Method for synthesizing high-purity battery-grade manganese acetate by using manganese sheet and acetic acid

Abstract

The invention relates to the technical field of manganese acetate synthesis, in particular to a method for synthesizing high-purity battery-grade manganese acetate by using a manganese sheet and acetic acid, which comprises the following steps: step 1, adding an acetic acid aqueous solution and the manganese sheet into a reactor for reaction; 2, separating the reaction liquid through a separation tower, and collecting an acetic acid-containing mixture extracted from the tower bottom; step 3, evaporating, cooling and crystallizing the acetic acid-containing mixture separated in the step 2 to obtain a manganese acetate crude product; step 4, adding the manganese acetate crude product obtained in the step 3 into a first purification tank; 5, after the reaction in the step 4 is finished, filtering the reaction liquid in the first purification tank, and conveying the filtered reaction liquid to a second purification tank; according to the method for synthesizing the high-purity battery-grade manganese acetate, the manganese sheets and the acetic acid are adopted as main raw materials, the main raw materials are low in price and easy to obtain, the preparation process is simple, few wastes are generated, and the obtained manganese acetate is high in purity.

Description

Technical Field

[0001] The invention relates to the technical field of manganese acetate synthesis, and in particular to a method for synthesizing high-purity battery-grade manganese acetate by using manganese sheets and acetic acid. Background Art

[0002] Manganese acetate, also known as manganese acetate, has the molecular formula: Mn(CH3COO)2, light red transparent monoclinic crystal, melting point 80°C, easily soluble in water and organic solvents such as acetic acid. It is not only used as a high-temperature oxidation catalyst for p-xylene, but also as a dyeing mordant, a drying agent for coatings and paints, etc.

[0003] In the field of new energy vehicles, manganese acetate also has wide application potential. The battery system of new energy vehicles is one of its most critical components, and manganese acetate can be used as an additive for battery positive electrode materials to improve battery life and energy density.

[0004] At present, the traditional preparation methods of manganese acetate are mainly metal manganese method and manganese sulfate method. The metal manganese method is also called electrolytic manganese method, which is to mix metal manganese and acetic acid and heat them to react, and then adjust the pH value, distill, concentrate and crystallize to obtain the finished manganese acetate. The manganese sulfate method uses manganese sulfate as raw material, reacts with soda ash to generate solid manganese carbonate, and then evaporates and crystallizes with acetic acid to obtain the finished manganese acetate. The traditional process products have high impurity content and cannot meet the use in the field of new energy vehicles.

[0005] Therefore, we proposed a method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid.

[0007] A method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid comprises the following steps: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4, adding the crude manganese acetate obtained in step 3 to a first purification tank, adding water to dissolve, and then adding manganese flakes to the first purification tank to carry out a replacement reaction; Step 5: After the reaction in step 4 is completed, the reaction liquid in the first purification tank is filtered and then transported to the second purification tank, hydrogen peroxide is added to the second purification tank, and after sufficient reaction, evaporation and cooling are performed to crystallize to obtain a crystalline product; Step 6: dissolve the crystallized product in step 5 with anhydrous ethanol, filter, evaporate the filtrate, cool and crystallize to obtain high-purity battery-grade manganese acetate.

[0008] Preferably, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 20% to 38%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 15 to 30:1, the reaction temperature is controlled at 40 to 60° C., and the reaction pressure is 0.01 to 0.1 MPa.

[0009] Preferably, in step 2, the separation tower is a distillation tower, and before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 75-80, the reboiler temperature in the distillation tower is 108-112°C, the top pressure is 0.7 bar, and the pressure drop of the whole tower is 0.1 bar. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0010] Preferably, the extractant is one of adiponitrile, N-methylacetamide and N-vinylacetamide.

[0011] Preferably, the method further comprises an extractant recovery tower. In step 3, during the evaporation cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 186-193° C., the tower top pressure is 0.6 bar, and the whole tower pressure drop is 0.1 bar. After separation, acetic acid is extracted from the tower top and the extractant is extracted from the tower bottom.

[0012] Preferably, in step 4, the mass ratio of water to crude manganese acetate is 4-10:1, and the mass ratio of manganese flakes to crude manganese acetate is 0.1-0.5:1.

[0013] Preferably, in step 4, during the replacement reaction, the reaction solution is extracted every 2 to 10 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0014] Preferably, in step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.03-0.1:1.

[0015] Preferably, in step 2, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 35-50, and the position of the feed plate of the distillation tower is 20-25.

[0016] Preferably, in step 3, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 12 to 20, and the position of the feed plate of the distillation tower is 3 to 8.

[0017] The beneficial effects of the present invention are: 1. The method for synthesizing high-purity battery-grade manganese acetate proposed by the present invention uses manganese flakes and acetic acid as main raw materials. The main raw materials are cheap and easily available, the preparation process is simple, and less waste is generated. The obtained manganese acetate has high purity.

[0018] 2. The method for synthesizing high-purity battery-grade manganese acetate proposed by the present invention comprises the following steps: adding manganese flakes into the first purification tank to carry out a replacement reaction, thereby replacing lead ions whose activity is lower than that of manganese; and then adding hydrogen peroxide into the second purification tank, so that the hydrogen peroxide oxidizes the ferrous ions to generate ferric acetate. Finally, ferric acetate is insoluble in ethanol, while manganese acetate is soluble in ethanol, thereby achieving purification of manganese acetate and obtaining high-purity battery-grade manganese acetate.

[0019] 3. The method for synthesizing high-purity battery-grade manganese acetate proposed in the present invention adds an extractant before separating acetic acid and water in the reaction solution, thereby reducing the difficulty of separating water and acetic acid, and separates the extractant from acetic acid through a recovery tower. The separated acetic acid and extractant can be recycled, thereby improving the utilization rate of raw materials and reducing the emission of pollutants.

[0020] 4. The method for synthesizing high-purity battery-grade manganese acetate proposed by the present invention comprises evaporating and cooling the mixture containing acetic acid separated in step 2 to obtain a crude manganese acetate, and separating acetic acid from the crude manganese acetate to avoid the reaction of acetic acid with manganese flakes (and impurities in the manganese flakes) during the subsequent replacement reaction, thereby reducing the introduction of impurities in the subsequent steps. DETAILED DESCRIPTION

[0021] The present invention will be further explained below in conjunction with specific embodiments.

[0022] In the following embodiments, the experimental methods or test methods, unless otherwise specified, are conventional methods; reagents and materials, unless otherwise specified, are obtained from conventional commercial channels or prepared by conventional methods, wherein: manganese flakes are 99.7% electrolytic manganese flakes purchased from Suzhou Tamuchuan Rare Metal Products Co., Ltd., and acetic acid is purchased from Jinan Zesheng Chemical Co., Ltd.

[0023] A method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid comprises the following steps: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4, adding the crude manganese acetate obtained in step 3 to a first purification tank, adding water to dissolve, and then adding manganese flakes to the first purification tank to carry out a replacement reaction; Step 5: After the reaction in step 4 is completed, the reaction liquid in the first purification tank is filtered and then transported to the second purification tank, hydrogen peroxide is added to the second purification tank, and after sufficient reaction, evaporation and cooling are performed to crystallize to obtain a crystalline product; Step 6: dissolve the crystallized product in step 5 with anhydrous ethanol, filter, evaporate the filtrate, cool and crystallize to obtain high-purity battery-grade manganese acetate.

[0024] In Example 1, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 20%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 15:1, the reaction temperature is controlled at 40° C., and the reaction pressure is 0.01 MPa.

[0025] In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 75, the reboiler temperature in the distillation tower is 108°C, the top pressure is 0.7 bar, the pressure drop of the whole tower is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 35, and the position of the feed plate of the distillation tower is 20. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0026] The extractant is adiponitrile.

[0027] The method further comprises an extractant recovery tower. In step 3, during the evaporation, cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 186-193° C., the tower top pressure is 0.6 bar, the whole tower pressure drop is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 12, and the position of the feed plate of the distillation tower is 3. After the separation is completed, acetic acid is extracted from the top of the tower and the extractant is extracted from the bottom of the tower.

[0028] In step 4, the mass ratio of water to the crude manganese acetate is 4:1, and the mass ratio of manganese flakes to the crude manganese acetate is 0.1:1.

[0029] In step 4, during the replacement reaction, the reaction solution is extracted every 2 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0030] In step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.03:1.

[0031] In Example 1, the purity of manganese acetate is 99.97%.

[0032] In Example 2, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 38%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 30:1, the reaction temperature is controlled at 60° C., and the reaction pressure is 0.1 MPa.

[0033] In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 80, the reboiler temperature in the distillation tower is 112°C, the top pressure is 0.7 bar, the pressure drop of the whole tower is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 50, and the position of the feed plate of the distillation tower is 25. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0034] The extractant is N-methylacetamide.

[0035] The method further comprises an extractant recovery tower. In step 3, during the evaporation, cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 186-193° C., the tower top pressure is 0.6 bar, the whole tower pressure drop is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 20, and the position of the feed plate of the distillation tower is 8. After the separation is completed, acetic acid is extracted from the top of the tower and the extractant is extracted from the bottom of the tower.

[0036] In step 4, the mass ratio of water to crude manganese acetate is 10:1, and the mass ratio of manganese flakes to crude manganese acetate is 0.5:1.

[0037] In step 4, during the replacement reaction, the reaction solution is extracted every 10 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0038] In step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.1:1.

[0039] In Example 2, the purity of manganese acetate is 99.98%.

[0040] In Example 3, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 30%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 20:1, the reaction temperature is controlled at 50° C., and the reaction pressure is 0.05 MPa.

[0041] In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 77, the reboiler temperature in the distillation tower is 109° C., the top pressure is 0.7 bar, the pressure drop of the whole tower is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 40, and the position of the feed plate of the distillation tower is 22. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0042] The extractant is N-vinyl acetamide.

[0043] The method further comprises an extractant recovery tower. In step 3, during the evaporation, cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 189° C., the tower top pressure is 0.6 bar, the whole tower pressure drop is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 18, and the position of the feed plate of the distillation tower is 5. After the separation is completed, acetic acid is extracted from the top of the tower and the extractant is extracted from the bottom of the tower.

[0044] In step 4, the mass ratio of water to crude manganese acetate is 6:1, and the mass ratio of manganese flakes to crude manganese acetate is 0.4:1.

[0045] In step 4, during the replacement reaction, the reaction solution is extracted every 5 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0046] In step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.06:1.

[0047] In Example 3, the purity of manganese acetate is 99.98%.

[0048] In Example 4, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 30%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 20:1, the reaction temperature is controlled at 50° C., and the reaction pressure is 0.05 MPa.

[0049] In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 77, the reboiler temperature in the distillation tower is 109° C., the top pressure is 0.7 bar, the pressure drop of the whole tower is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 40, and the position of the feed plate of the distillation tower is 22. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0050] The extractant is N-vinyl acetamide.

[0051] The method further comprises an extractant recovery tower. In step 3, during the evaporation, cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 189° C., the tower top pressure is 0.6 bar, the whole tower pressure drop is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 18, and the position of the feed plate of the distillation tower is 5. After the separation is completed, acetic acid is extracted from the top of the tower and the extractant is extracted from the bottom of the tower.

[0052] In step 4, the mass ratio of water to crude manganese acetate is 10:1, and the mass ratio of manganese flakes to crude manganese acetate is 0.5:1.

[0053] In step 4, during the replacement reaction, the reaction solution is extracted every 5 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0054] In step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.1:1.

[0055] In Example 4, the purity of manganese acetate is 99.97%.

[0056] In Example 5, in step 1, the mass fraction of the solute in the acetic acid aqueous solution is 30%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 20:1, the reaction temperature is controlled at 50° C., and the reaction pressure is 0.05 MPa.

[0057] In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 77, the reboiler temperature in the distillation tower is 109° C., the top pressure is 0.7 bar, the pressure drop of the whole tower is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 40, and the position of the feed plate of the distillation tower is 22. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

[0058] The extractant is N-vinyl acetamide.

[0059] The method further comprises an extractant recovery tower. In step 3, during the evaporation, cooling and crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 189° C., the tower top pressure is 0.6 bar, the whole tower pressure drop is 0.1 bar, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 18, and the position of the feed plate of the distillation tower is 5. After the separation is completed, acetic acid is extracted from the top of the tower and the extractant is extracted from the bottom of the tower.

[0060] In step 4, the mass ratio of water to the crude manganese acetate is 4:1, and the mass ratio of manganese flakes to the crude manganese acetate is 0.1:1.

[0061] In step 4, during the replacement reaction, the reaction solution is extracted every 5 minutes and the conductivity is measured. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

[0062] In step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.03:1.

[0063] In Example 5, the purity of manganese acetate is 99.98%.

[0064] In Comparative Example 1, a method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid comprises the following steps: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4, dissolving the crude manganese acetate in a second purification tank, adding hydrogen peroxide into the second purification tank, and after sufficient reaction, performing evaporation and cooling crystallization to obtain a crystalline product; Step 5: dissolving the crystallized product in step 4 with anhydrous ethanol, filtering, evaporating the filtrate, cooling and crystallizing to obtain high-purity battery-grade manganese acetate.

[0065] In step 4, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.06:1.

[0066] The rest is the same as Example 3.

[0067] In Comparative Example 1, the purity of manganese acetate was 99.91%.

[0068] In Comparative Example 2, a method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid comprises the following steps: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4, adding the crude manganese acetate obtained in step 3 to a first purification tank, adding water to dissolve, and then adding manganese flakes to the first purification tank to carry out a replacement reaction; Step 5: After the reaction in step 4 is completed, the reaction liquid in the first purification tank is filtered and then transported to the second purification tank for evaporation, cooling and crystallization to obtain a crystalline product; Step 6: dissolve the crystallized product in step 5 with anhydrous ethanol, filter, evaporate the filtrate, cool and crystallize to obtain high-purity battery-grade manganese acetate.

[0069] The rest is the same as Example 3.

[0070] In Comparative Example 2, the purity of manganese acetate was 99.72%.

[0071] In Comparative Example 3, a method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid comprises the following steps: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4: dissolve the crude manganese acetate in step 2 with anhydrous ethanol, filter, evaporate the filtrate, cool and crystallize to obtain high-purity battery-grade manganese acetate.

[0072] The rest is the same as Example 3.

[0073] In Comparative Example 3, the purity of manganese acetate was 99.64%.

[0074] In Examples 1-5, the purity of the obtained manganese acetate is stable and at a relatively high purity of greater than or equal to 99.97%, which meets the use requirements in the field of new energy vehicles; in Comparative Examples 1-3, the corresponding impurity removal step is lacking, and the purity is significantly reduced, especially in Comparative Example 3, the purity is only 99.64%.

[0075] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid, characterized in that: The following steps are involved: Step 1, adding acetic acid aqueous solution and manganese flakes into a reactor for reaction, performing solid-liquid separation after the reaction is completed, and conveying the reaction liquid to the liquid inlet of the separation tower; Step 2, separating the reaction liquid through a separation tower, separating the water in the reaction liquid, and collecting the mixture containing acetic acid extracted from the bottom of the tower; Step 3, evaporating and cooling the mixture containing acetic acid separated in step 2 and crystallizing it to obtain a crude manganese acetate; Step 4, adding the crude manganese acetate obtained in step 3 to a first purification tank, adding water to dissolve, and then adding manganese flakes to the first purification tank to carry out a replacement reaction; Step 5: After the reaction in step 4 is completed, the reaction liquid in the first purification tank is filtered and then transported to the second purification tank, hydrogen peroxide is added to the second purification tank, and after sufficient reaction, evaporation and cooling are performed to crystallize to obtain a crystalline product; Step 6: dissolve the crystallized product in step 5 with anhydrous ethanol, filter, evaporate the filtrate, cool and crystallize to obtain high-purity battery-grade manganese acetate.

2. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 1, characterized in that: In the step 1, the mass fraction of the solute in the acetic acid aqueous solution is 20% to 38%, the mass ratio of the acetic acid aqueous solution to the manganese flakes is 15 to 30:1, the reaction temperature is controlled at 40 to 60° C., and the reaction pressure is 0.01 to 0.1 MPa.

3. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 1, characterized in that: In step 2, the separation tower is a distillation tower. Before the reaction liquid enters the separation tower, an extractant is added to mix with the reaction liquid, and then the mixture is transported to the distillation tower. The reflux ratio of the distillation tower is 75-80, the reboiler temperature in the distillation tower is 108-112° C., the top pressure is 0.7 bar, and the pressure drop of the whole tower is 0.1 bar. After the separation is completed, water is extracted from the top of the tower, and the mixture containing acetic acid is extracted from the bottom of the tower.

4. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 3, characterized in that: The extractant is one of adiponitrile, N-methylacetamide and N-vinylacetamide.

5. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 4, characterized in that: The step 3 also includes an extractant recovery tower. In the step 3, during the evaporation cooling crystallization process, the gas phase is condensed and recovered, and the condensed and recovered coolant is transported to the extractant recovery tower to separate acetic acid from the extractant. The reflux ratio of the extractant recovery tower is 3, the reboiler temperature in the distillation tower is 186-193° C., the tower top pressure is 0.6 bar, and the whole tower pressure drop is 0.1 bar. After the separation is completed, acetic acid is extracted from the tower top and the extractant is extracted from the tower bottom.

6. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 1, characterized in that: In the step 4, the mass ratio of water to the crude manganese acetate is 4-10:1, and the mass ratio of manganese flakes to the crude manganese acetate is 0.1-0.5:

1.

7. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 1, characterized in that: In step 4, during the replacement reaction, the reaction solution is extracted every 2 to 10 minutes to measure the conductivity. When the conductivity change rate of the reaction solution between the first and the last two times is less than 0.3%, the reaction is completed.

8. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 1, characterized in that: In the step 5, the mass ratio of hydrogen peroxide to crude manganese acetate is 0.03-0.1:

1.

9. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 3, characterized in that: In the step 2, the reboiler is a kettle reboiler, the number of plates of the distillation tower is 35-50, and the position of the feed plate of the distillation tower is 20-25.

10. The method for synthesizing high-purity battery-grade manganese acetate using manganese flakes and acetic acid according to claim 5, characterized in that: In the step 3, the reboiler is a kettle reboiler, the number of plates of the recovery tower is 12 to 20, and the position of the feed plate of the distillation tower is 3 to 8.