Ferrous manganese phosphate, its preparation method and application

Abstract

This invention provides a method for preparing ferrous manganese phosphate, comprising mixing an iron source, a manganese source, and phosphoric acid, adding a phosphorus source, controlling the pH value to 3.0-4.0, and preparing a mixed solution; then adding an ammonia solution A to a reaction vessel, and simultaneously adding the mixed solution A and ammonia solution B dropwise under an inert gas atmosphere, controlling the pH value throughout the reaction process to (7.5-8.0) ± 0.1, and co-precipitating to obtain ferrous manganese phosphate. The ferrous manganese phosphate prepared by this invention has uniform Mn, Fe, and P content and stable ratio.

Description

Technical Field

[0001] This invention belongs to the field of battery cathode material manufacturing technology, and particularly relates to a method for preparing ferromanganese phosphate, ferromanganese phosphate obtained by the method, and the application of ferromanganese phosphate in lithium iron phosphate batteries. Background Technology

[0002] Numerous reports have been published on the preparation methods of lithium iron manganese phosphate (LMP) battery materials and precursors. Currently, the main methods for preparing LMP include high-temperature solid-state reaction, sol-gel reaction, and co-precipitation. Among these, the high-temperature solid-state reaction is widely used and suitable for industrial production. However, it is difficult to control the nucleation rate and ion diffusion rate of the generated phase in solid-state reactions. Therefore, the synthesized LMP products have poor consistency, uneven particle morphology, and wide particle size distribution. Furthermore, the entire high-temperature solid-state reaction process generates significant waste gas pollution, mainly NH3 and CO2. To overcome these shortcomings, the co-precipitation method for preparing LMP precursors has become a key research focus. Summary of the Invention

[0003] The purpose of this invention is to provide a solution to the problem of unstable proportions of various components in current ferrous manganese phosphate.

[0004] To achieve the above objectives, the present invention provides a method for preparing ferrous manganese phosphate, comprising the following steps:

[0005] S1. Mix the iron source, manganese source, and phosphoric acid, add the phosphorus source, and control the pH to 3.0-4.0 to prepare a mixed solution;

[0006] S2. Add ammonia solution A into the reaction vessel, and under an inert gas atmosphere, simultaneously add the mixed solution and ammonia solution B, controlling the pH of the entire reaction process to (7.5-8.0) ± 0.1, and co-precipitate to prepare ferrous manganese phosphate.

[0007] Optionally, in step S1, the iron source includes at least one of ferrous sulfate, hydrated ferrous sulfate, ferrous nitrate, and ferrous chloride.

[0008] Optionally, in step S1, the phosphorus source includes at least one of phosphoric acid, sodium phosphate, potassium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0009] Optionally, in step S1, the manganese source includes at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate.

[0010] Optionally, step S1 further includes adding an antioxidant, which includes ascorbic acid, and the added antioxidant is 1% of the mass fraction of the iron source.

[0011] Optionally, in step S1, the molar ratio of the added manganese source to the iron source (Mn / Fe) is 8:2-2:8, and the molar ratio of the sum of the added manganese source and the iron source to phosphorus is 1.41-1.43. Preferably, the molar ratio of the manganese source to the iron source (Mn / Fe) is 7:3-3:7. Further preferably, the molar ratio of the manganese source to the iron source (Mn / Fe) is 6:4-4:6.

[0012] Optionally, in step S2, the mass percentage of the ammonia solution A is 16-20%, and the mass percentage of the ammonia solution B is 8-10%.

[0013] Optionally, in step S2, when adding the mixed solution and ammonia B, the pH of the system is maintained at 5-8.

[0014] Optionally, in step S2, the ferrous manganese phosphate is filtered, washed, dried, flash-evaporated, ground, and mixed. The washing, flash-evaporation, sintering, mixing, and packaging are all carried out in an air atmosphere.

[0015] In another aspect, the present invention provides ferrous manganese phosphate, which is prepared by the above-described preparation method.

[0016] In another aspect, the present invention provides the application of ferrous manganese phosphate prepared by the above-described method in lithium iron manganese phosphate batteries.

[0017] This invention involves adding phosphoric acid to a solution prepared from iron and manganese sources to lower the pH value, thereby reducing the probability of ferrous ion oxidation. An antioxidant is also added to prevent the mixed solution from being easily oxidized during preparation and addition.

[0018] In this invention, ammonium phosphate is added to the mixed solution. After the ammonium phosphate dissolves completely, it can both provide a phosphorus source and utilize the coordination effect of ammonium. NH 4+ The coordination of Mn with ammonia water was achieved by simultaneously adding the precursors, mimicking the method used for ternary precursors. 2+ ,Fe 2+ Regarding the issue of uniform precipitation of phosphate, Mn 2+ Fe 2+ In the phosphate system, the precipitation rate is of the same order of magnitude, which meets the requirements of co-precipitation from the perspective of chemical reaction. Finally, the contents of Mn, Fe and P in ferrous manganese phosphate are uniform and the ratio is stable.

[0019] In this invention, ammonia solution A is first added to the reactor, and the pH of ammonia solution A is adjusted to 7.5-8.0. Under a nitrogen atmosphere, the mixed solution and alkali (ammonia solution B) are simultaneously added dropwise using a peristaltic pump. By fixing the flow rate of the mixed solution at 239 ml / min and controlling the flow rate of ammonia solution at 80 ml / mins, the pH is controlled at 7.5±0.1 throughout the feeding process.

[0020] The manganese ferrous phosphate prepared by this invention initially produces hollow spheres in the synthesis reaction. As the feeding time increases, the loose packing and compaction of the solid spheres also increase. Attached Figure Description

[0021] To make the technical problems solved by this invention, the technical means adopted, and the technical effects achieved clearer, specific embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, it should be noted that the drawings described below are merely drawings of exemplary embodiments of this invention. Those skilled in the art can obtain drawings of other embodiments based on these drawings without any creative effort.

[0022] Figure 1 This is a flowchart of a method for preparing ferrous manganese phosphate.

[0023] Figure 2A -SEM image of ferrous manganese phosphate in Example 1.

[0024] Figure 3A -SEM image of ferrous manganese phosphate in Example 3.

[0025] Figure 4A -SEM image of ferrous manganese phosphate in Example 4.

[0026] Figure 5A -E EDS elemental distribution diagram of ferrous manganese phosphate in Example 1.

[0027] Figure 6A - EDS line scan of ferrous manganese phosphate in Example 1.

[0028] Figure 7A -SEM image of iron manganese phosphate in Comparative Example 1. Detailed Implementation

[0029] Exemplary embodiments of the invention will now be described more fully with reference to the accompanying drawings. While these exemplary embodiments can be implemented in various specific ways, they should not be construed as limiting the invention to the embodiments set forth herein. Rather, these exemplary embodiments are provided to make the content of the invention more complete and to facilitate a full communication of the inventive concept to those skilled in the art. Structures, performance, effects, or other features described in a particular embodiment, while consistent with the inventive concept, may be combined in any suitable manner with one or more other embodiments.

[0030] In the description of specific embodiments, detailed descriptions of structures, performance, effects, or other features are provided to enable those skilled in the art to fully understand the embodiments. However, this does not preclude those skilled in the art from implementing the present invention with technical solutions that do not contain the aforementioned structures, performance, effects, or other features under specific circumstances.

[0031] Although the steps in this invention are arranged by reference numerals, this is not intended to limit the order of the steps. Unless the order of the steps is explicitly stated or the execution of a step requires other steps as a basis, the relative order of the steps can be adjusted. It is understood that the term "and / or" as used herein refers to and covers any and all possible combinations of one or more of the associated listed items.

[0032] Unless otherwise specified, all chemical reagents and materials used in this invention were purchased through commercial channels.

[0033] A method for preparing ferrous manganese phosphate includes the following steps:

[0034] Mix the iron source, manganese source, and phosphoric acid, where the ratio of the sum of the molar amounts of Mn and Fe to the molar amount of P is 1.41 - 1.43. The molar ratio of Mn / Fe is 8:2 - 2:8. Then add an antioxidant, which is 1% of the mass fraction of the iron source. Add the phosphorus source again, and control the pH value to be 3.0 - 4.0 throughout the process to make a mixed solution; Dilute commercially available ammonia water with pure water to a mass percentage of 16 - 20% at pH 7.5 to make ammonia water solution B. Put ammonia water solution A with a mass percentage of 16% (diluted 1:1 with pure water) into the reaction kettle, introduce nitrogen, and the reaction temperature is 25 - 40°C. As the temperature rises, the sphericity becomes denser and the primary particles are smaller. At the same time, dropwise add the mixed solution (flow rate 239 ml / min) and ammonia water B (flow rate 80 ml / mins). The entire reaction system maintains a pH of 5 - 8. The higher the pH value, the smaller the primary and secondary particles. However, if pH > 9.0, it is very difficult to make spherical particles even under nitrogen introduction. The feeding times are 0.5, 2, 4, and 6 h respectively. As the feeding time extends, the loose bulk density of the solid spheres also increases. After feeding, age for 1 hour to prepare iron manganese phosphite by coprecipitation. The chemical formula of the obtained iron manganese phosphite is (MnxFe1x)3(PO4)2·yH2O, where 0 < x < 1 and 0 ≤ y ≤ 8. Filter and wash the iron manganese phosphite to separate and purify it, washing away impurities, and the main impurities include (NH4 4+ , SO4 2- ). Dry and flash evaporate, with an inlet air temperature of 220 ± 5°C and an outlet air temperature of 100 ± 5°C. Sinter in a rotary kiln at 610 - 620°C for 3 - 4 h. After sintering the iron manganese phosphite, grind it mechanically, mix it in a mixer, and package it with a packaging machine to obtain the finished product.

[0035] Example 1

[0036] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate heptahydrate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia water solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 30℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added to the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted based on the pH meter signal feedback, maintaining the reaction at pH 7.50±0.1 throughout the feeding process. The feeding time was 4 hours. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1 hour. After the reaction, the mixture was filtered using a filter press, washed with water (cake:water = 1:4) 7 times, and the filter cake was flash-dried. The flash drying inlet air temperature was 220±5℃ and the outlet air temperature was 100±5℃. The sintering was carried out in a rotary kiln at 610-620℃ for 3-4 hours. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate. Figure 2A As can be seen from -D, the prepared secondary particles of manganese ferrous phosphate are spherical and solid. Figure 5A -E is the EDS elemental distribution diagram of ferrous manganese phosphate, which shows that Mn, Fe, and P are homogeneous.

[0037] Figure 6A -C is the EDS line scan of ferromanganese phosphate. The line scan shows that Mn, Fe and P are evenly distributed in ferromanganese phosphate, and the CP surface is flat and the elements are uniform.

[0038] Example 2:

[0039] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate heptahydrate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 30℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added into the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted by the pH meter signal feedback, so that the reaction was maintained at pH 7.50±0.1 throughout the feeding process. The feeding time was 2 hours. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1 hour. After the reaction was completed, the mixture was filtered by a filter press and washed with water (cake:water = 1:4) 7 times. The filter cake was flash dried with an inlet air temperature of 220±5℃ and an outlet air temperature of 100±5℃. The mixture was then sintered in a rotary kiln at 610-620℃ for 3-4 hours. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate.

[0040] Example 3:

[0041] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate heptahydrate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 30℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added into the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted by the pH meter signal feedback, so that the reaction was maintained at pH 7.50±0.1 throughout the feeding process. The feeding time was 0.5h. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1h. After the reaction was completed, the mixture was filtered by a filter press and washed with water (cake:water = 1:4) 7 times. The filter cake was flash dried with an inlet air temperature of 220±5℃ and an outlet air temperature of 100±5℃. The mixture was then sintered in a rotary kiln at 610-620℃ for 3-4h. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate. Figure 3A —C shows that the feeding time is 0.5h, and the prepared manganese ferrous phosphate is a hollow sphere.

[0042] Example 4:

[0043] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate heptahydrate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 30℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added into the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted by the pH meter signal feedback, so that the reaction was maintained at pH 7.50±0.1 throughout the feeding process. The feeding time was 6 hours. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1 hour. After the reaction was completed, the mixture was filtered by a filter press and washed with water (cake:water = 1:4) 7 times. The filter cake was flash dried with an inlet air temperature of 220±5℃ and an outlet air temperature of 100±5℃. The sintering was carried out in a rotary kiln at 610-620℃ for 3-4 hours. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate. Figure 4A —D shows that the feeding time is 6 hours, and the prepared manganese ferrous phosphate is a solid ball.

[0044] Example 5:

[0045] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia water solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 35℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added into the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted by the pH meter signal feedback, so that the reaction was maintained at pH 7.50±0.1 throughout the feeding process. The feeding time was 4 hours. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1 hour. After the reaction was completed, the mixture was filtered by a filter press and washed with water (cake:water = 1:4) 7 times. The filter cake was flash dried with an inlet air temperature of 220±5℃ and an outlet air temperature of 100±5℃. The mixture was then sintered in a rotary kiln at 610-620℃ for 3-4 hours. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate.

[0046] Example 6:

[0047] Add 20,000.00g of pure water, 500.00g of phosphoric acid (85%), 5,000g of ferrous sulfate heptahydrate (20.12%), 4,578.938g of manganese sulfate (32.42%), and 3,213.15g of monoammonium phosphate (26.81%) to mixing tank 1 to form a mixed solution; dilute 13,050g of ammonia water (16%) with pure water at a 1:1 ratio in mixing tank 2 to form ammonia water solution B. Nitrogen gas was introduced into the reactor, the reaction temperature was 40℃, and 15000g of ammonia solution A (pure water adjusted to pH 7.50 with ammonia) was added as the base solution. The mixed solution and ammonia solution B were added into the reactor using peristaltic pumps #1 and #2, respectively. The flow rate of peristaltic pump #2 was automatically adjusted by the pH meter signal feedback, so that the reaction was maintained at pH 7.50±0.1 throughout the feeding process. The feeding time was 4 hours. The mixed solution and ammonia solution B were added dropwise simultaneously. Nitrogen gas was continued to be introduced into the reactor, and the reaction was aged for 1 hour. After the reaction was completed, the mixture was filtered by a filter press and washed with water (cake:water = 1:4) 7 times. The filter cake was flash dried with an inlet air temperature of 220±5℃ and an outlet air temperature of 100±5℃. The sintering was carried out in a rotary kiln at 610-620℃ for 3-4 hours. After sintering, the material was mechanically ground and then fed into a mixer and packaging machine to obtain the finished product, ferrous manganese phosphate.

[0048] Example 7:

[0049] The difference between this embodiment and Example 1 is that the reaction temperature is 25°C, while the other steps and reaction conditions are exactly the same.

[0050] Example 8:

[0051] The difference between this embodiment and Example 1 is that the reaction is maintained at pH 7.0 ± 0.1 throughout the feeding process, while the other steps and reaction conditions are exactly the same.

[0052] Example 9:

[0053] The difference between this embodiment and Example 1 is that the reaction is maintained at pH 8.0 ± 0.1 throughout the feeding process, while the other steps and reaction conditions are exactly the same.

[0054] Example 10:

[0055] The difference between this embodiment and Example 1 is that the sum of the molar amounts of manganese sulfate and ferrous sulfate and the molar amount of ammonium dihydrogen phosphate is 1.41, and the molar ratio of manganese sulfate to ferrous sulfate is 6:4. The other steps and reaction conditions are exactly the same.

[0056] Example 11:

[0057] The difference between this embodiment and Example 1 is that the mass fraction of ascorbic acid and ferrous sulfate powder is 1%, while the other steps and reaction conditions are exactly the same.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the pH was adjusted to 8.5 during the reaction. As a result, the raw materials were oxidized, and manganese and iron ions could not be completely precipitated. The high ion loss rate of the mother liquor led to a low M / P ratio in the finished ferrous manganese phosphate, M / P = 1.435, which does not meet the requirement that the M / P ratio of the finished ferrous manganese phosphate should be in the range of 1.450-1.465. Figure 7A As can be seen from the SEM images of -E, the prepared manganese ferrous phosphate cannot form spherical shapes.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0062] In the above embodiments, the endpoints and any values ​​of the disclosed ranges are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0063] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0065] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for producing ferromanganous phosphate, characterized by, Includes the following steps: S1. Mix the iron source, manganese source, and phosphoric acid, add ammonium dihydrogen phosphate or diammonium hydrogen phosphate, and control the pH value to 3.0-4.0 to prepare a mixed solution; the mixture also includes adding an antioxidant, which includes ascorbic acid, wherein the molar ratio of the added manganese source to the iron source (Mn / Fe) is 8:2-2:8, and the molar ratio of the sum of the added manganese source and iron source to phosphorus is 1.41-1.43; S2. Add ammonia solution A to the reaction vessel. The pH of ammonia solution A is 7.5-8.

0. Under an inert gas atmosphere, simultaneously add the mixed solution and ammonia solution B. Control the flow rate of the mixed solution to 239 ml / min and the flow rate of ammonia solution B to 80 ml / min. Control the pH to 7.5±0.1 throughout the feeding process. Co-precipitate, filter, wash with water, dry, flash evaporate, sinter, grind, and mix to obtain solid spherical ferromanganese phosphate.

2. The method of claim 1, wherein the manganese ferrous phosphate is prepared by the steps of: In step S1, the iron source includes at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride. ​ 3. The method for preparing ferrous manganese phosphate according to claim 1, characterized in that, In step S1, the manganese source includes at least one of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate.

4. The method for preparing ferrous manganese phosphate according to claim 1, characterized in that, In step S2, the mass percentage of the ammonia solution A is 16-20%, and the mass percentage of the ammonia solution B is 8-10%.

5. A type of manganese ferric phosphate, characterized in that: The ferrous manganese phosphate is prepared by the preparation method described in any one of claims 1-4.

6. The application of ferrous manganese phosphate prepared by the method of any one of claims 1-4 in lithium iron manganese phosphate batteries.

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