Lithium iron manganese phosphate cathode material, preparation method thereof, electrode material, electrode and lithium ion battery

Abstract

The present invention relates to the technical field of lithium-ion batteries, and particularly relates to a lithium iron manganese phosphate cathode material and a preparation method thereof, an electrode material, an electrode and a lithium-ion battery. The expression of the lithium iron manganese phosphate cathode material is Li i Mn 1‑x‑y‑z Fe x M y M′ z PO4 / C; wherein, at any position of the particles of the lithium iron manganese phosphate cathode material, Δw = ∣w' - w∣ / w × 100% < 5% is satisfied, where w' is the Mn / Fe molar ratio at any position, and w is the average value of the Mn / Fe ratio in the cathode material. This cathode material has a small primary particle size, effectively improving the problems of low electronic conductivity and low ion mobility of the material. At the same time, the lithium-ion battery containing this cathode material has a high capacity retention rate and an average voltage retention rate during the cycling process.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a lithium iron manganese phosphate cathode material and a preparation method thereof, an electrode material, an electrode and a lithium-ion battery. Background Art

[0002] As an efficient energy storage and conversion device, the lithium-ion battery is an essential carrier for the wide application of new clean energy. With the continuous progress of lithium-ion battery technology, breakthroughs and upgrades in the industries such as energy storage power supplies and electric vehicles have been gradually achieved. At the same time, higher requirements are put forward for the energy density, safety performance, cycle life and manufacturing cost of lithium-ion batteries. The olivine-structured lithium iron phosphate cathode material has received continuous attention in recent years due to its high safety performance and cost advantages, and its installed capacity in the field of power batteries has approached that of ternary materials.

[0003] As an upgraded product of lithium iron phosphate, lithium iron manganese phosphate inherits the advantages of low cost and high safety of the olivine-structured cathode material. Its theoretical capacity is 170 mAh / g, the same as that of lithium iron phosphate. Due to the Mn 2+ / Mn 3+ discharge platform is as high as 4.1 V, and its energy density can be increased by 10%-20% compared with lithium iron phosphate. Therefore, the lithium iron manganese phosphate cathode material has received more and more extensive attention. However, different from the preparation process of lithium iron phosphate, with the increase of the Mn / Fe ratio, achieving the uniform distribution of manganese and iron elements is the key to preparing a lithium iron manganese phosphate cathode material with high energy density. In addition, due to the addition of Mn, lithium iron manganese phosphate has lower electronic conductivity and ion mobility than lithium iron phosphate. By means of reducing the particle size of the material and increasing carbon coating, the tap density of lithium iron manganese phosphate will be reduced and its specific surface area will be increased, affecting the processing characteristics of the material.

[0004] CN109650367A discloses a preparation method of a lithium iron manganese phosphate cathode material, which includes: mixing elemental iron, manganese dioxide and phosphoric acid aqueous solution to obtain a mixture A, ball-milling the mixture A to obtain manganese iron hydrogen phosphate; mixing the manganese iron hydrogen phosphate, lithium carbonate and glucose, and sand-milling until the particle size D 50 is 0.2-1 μm, and calcining after drying to obtain lithium iron manganese phosphate. However, this method directly uses elemental iron and manganese dioxide as raw materials, the reaction is slow, Mn / Fe phase separation is likely to occur, and this method has a complex reaction and difficult process control, and is not suitable for industrial production.

[0005] CN105514422A discloses a precursor and a preparation method of lithium iron manganese phosphate. The method includes: mixing a water-soluble divalent manganese source, a divalent iron source, a divalent metal M salt and a precipitant and reacting, and drying to obtain a pre-powder; then dispersing the pre-powder in water, adding a soluble decomposable ferrous salt, and performing heat treatment to obtain the oxalate precursor; mixing the precursor with a water-soluble lithium source, a phosphorus source and an organic carbon source, drying and sintering to obtain lithium iron manganese phosphate with less metal dissolution and excellent cycle performance. However, this process uses manganese iron oxalate as the precursor, which has a high gas generation during the sintering process, and is not conducive to obtaining a high tap density.

[0006] CN111268664A discloses a lithium iron manganese phosphate intermediate, lithium iron manganese phosphate and their manufacturing methods. The method includes: synchronously adding an aqueous solution of a mixed metal salt, a phosphorus source and an ammonia source to a reaction kettle for precipitation reaction, and aging to obtain an intermediate (NH4)Mn 1-x-y Fe x M y PO4·H2O, sintering after lithium doping to prepare lithium iron manganese phosphate, and then sintering after carbon doping to prepare a LiMn 1-x- y Fe x M y PO4 / C cathode material. However, this method uses an ammonium salt as the precursor, and a large amount of ammonia gas is released during the sintering process, which is not conducive to environmental protection. SUMMARY OF THE INVENTION

[0007] The object of the present invention is to overcome the above technical problems, and provide a lithium iron manganese phosphate cathode material and its preparation method, an electrode material, an electrode and a lithium ion battery. The lithium iron manganese phosphate cathode material has a high-strength structure and excellent electrochemical performance. At the same time, there is no gas release during the preparation process, and it is environmentally friendly.

[0008] To achieve the above object, in the first aspect of the present invention, a lithium iron manganese phosphate cathode material is provided. The expression of the lithium iron manganese phosphate cathode material is Li i Mn 1-x-y-z Fe x M y M′ z PO4 / C, where 0.09 ≤ x ≤ 0.59, 0 ≤ y ≤ 0.04, 0 ≤ z ≤ 0.04, 0.9 < i ≤ 1.2; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V and Ti; M′ is selected from at least one of Mg, Ca, Sr, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Y, Mo, Nb, B, Al, W, La and Sm;

[0009] Wherein, at any position of the particles of the lithium iron manganese phosphate cathode material, Δw = ∣w'-w∣ / w×100% < 5% is satisfied, where w' is the Mn / Fe molar ratio at any position, and w is the average value of the Mn / Fe ratio in the cathode material.

[0010] Preferably, in the expression of the lithium iron manganese phosphate cathode material, M and M′ are different.

[0011] Preferably, based on the total weight of the lithium iron manganese phosphate cathode material, the content of carbon element in the lithium iron manganese phosphate cathode material is 0.5-5 wt%.

[0012] Preferably, the lithium iron manganese phosphate cathode material has a secondary spherical particle structure formed by primary particles.

[0013] Preferably, the average particle size of the secondary spherical particles is 2-15 μm; the average particle size of the primary particles of the lithium iron manganese phosphate cathode material is 5-300 nm.

[0014] The second aspect of the present invention provides a preparation method of a lithium iron manganese phosphate cathode material, and the preparation method includes:

[0015] (1) Providing a lithium iron manganese phosphate precursor with the expression of (Mn 1-α-β Fe α M β )OOH, in the formula, 0.09 ≤ α ≤ 0.59, 0 ≤ β ≤ 0.04; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V and Ti;

[0016] (2) In the presence of a solvent, mixing and homogenizing the lithium iron manganese phosphate precursor, a phosphorus source, a lithium source, an M′ source and a carbon source to obtain a first slurry;

[0017] (3) Grinding the first slurry, and spray-drying the obtained ground slurry to obtain a spray-dried material;

[0018] (4) Sintering the spray-dried material in a first non-oxidizing atmosphere to obtain a lithium iron manganese phosphate cathode material.

[0019] Preferably, the average particle size of the primary particles of the lithium iron manganese phosphate precursor is 10-500 nm; the specific surface area of the lithium iron manganese phosphate precursor is 10-50 m 2 / g.

[0020] Preferably, the lithium iron manganese phosphate precursor is prepared by the following method: (a) providing a mixed metal salt solution containing a manganese source, an iron source, and an optional M source; providing a complexing agent solution and a precipitating agent solution; (b) in a second non-oxidizing atmosphere, adding the mixed metal salt solution, the complexing agent solution, and the precipitating agent solution to water for coprecipitation reaction to obtain a second slurry; (c) performing solid-liquid separation and washing on the second slurry to obtain the lithium iron manganese phosphate precursor.

[0021] In the third aspect of the present invention, an electrode material is provided. The electrode material contains an active material, a conductive agent, and a binder. The active material is the lithium iron manganese phosphate cathode material provided in the first aspect, or the lithium iron manganese phosphate cathode material prepared according to the preparation method provided in the second aspect.

[0022] In the fourth aspect of the present invention, an electrode is provided. The electrode includes a current collector, and an electrode material coated and / or filled on the current collector. The electrode material is the electrode material provided in the third aspect.

[0023] In the fifth aspect of the present invention, a lithium-ion battery is provided. The lithium-ion battery includes: the electrode provided in the fourth aspect as the positive electrode.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The lithium iron manganese phosphate cathode material provided by the present invention has small primary particle size, effectively improves the problems of low electronic conductivity and low ion mobility of the material, and enhances the capacity and rate performance of the cathode material; at the same time, the lithium iron manganese phosphate cathode material provided by the present invention forms a high-strength secondary spherical particle structure from primary particles, solving the problem of poor processing characteristics caused by simply reducing the particle size.

[0026] (2) The present invention uses a lithium iron manganese phosphate precursor with a specific structure (i.e., the lithium iron manganese phosphate precursor is a metal hydroxy oxide, the element distribution in the precursor is uniform, and the doped element M enters the metal site to form nanoparticles with a stable structure, which can effectively solve the problem of uneven distribution of Mn and Fe). The prepared lithium iron manganese phosphate cathode material has a high-strength structure and excellent electrochemical performance. Specifically, the lithium iron manganese phosphate precursor reacts with the phosphorus source during the mixing and grinding process to form a stable Me-P-O structure framework, there is no gas release during the sintering process, the loss rate is low, and the prepared lithium iron manganese phosphate cathode material has high strength and excellent electrical performance.

[0027] (3) The preparation method of the lithium iron manganese phosphate cathode material provided by the present invention is simple. By mixing and grinding the lithium iron manganese phosphate precursor with a specific structure, and then performing spray drying and sintering to prepare the lithium iron manganese phosphate cathode material, it is easy to realize industrial production.

[0028] (4) Using the lithium iron manganese phosphate cathode material provided by the present invention in a lithium-ion battery can improve the electrochemical performance of the lithium-ion battery, especially with good rate performance, high capacity retention rate and average voltage retention rate during cycling. Description of the Drawings

[0029] Figure 1 is the XRD pattern of the lithium iron manganese phosphate precursor Z1 prepared in Preparation Example 1;

[0030] Figure 2 is the SEM image of the lithium iron manganese phosphate cathode material C1 prepared in Example 1;

[0031] Figure 3 is the XRD pattern of the lithium iron manganese phosphate cathode material C1 prepared in Example 1;

[0032] Figure 4 is the distribution map of Mn and Fe elements obtained by EDS energy spectrum scanning of the lithium iron manganese phosphate cathode material C1 in Example 1;

[0033] Figure 5 are the charge-discharge curves of the lithium-ion battery A1 assembled with the lithium iron manganese phosphate cathode material C1 prepared in Example 1 and the lithium-ion battery A4 assembled with the lithium iron manganese phosphate cathode material C4 prepared in Example 4 at a rate of 0.1C, respectively. Detailed Description of the Invention

[0034] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0035] In the present invention, without special circumstances, "first" and "second" neither represent the order nor limit each material or step, and are only used to distinguish or indicate that these are not the same material or step. For example, "first slurry" and "second slurry" are only used to indicate that these are not the same slurry; similarly, "first non-oxidizing atmosphere" and "second non-oxidizing atmosphere" are only used to indicate that these are not the same non-oxidizing atmosphere.

[0036] The first aspect of the present invention provides a lithium iron manganese phosphate cathode material, and the expression of the lithium iron manganese phosphate cathode material is Li i Mn 1-x-y-z Fe x M y M′ zPO4 / C, where 0.09 ≤ x ≤ 0.59, 0 ≤ y ≤ 0.04, 0 ≤ z ≤ 0.05, 0.9 < i ≤ 1.2; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V, and Ti; M′ is selected from at least one of Mg, Ca, Sr, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Y, Mo, Nb, B, Al, W, La, and Sm;

[0037] Wherein, at any position of the particles of the lithium iron manganese phosphate cathode material, Δw = ∣w'-w∣ / w × 100% < 5% is satisfied, where w' is the Mn / Fe molar ratio at any position and w is the average value of the Mn / Fe ratio in the cathode material.

[0038] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate cathode material, 0.09 ≤ x ≤ 0.59, 0.01 ≤ y ≤ 0.04, 0.01 ≤ z ≤ 0.04, 1 ≤ i ≤ 1.2.

[0039] In some embodiments of the present invention, more preferably, in the expression of the lithium iron manganese phosphate cathode material, 0.19 ≤ x ≤ 0.39, 0.01 ≤ y ≤ 0.02, 0.01 ≤ z ≤ 0.02, 1 ≤ i ≤ 1.1.

[0040] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate cathode material, M and M′ are different.

[0041] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate cathode material, M is from the lithium iron manganese phosphate precursor; M′ is provided by the M′ source and doped into the lithium iron manganese phosphate cathode material through the sintering process.

[0042] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate cathode material, M is selected from Mg and / or Cu; M′ is selected from at least one of Ti, Nb, and B.

[0043] In some embodiments of the present invention, in the lithium iron manganese phosphate cathode material, even if the content of carbon element is relatively small, the object of the present invention can be achieved. Preferably, based on the total weight of the cathode material, the content of carbon element in the cathode material is 0.5 - 5 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 3 wt%, 5 wt%, and any value within the range composed of any two numerical values, preferably 1 - 3 wt%, more preferably 1.8 - 2.5 wt%.

[0044] In some embodiments of the present invention, preferably, the lithium iron manganese phosphate cathode material has a secondary spherical particle structure formed by primary particles; more preferably, the average particle size of the secondary spherical particles is 2-15 μm, for example, 2 μm, 4 μm, 6.4 μm, 6.9 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 8.1 μm, 8.5 μm, 9 μm, 9.2 μm, 10.4 μm, 15 μm, and any value within the range composed of any two numerical values, preferably 4-9 μm; the average particle size of the primary particles of the lithium iron manganese phosphate cathode material is 5-300 nm, for example, 5 nm, 40 nm, 46 nm, 49 nm, 50 nm, 56 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 200 nm, 300 nm, and any value within the range composed of any two numerical values, preferably 40-120 nm.

[0045] The lithium iron manganese phosphate cathode material provided by the present invention has the structural characteristics of secondary agglomerated particles. By controlling the grinding particle size and optimizing the sintering process, primary particles with an average particle size of 5-300 nm and uniform size are generated, which improves the electronic conductivity and ion migration rate of the material and the rate performance of the material; by using two-fluid spray drying granulation, the in-situ generated Me-P-O structure is beneficial to the formation of dense agglomerated particles, and the gas release amount during the sintering process is small, so that the cathode material maintains a high-strength structure and optimizes the processing characteristics of the material during the electrode preparation process. In addition, the lithium iron manganese phosphate cathode material provided by the present invention has good rate performance, high capacity retention rate and average voltage retention rate during the cycling process.

[0046] In some embodiments of the present invention, preferably, in the XRD diffraction pattern obtained by the lithium iron manganese phosphate cathode material under CuKa radiation, the strongest diffraction peak appears in the range of 2θ = 35°-36°, and obvious diffraction peaks appear near 2θ = 17.8°, 25.5°, 29.6° and 36.4° respectively, showing an orthorhombic crystal structure. The crystal structure of the lithium iron manganese phosphate cathode material can be determined by XRD characterization.

[0047] In some embodiments of the present invention, preferably, the primary particles of the lithium iron manganese phosphate cathode material satisfy: p / p0×100% > 50%, where p is the number of particles of the lithium iron manganese phosphate cathode material whose primary particle size satisfies (D m ±0.2D m ) nm, D m is the average particle size of the primary particles of the lithium iron manganese phosphate cathode material, and p0 is the total number of primary particles of the lithium iron manganese phosphate cathode material to be measured.

[0048] In some embodiments of the present invention, preferably, the specific surface area of the lithium iron manganese phosphate cathode material is S0, and the specific surface area after applying a pressure of 2T is S1, where (S1 - S0) / S0×100% ≤ 10%, for example, 2%, 2.3%, 3%, 3.3%, 3.4%, 3.9%, 4%, 4.7%, 5%, 5.2%, 5.6%, 6%, 6.4%, 7%, 7.7%, 8%, 8.2%, 9%, 9.6%, 10%, and any value within the range composed of any two of these values. Preferably, (S1 - S0) / S0×100% ≤ 5%.

[0049] The second aspect of the present invention provides a method for preparing a lithium iron manganese phosphate cathode material, the preparation method comprising:

[0050] (1) providing a lithium iron manganese phosphate precursor expressed as (Mn 1-α-β Fe α M β )OOH, where 0.09 ≤ α ≤ 0.59 and 0 ≤ β ≤ 0.04; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V, and Ti;

[0051] (2) in the presence of a solvent, mixing and homogenizing the lithium iron manganese phosphate precursor, a phosphorus source, a lithium source, an M' source, and a carbon source to obtain a first slurry;

[0052] (3) grinding the second slurry, and spray-drying the obtained ground slurry to obtain a spray-dried material;

[0053] (4) sintering the spray-dried material in a first non-oxidizing atmosphere to obtain a lithium iron manganese phosphate cathode material.

[0054] In the present invention, in step (1), the lithium iron manganese phosphate precursor is a manganese-iron-containing hydroxy oxide, which is prepared by a coprecipitation method using water-soluble metal salts as raw materials to solve the problem of uneven Mn / Fe distribution. In addition, the lithium iron manganese phosphate precursor reacts with the P source during the mixing and grinding processes to form a stable Me-P-O structural framework, with no gas release during the sintering process and a low burn-off rate. The prepared cathode material has the characteristics of high capacity and stable structure.

[0055] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate precursor, 0.09 ≤ α ≤ 0.59 and 0.01 ≤ β ≤ 0.04.

[0056] In some embodiments of the present invention, more preferably, in the expression of the lithium iron manganese phosphate precursor, 0.19 ≤ α ≤ 0.39 and 0.01 ≤ β ≤ 0.02.

[0057] In some embodiments of the present invention, preferably, in the expression of the lithium iron manganese phosphate precursor, M is selected from Mg and / or Cu.

[0058] In some embodiments of the present invention, preferably, the average particle size of the primary particles of the lithium iron manganese phosphate precursor is 10 - 500 nm, for example, 10 nm, 50 nm, 89 nm, 93 nm, 96 nm, 102 nm, 104 nm, 124 nm, 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, and any value within the range composed of any two of these values, preferably 50 - 200 nm; the specific surface area of the lithium iron manganese phosphate precursor is 10 - 50 m 2 / g, for example, 10 m 2 / g, 20 m 2 / g, 26 m 2 / g, 28 m 2 / g, 32 m 2 / g, 34 m 2 / g, 35 m 2 / g, 39 m 2 / g, 40 m 2 / g, 50 m 2 / g, and any value within the range composed of any two of these values, preferably 20 - 40 m 2 / g. When the average particle size of the primary particles of the lithium iron manganese phosphate precursor is smaller, it is more conducive to improving the grinding efficiency in the preparation process of the lithium iron manganese phosphate cathode material; when the specific surface area of the lithium iron manganese phosphate precursor is higher, providing a rich contact area, it is more conducive to the progress of the phosphating reaction.

[0059] In some embodiments of the present invention, preferably, in the XRD diffraction pattern of the lithium iron manganese phosphate precursor obtained under CuKa radiation, obvious diffraction peaks appear near 2θ = 35.2°, 39.9°, 54.4° and 63.2°, showing a hexagonal crystal structure. That is, the crystal structure of the lithium iron manganese phosphate precursor can be determined by XRD characterization.

[0060] In the present invention, the source of the lithium iron manganese phosphate precursor has a relatively wide selection range, as long as the expression of the lithium iron manganese phosphate precursor meets the above limitations. Preferably, the lithium iron manganese phosphate precursor is prepared by the following method:

[0061] (a) Provide a mixed metal salt solution containing a manganese source, an iron source and an optional M source; provide a complexing agent solution and a precipitant solution;

[0062] (b) In a second non-oxidizing atmosphere, add the mixed metal salt solution, the complexing agent solution and the precipitant solution to water for coprecipitation reaction to obtain a second slurry;

[0063] (c) Solid-liquid separate and wash the second slurry to obtain a lithium iron manganese phosphate precursor.

[0064] In some embodiments of the present invention, preferably, in step (a), the manganese source is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0065] In some embodiments of the present invention, preferably, in step (a), the iron source is selected from at least one of ferric sulfate, ferrous sulfate, ferric nitrate, iron acetate, and ferric chloride.

[0066] In some embodiments of the present invention, preferably, in step (a), the M source is selected from at least one of sulfates, nitrates, acetates, and chlorides containing M, where M is selected from at least one of Mg, Cu, Co, Ni, Zn, V, and Ti. In the present invention, the M source includes, but is not limited to, copper sulfate, copper nitrate, copper acetate, copper chloride, magnesium sulfate, magnesium nitrate, magnesium chloride, magnesium acetate, etc.

[0067] In some embodiments of the present invention, preferably, in step (a), the molar ratio of the manganese source in terms of Mn, the iron source in terms of Fe, and the M source in terms of M satisfies: n(Mn):n(Fe):n(M), where 0.37 ≤ n(Mn) ≤ 0.91, 0.09 ≤ n(Fe) ≤ 0.59, 0 ≤ n(M) ≤ 0.04; further preferably, 0.37 ≤ n(Mn) ≤ 0.9, 0.09 ≤ n(Fe) ≤ 0.59, 0.01 ≤ n(M) ≤ 0.04; more preferably, 0.59 ≤ n(Mn) ≤ 0.8, 0.19 ≤ n(Fe) ≤ 0.39, 0.01 ≤ n(M) ≤ 0.02. The manganese source, iron source, and M source within the above molar ratio range are conducive to obtaining a lithium iron manganese phosphate precursor with a stable structure, which is conducive to improving the structural stability of the lithium iron manganese phosphate cathode material and endowing it with a high energy density.

[0068] In some specific embodiments of the present invention, in step (a), the molar ratio of the manganese source in terms of Mn, the iron source in terms of Fe, and the M source in terms of M is 37 - 91:9 - 59:0 - 4, for example, 37:59:4, 40:59:1, 59:39:2, 65:35:0, 65:34:1, 70:29:1, 80:19:1, 90:9:1, 91:9:0, and any value within the range composed of any two numerical values, preferably 37 - 90:9 - 59:1 - 4, and most preferably 59 - 80:19 - 39:1 - 2.

[0069] In some embodiments of the present invention, preferably, in step (a), the concentration of the total metal ions in the mixed metal salt solution is 0.5 - 3 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, and 3 mol / L, and any value within the range composed of any two of these values.

[0070] In some embodiments of the present invention, preferably, in step (a), the concentration of the complexing agent in the complexing agent solution is 2 - 14 mol / L, for example, 2 mol / L, 3 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, 14 mol / L, and any value within the range composed of any two of these values. In the present invention, the complexing agent in the complexing agent solution is selected from at least one of ammonia water, disodium ethylenediaminetetraacetate, ammonium nitrate, ammonium chloride, and ammonium sulfate.

[0071] In some embodiments of the present invention, preferably, in step (a), the concentration of the precipitating agent in the precipitating agent solution is 2 - 10 mol / L, for example, 2 mol / L, 3 mol / L, 5 mol / L, 8 mol / L, 10 mol / L, and any value within the range composed of any two of these values. In the present invention, the precipitating agent in the precipitating agent solution is selected from sodium hydroxide and / or potassium hydroxide.

[0072] In some embodiments of the present invention, preferably, in step (b), the mixed metal salt solution, the complexing agent solution, and the precipitating agent solution are added to water in a co-current manner.

[0073] In the present invention, by controlling the temperature, pH, and the amount of the complexing agent of the co-precipitation reaction, the growth of the particles is controlled to obtain nanoscale particles with uniform size, and Mn, Fe, and the doped metal M are uniformly distributed at the atomic level therein.

[0074] In some embodiments of the present invention, preferably, in step (b), the co-precipitation reaction is carried out under stirring. The conditions of the co-precipitation reaction include: the rotation speed is 500 - 1000 rpm, the pH is 8 - 12, the temperature is 30 - 90 °C, and the time is 0.1 - 5 h. The pH of the co-precipitation reaction can be controlled to be 8 - 12 (the error of the pH can be ±0.5) by adjusting the addition rate of the precipitating agent solution.

[0075] In some embodiments of the present invention, preferably, in step (b), the second non-oxidizing atmosphere is selected from nitrogen and / or argon; more preferably, the second non-oxidizing atmosphere is selected from nitrogen.

[0076] In some embodiments of the present invention, in step (c), there is no particular limitation on the method of solid-liquid separation, and the prior art known to those skilled in the art can be adopted. For example, positive pressure filtration, negative pressure filtration, centrifugation, and suction filtration can be used for solid-liquid separation to obtain the product of solid-liquid separation.

[0077] In some embodiments of the present invention, there is also no particular limitation on the method of washing, and the conventional washing methods in the art can all be applied to the present invention. Preferably, in step (c), the washing process includes: washing the product of solid-liquid separation with an appropriate amount of water / alkaline aqueous solution until the conductivity of the washing liquid ≤ 200 μs / cm.

[0078] In some embodiments of the present invention, preferably, in step (c), after drying the washed product, the lithium iron manganese phosphate precursor is obtained; more preferably, the drying temperature is 80 - 150 °C and the time is 1 - 10 h.

[0079] In some embodiments of the present invention, preferably, in step (2), the molar ratio of the lithium iron manganese phosphate precursor, the phosphorus source calculated as P, the lithium source calculated as Li, the M' source, and the carbon source is 1:0.95 - 1.1:1 - 1.1:0.01 - 0.04:0.05 - 0.15. For example, 1:0.95:1:0.01:0.05, 1:1.02:1.01:0.01:0.07, 1:1.02:1.04:0.01:0.08, 1:1.02:1.04:0.02:0.08, 1:1.03:1.02:0.01:0.08, 1:1.03:1.04:0.01:0.08, 1:1.03:1.04:0.01:0.09, 1:1.06:1.06:0.02:0.09, 1:1.07:1.06:0.02:0.12, 1:1.1:1.1:0.04:0.15, and any value within the range composed of any two numerical values. Preferably, it is 1:1.02 - 1.07:1.01 - 1.06:0.01 - 0.02:0.07 - 0.12. Selecting the lithium iron manganese phosphate precursor, phosphorus source, lithium source, M' source, and carbon source that meet the above molar ratio range is beneficial to improving the electronic conductivity and ionic conductivity of the cathode material and obtaining high electrical performance.

[0080] In some embodiments of the present invention, preferably, in step (2), the phosphorus source is selected from at least one of phosphoric acid, ammonium dihydrogen phosphate, and lithium dihydrogen phosphate.

[0081] In some embodiments of the present invention, preferably, in step (2), the lithium source is selected from at least one of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate, and is preferably at least one of lithium carbonate, lithium hydroxide, and lithium chloride.

[0082] In some embodiments of the present invention, preferably, in step (2), the M′ source is selected from at least one of sulfates, nitrates, acetates, oxides, and acids containing M′; more preferably, the M′ source is selected from at least one of titanium dioxide, niobium pentoxide, and boric acid; most preferably, the M′ source is selected from titanium dioxide and / or niobium pentoxide.

[0083] In some embodiments of the present invention, preferably, in step (2), the carbon source is selected from at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine, and is preferably at least one of glucose, sucrose, starch, and polyethylene glycol.

[0084] In some embodiments of the present invention, in step (2), there is no particular limitation on the method of mixing and homogenizing. For example, mixing and homogenizing can be carried out by mechanical stirring to form a uniform slurry. There is also no particular limitation on the stirring temperature and stirring rate, as long as a uniform second slurry can be formed.

[0085] In some embodiments of the present invention, there is no particular limitation on the type of the solvent, as long as a uniform second slurry can be formed. For example, the solvent can be water, ethanol, etc., and is preferably water; there is also no particular limitation on the amount of the solvent, and it is also based on the ability to form a uniform second slurry.

[0086] In the present invention, there is no limitation on the grinding method. Preferably, in step (3), the average particle size of the ground slurry is 0.1 - 0.6 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, and any value within the range composed of any two numerical values.

[0087] In some embodiments of the present invention, preferably, in step (3), the spray drying is selected from two-fluid spray drying, wherein the nozzle size is 0.5 - 5 mm, the spray gun pressure is 0.2 - 1 MPa, the inlet air temperature is 150 - 300 °C, and the outlet air temperature is 80 - 180 °C. In the present invention, unless otherwise specified, the pressure refers to the gauge pressure.

[0088] In some embodiments of the present invention, preferably, in step (3), the particle size of the spray-dried material is 2 - 15 μm, for example, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, and any value within the range composed of any two of these values.

[0089] In some embodiments of the present invention, preferably, in step (4), the first non-oxidizing atmosphere is selected from nitrogen and a mixture of nitrogen and hydrogen. In the present invention, in the mixture of nitrogen and hydrogen, the content of hydrogen is 1 - 5 vol%.

[0090] In some embodiments of the present invention, preferably, in step (4), the sintering conditions include: the temperature is 600 - 900 °C, preferably 600 - 750 °C; the time is 5 - 20 h, preferably 8 - 12 h.

[0091] The third aspect of the present invention provides an electrode material, which contains an active material, a conductive agent, and a binder. The active material is the lithium iron phosphate manganese cathode material described in the first aspect or the lithium iron phosphate manganese cathode material prepared according to the preparation method described in the second aspect.

[0092] The fourth aspect of the present invention provides an electrode, which includes a current collector, and an electrode material coated and / or filled on the current collector. The electrode material is the electrode material described in the third aspect.

[0093] In some embodiments of the present invention, the electrode is prepared by the following method: a slurry containing an active material, a conductive agent, and a binder and a solvent is coated and / or filled on a current collector, and then dried, with or without calendering. The active material is the lithium iron phosphate manganese cathode material described in the first aspect or the lithium iron phosphate manganese cathode material obtained according to the preparation method described in the second aspect.

[0094] The fifth aspect of the present invention provides a lithium-ion battery, which includes: the electrode provided in the fourth aspect as the positive electrode.

[0095] In a specific embodiment of the present invention, the lithium-ion battery includes an electrode assembly and an electrolyte. The electrode assembly and the electrolyte are sealed in a battery housing. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive electrode and the negative electrode. The positive electrode is the electrode provided in the fourth aspect.

[0096] Since the present invention only relates to the improvement of the active material contained in the existing electrode material, there are no special limitations on other components and structures of the lithium-ion battery.

[0097] For example, for the positive electrode of a lithium-ion battery, the content and type of the conductive agent of the positive electrode material described in the present invention are well-known to those skilled in the art. The conductive agent can be selected from one or more of conductive carbon black (Super-P), acetylene black, Ketjen black, graphene, and carbon nanotubes. The present invention preferably uses carbon nanotubes as the conductive agent.

[0098] The binder of the positive electrode material described in the present invention can use all known binders in the art that can be used for lithium-ion batteries. It can be selected from fluororesins and / or polyolefin compounds, such as one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and styrene-butadiene rubber. The present invention preferably uses polyvinylidene fluoride as the binder.

[0099] In some embodiments of the present invention, preferably, the mass ratio of lithium iron phosphate manganese positive electrode material, conductive agent, and binder is 80-96:10-2:10-2, preferably 90:5:5.

[0100] The current collector described in the present invention can be various current collectors well-known to those skilled in the art, such as aluminum foil, copper foil, nickel-plated steel strip, etc. The present invention selects aluminum foil as the current collector.

[0101] The solvent described in the present invention can use all known solvents in the art that can be used for the preparation of lithium-ion battery electrodes. For example, it can be ethanol and / or N-methylpyrrolidone (NMP), preferably N-methylpyrrolidone. The amount of the solvent is based on the formation of the required coating slurry.

[0102] In some embodiments of the present invention, a lithium metal sheet can be used as the negative electrode of the lithium-ion battery.

[0103] In some embodiments of the present invention, the electrolyte of the lithium-ion battery can be the electrolyte conventionally used in the art. The concentration of the electrolyte is generally 0.2-8 mol / L. The present invention selects an equal-volume mixture of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC) as the electrolyte.

[0104] The separator described in the present invention has electrical insulation performance and liquid retention performance, is disposed between the positive electrode and the negative electrode, and is sealed in the battery case together with the positive electrode, the negative electrode, and the electrolyte. The separator can be various separators commonly used in the art, such as a composite film formed by welding or bonding polyethylene, polypropylene, modified polyethylene felt, modified polypropylene felt, ultra-fine glass fiber felt, vinylon felt, or nylon felt of various production grades well-known to those skilled in the art and a wettable polyolefin microporous membrane. The present invention selects a polyethylene porous membrane as the separator.

[0105] The present invention will be described in detail below through examples.

[0106] The composition of the material, the structure or morphology of atoms or molecules inside the material, etc. are obtained by XRD. The model of the XRD diffractometer used is the XRD-6000 X-ray powder diffractometer (Shimadzu, Japan). The test conditions of XRD are as follows: Cu target, Kα ray (wavelength λ = 0.154 nm), tube voltage of 40 kV, tube current of 200 mA, and scanning speed of 10° (2θ) / min.

[0107] The surface morphology of the material is characterized by scanning electron microscopy (SEM). The model of the scanning electron microscope used is S-4800 (manufactured by Hitachi, Japan). The test conditions of the scanning electron microscope are as follows: acceleration voltage of 1 kV and magnification of 10K. The average particle sizes of the primary particles and secondary spherical particles in the material are measured from the scanning electron microscope images.

[0108] The analysis of carbon (C) element is carried out on an Elementar Micro Cube elemental analyzer. The specific operation methods and conditions are as follows: The sample is weighed at 1 - 2 mg in a tin cup, placed in an automatic sample injection tray, and enters the combustion tube through a ball valve for combustion. The combustion temperature is 1000 °C (in order to remove the interference of the atmosphere during sample injection, helium purge is used). Then, the gas after combustion is reduced by reducing copper to form carbon dioxide, and then the carbon dioxide is detected by a TCD detector.

[0109] In the expressions of the precursor and the cathode material respectively, the elements and their contents are obtained by testing with an inductively coupled plasma spectrometer (ICP). The instrument is purchased from PerkinElmer Instruments Co., Ltd., and the model is PE-7000DV.

[0110] The process parameters of Preparation Examples 1 - 7 and Comparative Preparation Examples 1 - 2, as well as the physical property parameters of the prepared precursors (Z1 - Z7 and DZ1 - DZ2), are all listed in Table 1.

[0111] Preparation Example 1

[0112] (a) Manganese sulfate, iron sulfate, and magnesium sulfate (all calculated as metal elements) are dissolved in water at a molar ratio of 65:34:1 to obtain a mixed metal salt solution with a total metal ion concentration of 2 mol / L; ammonia water is dissolved in water as a complexing agent to obtain a complexing agent solution with a concentration of 5 mol / L; sodium hydroxide is dissolved in water as a precipitating agent to obtain a precipitating agent solution with a concentration of 8 mol / L.

[0113] (b) Pure water is added to the reaction kettle. At a rotation speed of 700 rpm, the above-mentioned mixed metal salt solution, complexing agent solution, and precipitating agent solution are slowly added to the reaction kettle in a co-current manner, controlling the temperature of the reaction kettle to be 60 °C and the pH to be 10.0 ± 0.5. After the feeding is completed, continue to stir for 1 h to obtain the first slurry.

[0114] (c) Filter the above first slurry and wash it with pure water until the conductivity of the filtrate ≤ 200 μs / cm; place the filter cake in a forced-air oven and dry it at 120 °C for 8 h to obtain a lithium iron manganese phosphate precursor Z1 with the formula (Mn 0.65 Fe 0.34 Mg 0.01 )OOH;

[0115] Among them, the XRD pattern of the above lithium iron manganese phosphate precursor Z1 is as shown in Figure 1 As can be seen from Figure 1 , obvious diffraction peaks appear near 2θ = 35.2°, 39.9°, 54.4° and 63.2°, indicating that the lithium iron manganese phosphate precursor Z1 has a crystal structure of hexagonal system.

[0116] Preparation Example 2

[0117] (a) Dissolve manganese sulfate, iron sulfate, and magnesium sulfate (all calculated as metal elements) in water at a molar ratio of 70:29:1 to obtain a mixed metal salt solution with a total metal ion concentration of 2 mol / L; dissolve ammonia water as a complexing agent in water to obtain a complexing agent solution with a concentration of 5 mol / L; dissolve sodium hydroxide as a precipitating agent in water to obtain a precipitating agent solution with a concentration of 8 mol / L;

[0118] (b) Add pure water to the reaction kettle. At a rotation speed of 700 rpm, slowly add the above mixed metal salt solution, complexing agent solution, and precipitating agent solution to the reaction kettle in a co-current manner, control the temperature of the reaction kettle at 60 °C, and the pH at 9.0 ± 0.5. After the feeding is completed, continue stirring for 1 h to obtain a first slurry;

[0119] (c) Filter the above first slurry and wash it with pure water until the conductivity of the filtrate ≤ 200 μs / cm; place the filter cake in a forced-air oven and dry it at 120 °C for 8 h to obtain a lithium iron manganese phosphate precursor Z2 with the formula (Mn 0.7 Fe 0.29 Mg 0.01 )OOH;

[0120] Among them, it can be known from the detection results of XRD that the lithium iron manganese phosphate precursor Z2 has a crystal structure of hexagonal system.

[0121] Preparation Example 3

[0122] (a) Dissolve manganese chlorate, iron chlorate, and copper sulfate (both calculated as metal elements) in water at a molar ratio of 80:19:1 to obtain a mixed metal salt solution with a total metal ion concentration of 2 mol / L; dissolve ammonium citrate tribasic as a complexing agent in water to obtain a complexing agent solution with a concentration of 3 mol / L; dissolve sodium hydroxide as a precipitating agent in water to obtain a precipitating agent solution with a concentration of 8 mol / L.

[0123] (b) Add pure water to the reaction kettle. While stirring at a speed of 700 rpm, slowly add the above-mentioned mixed metal salt solution, complexing agent solution, and precipitating agent solution to the reaction kettle in a co-current manner. Control the temperature of the reaction kettle at 65 °C and the pH at 10.0 ± 0.5. After the feeding is completed, continue stirring for 1 h to obtain the first slurry.

[0124] (c) Filter the above-mentioned first slurry by suction and wash it with pure water until the conductivity of the filtrate ≤ 200 μs / cm; place the filter cake in a forced-air oven and dry it at 120 °C for 8 h to obtain the lithium iron manganese phosphate precursor Z3 with the formula (Mn 0.8 Fe 0.19 Cu 0.01 )OOH.

[0125] Among them, according to the XRD test results, the lithium iron manganese phosphate precursor Z3 has a hexagonal crystal structure.

[0126] Preparation Example 4

[0127] According to the method of Preparation Example 1, the difference is that in step (a), magnesium sulfate is not added. That is, the molar ratio of manganese sulfate and iron sulfate (both calculated as metal elements) is replaced with 65:35, and the other conditions are the same, to obtain the precursor Z4 with the formula (Mn 0.65 Fe 0.35 )OOH.

[0128] Among them, according to the XRD test results, the lithium iron manganese phosphate precursor Z4 has a hexagonal crystal structure.

[0129] Preparation Example 5

[0130] According to the method of Preparation Example 1, the difference is that in step (a), the molar ratio of manganese sulfate, iron sulfate, and magnesium sulfate (both calculated as metal elements) of 65:34:1 is replaced with the molar ratio of manganese sulfate, iron sulfate, and cobalt sulfate (both calculated as metal elements) of 65:34:1, and the other conditions are the same, to obtain the precursor Z5 with the formula (Mn 0.65 Fe 0.34 Co 0.01 )OOH.

[0131] Among them, from the XRD test results, it can be seen that the lithium iron manganese phosphate precursor Z5 has a crystal structure of hexagonal system.

[0132] Preparation Example 6

[0133] According to the method of Preparation Example 1, the difference is that in step (a), manganese sulfate, iron sulfate, and magnesium sulfate (all calculated as metal elements) are replaced with a molar ratio of 40:59:1 instead of 65:34:1, and the other conditions are the same, to obtain the (Mn 0.4 Fe 0.59 Mg 0.01 )OOH precursor Z6.

[0134] Among them, from the XRD test results, it can be seen that the lithium iron manganese phosphate precursor Z6 has a crystal structure of hexagonal system.

[0135] Preparation Example 7

[0136] According to the method of Preparation Example 1, the difference is that in step (b), the pH is replaced with 7.5 ± 0.5, and the other conditions are the same, to obtain the (Mn 0.65 Fe 0.34 Mg 0.01 )OOH precursor Z7.

[0137] Among them, from the XRD test results, it can be seen that the lithium iron manganese phosphate precursor Z7 has a crystal structure of hexagonal system.

[0138] Comparative Preparation Example 1

[0139] According to the method of Preparation Example 4, the difference is that there is no complexing agent solution, and the other conditions are the same, to obtain the precursor DZ1.

[0140] Comparative Preparation Example 2

[0141] Mix manganese sulfate and iron sulfate (both calculated as metal elements) with a molar ratio of 65:35 to obtain the precursor DZ2.

[0142] Table 1

[0143]

[0144] Continued Table 1

[0145]

[0146] From the data in Table 1, it can be seen that compared with Comparative Preparation Examples 1-2, the lithium iron manganese phosphate precursors prepared in Preparation Examples 1-7 are homogeneous hydroxyoxides under the premise of satisfying the expression (Mn 1-α-β Fe α M β )OOH, that is, nanometer particles with uniform element distribution are formed.

[0147] The process parameters of Examples 1-11 and Comparative Examples 1-3 and the physical property parameters of the lithium iron manganese phosphate cathode materials (C1-C11 and DC1-DC3) prepared therefrom are listed in Table 2.

[0148] Example 1

[0149] (1) The lithium iron manganese phosphate precursor Z1 expressed as (Mn 0.65 Fe 0.34 Mg 0.01 )OOH, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide and glucose were mixed with pure water in a molar ratio of 1:1.02:1.04:0.02:0.08, and mechanically stirred to be uniformly mixed to obtain a second slurry;

[0150] (2) The above-mentioned second slurry was transferred to a sand mill for grinding to obtain a ground slurry with an average particle size of 0.35 μm; the ground slurry was spray-dried and granulated by a two-fluid spray dryer, wherein the nozzle size was 1 mm, the spray gun pressure was 0.5 MPa, the inlet air temperature was 230 ± 5 °C, and the outlet air temperature was controlled at 110 ± 5 °C to obtain a spray-dried material with a particle size of 7.9 μm;

[0151] (3) In a nitrogen atmosphere, the above-mentioned spray-dried material was sintered at 700 °C for 10 h, and after screening, the lithium iron manganese phosphate cathode material C1 expressed as Li 1.04 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 PO4 / C was obtained.

[0152] Among them, the SEM image of the above-mentioned lithium iron manganese phosphate cathode material C1 is shown in Figure 2. As Figure 2 can be seen, the lithium iron manganese phosphate cathode material C1 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 56 nm, and the average particle size of the secondary spherical particles is 7.6 μm.

[0153] Among them, the XRD pattern of the above-mentioned lithium iron manganese phosphate cathode material C1 is as Figure 3 shown. As Figure 3 can be seen, the strongest diffraction peak appears at 2θ = 35.4°, and obvious diffraction peaks appear at 2θ = 17.8°, 25.5°, 29.6° and 36.4° respectively, indicating that the lithium iron manganese phosphate cathode material C1 has an orthorhombic crystal structure.

[0154] Among them, the distribution maps of Mn and Fe elements obtained by EDS energy spectrum scanning of the above-mentioned lithium iron manganese phosphate cathode material C1 are as Figure 4 shown. As Figure 4It can be seen that the Mn and Fe elements are evenly distributed throughout the cathode particles without element segregation.

[0155] Example 2

[0156] (1) Lithium iron manganese phosphate precursor Z2 expressed as (Mn 0.7 Fe 0.29 Mg 0.01 )OOH, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide and glucose are mixed with pure water in a molar ratio of 1:1.03:1.02:0.01:0.08, and mixed evenly by mechanical stirring to obtain a second slurry;

[0157] (2) Transfer the above second slurry to a sand mill for grinding to obtain a ground slurry with an average particle size of 0.35 μm; use a two-fluid spray dryer to spray-dry and granulate the ground slurry. Among them, the nozzle size is 1 mm, the spray gun pressure is 0.6 MPa, the inlet air temperature is 230 ± 5 °C, and the outlet air temperature is controlled at 110 ± 5 °C to obtain a spray-dried material with a particle size of 6.9 μm;

[0158] (3) In a nitrogen atmosphere, sinter the above spray-dried material at 680 °C for 10 h, and after screening, obtain lithium iron manganese phosphate cathode material C2 expressed as Li 1.02 Mn 0.7 Fe 0.28 Mg 0.01 Ti 0.01 PO4 / C.

[0159] Among them, the SEM image of the lithium iron manganese phosphate cathode material C2 is similar to Figure 2 . By observing the morphology of the lithium iron manganese phosphate cathode material C2 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C2 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 49 nm, and the average particle size of the secondary spherical particles is 6.9 μm.

[0160] Among them, through the XRD test results, it can be known that the lithium iron manganese phosphate cathode material C2 has an orthorhombic crystal structure.

[0161] Example 3

[0162] (1) Lithium iron manganese phosphate precursor Z3 expressed as (Mn 0.8 Fe 0.19 Cu 0.01 )OOH, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), niobium pentoxide and sucrose are mixed with pure water in a molar ratio of 1:1.03:1.04:0.01:0.09, and mixed evenly by mechanical stirring to obtain a second slurry;

[0163] (2) Transfer the above-mentioned second slurry to a sand mill for grinding to obtain a ground slurry with an average particle size of 0.35 μm; use a two-fluid spray dryer to spray-dry and granulate the ground slurry. Among them, the nozzle size is 1.5 mm, the spray gun pressure is 0.5 MPa, the inlet air temperature is 230 ± 5 °C, and the outlet air temperature is controlled at 110 ± 5 °C to obtain a spray-dried material with a particle size of 8.5 μm;

[0164] (3) In a nitrogen atmosphere, sinter the above-mentioned spray-dried material at 650 °C for 10 h. After screening, a lithium 1.04 Mn 0.8 Fe 0.18 Cu 0.01 Nb 0.01 phosphate lithium manganese iron copper niobate cathode material C3 of PO4 / C is obtained.

[0165] Among them, the SEM image of the lithium manganese iron phosphate cathode material C3 is similar to Figure 2 that. By observing the morphology of the lithium manganese iron phosphate cathode material C3 using a scanning electron microscope, it can be seen that the lithium manganese iron phosphate cathode material C3 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 46 nm, and the average particle size of the secondary spherical particles is 8.1 μm.

[0166] Among them, through the detection results of XRD, it can be known that the lithium manganese iron phosphate cathode material C3 has an orthorhombic crystal structure.

[0167] Example 4

[0168] According to the method of Example 1, the difference is that

[0169] in step (1), the molar ratio of lithium manganese iron phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide, and glucose of 1:1.02:1.04:0.02:0.08 is replaced with the molar ratio of lithium manganese iron phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide, and sucrose of 1:1.02:1.04:0.01:0.08;

[0170] in step (2), the spray gun pressure is replaced with 0.6 MPa, and the outlet air temperature is replaced with 120 ± 5 °C;

[0171] in step (3), the sintering temperature is replaced with 800 °C;

[0172] The remaining conditions are the same, and a lithium 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01Lithium iron manganese phosphate cathode material C4 of PO4 / C.

[0173] Among them, the SEM image of the lithium iron manganese phosphate cathode material C4 is similar to Figure 2 that. By observing the morphology of the lithium iron manganese phosphate cathode material C4 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C4 has a secondary spherical particle structure formed by primary particles. The primary particles are densely bonded. Among them, the average particle size of the primary particles is 325 nm, and the average particle size of the secondary spherical particles is 10.4 μm.

[0174] Among them, through the XRD test results, it can be known that the lithium iron manganese phosphate cathode material C4 has an orthorhombic crystal structure.

[0175] Example 5

[0176] According to the method of Example 1, the difference is that

[0177] in step (1), the molar ratio of lithium iron manganese phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide and glucose of 1:1.02:1.04:0.02:0.08 is replaced with the molar ratio of lithium iron manganese phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide and sucrose of 1:1.02:1.04:0.01:0.08;

[0178] in step (2), the spray gun pressure is replaced with 0.6 MPa, and the air outlet temperature is replaced with 120 ± 5 °C;

[0179] in step (3), the sintering temperature is replaced with 680 °C;

[0180] The other conditions are the same, and the lithium iron manganese phosphate cathode material C5 of the formula Li 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01 PO4 / C is obtained.

[0181] Among them, the SEM image of the lithium iron manganese phosphate cathode material C5 is similar to Figure 2 that. By observing the morphology of the lithium iron manganese phosphate cathode material C5 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C5 has a loose secondary spherical particle structure formed by primary particles. Among them, the average particle size of the primary particles is 50 nm, and the average particle size of the secondary spherical particles is 7.5 μm.

[0182] Among them, through the XRD test results, it can be known that the lithium iron manganese phosphate cathode material C5 has an orthorhombic crystal structure.

[0183] Example 6

[0184] According to the method of Example 1, the difference is that

[0185] in step (1), titanium dioxide is not added,

[0186] and the other conditions are the same, obtaining the lithium 1.04 Mn 0.65 Fe 0.34 Mg 0.01 phosphate iron manganese lithium cathode material C6 of PO4 / C.

[0187] Among them, the SEM image of the lithium phosphate iron manganese lithium cathode material C6 is similar to Figure 2 that. By observing the morphology of the cathode material C6 with a scanning electron microscope, it can be seen that the lithium phosphate iron manganese lithium cathode material C6 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 54 nm, and the average particle size of the secondary spherical particles is 7.4 μm.

[0188] Among them, it can be known from the XRD test results that the lithium phosphate iron manganese lithium cathode material C6 has an orthorhombic crystal structure.

[0189] Example 7

[0190] According to the method of Example 1, the difference is that

[0191] in step (1), the molar ratio of the lithium phosphate iron manganese lithium precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide and glucose is replaced with 1:1.06:1.06:0.02:0.09,

[0192] and the other conditions are the same, obtaining the lithium 1.06 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 phosphate iron manganese lithium cathode material C7 of PO4 / C.

[0193] Among them, the SEM image of the lithium phosphate iron manganese lithium cathode material C7 is similar to Figure 2 that. By observing the morphology of the lithium phosphate iron manganese lithium cathode material C7 with a scanning electron microscope, it can be seen that the lithium phosphate iron manganese lithium cathode material C7 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 62 nm, and the average particle size of the secondary spherical particles is 8.1 μm.

[0194] Among them, it can be known from the XRD test results that the lithium phosphate iron manganese lithium cathode material C7 has an orthorhombic crystal structure.

[0195] Example 8

[0196] According to the method of Example 1, the difference is that

[0197] In step (1), replace the lithium iron manganese phosphate precursor Z1 with the lithium iron manganese phosphate precursor Z4.

[0198] Under the same other conditions, the obtained expression is Li 1.04 Mn 0.65 Fe 0.33 Ti 0.02 PO4 / C lithium iron manganese phosphate cathode material C8.

[0199] Among them, the SEM image of the lithium iron manganese phosphate cathode material C8 is similar to Figure 2 that. By observing the morphology of the cathode material C8 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C8 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 57 nm, and the average particle size of the secondary spherical particles is 7.5 μm.

[0200] Among them, through the XRD test results, it can be known that the lithium iron manganese phosphate cathode material C8 has an orthorhombic crystal structure.

[0201] Example 9

[0202] According to the method of Example 1, the difference is that

[0203] In step (1), replace the lithium iron manganese phosphate precursor Z1 with the lithium iron manganese phosphate precursor Z5.

[0204] Under the same other conditions, the obtained expression is Li 1.04 Mn 0.64 Fe 0.33 Co 0.01 Ti 0.02 PO4 / C lithium iron manganese phosphate cathode material C9.

[0205] Among them, the SEM image of the lithium iron manganese phosphate cathode material C9 is similar to Figure 2 that. By observing the morphology of the cathode material C9 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C9 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 53 nm, and the average particle size of the secondary spherical particles is 7.3 μm.

[0206] Among them, through the XRD test results, it can be known that the lithium iron manganese phosphate cathode material C9 has an orthorhombic crystal structure.

[0207] Example 10

[0208] According to the method of Example 1, the difference is that

[0209] In step (1), replace the lithium iron manganese phosphate precursor Z1 with the lithium iron manganese phosphate precursor Z6,

[0210] with other conditions being the same, to obtain the lithium iron manganese phosphate cathode material C10 with the expression Li 1.04 Mn 0.39 Fe 0.58 Mg 0.01 Ti 0.02 PO4 / C.

[0211] Among them, the SEM image of the lithium iron manganese phosphate cathode material C10 is similar to Figure 2 that. By observing the morphology of the cathode material C10 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C10 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 62 nm, and the average particle size of the secondary spherical particles is 8.5 μm.

[0212] Among them, through the detection results of XRD, it can be known that the lithium iron manganese phosphate cathode material C10 has an orthorhombic crystal structure.

[0213] Example 11

[0214] According to the method of Example 1, the difference is that

[0215] in step (1), replace the lithium iron manganese phosphate precursor Z1 with the lithium iron manganese phosphate precursor Z7,

[0216] with other conditions being the same, to obtain the lithium iron manganese phosphate cathode material C11 with the expression Li 1.04 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 PO4 / C.

[0217] Among them, the SEM image of the lithium iron manganese phosphate cathode material C11 is similar to Figure 2 that. By observing the morphology of the cathode material C11 using a scanning electron microscope, it can be seen that the lithium iron manganese phosphate cathode material C11 has a secondary spherical particle structure formed by primary particles, and the primary particles are densely bonded. Among them, the average particle size of the primary particles is 89 nm, and the average particle size of the secondary spherical particles is 9.2 μm.

[0218] Among them, through the detection results of XRD, it can be known that the lithium iron manganese phosphate cathode material C11 has an orthorhombic crystal structure.

[0219] Comparative Example 1

[0220] According to the method of Example 1, the difference is that in step (1),

[0221] Replace the lithium iron manganese phosphate precursor Z1 with the lithium iron manganese phosphate precursor DZ1, and the molar ratio of the lithium iron manganese phosphate precursor DZ1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide, and glucose is 1:1.03:1.04:0.01:0.08,

[0222] Under the same other conditions, obtain the lithium iron manganese phosphate cathode material DC1 with the formula Li 1.04 Mn 0.65 Fe 0.34 Ti 0.01 PO4 / C.

[0223] Using a scanning electron microscope to observe the morphology of the cathode material DC1, it can be seen that the lithium iron manganese phosphate cathode material DC1 has a secondary spherical particle structure formed by primary particles. The primary particles are densely bonded. Among them, the average particle size of the primary particles is 52 nm, and the average particle size of the secondary spherical particles is 7.9 μm.

[0224] Comparative Example 2

[0225] According to the method of Example 1, the difference is that in step (1),

[0226] Replace the lithium iron manganese phosphate precursor Z1 with iron phosphate and manganese trioxide, and the molar ratio of iron phosphate, manganese trioxide (calculated as Mn), phosphoric acid, lithium carbonate (calculated as Li), titanium dioxide, and glucose is 0.34:0.65:0.65:1.04:0.01:0.08,

[0227] Under the same other conditions, obtain the lithium iron manganese phosphate cathode material DC2 with the formula Li 1.04 Mn 0.65 Fe 0.34 Ti 0.01 PO4 / C.

[0228] Using a scanning electron microscope to observe the morphology of the cathode material DC2, it can be seen that the lithium iron manganese phosphate cathode material DC2 has a secondary spherical particle structure formed by primary particles; among them, the average particle size of the primary particles is 51 nm, and the average particle size of the secondary spherical particles is 7.3 μm.

[0229] Comparative Example 3

[0230] According to the method of Example 1, the difference is that

[0231] In step (1), replace the molar ratio of the lithium iron manganese phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide, and glucose of 1:1.02:1.04:0.02:0.08 with the molar ratio of the lithium iron manganese phosphate precursor Z1, phosphoric acid (calculated as P), lithium carbonate (calculated as Li), titanium dioxide, and sucrose of 1:1.02:1.04:0.01:0.08;

[0232] In step (2), replace the spray drying method with centrifugal spray drying;

[0233] Under the same other conditions, the expression Li 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01 Lithium iron manganese phosphate cathode material DC3 of Li

[0234] Using a scanning electron microscope to observe the morphology of the cathode material DC3, it can be seen that the lithium iron manganese phosphate cathode material DC3 has a loose secondary spherical particle structure formed by primary particles. Among them, the average particle size of the primary particles is 50 nm, and the average particle size of the secondary spherical particles is 16.5 μm.

[0235] Table 2

[0236]

[0237] Note: 1 - Average particle size of the slurry after grinding, μm; 2 - Particle size of the spray-dried material, μm; 3 - Average particle size of the secondary spherical particles of the cathode material, μm; 4 - Average particle size of the primary particles of the cathode material, nm.

[0238] Continued Table 2

[0239] Expression <![CDATA[C content 5 , wt%]]> Example 1 <![CDATA[Li 1.04 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 PO4 / C]]> 2.16 Example 2 <![CDATA[Li 1.02 Mn 0.7 Fe 0.28 Mg 0.01 Ti 0.01 PO4 / C]]> 2.24 Example 3 <![CDATA[Li 1.04 Mn 0.8 Fe 0.18 Cu 0.01 Nb 0.01 PO4 / C]]> 2.42 Example 4 <![CDATA[Li 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01 PO4 / C]]> 2.13 Example 5 <![CDATA[Li 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01 PO4 / C]]> 2.14 Example 6 <![CDATA[Li 1.04 Mn 0.65 Fe 0.34 Mg 0.01 PO4 / C]]> 2.11 Example 7 <![CDATA[Li 1.06 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 PO4 / C]]> 2.18 Example 8 <![CDATA[Li 1.04 Mn 0.65 Fe 0.33 Ti 0.02 PO4 / C]]> 2.09 Example 9 <![CDATA[Li 1.04 Mn 0.64 Fe 0.33 Co 0.01 Ti 0.02 PO4 / C]]> 2.11 Example 10 <![CDATA[Li 1.04 Mn 0.39 Fe 0.58 Mg 0.01 Ti 0.02 PO4 / C]]> 2.17 Example 11 <![CDATA[Li 1.04 Mn 0.64 Fe 0.33 Mg 0.01 Ti 0.02 PO4 / C]]> 2.18 Comparative Example 1 <![CDATA[Li 1.04 Mn 0.65 Fe 0.34 Ti 0.01 PO4 / C]]> 2.14 Comparative Example 2 <![CDATA[Li 1.04 Mn 0.65 Fe 0.34 Ti 0.01 PO4 / C]]> 2.15 Comparative Example 3 <![CDATA[Li 1.04 Mn 0.65 Fe 0.33 Mg 0.01 Ti 0.01 PO4 / C]]> 2.19

[0240] Note: 5 - Content of carbon element in the lithium iron manganese phosphate cathode material, wt%, based on the total weight of the lithium iron manganese phosphate cathode material.

[0241] Continued Table 2

[0242]

[0243]

[0244] Note: 6 - At any position of the particles of the lithium iron manganese phosphate cathode material, Δw = ∣w' - w∣ / w × 100% < 5%, where w' is the Mn / Fe molar ratio at any position and w is the average value of the Mn / Fe ratio in the cathode material;

[0245] 7 - The primary particles of the lithium iron manganese phosphate cathode material satisfy: p / p0 × 100% > 50%, where p is the number of particles of the lithium iron manganese phosphate cathode material whose primary particle size satisfies (D m ±0.2D m ) nm, and D mis the average particle size of the primary particles of the lithium iron manganese phosphate cathode material, and p0 is the total number of primary particles of the lithium iron manganese phosphate cathode material;

[0246] Comparison of the surface area change of the lithium iron manganese phosphate cathode material before and after 2T pressure. Among them, the specific surface area of the lithium iron manganese phosphate cathode material is S0, and the specific surface area after 2T pressure is S1.

[0247] From the results in Table 2, it can be seen that compared with Comparative Examples 1-3, the lithium iron manganese phosphate cathode materials prepared by the method provided by the present invention in Examples 1-11 satisfy the expression Li i Mn 1-x-y-z Fe x M y M′ z Under the premise of PO4 / C, it also has a smaller primary particle size and a suitable agglomerated particle size at the same time, satisfying Δw = ∣w'-w∣ / w×100% < 5%, the primary particles of the cathode material satisfy: p / p0×100% > 50%, and (S1 - S0) / S0×100% ≤ 10%. That is, the lithium iron manganese phosphate cathode material provided by the present invention has the characteristics of high strength and excellent electrochemical performance.

[0248] Test Example

[0249] (1) Preparation of the positive electrode sheet: The lithium iron manganese phosphate cathode materials (C1-C11 and DC1-DC2) obtained in Examples 1-11 and Comparative Examples 1-3, the conductive agent carbon nanotubes, and the NMP solution of the binder PVDF were mixed at a mass ratio of 90:5:5. The specific method is as follows: Grind the dried cathode material and the conductive agent in a mortar for 15 min. After grinding evenly, add the PVDF solution (mass fraction 5%) according to the ratio and stir on a magnetic stirrer for 6 h; Coat the obtained paste-like slurry evenly on the current collector aluminum foil, then dry it in a vacuum drying oven at 60°C for 20 h, and then press it into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm under a pressure of 100 MPa, and put the positive electrode sheet into a vacuum drying oven at 120°C for 12 h.

[0250] (2) Battery assembly: Using a metal lithium sheet with a diameter of 17 mm and a thickness of 1 mm as the negative electrode, a polyethylene porous membrane with an alumina ceramic layer coated on the surface and a thickness of 25 μm as the separator, and selecting an equal mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC) as the electrolyte, assemble the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte into a 2025-type button battery in an Ar gas glove box with a water content and an oxygen content both less than 5 ppm, and respectively prepare lithium ion batteries (A1-A11 and DA1-DA3).

[0251] (3) Electrochemical performance test: The assembled lithium-ion batteries (A1 - A11 and DA1 - DA3) were subjected to charge-discharge tests using a LAND CT2001A charge-discharge instrument from Wuhan Lanbo Electronics Co., Ltd. The charge-discharge voltage range was from 2.5 to 4.4 V. Specific capacity tests were carried out on the assembled lithium-ion batteries at the rates of 0.1C, 1C, and 5C respectively, and the cycle performance test was carried out at the rate of 1C. The test results are shown in Table 3.

[0252] Among them, the charge-discharge curves of the lithium-ion battery A1 assembled with the lithium iron phosphate manganese cathode material C1 prepared in Example 1 and the lithium-ion battery A4 assembled with the lithium iron phosphate manganese cathode material C4 prepared in Example 4 at the rate of 0.1C are as Figure 5 shown, and it can be seen from Figure 5 that compared with Example 4, the lithium-ion battery A1 assembled in Example 1 has a higher capacity retention rate and average voltage retention rate during the cycling process.

[0253] Table 3

[0254]

[0255]

[0256] It can be seen from the data in Table 3 that compared with Comparative Examples 1 - 3, the lithium-ion batteries assembled with the cathode materials prepared in Examples 1 - 11 have higher electrochemical performance, especially good rate performance, high capacity retention rate and average voltage retention rate during the cycling process.

[0257] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A lithium iron manganese phosphate cathode material, characterized in that, The expression of the lithium iron manganese phosphate cathode material is Li i Mn 1-x-y-z Fe x M y M′ z PO4 / C, where 0.09 ≤ x ≤ 0.59, 0 ≤ y ≤ 0.04, 0 ≤ z ≤ 0.04, 0.9 < i ≤ 1.2; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V, and Ti; M′ is selected from at least one of Mg, Ca, Sr, Ti, V, Cr, Co, Ni, Cu, Zn, Zr, Y, Mo, Nb, B, Al, W, La, and Sm; Wherein, at any position of the particles of the lithium iron manganese phosphate cathode material, Δw = ∣w'-w∣ / w×100% < 5%, where w' is the Mn / Fe molar ratio at any position and w is the average value of the Mn / Fe ratio in the cathode material; Wherein, the lithium iron manganese phosphate cathode material has a secondary spherical particle structure formed by primary particles, the average particle size of the secondary spherical particles is 2 - 15 μm, and the average particle size of the primary particles of the lithium iron manganese phosphate cathode material is 5 - 300 nm; the lithium iron manganese phosphate cathode material has an orthorhombic crystal structure.

2. The lithium iron manganese phosphate cathode material according to claim 1, wherein, In the expression of the lithium iron manganese phosphate cathode material, 0.09 ≤ x ≤ 0.59, 0.01 ≤ y ≤ 0.04, 0.01 ≤ z ≤ 0.04, 1 ≤ i ≤ 1.2; and / or, in the expression of the lithium iron manganese phosphate cathode material, M and M′ are different; and / or, in the expression of the lithium iron manganese phosphate cathode material, M is selected from Mg and / or Cu; M′ is selected from at least one of Ti, Nb, and B.

3. The lithium iron manganese phosphate cathode material according to claim 2, wherein, In the expression of the lithium iron manganese phosphate cathode material, 0.19 ≤ x ≤ 0.39, 0.01 ≤ y ≤ 0.02, 0.01 ≤ z ≤ 0.02, 1 ≤ i ≤ 1.

1.

4. The lithium iron manganese phosphate cathode material according to claim 1, wherein, Based on the total weight of the lithium iron manganese phosphate cathode material, the content of carbon element in the lithium iron manganese phosphate cathode material is 0.5 - 5 wt%.

5. The lithium iron manganese phosphate cathode material according to claim 4, wherein, Based on the total weight of the lithium iron manganese phosphate cathode material, the content of carbon element in the lithium iron manganese phosphate cathode material is 1 - 3 wt%.

6. The lithium iron manganese phosphate cathode material according to claim 5, wherein Based on the total weight of the lithium iron manganese phosphate cathode material, the content of carbon element in the lithium iron manganese phosphate cathode material is 1.8 - 2.5 wt%.

7. The lithium iron manganese phosphate cathode material according to claim 1, the average particle size of the secondary spherical particles is 4 - 9 μm; the average particle size of the primary particles of the lithium iron manganese phosphate cathode material is 40 - 120 nm.

8. The lithium iron manganese phosphate cathode material according to any one of claims 1-7, wherein, The primary particles of the lithium iron manganese phosphate cathode material satisfy: p / p0×100% > 50%, where p is the number of particles of the lithium iron manganese phosphate cathode material with a particle size satisfying (D m ±0.2D m ) nm, D m is the average particle size of the primary particles of the lithium iron manganese phosphate cathode material, and p0 is the total number of particles of the primary particles of the lithium iron manganese phosphate cathode material; and / or, the specific surface area of the lithium iron manganese phosphate cathode material is S0, and the specific surface area after 2T pressure is S1, where (S1 - S0) / S0×100% ≤ 10%.

9. The lithium iron manganese phosphate cathode material according to claim 8, wherein, The specific surface area of the lithium iron manganese phosphate cathode material is S0, and the specific surface area after 2T pressure is S1, where (S1 - S0) / S0×100% ≤ 5%.

10. The preparation method of the lithium iron manganese phosphate cathode material according to claim 1, characterized in that, The preparation method includes: (1) Provide a lithium iron manganese phosphate precursor with the expression of (Mn 1-α-β Fe α M β )OOH, where 0.09 ≤ α ≤ 0.59, 0 ≤ β ≤ 0.04; M is selected from at least one of Mg, Cu, Co, Ni, Zn, V, and Ti; (2) In the presence of a solvent, mixing and homogenizing the lithium iron manganese phosphate precursor, phosphorus source, lithium source, M′ source, and carbon source to obtain a first slurry; (3) Grinding the first slurry, and spray-drying the obtained ground slurry to obtain a spray-dried material; (4) Sintering the spray-dried material in a first non-oxidizing atmosphere to obtain the lithium iron manganese phosphate cathode material; Among them, the average particle size of the primary particles of the lithium iron manganese phosphate precursor is 10 - 500 nm, and the specific surface area of the lithium iron manganese phosphate precursor is 10 - 50 m 2 / g; In step (3), the average particle size of the ground slurry is 0.1 - 0.6 μm.

11. The preparation method according to claim 10, wherein, In step (1), in the expression of the lithium iron manganese phosphate precursor, 0.09 ≤ α ≤ 0.59, 0.01 ≤ β ≤ 0.04; and / or, in the expression of the lithium iron manganese phosphate precursor, M is selected from Mg and / or Cu; and / or, the average particle size of the primary particles of the lithium iron manganese phosphate precursor is 50-200 nm; the specific surface area of the lithium iron manganese phosphate precursor is 20-40 m 2 / g; and / or, the lithium iron manganese phosphate precursor has a hexagonal crystal structure; And / or, the lithium iron manganese phosphate precursor is prepared by the following method: (a) providing a mixed metal salt solution containing a manganese source, an iron source, and an optional M source; providing a complexing agent solution and a precipitating agent solution; (b) in a second non-oxidizing atmosphere, adding the mixed metal salt solution, the complexing agent solution, and the precipitating agent solution into water for co-precipitation reaction to obtain a second slurry; (c) performing solid-liquid separation and washing on the second slurry to obtain the lithium iron manganese phosphate precursor.

12. The preparation method according to claim 11, wherein, In step (1), in the expression of the lithium iron manganese phosphate precursor, 0.19 ≤ α ≤ 0.39 and 0.01 ≤ β ≤ 0.

02.

13. The preparation method according to claim 11, wherein, In step (a), the molar ratio of the manganese source in terms of Mn, the iron source in terms of Fe, and the M source in terms of M satisfies: n(Mn):n(Fe):n(M), where 0.37 ≤ n(Mn) ≤ 0.91, 0.09 ≤ n(Fe) ≤ 0.59, and 0 ≤ n(M) ≤ 0.04; And / or, the concentration of total metal ions in the mixed metal salt solution is 0.5 - 3 mol / L; the concentration of the complexing agent in the complexing agent solution is 2 - 14 mol / L; the concentration of the precipitating agent in the precipitating agent solution is 2 - 10 mol / L; And / or, in step (b), the mixed metal salt solution, the complexing agent solution, and the precipitating agent solution are added into water in a co-current manner; And / or, the co-precipitation reaction is carried out under stirring, and the conditions of the co-precipitation reaction include: rotation speed of 500 - 1000 rpm, pH of 8 - 12, temperature of 30 - 90 °C, and time of 0.1 - 5 h; And / or, in step (c), after drying the washed product, the lithium iron manganese phosphate precursor is obtained; the drying temperature is 80 - 150 °C and the time is 1 - 10 h.

14. The preparation method according to claim 13, wherein In step (a), the molar ratio of the manganese source in terms of Mn, the iron source in terms of Fe, and the M source in terms of M satisfies: n(Mn):n(Fe):n(M), where 0.37 ≤ n(Mn) ≤ 0.9, 0.09 ≤ n(Fe) ≤ 0.59, and 0.01 ≤ n(M) ≤ 0.

04.

15. The preparation method according to claim 14, wherein, In step (a), the molar ratio of the manganese source in terms of Mn, the iron source in terms of Fe, and the M source in terms of M satisfies: n(Mn):n(Fe):n(M), where 0.59 ≤ n(Mn) ≤ 0.8, 0.19 ≤ n(Fe) ≤ 0.39, and 0.01 ≤ n(M) ≤ 0.

02.

16. The preparation method according to claim 10, wherein In step (2), the molar ratio of the lithium iron manganese phosphate precursor, the phosphorus source in terms of P, the lithium source in terms of Li, the M' source, and the carbon source is 1:0.95 - 1.1:1 - 1.1:0.01 - 0.04:0.05 - 0.15; And / or, the phosphorus source is selected from at least one of phosphoric acid, ammonium dihydrogen phosphate, and lithium dihydrogen phosphate; And / or, the lithium source is selected from at least one of lithium oxide, lithium hydroxide, lithium chloride, lithium nitrate, lithium nitrite, lithium formate, lithium acetate, lithium oxalate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium citrate; And / or, the M' source is selected from at least one of sulfates, nitrates, acetates, oxides, and acids containing M'; And / or, the carbon source is selected from at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

17. The preparation method according to claim 16, wherein, In step (2), the molar ratio of the lithium iron manganese phosphate precursor, the phosphorus source calculated as P, the lithium source calculated as Li, the M' source, and the carbon source is 1:1.02 - 1.07:1.01 - 1.06:0.01 - 0.02:0.07 - 0.12; And / or, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and lithium chloride; And / or, the M' source is selected from at least one of titanium dioxide, niobium pentoxide, and boric acid; And / or, the carbon source is selected from at least one of glucose, sucrose, starch, and polyethylene glycol.

18. The preparation method according to any one of claims 10-17, wherein, The spray drying is two-fluid spray drying, wherein the nozzle size is 0.5 - 5 mm, the spray gun pressure is 0.2 - 1 MPa, the inlet air temperature is 150 - 300 °C, and the outlet air temperature is 80 - 180 °C; And / or, the particle size of the spray-dried material is 2 - 15 μm; And / or, in step (4), the sintering conditions include: the temperature is 600 - 900 °C; the time is 5 - 20 h.

19. The preparation method according to claim 18, wherein, The sintering conditions include: the temperature is 600 - 750 °C; the time is 8 - 12 h.

20. An electrode material, the electrode material containing an active material, a conductive agent, and a binder, characterized in that, The active material is the lithium iron manganese phosphate cathode material according to any one of claims 1 - 9.

21. An electrode, the electrode comprising a current collector, and an electrode material coated and / or filled on the current collector, characterized in that, The electrode material is the electrode material according to claim 20.

22. A lithium-ion battery, characterized in that, The lithium ion battery includes: the electrode according to claim 21 as the positive electrode.

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