Manganese ferrophosphate hydrate and preparation method thereof, precursor, positive electrode material and secondary battery

Abstract

The present invention provides manganese ferrophosphate hydrate, the chemical formula of which is (Mn y Fe 1‑y )PO4·xH2O, the manganese ferrophosphate hydrate has wedge-shaped primary particles, the wedge-shaped primary particles agglomerate to form spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles agglomerate to form tertiary particles. The manganese ferrophosphate hydrate having this morphology can subsequently be used to prepare a positive electrode material with high compaction density and high specific capacity. A preparation method of the manganese ferrophosphate hydrate is also provided, which has good repeatability, simple and easy-to-regulate process, controllable (Mn+Fe) / P ratio, and is easy to realize industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials, and in particular, relates to manganese ferrophosphate hydrate with special morphology, preparation thereof, precursor, positive electrode material and application thereof. Background Art

[0002] Lithium manganese iron phosphate (LiMnxFe 1-x PO4) is a new type of phosphate lithium battery positive electrode material formed by doping a certain proportion of manganese on lithium iron phosphate (LiFePO4). On the one hand, doping can effectively combine the advantages of iron and manganese. 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 cost per watt-hour. 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 determines the performance of lithium iron manganese phosphate to a large extent. At present, there is relatively little research on ferromanganese phosphate in China.

[0005] CN112142028A discloses a method for preparing manganese phosphate, comprising taking concentrated phosphoric acid and potassium permanganate in a set ratio and mixing them evenly; reacting the mixture at a set temperature; filtering, washing and drying the reaction liquid after the reaction to obtain manganese phosphate MnPO4·H2O. The problem with this method is that potassium permanganate will introduce K impurities, the reaction temperature is 150-180°C, the reaction temperature is high, the energy consumption is high, the industrial production cost is high, and it is not easy to control its particle size.

[0006] CN114940485A discloses a method for preparing a lithium iron manganese phosphate precursor, comprising: mixing an iron source, a manganese source, a phosphorus source and water to prepare a mixed solution; heating and stirring the mixed solution, adding alkali to adjust the pH value of the solution to 1.5-5, stirring and reacting to obtain the lithium iron manganese phosphate precursor; the iron source is a trivalent iron source, and the manganese source is a trivalent manganese source. This method has at least the following problems: the trivalent manganese source and the iron source are expensive, and the trivalent manganese source is easily disproportionated after being dissolved in water to generate divalent manganese and tetravalent manganese, so the manganese iron distribution uniformity in the synthesized manganese iron phosphate precursor is poor. Summary of the invention

[0007] In response to at least one of the above technical problems, the present application provides manganese phosphate iron hydrate and its preparation method, precursor, positive electrode material, and secondary battery.

[0008] To achieve the above objectives, this application proposes the following solutions: In a first aspect, a manganese phosphate iron hydrate is provided, wherein the chemical formula of the manganese phosphate iron hydrate is (Mn y Fe 1-y )PO4·xH2O, wherein 0<y<1, 1≤x≤2, the manganese iron phosphate hydrate has wedge-shaped primary particles, the wedge-shaped primary particles are agglomerated into spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles are agglomerated into tertiary particles.

[0009] Furthermore, the manganese ferrophosphate hydrate satisfies at least one of the conditions (a) to (f): (a) In the manganese ferrophosphate hydrate, the molar ratio of manganese to iron is 1-2:1; (b) the thickness of the wedge-shaped primary particles is 10 to 50 nm; (c) the particle size of the spherical or quasi-spherical secondary particles is 300 nm to 3000 nm; (d) the tertiary particles are spherical or quasi-spherical; the particle size of the tertiary particles is 300 nm to 50 μm; (e) The tap density of the manganese ferrophosphate hydrate is 0.35-1.5 g / cm 3 ; (f) The specific surface area of ​​the manganese phosphate iron hydrate is 10 to 120 m 2 / g.

[0010] In a second aspect, a method for preparing manganese phosphate iron hydrate is provided, comprising: (1) A solution A of trivalent manganese and trivalent iron is prepared using a manganese source, an iron source, an oxidant and a chelating agent as raw materials; (2) introducing solution A, phosphorus source solution B and pH adjuster solution C into the bottom liquid of the reaction kettle in parallel, raising the temperature to 60-100° C. and stirring the reaction at this temperature to obtain a slurry; during the reaction, the pH value of the system is controlled to be 0-7; (3) The slurry is subjected to solid-liquid separation, washing and drying to obtain manganese iron phosphate hydrate.

[0011] In a third aspect, a precursor is provided, which is obtained by calcining the aforementioned manganese ferrophosphate hydrate or the manganese ferrophosphate hydrate prepared by the aforementioned preparation method to remove crystal water.

[0012] In a fourth aspect, a positive electrode material is provided, wherein the positive electrode material is lithium iron manganese phosphate or sodium iron manganese phosphate, which is obtained by mixing and sintering the aforementioned precursor with a raw material including a lithium source or a sodium source.

[0013] In a fifth aspect, a secondary battery is provided, comprising the aforementioned positive electrode material.

[0014] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: Provided is a manganese ferrophosphate hydrate with a special morphology, wherein the manganese ferrophosphate hydrate has wedge-shaped primary particles, the wedge-shaped primary particles agglomerate to form spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles agglomerate to form tertiary particles. The manganese ferrophosphate hydrate with this morphology can subsequently be used to prepare a positive electrode material with high compaction density and high specific capacity.

[0015] A method for preparing the above-mentioned manganese ferrophosphate hydrate is provided. The preparation method has good repeatability, a simple and easy-to-regulate process, a controllable (Mn+Fe) / P ratio, and is easy to realize industrial production. 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 the XRD pattern of the manganese ferrophosphate hydrate prepared in Example 1.

[0018] Figure 2 This is the SEM image of the manganese ferrophosphate hydrate prepared in Example 1.

[0019] Figure 3 This is the EDS graph of the manganese phosphate iron hydrate prepared in Example 1.

[0020] Figure 4This is the XRD pattern of the calcined and dehydrated ferromanganese phosphate prepared in Example 1.

[0021] Figure 5 This is the SEM image of the calcined and dehydrated ferromanganese phosphate prepared in Example 1.

[0022] Figure 6 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 2.

[0023] Figure 7 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 2.

[0024] Figure 8 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 3.

[0025] Fig. 9 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 3.

[0026] Fig.10 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 4.

[0027] Fig.11 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 4.

[0028] Fig.12 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 5.

[0029] Fig.13 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 5.

[0030] Fig.14 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 6.

[0031] Fig.15 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 6.

[0032] Fig.16 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 7.

[0033] Fig.17 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 7.

[0034] Fig.18 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 8.

[0035] Fig.19 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 8.

[0036] Fig. 20 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 9.

[0037] Fig.21 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 9.

[0038] Fig. 22 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 10.

[0039] Fig.23 This is the SEM image of the manganese phosphate iron hydrate prepared in Example 10.

[0040] Fig.24 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 11.

[0041] Fig.25 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 12.

[0042] Fig.26 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 13.

[0043] Fig. 27 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 14.

[0044] Fig.28 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 15.

[0045] Fig.29 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Example 16.

[0046] Fig.30 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Comparative Example 1.

[0047] Fig.31 This is the SEM image of the manganese phosphate iron hydrate prepared in Comparative Example 1.

[0048] Fig.32 This is the XRD pattern of the manganese phosphate iron hydrate prepared in Comparative Example 2.

[0049] Fig.33 This is the SEM image of the manganese phosphate iron hydrate prepared in Comparative Example 2. DETAILED DESCRIPTION

[0050] After research, the applicant has developed a manganese phosphate iron hydrate having wedge-shaped primary particles, wedge-shaped primary particles agglomerated into spherical or quasi-spherical secondary particles, and spherical or quasi-spherical secondary particles agglomerated into tertiary particles. The hydrate can be used to prepare positive electrode materials with high compaction density and capacity. Based on this, the present invention has been completed.

[0051] The present invention provides manganese ferrophosphate hydrate, wherein the chemical formula of the manganese ferrophosphate hydrate is (Mn y Fe1-y )PO4·xH2O, wherein 0<y<1, 1≤x≤2, the manganese iron phosphate hydrate has wedge-shaped primary particles, the wedge-shaped primary particles are agglomerated into spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles are agglomerated into tertiary particles.

[0052] In some preferred embodiments, in the manganese ferrophosphate hydrate, the molar ratio of manganese to iron is 1-2:1, for example, 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, etc.

[0053] In some preferred embodiments, the thickness of the wedge-shaped primary particles is 10-50 nm.

[0054] In some preferred embodiments, the length and width of the wedge-shaped primary particles are independently in the range of 100 to 800 nm, where the length and width refer to the length and width of the primary particles.

[0055] In some preferred embodiments, the particle size of the spherical or quasi-spherical secondary particles is 300 nm to 3000 nm.

[0056] In some preferred embodiments, the tertiary particles are spherical or quasi-spherical; the particle size of the tertiary particles is 300 nm to 50 μm, the particle size of the tertiary particles is Dmin=0.3 to 3 μm, and D100=9 to 50 μm.

[0057] In some preferred embodiments, the tap density of the manganese ferrophosphate hydrate is 0.35-1.5 g / cm 3 .

[0058] In some preferred embodiments, the specific surface area of ​​the manganese phosphate iron hydrate is 10 to 120 m 2 / g. Some embodiments provide a method for preparing manganese ferrophosphate hydrate, comprising: (1) preparing a mixed metal solution using a manganese source and an iron source as raw materials, adding an oxidant and a complexing agent to the mixed metal solution, filtering, and obtaining a solution A of trivalent manganese and trivalent iron; (2) introducing solution A, phosphorus source solution B and pH adjuster solution C into the bottom liquid of the reaction kettle in parallel, raising the temperature to 60-100° C. and stirring the reaction at this temperature to obtain a slurry; during the reaction, the pH value of the system is controlled to be 0-7; (3) The slurry is subjected to solid-liquid separation, washing and drying to obtain manganese iron phosphate hydrate (Mn,Fe)PO4·xH2O, wherein x is 1-2.

[0059] In the existing preparation method of ferromanganese phosphate, since trivalent manganese cannot exist stably in the solution, it is very easy to undergo disproportionation reaction, resulting in manganese oxide precipitation and forming heterogeneous precipitation. In addition, the Ksp difference between FePO4 and MnPO4 is large, and (Mn,Fe)PO4 is difficult to precipitate in the form of solid solution after uniform co-precipitation, and it is also easy to form heterogeneous precipitation.

[0060] The above preparation method can prepare a manganese iron phosphate hydrate with a special morphology, and the hydrate can be used as a raw material to prepare a positive electrode material with high compaction density and capacity; and the above method adopts the method of mixing ferromanganese first, oxidizing and complexing, and then feeding solution A, phosphorus source solution B and pH regulator solution C in parallel, and setting the process parameters of the synthesis reactor to a range in which trivalent ferromanganese can be completely precipitated, so as to ensure that ferromanganese can be evenly distributed in all micro-areas; the co-precipitation effect of manganese and iron in the prepared manganese iron phosphate hydrate is better, so that the distribution of ferromanganese elements is more uniform. And because the ferromanganese complex oxidation solution, pH regulator and phosphorus source solution are fed in parallel, the process is easy to control and has good repeatability.

[0061] In some preferred embodiments, the complexing agent is at least one of sodium pyrophosphate, potassium pyrophosphate, pyrophosphoric acid, phosphoric acid, diammonium phosphate, diammonium hydrogen phosphate, ammonium phosphate, DFOB, desferricoprogen, acetohydroxamic, 2,5-dihydroxamic acid and 3,4-dihydroxamic acid, EDTA, disodium EDTA, triphenylphosphine, sodium citrate, ammonium citrate, potassium citrate, oxalic acid, acetic acid, and lactic acid.

[0062] In some preferred embodiments, the amount of the complexing agent is 50% to 300% of the molar amount of the manganese source, such as 50%, 80%, 100%, 120%, 150%, 180%, 200%, 220%, 250%, 280%, 300%, etc. Since trivalent manganese ions are unstable in solution, their stability in solution can be enhanced by adjusting the amount ratio of the complexing agent to the manganese source.

[0063] In some preferred embodiments, the amount of the oxidant is 110-150% of the theoretical amount required to oxidize the manganese and iron in solution A into trivalent manganese and trivalent iron, for example, 110%, 120%, 130%, 140%, 150%, etc.

[0064] In the above preparation method, by accurately controlling the amount of oxidant, the manganese ions in the solution are all trivalent manganese in an oxidizing environment, and by accurately controlling the amount of complexing agent, the trivalent manganese ions can be stably present in the solution, thereby avoiding the formation of Mn 3+Disproportionation reaction produces Mn 2+ and Mn 4+ , and also avoids Mn 3+ Reduced to form Mn 2+ The process of metal source complex oxidation solution, pH regulator solution, and phosphorus source solution co-flowing and the control of synthesis temperature are adopted to make Mn 3+ with Fe 3+ Quickly with PO4 3- Co-precipitation generates (Mn,Fe)PO4·H2O, but FePO4·2H2O and MnPO4·H2O are not generated separately, and other impurities such as Fe2(NH4OH)(PO4)2·2H2O (octahedral in shape) and NH4MnPO4·H2O (lamellar in shape) are not generated. The size of the wedge-shaped primary particles can be directional controlled by adjusting the pH value and the flow rate of solution A, and then the size of the spherical secondary particles and the size of the tertiary particles can be adjusted. The above process parameters are closely coordinated to obtain (Mn,Fe)PO4·xH2O with uniform element distribution, where x=1~2.

[0065] In some preferred embodiments, in the solution A, the total molar concentration of manganese and iron is 0.2-2.0 mol / L, for example 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, and 2.0 mol / L.

[0066] In the solution A, the molar ratio of manganese to iron can be determined according to product requirements; in some preferred embodiments, in the solution A, the molar ratio of manganese to iron is 1-2:1, for example, 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, etc.

[0067] In some preferred embodiments, the concentration of the phosphorus source solution is 0.2~2 mol / L, for example, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, and 2.0 mol / L.

[0068] In some embodiments, the concentration of the pH adjusting agent solution can be the conventional concentration of ferromanganese phosphate synthesis, for example, 1-10 mol / L.

[0069] It should be noted that in step (1), when a manganese source and an iron source are used as raw materials to prepare a mixed metal solution, the manganese source and the iron source can be water-soluble manganese source and iron source, or can be water-insoluble manganese source and iron source, and the preparation process is a conventional process; when a water-soluble manganese source and an iron source are used as raw materials, the two can be dissolved in water and filtered to prepare a mixed metal solution A of manganese and iron; when a water-insoluble manganese source and / or iron source is used, the manganese source and the iron source can be dissolved in a conventional acid solution and filtered to prepare a mixed metal solution A of manganese and iron.

[0070] The phosphorus source solution can be prepared by conventional methods, such as dissolving the phosphorus source in deionized water and filtering to obtain the phosphorus source solution.

[0071] The pH adjuster solution can also be prepared by conventional methods, such as dissolving the pH adjuster in water and filtering to obtain the pH adjuster solution.

[0072] In some preferred embodiments, the iron source is at least one of ferrous sulfate, a by-product of titanium dioxide, industrial grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, ferrous acetate, ferrous carbonate, ferric carbonate, red iron, ferrous oxide, ferrous oxide, and elemental iron.

[0073] In some preferred embodiments, the manganese source is at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, manganese acetate, manganese carbonate, manganese dioxide, manganese tetraoxide, potassium permanganate, and elemental manganese.

[0074] In some preferred embodiments, the phosphorus source is at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium phosphate.

[0075] In some preferred embodiments, the pH adjuster is one or more of ammonia water, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and sodium hydroxide.

[0076] In some preferred embodiments, the oxidant is at least one of hydrogen peroxide, oxygen, ammonium persulfate, sodium persulfate, potassium persulfate, ozone, nitric acid, ammonium nitrate, potassium nitrate, sodium nitrate, potassium permanganate, dichromic acid, chlorine, chloric acid, hypochlorous acid, chlorous acid, perchloric acid, hypoiodous acid, metaperiodic acid, bromic acid, hypobromous acid, perbromic acid, ferrate, and fluorine.

[0077] In some preferred embodiments, in step (2), the stirring reaction temperature is 60-99°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 99°C, etc.

[0078] In some preferred embodiments, in step (2), the pH of the reaction system is controlled to be 1 to 6, more preferably 1 to 5, such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc. The pH adjustment can effectively control the product composition, thereby achieving the control of (Mn+Fe) / P in the product.

[0079] In step (2), the stirring speed of the stirring reaction can be 100~1000rpm, for example, 100rpm, 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm, etc.

[0080] In step (2), the pH value of the reaction kettle bottom liquid is 0-7, preferably 1-6, and more preferably 1-5, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, etc.; the pH of the reaction kettle bottom liquid is preferably controlled to be close to or even the same as the pH range required for the reaction process system to be controlled, which is conducive to reducing the difficulty of the reaction control process.

[0081] In step (2), the reaction kettle bottom liquid is prepared with water or water and acid. The acid can be conventional acids in the art, such as phosphoric acid, sulfuric acid, hydrochloric acid, oxalic acid, acetic acid, etc. The amount of acid used in the preparation process can be conventionally determined according to pH requirements; of course, a small amount of complexing agent, ammonium dihydrogen phosphate, nitrate and other salts corresponding to oxidizing acids can also be added to the reaction kettle bottom liquid.

[0082] In some preferred embodiments, in step (2), the flow rate of the phosphorus source solution B and the flow rate of the solution A are calculated according to the molar ratio of the phosphorus in the phosphorus source solution introduced per unit time to the total amount of metal in the solution A introduced per unit time, which is 1 to 2, for example, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc. It is worth noting that the flow rate ratio of the phosphorus source solution B to the solution A can be controlled in various ways as needed, for example, the flow rate of the phosphorus source solution B and the flow rate of the solution A can be changed and controlled synchronously; or after fixing the flow rate of the solution A or the phosphorus source solution B, the flow rate of the other raw material can be controlled according to its flow rate.

[0083] In some embodiments, in step (2), the flow rate of solution A is 0.05%V~0.5%V of solution A per minute, where V is the volume of the reactor, for example, 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 synthesis reactor for synthesis as an example, the flow rate of solution A is 50~500mL / min.

[0084] In some preferred embodiments, in step (2), during the reaction process, continuous feeding and continuous overflow discharge can also be adopted, and after the particle size D50 of the reaction slurry reaches the target range, the slurry is collected. That is, by adopting a continuous method to prepare ferromanganese phosphate, this preparation method is conducive to stable control of particle size and improving batch stability of materials.

[0085] It should be noted that in step (2), the (Mn+Fe) / P in the final product can be regulated by adjusting the pH value and the molar flow ratio of the phosphorus source solution B to the solution A. Specifically, the higher the pH value, the higher the (Mn+Fe) / P of the final product. The higher the molar flow ratio of the solution A to the solution B, the higher the (Mn+Fe) / P of the final product.

[0086] It should be noted that step (3) may also include other conventional steps, such as screening after drying as required.

[0087] It should be noted that in step (3), solid-liquid separation can be achieved by conventional methods such as centrifugation or filter pressing in the art; washing and drying can also be conventional washing and drying methods; for example, drying can be the most common drying method, and the drying temperature can also be a conventional drying temperature in the art, such as 90-150°C.

[0088] The present invention also provides a precursor, which is obtained by calcining the aforementioned ferromanganese phosphate hydrate or the ferromanganese phosphate hydrate prepared by the aforementioned preparation method to remove crystal water, and the precursor is an anhydrous compound. The precursor inherits the morphological characteristics of the ferromanganese phosphate hydrate, has wedge-shaped primary particles, the wedge-shaped primary particles agglomerate to form spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles agglomerate to form tertiary particles.

[0089] It should be noted that in step (4), the calcination is a conventional calcination process in the art, as long as the crystal water can be removed. For example, the calcination temperature can be 400-600° C., and the calcination time can be determined according to needs.

[0090] The present invention also provides a positive electrode material, which is lithium iron manganese phosphate or sodium iron manganese phosphate, and is obtained by mixing and sintering the aforementioned precursor with a raw material including a lithium source or a sodium source.

[0091] In addition to the lithium source or sodium 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, for lithium manganese iron phosphate, manganese iron phosphate, sucrose, polyethylene glycol, titanium dioxide (or other doping element compounds), 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 the lithium manganese iron phosphate positive electrode material.

[0092] The compacted density of the obtained lithium manganese iron phosphate is 2.2~2.5g / cm 3 Between, preferably 2.3~2.5g / cm 3 , for example 2.3 g / cm 3 , 2.32g / cm 3 , 2.35g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.42g / cm 3 , 2.45g / cm 3 , 2.48g / cm 3 , 2.5g / cm 3 etc., with a specific surface area of ​​14~24m 2 / g, the assembled battery 0.1C gram capacity is 145~160mAh / g.

[0093] The present invention also provides a secondary battery, comprising the above-mentioned positive electrode material.

[0094] 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.

[0095] In the following embodiments and comparative examples, the detection methods or instruments of the products are as follows: Particle size distribution detection: Malvern 3000 particle size analyzer.

[0096] BET test: specific surface area tester, model BSD-BET400, manufacturer is Best Instrument Technology (Beijing) Co., Ltd.

[0097] Tap density test: Tap density meter, model BT-313, manufacturer is Dandong Better Instrument Co., Ltd.

[0098] Mn, Fe, P element content detection method: ICP.

[0099] Example 1 Step S1, dissolving manganese sulfate and ferrous sulfate, an oxidant ammonium persulfate, and a complexing agent sodium pyrophosphate in deionized water, filtering, and obtaining a trivalent manganese ferrous sulfate solution A, wherein the solution concentration is 0.9 mol / L Mn concentration, 0.6 mol / L Fe total concentration, 0.9 mol / L oxidant ammonium persulfate concentration, and 1.08 mol / L complexing agent sodium pyrophosphate; Step S2, dissolving ammonium dihydrogen phosphate in deionized water, filtering to obtain solution B (phosphorus source solution), the concentration of solution B is 2 mol / L; preparing ammonia water as a pH adjuster, filtering to obtain solution C (pH adjuster), the solution concentration is 6.5 mol / L; Step S3, using pure water as the base liquid, adding sulfuric acid to adjust the pH value of the base liquid to 3.0, heating to 85°C, stirring at a stirring speed of 400 rpm, feeding solutions A, B, and C into a 100 L reactor in parallel, fixing the flow rate of solution A at 100 mL / min, and the flow rate of solution B so that (Mn+Fe) / P in the feed per unit time is 1 / 1.2, and stabilizing the pH value of the system to 3.0 by using pH regulator C; Step S4, cooling the obtained slurry and centrifuging or filtering to achieve solid-liquid separation, drying the solid at 120°C, and sieving to obtain (Mn,Fe)PO4·xH2O. The XRD pattern of (Mn,Fe)PO4·xH2O is as follows: Figure 1 As shown, from Figure 1 It can be seen that it is pure phase MnPO4·H2O, and the crystals are relatively intact; the SEM picture is as follows Figure 2 As shown, from Figure 2 It can be seen that the primary particles are wedge-shaped, with a length and width ranging from 300 to 400 nm and a thickness ranging from 30 to 50 nm. The secondary particles are spherical, with a particle size ranging from 300 nm to 1000 nm. The tertiary particles are quasi-spherical, with a particle size ranging from 300 nm to 50 μm. After testing, the tap density of the obtained hydrate is 1.00 g / cm 3 , with a specific surface area of ​​30m 2 / g; EDS diagram of hydrate is as follows Figure 3 As shown, from Figure 3 It can be seen that the distribution of Mn and Fe in the hydrate is uniform, proving that uniform co-precipitation of Mn and Fe is achieved; the element content of the hydrate is detected, the molar ratio of Mn / Fe is 1.474, and the molar ratio of (Mn+Fe) / P is 0.987.

[0100] Step S5, calcining the obtained (Mn,Fe)PO4·xH2O at 400°C for 4h to remove crystal water to obtain ferromanganese phosphate. The XRD pattern of the obtained ferromanganese phosphate is as follows: Figure 4 As shown, from Figure 4It can be seen that the phase result is Mn2P2O7+(Fe,Mn)3(PO4)2(OH)2, and the main active component of the intermediate phase is ferromanganese phosphate; the SEM image of the obtained ferromanganese phosphate is as follows Figure 5 As shown, from Figure 5 It can be seen that the morphology of the anhydrous compound and the hydrate is not much different.

[0101] 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 ferromanganese phosphate. After dissolving with pure water, the slurry of the mixture 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 lithium ferromanganese phosphate positive electrode material.

[0102] The compacted density of the obtained lithium manganese iron phosphate is 2.40g / cm 3 The specific surface area is 19m 2 / g.

[0103] Battery assembly method: Add lithium manganese iron phosphate, PVP, and EC300J to NMP in a ratio of 8:1:1 to form a slurry, evenly apply it on aluminum foil, dry it at 90°C, and obtain the positive electrode sheet after punching. Assemble the button battery in the order of positive electrode sheet, electrolyte, diaphragm, electrolyte, lithium sheet, gasket, and shrapnel. After standing for 24 hours, first use 0.1C (i.e., 0.1559mA) constant current to charge to 4.5V, then charge at 4.5V constant voltage to a cutoff current of 0.05mA, stand for 5 minutes, and discharge at 0.1C (0.1559mA) to 2.0V, and record the 0.1C discharge gram capacity.

[0104] The first discharge capacity of the assembled battery at 0.1C is 152 mAh / g.

[0105] Example 2 The only difference between this embodiment and embodiment 1 is that in step S3, the flow rate of solution A is different, and the flow rate of solution A is 50 mL / min.

[0106] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Figure 6 The SEM image of the obtained manganese phosphate iron hydrate is shown in Figure 7 shown.

[0107] The manganese iron phosphate prepared in this example was used as a raw material, and lithium manganese iron phosphate was prepared by the same preparation method as in Example 1.

[0108] The compacted density of the obtained lithium manganese iron phosphate is 2.36g / cm 3 , with a specific surface area of ​​17.39m 2 / g.

[0109] The battery was assembled in the same manner as in Example 1. The first discharge capacity of the assembled battery at 0.1C was 148 mAh / g.

[0110] Example 3 The only difference between this embodiment and embodiment 1 is that in step S3, the flow rate of solution A is different, and the flow rate of solution A is 500 mL / min.

[0111] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Figure 8 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig. 9 shown.

[0112] The manganese iron phosphate prepared in this example was used as a raw material, and lithium manganese iron phosphate was prepared by the same preparation method as in Example 1.

[0113] The compacted density of the obtained lithium manganese iron phosphate is 2.35g / cm 3 , with a specific surface area of ​​18.14m 2 / g.

[0114] The battery was assembled in the same manner as in Example 1. The first discharge capacity of the assembled battery at 0.1C was 146 mAh / g.

[0115] Example 4 The difference between this embodiment and embodiment 1 is that in step S3, the reaction temperature is different, and the temperature is raised to 60° C. for reaction.

[0116] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.10 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.11 shown.

[0117] Example 5 The difference between this embodiment and embodiment 1 is that in step S3, the reaction temperature is different, and the temperature is raised to 95° C. for reaction.

[0118] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.12 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.13 shown.

[0119] Example 6 The difference between this embodiment and embodiment 1 is only that step S3 is different. In step S3, pure water is used as the base liquid, sulfuric acid is added to adjust the pH value of the base liquid to 1.0, the temperature is raised to 85°C, and the stirring speed is 400 rpm. Solutions A, B, and C are fed into a 100L reactor in parallel, the flow rate of solution A is fixed at 100 mL / min, and the flow rate of solution B is such that (Mn+Fe) / P in the feed per unit time is 1 / 1.2, and the pH value of the system is stabilized to 1.0 by pH regulator C.

[0120] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.14 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.15 shown.

[0121] Example 7 The difference between this embodiment and embodiment 1 is only that step S3 is different. In step S3, pure water is used as the base liquid, sulfuric acid is added to adjust the pH value of the base liquid to 5.0, the temperature is raised to 85°C, and the stirring speed is 400 rpm. Solutions A, B, and C are fed into a 100L reactor in parallel, the flow rate of solution A is fixed at 100 mL / min, and the flow rate of solution B is such that (Mn+Fe) / P in the feed per unit time is 1 / 1.2, and the pH value of the system is stabilized to 5.0 by pH regulator C.

[0122] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.16 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.17 shown.

[0123] Example 8 The difference between this embodiment and embodiment 1 is only that step S3 is different. In step S3, pure water is used as the base liquid, sulfuric acid is added to adjust the pH value of the base liquid to 7.0, the temperature is raised to 85°C, and the stirring speed is 400 rpm. Solutions A, B, and C are fed into a 100L reactor in parallel, the flow rate of solution A is fixed at 100 mL / min, and the flow rate of solution B is such that (Mn+Fe) / P in the feed per unit time is 1 / 1.2, and the pH value of the system is stabilized to 7.0 by pH regulator C.

[0124] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.18 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.19 shown.

[0125] Example 9 The only difference between this embodiment and embodiment 1 is that in step S1, the type of complexing agent is different, and the complexing agent is phosphoric acid.

[0126] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig. 20The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.21 shown.

[0127] Example 10 The only difference between this embodiment and embodiment 1 is that in step S1, the type of complexing agent is different, and the complexing agent is oxalic acid.

[0128] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig. 22 The SEM image of the obtained manganese phosphate iron hydrate is shown in Fig.23 shown.

[0129] Embodiment 11 The difference between this embodiment and embodiment 1 is that step S1 is different. In step S1, manganese sulfate and ferrous sulfate, oxidant ammonium persulfate, and complexing agent sodium pyrophosphate are dissolved in deionized water, filtered, and trivalent manganese ferrous sulfate solution A is obtained, wherein the solution concentration is 0.9 mol / L of Mn concentration, 0.6 mol / L of total Fe concentration, 0.9 mol / L of oxidant ammonium persulfate concentration, and 0.45 mol / L of complexing agent sodium pyrophosphate.

[0130] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.24 shown.

[0131] Example 12 The difference between this embodiment and embodiment 1 is that step S1 is different. In step S1, manganese sulfate and ferrous sulfate, oxidant ammonium persulfate, and complexing agent sodium pyrophosphate are dissolved in deionized water, filtered, and trivalent manganese ferrous sulfate solution A is obtained, wherein the solution concentration is 0.9 mol / L of Mn concentration, 0.6 mol / L of total Fe concentration, 0.9 mol / L of oxidant ammonium persulfate concentration, and 2.7 mol / L of complexing agent sodium pyrophosphate.

[0132] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.25 shown.

[0133] Embodiment 13 The difference between this embodiment and embodiment 1 is that step S1 is different. In step S1, manganese sulfate and ferrous sulfate, oxidant ammonium persulfate, and complexing agent sodium pyrophosphate are dissolved in deionized water, filtered, and trivalent manganese ferrous sulfate solution A is obtained, wherein the solution concentration is 0.9 mol / L of Mn concentration, 0.6 mol / L of total Fe concentration, 0.825 mol / L of oxidant ammonium persulfate concentration, and 1.08 mol / L of complexing agent sodium pyrophosphate.

[0134] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.26 shown.

[0135] Embodiment 14 The difference between this embodiment and embodiment 1 is that step S1 is different. In step S1, manganese sulfate and ferrous sulfate, oxidant ammonium persulfate, and complexing agent sodium pyrophosphate are dissolved in deionized water, filtered, and trivalent manganese ferrous sulfate solution A is obtained, wherein the solution concentration is 0.9 mol / L of Mn concentration, 0.6 mol / L of total Fe concentration, 1.125 mol / L of oxidant ammonium persulfate concentration, and 1.08 mol / L of complexing agent sodium pyrophosphate.

[0136] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig. 27 shown.

[0137] Embodiment 15 Step S3, using pure water as the base liquid, adding sulfuric acid to adjust the pH value of the base liquid to 3.0, heating to 85°C, stirring at a stirring speed of 400 rpm, feeding solutions A, B, and C in parallel, fixing the flow rate of solution A at 100 mL / min, and the flow rate of solution B so that (Mn+Fe) / P in the feed per unit time is 1, and the pH value of the system is stabilized to 3.0 by pH regulator C.

[0138] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.28 shown.

[0139] Example 16 Step S3, using pure water as the base liquid, adding sulfuric acid to adjust the pH value of the base liquid to 3.0, heating to 85°C, stirring at a stirring speed of 400 rpm, feeding solutions A, B, and C in parallel, fixing the flow rate of solution A at 100 mL / min, and the flow rate of solution B so that (Mn+Fe) / P in the feed per unit time is 1 / 2, and the pH value of the system is stabilized to 3.0 by pH regulator C.

[0140] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.29 shown.

[0141] Comparative Example 1 The only difference between this comparative example and Example 1 is that in step S3, the temperature is raised to 50°C for reaction.

[0142] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.30 As shown in the SEM images Fig.31 shown.

[0143] The manganese iron phosphate prepared in this comparative example was used as a raw material, and lithium manganese iron phosphate was prepared by the same preparation method as in Example 1.

[0144] The compacted density of the obtained lithium manganese iron phosphate is 2.10g / cm 3 , with a specific surface area of ​​23.55m 2 / g.

[0145] The battery was assembled in the same manner as in Example 1. The first discharge capacity of the assembled battery at 0.1C was 134 mAh / g.

[0146] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S3, the pH value of the system is stabilized to 8 by the pH adjuster C.

[0147] The XRD pattern of the obtained manganese iron phosphate hydrate is as follows: Fig.32 As shown in the SEM images Fig.33 shown.

[0148] The manganese iron phosphate prepared in this comparative example was used as a raw material, and lithium manganese iron phosphate was prepared by the same preparation method as in Example 1.

[0149] The compacted density of the obtained lithium manganese iron phosphate is 2.23g / cm 3 , the specific surface area is 24.56m 2 / g.

[0150] The battery was assembled in the same manner as in Example 1. The first discharge capacity of the assembled battery at 0.1C was 138 mAh / g.

[0151] It can be seen from the SEM images of the manganese ferrophosphate hydrate prepared in each embodiment that the morphology of the manganese ferrophosphate hydrate prepared in each embodiment of the present invention has wedge-shaped primary particles, the wedge-shaped primary particles are agglomerated into spherical or quasi-spherical secondary particles, the spherical or quasi-spherical secondary particles are agglomerated into tertiary particles, and the primary particles, secondary particles and tertiary particles of the obtained manganese ferrophosphate hydrate The size, tap density, specific surface area and Me / P molar ratio (wherein Me is the total amount of Fe and Mn) are as shown in Table 1. Compared with the morphology of the manganese iron phosphate hydrate prepared in each embodiment, it is found that the SEM images of the manganese iron phosphate hydrate prepared in Comparative Examples 1 and 2 show that the morphology has changed, and it is impossible to synthesize manganese iron phosphate with similar morphology in each embodiment. In addition, compared with the manganese iron lithium phosphate prepared in Examples 1 to 3 and the manganese iron lithium phosphate prepared in Comparative Examples 1 to 2, it can be found that the compaction density of the manganese iron lithium phosphate prepared in Examples 1 to 3 is higher. Comparing the performance of the battery assembled with the manganese iron lithium phosphate prepared in Examples 1 to 3 and the manganese iron lithium phosphate prepared in Comparative Examples 1 to 2, it can be found that the discharge specific capacity of the battery assembled with the manganese iron lithium phosphate prepared in Examples 1 to 3 is higher.

[0152] 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. Manganese iron phosphate hydrate, characterized in that The chemical formula of the manganese ferrophosphate hydrate is (Mn y Fe 1-y )PO4·xH2O, wherein 0<y<1, 1≤x≤2, the manganese iron phosphate hydrate has wedge-shaped primary particles, the wedge-shaped primary particles are agglomerated into spherical or quasi-spherical secondary particles, and the spherical or quasi-spherical secondary particles are agglomerated into tertiary particles.

2. The manganese ferrophosphate hydrate according to claim 1, characterized in that The manganese ferrophosphate hydrate satisfies at least one of the conditions (a) to (f): (a) In the manganese ferrophosphate hydrate, the molar ratio of manganese to iron is 1-2:1; (b) the thickness of the wedge-shaped primary particles is 10 to 50 nm; (c) the particle size of the spherical or quasi-spherical secondary particles is 300 nm to 3000 nm; (d) the tertiary particles are spherical or quasi-spherical; the particle size of the tertiary particles is 300 nm to 50 μm; (e) The tap density of the manganese ferrophosphate hydrate is 0.35-1.5 g / cm 3 ; (f) The specific surface area of ​​the manganese phosphate iron hydrate is 10 to 120 m 2 / g.

3. A method for preparing manganese ferrophosphate hydrate, characterized in that: include: (1) A solution A of trivalent manganese and trivalent iron is prepared using a manganese source, an iron source, an oxidant and a chelating agent as raw materials; (2) introducing solution A, phosphorus source solution B and pH adjuster solution C into the bottom liquid of the reaction kettle in parallel, raising the temperature to 60-100° C. and stirring the reaction at this temperature to obtain a slurry; during the reaction, the pH value of the reaction system is controlled to be 0-7; (3) The slurry is subjected to solid-liquid separation, washing and drying to obtain manganese iron phosphate hydrate.

4. The method for preparing manganese ferrophosphate hydrate according to claim 3, characterized in that: The complexing agent is at least one of sodium pyrophosphate, potassium pyrophosphate, pyrophosphoric acid, phosphoric acid, diammonium phosphate, diammonium hydrogen phosphate, ammonium phosphate, DFOB, desferrioxine, acetic acid hydroxylamine, 2,5-diacylhydroxamic acid and 3,4-diacylhydroxamic acid, EDTA, disodium EDTA, triphenylphosphine, sodium citrate, ammonium citrate, potassium citrate, oxalic acid, acetic acid, and lactic acid.

5. The method for preparing manganese ferrophosphate hydrate according to claim 3 or 4, characterized in that: 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 1-2:1; Preferably, when preparing solution A, the amount of the oxidant is 110-150% of the theoretical amount required to oxidize manganese and iron in solution A into trivalent manganese and trivalent iron; Preferably, when preparing solution A, the amount of the complexing agent used is 50% to 300% of the molar amount of the manganese source.

6. The method for preparing manganese ferrophosphate hydrate according to any one of claims 3 to 5, characterized in that: The iron source is at least one of ferrous sulfate, a byproduct of titanium dioxide, industrial-grade ferrous sulfate, ferrous nitrate, ferrous chloride, ferrous oxalate, ferrous acetate, ferrous carbonate, ferric carbonate, iron red, ferrous oxide, ferroferric oxide, and elemental iron; Preferably, the manganese source is at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, manganese acetate, manganese carbonate, manganese dioxide, manganese tetraoxide, elemental manganese, and potassium permanganate; Preferably, the phosphorus source is at least one of phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium phosphate; Preferably, the pH regulator is one or more of ammonia water, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and sodium hydroxide; Preferably, the oxidant is at least one of hydrogen peroxide, oxygen, ammonium persulfate, sodium persulfate, potassium persulfate, ozone, nitric acid, ammonium nitrate, potassium nitrate, sodium nitrate, potassium permanganate, dichromic acid, chlorine, chloric acid, hypochlorous acid, chlorous acid, perchloric acid, hypoiodous acid, metaperiodic acid, bromic acid, hypobromous acid, perbromic acid, ferrate, and fluorine.

7. The method for preparing manganese ferrophosphate hydrate according to any one of claims 3 to 6, characterized in that: The pH value of the reaction kettle bottom liquid is 0-7, preferably 1-6; Preferably, the concentration of the phosphorus source solution is 0.2-2 mol / L; Preferably, the concentration of the pH adjuster solution is 1-10 mol / L.

8. The method for preparing manganese ferrophosphate hydrate according to any one of claims 3 to 7, characterized in that: In step (2), the temperature is raised to 70-99° C. and stirred for reaction at this temperature; Preferably, in step (2), the pH of the reaction system is controlled to be 1 to 6, more preferably 1 to 5 during the reaction; Preferably, in step (2), the stirring speed of the stirring reaction is 100-1000 rpm.

9. The method for preparing manganese phosphate iron hydrate according to any one of claims 3 to 8, characterized in that: In step (2), the flow rate of the phosphorus source solution B and the flow rate of the solution A are calculated based on the molar ratio of phosphorus in the phosphorus source solution introduced per unit time to the total amount of metal in the solution A introduced per unit time being 1 to 2; In step (2), the flow rate of solution A is 0.05%V~0.5%V of solution A per minute, where V is the volume of the reactor.

10. The method for preparing manganese ferrophosphate hydrate according to any one of claims 3 to 9, characterized in that: In step (2), during the reaction process, the feed is continuously fed and the overflow is continuously discharged, and after the particle size D50 of the reaction slurry reaches the target range, the slurry is collected.

11. A precursor, characterized in that The ferromanganese phosphate hydrate is obtained by calcining the ferromanganese phosphate hydrate according to claim 1 or 2 or the ferromanganese phosphate hydrate prepared by the preparation method according to any one of claims 3 to 10 to remove crystal water.

12. A positive electrode material, wherein the positive electrode material is lithium iron manganese phosphate or sodium iron manganese phosphate, characterized in that: The precursor according to claim 11 is mixed with raw materials including a lithium source or a sodium source and sintered to obtain the product.

13. A secondary battery, characterized in that: Comprising the positive electrode material as claimed in claim 12.

Images