Lithium iron manganese phosphate precursor and preparation method thereof, lithium iron manganese phosphate, lithium ion battery and electrical equipment

Abstract

The present application provides a lithium iron manganese phosphate precursor and its preparation method, lithium iron manganese phosphate, lithium ion battery and electrical equipment, which relates to the field of new energy technology. The primary particles of the lithium iron manganese phosphate precursor provided in the present application are thick flakes, and the side of the primary particles are porous. The large-sized primary particles and porous lithium iron manganese phosphate precursor have many defects, are easy to grind, have excellent processing performance, and have good Li-ion sintering performance during the sintering process. + It is easier to react with manganese iron phosphate to produce lithium manganese iron phosphate with high sphericity, high compaction density, no other impurities generated, and good capacity and rate performance. The preparation method of the lithium manganese iron phosphate precursor provided in this application can generate large-sized primary particles of hydrated ammonium manganese iron phosphate by adding an excess phosphorus source to a mixed metal salt solution. Furthermore, pyrophosphorylation occurs through high-temperature calcination, generating a large number of pores, and ultimately generating a porous lithium manganese iron phosphate precursor.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a lithium iron manganese phosphate precursor and a preparation method thereof, lithium iron manganese phosphate, a lithium-ion battery and electrical equipment. Background Art

[0002] Lithium iron manganese phosphate exists as a manganese-iron solid solution rather than a simple physical mixture. Doping lithium iron phosphate with manganese effectively combines the advantages of both elements, while also allowing manganese and iron to occupy adjacent positions in the periodic table and possess similar ionic radii, so doping does not significantly affect the original structure. The voltage platform of lithium iron phosphate is 3.4V, while that of lithium iron manganese phosphate is 4.1V. This can increase the energy density of lithium iron phosphate by 20%-30%, approaching the energy density of ternary low-nickel batteries, while remaining less expensive than ternary batteries. Therefore, it has enormous potential.

[0003] Ammonium manganese iron phosphate, as a precursor of lithium manganese iron phosphate, not only makes lithium manganese iron phosphate have a higher compaction density, but also makes (Fe+Mn) / P in lithium manganese iron phosphate less than 1. Therefore, using lithium manganese iron phosphate as a positive electrode material in lithium-ion batteries can improve the specific capacity and cycle performance.

[0004] However, the existing ammonium manganese ferric phosphate has a primary particle shape of thin flakes, and a secondary particle shape of flakes, inserts, or spheres. After dehydration and deammoniation, the thin flake primary particles are highly sensitive to temperature and are prone to large-scale melting in morphology, generating large pores. The physical phases are crystalline manganese pyrophosphate and iron phosphate. As a result, the specific surface area is not much higher than that of the precursor hydrate (the specific surface area after calcination and dehydration is less than 2.5m 2 / g, the increase is 0-1m 2 / g or even decrease), the low specific surface area will make the subsequent sanding process difficult, and the reaction rate of lithium carbonate and ferromanganese phosphate precursor is slow during the sintering process, resulting in a larger driving force for the solid-state phase transition of the ferromanganese phosphate precursor to lithium iron manganese phosphate, which is prone to produce other impurities with poor electrochemical properties, resulting in poor electrochemical performance, poor capacity and rate performance, and incomplete crystallization of the generated lithium iron manganese phosphate, irregular primary particle morphology, and low compaction density. Summary of the Invention

[0005] The purpose of this application is to provide a lithium iron manganese phosphate precursor and its preparation method, lithium iron manganese phosphate, lithium-ion battery and electrical equipment, aiming to solve the problem of poor capacity and rate performance of lithium iron manganese phosphate obtained from the existing lithium iron manganese phosphate precursor.

[0006] To achieve the above objectives, the present application provides a lithium iron manganese phosphate precursor, comprising secondary particles composed of a plurality of primary particles; the primary particles are thick flakes, and the primary particles of the lithium iron manganese phosphate precursor have sides that are fine, dense, and porous. The primary particles have an average length of 5 to 14 μm, an average width of 3 to 10 μm, and an average thickness of 2.0 to 4.0 μm. The porosity of the lithium iron manganese phosphate precursor is 15% to 40%.

[0007] The physical phase of the lithium manganese iron phosphate precursor includes manganese pyrophosphate and iron phosphate, and the peak intensity of the (021) peak of manganese pyrophosphate in the X-ray diffraction spectrum of the lithium manganese iron phosphate precursor is 400-600.

[0008] In some embodiments, at least one of the following conditions is met:

[0009] A. The X-ray diffraction pattern of the lithium manganese iron phosphate precursor is an amorphous peak + a small amount of crystalline peak, and the crystalline peak is located at the position of amorphous peak + crystalline manganese pyrophosphate, or amorphous peak + crystalline manganese pyrophosphate + crystalline iron phosphate, wherein the crystalline peak (021) of crystalline manganese pyrophosphate is the strongest, and the peak intensity range is the highest at 400~600;

[0010] B. The tap density of the lithium manganese iron phosphate precursor is 0.6~1.5m 2 / g;

[0011] C. The D50 of the lithium manganese iron phosphate precursor is 1~80μm.

[0012] In some embodiments, at least one of the following conditions is met:

[0013] A. The pore size range of the pores is 0.05~3μm;

[0014] B. The porosity of the lithium manganese iron phosphate precursor is 15-38.3%;

[0015] C. The specific surface area of ​​the lithium manganese iron phosphate precursor is 1~10m 2 / g, preferably 5-9.2m 2 / g.

[0016] The present application also provides a method for preparing the above-mentioned lithium manganese iron phosphate precursor, comprising:

[0017] Under a protective gas atmosphere, a mixed metal salt solution and an ammonia solution are concurrently introduced into a bottom liquid of a reactor for a coprecipitation reaction, wherein the pH value of the coprecipitation reaction is 4.5-6.0, the bottom liquid comprises a first phosphorus source and ammonium ions, the ammonium ion concentration in the bottom liquid is 1.0-2.5 mol / L, the molar amount of the first phosphorus source is greater than or equal to 0 mol, and the mixed metal salt solution comprises a manganese source, an iron source, and a second phosphorus source, and the total molar amount of the first phosphorus source and the second phosphorus source is 1.5-2.5 times the total molar amount of manganese and iron;

[0018] The reaction slurry is subjected to solid-liquid separation, washing, and drying to obtain ammonium manganese ferrous phosphate;

[0019] The ammonium manganese ferric phosphate is calcined to obtain manganese pyrophosphate and iron phosphate, and the calcination temperature is 400-700°C.

[0020] In some embodiments, at least one of the following conditions is met:

[0021] A. The pH value of the base solution is 4.5-6.0;

[0022] B. the base liquid comprises at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and ammonium chloride;

[0023] C. The pH value of the base solution is adjusted by adding an acidic solution or an alkaline solution; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid; the alkaline solution is one or more of NaOH solution, NaHCO3 solution, Na2CO3 solution, Na2HPO4 solution, and Na3PO4 solution;

[0024] D. the ammonium ion concentration in the base solution is 1.0-2.5 mol / L;

[0025] E. The amount of the base liquid is 10-40% of the volume of the reactor;

[0026] F. The stirring speed of the coprecipitation reaction is 200~1200rpm;

[0027] G. the temperature of the coprecipitation reaction is 40-80°C;

[0028] H. The flow rate of the mixed metal salt solution is 0.05% to 0.5% of the volume of the reactor per minute;

[0029] I. The endpoint of the coprecipitation reaction is when the volume of the reaction slurry reaches 70-90% of the volume of the reactor.

[0030] In some embodiments, at least one of the following conditions is met:

[0031] A. The concentration of the ammonia solution is 5-10 mol / L;

[0032] B. the pH value of the mixed metal salt solution is below 3;

[0033] C. the total molar concentration of manganese and iron in the mixed metal salt solution is 0.2 to 2.0 mol / L;

[0034] D. In the mixed metal salt solution, the molar ratio of manganese to iron is 1 to 2:1;

[0035] E. In the mixed metal salt solution, the molar amount of phosphorus is 1.5 to 2.5 times the total molar amount of manganese and iron;

[0036] F. the mixed metal salt solution further comprises ascorbic acid;

[0037] G. When condition F is met, 0.2-0.8 g of ascorbic acid is added to 1 L of the mixed metal salt solution;

[0038] H. The iron source includes one or more of ferrous sulfate, a byproduct of titanium dioxide, industrial-grade ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous acetate;

[0039] I. The manganese source includes one or more of manganese sulfate, manganese chloride, manganese oxalate, and manganese acetate;

[0040] J. the second phosphorus source comprises one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate;

[0041] K. The mixed metal salt solution further comprises an acidic solution for adjusting pH; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0042] In some embodiments, the calcination temperature is 400-600° C., and the calcination time is 2-6 hours, preferably 3-5 hours.

[0043] The present application also provides a lithium iron manganese phosphate, which is obtained by mixing the above-mentioned lithium iron manganese phosphate precursor with a lithium source and then sintering, or by mixing the lithium iron manganese phosphate precursor obtained by the above-mentioned preparation method with a lithium source and then sintering.

[0044] The present application also provides a lithium-ion battery, comprising the above-mentioned lithium iron manganese phosphate.

[0045] The present application also provides an electrical device comprising the above-mentioned lithium-ion battery.

[0046] Compared with the prior art, the advantages of this application include:

[0047] The lithium iron manganese phosphate precursor provided in the present application includes secondary particles composed of multiple primary particles; the primary particles are thick flakes, and the sides of the primary particles are fine, dense and porous. The average length of the primary particles is 5~14μm, the average width is 3~10μm, and the average thickness is 2.0~4.0μm. The porosity of the lithium iron manganese phosphate precursor is 15%-40%. The physical phases of the lithium iron manganese phosphate precursor include manganese pyrophosphate and iron phosphate, and the peak intensity of the (021) peak of manganese pyrophosphate in the X-ray diffraction pattern of the lithium iron manganese phosphate precursor is 400~600. Thick flake primary particles can increase the melting temperature by 50-100°C, generating tiny pores within the 400-600°C range, increasing the specific surface area and resulting in more defects. During sintering, the reaction rate between lithium carbonate and the ferromanganese phosphate precursor is rapid, requiring a small driving force for the solid-state phase transition from the ferromanganese phosphate precursor to lithium ferromanganese phosphate, making it less likely to produce other impurities with poor electrochemical properties. This results in excellent electrochemical performance, with good capacity and rate capabilities. The resulting lithium ferromanganese phosphate is fully crystalline, with high primary particle morphology sphericity and compaction density. Pyrophosphorylation produces manganese pyrophosphate and iron phosphate, which undergo recrystallization during the pyrophosphorylation process, changing the crystal structure and reducing the overall lattice size, thereby generating pores. This can further increase the porosity of the precursor, thereby improving capacity and rate capabilities.

[0048] Furthermore, the porous lithium manganese iron phosphate precursor has many defects and good processing performance. + It is easier to react with manganese iron phosphate to generate porous manganese iron phosphate with low crystallinity, shortening the Li + Diffusion channel distance, capacity and rate performance are better.

[0049] The method for preparing a lithium iron manganese phosphate precursor provided herein generates large, thick, flaky primary particles of hydrated ammonium iron manganese phosphate by adding an excess phosphorus source to a mixed metal salt solution. Furthermore, high-temperature calcination produces pyrophosphorylation, generating a large number of pores, ultimately resulting in a porous lithium iron manganese phosphate precursor. This is because the pyrophosphorylation process causes recrystallization, which changes the crystal structure and reduces the overall lattice size, thereby generating pores.

[0050] The lithium manganese iron phosphate provided in the present application is obtained by mixing and sintering the lithium manganese iron phosphate precursor of the present application with a lithium source. When applied to lithium-ion batteries and electrical equipment, it has better capacity and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0052] Figure 1This is an SEM image of the pure phase ammonium manganese ferric phosphate containing crystal water of Example 1;

[0053] Figure 2 This is the XRD pattern of the pure phase ammonium manganese ferric phosphate containing crystal water of Example 1;

[0054] Figure 3 This is an SEM image of the lithium manganese iron phosphate precursor of Example 1;

[0055] Figure 4 This is the XRD pattern of the lithium manganese iron phosphate precursor of Example 1;

[0056] Figure 5 This is an SEM image of the lithium manganese iron phosphate precursor of Example 2;

[0057] Figure 6 This is the XRD pattern of the lithium manganese iron phosphate precursor of Example 2;

[0058] Figure 7 This is an SEM image of the lithium manganese iron phosphate precursor of Example 3;

[0059] Figure 8 This is the XRD pattern of the lithium manganese iron phosphate precursor of Example 3;

[0060] Figure 9 This is an SEM image of the lithium manganese iron phosphate precursor of Example 4;

[0061] Figure 10 This is the XRD pattern of the lithium manganese iron phosphate precursor of Example 4;

[0062] Figure 11 This is an SEM image of the pure phase ammonium manganese ferric phosphate containing crystal water of Comparative Example 1;

[0063] Figure 12 This is the XRD pattern of the pure phase ammonium manganese ferric phosphate containing crystal water of Comparative Example 1;

[0064] Figure 13 This is an SEM image of the lithium manganese iron phosphate precursor of Comparative Example 1;

[0065] Figure 14 This is the XRD pattern of the lithium manganese iron phosphate precursor of Comparative Example 1;

[0066] Figure 15 This is an SEM image of the pure phase ammonium manganese ferric phosphate containing crystal water of Comparative Example 3;

[0067] Figure 16 This is the XRD pattern of the pure phase ammonium manganese ferric phosphate containing crystal water of Comparative Example 3;

[0068] Figure 17 This is an SEM image of the lithium iron manganese phosphate precursor of Comparative Example 3;

[0069] Figure 18 This is the XRD pattern of the lithium manganese iron phosphate precursor of Comparative Example 3;

[0070] Figure 19 This is an SEM image of the multiphase ammonium manganese ferric phosphate containing crystal water of Comparative Example 4;

[0071] Figure 20 This is the XRD pattern of the multiphase ammonium manganese iron phosphate containing crystal water of Comparative Example 4;

[0072] Figure 21 This is an SEM image of the lithium manganese iron phosphate precursor of Comparative Example 4;

[0073] Figure 22 This is the XRD pattern of the lithium iron manganese phosphate precursor of Comparative Example 4;

[0074] Figure 23 This is an SEM image of the lithium manganese iron phosphate precursor of Comparative Example 5;

[0075] Figure 24 This is the XRD pattern of the lithium manganese iron phosphate precursor of Comparative Example 5;

[0076] Figure 25 This is an SEM image of the lithium manganese iron phosphate precursor of Comparative Example 6;

[0077] Figure 26 This is the XRD pattern of the lithium manganese iron phosphate precursor of Comparative Example 6. DETAILED DESCRIPTION

[0078] The present application provides a lithium iron manganese phosphate precursor, which includes secondary particles composed of multiple primary particles; the primary particles are thick flakes, and the side surfaces of the primary particles of the lithium iron manganese phosphate precursor are fine, dense and porous. The average length of the primary particles is 5-14 μm, for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or any value between 5 and 14 μm; the average width of the primary particles is 3-10 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm , 7μm, 8μm, 9μm, 10μm or any value between 3~10μm; the average thickness of the primary particles is 2.0~4.0μm, for example, it can be 2.0μm, 2.1μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.7μm, 4.0μm or any value between 2.0~4.0μm; the porosity of the lithium manganese iron phosphate precursor is 15%-40%, for example, it can be 15%, 20%, 25%, 30%, 35%, 40% or any value between 15~40%, preferably 15%-38.3%.

[0079] Thick flake primary particles can increase the melting temperature by 50-100°C, and can generate tiny pores in the range of 400-600°C, increasing the specific surface area and having more defects. During the sintering process, the reaction rate of lithium carbonate and ferromanganese phosphate precursor is fast, and the driving force required for the solid-state phase transition of the ferromanganese phosphate precursor to lithium ferromanganese phosphate is small. It is not easy to produce other impurities with poor electrochemical properties. The electrochemical properties are excellent, and the capacity and rate performance are good. At the same time, the generated lithium ferromanganese phosphate is completely crystallized, the primary particles have high sphericity, and the compaction density is high.

[0080] Porous lithium manganese iron phosphate precursor, with many defects and excellent processing performance, Li + It is easier to react with manganese iron phosphate to generate porous manganese iron phosphate with low crystallinity, shortening the Li + Diffusion channel distance, capacity and rate performance are better.

[0081] In some embodiments, the X-ray diffraction pattern of the lithium manganese iron phosphate precursor is an amorphous peak + a small amount of crystalline peak, and the crystalline peak is located at the amorphous peak + crystalline manganese pyrophosphate, or the amorphous peak + crystalline manganese pyrophosphate + crystalline iron phosphate, wherein the crystalline peak (021) of the crystalline manganese pyrophosphate is the strongest, and the peak intensity range is up to 400~600, for example, it can be 400, 450, 500, 550, 600 or any value between 400~600.

[0082] In some embodiments, the tap density of the lithium manganese iron phosphate precursor is 0.6 to 1.5 m 2 / g, for example, 0.6m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.5m 2 / g or 0.6~1.5m 2 / g; the D50 of the lithium iron manganese phosphate precursor is 1~80μm, for example, it can be 1μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm or any value between 1~80μm.

[0083] In some embodiments, the pore size ranges from 0.05 to 3 μm, for example, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or any value between 0.05 and 3 μm; the specific surface area of ​​the lithium manganese iron phosphate precursor is 1 to 10 m 2 / g, for example, 1m 2 / g, 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g or 1~10m 2 Any value between 5 and 9.2 m / g 2 / g.

[0084] The present application also provides a method for preparing the above-mentioned lithium manganese iron phosphate precursor, comprising:

[0085] Under a protective gas atmosphere, a mixed metal salt solution and an ammonia solution are introduced into a bottom liquid of a reactor in parallel for a coprecipitation reaction, wherein the pH value of the coprecipitation reaction is 4.5-6.0, for example, 4.5, 5, 5.5, 6.0, or any value between 4.5 and 6.0, the bottom liquid comprises a first phosphorus source and ammonium ions, the ammonium ion concentration in the bottom liquid is 1.0-2.5 mol / L, the molar amount of the first phosphorus source is greater than or equal to 0 mol, and the mixed metal salt solution comprises a manganese source, an iron source, and a second phosphorus source, and the total molar amount of the first phosphorus source and the second phosphorus source is 1.5-2.5 times the total molar amount of manganese and iron, for example, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times, 2.5 times, or any value between 1.5 and 2.5 times;

[0086] The reaction slurry is subjected to solid-liquid separation, washing, and drying to obtain ammonium manganese ferrous phosphate;

[0087] The ammonium manganese iron phosphate is calcined to obtain manganese pyrophosphate and iron phosphate. The calcination temperature is 400-700°C, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C or any value between 400-700°C, preferably 400-600°C.

[0088] The present invention provides a method for preparing a lithium iron manganese phosphate precursor. By adding an excess phosphorus source to a mixed metal salt solution, hydrated ammonium iron manganese phosphate (AMMPP) is produced into large, thick, flake-like primary particles. High-temperature calcination produces pyrophosphorylation, generating a large number of pores, ultimately yielding a porous lithium iron manganese phosphate precursor.

[0089] In some embodiments, the pH value of the base solution is 4.5-6.0, for example, it can be 4.5, 5, 5.5, 6.0 or any value between 4.5 and 6.0.

[0090] In some embodiments, the base liquid includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and ammonium chloride; the base liquid of the present application includes at least ammonium ions, and the precursor crystals obtained with pure water as the base liquid are too complete, and the physical phase is not pure ammonium manganese iron phosphate, but a mixture of three physical phases, with a very low specific surface area and too complete crystals.

[0091] In some embodiments, the pH value of the base liquid is adjusted by adding an acidic solution or an alkaline solution; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid; the alkaline solution is one or more of NaOH solution, NaHCO3 solution, Na2CO3 solution, Na2HPO4 solution, and Na3PO4 solution.

[0092] In some embodiments, the ammonium ion concentration in the base liquid is 1.0~2.5 mol / L, for example, it can be 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L or any value between 1.0~2.5 mol / L; the amount of the base liquid is 10~40% of the volume of the reactor, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value between 10~40%.

[0093] In some embodiments, the stirring speed of the coprecipitation reaction is 200~1200 rpm, for example, it can be 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm or any value between 200~1200 rpm; the temperature of the coprecipitation reaction is 40~80°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or any value between 40~80°C.

[0094] In some embodiments, the flow rate of the mixed metal salt solution is 0.05% to 0.5% of the volume of the reactor per minute, for example, it can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or any value between 0.05% and 0.5%; the endpoint of the coprecipitation reaction is that the volume of the reaction slurry reaches 70% to 90% of the volume of the reactor, for example, it can be 70%, 75%, 80%, 85%, 90% or any value between 70% and 90%.

[0095] In some embodiments, the concentration of the ammonia solution is 5-10 mol / L, for example, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L or any value between 5 and 10 mol / L.

[0096] In some embodiments, the pH value of the mixed metal salt solution is below 3; the total molar concentration of manganese and iron in the mixed metal salt solution is 0.2-2.0 mol / L, for example, it can be 0.2 mol / L, 0.5 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L or any value between 0.2-2.0 mol / L; the molar ratio of manganese to iron is 1-2:1, for example, it can be 1:1, 1.1:1, 1.2:1, 1 .3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1 or any value between 1 and 2:1; the ratio of the molar amount of phosphorus to the total molar amount of manganese and iron, P / (Mn+Fe), is 1.5 to 2.5 times, for example, it can be 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times, 2.1 times, 2.2 times, 2.3 times, 2.4 times, 2.5 times or any value between 1.5 and 2.5 times, preferably 1.75 to 2.3 times. When the above ratio P / (Mn+Fe) is too large, it is easy to generate too many pores, resulting in excessive porosity and reduced structural stability; when the above ratio P / (Mn+Fe) is too small, insufficient pores are generated, resulting in too low porosity, making it difficult to generate a porous lithium manganese iron phosphate precursor.

[0097] In some embodiments, the mixed metal salt solution further includes ascorbic acid; preferably, 0.2-0.8 g of ascorbic acid is added to 1 L of the mixed metal salt solution, for example, it can be 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g or any value between 0.2-0.8 g.

[0098] In some embodiments, the mixed metal salt solution further includes an acidic solution for adjusting pH; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0099] In some embodiments, the iron source includes one or more of ferrous sulfate, a by-product of titanium dioxide, industrial-grade ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous acetate; the manganese source includes one or more of manganese sulfate, manganese chloride, manganese oxalate, and manganese acetate; and the second phosphorus source includes one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0100] In some embodiments, the calcination time is 2-6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours or any value between 2-6 hours, preferably 3-5 hours.

[0101] Uncalcined ammonium manganese iron phosphate (AMMP) produces a significant amount of ammonia during the preparation of cathode materials, significantly impacting the atmosphere for the formation of lithium manganese iron phosphate. Ammonia reacts with reducing carbon to form toxic HCN, posing a significant safety hazard. Furthermore, ammonia decomposes at a temperature between 400-450°C, which can affect subsequent reactions between the precursor and lithium.

[0102] The present application also provides a lithium iron manganese phosphate, which is obtained by mixing the above-mentioned lithium iron manganese phosphate precursor with a lithium source and then sintering, or by mixing the lithium iron manganese phosphate precursor obtained by the above-mentioned preparation method with a lithium source and then sintering.

[0103] The present application also provides a lithium-ion battery, comprising the above-mentioned lithium iron manganese phosphate.

[0104] The present application also provides an electrical device comprising the above-mentioned lithium-ion battery.

[0105] The lithium manganese iron phosphate provided in the present application is obtained by mixing and sintering the lithium manganese iron phosphate precursor of the present application with a lithium source. When applied to lithium-ion batteries and electrical equipment, it has better capacity and rate performance.

[0106] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0107] Example 1

[0108] Example 1 provides a lithium manganese iron phosphate precursor, and its preparation method includes the following steps. The reactor is 100L. Detailed process parameter comparison is shown in Table 1:

[0109] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare a 0.9 mol / L manganese sulfate solution, a 0.6 mol / L ferrous sulfate solution, and a 2.5 mol / L phosphoric acid solution, and mixing to prepare 50 L of a solution, wherein the molar ratio of Mn to Fe is 6:4. 25 g of ascorbic acid is further added, and the mixture is filtered to obtain a solution A;

[0110] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0111] Step S3: preparing 30 L of 1.6 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C; the P / (Mn+Fe) ratio of the total molar amount of the first phosphorus source and the second phosphorus source to the total molar amount of manganese and iron is shown in Table 1;

[0112] Step S4: Solution C was added to the reactor, heated to 50°C, stirred, and acid was added to adjust the pH value of the solution in the reactor to 6.0. Solution A was added to the reactor at a process flow rate of 400 ml / min. Solution B and solution A were fed in parallel, and the pH value of the system was controlled to be 6.0±0.1. The nitrogen flow rate was 10 ml / min until solution A was used up. The solid-liquid separation was performed and the filter cake was washed with pure water. The filter cake was dried at 120°C for 15 h to obtain pure phase ammonium manganese iron phosphate containing crystal water, and its SEM image is shown as follows. Figure 1 As shown, the XRD pattern is Figure 2 As shown;

[0113] Step S5: calcining the dried manganese iron phosphate containing crystal water at 550°C for 4 hours to obtain the lithium manganese iron phosphate precursor of Example 1, the SEM image of which is as follows: Figure 3 As shown, the XRD pattern is Figure 4 shown.

[0114] Example 2

[0115] Example 2 provides a lithium manganese iron phosphate precursor, and its preparation method includes the following steps. The reactor is 100 L. Detailed process parameter comparison is shown in Table 1:

[0116] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare a 0.9 mol / L manganese sulfate solution, a 0.6 mol / L ferrous sulfate solution, and a 2.5 mol / L phosphoric acid solution; mixing to prepare 50 L of a solution in which the molar ratio of Mn to Fe is 1:1; adding 10 g of ascorbic acid; and filtering to obtain a solution A;

[0117] Step S2: preparing 5.0 mol / L ammonia water and filtering to obtain solution B;

[0118] Step S3: preparing 10 L of 1.0 mol / L ammonium dihydrogen phosphate solution and filtering to obtain solution C;

[0119] Step S4: adding solution C to a reactor, heating to 40°C, stirring, and adding acid to adjust the pH value of the solution in the reactor to 4.5; adding solution A to the reactor at a process flow rate of 50 ml / min; feeding solution B and solution A in parallel; controlling the pH value of the system to 4.5±0.1; and adding nitrogen at a flow rate of 10 ml / min until solution A is used up; performing solid-liquid separation, washing with pure water, obtaining a filter cake, and drying at 120°C for 15 h to obtain pure phase ammonium manganese ferric phosphate containing water of crystallization;

[0120] Step S5: calcining the dried ammonium manganese iron phosphate containing crystal water at 400°C for 4 hours to obtain the lithium manganese iron phosphate precursor of Example 2, the SEM image of which is as follows: Figure 5 As shown, the XRD pattern is Figure 6 shown.

[0121] Example 3

[0122] Example 3 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0123] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare a 0.9 mol / L manganese sulfate solution, a 0.6 mol / L ferrous sulfate solution, and a 2.5 mol / L phosphoric acid solution; mixing to prepare 50 L of a solution in which the molar ratio of Mn to Fe is 2:1; adding 10 g of ascorbic acid; and filtering to obtain a solution A;

[0124] Step S2: preparing 5.0 mol / L ammonia water and filtering to obtain solution B;

[0125] Step S3: preparing 40 L of 2.5 mol / L ammonium dihydrogen phosphate solution, filtering, and obtaining solution C;

[0126] Step S4: adding solution C to the reactor, heating to 80°C, stirring, adding acid to adjust the pH value of the solution in the reactor to 6.0, adding solution A to the reactor at a process flow rate of 500 ml / min, feeding solution B and solution A in parallel, controlling the pH value of the system to 6.0±0.1, and nitrogen flow rate of 10 ml / min until solution A is used up, separating the solid and liquid, washing with pure water to obtain a filter cake, and drying at 120°C for 15 hours to obtain pure phase ammonium manganese iron phosphate containing crystal water;

[0127] Step S5: calcining the dried ammonium manganese iron phosphate containing crystal water at 600°C for 4 hours to obtain the lithium manganese iron phosphate precursor of Example 3, the SEM image of which is as follows: Figure 7 As shown, the XRD pattern is Figure 8 shown.

[0128] Example 4

[0129] Example 4 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0130] Step S1: dissolving manganese chloride, ferrous chloride, and phosphoric acid in deionized water to prepare 0.9 mol / L manganese chloride solution, 0.6 mol / L ferrous chloride solution, and 3.75 mol / L phosphoric acid solution. Prepare 50 L of solution with a molar ratio of Mn to Fe of 6:4, add 25 g of ascorbic acid, and filter to obtain solution A;

[0131] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0132] Step S3: Prepare 30 L of 1.6 mol / L ammonium chloride and filter to obtain solution C;

[0133] Step S4: adding solution C to the reactor, heating to 50° C., stirring, adding acid to adjust the pH value of the solution in the reactor to 6.0, adding solution A to the reactor at a process flow rate of 400 ml / min, feeding solution B and solution A in parallel, controlling the system pH value to 6.0±0.1, and nitrogen flow rate of 10 ml / min until solution A is used up, separating the solid and liquid, washing with pure water to obtain a filter cake, and drying at 120° C. for 15 h to obtain pure phase ammonium manganese ferric phosphate containing crystal water;

[0134] Step S5: calcining the dried manganese iron phosphate containing crystal water at 550°C for 4 hours to obtain the lithium manganese iron phosphate precursor of Example 4, the SEM image of which is as follows: Figure 9 As shown, the XRD pattern is Figure 10 shown.

[0135] Comparative Example 1

[0136] Comparative Example 1 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0137] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare 0.9 mol / L manganese sulfate solution, 0.6 mol / L ferrous sulfate solution, and 2.5 mol / L phosphoric acid solution. Prepare 50 L of solution with a molar ratio of Mn to Fe of 6:4, add 25 g of ascorbic acid, and filter to obtain Solution A;

[0138] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0139] Step S3: preparing 30 L of 1.6 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C;

[0140] Step S4: Solution C was added to the reactor, heated to 45°C, stirred, and acid was added to adjust the pH value of the solution in the reactor to 7.0. Solution A was added to the reactor at a process flow rate of 400 ml / min. Solution B and solution A were fed in parallel, and the pH value of the system was controlled to 7.0±0.1. The nitrogen flow rate was 10 ml / min until solution A was used up. The solid-liquid separation was performed and the filter cake was washed with pure water. The filter cake was dried at 120°C for 15 h to obtain pure phase ammonium manganese iron phosphate containing crystal water, and its SEM image is shown as follows. Figure 11 As shown, the XRD pattern is Figure 12 As shown;

[0141] Step S5: calcining the dried manganese iron phosphate containing crystal water at 550°C for 4 hours to obtain the manganese iron phosphate lithium precursor of Comparative Example 1, the SEM image of which is as follows: Figure 13 As shown, the XRD pattern is Figure 14 shown.

[0142] Comparative Example 2

[0143] Comparative Example 2 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0144] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare 0.9 mol / L manganese sulfate solution, 0.6 mol / L ferrous sulfate solution, and 2.5 mol / L phosphoric acid solution. Prepare 50 L of solution with a molar ratio of Mn to Fe of 6:4, add 25 g of ascorbic acid, and filter to obtain Solution A;

[0145] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0146] Step S3: preparing 30 L of 1.6 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C;

[0147] Step S4: adding solution C to the reactor, heating to 50° C., stirring, adding acid to adjust the pH value of the solution in the reactor to 6.0, adding solution A to the reactor at a process flow rate of 400 ml / min, feeding solution B and solution A in parallel, controlling the system pH value to 6.0±0.1, and nitrogen flow rate of 10 ml / min until solution A is used up, separating the solid and liquid, washing with pure water to obtain a filter cake, and drying at 120° C. for 15 h to obtain pure phase ammonium manganese ferric phosphate containing crystal water;

[0148] The calcination in step S5 as in Example 1 was not performed, and the product was used directly as a manganese ferrophosphate precursor.

[0149] Comparative Example 3

[0150] Comparative Example 3 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0151] Step S1: dissolving manganese sulfate and ferrous sulfate in deionized water to prepare 0.9 mol / L manganese sulfate solution and 0.6 mol / L ferrous sulfate solution, preparing 50 L of solution with a molar ratio of Mn to Fe of 6:4, adding 25 g of ascorbic acid, and filtering to obtain solution A;

[0152] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0153] Step S3: preparing 30 L of 2.5 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C;

[0154] Step S4: Solution C was added to the reactor, heated to 50°C, stirred, and acid was added to adjust the pH value of the solution in the reactor to 6.0. Solution A was added to the reactor at a process flow rate of 400 ml / min. Solution B and solution A were fed in parallel, and the pH value of the system was controlled to be 6.0±0.1. The nitrogen flow rate was 10 ml / min until solution A was used up. The solid-liquid separation was performed and the filter cake was washed with pure water. The filter cake was dried at 120°C for 15 h to obtain pure phase ammonium manganese iron phosphate containing crystal water, and its SEM image is shown as follows. Figure 15 As shown, the XRD pattern is Figure 16 As shown;

[0155] Step S6: calcining the dried manganese iron phosphate containing crystal water at 550°C for 4 hours to obtain the manganese iron phosphate lithium precursor of Comparative Example 3, the SEM image of which is as follows: Figure 17 As shown, the XRD pattern is Figure 18 shown.

[0156] Comparative Example 4

[0157] Comparative Example 4 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0158] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare 0.9 mol / L manganese sulfate solution, 0.6 mol / L ferrous sulfate solution, and 2.5 mol / L phosphoric acid solution. Prepare 50 L of solution with a molar ratio of Mn to Fe of 6:4, add 25 g of ascorbic acid, and filter to obtain solution A;

[0159] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0160] Step S3: 30L of pure water was added to the reactor, the temperature was raised to 50°C, stirred, and acid was added to adjust the pH value of the solution in the reactor to 6.0. Solution A was added to the reactor at a process flow rate of 400ml / min, and solution B and solution A were fed in parallel. The pH value of the system was controlled to be 6.0±0.1, and the nitrogen flow rate was 10ml / min until solution A was used up. The solid-liquid separation was performed and the filter cake was washed with pure water. The filter cake was dried at 120°C for 15h to obtain ammonium manganese iron phosphate containing crystallization water and other impurities. The SEM image thereof is shown as follows Figure 19 As shown, the XRD pattern is Figure 20 As shown;

[0161] Step S5: calcining the dried manganese iron phosphate containing crystal water at 550°C for 4 hours to obtain the manganese iron phosphate lithium precursor of Comparative Example 4, the SEM image of which is as follows: Figure 21 As shown, the XRD pattern is Figure 22 shown.

[0162] Comparative Example 5

[0163] Comparative Example 5 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0164] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare a 0.9 mol / L manganese sulfate solution, a 0.6 mol / L ferrous sulfate solution, and a 2.5 mol / L phosphoric acid solution, and mixing to prepare 50 L of a solution, wherein the molar ratio of Mn to Fe is 6:4. 25 g of ascorbic acid is further added, and the mixture is filtered to obtain a solution A;

[0165] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0166] Step S3: preparing 30 L of 1.6 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C; the P / (Mn+Fe) ratio of the total molar amount of the first phosphorus source and the second phosphorus source to the total molar amount of manganese and iron is shown in Table 1;

[0167] Step S4: adding solution C to the reactor, heating to 50° C., stirring, adding acid to adjust the pH value of the solution in the reactor to 6.0, adding solution A to the reactor at a process flow rate of 400 ml / min, feeding solution B and solution A in parallel, controlling the system pH value to 6.0±0.1, and nitrogen flow rate of 10 ml / min until solution A is used up, separating the solid and liquid, washing with pure water to obtain a filter cake, and drying at 120° C. for 15 h to obtain pure phase ammonium manganese ferric phosphate containing crystal water;

[0168] Step S5: calcining the dried manganese iron phosphate containing crystal water at 300°C for 4 hours to obtain the manganese iron phosphate lithium precursor of Comparative Example 5, the SEM image of which is as follows: Figure 23 As shown, the XRD pattern is Figure 24 shown.

[0169] Comparative Example 6

[0170] Comparative Example 6 provides a lithium manganese iron phosphate precursor, the preparation method of which includes the following steps, the reactor is 100L, and the detailed process parameters are compared in Table 1:

[0171] Step S1: dissolving manganese sulfate, ferrous sulfate, and phosphoric acid in deionized water to prepare a 0.9 mol / L manganese sulfate solution, a 0.6 mol / L ferrous sulfate solution, and a 2.5 mol / L phosphoric acid solution, and mixing to prepare 50 L of a solution, wherein the molar ratio of Mn to Fe is 6:4. 25 g of ascorbic acid is further added, and the mixture is filtered to obtain a solution A;

[0172] Step S2: preparing 6.5 mol / L ammonia water and filtering to obtain solution B;

[0173] Step S3: preparing 30 L of 1.6 mol / L ammonium dihydrogen phosphate and filtering to obtain solution C; the P / (Mn+Fe) ratio of the total molar amount of the first phosphorus source and the second phosphorus source to the total molar amount of manganese and iron is shown in Table 1;

[0174] Step S4: adding solution C to the reactor, heating to 50° C., stirring, adding acid to adjust the pH value of the solution in the reactor to 6.0, adding solution A to the reactor at a process flow rate of 400 ml / min, feeding solution B and solution A in parallel, controlling the system pH value to 6.0±0.1, and nitrogen flow rate of 10 ml / min until solution A is used up, separating the solid and liquid, washing with pure water to obtain a filter cake, and drying at 120° C. for 15 h to obtain pure phase ammonium manganese ferric phosphate containing crystal water;

[0175] Step S5: The dried manganese iron phosphate containing crystal water was calcined at 800°C for 4 hours to obtain the manganese iron phosphate lithium precursor of Comparative Example 6, the SEM image of which is as follows: Figure 25 As shown, the XRD pattern is Figure 26 shown.

[0176] The lithium manganese iron phosphate precursors of each embodiment and comparative example were tested for product indicators, and the test methods were as follows:

[0177] Particle size D50: Malvern 3000 particle size analyzer;

[0178] Specific surface area: Specific surface area tester, model BSD-BET400, manufacturer: Best Instrument Technology (Beijing) Co., Ltd.

[0179] Tap density: Tap density meter, model BT-313, manufacturer is Dandong Better Instrument Co., Ltd.

[0180] Primary particle size test method: Use Nano Measurer test software, open the SEM electron microscope image, first determine the scale and input it into the system, then select 10-20 primary particles, and the software will automatically calculate and count the primary particle size.

[0181] XRD test method: Place the sample in the center of the groove on the slide, compact it with a cover glass, and place it in the X-ray diffractometer. Set the scanning mode to step scanning, 8° / min, and step length 0.02°.

[0182] Porosity test method: Fully automatic porosity measuring instrument, model BSD-660, manufactured by Best Instrument Technology (Beijing) Co., Ltd. The test principle is to introduce a certain amount of adsorbate gas N into the sample tube at liquid nitrogen temperature (77.3K). 2 , the adsorption amount at the partial pressure point is obtained through PV=nRT; then the specific surface area of ​​the sample can be calculated through theoretical formulas such as BET or Langmuir, and the adsorbate gas is gradually added to increase the adsorption equilibrium pressure, and the adsorption-desorption isotherm is obtained to obtain the porosity.

[0183] The process parameters of each embodiment and comparative example are shown in Table 1, and the product parameters of the lithium manganese iron phosphate precursor of each embodiment and comparative example are shown in Table 2.

[0184] Table 1 Process parameters of Examples and Comparative Examples

[0185]

[0186] Table 2 Product parameters of lithium manganese iron phosphate precursors of various embodiments and comparative examples

[0187]

[0188] The lithium iron manganese phosphate precursors of the examples and comparative examples were mixed with a lithium source and sintered to obtain lithium iron manganese phosphate, and electrochemical performance tests were performed.

[0189] In addition to the lithium source, the raw materials may also include a carbon source, a doping element compound, etc. The preparation method of the positive electrode material may adopt a conventional preparation process in the art. For example, a manganese iron phosphate precursor, sucrose, polyethylene glycol, titanium dioxide (or other doping element compound), and lithium carbonate may be weighed in conventional proportions, dissolved in pure water, and the mixture slurry is sand-milled to D50 = 300~500nm in a sand mill, spray granulated, and the sprayed particles are sintered at 700~750°C and crushed to obtain a manganese iron phosphate lithium positive electrode material.

[0190] Battery assembly method:

[0191] Lithium manganese iron phosphate, PVP, EC300J, and NMP were mixed into a slurry in proportion, evenly coated on aluminum foil, dried at 90°C, and punched to obtain the positive electrode sheet. The button battery was assembled in the order of positive electrode sheet, electrolyte, diaphragm, electrolyte, lithium sheet, gasket, and shrapnel. After standing for 24 hours, it was first charged to 4.5V with a constant current of 0.1C (i.e., a current of 0.1559mA), then charged at a constant voltage of 4.5V to a cutoff current of 0.05mA, stood for 5 minutes, discharged at 0.1C (0.1559mA) to 2.0V, stood for 5 minutes, charged to 4.5V with 0.2C (0.3119mA), charged at a constant voltage to a cutoff current of 0.05mA, stood for 5 minutes, discharged to 2.0V with 0.5C, and then charged and discharged with 1C.

[0192] Table 3 Electrochemical properties of lithium manganese iron phosphate of various examples and comparative examples

[0193]

[0194] The electrochemical properties of the lithium manganese iron phosphate of each embodiment and comparative example are shown in Table 3. According to Table 3, the capacity and rate performance of the lithium manganese iron phosphate of the embodiment of the present application are better than those of the lithium manganese iron phosphate of the comparative example.

[0195] In Comparative Example 1, since the pH value of the solution in the reactor is 7.0, which is too high, the primary particles are very thin and have low porosity, which makes processing difficult (not easy to grind). + The difficulty of reacting with the precursor increases, not only the discharge capacity and rate performance deteriorate, but also the magnetic substance iron phosphide is easily produced, which increases magnetic foreign matter. In Comparative Example 2, since the calcination of step S5 is not carried out, the porosity is very low. In Comparative Example 3, the second phosphorus source is not added, P / (Mn+Fe) is 1, the primary particles are very thin, and the peak intensity rises very quickly at the same calcination temperature, and the morphology before and after calcination is almost unchanged, and the porosity is low. In Comparative Example 4, pure water is used as the base liquid, and the first phosphorus source and ammonium ions are not added. Some miscellaneous phases will be generated between 10°-20°, and the miscellaneous phases will inhibit pyrophosphorylation and reduce porosity. In Comparative Example 5, the calcination temperature is only 300°C, the deamination is not thorough, and manganese pyrophosphate is not generated, and the porosity is low. In Comparative Example 6, the calcination temperature is 800°C, which is too high, and a large amount of manganese pyrophosphate is produced. The manganese pyrophosphate crystals are intact and the porosity is greatly reduced.

[0196] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A lithium manganese iron phosphate precursor, characterized in that: The lithium iron manganese phosphate precursor includes secondary particles composed of multiple primary particles; the primary particles are thick flakes, and the side surfaces of the primary particles of the lithium iron manganese phosphate precursor are fine, dense and porous. The average length of the primary particles is 5-14 μm, the average width is 3-10 μm, and the average thickness is 2.0-4.0 μm. The porosity of the lithium iron manganese phosphate precursor is 15%-40%; The phase of the lithium manganese iron phosphate precursor includes manganese pyrophosphate and iron phosphate, and the peak intensity of the (021) peak of manganese pyrophosphate in the X-ray diffraction pattern of the lithium manganese iron phosphate precursor is 400-600; The preparation method of the lithium manganese iron phosphate precursor comprises: Under a protective gas atmosphere, a mixed metal salt solution and an ammonia solution are concurrently introduced into a bottom liquid of a reactor for a coprecipitation reaction, wherein the pH value of the coprecipitation reaction is 4.5-6.0, the bottom liquid comprises a first phosphorus source and ammonium ions, the ammonium ion concentration in the bottom liquid is 1.0-2.5 mol / L, and the mixed metal salt solution comprises a manganese source, an iron source, and a second phosphorus source, and the total molar amount of the first phosphorus source and the second phosphorus source is 1.5-2.5 times the total molar amount of manganese and iron; The reaction slurry is subjected to solid-liquid separation, washing, and drying to obtain ammonium manganese ferrous phosphate; The ammonium manganese ferric phosphate is calcined to obtain manganese pyrophosphate and iron phosphate, and the calcination temperature is 400-700°C.

2. The lithium iron manganese phosphate precursor according to claim 1, characterized in that At least one of the following conditions is met: A. The tap density of the lithium manganese iron phosphate precursor is 0.6~1.5m 2 / g; B. The D50 of the lithium manganese iron phosphate precursor is 1-80 μm.

3. The lithium iron manganese phosphate precursor according to claim 1 or 2, characterized in that At least one of the following conditions is met: A. The pore size range of the pores is 0.05~3μm; B. The specific surface area of ​​the lithium manganese iron phosphate precursor is 1~10m 2 / g.

4. A method for preparing a lithium manganese iron phosphate precursor according to any one of claims 1 to 3, characterized in that: include: Under a protective gas atmosphere, a mixed metal salt solution and an ammonia solution are concurrently introduced into a bottom liquid of a reactor for a coprecipitation reaction, wherein the pH value of the coprecipitation reaction is 4.5-6.0, the bottom liquid comprises a first phosphorus source and ammonium ions, the ammonium ion concentration in the bottom liquid is 1.0-2.5 mol / L, and the mixed metal salt solution comprises a manganese source, an iron source, and a second phosphorus source, and the total molar amount of the first phosphorus source and the second phosphorus source is 1.5-2.5 times the total molar amount of manganese and iron; The reaction slurry is subjected to solid-liquid separation, washing, and drying to obtain ammonium manganese ferrous phosphate; The ammonium manganese ferric phosphate is calcined to obtain manganese pyrophosphate and iron phosphate, and the calcination temperature is 400-700°C.

5. The method for preparing a lithium iron manganese phosphate precursor according to claim 4, wherein: At least one of the following conditions is met: A. The pH value of the base solution is 4.5-6.0; B. the base liquid comprises at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and ammonium chloride; C. The pH value of the base solution is adjusted by adding an acidic solution or an alkaline solution; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid; the alkaline solution is one or more of NaOH solution, NaHCO3 solution, Na2CO3 solution, Na2HPO4 solution, and Na3PO4 solution; D. the ammonium ion concentration in the base solution is 1.0-2.5 mol / L; E. The amount of the base liquid is 10-40% of the volume of the reactor; F. The stirring speed of the coprecipitation reaction is 200~1200rpm; G. the temperature of the coprecipitation reaction is 40-80°C; H. The flow rate of the mixed metal salt solution is 0.05% to 0.5% of the volume of the reactor per minute; I. The endpoint of the coprecipitation reaction is when the volume of the reaction slurry reaches 70-90% of the volume of the reactor.

6. The method for preparing a lithium iron manganese phosphate precursor according to claim 5, wherein: At least one of the following conditions is met: A. The concentration of the ammonia solution is 5-10 mol / L; B. the pH value of the mixed metal salt solution is below 3; C. the total molar concentration of manganese and iron in the mixed metal salt solution is 0.2 to 2.0 mol / L; D. In the mixed metal salt solution, the molar ratio of manganese to iron is 1 to 2:1; E. In the mixed metal salt solution, the molar amount of phosphorus is 1.5 to 2.5 times the total molar amount of manganese and iron; F. the mixed metal salt solution further comprises ascorbic acid; G. When condition F is met, 0.2-0.8 g of ascorbic acid is added to 1 L of the mixed metal salt solution; H. The iron source includes one or more of ferrous sulfate, a byproduct of titanium dioxide, industrial-grade ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous acetate; I. The manganese source includes one or more of manganese sulfate, manganese chloride, manganese oxalate, and manganese acetate; J. the second phosphorus source comprises one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; K. The mixed metal salt solution further comprises an acidic solution for adjusting pH; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

7. The method for preparing a lithium iron manganese phosphate precursor according to claim 4, wherein: The calcination temperature is 400-600° C., and the calcination time is 2-6 hours.

8. A lithium manganese iron phosphate, characterized in that: The lithium manganese iron phosphate precursor is obtained by mixing the lithium iron phosphate precursor according to any one of claims 1 to 3 with a lithium source and then sintering, or the lithium iron phosphate precursor prepared by the preparation method according to any one of claims 4 to 6 is obtained by mixing the lithium iron phosphate precursor with a lithium source and then sintering.

9. A lithium-ion battery, characterized in that: Including the lithium manganese iron phosphate as described in claim 8.

10. An electrical device, characterized in that: Including the lithium ion battery according to claim 9.

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