Method for synthesizing manganese iron phosphate by using phosphating slag and application of the manganese iron phosphate in positive electrode material

Abstract

The application relates to the field of new energy material preparation technology, and particularly discloses a method for synthesizing manganese iron phosphate from phosphating slag and application of the manganese iron phosphate in a positive electrode material. The method for synthesizing manganese iron phosphate from phosphating slag comprises the following steps: S1. Taking phosphating slag to detect the manganese and iron contents, dissolving the phosphating slag in concentrated phosphoric acid to obtain clear filtrate A; S2. According to the manganese and iron contents measured in S1, a divalent manganese salt and a ferrous salt are weighed and added into the filtrate A to obtain filtrate B; S3. A soluble zinc salt and a complexing agent are added into dilute phosphoric acid to configure a bottom solution; S4. The filtrate B is slowly added into the bottom solution to obtain manganese iron phosphate precipitate; and S5. Manganese iron phosphate powder is obtained. The manganese iron phosphate powder synthesized from the phosphating slag is used as raw material, mixed with lithium carbonate and glucose, pure water is added, sand grinding is carried out, spray drying is carried out, and sintering is carried out under the protection of a nitrogen atmosphere to obtain a manganese iron lithium phosphate positive electrode material, and the problems of low resource utilization efficiency of the phosphating slag and poor synthesis effect of the manganese iron phosphate are solved.

Description

Technical Field

[0001] This application relates to the field of new energy material preparation technology, and more specifically, it relates to a method for synthesizing manganese iron phosphate using phosphating slag and its application in cathode materials. Background Technology

[0002] Phosphating is a common surface treatment method for various metal materials. It can enhance the bonding force between the metal surface and the workpiece, improve the corrosion resistance, lubricity, and wear resistance of the metal material, and also serve a decorative purpose. The principle of phosphating is that phosphate ions in the phosphating solution precipitate with metal ions on the metal surface, forming a uniform and dense film. Commonly used phosphating solutions include zinc-based, iron-based, and manganese-based solutions. During the phosphating process, the generation of phosphating slag is unavoidable, especially when the phosphating solution ratio is improper, the workload is high, the temperature exceeds the limit, or the acidity is too high. If the phosphating slag is not cleaned in time, it will seriously affect the quality of the phosphating film formation, leading to problems such as ash buildup, looseness, and coarse crystals. The main components of phosphating slag are iron phosphate, zinc phosphate, and manganese phosphate. Simply treating it as hazardous waste not only poses safety hazards but also wastes a large amount of resources.

[0003] Lithium manganese iron phosphate batteries are an extension of lithium iron phosphate batteries. They possess the same good stability as lithium iron phosphate batteries while improving the discharge specific capacity of lithium iron phosphate batteries, making them another important way to achieve high energy density batteries.

[0004] In related technologies, phosphate slag contains a large amount of elements such as phosphate, iron, zinc or manganese. If phosphate slag is used as a raw material and then applied to the preparation of lithium manganese iron phosphate cathode materials, lithium iron phosphate materials or corresponding manganese iron phosphate and iron phosphate, it can not only solve the hazardous waste safety problem of phosphate slag, but also achieve low-cost preparation of lithium battery cathode materials. Therefore, this approach has important practical significance.

[0005] However, phosphating slag has problems in the synthesis of lithium manganese iron phosphate or lithium iron phosphate, such as poor reactivity, uneven synthesis products, large particle size and low purity. These problems hinder the efficient application of phosphating slag in lithium battery cathode materials. Summary of the Invention

[0006] To address the issues of low resource utilization efficiency of phosphating slag and poor synthesis effect of ferromanganese phosphate, this application provides a method for synthesizing ferromanganese phosphate using phosphating slag and its application in cathode materials.

[0007] This application provides a method for synthesizing ferromanganese phosphate using phosphating slag and its application in cathode materials, employing the following technical solution:

[0008] In a first aspect, this application provides a method for synthesizing ferromanganese phosphate using phosphating slag, employing the following technical solution:

[0009] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0010] S1. Take the phosphate residue and test its manganese and iron content. Dissolve the phosphate residue in concentrated phosphoric acid and stir at 40-70℃ for 2-5 hours. Filter while hot to obtain clear filtrate A. The phosphate residue includes iron-based, manganese-based, and zinc-based phosphate residues.

[0011] S2. Based on the manganese and iron content measured in S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 20%-50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 40-70℃ for 1-4 hours and filter while hot to obtain filtrate B.

[0012] S3. Add soluble zinc salt and complexing agent to dilute phosphoric acid with a concentration of 5-8% to prepare a mixed solution of zinc salt with a mass concentration of 0.5-3% and complexing agent with a mass concentration of 1-6% as the base solution;

[0013] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(1 / 3-3 / 4). Stir while adding, with a stirring speed of 120-330 rpm. After the addition is complete, heat to 60-75℃ and introduce oxygen. After reacting for 2-6 hours, filter while hot to obtain manganese iron phosphate precipitate.

[0014] S5. Dry the precipitate of manganese phosphate at 60-80℃ for 1-3 hours, grind it, and sieve it to obtain manganese phosphate powder.

[0015] By adopting the above technical solution and following the above steps, the problems of low resource utilization efficiency of phosphate slag and poor synthesis effect of manganese iron phosphate are improved. Compared with the prior art, this application can select iron-based, manganese-based, and zinc-based phosphate slag as raw materials. The component utilization rate of phosphate slag is higher, and manganese iron phosphate raw materials with high specific surface area can be obtained. The lithium manganese iron phosphate particles synthesized from this raw material are finer and have a higher specific surface area, exhibiting higher specific capacity and good cycle stability in battery performance tests. Experiments have shown that when a certain concentration of zinc ions is present in the solution, the addition of a macromolecular complexing agent allows the zinc ions to assist the complexing agent in forming a uniform and stable network framework in the solution, making the manganese and iron ions more uniformly dispersed and easier to generate small-diameter manganese iron phosphate particles. After the macromolecular complexing agent is dispersed in the solution, it can form a macromolecular network framework, constructing a micro-reaction synthesis chamber for manganese iron phosphate, significantly reducing the size of the synthesized manganese iron phosphate particles, obtaining manganese iron phosphate particles with a large specific surface area, and improving its application effect in lithium manganese iron phosphate cathode materials. Divalent manganese ions and zinc ions have similar ionic radii and outer electron structures. Divalent manganese ions can easily replace zinc ions mixed in ferric phosphate, so there is no need to worry about the addition of soluble zinc salts reducing the purity of the prepared ferric manganese phosphate phase. Therefore, the addition of zinc salts will not affect the high-purity preparation of ferric manganese phosphate.

[0016] Optionally, when testing the manganese and iron content of the phosphate slag, the manganese content is measured by perchloric acid oxidation, and the iron content is measured by potassium dichromate titration.

[0017] By adopting the above technical solutions, the perchloric acid oxidation method for measuring manganese content in phosphate slag is relatively simple to operate, and the measurement results are accurate and reliable. The potassium dichromate titration method for measuring iron content in phosphate slag is highly sensitive, capable of detecting iron content at low concentrations. Furthermore, the measurement results are accurate and reliable, and the operation is simple, improving detection efficiency.

[0018] Optionally, the divalent manganese salt is one or a combination of manganese dichloride, manganese nitrate, and manganese oxalate, and the ferrous salt is one or a combination of ferrous chloride, ferrous nitrate, and ferrous oxalate.

[0019] Experiments have shown that when the divalent manganese salt is one or a combination of manganese dichloride, manganese nitrate, and manganese oxalate, and the ferrous salt is one or a combination of ferrous chloride, ferrous nitrate, and ferrous oxalate, the S3 step reacts faster.

[0020] Optionally, the complexing agent is one or a combination of ethylenediaminetetraacetic acid, citric acid, succinic acid, and glycolic acid.

[0021] By adopting the above technical solution, ethylenediaminetetraacetic acid, citric acid, succinic acid, and glycolic acid have strong complexing ability and can form a uniform and stable network framework with zinc ions, making manganese ions and iron ions more uniformly dispersed and easier to generate small-sized manganese iron phosphate particles; subsequently, divalent manganese ions can easily replace zinc ions mixed in iron phosphate from the network framework.

[0022] Optionally, the soluble zinc salt is one or a combination of zinc chloride, zinc nitrate, and zinc acetate.

[0023] By adopting the above technical solution, zinc chloride, zinc nitrate, and zinc acetate can easily ionize into zinc ions, which in turn help the complexing agent form a uniform and stable network framework in the solution, making manganese ions and iron ions more evenly dispersed and easier to generate small-sized manganese iron phosphate particles.

[0024] Secondly, this application provides the application of manganese iron phosphate synthesized using phosphating slag in cathode materials, employing the following technical solution:

[0025] An application of the above-mentioned manganese iron phosphate synthesized from phosphating slag in cathode materials includes the following steps:

[0026] Using ferromanganese phosphate powder synthesized from phosphate slag as raw material, the ferromanganese phosphate powder is mixed with lithium carbonate and glucose, then pure water is added, the mixture is sand-milled and mixed evenly, spray-dried, and sintered under nitrogen atmosphere protection to obtain lithium manganese iron phosphate cathode material.

[0027] By adopting the above technical solution, using manganese iron phosphate powder synthesized from phosphate slag as raw material, the manganese iron phosphate powder is mixed with lithium carbonate and glucose, then pure water is added, the mixture is sand-milled and mixed evenly, spray-dried, and sintered under nitrogen atmosphere protection to obtain lithium manganese iron phosphate cathode material, which shows higher specific capacity and good cycle stability in battery performance tests.

[0028] Optionally, the molar ratio of the manganese iron phosphate powder, lithium carbonate, and glucose is 1:(0.40-0.60):(0.01-0.20).

[0029] By adopting the above technical solution, the cathode material with better performance is prepared by using a molar ratio of manganese iron phosphate powder, lithium carbonate, and glucose of 1:(0.40-0.60):(0.01-0.20).

[0030] Optionally, the ratio of the mixture of manganese iron phosphate powder, lithium carbonate, glucose, and pure water is 1:(3-5).

[0031] By adopting the above technical solution, the ratio of the mixture of manganese iron phosphate powder, lithium carbonate, glucose and pure water is 1:(3-5), which is more conducive to sand milling and mixing.

[0032] Optionally, during the sand milling process, manganese iron phosphate is first added and milled for 45-55 minutes, followed by lithium carbonate and milled for 20-40 minutes, and finally glucose is added and milled for 5-15 minutes, resulting in a D50 particle size of less than 0.5 μm.

[0033] By adopting the above technical solution, the particle sizes of ferromanganese phosphate, lithium carbonate, and glucose decrease sequentially. Adding ferromanganese phosphate, lithium carbonate, and glucose in that order helps to achieve more uniform particle sizes and more homogeneous mixing. When the D50 particle size is below 0.5 μm, the resulting cathode material exhibits better performance.

[0034] Optionally, the sintering temperature is 620-640℃.

[0035] By adopting the above technical solution, the sintering temperature is 620-640℃, resulting in a cathode material with better performance.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. Since this application selects iron-based, manganese-based, and zinc-based phosphate slag as raw materials, the component utilization rate of phosphate slag is higher, and high specific surface area manganese iron phosphate raw materials can be obtained. The lithium manganese iron phosphate particles synthesized from this raw material are finer and have a higher specific surface area, exhibiting higher specific capacity and good cycle stability in battery performance tests.

[0038] 2. In this application, one or more of ethylenediaminetetraacetic acid, citric acid, succinic acid, and ethylene glycol are preferably used as complexing agents. Because ethylenediaminetetraacetic acid, citric acid, succinic acid, and ethylene glycol have strong complexing ability, they can form a uniform and stable network framework with zinc ions, making manganese ions and iron ions more uniformly dispersed and easier to generate small-diameter iron manganese phosphate particles; subsequently, divalent manganese ions can easily replace zinc ions mixed in iron phosphate from the network framework.

[0039] 3. The application of ferromanganese phosphate synthesized from phosphating slag in the cathode material of this application uses ferromanganese phosphate powder synthesized from phosphating slag as raw material. The ferromanganese phosphate powder is mixed with lithium carbonate and glucose, then pure water is added, the mixture is sand-milled and mixed evenly, spray-dried, and sintered under nitrogen atmosphere protection to obtain lithium iron manganese phosphate cathode material. In battery performance tests, it shows higher specific capacity and good cycle stability, and improves the problem of low resource utilization efficiency of phosphating slag. Attached Figure Description

[0040] Figure 1 This is a SEM image of ferric manganese phosphate from Example 1 of this application;

[0041] Figure 2 This is the XRD pattern of ferric manganese phosphate from Example 1 of this application;

[0042] Figure 3 This is a SEM image of the lithium iron phosphate cathode material synthesized using Example 1 of this application;

[0043] Figure 4 This is the XRD pattern of the lithium iron phosphate cathode material synthesized using Example 1 of this application;

[0044] Figure 5 The charge-discharge curve of the CR2032 button half-cell assembled from lithium iron manganese phosphate synthesized in Example 1 of this application is shown in Example 1.

[0045] Figure 6 The image shows the 1C charge-discharge cycle capacity change curve of the CR2032 button half-cell assembled from lithium iron manganese phosphate synthesized in Example 1 of this application. Detailed Implementation

[0046] The following provides a further detailed description of this application.

[0047] Example

[0048] Example 1

[0049] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0050] S1. Take phosphate residue to test the manganese and iron content. The manganese content of phosphate residue is measured by perchloric acid oxidation method, and the iron content is measured by potassium dichromate titration method. Dissolve phosphate residue in concentrated phosphoric acid, stir at 60℃ for 2 hours, filter while hot to obtain clear filtrate A. Phosphate residue includes iron-based, manganese-based and zinc-based phosphate residue.

[0051] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 65°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is manganese dichloride and the ferrous salt is ferrous chloride.

[0052] S3. Add soluble zinc salt and complexing agent to 6% dilute phosphoric acid to prepare a mixed solution of 1% (w / w) zinc salt and 5% (w / w) complexing agent as the base solution. The complexing agent is ethylenediaminetetraacetic acid, and the soluble zinc salt is zinc chloride.

[0053] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3). Stir while adding, with a stirring speed of 150 rpm. After the addition is complete, heat to 70℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 80℃ for 1.5 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0054] Example 2

[0055] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0056] S1. Take the phosphate residue to test the manganese and iron content. The manganese content of the phosphate residue is measured by the perchloric acid oxidation method, and the iron content is measured by the potassium dichromate titration method. Dissolve the phosphate residue in concentrated phosphoric acid, stir at 70℃ for 2 hours, filter while hot to obtain clear filtrate A. The phosphate residue includes iron-based, manganese-based and zinc-based phosphate residues.

[0057] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 50°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is manganese nitrate and the ferrous salt is ferrous chloride.

[0058] S3. Add soluble zinc salt and complexing agent to 6% dilute phosphoric acid to prepare a mixed solution of 1% (w / w) zinc salt and 5% (w / w) complexing agent as the base solution. The complexing agent is ethylenediaminetetraacetic acid, and the soluble zinc salt is zinc chloride.

[0059] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3), while stirring at a speed of 200 rpm. After the addition is complete, heat to 60℃ and introduce oxygen. After reacting for 5 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 70℃ for 1.5 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0060] Example 3

[0061] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0062] S1. Take the phosphate residue to test the manganese and iron content. The manganese content of the phosphate residue is measured by the perchloric acid oxidation method, and the iron content is measured by the potassium dichromate titration method. Dissolve the phosphate residue in concentrated phosphoric acid, stir at 55℃ for 3 hours, filter while hot to obtain clear filtrate A. The phosphate residue includes iron-based, manganese-based and zinc-based phosphate residues.

[0063] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 55°C for 2 hours and filter while hot to obtain filtrate B. The divalent manganese salt is manganese dichloride and the ferrous salt is ferrous oxalate.

[0064] S3. Add soluble zinc salt and complexing agent to 6% dilute phosphoric acid to prepare a mixed solution of 1% (w / w) zinc salt and 5% (w / w) complexing agent as the base solution. The complexing agent is ethylenediaminetetraacetic acid, and the soluble zinc salt is zinc chloride.

[0065] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3). Stir while adding, with a stirring speed of 180 rpm. After the addition is complete, heat to 75℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 60℃ for 2 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0066] Example 4

[0067] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0068] S1. Take phosphate residue to test the manganese and iron content. The manganese content of phosphate residue is measured by perchloric acid oxidation method, and the iron content is measured by potassium dichromate titration method. Dissolve phosphate residue in concentrated phosphoric acid, stir at 40℃ for 5h, filter while hot to obtain clear filtrate A. Phosphate residue includes iron-based, manganese-based and zinc-based phosphate residue.

[0069] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 20% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 70°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is a combination of manganese dichloride, manganese nitrate and manganese oxalate, with a ratio of 1:0.5:2. The ferrous salt is a combination of ferrous chloride, ferrous nitrate and ferrous oxalate, with a ratio of 1:1:1.

[0070] S3. Add soluble zinc salt and complexing agent to 8% dilute phosphoric acid to prepare a mixed solution of 0.5% (w / w) zinc salt and 6% (w / w) complexing agent as the base solution. The complexing agent is ethylene glycol acid and the soluble zinc salt is zinc nitrate.

[0071] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(1 / 3). Stir while adding, with a stirring speed of 330 rpm. After the addition is complete, heat to 60℃ and introduce oxygen. After reacting for 6 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 60℃ for 3 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0072] Example 5

[0073] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0074] S1. Take the phosphate residue to test the manganese and iron content. The manganese content of the phosphate residue is measured by the perchloric acid oxidation method, and the iron content is measured by the potassium dichromate titration method. Dissolve the phosphate residue in concentrated phosphoric acid, stir at 70℃ for 2 hours, filter while hot to obtain clear filtrate A. The phosphate residue includes iron-based, manganese-based and zinc-based phosphate residues.

[0075] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese accounts for 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 40°C for 4 hours and filter while hot to obtain filtrate B. The divalent manganese salt is a combination of manganese nitrate and manganese oxalate, with a ratio of manganese nitrate to manganese oxalate of 1:2. The ferrous salt is a combination of ferrous chloride and ferrous oxalate, with a ratio of ferrous chloride to ferrous oxalate of 1:0.8.

[0076] S3. Add soluble zinc salt and complexing agent to 5% dilute phosphoric acid to prepare a 3% (w / w) zinc salt and 1% (w / w) complexing agent mixture as the base solution. The complexing agent is a combination of ethylenediaminetetraacetic acid, citric acid, succinic acid, and ethylene glycol, with a ratio of 1:1:1:1. The soluble zinc salt is a combination of zinc chloride, zinc nitrate, and zinc acetate, with a ratio of 1:0.5:2.

[0077] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(3 / 4). Stir while adding, with a stirring speed of 120 rpm. After the addition is complete, heat to 75℃ and introduce oxygen. After reacting for 2 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 80℃ for 1 hour, grind, and sieve to obtain ferromanganese phosphate powder.

[0078] Example 6

[0079] A method for synthesizing ferromanganese phosphate using phosphating slag includes the following steps:

[0080] S1. Take the phosphate residue to test the manganese and iron content. The manganese content of the phosphate residue is measured by the perchloric acid oxidation method, and the iron content is measured by the potassium dichromate titration method. Dissolve the phosphate residue in concentrated phosphoric acid, stir at 55℃ for 3.5h, filter while hot to obtain clear filtrate A. The phosphate residue includes iron-based, manganese-based and zinc-based phosphate residues.

[0081] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 35% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 55°C for 2.5 hours and filter while hot to obtain filtrate B. The divalent manganese salt is a combination of manganese dichloride and manganese nitrate, with a ratio of manganese dichloride and manganese nitrate of 1:1. The ferrous salt is ferrous nitrate.

[0082] S3. Add soluble zinc salt and complexing agent to 6.5% dilute phosphoric acid to prepare a mixed solution of 1.8% (w / w) zinc salt and 3.5% (w / w) complexing agent as the base solution. The complexing agent is a combination of citric acid and ethylene glycol acid in a ratio of 1:2. The soluble zinc salt is a combination of zinc chloride and zinc acetate in a ratio of 1:0.5.

[0083] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(1 / 2). Stir while adding, with a stirring speed of 225 rpm. After the addition is complete, heat to 67.5℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain manganese iron phosphate precipitate.

[0084] S5. Dry the precipitate of manganese phosphate at 70℃ for 2 hours, grind it, and sieve it to obtain manganese phosphate powder.

[0085] Example 7

[0086] The difference between Example 7 and Example 1 is that the divalent manganese salt is manganese carbonate and the ferrous salt is ferrous sulfate.

[0087] Example 8

[0088] The difference between Example 8 and Example 1 is that the complexing agent is triethylphosphine.

[0089] Example 9

[0090] The difference between Example 9 and Example 1 is that the soluble zinc salt is zinc sulfate.

[0091] Implement comparative

[0092] Comparative Example 1

[0093] The difference between Comparative Example 1 and Example 1 is that soluble zinc salts and complexing agents are not added in the preparation of the base solution. Specifically, the following steps are included:

[0094] S1. Take phosphate residue to test the manganese and iron content. The manganese content of phosphate residue is measured by perchloric acid oxidation method, and the iron content is measured by potassium dichromate titration method. Dissolve phosphate residue in concentrated phosphoric acid, stir at 60℃ for 2 hours, filter while hot to obtain clear filtrate A. Phosphate residue includes iron-based, manganese-based and zinc-based phosphate residue.

[0095] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 65°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is manganese dichloride and the ferrous salt is ferrous chloride.

[0096] S3. Prepare a 6% dilute phosphoric acid solution as the base solution;

[0097] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3). Stir while adding, with a stirring speed of 150 rpm. After the addition is complete, heat to 70℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 80℃ for 1.5 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 1 is that no soluble zinc salt is added in the preparation of the base solution. Specifically, it includes the following steps: S1. Take phosphating slag and test its manganese and iron content. The manganese content of the phosphating slag is measured by perchloric acid oxidation method, and the iron content is measured by potassium dichromate titration method. Dissolve the phosphating slag in concentrated phosphoric acid, stir at 60°C for 2 hours, filter while hot, and obtain clear filtrate A. The phosphating slag includes iron-based, manganese-based, and zinc-based phosphating slag.

[0100] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 65°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is manganese dichloride and the ferrous salt is ferrous chloride.

[0101] S3. Add ethylenediaminetetraacetic acid (EDTA) as a complexing agent to 6% dilute phosphoric acid to prepare a 5% (w / w) complexing agent solution as the base solution.

[0102] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3). Stir while adding, with a stirring speed of 150 rpm. After the addition is complete, heat to 70℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 80℃ for 1.5 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0103] Implement Comparative Example 3

[0104] The difference between Comparative Example 3 and Example 1 is that no complexing agent is added in the preparation of the base solution, and the specific steps include:

[0105] S1. Take phosphate residue to test the manganese and iron content. The manganese content of phosphate residue is measured by perchloric acid oxidation method, and the iron content is measured by potassium dichromate titration method. Dissolve phosphate residue in concentrated phosphoric acid, stir at 60℃ for 2 hours, filter while hot to obtain clear filtrate A. Phosphate residue includes iron-based, manganese-based and zinc-based phosphate residue.

[0106] S2. Based on the manganese and iron content measured in step S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 50% and the remainder is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 65°C for 1 hour and filter while hot to obtain filtrate B. The divalent manganese salt is manganese dichloride and the ferrous salt is ferrous chloride.

[0107] S3. Add a soluble zinc salt to a 6% dilute phosphoric acid solution to prepare a 1% (w / w) zinc salt solution as the base solution. The soluble zinc salt is zinc chloride.

[0108] S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(2 / 3). Stir while adding, with a stirring speed of 150 rpm. After the addition is complete, heat to 70℃ and introduce oxygen. After reacting for 4 hours, filter while hot to obtain ferromanganese phosphate precipitate. S5. Dry the ferromanganese phosphate precipitate at 80℃ for 1.5 hours, grind, and sieve to obtain ferromanganese phosphate powder.

[0109] Application examples

[0110] Application Example 1

[0111] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 1 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose in a molar ratio of 1:0.51:0.09. Then, pure water was added at a ratio of 1:4 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 50 minutes, then lithium carbonate and milled for 30 minutes, and finally glucose and milled for 10 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 630°C in a nitrogen-filled furnace to obtain lithium manganese phosphate cathode material. This lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form cathode sheets, which were then assembled into CR2032 button half-cells.

[0112] Application Example 2

[0113] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 2 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose in a molar ratio of 1:0.51:0.09. Then, pure water was added at a ratio of 1:4 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 45 minutes, then lithium carbonate and milled for 40 minutes, and finally glucose and milled for 5 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 630°C in a nitrogen-filled furnace to obtain lithium manganese phosphate cathode material. This lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form cathode sheets, which were then assembled into CR2032 button half-cells.

[0114] Application Example 3

[0115] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 1 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose in a molar ratio of 1:0.51:0.09. Then, pure water was added at a ratio of 1:4 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 55 minutes, then lithium carbonate and milled for 20 minutes, and finally glucose and milled for 15 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 630°C in a nitrogen-filled furnace to obtain lithium manganese phosphate cathode material. This lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form cathode sheets, which were then assembled into CR2032 button half-cells.

[0116] Application Example 4

[0117] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 4 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose in a molar ratio of 1:0.40:0.20. Then, pure water was added at a ratio of 1:3 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 53 minutes, then lithium carbonate and milled for 28 minutes, and finally glucose and milled for 12 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 635°C in a nitrogen-filled furnace to obtain the lithium manganese phosphate cathode material. The lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form a cathode sheet, which was then assembled into a CR2032 button half-cell.

[0118] Application Example 5

[0119] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 5 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose at a molar ratio of 1:0.60:0.01. Then, pure water was added at a ratio of 1:5 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 46 minutes, then lithium carbonate was added and milled for 24 minutes, and finally glucose was added and milled for 13 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 635°C in a nitrogen-filled furnace to obtain lithium manganese phosphate cathode material. The lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form a cathode sheet, which was then assembled into a CR2032 button half-cell.

[0120] Application Example 6

[0121] Using the ferromanganese phosphate powder synthesized from phosphate slag in Example 6 as raw material, the ferromanganese phosphate powder was mixed with lithium carbonate and glucose at a molar ratio of 1:0.50:0.10. Then, pure water was added at a ratio of 1:4 for the mixture of ferromanganese phosphate powder, lithium carbonate, glucose, and pure water. The mixture was first added and milled for 41 minutes, then lithium carbonate was added and milled for 22 minutes, and finally glucose was added and milled for 11 minutes. The D50 particle size was less than 0.5 μm. After milling and mixing, the mixture was spray-dried at an inlet air temperature of 230°C and an outlet temperature of 95°C. The mixture was then sintered at 631°C in a nitrogen-filled furnace to obtain lithium manganese phosphate cathode material. The lithium manganese phosphate cathode material was mixed with superconducting carbon black, adhesive, and NMP and coated onto aluminum foil to form cathode sheets, which were then assembled into CR2032 button half-cells.

[0122] Application Example 7

[0123] The difference between Application Example 7 and Application Example 1 is that Application Example 7 uses the manganese ferrophosphate powder synthesized from phosphating slag in Example 7 as a raw material.

[0124] Application Example 8

[0125] The difference between Application Example 8 and Application Example 1 is that Application Example 8 uses the manganese ferrophosphate powder synthesized from phosphating slag in Example 8 as a raw material.

[0126] Application Example 9

[0127] The difference between Application Example 9 and Application Example 1 is that Application Example 9 uses the manganese iron phosphate powder synthesized from phosphating slag in Example 9 as a raw material.

[0128] Application of comparative examples

[0129] Application Comparative Example 1

[0130] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses manganese ferrophosphate powder synthesized from phosphate slag as raw material.

[0131] Application Comparative Example 2

[0132] The difference between Comparative Example 2 and Comparative Example 1 is that Comparative Example 2 uses manganese ferrophosphate powder synthesized from phosphate slag as raw material.

[0133] Application Comparative Example 3

[0134] The difference between Comparative Example 3 and Comparative Example 1 is that Comparative Example 3 uses manganese ferrophosphate powder synthesized from phosphate slag as raw material.

[0135] Performance testing

[0136] The manganese iron phosphate prepared in Example 1 and the lithium manganese iron phosphate cathode material used in Example 1 were characterized by field emission scanning electron microscopy (SEM), and the results are as follows: Figure 1 and Figure 3 As shown. Figure 1 The manganese iron phosphate particles shown in Example 1 range from 50 nm to several hundred nanometers, and the particles are very small. Figure 3 The results show that the particle size of lithium manganese iron phosphate cathode material can be as small as tens of nanometers, and even when it is agglomerated, the particle size is still around 1 μm.

[0137] The manganese iron phosphate prepared in Example 1 and the lithium manganese iron phosphate cathode material used in Example 1 were characterized by X-ray powder diffraction (XRD), and the results are as follows: Figure 2 and Figure 4 As shown. Figure 2 The results show that the manganese iron phosphate material prepared in Example 1 is a pure phase of (Fe,Mn)PO4 with no obvious impurities generated. Figure 4 This illustrates the synthesis of lithium manganese iron phosphate and LiFe from lithium manganese iron phosphate in Example 1. 0.5 Mn 0.5 The XRD patterns of the PO4 standard phase are consistent, and there are basically no impurities.

[0138] Performance testing was conducted on the lithium manganese iron phosphate cathode material and the assembled CR2032 button half-cell in corresponding use cases 1-9 and application comparison examples.

[0139] The D50 of lithium manganese iron phosphate cathode material was determined with reference to GB / T 19077-2016 "Particle size distribution laser diffraction method".

[0140] The specific surface area of ​​lithium manganese iron phosphate cathode material was determined according to GB / T 19587-2017 "Determination of specific surface area of ​​solid materials by gas adsorption BET method".

[0141] The discharge specific capacity, initial coulombic efficiency, and discharge specific capacity rate after 50 1C charge-discharge cycles of CR2032 button half-cell were tested in accordance with SJ / T 11793-2022 "Test Method for Electrochemical Performance of Electrode Materials of Lithium-ion Batteries".

[0142] Figure 5 The charge-discharge curve of the CR2032 button half-cell assembled from lithium iron manganese phosphate synthesized in Example 1 of this application is shown in Example 1. Figure 5 The results show that the lithium iron manganese phosphate synthesized from the iron manganese phosphate in Example 1, when assembled into a CR2032 button half-cell, achieves a discharge specific capacity of 163.9 mAh / g and an initial coulombic efficiency of 99.97%.

[0143] Figure 6 The image shows the 1C charge-discharge cycle capacity change curve of the CR2032 button half-cell assembled from lithium iron manganese phosphate synthesized in Example 1 of this application. Figure 6 The results show that the lithium iron phosphate synthesized from manganese iron phosphate in Example 1, when assembled into a CR2032 button half-cell, retains approximately 97% of its capacity after 50 1C charge-discharge cycles.

[0144] Other test results are shown in the table below:

[0145] Table 1 Test Results

[0146]

[0147]

[0148] Comparing Application Examples 1-9 with Comparative Example 1, the particle size D50 of the lithium manganese iron phosphate cathode materials in Application Examples 1-9 is approximately 1 μm, significantly smaller than that in Comparative Example 1. The specific surface area of ​​the lithium manganese iron phosphate cathode materials in Application Examples 1-9 is significantly larger than that in Comparative Example 1, indicating that the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate of this application has superior performance. The electrochemical performance of the CR2032 button half-cells from Application Examples 1-9, including discharge specific capacity, initial coulombic efficiency, and discharge specific capacity after 50 1C charge-discharge cycles, is significantly better than that of Comparative Example 1, demonstrating that the lithium manganese iron phosphate cathode material prepared in this application exhibits higher specific capacity and better cycle stability in battery performance testing, improving the problem of low resource utilization efficiency of phosphating slag. It also shows that soluble zinc salts and complexing agents have a significant impact on the performance of synthesized manganese iron phosphate and the performance of the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate.

[0149] Comparing Application Examples 1-9 with Comparative Example 2, the particle size D50 of the lithium manganese iron phosphate cathode material in Application Examples 1-9 is significantly smaller than that in Comparative Example 2, and the specific surface area of ​​the lithium manganese iron phosphate cathode material in Application Examples 1-9 is significantly larger than that in Comparative Example 2, indicating that the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate of this application has superior performance. The electrochemical performance of the CR2032 button half-cells in Application Examples 1-9, including discharge specific capacity, initial coulombic efficiency, and discharge specific capacity after 50 1C charge-discharge cycles, is significantly better than that of Comparative Example 2, indicating that soluble zinc salt has a significant impact on the performance of the synthesized manganese iron phosphate and the performance of the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate.

[0150] Comparing Application Examples 1-9 with Comparative Example 3, the particle size D50 of the lithium manganese iron phosphate cathode material in Application Examples 1-9 is significantly smaller than that in Comparative Example 3, and the specific surface area of ​​the lithium manganese iron phosphate cathode material in Application Examples 1-9 is significantly larger than that in Comparative Example 3, indicating that the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate of this application has superior performance. The electrochemical performance of the CR2032 button half-cells in Application Examples 1-9, including discharge specific capacity, initial coulombic efficiency, and discharge specific capacity after 50 1C charge-discharge cycles, is significantly better than that of Comparative Example 3, indicating that the complexing agent has a significant impact on the performance of the synthesized manganese iron phosphate and the performance of the lithium manganese iron phosphate cathode material prepared from the synthesized manganese iron phosphate.

[0151] In summary, the synergistic effect of the complexing agent and soluble zinc salt refines the ferromanganese phosphate particles and improves their purity. This is because when a certain concentration of zinc ions is present in the solution, the addition of a macromolecular complexing agent helps the zinc ions assist the complexing agent in forming a uniform and stable network framework in the solution, resulting in more uniform dispersion of manganese and iron ions and easier formation of small-sized ferromanganese phosphate particles. After dispersion in solution, the macromolecular complexing agent can form a large molecular network framework, constructing a microscopic reaction synthesis chamber for ferromanganese phosphate, significantly reducing the size of the synthesized ferromanganese phosphate particles, obtaining ferromanganese phosphate particles with a large specific surface area, and improving its application effect in lithium iron phosphate cathode materials. Divalent manganese ions and zinc ions have similar ionic radii and outer electron structures. Divalent manganese ions can easily replace zinc ions mixed in ferromanganese phosphate, without worrying about the addition of soluble zinc salts reducing the purity of the resulting ferromanganese phosphate phase. Therefore, the addition of zinc salts does not affect the high-purity preparation of ferromanganese phosphate.

[0152] The above specific embodiments are merely explanations of this application and are not intended to limit this application. After reading this specification, those skilled in the art can make modifications to this application without contributing any inventive step, but all such modifications should be covered within the protection scope of this application.

Claims

1. A method for synthesizing ferromanganese phosphate using phosphating slag, characterized in that: It includes the following steps: S1. Take phosphate residue, measure the manganese content by perchloric acid oxidation method and the iron content by potassium dichromate titration method, dissolve the phosphate residue in concentrated phosphoric acid, stir at 40-70℃ for 2-5 hours, filter while hot to obtain clear filtrate A, wherein the phosphate residue includes iron-based, manganese-based and zinc-based phosphate residues. S2. Based on the manganese and iron content measured in S1, weigh out divalent manganese salt and ferrous salt and add them to filtrate A. According to the percentage content of manganese and iron moles, manganese is 20%-50% and the rest is iron. The above-mentioned manganese and iron components come from divalent manganese salt and ferrous salt. Stir at 40-70℃ for 1-4 hours and filter while hot to obtain filtrate B. S3. Add soluble zinc salt and complexing agent to dilute phosphoric acid with a concentration of 5-8%. The complexing agent is one or more of ethylenediaminetetraacetic acid, citric acid, succinic acid, and ethylene glycol. Prepare a mixed solution of zinc salt with a mass concentration of 0.5-3% and complexing agent with a mass concentration of 1-6% as the base solution. Zinc ions and complexing agent work together to form a uniform and stable network framework, which makes manganese ions and iron ions more evenly dispersed. S4. Slowly add filtrate B to the base liquid, with a mass ratio of base liquid to filtrate B of 1:(1 / 3-3 / 4). Stir while adding, with a stirring speed of 120-330 rpm. After the addition is complete, heat to 60-75℃ and introduce oxygen. After reacting for 2-6 hours, filter while hot to obtain manganese iron phosphate precipitate. S5. Dry the precipitate of manganese phosphate at 60-80℃ for 1-3 hours, grind it, and sieve it to obtain manganese phosphate powder.

2. The method for synthesizing ferromanganese phosphate using phosphating slag according to claim 1, characterized in that: The divalent manganese salt is one or a combination of manganese dichloride, manganese nitrate, and manganese oxalate, and the ferrous salt is one or a combination of ferrous chloride, ferrous nitrate, and ferrous oxalate.

3. The method for synthesizing ferromanganese phosphate using phosphating slag according to claim 1, characterized in that: The soluble zinc salt is one or a combination of zinc chloride, zinc nitrate, and zinc acetate.

4. The application of the manganese iron phosphate synthesized from phosphating slag as described in any one of claims 1 to 3 in cathode materials, characterized in that: It includes the following steps: Using ferromanganese phosphate powder synthesized from phosphate slag as raw material, the ferromanganese phosphate powder is mixed with lithium carbonate and glucose, then pure water is added, the mixture is sand-milled and mixed evenly, spray-dried, and sintered under nitrogen atmosphere protection to obtain lithium manganese iron phosphate cathode material.

5. The application of manganese iron phosphate synthesized from phosphating slag according to claim 4 in cathode materials, characterized in that: The molar ratio of manganese iron phosphate powder, lithium carbonate, and glucose is 1:(0.40-0.60):(0.01-0.20).

6. The application of manganese iron phosphate synthesized from phosphating slag according to claim 4 in cathode materials, characterized in that: The ratio of the mixture of manganese iron phosphate powder, lithium carbonate, glucose, and pure water is 1:(3-5).

7. The application of manganese iron phosphate synthesized from phosphating slag according to claim 4 in cathode materials, characterized in that: When the sand is milled and mixed, first add manganese iron phosphate and mill for 45-55 minutes, then add lithium carbonate and mill for 20-40 minutes, and finally add glucose and mill for 5-15 minutes. The D50 particle size is less than 0.5μm.

8. The application of manganese iron phosphate synthesized from phosphating slag according to claim 4 in cathode materials, characterized in that: The sintering temperature is 620-640℃.

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