Preparation method and application of manganese iron phosphate precursor
By preparing manganese iron phosphate precursors through electrodeposition, the problems of complex preparation methods and uneven product performance in existing technologies have been solved, realizing the preparation of efficient and environmentally friendly lithium manganese iron phosphate cathode materials and improving the electrochemical performance of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI XINGFA CHEM GRP CO LTD
- Filing Date
- 2024-06-24
- Publication Date
- 2026-06-19
AI Technical Summary
Existing methods for preparing manganese iron phosphate precursors suffer from problems such as complex operation, low production efficiency, high equipment requirements, irregular product morphology, uneven particle size distribution, easy agglomeration, and impurity residues, which affect material properties.
Manganese iron phosphate precursor was prepared by electrodeposition. By preparing an electrolyte solution, manganese, iron and phosphorus sources were dissolved in water, and an electrodeposition reaction was carried out. The precursor was collected, washed and dried to obtain manganese iron phosphate precursor, achieving atomic-level distribution of manganese, iron and phosphorus elements.
The process was simplified, energy consumption was reduced, and the electrochemical performance of lithium manganese iron phosphate cathode material was improved. The particle morphology was more rounded and the particle size was more uniform, which solved the problems of irregular morphology and uneven particle size in traditional methods.
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Figure CN118702084B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of the preparation of the precursor of the cathode material of lithium-ion batteries, and specifically relates to a preparation method and application of a manganese iron phosphate precursor. Background Art
[0002] Lithium manganese iron phosphate (LMFP), as a new type of cathode material for lithium-ion batteries, has gradually received extensive attention due to its high energy density, good cycling performance and relatively low cost. At the same specific capacity, the energy density of lithium manganese iron phosphate batteries is 10% - 20% higher than that of lithium iron phosphate batteries. Compared with ternary materials, lithium manganese iron phosphate has a similar energy density, but higher safety and relatively lower price. Therefore, lithium manganese iron phosphate is expected to become the cathode material of the new generation of high-energy density power batteries, and its precursor manganese iron phosphate (Mn x Fe 1-x PO4, 0 < x < 1) has also received more and more attention.
[0003] The performance indexes such as the composition, structure, particle size, and morphology of manganese iron phosphate play a crucial role in the electrochemical performance of the synthesized lithium manganese iron phosphate material. Therefore, studying the synthesis technology of manganese iron phosphate is of great significance for improving the electrochemical performance of lithium manganese iron phosphate cathode materials and promoting their industrial applications. At present, the preparation methods of manganese iron phosphate precursor materials are similar to those of iron phosphate, mainly including coprecipitation, hydrothermal method, high-temperature solid-state reaction method, spray drying method, etc. Selecting different synthesis methods has a very important impact on the particle size and morphology structure of manganese iron phosphate, and thus determines the electrochemical performance of lithium manganese iron phosphate cathode materials to a certain extent.
[0004] CN113659134A discloses a method for preparing nano-scale lithium manganese iron phosphate materials using the co-crystallization method. Specifically, a manganese source, an iron source, and a phosphorus source are respectively dissolved in an aqueous solution, then mixed in proportion and the pH is adjusted to 1 - 3, stirred and filtered, an oxidant is added for oxidation, and after stirring and reacting, pressure filtration and drying are carried out to obtain a nano-scale spherical Mn x Fe 1-x PO4 intermediate. After making this intermediate into a lithium manganese iron phosphate cathode material, the discharge at 0.2C is 157.68 mAh / g. CN105449207A discloses a preparation method and product of manganese iron phosphate, and a manganese iron phosphate is prepared by the hydrothermal method; the manganese source and the iron source are respectively dissolved in appropriate amounts of water, and appropriate amounts of phosphorus source are respectively added, then the two mixed solutions are transferred into a reaction kettle, the solution pH is adjusted < 2, and then an oxidant and a dispersant are added, and the temperature is raised for reaction to obtain a manganese iron phosphate product, which has the advantages of high purity and uniform particle size distribution. CN105355885A discloses a composite cathode material for lithium-ion batteries LiMn 1-x Fe xThe synthesis method of PO4 / C is as follows: Iron, phosphorus, manganese, and organic carbon sources are mixed in proportions according to the desired molecular formula of the cathode material. The mixture is then dry-milled in ball milling media using high-energy methods to obtain a precursor mixture. Finally, the precursor mixture is heat-treated at 500-700℃ under an inert atmosphere to obtain the precursor (Mn). 1-x Fe x CN114583155A discloses a method for preparing lithium iron phosphate material, which prepares a precursor of lithium iron manganese phosphate by spray drying. Specifically, an aqueous solution of phosphate salt is added to a mixed aqueous solution containing an iron source and a manganese source to react and obtain a mixture. The mixture is then ground and spray dried. The powder obtained by spray drying is then sintered to obtain a precursor of lithium iron manganese phosphate. CN106935851A discloses a lithium iron manganese phosphate material and its preparation method, as well as battery slurry, positive electrode and lithium battery. It uses a liquid-phase ultrasonic method to synthesize a doped lithium iron manganese phosphate precursor. The preparation method is as follows: a phosphorus source is dissolved in a first solution to prepare solution A, and at least one of an iron source, a manganese source and a M source is dissolved in a second solution to prepare solution B. Then, under ultrasonic reaction conditions, solutions A and B are mixed and reacted in parallel. After drying, an amorphous lithium iron manganese phosphate precursor is obtained.
[0005] However, the co-precipitation method is complex, requiring repeated filtration, washing, drying, and dehydration, resulting in low production efficiency and a long process flow. The hydrothermal method produces products with uniform particle size and controllable morphology, but it requires sophisticated equipment and involves a relatively complex preparation process. While the high-temperature solid-state method is easy to implement for large-scale production, the resulting products have irregular morphology, uneven particle size distribution, are difficult to control, and are prone to agglomeration, all of which affect material performance. Spray drying generates a large amount of byproduct salt, and subsequent calcination releases a large amount of harmful gases and leaves residual impurities, affecting precursor performance. Therefore, it is necessary to develop a simple and efficient preparation method to synthesize high-performance manganese iron phosphate precursors, simplifying the synthesis and improving the performance of lithium manganese iron phosphate cathode materials. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a method for preparing and applying a manganese iron phosphate precursor. The method employs electrodeposition to prepare the manganese iron phosphate precursor, which reduces energy consumption, simplifies the process, effectively achieves atomic-level distribution of manganese, iron, and phosphorus elements, and improves the electrochemical performance of the prepared lithium manganese iron phosphate cathode material.
[0007] To achieve the above objectives, the present invention provides a method for preparing a manganese iron phosphate precursor, the method comprising the following steps:
[0008] (1) Preparation of electrolyte solution: Dissolve manganese source, iron source and phosphorus source in water and mix well to obtain electrolyte solution;
[0009] (2) Electrodeposition reaction: The electrolyte solution is placed in the electroplating tank to react and obtain manganese iron phosphate;
[0010] (3) Collect manganese iron phosphate, wash and dry to obtain manganese iron phosphate precursor.
[0011] Preferably, the atomic molar ratio of manganese, iron and phosphorus in the electrolyte solution of step (1) is x:(1-x):(1-5), where 0<x<1.
[0012] More preferably, the manganese source is any one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; the iron source is any one of ferrous sulfate, ferrous chloride, and ferrous nitrate; and the phosphorus source is any one of phosphoric acid, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate, and trisodium phosphate.
[0013] Preferably, the pH of the electrolyte solution in step (1) is ≤1.
[0014] Preferably, the reaction temperature in step (2) is 25-60℃, and the reaction current density is 500-3000 A / m. 2 .
[0015] Preferably, the electroplating tank in step (2) is provided with a working electrode and a counter electrode.
[0016] More preferably, the working electrode is any one of a titanium plate, a graphite plate, or a platinum plate; and the counter electrode is any one of a stainless steel plate, a titanium plate, a graphite plate, or a platinum plate.
[0017] Preferably, the atomic molar ratio of manganese, iron and phosphorus in the manganese iron phosphate precursor described in step (3) is x:(1-x):1, where 0<x<1.
[0018] Preferably, the washing method in step (3) includes water washing and alcohol washing, each washing 2-5 times; the drying conditions are drying at 70-90℃ for 20-26 hours.
[0019] More preferably, the washing method is any one of vacuum filtration, pressure filtration, and centrifugation; the drying method is blower drying, flash drying, and spray drying.
[0020] The present invention also provides an application of the manganese iron phosphate precursor prepared by the above-mentioned method for preparing lithium manganese iron phosphate cathode materials.
[0021] Preferably, the application method is to use a high-temperature solid-state method, using manganese iron phosphate precursor as raw material, and mix and sinter it with lithium source and carbon source to prepare lithium iron manganese phosphate cathode material.
[0022] The beneficial effects of this invention are as follows:
[0023] 1. Manganese ferric phosphate was prepared by mixing manganese, iron and phosphorus sources using an electrodeposition method, which effectively achieved atomic-level distribution of manganese, iron and phosphorus elements, and the prepared manganese ferric phosphate precursor was a single-phase homogeneous solid solution.
[0024] 2. The lithium manganese iron phosphate precursor is prepared by electrodeposition, which is a simple and efficient process that does not require high temperature conditions, and is energy-efficient and environmentally friendly.
[0025] 3. The lithium manganese iron phosphate prepared from the manganese iron phosphate precursor obtained by electrodeposition has a more rounded and spherical particle morphology and achieves a better particle size distribution. Therefore, it effectively alleviates the balance problem between electrical properties, compaction, and specific surface area of lithium manganese iron phosphate, and avoids the problems of irregular particle morphology and unreasonable particle size distribution in traditional preparation methods. Therefore, this process has good application prospects. Attached Figure Description
[0026] Figure 1 The image shows the XRD pattern of the manganese iron phosphate precursor prepared in Example 1.
[0027] Figure 2 The charge-discharge curves of the lithium iron manganese phosphate cathode material prepared from the iron manganese phosphate precursor prepared in Example 10 at 0.1C and 1C are shown.
[0028] Figure 3 The charge-discharge curves of the lithium iron manganese phosphate cathode material prepared using the iron manganese phosphate precursor prepared in Comparative Example 6 in Example 10 are shown at 0.1C and 1C. Detailed Implementation
[0029] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.
[0030] Example 1
[0031] (1) Preparation of electrolyte solution: Dissolve manganese sulfate and ferrous sulfate in deionized water to prepare a mixed metal ion solution. Then add 85% phosphoric acid solution to the solution and mix well to obtain the electrolyte solution. The atomic molar ratio of manganese, iron and phosphorus in the solution is 0.6:0.4:2 and the pH value of the electrolyte solution is 0.8.
[0032] (2) Electrodeposition reaction: A platinum plate is used as the working electrode and connected to the positive terminal of the power supply, and a graphite plate is used as the counter electrode and connected to the negative terminal of the power supply. Then, the electrolyte solution is placed in the electroplating tank, the solution temperature is set to 40℃, and the current density at the working electrode is set to 1000A / m. 2 Electrodeposition reaction is carried out;
[0033] (3) After reacting for 1 h, manganese iron phosphate was collected at the working electrode and then placed in a vacuum filtration and washing device and repeatedly filtered and washed 3 times with deionized water, then filtered and washed 3 times with ethanol. Finally, the washing product was placed in a 90℃ forced-air drying oven and dried for 24 h to obtain the manganese iron phosphate precursor ( Figure 1 ).
[0034] Example 2
[0035] The method and steps are the same as in Example 1, except that manganese sulfate in step (1) is replaced with manganese chloride and ferrous sulfate is replaced with ferrous chloride to prepare manganese ferric phosphate precursor.
[0036] Example 3
[0037] The method and steps are the same as in Example 1, except that the phosphoric acid in step (1) is replaced with ammonium dihydrogen phosphate to prepare the manganese iron phosphate precursor.
[0038] Example 4
[0039] The method and steps are the same as in Example 1, except that the current density in step (2) is changed to 1200 A / m. 2 The manganese iron phosphate precursor was prepared.
[0040] Example 5
[0041] The method and steps are the same as in Example 1, except that the phosphoric acid in step (1) is replaced with trisodium phosphate, and the pH of the electrolyte solution is 0.5 to prepare the manganese phosphate precursor.
[0042] Example 6
[0043] The method and steps are the same as in Example 1, except that the molar ratio of manganese, iron and phosphorus atoms in the electrolyte solution in step (1) is changed to 0.8:0.2:1 to prepare manganese phosphate precursor.
[0044] Example 7
[0045] The method and steps are the same as in Example 1, except that the molar ratio of manganese, iron and phosphorus atoms in the electrolyte solution in step (1) is changed to 0.3:0.7:5 to prepare manganese phosphate precursor.
[0046] Example 8
[0047] The method and steps are the same as in Example 1, except that the temperature of the electrodeposition reaction in step (2) is changed to 25°C and the current density is changed to 500A / m. 2 The reaction time was 2 h, and the manganese phosphate precursor was prepared.
[0048] Example 9
[0049] The method and steps are the same as in Example 1, except that the temperature of the electrodeposition reaction in step (2) is changed to 60°C and the current density is changed to 3000 A / m. 2 The reaction time was 0.2 h, and the manganese phosphate precursor was prepared.
[0050] Comparative Example 1
[0051] The method and steps are the same as in Example 1, except that the molar ratio of manganese, iron and phosphorus atoms in the electrolyte solution in step (1) is changed to 0.6:0.4:6 to prepare manganese phosphate precursor.
[0052] Comparative Example 2
[0053] The method and steps are the same as in Example 1, except that the molar ratio of manganese, iron and phosphorus atoms in the electrolyte solution in step (1) is changed to 0.6:0.4:0.8 to prepare manganese phosphate precursor.
[0054] Comparative Example 3
[0055] The method and steps are the same as in Example 1, except that the electrodeposition reaction temperature in step (2) is changed to 20°C and the current density is changed to 400 A / m. 2 The reaction time was 0.5 h, and the manganese phosphate precursor was prepared.
[0056] Comparative Example 4
[0057] The method and steps are the same as in Example 1, except that the electrodeposition reaction temperature in step (2) is changed to 70°C and the current density is changed to 3500 A / m. 2 The reaction time was 1 hour, and the manganese phosphate precursor was prepared.
[0058] Comparative Example 5
[0059] The manganese phosphate precursor was prepared by co-precipitation, and the specific method is as follows:
[0060] (1) Weigh 0.4437 mol manganese sulfate monohydrate and 0.1109 mol ferrous sulfate heptahydrate into 200 mL of deionized water, and add 1 mol sodium hydroxide solution (concentration of 10 mol / L) while stirring to dissolve. Adjust the pH of the system to 8.51 to obtain a mixed solution.
[0061] (2) After the sodium hydroxide solution is added, continue stirring for 15 minutes, and while stirring the mixture, add 0.5876 mol of hydrogen peroxide solution (mass fraction of 30%) at a feed rate of 50 r / min to carry out the oxidation reaction. After the oxidation reaction is completed, continue stirring for 30 minutes to obtain the oxidized solution.
[0062] (3) The oxidizing solution was placed in a reaction vessel and heated to 85°C. Then, 0.6557 mol / L of phosphoric acid solution (mass fraction of 85%) was added. After reacting for 5 hours, the solution was cooled to room temperature to obtain the reaction solution.
[0063] (4) Separate the reaction solution into solid and liquid phases, and wash, filter, and dry the solid precipitate to obtain the manganese iron phosphate precursor Mn. 0.8 Fe 0.2 PO4·H2O.
[0064] Comparative Example 6
[0065] The method and steps are the same as in Example 1, except that the pH of the electrolyte solution in step (1) is changed to 1.5 to prepare the manganese iron phosphate precursor.
[0066] Results Testing: The manganese iron phosphate precursors prepared in the above examples and comparative examples were tested for their tap density, specific surface area, and other performance parameters. The results are shown in Table 1.
[0067] Table 1. Performance parameters of manganese iron phosphate precursor:
[0068]
[0069] Example 10
[0070] The lithium iron phosphate cathode material was prepared using the precursors obtained from Examples 1-9 and Comparative Examples 1-6. The specific steps are as follows:
[0071] (1) Material mixing and grinding: Take 100g of manganese ferric phosphate precursor, 22.13g of lithium carbonate, 11.48g of glucose and 282g of deionized water, mix and grind to the particle size D of the slurry. 50 ≤350 nm;
[0072] (2) Spray drying: The slurry after sand milling is spray dried at 85°C so that the moisture content of the powder obtained after drying is ≤2%;
[0073] (3) Sintering: The powder is placed under nitrogen protection and heated to 720°C at a rate of 2°C / min, and sintered for 6 hours to obtain black material;
[0074] (4) Physically crush the black material to a particle size D 50 =1.0±0.2 μm, thus obtaining lithium manganese iron phosphate cathode material.
[0075] The lithium iron phosphate cathode material prepared using the manganese iron phosphate precursor obtained in Example 1 was charged and discharged at 0.1C and 1C, respectively, and charge-discharge curves were obtained. Figure 2 ).
[0076] Comparative Example 7
[0077] The method and steps are the same as in Example 10, except that the raw material components in step (1) are changed to 100 g of iron phosphate, 59.51 g of manganese tetroxide, 49.13 g of lithium carbonate, 89.60 g of ammonium dihydrogen phosphate, 32.79 g of glucose, and 584 g of deionized water to prepare lithium manganese iron phosphate cathode material. The lithium manganese iron phosphate cathode material is charged and discharged at 0.1C and 1C respectively to obtain charge and discharge curves ( Figure 3 ).
[0078] The lithium manganese iron phosphate cathode materials prepared under different conditions in Example 10 and the lithium manganese iron phosphate cathode materials prepared in Comparative Example 7 were used to test their tap density, compaction density, and specific surface area. After fabricating cathode sheets, the discharge specific capacity and capacity retention rate at different rates were tested. The results are shown in Table 2.
[0079] Table 2 Performance parameters of lithium manganese iron phosphate
[0080]
[0081] The results show that the lithium iron phosphate cathode material prepared using the manganese iron phosphate precursor provided by this invention has significant advantages in terms of specific capacity, rate performance, cycle performance, and electrode material processing performance.
Claims
1. A method of preparing a manganese iron phosphate precursor, characterized by: The preparation method includes the following steps: (1) Preparation of electrolyte solution: Dissolve manganese source, iron source and phosphorus source in water and mix well to obtain electrolyte solution; (2) Electrodeposition reaction: The electrolyte solution is placed in the electroplating tank to react and obtain manganese iron phosphate; (3) Collect manganese iron phosphate, wash and dry to obtain manganese iron phosphate precursor; In step (1), the atomic molar ratio of manganese, iron and phosphorus in the electrolyte solution is x:(1-x):(1-5), where 0<x<1; The pH of the electrolyte solution in step (1) is ≤1; The reaction temperature in step (2) is 25-60℃, and the reaction current density is 500-3000 A / m. 2 .
2. The method of claim 1, wherein the method comprises: The manganese source is any one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; the iron source is any one of ferrous sulfate, ferrous chloride, and ferrous nitrate; and the phosphorus source is any one of phosphoric acid, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate, and trisodium phosphate. 3. The method of claim 1, wherein the method further comprises: The electroplating tank described in step (2) is equipped with a working electrode and a counter electrode. 4. The method of claim 3, wherein the method further comprises: The working electrode is any one of a titanium plate, a graphite plate, or a platinum plate; the counter electrode is any one of a stainless steel plate, a titanium plate, a graphite plate, or a platinum plate.
5. The method of claim 1, wherein the method further comprises: In step (3), the atomic molar ratio of manganese, iron and phosphorus in the manganese iron phosphate precursor is x:(1-x):1, where 0<x<1. 6. The method for preparing a manganese iron phosphate precursor according to claim 1, characterized in that: The washing method described in step (3) includes water washing and alcohol washing, each washing 2-5 times; the drying conditions are drying at 70-90℃ for 20-26 hours.
7. The application of the manganese iron phosphate precursor prepared by the method of any one of claims 1-6 in the preparation of lithium manganese iron phosphate cathode materials.