Lithium manganese iron phosphate as well as preparation method and application thereof

Abstract

The invention provides lithium manganese iron phosphate as well as a preparation method and application thereof, and relates to the technical field of lithium ion batteries. Specifically, the method comprises the following steps: preparing a solution containing an iron source, a manganese source and ammonium oxalate, adjusting the pH value to be acidic, and carrying out a water bath reaction on the solution in a sealed state; after the reaction, sequentially carrying out aging, solid-liquid separation and drying to obtain Fe < 1-x > Mn < x > C < 2 > O < 4 >. 2H < 2 > O; preparing a mixed solution containing Fe < 1-x > Mn < x > C < 2 > O < 4 >. 2H < 2 > O, a lithium source, a phosphorus source and a carbon source, and sequentially performing wet ball milling, spray drying and calcination to obtain the lithium manganese iron phosphate. According to the preparation method, the manganese iron oxalate precursor is synthesized in advance, so that uniform mixing of iron and manganese on an atomic level can be realized, and the lithium manganese iron phosphate positive electrode material with high electrochemical performance is prepared; and the preparation method is simple in preparation process and low in cost, and has a good batch production prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to lithium manganese iron phosphate and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, light weight, no memory effect, long cycle life, and no pollution. They have been widely used in portable electronic devices such as mobile phones, laptops, and small cameras, as well as submarines, aviation, aerospace, electric vehicles, and large-scale energy storage. As a positive electrode material for lithium-ion batteries, lithium manganese iron phosphate has a discharge platform of up to 4.1V, and its theoretical energy density is 15% to 20% higher than that of lithium iron phosphate. Its olivine structure makes it less likely to collapse during the charge and discharge process, and its capacity retention rate can still be maintained at more than 75% in low temperature environments. It is considered to be the next generation of positive electrode materials that are expected to replace lithium iron phosphate and achieve commercial applications.

[0003] At present, the methods for preparing lithium iron manganese phosphate mainly include high-temperature solid-phase method, hydrothermal method and co-precipitation method. Among them, the high-temperature solid-phase method mostly uses iron source, manganese source, phosphorus source, lithium source and carbon source to mix, and synthesize lithium iron manganese phosphate through processes such as sand milling, spray drying and sintering; the high-temperature solid-phase method can make the raw materials fully react at high temperature and form a relatively pure lithium iron manganese phosphate powder, and the powder particles are evenly distributed, with less agglomeration. At the same time, the equipment requirements are low and the operation is simple. Compared with the hydrothermal method or co-precipitation method, it is more suitable for industrial production. However, this method cannot achieve uniform mixing of iron and manganese at the atomic level during the sand milling process, resulting in the prepared lithium iron manganese phosphate having poor constant voltage charging performance and rate discharge performance.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first purpose of the present invention is to provide a method for preparing lithium iron manganese phosphate, which is mainly used to solve the problem that the conventional high-temperature solid-phase method in industrial mass applications cannot achieve uniform mixing of iron and manganese at the atomic level when preparing lithium iron manganese phosphate positive electrode materials, resulting in the prepared lithium iron manganese phosphate positive electrode materials not having excellent constant voltage charging performance and rate discharge performance.

[0006] The second object of the present invention is to provide a lithium manganese iron phosphate, which has excellent constant voltage charging performance and rate discharge performance when used as a positive electrode material for a lithium ion battery.

[0007] A third object of the present invention is to provide a lithium ion battery.

[0008] A fourth object of the present invention is to provide an electrical device.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] A method for preparing lithium manganese iron phosphate mainly comprises the following steps:

[0011] A solution containing an iron source, a manganese source and ammonium oxalate is prepared, and after adjusting the pH to acidic, the solution is subjected to a water bath reaction in a sealed state; after the reaction, aging, solid-liquid separation and drying are performed in sequence to obtain Fe 1-x Mn x C2O4·2H2O,0 <x<1;

[0012] Configuration includes Fe 1-x Mn x A mixed solution of C2O4·2H2O, a lithium source, a phosphorus source and a carbon source is sequentially subjected to wet ball milling, spray drying and calcination to obtain lithium manganese iron phosphate.

[0013] A lithium iron manganese phosphate positive electrode material is prepared by adopting the preparation method of lithium iron manganese phosphate.

[0014] A lithium ion battery comprises the lithium iron manganese phosphate positive electrode material.

[0015] An electrical device comprises the lithium-ion battery.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention provides a preparation process of lithium iron manganese phosphate, wherein an acidic reaction solution is prepared with an iron source, a manganese source and ammonium oxalate, a dihydrated manganese iron oxalate coprecipitation precursor is obtained by adjusting pH, reacting in a sealed water bath and post-processing, and the precursor is used as a manganese iron source and mixed with a lithium source, a phosphorus source and a carbon source, and then a lithium iron manganese phosphate positive electrode material is further prepared by a high-temperature solid phase method. The preparation process of the present invention is simple to operate, can be completed under normal pressure, has low cost, and is very suitable for large-scale industrial production; wherein the yield of dihydrated manganese iron oxalate is close to 100%, which can greatly avoid the waste of raw materials, and can achieve uniform mixing of iron and manganese at the atomic level, and prepare a lithium iron manganese phosphate positive electrode material with high electrochemical performance.

[0018] (2) In the process steps of preparing the dihydrate oxalate manganese iron precursor of the present invention, no external reducing agent is required. The reduction effect of the oxalate group in the precursor itself can make the reduction uniform and sufficient, and can achieve uniform mixing of iron and manganese at the atomic level. Furthermore, lithium manganese iron phosphate belongs to an olivine structure. Under the ideal atomic-level uniform mixing state, the iron and manganese atoms uniformly occupy the same lattice positions and form a stable skeleton structure with the phosphate group, and the lithium ions are distributed in the channels formed by this skeleton structure; this uniform mixing is very critical to the electrochemical properties of the material and greatly contributes to the improvement of the electrochemical properties of the material. For example, during the charge and discharge process, lithium ions can be smoothly embedded and removed in a uniform channel; if the atoms are unevenly distributed, it may cause inconsistent changes in the local structure, affect the diffusion kinetics of lithium ions, and thus reduce the electrochemical performance indicators such as battery capacity, rate performance and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The XRD spectrum of the lithium manganese iron phosphate material of Example 1 of the present invention is provided. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but those skilled in the art will appreciate that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be interpreted as indicating or implying relative importance.

[0022] The first aspect of the present invention is to provide a preparation method of lithium iron manganese phosphate, which is used to provide a lithium iron manganese phosphate cathode active material with good constant voltage charging performance and strong rate discharge performance; the preparation method of the present invention generally belongs to the high-temperature solid-phase method, but the raw materials and processes of the existing simple high-temperature solid-phase method are improved, and a new route for synthesizing lithium iron manganese phosphate cathode active material by the high-temperature solid-phase method is provided.

[0023] The preparation method of the present invention mainly includes the following steps: (1) Prepare a solution containing an iron source, a manganese source and ammonium oxalate, adjust the pH to acidic, and then carry out a water bath reaction on the solution in a sealed state; after the reaction, carry out aging, solid-liquid separation and drying in sequence to obtain Fe 1-x Mn x C2O4·2H2O, 0 < x < 1; (2) Prepare a mixed solution containing Fe 1-x Mn x C2O4·2H2O, a lithium source, a phosphorus source and a carbon source, and carry out wet ball milling, spray drying and calcination in sequence to obtain lithium iron manganese phosphate.

[0024] As a preferred embodiment, the iron source includes at least one of ferrous sulfate, ferrous chloride, ferrous nitrate or ferrous acetate, and optionally, pure substances of the above compounds or hydrated compounds containing crystal water can be used, such as common FeSO4·7H2O, FeCl2·4H2O, Fe(CH3COO)2·4H2O, etc.

[0025] As a preferred embodiment, the manganese source includes at least one of manganese sulfate, manganese chloride, manganese nitrate or manganese acetate, and optionally, pure substances of the above compounds or hydrated compounds containing crystal water can be used, such as common MnSO4·H2O, MnCl2·4H2O, Mn(NO3)2·4H2O, Mn(CH3COO)2·4H2O, etc.

[0026] As a preferred embodiment, in the solution, the total concentration of ferrous ions (Fe 2+ ) and manganese ions (Mn 2+ ) is 60 g / L to 90 g / L, including but not limited to any one or any numerical range composed of any two of 60, 65, 70, 75, 80, 85, 90 (g / L); it should be noted that the concentration sum provided here is the sum of the concentrations of the two metal ions, rather than the sum of the compound concentrations of the added iron source and manganese source. Those skilled in the art need to convert according to the above total concentration and the types of compounds selected to obtain the specific dosages of the added manganese source and iron source.

[0027] As a preferred embodiment, in the solution, the iron element and the manganese element are present as ferrous ions and manganese ions, respectively, and the iron-manganese ratio is 1:4 to 4:1 on a molar basis; it is understandable that those skilled in the art can adaptively select and adjust the iron-manganese ratio in the solution according to the preset iron-manganese ratio in the lithium iron manganese phosphate product.

[0028] As a preferred embodiment, the amount of ammonium oxalate added is based on the iron source and the manganese source, and an appropriate amount of oxalate ions is added to pair with ferrous ions and manganese ions to obtain Fe 1-x Mn x C2O4 precursor product, so the ratio of the sum of the molar amounts of the iron element in the iron source and the manganese element in the manganese source to the molar amount of the ammonium oxalate is 1: (1 to 1.2), more preferably 1:1.

[0029] As a preferred embodiment, during the preparation of the solution, the iron source and the manganese source are first added to water to perform a first mixing; and then the ammonium oxalate is added to perform a second mixing; the first mixing and / or the second mixing can be assisted by one or more of the following methods, such as oscillation, stirring, ultrasound, shaking, centrifugation, and heat treatment. In some more preferred embodiments, the first mixing and the second mixing are performed by stirring at a rate of 500 rpm to 1000 rpm.

[0030] As a preferred embodiment, the pH is adjusted to 3-6, including but not limited to any one of 3, 3.5, 4, 4.5, 5, 5.5, 6 or a numerical range consisting of any two of them.

[0031] As a preferred embodiment, the acid-base reagents used for pH adjustment include but are not limited to sulfuric acid, hydrochloric acid, nitric acid, ammonia water, sodium hydroxide, potassium hydroxide, etc.; in order to avoid the introduction of excessive water by the addition of acid-base reagents, high-concentration acid-base reagents are more preferably used in the present invention, and the reference concentration is 1 mol / L to 3 mol / L.

[0032] As a preferred embodiment, the temperature of the water bath reaction is 25°C to 75°C, and the time of the water bath reaction is 0.5h to 3h; in some optional embodiments, the temperature of the water bath reaction includes but is not limited to any one of 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 (°C) or a numerical range composed of any two of them, and the time of the water bath reaction includes but is not limited to any one of 0.5, 1, 1.5, 2, 2.5, 3 (h) or a numerical range composed of any two of them.

[0033] As a preferred implementation manner, the aging time is 2h to 4h.

[0034] As a preferred embodiment, the solid-liquid separation includes but is not limited to decantation, filtration, centrifugation, filter or membrane separation, etc.; in some more preferred embodiments, the solid-liquid separation in this step is carried out by suction filtration in low-yield production mode or laboratory scenario, and in large-scale batch production mode, solid-liquid separation can be carried out by filter.

[0035] As a preferred implementation, the drying temperature is 80° C. to 120° C., and the drying time is adaptively adjusted based on the absence of significant free moisture.

[0036] As a preferred embodiment, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium chloride and lithium citrate.

[0037] As a preferred embodiment, the phosphorus source includes at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, and phosphoric acid.

[0038] As a preferred embodiment, the carbon source includes at least one of sucrose, glucose, carbon black, polyethylene glycol, citric acid, and cellulose.

[0039] As a preferred embodiment, based on the molar amount of lithium in the lithium source, the molar amount of phosphorus in the phosphorus source, the sum of the molar amounts of iron in the iron source and the manganese in the manganese source, Li:P:(Fe+Mn)=(1~1.05):(1~1.05):1; simultaneously, based on the molar amount of carbon in the carbon source, C:(Fe+Mn)=(0.06~0.08):1.

[0040] As a preferred implementation, the solid content of the mixed solution is 20% to 30%.

[0041] As a preferred implementation manner, the rotation speed of the wet ball milling is 300 rpm to 600 rpm, and the time of the wet ball milling is 6 h to 12 h.

[0042] As a preferred embodiment, after the wet ball milling, the particle size of the material in the mixed liquid is D 50 It is 0.3 μm to 0.45 μm; it can be understood that those skilled in the art can adaptively adjust the process parameters of the wet ball milling based on this particle size parameter.

[0043] As a preferred embodiment, the inlet temperature of the spray drying is 200°C to 280°C, the outlet temperature is 80°C to 110°C, and the atomizer frequency is 40Hz to 60Hz.

[0044] As a preferred embodiment, the calcination is carried out in a protective gas environment, and the protective gas includes but is not limited to any one of nitrogen, hydrogen, helium, neon, argon and the like.

[0045] As a preferred embodiment, the calcination temperature is 700° C. to 850° C., and the calcination time is 8 h to 12 h.

[0046] The second aspect of the present invention is to provide a lithium manganese iron phosphate positive electrode material, which is prepared by the preparation method of lithium manganese iron phosphate as described in the first aspect.

[0047] The third aspect of the present invention is to provide a lithium-ion battery, comprising the lithium iron manganese phosphate positive electrode material as described in the second aspect.

[0048] It should be noted that the lithium-ion battery should include a positive electrode, a negative electrode, an electrolyte, a diaphragm, and other necessary or unnecessary functional elements or packaging components, etc., which can be arbitrarily selected and combined by those skilled in the art; when the lithium iron manganese phosphate positive electrode material described in the present invention is included in the lithium-ion battery, a lithium-ion battery positive electrode should be prepared based on the lithium iron manganese phosphate positive electrode material, and the positive electrode can be a lithium iron manganese phosphate positive electrode or a composite positive electrode containing lithium iron manganese phosphate; that is, whether other positive electrode active materials are used in the lithium-ion battery or not, they can be regarded as an embodiment of the present invention.

[0049] The fourth aspect of the present invention is to provide an electric device, including the lithium-ion battery as described in the third aspect. The electric device can be any device or apparatus that relies on electric energy to work or operate, including but not limited to new energy vehicles, building electrical equipment, industrial electrical appliances, household and agricultural electrical appliances, etc.; when including the lithium-ion battery, any electric device equipped with the lithium-ion battery can belong to an embodiment of the present invention.

[0050] Example 1

[0051] S1: Weigh 83.40 g FeSO4·7H2O and 50.70 g MnSO4·H2O and dissolve them in 550 mL deionized water to prepare a solution with a metal ion concentration of 60 g / L. Place the reactor containing the solution in a constant temperature water bath at 60°C and continue stirring at a rate of 600 rpm.

[0052] S2: Calculate the sum of the molar amounts of iron and manganese, and weigh ammonium oxalate at a molar ratio of 1:1 between the sum of the molar amounts of manganese and iron and ammonium oxalate; add ammonium oxalate to the above reactor, adjust the pH to 4.0 with 1 mol / L concentrated sulfuric acid and concentrated ammonia water, maintain stirring, seal the reactor, and continue the reaction at 60°C for 2 hours.

[0053] S3: After the reaction is completed, the coprecipitation filter cake is filtered and washed in sequence to obtain the coprecipitation filter cake; the coprecipitation filter cake is dried at a constant temperature of 100°C for 2h to obtain Fe 0.5 Mn 0.5 C2O4·2H2O precursor.

[0054] S4: Weigh 11.08g Li2CO3, 50.83g of the above precursor, 34.51g NH4H2PO4 and 0.60g sucrose, control the molar ratio of Li:(Fe+Mn):P to be 1:1:1, and the molar ratio of C:(Fe+Mn) to be 0.07, combine the solid phase material with 110mL deionized water and put it into a 250mL ball mill.

[0055] S5: Add zirconium balls of equal mass for ball milling, control the rotation speed to 300 rpm, and the ball milling time to 6 h, and spray dry after ball milling.

[0056] S6: The powder obtained by spray drying is calcined at 750° C. for 9 h under nitrogen protection, and then naturally cooled to room temperature to obtain lithium manganese iron phosphate LiFe 0.5 Mn 0.5 PO4 products.

[0057] like Figure 1 As shown, the XRD spectrum of lithium manganese iron phosphate of this embodiment is provided.

[0058] Furthermore, in combination with the chemical reactions performed in steps S1 to S3: MnSO4·H2O+FeSO4·7H2O+(NH4)2C2O4=Fe 1-x Mn x C2O4·2H2O+(NH4)2SO4+6H2O(x=0.5), according to the stoichiometric relationship, MnSO4·H2O, FeSO4·7H2O, Fe 1-x Mn x The stoichiometric coefficient of C2O4·2H2O is 1:1:1; for Fe 0.5 Mn 0.5 C2O4·2H2O, its molar mass M is 179.4395g / mol, while the amount of MnSO4·H2O and FeSO4·7H2O is 0.3mol. Theoretically, Fe 0.5 Mn 0.5 The amount of C2O4·2H2O is also 0.3 mol, and the theoretical value of the theoretical yield m is 0.3 mol*179.4395 g / mol=53.83 g. Correspondingly, the Fe 0.5 Mn 0.5The mass of C2O4·2H2O is 53.25 g. The yield of this embodiment is calculated to be 98.92%, which is an extremely high yield.

[0059] Example 2

[0060] The method is basically the same as Example 1, except that: in step S1, 66.72 g of FeSO4·7H2O and 60.84 g of MnSO4·H2O are weighed respectively;

[0061] Correspondingly, in step S3, Fe 0.4 Mn 0.6 C2O4·2H2O precursor, and in step S6, lithium manganese iron phosphate LiFe 0.4 Mn 0.6 PO4 products.

[0062] Example 3

[0063] It is basically the same as Example 1, except that:

[0064] S1: Prepare a solution with a metal ion concentration of 80 g / L;

[0065] S2: Calculate the sum of the molar amounts of iron and manganese, and weigh ammonium oxalate at a molar ratio of the sum of the molar amounts of manganese and iron to ammonium oxalate of 1:1.2; add ammonium oxalate to the above reactor, adjust the pH to 4.5 with 1 mol / L concentrated sulfuric acid and concentrated ammonia water, maintain stirring, seal the reactor, and continue the reaction at 40°C for 3 hours.

[0066] Example 4

[0067] It is basically the same as Example 1, except that in step S4, the molar ratio of Li:(Fe+Mn):P is controlled to be 1.05:1:1.05, and the molar ratio of C:(Fe+Mn) is controlled to be 0.08 to adjust the addition amounts of Li2CO3, NH4H2PO4 and sucrose.

[0068] Example 5

[0069] The method is basically the same as Example 1, except that in step S6, the mixture is calcined at 850° C. for 8 h under nitrogen protection.

[0070] Comparative Example

[0071] Weigh 83.40g FeSO4·7H2O, 50.70g MnSO4·H2O, 11.08g Li2CO3, 34.51g NH4H2PO4 and 0.60g sucrose, combine the above solid materials with 110mL deionized water and put them into a 250mL ball mill. Add zirconium balls of equal mass for ball milling, control the speed to 300rpm, and the ball milling time to 6h, and spray dry after ball milling. The powder obtained by spray drying is calcined at 750℃ for 9h under nitrogen protection, and then naturally cooled to room temperature to obtain lithium manganese iron phosphate LiFe 0.5 Mn 0.5 PO4 products.

[0072] Test example

[0073] The lithium iron manganese phosphate materials obtained in the above embodiments and comparative examples were used to prepare positive electrode sheets, and the method was as follows: lithium iron manganese phosphate, carbon black (Super-P) and polyvinylidene fluoride (PVDF) were uniformly dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 9:0.5:0.5 to obtain an electrode slurry; the slurry was then coated on aluminum foil, dried in a vacuum oven at 100°C for 12 hours, and cut to obtain positive electrode sheets.

[0074] Furthermore, in a glove box, each positive electrode sheet, negative electrode metal lithium sheet, polypropylene film (Celard2325) separator and 1M LiPF6 ethylene carbonate / diethyl carbonate electrolyte were assembled into CR2032 type button batteries corresponding to each embodiment and comparative example.

[0075] The above test batteries were tested in the following method: tested on LANHE CT3002A battery test system, constant current and constant voltage charging, cut-off voltage 4.5V, cut-off current 20mA; constant current discharge, cut-off voltage 2.5V; recorded and calculated the first efficiency of each battery at 0.1C and 0.2C, first efficiency = (first discharge capacity / first charge capacity) * 100%. The results are shown in Table 1.

[0076] Table 1

[0077]

[0078] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing lithium manganese iron phosphate, characterized in that: The steps include: A solution containing an iron source, a manganese source and ammonium oxalate is prepared, and after adjusting the pH to acidic, the solution is subjected to a water bath reaction in a sealed state; after the reaction, aging, solid-liquid separation and drying are performed in sequence to obtain Fe 1-x Mn x C2O4·2H2O,0 <x<1; Configuration includes Fe 1-x Mn x A mixed solution of C2O4·2H2O, a lithium source, a phosphorus source and a carbon source is sequentially subjected to wet ball milling, spray drying and calcination to obtain lithium manganese iron phosphate.

2. The method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: The iron source includes at least one of ferrous sulfate, ferrous chloride, ferrous nitrate or ferrous acetate; And / or, the manganese source includes at least one of manganese sulfate, manganese chloride, manganese nitrate or manganese acetate.

3. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The total concentration of ferrous ions and manganese ions in the solution is 60 g / L to 90 g / L; And / or, the ratio of the sum of the molar amounts of the iron element in the iron source and the manganese element in the manganese source to the molar amount of the ammonium oxalate is 1:(1-1.2).

4. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The temperature of the water bath reaction is 25°C to 75°C, and the time of the water bath reaction is 0.5h to 3h; Preferably, adjusting the pH to acidic includes: adjusting the pH to 3-6.

5. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, lithium chloride or lithium citrate; and / or, the phosphorus source comprises at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate or phosphoric acid; And / or, the carbon source includes at least one of sucrose, glucose, carbon black, polyethylene glycol, citric acid or cellulose.

6. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: Calculated by the molar amount of lithium in the lithium source, the molar amount of phosphorus in the phosphorus source, the sum of the molar amounts of iron in the iron source and the manganese in the manganese source: The ratio of the molar amount of lithium element to the sum of the molar amounts of iron element and manganese element is 1 to 1.05, and the ratio of the molar amount of phosphorus element to the sum of the molar amounts of iron element and manganese element is 1 to 1.05; Preferably, based on the molar amount of carbon element in the carbon source, the ratio of the molar amount of carbon element to the sum of the molar amounts of iron element and manganese element is 0.06 to 0.

08.

7. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that: The preparation method comprises at least one of features (a) to (c): (a) the rotation speed of the wet ball milling is 300 rpm to 600 rpm, and the time of the wet ball milling is 6 h to 12 h; (b) the inlet air temperature of the spray drying is 200°C to 280°C, the outlet air temperature is 80°C to 110°C, and the atomizer frequency is 40Hz to 60Hz; (c) The calcination is carried out in a protective gas environment; the calcination temperature is 700° C. to 850° C., and the calcination time is 8 h to 12 h.

8. A lithium manganese iron phosphate positive electrode material, characterized in that: The lithium manganese iron phosphate is prepared by the preparation method of any one of claims 1 to 7.

9. A lithium ion battery, characterized in that: Comprising the lithium manganese iron phosphate positive electrode material as described in claim 8.

10. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 9.

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