Lithium manganese iron phosphate precursor hydrate and preparation method thereof, lithium manganese iron phosphate precursor and preparation method thereof, lithium manganese iron phosphate and secondary battery

Abstract

The invention provides a lithium manganese iron phosphate precursor hydrate which comprises a mixture of manganese phosphorus ore phase manganese manganese phosphate and ammonium manganese iron phosphate, and the molar ratio of the manganese phosphorus ore phase manganese manganese phosphate to the ammonium manganese iron phosphate is (1: 9)-(1: 1). A precursor material obtained by roasting the precursor hydrate is uniform in manganese and iron element distribution and good in processability, and lithium manganese iron phosphate with relatively high compaction density, relatively high capacity and better comprehensive performance can be prepared. The invention also provides a preparation method of the lithium iron manganese phosphate precursor hydrate, a lithium iron manganese phosphate precursor, lithium iron manganese phosphate and a secondary battery.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion battery positive electrode materials, and specifically relates to lithium manganese iron phosphate precursor hydrate and a preparation method and application thereof. Background Art

[0002] Lithium iron manganese phosphate (LiMn x Fe 1-x PO 4 ) is in lithium iron phosphate (LiFePO 4 ) is a new type of phosphate lithium battery positive electrode material formed by doping a certain proportion of manganese on . On the one hand, doping allows the advantages of iron and manganese to be effectively combined. On the other hand, manganese and iron are adjacent in the periodic table and have similar ionic radii, so doping will not significantly affect the original structure.

[0003] Compared with lithium iron phosphate, the high voltage characteristic of manganese makes lithium iron phosphate have a higher voltage platform, which also leads to higher energy density when the specific capacity is the same. Under the same conditions, the energy density is 10~20% higher than that of lithium iron phosphate. Compared with the layered structure of ternary NCM materials, lithium iron phosphate has the same olivine structure as lithium iron phosphate, and the structure is more stable during the charging and discharging process. Even if all lithium ions are embedded during the charging process, the structure will not collapse, so it is safer. In addition, lithium iron phosphate has obvious advantages in the cost per watt. In the development of this material, on the one hand, the conductivity of pure LMFP is improved by coating, doping and nano-sizing; on the other hand, lithium manganese iron phosphate is compounded with ternary 523, LCO and other materials to further integrate the advantages of the materials, complement each other's shortcomings through compounding, improve energy density, and have more comprehensive and integrated battery performance.

[0004] As the precursor of lithium iron manganese phosphate, ferromanganese phosphate largely determines the performance of lithium iron manganese phosphate. Currently, there is relatively little research on ferromanganese phosphate in China.

[0005] CN115072692A discloses ferromanganese phosphate of pyrophosphate type and its preparation method and application, wherein diammonium phosphate is added to a mixed solution of a manganese source and an iron source, and the solution is aged at elevated temperatures to obtain highly crystalline ferromanganese phosphate of pyrophosphate type.

[0006] CN115043387A discloses a method for preparing ammonium manganese iron phosphate, comprising: (1) mixing a metal mixed salt solution, a diammonium phosphate solution and an organic solution respectively to obtain a metal salt mixed solution and a phosphate mixed solution; the metal mixed salt solution is a mixed solution of manganese salt and ferrous salt, and the organic solution is obtained by dissolving a surfactant in an organic solvent; (2) under an inert atmosphere, adding the metal salt mixed solution, the phosphate mixed solution and a first ammonia water to a base liquid in parallel to react, and when the reaction material reaches a target particle size, solid-liquid separation is performed to obtain the ammonium manganese iron phosphate; the base liquid is a mixed solution of the phosphate mixed solution and a second ammonia water. This method uses an organic solvent for synthesis, and the wastewater treatment cost is relatively high. Summary of the invention

[0007] In response to the above technical problems, the present application provides a lithium iron manganese phosphate precursor hydrate and a preparation method thereof, a lithium iron manganese phosphate precursor and a preparation method thereof, lithium iron manganese phosphate, and a secondary battery.

[0008] To achieve the above objectives, this application proposes the following technical solutions: In a first aspect, a lithium iron manganese phosphate precursor hydrate is provided, comprising a mixture of ferromanganese phosphate in a pyrophosphate phase and ammonium iron manganese phosphate, wherein the molar ratio of the ferromanganese phosphate in the pyrophosphate phase to the ammonium iron manganese phosphate is 1:9 to 1:1.

[0009] Furthermore, the molar ratio of the ferromanganese phosphate and ammonium ferromanganese phosphate in the red phosphorus manganese ore phase is 1:9 to 4:6.

[0010] In a second aspect, a method for preparing a lithium manganese iron phosphate precursor hydrate is provided, comprising: S1, adding solution A and ammonia solution to the synthesis kettle bottom liquid in parallel, stirring and reacting under a protective gas atmosphere, controlling the pH value of the reaction system to be 3-7 during the reaction, and obtaining a reaction slurry; the ammonium ion concentration in the synthesis kettle bottom liquid is 0.1-1.5 mol / L; the solution A is a solution prepared by raw materials including a manganese source, a divalent iron source, a phosphorus source and water; S2. The reaction slurry is subjected to solid-liquid separation, washing and drying to obtain a composite phase lithium manganese iron phosphate precursor hydrate containing crystal water.

[0011] In a third aspect, a lithium iron manganese phosphate precursor is provided, which is obtained by calcining the aforementioned lithium iron manganese phosphate precursor hydrate or the lithium iron manganese phosphate precursor hydrate prepared by the aforementioned preparation method.

[0012] In a fourth aspect, lithium manganese iron phosphate is provided, which is obtained by mixing the aforementioned lithium manganese iron phosphate precursor with a lithium source and then subjecting it to processes such as sand milling, spraying, and sintering, or by mixing the lithium manganese iron phosphate precursor prepared by the aforementioned preparation method with a lithium source and then subjecting it to processes such as sand milling, spraying, and sintering.

[0013] In a fifth aspect, a secondary battery is provided, comprising the aforementioned lithium manganese iron phosphate.

[0014] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: A lithium iron manganese phosphate precursor hydrate is provided, including a mixture of a certain proportion of red phosphorus manganese ore phase iron manganese phosphate and ammonium iron manganese phosphate. The precursor material obtained by roasting the precursor hydrate has uniform distribution of manganese and iron elements and good processing performance, and can be used to prepare lithium iron manganese phosphate with higher compaction density, higher capacity and better comprehensive performance.

[0015] The invention provides a method for preparing a lithium manganese iron phosphate precursor hydrate, which has the advantages of short process flow, low cost, no need for surfactant, good controllability, etc. The precursor material obtained by calcining the prepared precursor hydrate has uniform distribution of metal elements and good processing performance, and can prepare lithium manganese iron phosphate with higher compaction density, higher capacity and better comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a SEM image of the precursor containing crystalline water obtained in step S3 of Example 1.

[0018] Figure 2 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 1.

[0019] Figure 3 This is a SEM image of the anhydrous precursor obtained in step S4 of Example 1.

[0020] Figure 4 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 1.

[0021] Figure 5 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 2.

[0022] Figure 6 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 2.

[0023] Figure 7 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 3.

[0024] Figure 8This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 3.

[0025] Fig. 9 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 4.

[0026] Fig.10 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 4.

[0027] Fig.11 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of comparative example 1.

[0028] Fig.12 This is the XRD pattern of the anhydrous precursor obtained in step S4 of comparative example 1.

[0029] Fig.13 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of comparative example 2.

[0030] Fig.14 This is the XRD pattern of the anhydrous precursor obtained in step S4 of comparative example 2.

[0031] Fig.15 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 5.

[0032] Fig.16 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 5.

[0033] Fig.17 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 6.

[0034] Fig.18 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 6.

[0035] Fig.19 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 7.

[0036] Fig. 20 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 7.

[0037] Fig.21 This is the XRD pattern of the anhydrous precursor obtained in step S4 of Example 8.

[0038] Fig. 22 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 9.

[0039] Fig.23 This is the XRD pattern of the precursor containing crystalline water obtained in step S3 of Example 10. DETAILED DESCRIPTION

[0040] The applicant has found through research that the lithium iron manganese phosphate prepared from the ferromanganese phosphate obtained by calcining the pure phase red phosphorus manganese ore type ferromanganese phosphate hydrate as a raw material has a high compaction density, but poor processing performance (difficult to grind, many grinding times are required, and the grinding time is long), and the capacity is low, while the lithium iron manganese phosphate prepared from the ferromanganese phosphate obtained by calcining the pure phase ammonium iron manganese phosphate hydrate as a raw material has a low compaction density, but good processing performance (easy to grind, few grinding times are required, and the grinding time is short), and high capacity. Based on this, the applicant provides a mixed phase precursor hydrate containing a certain proportion of red phosphorus manganese ore type ferromanganese phosphate and ammonium iron manganese phosphate. The precursor prepared using the precursor hydrate as a raw material has good processing performance and can prepare lithium iron manganese phosphate with good compaction density and capacity. Based on this, the present invention is completed.

[0041] The lithium iron manganese phosphate precursor hydrate comprises a mixture of ferromanganese phosphate in the red phosphate manganese phase and ammonium iron manganese phosphate, wherein the molar ratio of the ferromanganese phosphate in the red phosphate manganese phase to the ammonium iron manganese phosphate is 1:9-1:1.

[0042] In some preferred embodiments, the molar ratio of the ferromanganese phosphate and ammonium ferromanganese phosphate in the red phosphorus manganese ore phase is 1:9 to 4:6, for example, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 4:5, 4:6, etc.

[0043] After further research, the applicant has developed a simple preparation method that can achieve the preparation of the above-mentioned mixed-phase precursor hydrate.

[0044] Specifically, a method for preparing a lithium manganese iron phosphate precursor hydrate is provided, comprising: S1, adding solution A and ammonia solution to the synthesis kettle bottom liquid in parallel, stirring and reacting under a protective gas atmosphere, controlling the pH value of the reaction system to be 3-7 during the reaction, and obtaining a reaction slurry; the ammonium ion concentration in the synthesis kettle bottom liquid is 0.1-1.5 mol / L; the solution A is a solution prepared by raw materials including a manganese source, a divalent iron source, a phosphorus source and water; S2. The reaction slurry is subjected to solid-liquid separation, washing and drying to obtain a composite phase lithium manganese iron phosphate precursor hydrate containing crystal water.

[0045] In the above technical scheme, ammonia water is used as a precipitant, and the ratio of red phosphorus manganese ore phase ferromanganese phosphate and ammonium ferromanganese phosphate in the lithium ferromanganese phosphate precursor hydrate is regulated by controlling the conditions such as the ammonium ion concentration in the bottom liquid of the reactor. The applicant has found through research that there are large and obvious differences in the compacted density, capacity and processing performance of the lithium ferromanganese phosphate subsequently prepared using the two as raw materials. Based on this difference, the lithium ferromanganese phosphate and the precursor are optimized.

[0046] In some embodiments, in step S1, the ammonium salt is one or more of ammonium sulfate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and ammonium acetate.

[0047] In some preferred embodiments, the pH value of the synthesis kettle bottom liquid is 3-7, more preferably 4.5-6.0, for example 4.5, 4.8, 5.0, 5.2, 5.5, 5.8, 6, etc.

[0048] In some preferred embodiments, the amount of the synthesis reactor bottom liquid is 10-40% of the volume of the synthesis reactor, for example, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0049] In some embodiments, the pH value of the synthesis kettle bottom liquid is adjusted by adding an acidic solution; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0050] In some embodiments, the protective gas atmosphere is a nitrogen atmosphere or an inert atmosphere; the protective gas atmosphere is achieved by introducing a protective gas into a synthesis reactor.

[0051] In some embodiments, the concentration of the aqueous ammonia solution is 5-10 mol / L.

[0052] In some embodiments, the total molar concentration of manganese and iron in the solution A is 0.2-2.0 mol / L.

[0053] In some embodiments, in the solution A, the molar ratio of manganese to iron is 1-2, for example, 1, 1.2, 1.5, 1.8, 2, etc.

[0054] In some preferred embodiments, in the solution A, the molar amount of phosphorus is 0.9 to 1.1 times the total molar amount of manganese and iron, for example, 0.9 times, 0.92 times, 0.95 times, 0.98 times, 1.0 times, 1.02 times, 1.05 times, 1.08 times, and 1.1 times.

[0055] In some embodiments, the raw materials for preparing the solution A further include ascorbic acid; preferably, 0.2-0.8 g of ascorbic acid is added to 1 L of the solution A, for example, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g, etc.

[0056] In some preferred embodiments, the pH value of the solution A is below 3, such as 3, 2.8, 2.5, 2.2, 2, 1.8, 1.5, 1.2, 1, etc. In some embodiments, the raw materials for preparing the solution A also include an acidic solution for adjusting the pH; the acidic solution is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, and acetic acid.

[0057] In some embodiments, the divalent iron source is one or more of ferrous sulfate, a byproduct of titanium dioxide, industrial-grade ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous acetate.

[0058] In some embodiments, the manganese source is one or more of manganese sulfate, manganese chloride, manganese oxalate, and manganese acetate.

[0059] In some embodiments, the phosphorus source is one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0060] In some preferred embodiments, in step S1, the stirring speed of the reaction is controlled at 200-1200 rpm, for example, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, 1200 rpm, etc.; the reaction temperature is 40-80°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc.

[0061] In some preferred embodiments, in step S1, the pH value of the reaction system is controlled to be 4.5-6.0, for example, 4.5, 4.8, 5.0, 5.2, 5.5, 5.8, 6, etc. during the reaction.

[0062] In some preferred embodiments, in step S1, 0.05%V~0.5%V of solution A is introduced per minute, where V is the volume of the reactor, such as 0.05%V, 0.1%V, 0.15%V, 0.2%V, 0.25%V, 0.3%V, 0.35%V, 0.4%V, 0.45%V, 0.5%V, etc.; taking a 100L reactor as an example, in step S1, the feed flow rate of solution A is controlled at 50~500mL / min. The value of V can be 50L~100m 3 .

[0063] The flow rate of the protective gas can be adjusted according to the working conditions. In some implementation methods, when the reactor is 100L, in step S1, the nitrogen flow rate is controlled at 0.1-50mL / min.

[0064] In some embodiments, in step S1, the reaction endpoint is when the volume of the reaction slurry reaches 70-90% of the volume of the synthesis reactor, that is, preferably, the total feed amount is 30-80% of the volume of the synthesis reactor, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% and 80%.

[0065] The present invention also provides a lithium iron manganese phosphate precursor, which is obtained by calcining the lithium iron manganese phosphate precursor hydrate or the lithium iron manganese phosphate precursor hydrate prepared by the above-mentioned preparation method. The obtained phase is amorphous anhydrous iron phosphate or amorphous anhydrous iron phosphate and manganese pyrophosphate iron phosphate phase, and the obtained phase is different according to the different calcination temperatures.

[0066] In some preferred embodiments, the particle size D50 of the lithium manganese iron phosphate precursor is 1-30 μm, more preferably 5-20 μm; the tap density is 0.6-1.5 g / cm 3 , with a specific surface area of ​​1~10m 2 / g, more preferably 2 to 6 m 2 / g.

[0067] The calcination may adopt conventional parameters; specifically, the calcination temperature is 300-600°C, such as 300°C, 400°C, 500°C, 600°C, etc.; the calcination time is 3-6h, such as 3h, 4h, 5h, 6h, etc.

[0068] The present invention also provides lithium iron manganese phosphate, which is obtained by mixing the aforementioned lithium iron manganese phosphate precursor with a lithium source and then sintering, or by mixing the lithium iron manganese phosphate precursor prepared by the aforementioned preparation method with a lithium source and then sintering.

[0069] The present invention also provides a secondary battery, comprising the above-mentioned lithium manganese iron phosphate.

[0070] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0071] In the following embodiments: BET stands for specific surface area.

[0072] The particle size distribution was measured using a Malvern 3000 particle size analyzer.

[0073] BET is tested using a specific surface area tester, model BSD-BET400, manufactured by Best Instrument Technology (Beijing) Co., Ltd.

[0074] The tap density is tested by a tap density meter, model BT-313, manufactured by Dandong Better Instrument Co., Ltd.

[0075] The Fe element test method is redox titration.

[0076] The P element test method is the quinoline molybdenum gravimetric method. Example 1 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g per 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.4 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, and use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose SEM image is as shown below: Figure 1 As shown, the XRD pattern is Figure 2 As shown, from Figure 2 Combined with the preparation method, it can be concluded that the obtained precursor is red phosphorus manganese ore type (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O and ammonium manganese ferrophosphate type NH 4 (Mn,Fe)PO 4 ·H 2 O Two manganese ferrophosphate precursors containing crystalline water; after calculation, the molar ratio of the two phases is 2:8, and the Me / P of the obtained precursor hydrate, i.e. (Fe+Mn) / P, is 1.048 after testing.

[0077] Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain a ferromanganese phosphate precursor, the SEM image of which is as follows: Figure 3 As shown, the XRD pattern is Figure 4 As shown, from Figure 4 It can be seen that the obtained anhydrous precursor is ferromanganese phosphate, and because it shows a steamed bun peak, the crystallinity is low, so the anhydrous precursor is ferromanganese phosphate, and its particle size D50 and specific surface area are shown in Table 1.

[0078] Example 2 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.4 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, maintain the pH value in the synthesis reactor at 5.5±0.1 with solution B, and react fully until the volume of the synthesis reactor reaches 90%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Figure 5 As shown, from Figure 5 It can be concluded that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 17:83, and the Me / P of the obtained precursor hydrate is 1.041 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Figure 6 Its particle size D50 and specific surface area are shown in Table 1.

[0079] Example 3 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 10% volume of 0.4 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 90%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Figure 7 As shown, from Figure 7 It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 14:86, and the Me / P of the obtained precursor hydrate is 1.033 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Figure 8 Its particle size D50 and specific surface area are shown in Table 1.

[0080] Example 4 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.5 mol / L ammonium sulfate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig. 9 As shown, from Fig. 9It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 12:88, and the Me / P of the corresponding precursor hydrate is 1.028; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig.10 Its particle size D50 and specific surface area are shown in Table 1.

[0081] Example 5 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.1 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.11 As shown, from Fig.11 It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O-type manganese iron phosphate precursor containing crystal water; after calculation, the molar ratio of the two phases is 25:75, and the corresponding Me / P is 1.063; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig.12 Its particle size D50 and specific surface area are shown in Table 1.

[0082] Example 6 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.1 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 4.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 4.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.13 As shown, from Fig.13 It can be concluded that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 34:66, and the corresponding Me / P is 1.081; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig.14 Its particle size D50 and specific surface area are shown in Table 1.

[0083] Example 7 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 0.1 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 6.0±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 6.0±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.15 As shown, from Fig.15 It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 21:79, and the corresponding Me / P is 1.051; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig.16 Its particle size D50 and specific surface area are shown in Table 1.

[0084] Comparative Example 1 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 30% volume of 1.6 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.17 As shown, from Fig.17 It can be concluded that the precursor obtained is ammonium manganese iron phosphate type NH 4 (Mn,Fe)PO 4 ·H 2 O-containing ferromanganese phosphate precursor with crystal water, wherein the Me / P ratio of the precursor is 0.998; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig.18 Its particle size D50 and specific surface area are shown in Table 1.

[0085] Comparative Example 2 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing a 6.5 mol / L ammonia solution, filtering, and obtaining a solution B; Step S3: Add 30% volume of pure water into a 100L synthesis reactor, heat to 60°C, stir at 800rpm, introduce nitrogen for 1h, add sulfuric acid to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 70%, separate the solid and liquid, obtain a filter cake, and dry it at 120°C for 12h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.19 As shown, from Fig.19 It can be concluded that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 54:46, and the Me / P of the obtained precursor hydrate is 1.135 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400°C for 4h to obtain an amorphous ferromanganese phosphate precursor, the XRD pattern of which is as follows: Fig. 20 Its particle size D50 and specific surface area are shown in Table 1.

[0086] Example 8 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 1.5 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 1.5 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 10% volume of 0.4 mol / L diammonium phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 90%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, and the obtained precursor is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 14:86, and the Me / P of the obtained precursor hydrate is 1.035 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 500°C for 4h to obtain a precursor composed of amorphous ferromanganese phosphate + pyrophosphate manganese phase, the XRD pattern of which is as follows: Fig.21 Its particle size D50 and specific surface area are shown in Table 1.

[0087] Example 9 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 0.2 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 0.2 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 10% volume of 0.4 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 5.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 5.5±0.1, and react fully until the volume of the synthesis reactor reaches 90%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig. 22 As shown, from Fig. 22 It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 28:72, and the Me / P of the obtained precursor hydrate is 1.08 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400° C. for 4 h to obtain an amorphous ferromanganese phosphate + manganese pyrophosphate phase ferromanganese pyrophosphate precursor, whose particle size D50 and specific surface area are shown in Table 1.

[0088] Example 10 Step S1: dissolving manganese sulfate, ferrous sulfate and phosphoric acid in deionized water to prepare a solution with a total concentration of Mn and Fe of 2.0 mol / L, a molar ratio of Mn to Fe of 6:4, a molar concentration of phosphoric acid of 2.0 mol / L, adding ascorbic acid in an amount of 0.5 g of ascorbic acid to 1 L of the solution, filtering to obtain a solution A; Step S2: preparing 6.5 mol / L ammonia water, filtering, and obtaining solution B; Step S3: Add 10% volume of 0.4 mol / L ammonium dihydrogen phosphate solution into a 100L synthesis reactor, heat to 60°C, stir at 800 rpm, introduce nitrogen for 1 h, add sodium hydroxide to adjust the pH value of the solution in the synthesis reactor to 4.5±0.1, inject solution A into the synthesis reactor at a flow rate of 200 mL / min, use solution B to maintain the pH value in the synthesis reactor at 4.5±0.1, and react fully until the volume of the synthesis reactor reaches 90%, separate the solid and liquid, wash, obtain a filter cake, and dry it at 120°C for 12 h to obtain a precursor containing crystal water, whose XRD pattern is as follows: Fig.23 As shown, from Fig.23 It can be seen that the precursor obtained is red phosphorus manganese ore (Mn, Fe) 5 (PO 4 ) 2 (HPO 4 ) 2 ·4H 2 O+NH4+NH 4 (Mn,Fe)PO 4 ·H 2 O Two ferromanganese phosphate precursors containing crystal water; after calculation, the molar ratio of the two phases is 10:90, and the Me / P of the obtained precursor hydrate is 1.023 after testing; Step S4: calcining the dried ferromanganese phosphate containing crystal water at 400° C. for 4 h to obtain an amorphous ferromanganese phosphate + manganese pyrophosphate phase ferromanganese pyrophosphate precursor, whose particle size D50 and specific surface area are shown in Table 1.

[0089] The anhydrous manganese iron phosphate products prepared in each embodiment and comparative example were respectively prepared into lithium manganese iron phosphate by the following methods: According to the designed ratio, the ferromanganese phosphate, sucrose, polyethylene glycol, titanium dioxide and lithium carbonate prepared in this embodiment are accurately weighed, Li / (Mn+Fe)=1.02, the amount of sucrose added is 5% of the mass of the ferromanganese phosphate, the amount of polyethylene glycol added is 2% of the mass of the ferromanganese phosphate, and the amount of titanium dioxide added is 0.1% of the mass of the anhydrous ferromanganese phosphate precursor. After dissolving with pure water, the slurry of the mixture is sand-milled to D50=300~500nm in a sand mill (the sand-milling time of each embodiment and comparative example is shown in Table 1), spray granulation, and the sprayed particles are sintered at 700~750°C and crushed to obtain lithium ferromanganese phosphate positive electrode material.

[0090] The compaction density of the lithium manganese iron phosphate positive electrode materials obtained in various embodiments and comparative examples is shown in Table 1.

[0091] Electrochemical testing: Lithium manganese iron phosphate, PVP, and EC300J were added to NMP in a mass ratio of 8:1:1 to form a slurry, 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 at a constant current of 0.1C (i.e., a current of 0.1559mA), and then charged at a constant voltage of 4.5V to a cutoff current of 0.05mA. After standing for 5 minutes, it was discharged to 2.0V at 0.1C (0.1559mA), and the gram capacity of 0.1C discharge was recorded.

[0092] The test results are shown in Table 1. It can be seen from Table 1 that the red phosphorus manganese ore contained in the precursor containing crystal water prepared in each embodiment is within a certain range, and the anhydrous precursor after calcination to remove the crystal water has good processing performance in the subsequent preparation of lithium manganese iron phosphate (the time required for sand grinding to a specific particle size range is short), and the prepared lithium manganese iron phosphate has a high compaction density, and the assembled battery has good electrochemical performance.

[0093] Table 1 The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A lithium manganese iron phosphate precursor hydrate, characterized in that: The ferromanganese phosphate precursor hydrate comprises a mixture of ferromanganese phosphate in the pyrophosphate phase and ammonium ferromanganese phosphate, and the molar ratio of the ferromanganese phosphate in the pyrophosphate phase to the ammonium ferromanganese phosphate is 1:9 to 1:

1.

2. The lithium iron manganese phosphate precursor hydrate according to claim 1, characterized in that: The molar ratio of the ferromanganese phosphate to ammonium ferromanganese phosphate in the red phosphorus manganese ore phase is 1:9 to 4:

6.

3. A method for preparing lithium manganese iron phosphate precursor hydrate, characterized in that: include: S1, adding solution A and ammonia solution to the synthesis kettle bottom liquid in parallel, stirring and reacting under a protective gas atmosphere, controlling the pH value of the reaction system to be 3-7 during the reaction, and obtaining a reaction slurry; the ammonium ion concentration in the synthesis kettle bottom liquid is 0.1-1.5 mol / L; the solution A is a solution prepared by raw materials including a manganese source, a divalent iron source, a phosphorus source and water; S2. The reaction slurry is subjected to solid-liquid separation, washing and drying to obtain a composite phase lithium manganese iron phosphate precursor hydrate containing crystal water.

4. The method for preparing the lithium iron manganese phosphate precursor hydrate according to claim 3, characterized in that: In step S1, the synthesis kettle bottom liquid is prepared with ammonium salt and water as raw materials; Preferably, the pH value of the synthesis kettle bottom liquid is 3 to 7, more preferably 4.5 to 6.0; Optionally, the pH value of the synthesis kettle bottom 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; Preferably, the ammonium salt is one or more of ammonium sulfate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, and ammonium acetate; Preferably, the ammonium ion concentration in the synthesis kettle bottom liquid is 0.1-1.0 mol / L; Preferably, the amount of the synthesis reactor bottom liquid is 10-40% of the volume of the synthesis reactor.

5. The method for preparing the lithium iron manganese phosphate precursor hydrate according to claim 3 or 4, characterized in that: The concentration of the ammonia solution is 5-10 mol / L; Preferably, the pH value of the solution A is below 3; Preferably, in the solution A, the total molar concentration of manganese and iron is 0.2-2.0 mol / L; Preferably, in the solution A, the molar ratio of manganese to iron is 1 to 2; Preferably, in the solution A, the molar amount of phosphorus is 0.9 to 1.1 times the total molar amount of manganese and iron; Preferably, the preparation raw materials of the solution A also include ascorbic acid; Preferably, 0.2-0.8 g of ascorbic acid is added to 1 L of solution A.

6. The method for preparing the lithium iron manganese phosphate precursor hydrate according to any one of claims 3 to 5, characterized in that: The divalent iron source is one or more of ferrous sulfate, a byproduct of titanium dioxide, industrial-grade ferrous sulfate, ferrous chloride, ferrous oxalate, and ferrous acetate; Preferably, the manganese source is one or more of manganese sulfate, manganese chloride, manganese oxalate and manganese acetate; Preferably, the phosphorus source is one or more of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate; Preferably, the raw materials for preparing the solution A also include 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 the lithium iron manganese phosphate precursor hydrate according to any one of claims 3 to 6, characterized in that: In step S1, the stirring speed of the reaction is controlled at 200-1200 rpm; the reaction temperature is 40-80° C.; Preferably, in step S1, the pH value of the reaction system is controlled to be 4.5-6.0 during the reaction process; Preferably, the protective gas atmosphere is a nitrogen atmosphere or an inert atmosphere; the protective gas atmosphere is achieved by introducing protective gas into the synthesis reactor.

8. The method for preparing the lithium iron manganese phosphate precursor hydrate according to any one of claims 3 to 6, characterized in that: In step S1, 0.05%V~0.5%V of the solution A is introduced per minute, wherein V is the volume of the reactor; Preferably, in step S1, the reaction endpoint is when the volume of the reaction slurry reaches 70-90% of the volume of the synthesis reactor.

9. A lithium manganese iron phosphate precursor, characterized in that: The method is obtained by calcining the lithium manganese iron phosphate precursor hydrate according to claim 1 or 2 or the lithium manganese iron phosphate precursor hydrate prepared by the preparation method according to any one of claims 3 to 8.

10. The lithium iron manganese phosphate precursor according to claim 9, characterized in that: The particle size D50 of the ferromanganese phosphate precursor is 1-30 μm, and the tap density is 0.6-1.5 g / cm 3 , with a specific surface area of ​​1~10m 2 / g; Preferably, the particle size D50 of the ferromanganese phosphate precursor is 5-20 μm; Preferably, the specific surface area of ​​the ferromanganese phosphate precursor is 2 to 6 m 2 / g.

11. Lithium manganese iron phosphate, characterized in that: The lithium manganese iron phosphate precursor as claimed in claim 9 or 10 is mixed with a lithium source and then sintered to obtain the product.

12. A secondary battery, characterized in that: Comprising the lithium manganese iron phosphate as described in claim 11.

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