addition amount of reduced iron powder is 1% - 1.5% of the mass of ferrous sulfate heptahydrate.
[0014] Preferably, in step (1), a solution with a ferrous sulfate concentration of 10 - 100 g / L is obtained.
[0015] Preferably, in step (2), the fluoride ion-containing solution is sodium fluoride or ammonium fluoride, and the addition amount is 1% - 5% of the mass of ferrous sulfate heptahydrate.
[0016] Preferably, in step (3), the dispersant is propylene glycol, and the addition amount is 0.001% - 0.1% of the total mass of the solution.
[0017] Preferably, in step (3), the concentration of ferrous nitrate is 20 - 30 g / L, and the addition amount is 1% - 50% of the total mass of the solution.
[0018] Preferably, in step (3), the flow rate of the introduced air is 3 - 4 m 3 ·h -1 。
[0019] Preferably, in step (4), the addition amount of the ferrous nitrate solution is 25% - 45% of the total mass of the solution, and the addition amount of the ferrous sulfate solution is 5% - 25% of the total mass of the solution.
[0020] Preferably, in step (4), the viscosity regulator is a mixture of polyethylene glycol and diethylene glycol, and the proportion of polyethylene glycol is 25% - 75%.
[0021] Preferably, in step (4), the reaction temperature is 85 °C, the air flow rate is 2 - 3 m 3 ·h-1, and the reaction time is 2 h.
[0022] Compared with the prior art, the beneficial effects of the present invention are:
[0023] 1) The process for preparing iron oxide red by hydrothermal synthesis provided by the present invention uses by - product green vitriol from the titanium dioxide industry as the main raw material, replacing the iron sheet method for preparing iron oxide red. While realizing the high - value utilization of green vitriol, this liquid - phase method can effectively remove the content of impurity ions in iron oxide red, is more suitable for use in lithium - ion battery cathode materials, significantly improves the battery performance and stability, reduces environmental pollution, conforms to the concept of green chemistry, and has broad application prospects and economic benefits.
[0024] 2) In the present invention, during the preparation of crystal seeds and the second - step oxidation process, by adding an appropriate amount of ferrous nitrate solution to adjust the hue of the iron oxide red product, on the premise of having a good hue, the product has a low content of impurity ions. At the same time, by further adding a viscosity regulator, the product has a low apparent viscosity after drying, meeting the requirements of iron oxide materials for batteries. Detailed implementation manners
[0025] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the technical means used are all conventional means well - known to those skilled in the art.
[0026] Example 1
[0027] A preparation method of an iron oxide material for batteries includes the following steps:
[0028] 1) Take 5 kg of by - product green vitriol from titanium dioxide, dissolve it in water, add 0.05 kg of reduced iron powder, stir at 90 °C for 2 h, and obtain a ferrous sulfate solution with a concentration of 10 g / L through filtration.
[0029] 2) Mix 30 kg of ferrous sulfate solution with a concentration of 10 g / L, 0.5 g of propylene glycol, and 20 kg of ferrous nitrate solution with a concentration of 25 g / L evenly at room temperature, blow in air with a flow rate of 3 m 3 ·h -1 of air, quickly adjust the pH to 9.5 - 10.5 by adding liquid caustic soda, and continue to blow in air for oxidation. During this period, add liquid caustic soda appropriately 2 - 3 times to generate a crystal seed solution with a pH of 8.2.
[0030] 3) Mix 30 kg of the crystal seed solution with 20 kg of ferrous nitrate solution with a concentration of 25 g / L and 10 kg of ferrous sulfate solution with a concentration of 10 g / L, adjust the pH to 5.2 at 85 °C, after reacting for 1.5 h, add 50 g of a viscosity regulator (polyethylene glycol:diethylene glycol = 1:1), and continue to react for 0.5 h.
[0031] 4) After filtering, washing, drying, and sieving the product obtained in step 3), iron oxide red is prepared, with D50 being 52 ± 5 nm and the apparent viscosity being 90 ± 5 Pa·s.
[0032] Example 2
[0033] A preparation method of iron oxide material for batteries, comprising the following steps:
[0034] 1) Take 5 kg of by - product ferrous sulfate heptahydrate from titanium white production and dissolve it in water. Add 0.055 kg of reduced iron powder, stir at 90 °C for 2 h, and filter to obtain a ferrous sulfate solution with a concentration of 100 g / L;
[0035] 2) Add 0.05 kg of ammonium fluoride to the ferrous sulfate solution obtained in step 1) to remove magnesium;
[0036] 3) Stir 20 kg of the impurity - removed ferrous sulfate solution, 2.5 g of propylene glycol, and 15 kg of ferrous nitrate solution with a concentration of 25 g / L evenly at room temperature. Bubble air with a flow rate of 3 m 3 ·h -1 of air, add liquid alkali quickly to adjust the pH to 9.5 - 10.5, and continue to bubble air for oxidation. During this period, add liquid alkali appropriately 2 - 3 times to generate a seed solution with a pH of 8.8;
[0037] 4) Mix 30 kg of the seed solution, 20 kg of ferrous nitrate solution with a concentration of 25 g / L, and 10 kg of ferrous sulfate solution with a concentration of 100 g / L, adjust the pH to 5.2 at 85 °C, react for 1.5 h, then add 60 g of viscosity regulator (polyethylene glycol:diethylene glycol = 3:1), and continue to react for 0.5 h;
[0038] 5) After filtering, washing, drying, and sieving the product obtained in step 4), iron oxide red is prepared, with D50 being 63 ± 5 nm and the apparent viscosity being 80 ± 5 Pa·s.
[0039] Example 3
[0040] A preparation method of iron oxide material for batteries, comprising the following steps:
[0041] 1) Take 5 kg of by - product ferrous sulfate heptahydrate from titanium white production and dissolve it in water. Add 0.065 kg of reduced iron powder, stir at 90 °C for 2 h, and filter to obtain a ferrous sulfate solution with a concentration of 50 g / L;
[0042] 2) Add 0.25 kg of sodium fluoride to the ferrous sulfate solution obtained in step 1) to remove magnesium;
[0043] 3) Stir 30 kg of the impurity - removed ferrous sulfate solution, 1.5 g of propylene glycol, and 10 kg of ferrous nitrate solution with a concentration of 25 g / L evenly at room temperature. Bubble air with a flow rate of 3 m 3 ·h -1Air was introduced, and liquid caustic soda was added to quickly adjust the pH to 9.5 - 10.5. Then, air was continuously introduced for oxidation, and liquid caustic soda was appropriately replenished 2 - 3 times during this period to produce a seed solution with a pH of 8.5.
[0044] 4) Mix 30 kg of the seed solution with 15 kg of a ferrous nitrate solution with a concentration of 25 g / L and 15 kg of a ferrous sulfate solution with a concentration of 50 g / L. Adjust the pH to 5.2 at 85°C, and after reacting for 1.5 h, add 40 g of a viscosity regulator (polyethylene glycol:diethylene glycol = 1:3), and continue to react for 0.5 h.
[0045] 5) After filtering, washing, drying, and sieving the product obtained in step 4), iron oxide red was prepared, with D50 being 58 ± 5 nm and the apparent viscosity being 84 ± 5 Pa·s.
[0046] Example 4
[0047] When preparing the iron oxide material for batteries, step 1) was as follows: Take 5 kg of titanium white by - product green vitriol, dissolve it in water, add 0.075 kg (1.5%) of reduced iron powder, stir at 90°C for 2 h, and obtain a ferrous sulfate solution with a concentration of 50 g / L through filtration. The remaining preparation methods and parameters were the same as those in Example 1, and the iron oxide material for batteries was prepared, with D50 being 53 ± 5 nm and the apparent viscosity being 85 ± 5 Pa·s.
[0048] Example 5
[0049] When preparing the iron oxide material for batteries, in step 3), polyethylene glycol:diethylene glycol = 1:3. The remaining preparation methods and parameters were the same as those in Example 1, and the iron oxide material for batteries was prepared, with D50 being 76 ± 5 nm, and the apparent viscosity being 105 ± 10 Pa·s.
[0050] Example 6
[0051] When preparing the iron oxide material for batteries, in step 3), polyethylene glycol:diethylene glycol = 3:1. The remaining preparation methods and parameters were the same as those in Example 1, and the iron oxide material for batteries was prepared, with D50 being 48 ± 5 nm and the apparent viscosity being 70 ± 5 Pa·s.
[0052] Comparative Example 1
[0053] When preparing the iron oxide material for batteries, in step 3), after reacting for 1 h, add 50 g of a viscosity regulator and continue to react for 0.5 h. The remaining preparation methods and parameters were the same as those in Example 1, and the iron oxide material for batteries was prepared, with D50 being 50 ± 5 nm and the apparent viscosity being 80 ± 5 Pa·s.
[0054] Comparative Example 2
[0055] When preparing the iron oxide material for the battery, step 1) is as follows: Take 5 kg of titanium white by-product green vitriol, dissolve it in water, add 0.15 kg (3.0%) of reduced iron powder, stir at 90 °C for 2 h, and obtain a ferrous sulfate solution with a concentration of 50 g / L through filtration. The remaining preparation methods and parameters are the same as those in Example 1, and the iron oxide material for the battery is prepared. The D50 is 48 ± 5 nm, and the apparent viscosity is 78 ± 5 Pa·s.
[0056] Comparative Example 3
[0057] When preparing the iron oxide material for the battery, step 1) is as follows: Take 5 kg of titanium white by-product green vitriol, dissolve it in water, add 0.03 kg (0.6%) of reduced iron powder, stir at 90 °C for 2 h, and obtain a ferrous sulfate solution with a concentration of 50 g / L through filtration. The remaining preparation methods and parameters are the same as those in Example 1, and the iron oxide material for the battery is prepared. The D50 is 65 ± 5 nm, and the apparent viscosity is 95 ± 10 Pa·s.
[0058] The main impurity elements of the iron oxide materials for the battery prepared in Examples 1-6 and Comparative Examples 1-3 were analyzed, and the results are shown in Table 1.
[0059] Table 1 Results of impurity element contents in the iron oxide material for the battery
[0060]
[0061]
[0062] As can be seen from Table 1, the process for preparing iron oxide red by hydrothermal synthesis provided by the present invention uses titanium white industrial by-product green vitriol as the main raw material to replace the iron sheet method for preparing iron oxide red. While realizing the high-value utilization of green vitriol, this liquid-phase method can effectively remove the content of impurity ions in iron oxide red and is more suitable for use in lithium-ion battery cathode materials, significantly improving the purity and performance of the iron oxide material for the battery, and providing a better material choice for the lithium-ion battery industry.
[0063] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.
Claims
1. A method for preparing an iron oxide material for a battery, characterized in that: The following steps are involved: (1) dissolving green vitriol, a by-product of titanium dioxide industry, in water, adding reduced iron powder, stirring at 85-95° C., and filtering to obtain a ferrous sulfate solution; (2) selectively adding a fluoride ion solution to the ferrous sulfate solution obtained in step (1) to remove magnesium ions, and filtering to obtain a solution; (3) mixing the solution obtained in step (2) with a dispersant and a ferrous nitrate solution at room temperature, blowing air into the mixture for oxidation reaction, adding liquid alkali to adjust the pH, and stopping the reaction when the pH of the solution reaches 8 to 9.5 to obtain a seed crystal-containing solution; (4) Adding ferrous nitrate solution, ferrous sulfate solution obtained in step (1) and viscosity regulator to the seed solution obtained in step (3), adjusting the pH to 5-6 for reaction, and obtaining an iron oxide material for battery with a D50 of 40-60 nm and an apparent viscosity of 75-95 Pa·s through post-treatment.
2. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (1), the amount of reduced iron powder added is 1% to 1.5% of the mass of the green vitriol.
3. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (1), a solution with a ferrous sulfate concentration of 10 to 100 g / L is obtained.
4. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (2), the fluoride ion solution is sodium fluoride or ammonium fluoride, and the added amount is 1% to 5% of the mass of the green vitriol.
5. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (3), the dispersant is propylene glycol, and the added amount is 0.001% to 0.1% of the total mass of the solution.
6. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (3), the concentration of ferrous nitrate is 20-30 g / L, and the amount added is 1%-50% of the total mass of the solution.
7. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In step (3), the flow rate of the blown air is 3 to 4 m 3 ·h -1 .
8. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (4), the amount of ferrous nitrate solution added is 25% to 45% of the total solution mass, and the amount of ferrous sulfate solution added is 5% to 25% of the total solution mass.
9. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In the step (4), the viscosity regulator is a mixture of polyethylene glycol and diethylene glycol, with the polyethylene glycol accounting for 25% to 75%.
10. The method for preparing the iron oxide material for battery according to claim 1, characterized in that: In step (4), the reaction temperature is 85°C and the air flow rate is 2-3 m 3 ·h-1, the reaction time is 2h.