Manganese ammonium phosphate as well as preparation method and application thereof

Abstract

The invention discloses ammonium manganese phosphate as well as a preparation method and application thereof, and relates to the technical field of lithium ion battery material preparation. The preparation method of the ammonium manganese phosphate comprises the following steps: preparing an ammonium dihydrogen phosphate solution, continuously stirring, heating, continuously introducing inert gas, adding a pH regulator at a volume flow rate of 15-25mL / min until the pH reaches 8.8-9.2, adding an antioxidant, and continuously adding the pH regulator until the pH reaches 9.6-10; and adding a manganese sulfate solution into the solution, continuously stirring until the product is thoroughly aged, and carrying out solid-liquid separation to obtain the ammonium manganese phosphate. According to the method, ammonium dihydrogen phosphate is adopted as a phosphorus source, and the high-purity ammonium manganese phosphate crystal meeting the requirements can be obtained through one-step reaction by optimizing process reaction condition parameters. Meanwhile, the content of impurity S can be greatly reduced, and the purity of the ammonium manganese phosphate is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery material preparation, and more specifically, to ammonium manganese phosphate and a preparation method and application thereof. Background Art

[0002] As a phosphate, ammonium manganese phosphate is not only widely used in fertilizers, catalysts, and flame retardants, but more importantly, it is used as a precursor for lithium iron manganese phosphate to prepare lithium iron manganese phosphate battery materials. If it is used to prepare lithium iron manganese phosphate battery materials, its purity and other aspects must meet the requirements of battery-grade raw materials. Therefore, improving product purity is a major difficulty currently faced by the industry.

[0003] Industrially produced ammonium manganese phosphate is mainly synthesized by coprecipitation. The manganese sources with wide sources and low costs are mainly manganese sulfate and manganese carbonate. However, manganese carbonate has poor water solubility and is not suitable for coprecipitation synthesis. Therefore, manganese sulfate is currently used as a manganese source in the industry to prepare ammonium manganese phosphate. However, when manganese sulfate is used as a manganese source, S impurities are inevitably introduced. Excessive S impurities will seriously affect the performance of the prepared manganese iron phosphate lithium battery material. At the same time, Mn 2+ Oxidation to Mn 3 + Improper control of the ratio of Mn to P will result in too many raw material components that have not reacted completely, which will also lead to a decrease in product purity.

[0004] Patent CN115231544A proposes a method for preparing ammonium manganese phosphate and a positive electrode material for a lithium-ion battery, wherein the manganese sulfate solution, the phosphorus source solution and the ammonium source solution are mixed, aged, and then solid-liquid separated to obtain ammonium manganese phosphate; the antioxidant solution includes at least one of a citric acid solution, an ascorbic acid solution, a hydrazine hydrate solution and hydrogen peroxide. The preparation method has a short reaction cycle, high production efficiency, a yield of 96.8%, and a purity of 98.0%; however, the method fails to effectively reduce the impurity S content in the ammonium manganese phosphate, and is not conducive to controlling the ratio of Mn to P. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects and shortcomings of low purity of ammonium manganese phosphate prepared in the prior art and to provide a method for preparing ammonium manganese phosphate.

[0006] Another object of the present invention is to provide a high-purity ammonium manganese phosphate.

[0007] Another object of the present invention is to provide an application of ammonium manganese phosphate prepared by a method for preparing ammonium manganese phosphate in preparing positive electrode materials for lithium ion batteries.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention provides a method for preparing ammonium manganese phosphate, comprising the following steps:

[0010] S1, preparing a diammonium phosphate solution with a molar concentration of 1-3 mol / L and continuously stirring, heating and continuously introducing an inert gas, adding a pH adjuster at a volume flow rate of 10-32 mL / min until the pH reaches 8.8-9.5, adding an antioxidant and continuing to add the pH adjuster until the pH reaches 9.6-10;

[0011] S2, adding manganese sulfate solution to the solution obtained in step S1, continuously stirring until the product is thoroughly aged, and separating the solid and liquid to obtain ammonium manganese phosphate.

[0012] The present invention uses ammonium dihydrogen phosphate as a phosphorus source, and optimizes the process reaction condition parameters to achieve a one-step reaction to obtain high-purity ammonium manganese phosphate crystals that meet the requirements. 3- NH4 + After the pH of the system reaches a certain level, the antioxidant is added and the antioxidant is fully dispersed. Then manganese sulfate is added to make Mn 2+ and PO4 3- NH4 + Fully react and inhibit Mn under the action of antioxidants 2+ Oxidation can also significantly reduce the content of impurity S and greatly improve the purity of ammonium manganese phosphate.

[0013] The inventors have found that the solubility of sulfur and its compounds under different pH conditions is different. By adjusting the pH, the dissolution and precipitation of sulfur can be controlled, thereby reducing the content of impurity sulfur. Therefore, the present invention adjusts the pH value of the diammonium phosphate solution and controls the addition rate of the pH regulator at the same time, effectively avoiding the phenomenon of local over-alkali, maintaining the uniformity and stability of the pH in the reaction system, and after adding the manganese sulfate solution for reaction, the impurity S content of the product can be greatly reduced, thereby improving the purity of ammonium manganese phosphate. The solubility of sulfur and its compounds under different pH conditions is different. By adjusting the pH, the dissolution and precipitation of sulfur can be controlled, thereby reducing the content of impurity sulfur.

[0014] Among them, it is necessary to pay attention to controlling the concentration of the diammonium phosphate solution and the addition rate of the pH adjuster. If the concentration of the diammonium phosphate solution is too high, the purity of the product will be affected; if the addition rate of the pH adjuster is too large, it will cause uneven crystallization of the product; but if the pH adjuster is added too slowly, the reaction system may be in a non-ideal pH state for a long time, thereby affecting the reaction rate and production efficiency. At the same time, insufficient addition of the pH adjuster will also affect the quality stability of the product.

[0015] In some embodiments, in step S1, the heating temperature is 45-60° C., preferably 48-52° C. The ammonium dihydrogen phosphate solution is heated before adjusting the pH. On the one hand, the dissolution of ammonium dihydrogen phosphate in water is an endothermic reaction, and heating helps its dissolution; on the other hand, heating in advance ensures that the temperature of the reaction process is controllable.

[0016] In some embodiments, the molar ratio of manganese element to diammonium phosphate in the manganese sulfate is (0.5-2):1.

[0017] In some embodiments, the inert gas is nitrogen.

[0018] In some embodiments, in step S1, the pH adjuster is an aqueous ammonia solution with a molar concentration of 8-18 mol / L.

[0019] In some embodiments, in step S1, the antioxidant includes any one or more of ascorbic acid, citric acid or acetic acid.

[0020] In some embodiments, the antioxidant is an ascorbic acid solution with a molar concentration of 0.1-0.2 mol / L and a volume flow rate of 8-16 mL / min.

[0021] In some embodiments, the molar ratio of the antioxidant to the manganese element in the manganese sulfate is (0.15-0.2): (16-22).

[0022] In some embodiments, in step S2, the molar concentration of the manganese sulfate solution is 2-4 mol / L, and the added volume flow rate is 45-55 mL / min.

[0023] In some embodiments, in step S2, the stirring time is 5-7 hours.

[0024] In some embodiments, in step S2, the solid-liquid separation includes: washing the product until the conductivity of the filtrate is ≤0.5 mS / cm, separating the filtrate from the precipitate, and drying the precipitate.

[0025] The invention protects ammonium manganese phosphate, which is prepared by the preparation method of ammonium manganese phosphate.

[0026] The invention protects the use of ammonium manganese phosphate prepared by a method for preparing ammonium manganese phosphate in preparing positive electrode materials for lithium ion batteries.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a method for preparing ammonium manganese phosphate, which uses ammonium dihydrogen phosphate as a phosphorus source and optimizes the process reaction condition parameters to achieve a one-step reaction to obtain high-purity ammonium manganese phosphate crystals that meet the requirements. The addition flow rate of a pH regulator is controlled and the pH of the system is optimized to make PO4 3- NH4 + After the pH of the system reaches a certain level, the antioxidant is added and the antioxidant is fully dispersed. Then manganese sulfate is added to make Mn 2+ and PO4 3- NH4 + Fully react and inhibit Mn under the action of antioxidants 2+ Oxidation can also significantly reduce the impurity S content, making the purity of ammonium manganese phosphate reach more than 98.9%. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0030] Example 1

[0031] A method for preparing ammonium manganese phosphate comprises the following steps:

[0032] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0033] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 21 mL / min until the pH reaches 9;

[0034] Continue to drop the ammonia solution at the same rate while slowly pumping in 1L of 0.17mol / L ascorbic acid solution at a rate of 12mL / min. When the pH value of the solution reaches 9.8, stop adding the ammonia solution.

[0035] (3) preparing 6.38 L of a manganese sulfate solution with a molar concentration of 3.01 mol / L, pumping it into the reactor at a rate of 48 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0036] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0037] Example 2

[0038] A method for preparing ammonium manganese phosphate comprises the following steps:

[0039] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0040] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 11 mL / min until the pH reaches 9;

[0041] Continue to drop the ammonia solution at the same rate while slowly pumping in 1L of 0.17mol / L ascorbic acid solution at a rate of 12mL / min. When the pH value of the solution reaches 9.8, stop adding the ammonia solution.

[0042] (3) preparing 6.38 L of a manganese carbonate solution with a molar concentration of 3.01 mol / L, pumping it into the reactor at a rate of 48 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0043] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0044] Example 3

[0045] A method for preparing ammonium manganese phosphate comprises the following steps:

[0046] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0047] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 31 mL / min until the pH reaches 9;

[0048] Continue to drop the ammonia solution at the same rate while slowly pumping in 1L of 0.17mol / L ascorbic acid solution at a rate of 12mL / min. When the pH value of the solution reaches 9.8, stop adding the ammonia solution.

[0049] (3) preparing 6.38 L of a manganese sulfate solution with a molar concentration of 3.01 mol / L, pumping it into the reactor at a rate of 48 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0050] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0051] Example 4

[0052] A method for preparing ammonium manganese phosphate comprises the following steps:

[0053] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0054] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 21 mL / min until the pH reaches 9.5;

[0055] Continue to drop the ammonia solution at the same rate while slowly pumping in 1L of 0.17mol / L ascorbic acid solution at a rate of 12mL / min. When the pH value of the solution reaches 10, stop adding the ammonia solution.

[0056] (3) preparing 6.38 L of a manganese sulfate solution with a molar concentration of 3.01 mol / L, pumping it into the reactor at a rate of 52 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0057] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0058] Comparative Example 1

[0059] A method for preparing ammonium manganese phosphate comprises the following steps:

[0060] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0061] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., instantly add 13.3 mol / L ammonia solution and 1 L of 0.17 mol / L ascorbic acid solution in the same amount as in Example 1, and then stir evenly;

[0062] (3) preparing 6.38 L of a manganese sulfate solution with a molar concentration of 3.01 mol / L, pumping it into the reactor at a rate of 48 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0063] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0064] Comparative Example 2

[0065] A method for preparing ammonium manganese phosphate comprises the following steps:

[0066] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 100 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0067] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 21 mL / min until the pH reaches 9.8, and then the addition of ammonia solution is stopped;

[0068] (3) preparing 6.38 L of a 3.01 mol / L manganese sulfate solution and 1 L of a 0.17 mol / L ascorbic acid solution, pumping the manganese sulfate solution into the reactor at a rate of 42 mL / min, and simultaneously slowly pumping the ascorbic acid solution into the reactor at a rate of 12 mL / min, and continuously stirring for 6 hours to allow the product to be thoroughly aged;

[0069] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0070] Comparative Example 3

[0071] A method for preparing ammonium manganese phosphate comprises the following steps:

[0072] (1) 10.8 L of ammonium dihydrogen phosphate solution with a molar concentration of 1.59 mol / L was prepared and added as a base liquid into a 50 L reactor. The reactor was stirred at 600 rpm, heated to 50° C., and nitrogen was continuously introduced;

[0073] (2) After the temperature of the bottom liquid in step (1) reaches 50° C., 13.3 mol / L ammonia solution is slowly pumped into the bottom liquid at a rate of 21 mL / min until the pH reaches 9.8, and then the addition of ammonia solution is stopped;

[0074] (3) preparing 6.38 L of a manganese sulfate solution with a molar concentration of 3.01 mol / L, pumping the manganese sulfate solution into the reactor at a rate of 42 mL / min, and continuously stirring for 6 hours to allow the product to age thoroughly;

[0075] (4) The product was washed with pure water until the conductivity of the filtrate was ≤0.5 mS / cm, the filtrate and the precipitate were completely separated by suction filtration, and the precipitate was transferred to a forced air drying oven at 110° C. and dried for 12 h to obtain ammonium manganese phosphate precursor powder.

[0076] Comparative Example 4

[0077] A method for preparing ammonium manganese phosphate, which is different from Example 1 in that: in step (1), the molar concentration of the diammonium phosphate solution is 3.43 mol / L and the volume is 5.0 L.

[0078] Comparative Example 5

[0079] A method for preparing ammonium manganese phosphate, which is different from Example 1 in that: in step (2), 13.3 mol / L ammonia solution is slowly pumped into the base liquid at a speed of 5 mL / min.

[0080] Comparative Example 6

[0081] A method for preparing ammonium manganese phosphate, which is different from Example 1 in that: in step (2), 13.3 mol / L ammonia solution is slowly pumped into the base liquid at a speed of 40 mL / min.

[0082] Performance Testing

[0083] The products of Examples 1-4 and Comparative Examples 1-2 were taken to detect the content of impurity S therein. The results are shown in Table 1.

[0084] Table 1

[0085] S content (ppm) Yield purity Example 1 602 98.9％ 99.5％ Example 2 719 99.6％ 99.1％ Example 3 1637 96.3％ 99.0％ Example 4 1803 98.0％ 98.9％ Comparative Example 1 4401 93.1％ 94.2％ Comparative Example 2 4037 93.6％ 94.8％ Comparative Example 3 5062 92.3％ 93.1％ Comparative Example 4 4681 97.2％ 96.5％ Comparative Example 5 2749 96.8％ 97.2％ Comparative Example 6 4278 95.4％ 96.3％

[0086] The S content of the ammonium manganese phosphate prepared by the invention is below 1803 ppm, the yield is above 96.3%, and the purity is above 98.9%.

[0087] Compared with Example 1, after the ammonia solution was quickly added in Comparative Example 1, the product crystallized unevenly, and its yield and purity were reduced.

[0088] Compared with Example 1, in Comparative Example 2, manganese sulfate solution and ascorbic acid solution were added to diammonium phosphate solution at the same time, the dispersibility of ascorbic acid was poor, some metal ions were oxidized, and the yield and purity were reduced. In Comparative Example 3, no ascorbic acid solution was added, and the impurity S content was too high, and the yield and purity were significantly reduced.

[0089] Compared with Example 1, the concentration of the ammonium dihydrogen phosphate solution in Comparative Example 3 was too high, and PO4 3- NH4 + The product is fully dissociated and evenly distributed in the solution, and its yield and purity decrease.

[0090] Compared with Example 1, when the addition rate of ammonia water in Comparative Examples 5-6 is too large or too small, the yield and purity thereof decrease.

[0091] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing ammonium manganese phosphate, characterized in that: The following steps are involved: S1, preparing a diammonium phosphate solution with a molar concentration of 1-3 mol / L and continuously stirring, heating and continuously introducing an inert gas, adding a pH adjuster at a volume flow rate of 10-32 mL / min until the pH reaches 8.8-9.5, adding an antioxidant and continuing to add the pH adjuster until the pH reaches 9.6-10; S2, adding manganese sulfate solution to the solution obtained in step S1, continuously stirring until the product is thoroughly aged, and separating the solid and liquid to obtain ammonium manganese phosphate.

2. The method for preparing ammonium manganese phosphate according to claim 1, wherein The molar ratio of manganese element to diammonium phosphate in the manganese sulfate is (0.5-2):

1.

3. The method for preparing ammonium manganese phosphate according to claim 1, characterized in that: In step S1, the pH adjuster is an aqueous ammonia solution with a molar concentration of 8-18 mol / L.

4. The method for preparing ammonium manganese phosphate according to claim 1, characterized in that: In step S1, the antioxidant includes any one or two or more of ascorbic acid, citric acid or acetic acid.

5. The method for preparing ammonium manganese phosphate according to claim 1 or 4, characterized in that: The antioxidant is an ascorbic acid solution with a molar concentration of 0.1-0.2 mol / L and a volume flow rate of 8-16 mL / min.

6. The method for preparing ammonium manganese phosphate according to claim 1, characterized in that: In step S1, the heating temperature is 45-60°C.

7. The method for preparing ammonium manganese phosphate according to claim 1, characterized in that: In step S2, the molar concentration of the manganese sulfate solution is 2-4 mol / L, and the added volume flow rate is 45-55 mL / min.

8. The method for preparing ammonium manganese phosphate according to claim 1, characterized in that: In step S2, the stirring time is 5-7 hours.

9. A manganese ammonium phosphate, characterized in that: The ammonium manganese phosphate is prepared by the preparation method of any one of claims 1 to 8.

10. Use of ammonium manganese phosphate prepared by the method for preparing ammonium manganese phosphate according to any one of claims 1 to 8 in preparing positive electrode materials for lithium ion batteries.