Ferric manganese phosphate and its preparation method, cathode material, secondary battery

Abstract

This invention provides a method for preparing ferromanganese phosphate. Using manganese, iron (containing ferric phosphate and / or ferric phosphate dihydrate), and phosphorus as raw materials, a seed induction solution is prepared. The solution is heated to generate NH4Fe(HPO4)2. This new biophase reduces the (Mn+Fe) / P ratio of the product during subsequent recrystallization of ferromanganese phosphate. After aging and recrystallization with ammonium ferromanganese phosphate slurry, a suitable (Mn+Fe) / P ratio of ferromanganese phosphate can be obtained through post-treatment. The preparation method of this invention can control the amount of new phase generated by controlling the amount of ferric phosphate and ferric phosphate dihydrate in the raw materials, thereby controlling the (Mn+Fe) / P ratio in the final product, ferromanganese phosphate. This preparation method is simple to operate, easy to implement, has good process stability, requires no additional surfactant, and offers high controllability of the (Mn+Fe) / P ratio in the product, which can be adjusted according to requirements. The prepared ferromanganese phosphate product has a controllable (Mn+Fe) / P ratio and low impurity content.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology. Specifically, this invention relates to a metal-to-phosphorus ratio adjustable manganese iron phosphate, its preparation method, cathode material, and secondary battery. Background Technology

[0002] Currently, the cathode materials for lithium-ion batteries that have been put into practical use can be divided into three categories: lithium metal oxides, spinel structure materials, and polyanionic structure materials. Lithium metal oxides are mainly lithium cobalt oxide and ternary materials, which have the advantages of high energy density and high conductivity, but their safety and cycle performance are generally poor. Spinel structure materials are mainly lithium manganese oxide, which have the advantages of low price and easy synthesis, but their energy density is relatively low and their cycle performance is generally poor. Polyanionic structure compounds are represented by lithium iron phosphate materials, which have excellent safety performance, good overcharge resistance and cycle stability, but their energy density is relatively low.

[0003] Lithium iron phosphate is easy to synthesize, has low cost, and relatively high conductivity, so its commercialization has been quite successful. Among the same group of compounds, lithium manganese phosphate has a high discharge platform, but its reactivity is low. Generally, lithium iron phosphate and lithium manganese phosphate are combined to form lithium manganese iron phosphate (LMFP). The advantages of the composite cathode material are: (1) it can form a single solid solution, which can improve the energy density of lithium iron phosphate batteries; (2) Mn 2+ The ionic radius is slightly larger than that of Fe. 2+ It can form lattice defects, expand the lithium ion transport channels, increase ionic conductivity, and improve the rate performance of the material; (3) Fe 3+ -O-Mn 2+ Interionic interactions can reduce Mn 3+ / Mn 2+ The redox reaction energy level improves the low capacity and poor rate performance of lithium manganese phosphate. Future lithium manganese iron phosphate may become an upgraded version of lithium iron phosphate, replacing high-end lithium iron phosphate and some medium-nickel ternary cathode materials in end-use applications. Ferric manganese phosphate is a precursor material for the synthesis of lithium manganese iron phosphate and largely determines the latter's performance. Currently, there is limited research on precursor materials for lithium manganese iron phosphate in China, and there are no relevant standards in the industry regarding the phase and composition of precursors.

[0004] Chinese invention patent CN105244497A discloses a method for preparing iron-manganese phosphate intermediates and lithium iron-manganese phosphate / carbon composite materials. The method involves adding manganese nitrate, iron nitrate, and selectively added doped metal M salt to a beaker containing water, stirring to dissolve them, and preparing an aqueous solution A of the metal salt with a molar ratio of Fe:Fe+Mn+M=0.1~0.6, which is then set aside. (2) Phosphoric acid and ethanol are added sequentially to a three-necked flask to form solution B. The solution is then refluxed and heated to 80~90℃ with stirring, and set aside. (3) The aqueous solution A of the metal salt is added to a three-necked flask containing solution B. After solution A is fully fed, solution A and solution B are reacted at the temperature described in step 2) for 2~7 hours. After the reaction is complete, the solution is unloaded, washed, and dried to finally obtain the iron-manganese phosphate intermediate. This method does not provide detailed descriptions of the phases and main components of the synthesized intermediate, and the addition of ethanol is costly.

[0005] Chinese invention patent CN109250698A discloses a high tap density lithium manganese iron phosphate cathode material, its preparation method, and its application. The preparation method involves slowly adding iron salt solution, manganese salt solution, phosphorus source solution, a mixed solution of surfactant and complexing agent, and precipitant solution to a three-necked flask, stirring and reacting at 70-90℃ for 3-5 hours to obtain a slurry of ferromanganese iron phosphate dihydrate; (2) filtering the slurry of ferromanganese iron phosphate dihydrate obtained by the reaction into a ferromanganese iron phosphate dihydrate cake using a filter press, then drying it completely under vacuum at 90-100℃, and then ball milling it for 1-2 hours. The (Mn+Fe) / P ratio of ferromanganese iron phosphate dihydrate synthesized by this method cannot be adjusted. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing ferromanganese phosphate, wherein the ratio of metal to phosphorus in the synthesized ferromanganese phosphate is adjustable.

[0007] To achieve the above objectives, the present invention proposes the following solution:

[0008] This invention provides a method for preparing ferric manganese phosphate, comprising:

[0009] (1) Using manganese source, iron source, phosphorus source, ammonia water, acid and water as raw materials, adjust the pH value to 0 to 4 to prepare a seed crystal induction solution. The iron source is any one of iron phosphate and iron phosphate dihydrate mixed with a soluble iron source.

[0010] (2) Heat the seed crystal induction solution to 60-99°C, add manganese iron ammonium phosphate slurry, and keep it warm for aging;

[0011] (3) The aged slurry is subjected to solid-liquid separation, drying and calcination to obtain manganese iron phosphate.

[0012] Preferably, in step (1), the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate.

[0013] Preferably, in step (1), the soluble iron source is one or more of the following: ferrous sulfate (a byproduct of titanium dioxide), industrial-grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, and ferrous acetate.

[0014] Preferably, in step (1), the phosphorus source is a soluble phosphorus source; the soluble phosphorus source is selected from one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0015] Preferably, in step (1), the acid is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0016] Preferably, in step (1), the pH value is adjusted to 0 to 3, and more preferably, the pH value is adjusted to 0 to 2.

[0017] Preferably, in step (2), the temperature of the heat preservation and aging process is 60-99°C, and the time of the heat preservation and aging process is 2-4 hours.

[0018] Preferably, in step (3), the calcination temperature is 300–600°C.

[0019] Preferably, the preparation method of the manganese ferric ammonium phosphate slurry includes: mixing manganese ferric ammonium phosphate raw material with water and then pulping it to obtain manganese ferric ammonium phosphate slurry.

[0020] Preferably, the solid content of the manganese ferric ammonium phosphate slurry is 150-250 g / L.

[0021] Preferably, the ratio of the total molar amount of Mn and Fe to the molar amount of P in the manganese iron ammonium phosphate slurry is 1 to 1.05:1.

[0022] Preferably, in step (1), the amount of manganese iron ammonium phosphate that can be theoretically prepared from the manganese source, iron source, phosphorus source and ammonia water in the seed induction solution is 5 to 90% of the amount of manganese iron ammonium phosphate in the manganese iron ammonium phosphate slurry.

[0023] Preferably, in step (1), the ratio of the total molar amount of Mn and Fe to the molar amount of P in the seed induction solution is less than 1.

[0024] Preferably, in step (1), the total amount of ferric phosphate and ferric phosphate dihydrate is 25-75% of the total molar amount of the iron source.

[0025] As a general inventive concept, the present invention provides a manganese iron phosphate, which is prepared by the aforementioned preparation method.

[0026] Preferably, the secondary particle size D50 of the ferromanganese phosphate is 1–30 μm, and the tap density is 0.6–1.5 g / cm³. 3 Specific surface area is 1-10 m² 2 / g, molar ratio n (Mn+Fe) / n P It ranges from 0.95 to 1.0.

[0027] As a general inventive concept, the present invention also provides a positive electrode active material, which can be lithium manganese iron phosphate or sodium manganese iron phosphate, prepared using the aforementioned manganese iron phosphate as a raw material.

[0028] As a general inventive concept, the present invention also provides a secondary battery, including the aforementioned positive electrode active material.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the preparation method of ferromanganese phosphate of the present invention, manganese source, iron source containing ferric phosphate and / or ferric phosphate dihydrate, phosphorus source, etc. are used as raw materials to prepare a seed induction solution. Heating the seed induction solution generates NH4Fe(HPO4)2 in the system. This new biophase can reduce the (Mn+Fe) / P ratio of the product in the system during the subsequent recrystallization of ferromanganese phosphate. Adding ammonium ferromanganese phosphate slurry for aging and recrystallization, followed by post-treatment, yields ferromanganese phosphate with a suitable metal-to-phosphorus ratio. The preparation method of the present invention can control the amount of NH4Fe(HPO4)2 generated by controlling the amount of ferric phosphate and / or ferric phosphate dihydrate in the raw materials, thereby controlling the (Mn+Fe) / P ratio in the final product, ferromanganese phosphate. This preparation method is simple to operate, easy to implement, requires no additional surfactant, has high controllability of the (Mn+Fe) / P ratio in the product and can be adjusted according to requirements, and the process has good stability. The prepared ferromanganese phosphate product has a controllable (Mn+Fe) / P ratio and low impurity content. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The image shows the XRD pattern of the substance precipitated after the induction solution in step S5 of Example 1 is heated to 90°C.

[0033] Figure 2This is a morphological image of the substance precipitated after the induction solution in step S5 of Example 1 is heated to 90°C.

[0034] Figure 3 The image shows the XRD pattern of the sample dried in step S5 of Example 1.

[0035] Figure 4 This is a morphological image of the sample after drying in step S5 of Example 1.

[0036] Figure 5 This is a morphology diagram of the manganese iron phosphate obtained in Example 1.

[0037] Figure 6 The image shows the XRD pattern of the sample dried in step S5 of Comparative Example 1.

[0038] Figure 7 This is a morphological image of the sample dried in step S5 of Comparative Example 1.

[0039] Figure 8 The image shows the XRD pattern of the dried sample from step S5 of Comparative Example 2.

[0040] Figure 9 This is a SEM image of the sample dried in step S5 of Comparative Example 2.

[0041] Figure 10 The image shows the XRD pattern of the dried sample from step S5 of Comparative Example 3.

[0042] Figure 11 The image shows the XRD pattern of the dried sample from step S5 of Example 2.

[0043] Figure 12 The image shows the XRD pattern of the dried sample from step S5 of Example 3.

[0044] Figure 13 The image shows the XRD pattern of the dried sample from step S5 of Example 4.

[0045] Figure 14 The image shows the XRD pattern of the dried sample from step S5 of Example 5.

[0046] Figure 15 The image shows the XRD pattern of the dried sample from step S5 of Example 6.

[0047] Figure 16 The image shows the XRD pattern of the dried sample from step S5 of Example 7.

[0048] Figure 17 The image shows the XRD pattern of the dried sample from step S5 of Example 8.

[0049] Figure 18 The image shows the XRD pattern of the dried sample from step S5 of Example 9.

[0050] Figure 19 The image shows the XRD pattern of the dried sample from step S5 of Example 10. Detailed Implementation

[0051] This invention provides a method for preparing ferric manganese phosphate, comprising:

[0052] (1) Using manganese source, iron source, phosphorus source, ammonia water, acid and water as raw materials, adjust the pH value to 0 to 4 to prepare a seed crystal induction solution. The iron source is any one of iron phosphate and iron phosphate dihydrate mixed with a soluble iron source.

[0053] (2) Heat the seed crystal induction solution to 60-99°C, add manganese iron ammonium phosphate slurry, and keep it warm for aging;

[0054] (3) The aged slurry is subjected to solid-liquid separation, drying, and calcination to obtain manganese iron phosphate.

[0055] The (Mn+Fe) / P molar ratio of ferromanganese phosphate prepared by precipitation is generally higher than 1. When using this type of ferromanganese phosphate as a precursor to prepare lithium iron phosphate, the molar content of P is relatively low. Therefore, when using this type of ferromanganese phosphate as a precursor for sintering to prepare lithium iron phosphate, a certain amount of P needs to be added to balance the (Mn+Fe) / P ratio after sintering. Generally, the final (Mn+Fe) / P molar ratio is required to be 0.95–1.00 to obtain high-performance Li(Mn,Fe)PO4 or Na(Mn,Fe)PO4. However, the additional P addition has efficiency issues, is prone to errors, and is difficult to precisely control the amount of P added in the raw material based on the (Mn+Fe) / P ratio in the finished product, which can adversely affect the stability of subsequent processes. At the same time, phosphorus supplementation increases the cost of subsequent processes. However, aging the precipitated manganese iron ammonium phosphate (NH4(Mn,Fe)PO4·H2O) directly leads to a phase change, generating red manganese phosphate (Mn,Fe)5(PO3(OH))2(PO4)2·4H2O and water-phosphorus iron ammonium phosphate (Fe,Mn)2(NH4OH)(PO4)2·2H2O. The molar ratio of (Mn+Fe) / P in red manganese phosphate (Mn,Fe)5(PO3(OH))2(PO4)2·4H2O is between 1.24 and 1.26. After the formation of this phase, the molar ratio of (Mn+Fe) / P after aging will increase from the original 1-1.05 to 1.05-1.10, which requires the addition of more phosphorus.

[0056] To address the aforementioned technical problems, this application, after extensive research, proposes the following solution. In this solution, ferric phosphate and / or ferric phosphate dihydrate are introduced as a partial iron source during the preparation of the seed crystal induction solution. The induction solution is then heated, causing the divalent iron source in the induction solution to oxidize, resulting in the following chemical reaction:

[0057]

[0058]

[0059] During the heating process of the induction solution, the ferric ammonium hydrogen phosphate phase NH4(Fe,Mn)(HPO4)2 precipitates, with a (Mn+Fe) / P ratio between 0.4 and 0.6. In the final aged product, the introduction of NH4(Fe,Mn)(HPO4)2 significantly reduces the overall (Mn+Fe) / P molar ratio. This ratio can be easily adjusted by changing the amount of ferric phosphate and / or ferric phosphate dihydrate in the iron source. Furthermore, the (Mn+Fe) / P ratio can be more precisely controlled by parameters such as the molar equivalent of ferric manganese phosphate added to the entire induction solution, the pH value of the seed induction solution, and the heating temperature of the seed induction solution, demonstrating good controllability.

[0060] Furthermore, in this technical solution, the synthesized manganese ferric ammonium phosphate is dissolved and recrystallized through an aging process. The impurities such as Na, K, S, Ca, Mg, Cu, Cr, Al, Co, Ni, and Zn after dissolution can be significantly reduced, thus effectively reducing the impurity content in the product.

[0061] In some preferred embodiments, in step (2), the total amount of ferric phosphate and ferric phosphate dihydrate in the iron source is 25-75% of the total molar amount of the iron source.

[0062] The aging process is carried out under stirring conditions, and the stirring speed can be the conventional stirring speed used in the field for aging.

[0063] In some preferred embodiments, in step (2), the seed crystal induction solution is heated to 60-95°C, and manganese iron ammonium phosphate slurry is added for heat preservation and aging.

[0064] In some preferred embodiments, in step (2), the temperature of the heat preservation and aging process is 60 to 99°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.

[0065] In some preferred embodiments, in step (2), the heat preservation and aging time is 2 to 4 hours, for example, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc.

[0066] In some preferred embodiments, in step (2), the amount of manganese iron ammonium phosphate that can be theoretically prepared from the manganese source, iron source, phosphorus source and ammonia water in the induction liquid is 5 to 90% of the amount of manganese iron ammonium phosphate in the manganese iron ammonium phosphate slurry, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc.

[0067] In some embodiments, in step (1), the ratio of the total molar amount of Mn and Fe to the molar amount of P in the seed induction solution is less than 1, and is more preferably 0.2 to 0.95, such as 0.95, 0.9, 0.85, 0.7, 0.65, 0.60, 0.55, 0.50, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, etc.

[0068] In some preferred embodiments, in step (3), the calcination temperature is 300 to 600°C, for example, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, etc.

[0069] In some preferred embodiments, the preparation method of the manganese ferric ammonium phosphate slurry includes: mixing manganese ferric ammonium phosphate raw material with water and then pulping it to obtain manganese ferric ammonium phosphate slurry. The pulping can be performed using equipment known in the art; for example, the pulping equipment can be an aging tank.

[0070] In some preferred embodiments, the solid content of the manganese ferric ammonium phosphate slurry is 150-250 g / L, such as 150 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, etc.

[0071] In some preferred embodiments, the ratio of the total molar amount of Mn and Fe to the molar amount of P in the manganese ferric ammonium phosphate slurry is 1 to 1.05:1, for example, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, etc.

[0072] In some preferred embodiments, the molar ratio n of metal to phosphorus in the manganese ferric ammonium phosphate slurry is... (Mn+Fe) / n P The molar ratio of manganese to iron (n) Mn / n Fe The ratio is the same as that in the solution prepared in step (1). Using the same ratio helps to reduce the difficulty of process control.

[0073] In some embodiments, the manganese source is a soluble manganese source, and more preferably, the soluble manganese source is selected from one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate.

[0074] In some embodiments, the soluble iron source is selected from one or more of the following: ferrous sulfate (a byproduct of titanium dioxide), industrial-grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, and ferrous acetate.

[0075] In some embodiments, the phosphorus source is a soluble phosphorus source, and more preferably, the soluble phosphorus source is selected from one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0076] In some embodiments, the drying is oven drying; the oven drying temperature is 100-150°C.

[0077] In this invention, the raw material for ferric ammonium manganese phosphate can be a conventional ferric ammonium manganese phosphate product or a newly prepared ferric ammonium manganese phosphate product, preferably a newly prepared ferric ammonium manganese phosphate product. If a newly prepared ferric ammonium manganese phosphate product is used, the preparation method can be an existing method for preparing ferric ammonium manganese phosphate, such as a continuous method or a batch method.

[0078] When preparing ferric ammonium manganese phosphate using a batch method, in some embodiments, the preparation method of the ferric manganese phosphate raw material includes:

[0079] S1. Dissolve the manganese and iron sources in deionized water, add an antioxidant, and filter to obtain solution A; dissolve the phosphorus source in deionized water, filter to obtain solution B; prepare pH adjustment solution C;

[0080] S2. Under a non-oxidizing atmosphere, solutions A, B and C are introduced concurrently into the bottom liquid of the reaction vessel to carry out the reaction. During the reaction, the pH of the system is maintained at 3 to 7.

[0081] S3. The obtained reaction slurry is subjected to solid-liquid separation, washing and drying to obtain manganese iron phosphate raw material.

[0082] In some embodiments, the reaction temperature in step S2 is 40–60°C.

[0083] In some embodiments, in step S2, the stirring speed of the reaction is 200 to 1200 rpm.

[0084] In some embodiments, the pH adjusting agent solution C is an ammonia solution; the concentration of the pH adjusting agent solution is preferably 5-10 mol / L.

[0085] In some embodiments, the total molar concentration of Mn and Fe in solution A is 0.2–2 mol / L; the molar ratio of Mn to Fe is 1–2:1.

[0086] In some embodiments, the manganese source is selected from one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate.

[0087] In some embodiments, the iron source is one or more of the following: ferrous sulfate (a byproduct of titanium dioxide), industrial-grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, and ferrous acetate.

[0088] In some embodiments, the concentration of the phosphorus source in solution B is 0.2~2 mol / L.

[0089] In some embodiments, the phosphorus source is selected from one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0090] In some embodiments, the amount of antioxidant is determined by adding 0.5 to 1.5 g to 1 L of solution.

[0091] In some embodiments, the antioxidant is selected from one or more of ascorbic acid, hydrazine hydrate, sodium sulfite, and sodium nitrite; when hydrazine hydrate, sodium sulfite, or sodium nitrite is selected as the antioxidant, an appropriate amount of acid is added to adjust the pH value.

[0092] In some embodiments, in step S2, the pH value of the bottom liquid of the reaction vessel is 3 to 7; the bottom liquid of the reaction vessel is obtained by adjusting the pH of pure water to 3 to 7; the reagent for adjusting the pH is selected from one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0093] In some embodiments, in step S2, the amount of the bottom liquid in the reactor can be the conventional amount used in the art, preferably 30-50% of the reactor volume.

[0094] In some embodiments, in step S2, the material is introduced until the slurry in the reactor occupies 70-90% of the reactor volume and the reaction is stopped.

[0095] In some embodiments, in step S2, the feed flow rate of solution A is controlled to be 50-500 ml / min.

[0096] In some embodiments, in step S2, the feed flow rate of solution B is added according to a molar ratio of (Mn+Fe) / P of 1 to 1.05:1 in the reaction system.

[0097] In some embodiments, in step S2, the flow rate of the non-oxidizing gas is controlled to be between 0.1 and 50 ml / min; the non-oxidizing gas is preferably nitrogen.

[0098] In a specific embodiment, ferromanganese phosphate is also provided, prepared using the aforementioned preparation method. The secondary particle size D50 of the ferromanganese phosphate is 1–30 μm, preferably 5–20 μm; the tap density is 0.6–1.5 g / cm³. 3 ; Specific surface area is 1-10 m² 2 / g, preferably 1-5m 2 / g; molar ratio n (Mn+Fe) / n P The value is 0.9 to 1.1, preferably 0.9 to 1.0, and more preferably 0.95 to 1.00, such as 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, etc.

[0099] In a specific embodiment, lithium manganese iron phosphate is also provided, which is prepared using the aforementioned iron manganese phosphate as a raw material.

[0100] In a specific embodiment, sodium manganese ferric phosphate is also provided, which is prepared using the aforementioned manganese ferric phosphate as a raw material.

[0101] In a specific embodiment, a secondary battery, such as a lithium-ion battery or a sodium-ion battery, is also provided, including a positive electrode active material, which is the aforementioned lithium manganese iron phosphate or sodium manganese iron phosphate.

[0102] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0103] In the following embodiments, the particle size distribution testing instrument is a Malvern 3000 particle size analyzer; the BET testing instrument is a specific surface area analyzer, model BSD-BET400, manufactured by Best Instrument Technology (Beijing) Co., Ltd.; and the tap density tester is a tap density meter, model BT-313, manufactured by Dandong Better Instrument Co., Ltd.

[0104] The Fe element content was tested using redox titration; the P element content was tested using the quinomolybdate gravimetric method.

[0105] Example 1

[0106] Step S1, preparation of manganese and iron source solutions:

[0107] Manganese sulfate and ferrous sulfate were dissolved in deionized water to prepare a 2 mol / L solution with a molar ratio of Mn to Fe of 6:4. 1 g of ascorbic acid was then added to 1 L of the solution, and the mixture was filtered to obtain solution A.

[0108] Step S2, preparation of phosphorus source solution:

[0109] Phosphoric acid was dissolved in deionized water to prepare a 2 mol / L solution, which was then filtered to obtain solution B.

[0110] Step S3, pH adjuster preparation:

[0111] Prepare an 8 mol / L ammonia solution, filter, and obtain an 8 mol / L solution C;

[0112] Step S4, Synthesis Reaction:

[0113] Add 30% deionized water to the synthesis reactor, heat to 60℃, stir at 800 rpm, and purge with nitrogen for 1 hour. Add sulfuric acid to adjust the pH of the solution in the synthesis reactor to 5.5±0.1. At the same time, inject solutions A and B into the synthesis reactor at a flow rate of 160 ml / min. Use solution C to maintain the pH of the synthesis reactor at 5.5±0.1 to allow for a full reaction until the volume of the slurry in the synthesis reactor reaches 80%. Separate the solid and liquid components to obtain a filter cake. At this point, (Mn+Fe) / P=1.040. Add water and the filter cake to a new reactor for a second pulping process, controlling the solid content of the second pulping to be 200 g / L.

[0114] Step S5, aging and dehydration:

[0115] In an aging reactor, a 20L seed crystal induction solution was prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added was determined according to the concentrations of 0.3 mol / L MnSO4·H2O, 0.1 mol / L FeSO4·7H2O, 0.1 mol / L FePO4·2H2O, 0.5 mol / L NH3·H2O, and 0.5 mol / L H3PO4. Finally, the pH of the solution was adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature was then raised to 90℃. During this process, a new phase precipitated. XRD analysis showed the following results: Figure 1 As shown, from Figure 1 It can be determined that the newly formed phase is NH4Fe(HPO4)2. Figure 2 To determine the morphology of this phase, the main component analysis revealed a (Mn+Fe) / P molar ratio of 0.504. Within 1 hour, 30 L of a 200 g / L manganese iron ammonium phosphate slurry was added to the seed crystal induction solution, and the mixture was aged at 90 °C for 3 hours. Solid-liquid separation was then performed to obtain a filter cake, which was dried at 150 °C. The morphology after drying is shown in the figure. Figure 3 The phase analysis results after drying are shown in the figure. Figure 4 The product phases include ① red phosphorus manganese ore, ② ammonium manganese phosphate (NH4MnPO4·H2O), and ③ ferric ammonium hydrogen phosphate (NH4Fe(HPO4)2). Dehydration and deammoniation are achieved by calcination at 400℃ to obtain ferric manganese phosphate. SEM images are shown below. Figure 5 As shown.

[0116] The obtained manganese ferric phosphate had a particle size D50 of 18.4 μm and a tap density of 1.25 g / cm³. 3 Its specific surface area is 1.2 m². 2 / g, and its (Mn+Fe) / P molar ratio was measured to be 0.975.

[0117] Comparative Example 1

[0118] The only difference between this comparative example and Example 1 is that, in step S5, ferrous sulfate is used instead of ferrous phosphate dihydrate.

[0119] Step S5 is as follows: In the aging reactor, 20L of seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added is determined according to the concentrations of 0.3mol / L MnSO4·H2O, 0.2mol / L FeSO4·7H2O, 0.5mol / L NH3·H2O, and 0.5mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is raised to 90℃, and 30L of manganese ferric ammonium phosphate slurry with a solid content of 200g / L is added to the seed crystal induction solution within 1 hour. The aging is continued at 90℃ for 3 hours. Solid-liquid separation is performed to obtain a filter cake, which is dried at 150℃. The morphology of the dried sample is shown in the figure. Figure 6 The phase analysis results are shown in Figure 7 The product phases include ① red phosphorus manganese ore (Mn5(PO3(OH))2(PO4)2·4H2O), ② hydrophosphorus iron ammonia ore (Fe2(NH4OH)(PO4)2·2H2O), and ③ ammonium manganese phosphate NH4MnPO4·H2O.

[0120] The obtained manganese ferric phosphate had a particle size D50 of 17.9 μm and a tap density of 1.3 g / cm³. 3 The specific surface area is 1.05 m². 2 / g, and its (Mn+Fe) / P molar ratio was measured to be 1.02.

[0121] Comparative Example 2

[0122] The difference between this comparative example and Example 1 is that, in step S5, the pH of the induction solution is 5.5.

[0123] Step S5 is as follows: In the aging kettle, 20L of seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added is determined according to the concentrations of 0.3mol / L MnSO4·H2O, 0.1mol / L FeSO4·7H2O, 0.1mol / L FePO4·2H2O, 0.5mol / L NH3·H2O, and 0.5mol / L H3PO4. Finally, the pH of the solution is adjusted to 5.5 with sulfuric acid to obtain the seed crystal induction solution. The temperature is raised to 90℃, and 30L of manganese ferric ammonium phosphate slurry with a solid content of 200g / L is added to the seed crystal induction solution within 1 hour. The solution is then aged at 90℃ for another 3 hours. Solid-liquid separation is performed to obtain a filter cake, which is then dried at 150℃. The morphology of the dried sample is shown in the figure below. Figure 8 As shown, the XRD pattern is as follows Figure 9 As shown, the phase analysis results are: ① red phosphorus manganese ore Mn5(PO3(OH))2(PO4)2·4H2O, ② water-phosphorus iron ammonia ore Fe2(NH4OH)(PO4)2·2H2O, ③ ammonium manganese phosphate NH4MnPO4·H2O.

[0124] The obtained manganese ferric phosphate had a particle size D50 of 15.6 μm and a tap density of 1.12 g / cm³. 3 Its specific surface area is 1.33 m². 2 / g, and its (Mn+Fe) / P ratio was measured to be 1.05.

[0125] Comparative Example 3

[0126] The difference between this comparative example and Example 1 is that in step S5, the induction liquid is heated and kept at a temperature of 30°C.

[0127] Step S5 is as follows: In the aging reactor, 20L of seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added is determined according to the concentrations of 0.3mol / L MnSO4·H2O, 0.1mol / L FeSO4·7H2O, 0.1mol / L FePO4·2H2O, 0.5mol / L NH3·H2O, and 0.5mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is raised to 50℃, and 30L of manganese ferric ammonium phosphate slurry with a solid content of 200g / L is added to the seed crystal induction solution within 1 hour. The solution is then aged at 90℃ for 3 hours. Solid-liquid separation is performed to obtain a filter cake, which is dried at 150℃. The XRD pattern of the dried sample is shown in the figure. Figure 10 As shown, the final phase analysis results are: ① red phosphorus manganese ore Mn5(PO3(OH))2(PO4)2·4H2O, ② hydrophosphorus iron ammonia ore Fe2(NH4OH)(PO4)2·2H2O, ③ ammonium manganese phosphate NH4MnPO4·H2O.

[0128] The obtained manganese ferric phosphate had a particle size D50 of 14.9 μm and a tap density of 1.32 g / cm³. 3 Its specific surface area is 1.46 m². 2 / g, and its (Mn+Fe) / P molar ratio was measured to be 1.045.

[0129] Example 2

[0130] The only difference between this embodiment and Embodiment 1 is that in step S5, the amount of FeSO4·7H2O added is determined according to a concentration of 0.14 mol / L, and the amount of FePO4·2H2O added is determined according to a concentration of 0.06 mol / L.

[0131] Step S5 specifically involves preparing a 20L seed crystal induction solution in an aging reactor using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added is determined according to the concentrations of 0.3 mol / L MnSO4·H2O, 0.14 mol / L FeSO4·7H2O, 0.06 mol / L FePO4·2H2O, 0.5 mol / L NH3·H2O, and 0.5 mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is then raised to 90℃. During this process, a new phase precipitates. XRD analysis shows the results as follows. Figure 1 As shown, from Figure 1 It can be determined that the newly formed phase is NH4Fe(HPO4)2. Figure 2 To determine the phase morphology, the main component of the phase was analyzed, revealing a (Mn+Fe) / P molar ratio of 0.504. Within 1 hour, 30 L of a 200 g / L manganese iron ammonium phosphate slurry was added to the seed crystal induction solution, and the mixture was aged at 90 °C for 3 hours. Solid-liquid separation was then performed to obtain a filter cake, which was dried at 150 °C. The XRD pattern of the sample obtained after drying in step S5 is shown below. Figure 11 As shown.

[0132] The obtained manganese ferric phosphate had a particle size D50 of 15.5 μm and a tap density of 1.35 g / cm³. 3 The specific surface area is 1.58 m². 2 / g, and its (Mn+Fe) / P molar ratio was measured to be 0.983.

[0133] Example 3

[0134] The only difference between this embodiment and Embodiment 1 is that in step S5, the amount of FeSO4·7H2O added is determined according to a concentration of 0.06 mol / L, and the amount of FePO4·2H2O added is determined according to a concentration of 0.14 mol / L.

[0135] Step S5 specifically involves preparing a 20L seed crystal induction solution in an aging reactor using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The amount of raw materials added is determined according to the concentrations of 0.3 mol / L MnSO4·H2O, 0.06 mol / L FeSO4·7H2O, 0.14 mol / L FePO4·2H2O, 0.5 mol / L NH3·H2O, and 0.5 mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is then raised to 90℃. During this process, a new phase precipitates. XRD analysis shows the results as follows. Figure 1 As shown, from Figure 1 It can be determined that the newly formed phase is NH4Fe(HPO4)2. Figure 2 To determine the phase morphology, the main component of the phase was analyzed, revealing a (Mn+Fe) / P molar ratio of 0.504. Within 1 hour, 30 L of a 200 g / L manganese iron ammonium phosphate slurry was added to the seed crystal induction solution, and the mixture was aged at 90 °C for 3 hours. Solid-liquid separation was then performed to obtain a filter cake, which was dried at 150 °C. The XRD pattern of the sample obtained after drying in step S5 is shown below. Figure 12 As shown.

[0136] The molar ratio of (Mn+Fe) / P in the obtained manganese iron phosphate sample was found to be 0.971.

[0137] Example 4

[0138] Step S1, preparation of manganese and iron source solutions:

[0139] Manganese sulfate and ferrous sulfate were dissolved in deionized water to prepare a 2 mol / L solution with a molar ratio of Mn to Fe of 6:4. 1 g of ascorbic acid was then added to 1 L of the solution, and the mixture was filtered to obtain solution A.

[0140] Step S2, preparation of phosphorus source solution:

[0141] Phosphoric acid was dissolved in deionized water to prepare a 2 mol / L solution, which was then filtered to obtain solution B.

[0142] Step S3, pH adjuster preparation:

[0143] Prepare an 8 mol / L ammonia solution, filter, and obtain an 8 mol / L solution C;

[0144] Step S4, Synthesis Reaction:

[0145] Add 30% deionized water to the synthesis reactor, heat to 60℃, stir at 800 rpm, and purge with nitrogen for 1 hour. Add sulfuric acid to adjust the pH of the solution in the synthesis reactor to 5.5±0.1. At the same time, inject solutions A and B into the synthesis reactor at a flow rate of 160 ml / min. Use solution C to maintain the pH of the synthesis reactor at 5.5±0.1 to allow for a full reaction until the volume of the slurry in the synthesis reactor reaches 80%. Separate the solid and liquid components to obtain a filter cake. At this point, (Mn+Fe) / P=1.040. Add water and the filter cake to a new reactor for a second pulping process, controlling the solid content of the second pulping to be 200 g / L.

[0146] Step S5, aging and dehydration:

[0147] In the aging reactor, 20L of seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The raw materials are added according to the following concentrations: 0.1mol / L MnSO4·H2O, 0.033mol / L FeSO4·7H2O, 0.033mol / L FePO4·2H2O, 0.166mol / L NH3·H2O, and 0.166mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is then raised to 90℃, during which a new phase will precipitate.

[0148] Within 1 hour, 30 L of manganese ferric ammonium phosphate slurry with a solid content of 200 g / L was added to the seed crystal induction solution. The mixture was then aged at 90 °C for 3 hours. Solid-liquid separation was performed to obtain a filter cake, which was dried at 150 °C. The XRD pattern of the dried sample is shown below. Figure 13 As shown, the phosphate was then calcined at 400℃ to dehydrate and deammonenze, yielding ferromanganese phosphate. The final ferromanganese phosphate had a (Mn+Fe) / P molar ratio of 0.988.

[0149] Example 5

[0150] Step S1, preparation of manganese and iron source solutions:

[0151] Manganese sulfate and ferrous sulfate were dissolved in deionized water to prepare a 2 mol / L solution with a molar ratio of Mn to Fe of 6:4. 1 g of ascorbic acid was then added to 1 L of the solution, and the mixture was filtered to obtain solution A.

[0152] Step S2, preparation of phosphorus source solution:

[0153] Phosphoric acid was dissolved in deionized water to prepare a 2 mol / L solution, which was then filtered to obtain solution B.

[0154] Step S3, pH adjuster preparation:

[0155] Prepare an 8 mol / L ammonia solution, filter, and obtain an 8 mol / L solution C;

[0156] Step S4, Synthesis Reaction:

[0157] Add 30% deionized water to the synthesis reactor, heat to 60℃, stir at 800 rpm, and purge with nitrogen for 1 hour. Add sulfuric acid to adjust the pH of the solution in the synthesis reactor to 5.5±0.1. At the same time, inject solutions A and B into the synthesis reactor at a flow rate of 160 ml / min. Use solution C to maintain the pH of the synthesis reactor at 5.5±0.1 to allow for a full reaction until the volume of the slurry in the synthesis reactor reaches 80%. Separate the solid and liquid components to obtain a filter cake. At this point, (Mn+Fe) / P=1.040. Add water and the filter cake to a new reactor for a second pulping process, controlling the solid content of the second pulping to be 200 g / L.

[0158] Step S5, aging and dehydration:

[0159] In the aging reactor, a 20L seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The raw materials are added according to the following concentrations: 0.58mol / L MnSO4·H2O, 0.19mol / L FeSO4·7H2O, 0.19mol / L FePO4·2H2O, 0.96mol / L NH3·H2O, and 0.96mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is then raised to 90℃, during which a new phase will precipitate.

[0160] Within 1 hour, 30 L of manganese ferric ammonium phosphate slurry with a solid content of 200 g / L was added to the seed crystal induction solution. The mixture was then aged at 90 °C for 3 hours. Solid-liquid separation was performed to obtain a filter cake, which was dried at 150 °C. The XRD pattern of the dried sample is shown below. Figure 14 As shown, the ferromanganese was then calcined at 400℃ to remove water and ammonia, yielding ferromanganese phosphate. The final ferromanganese phosphate had a (Mn+Fe) / P molar ratio of 0.969.

[0161] Example 6

[0162] Step S1, preparation of manganese and iron source solutions:

[0163] Manganese sulfate and ferrous sulfate were dissolved in deionized water to prepare a 2 mol / L solution with a molar ratio of Mn to Fe of 6:4. 1 g of ascorbic acid was then added to 1 L of the solution, and the mixture was filtered to obtain solution A.

[0164] Step S2, preparation of phosphorus source solution:

[0165] Phosphoric acid was dissolved in deionized water to prepare a 2 mol / L solution, which was then filtered to obtain solution B.

[0166] Step S3, pH adjuster preparation:

[0167] Prepare an 8 mol / L ammonia solution, filter, and obtain an 8 mol / L solution C;

[0168] Step S4, Synthesis Reaction:

[0169] Add 30% deionized water to the synthesis reactor, heat to 60℃, stir at 800 rpm, and purge with nitrogen for 1 hour. Add sulfuric acid to adjust the pH of the solution in the synthesis reactor to 5.5±0.1. At the same time, inject solutions A and B into the synthesis reactor at a flow rate of 160 ml / min. Use solution C to maintain the pH of the synthesis reactor at 5.5±0.1 to allow for a full reaction until the volume of the slurry in the synthesis reactor reaches 80%. Separate the solid and liquid components to obtain a filter cake. At this point, (Mn+Fe) / P=1.040. Add water and the filter cake to a new reactor for a second pulping process, controlling the solid content of the second pulping to be 200 g / L.

[0170] Step S5, aging and dehydration:

[0171] In the aging reactor, a 20L seed crystal induction solution is prepared using manganese sulfate, ferrous sulfate, ferric phosphate dihydrate, ammonia, and phosphoric acid as raw materials. The raw materials are added according to the following concentrations: 0.77mol / L MnSO4·H2O, 0.26mol / L FeSO4·7H2O, 0.26mol / L FePO4·2H2O, 1.29mol / L NH3·H2O, and 1.29mol / L H3PO4. Finally, the pH of the solution is adjusted to 1.0 with sulfuric acid to obtain the seed crystal induction solution. The temperature is then raised to 90℃, during which a new phase will precipitate.

[0172] Within 1 hour, 30 L of manganese ferric ammonium phosphate slurry with a solid content of 200 g / L was added to the seed crystal induction solution. The mixture was then aged at 90 °C for 3 hours. Solid-liquid separation was performed to obtain a filter cake, which was dried at 150 °C. The XRD pattern of the dried sample is shown below. Figure 15 As shown, the ferromanganese was then calcined at 400℃ to remove water and ammonia, yielding ferromanganese phosphate. The final ferromanganese phosphate had a (Mn+Fe) / P molar ratio of 0.965.

[0173] Example 7

[0174] The only difference between this embodiment and Embodiment 1 is that, in step S5, the pH value of the seed induction solution is 1.5.

[0175] In step S5, the XRD pattern of the sample obtained after drying is shown below. Figure 16 As shown.

[0176] The final molar ratio of (Mn+Fe) / P in the obtained manganese iron phosphate was found to be 0.98.

[0177] Example 8

[0178] The only difference between this embodiment and Embodiment 1 is that, in step S5, the pH value of the seed induction solution is 2.0.

[0179] In step S5, the XRD pattern of the sample obtained after drying is shown below. Figure 17 As shown.

[0180] The final molar ratio of (Mn+Fe) / P in the obtained manganese iron phosphate was found to be 0.985.

[0181] Example 9

[0182] The only difference between this embodiment and Embodiment 1 is that, in step S5, the heat preservation temperature is 60°C.

[0183] In step S5, the XRD pattern of the sample obtained after drying is shown below. Figure 18 As shown.

[0184] The final molar ratio of (Mn+Fe) / P in the obtained manganese iron phosphate was found to be 0.983.

[0185] Example 10

[0186] The only difference between this embodiment and Embodiment 1 is that, in step S5, the heat preservation temperature is 75°C.

[0187] In step S5, the XRD pattern of the sample obtained after drying is shown below. Figure 19 As shown.

[0188] The final molar ratio of (Mn+Fe) / P in the obtained manganese iron phosphate was found to be 0.98.

[0189] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ferric manganese phosphate, characterized in that, include: (1) Using manganese source, iron source, phosphorus source, ammonia water, acid and water as raw materials, adjust the pH value to 0-4 to prepare a seed crystal induction solution. The iron source is any one of ferric phosphate and ferric phosphate dihydrate mixed with a soluble iron source. In step (1), the total amount of ferric phosphate and ferric phosphate dihydrate is 25-75% of the total molar amount of iron source. (2) Heat the seed crystal induction solution to 60-99°C, add manganese iron ammonium phosphate slurry, and keep it warm for aging; (3) The aged slurry is subjected to solid-liquid separation, drying and calcination to obtain manganese iron phosphate.

2. The method for preparing ferric manganese phosphate as described in claim 1, characterized in that, In step (1), the manganese source is one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate; In step (1), the soluble iron source is one or more of the following: ferrous sulfate (a byproduct of titanium dioxide), industrial-grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, and ferrous acetate. In step (1), the phosphorus source is a soluble phosphorus source; the soluble phosphorus source is selected from one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate. In step (1), the acid is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

3. The method for preparing ferric manganese phosphate as described in claim 1, characterized in that, In step (1), the pH value is adjusted to 0-3.

4. The method for preparing ferric manganese phosphate as described in claim 3, characterized in that, In step (1), the pH value is adjusted to 0 to 2.

5. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, In step (2), the temperature for heat preservation and aging is 60-99℃; the time for heat preservation and aging is 2-4h.

6. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, In step (3), the calcination temperature is 300-600℃.

7. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, The preparation method of the manganese ferric ammonium phosphate slurry includes: mixing manganese ferric ammonium phosphate raw material with water and then pulping it to obtain manganese ferric ammonium phosphate slurry.

8. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, The solid content of the manganese ferric ammonium phosphate slurry is 150-250 g / L.

9. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, The ratio of the total molar amount of Mn and Fe to the molar amount of P in the manganese ferric ammonium phosphate slurry is 1 to 1.05:

1.

10. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, In step (1), the amount of manganese iron ammonium phosphate that can be theoretically prepared from the manganese source, iron source, phosphorus source and ammonia water in the seed crystal induction solution is 5 to 90% of the amount of manganese iron ammonium phosphate in the manganese iron ammonium phosphate slurry.

11. The method for preparing ferric manganese phosphate according to any one of claims 1 to 4, characterized in that, In step (1), the ratio of the total molar amount of Mn and Fe to the molar amount of P in the seed induction solution is less than 1.

12. Ferric manganese phosphate, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 11.

13. The ferromanganese phosphate as described in claim 12, characterized in that, The secondary particle size D50 of the ferromanganese phosphate is 1–30 μm, and the tap density is 0.6–1.5 g / cm³. 3 Specific surface area is 1-10 m² 2 / g, molar ratio n (Mn+Fe) / n P It ranges from 0.95 to 1.

0.

14. A positive electrode active material, characterized in that, It is prepared using manganese iron phosphate as described in claim 12 or 13 as a raw material.

15. A secondary battery, characterized in that, Includes the positive electrode active material as described in claim 14.

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