A lithium iron manganese phosphate precursor, a lithium iron manganese phosphate material, and a preparation method and application thereof

Abstract

The application discloses a lithium manganese iron phosphate precursor, a lithium manganese iron phosphate material and a preparation method and application thereof. The lithium manganese iron phosphate precursor comprises a core, a core layer and a shell layer coated on the outer surface of the core. The core is an ion conductive agent. The core layer is a manganese-rich layer, and the shell layer is an iron-rich layer. The mass of the core, the core layer and the shell layer accounts for 0.50-8.00%, 52.00-69.00% and 23.00-47.50% of the mass of the lithium manganese iron phosphate precursor respectively. The lithium manganese iron phosphate precursor has a specific structure, which comprises a core, a core layer and a shell layer. The specific structure can effectively inhibit Mn dissolution and promote lithium ion diffusion, and provides a stable environment for lithium ion diffusion, thereby being beneficial to improving the conductivity and structural stability of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode materials, and more particularly to a lithium manganese iron phosphate precursor, a lithium manganese iron phosphate material, and a preparation method and application thereof. BACKGROUND

[0002] The olivine-type lithium iron phosphate (LiFePO4) compound has low price, high thermal stability, excellent safety performance, and outstanding cycle life, and is one of the most promising positive electrode materials at present, especially in the field of electric vehicles or energy storage batteries. However, the LiFePO4 material inherently has poor electronic conductivity and ionic conductivity, which will affect its electrochemical performance. The formation of a lithium manganese iron phosphate (LiMn x Fe 1-x PO4) solid solution by partially substituting Mn for Fe can enhance the electronic conductivity, has a higher voltage platform and energy density. In terms of significant improvement in electrochemical performance, long cycle life, and simple synthesis process, the lithium manganese iron phosphate material is considered to be one of the most promising high-energy and power density positive electrode materials for the next generation of lithium-ion batteries.

[0003] With the development of the field of electric vehicles and energy storage batteries, and the increasing demand for the performance of positive electrode materials, higher requirements are put forward for the electrical conductivity of the lithium manganese iron phosphate material. Therefore, it is of great economic value to develop a lithium manganese iron phosphate precursor capable of improving the electrical conductivity of the lithium manganese iron phosphate material. SUMMARY

[0004] The present application aims to solve the problems of the prior art, and provides a lithium manganese iron phosphate precursor, a lithium manganese iron phosphate material, and a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0006] In a first aspect, the present application provides a lithium manganese iron phosphate precursor, which comprises an inner core, an inner core layer, and an outer shell layer from inside to outside.

[0007] The inner core is an ionic conductive agent, and the mass percentage of the inner core in the lithium manganese iron phosphate precursor is 0.50-8.00%.

[0008] The inner core layer contains Mn elements, Fe elements, M1 elements and P elements, the M1 elements are doped metal elements, the molar ratio of the Mn elements, the Fe elements and the M1 elements is Mn:Fe:M1=x:(1-x-y):y, 0.5<=x<1, 0

[0009] The outer shell layer contains Mn elements, Fe elements, M2 elements and P elements, the M2 elements are doped metal elements, the molar ratio of the Mn elements, the Fe elements and the M2 elements is Mn:Fe:M2=a:(1-a-b):b, 0

[0010] The specific structure of the lithium manganese iron phosphate precursor can effectively inhibit Mn elution and promote lithium ion diffusion, and provides a stable environment for lithium ion diffusion, thereby facilitating the improvement of the conductivity and structural stability of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

[0011] In addition, when the mass percentage of the inner core in the lithium manganese iron phosphate precursor is too large, the active material of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor will decrease in quantity, which will affect the energy density of the lithium ion battery and hinder the diffusion of lithium ions, and is not conducive to the improvement of the conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

[0012] In addition, in the present application, the inner core layer and the shell layer of the lithium iron manganese phosphate precursor can be respectively controlled by adding appropriate amounts of doping metal elements M1 and M2, so as to respectively control the internal crystal structure of the inner core layer and the shell layer, which is helpful to improve the stability of the specific structure of the lithium iron manganese phosphate precursor, thereby protecting and promoting the diffusion of lithium ions, and further improving the conductivity of the lithium iron manganese phosphate material prepared by using the lithium iron manganese phosphate precursor. When the amounts of the doping metal elements M1 and M2 added in the inner core layer and the shell layer are too much, the doping metal elements M1 and M2 will destroy the internal crystal structure of the inner core layer and the shell layer, which is not conducive to maintaining the stability of the specific structure of the lithium iron manganese phosphate precursor, thereby not conducive to improving the conductivity and structural stability of the lithium iron manganese phosphate material prepared by using the lithium iron manganese phosphate precursor. At the same time, the doping metal elements M1 and M2 will gather at the grain boundaries, which may have an adverse effect on the performance of the lithium iron manganese phosphate material. When the amounts of the doping metal elements M1 and M2 added in the inner core layer and the shell layer are too little, the doping metal elements M1 and M2 cannot well control the internal crystal structure of the inner core layer and the shell layer, which is not conducive to constructing a stable specific structure of the lithium iron manganese phosphate precursor, and cannot promote the diffusion of lithium ions, which is not conducive to improving the conductivity of the lithium iron manganese phosphate material prepared by using the lithium iron manganese phosphate precursor.

[0013] Preferably, the inner core layer further contains O elements; and in the inner core layer, the molar ratio of the P elements and O elements is P:O = 1:4.

[0014] Preferably, the shell layer further contains O elements; and in the shell layer, the molar ratio of the P elements and O elements is P:O = 1:4.

[0015] Preferably, the mass percentage of the inner core layer in the mass of the lithium iron manganese phosphate precursor is 57.00-62.00%.

[0016] More preferably, the mass percentage of the inner core layer in the mass of the lithium iron manganese phosphate precursor is 57.26-61.93%.

[0017] Preferably, the mass percentage of the shell layer in the mass of the lithium iron manganese phosphate precursor is 34.00-38.00%.

[0018] More preferably, the mass percentage of the shell layer in the mass of the lithium iron manganese phosphate precursor is 34.50-37.80%, and specifically can be 34.74-37.57%.

[0019] Preferably, in the inner core layer, the molar ratio of the Mn elements, Fe elements and M1 elements is Mn:Fe:M1 = (0.500-0.948):(0.050-0.498):(0.002-0.050).

[0020] More preferably, in the core layer, the molar ratio of the Mn element, the Fe element, the M1 element is Mn:Fe:M1 = 0.900:(0.050-0.098):(0.002-0.050).

[0021] Preferably, in the shell layer, the molar ratio of the Mn element, the Fe element, the M2 element is Mn:Fe:M2 = (0.100-0.400):(0.550-0.898):(0.002-0.050).

[0022] More preferably, in the shell layer, the molar ratio of the Mn element, the Fe element, the M2 element is Mn:Fe:M2 = 0.100:(0.850-0.898):(0.002-0.050).

[0023] Preferably, the M1 element and the M2 element are each independently selected from at least one of Ti, Mg, Al, Ni, Nb, Co, Cu, and Si.

[0024] Preferably, the ion conductive agent is at least one of LATP (lithium aluminum titanium phosphate), LAGP (lithium aluminum germanium phosphate), and LLTO (lithium lanthanum titanium oxide).

[0025] More preferably, the LATP (lithium aluminum titanium phosphate) has a general chemical composition of Li 1+c Al c Ti 2-c (PO4)3, 0

[0026] More preferably, the LAGP (lithium aluminum germanium phosphate) has a general chemical composition of Li 1+d Al d Ge 2-d (PO4)3, 0

[0027] More preferably, the LLTO (lithium lanthanum titanium oxide) has a general chemical composition of Li 3e La 2 / 3-e Ti f T 1-f O3, 0

[0028] In the present application, the LATP (lithium aluminum titanium phosphate), the LAGP (lithium aluminum germanium phosphate), and the LLTO (lithium lanthanum titanium oxide) can be obtained commercially or prepared by conventional preparation methods in the art, and the present application provides a preparation method for each of the LATP, the LAGP, and the LLTO, specifically:

[0029] The preparation method of the LATP (lithium aluminum titanium phosphate) is as follows:

[0030] The Li source, the Al source, the Ti source and the P source are weighed according to the molar ratio, mixed, and heat-treated at 800-950 DEG C for 6-20 hours to obtain the LATP; wherein the Li source can be but is not limited to lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, etc., the Al source can be but is not limited to aluminum oxide, aluminum nitrate, aluminum phosphate, aluminum isopropyl alcohol, etc., the Ti source can be but is not limited to titanium oxide, tetrabutyl titanate, titanium carbide, titanium pyrophosphate, etc., and the P source can be but is not limited to ammonium dihydrogen phosphate, diaphosphorus pentoxide, titanium pyrophosphate, etc.

[0031] The preparation method of the LAGP (lithium aluminum germanium phosphate) is as follows:

[0032] The Li source, the Al source, the Ge source and the P source are weighed according to the molar ratio, mixed, and heat-treated at 700-900 DEG C for 6-20 hours to obtain the LAGP; wherein the Li source can be but is not limited to lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, etc., the Al source can be but is not limited to aluminum oxide, aluminum nitrate, aluminum phosphate, aluminum isopropyl alcohol, etc., the Ge source can be but is not limited to germanium dioxide, germanium monoxide, titanium carbide, titanium pyrophosphate, etc., and the P source can be but is not limited to ammonium dihydrogen phosphate, diaphosphorus pentoxide, titanium pyrophosphate, etc.

[0033] The preparation method of the LLTO (lanthanum lithium titanate) is as follows:

[0034] The Li source, the La source, the Ti source and the T source are weighed according to the molar ratio, mixed, and heat-treated at 1000-1200 DEG C for 6-20 hours to obtain the LLTO; wherein the Li source can be but is not limited to lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, etc., the La source can be but is not limited to lanthanum oxide, lanthanum fluoride, lanthanum acetate, etc., the Ti source can be but is not limited to titanium oxide, tetrabutyl titanate, titanium carbide, titanium pyrophosphate, etc., and the T source is at least one of oxides, carbonates of Nb, W, Hf, Ru, Mo, Nd, Ba, Ga, In, Ge, Sn, Sb, Se.

[0035] In the present application, "weighed according to the molar ratio" means that the elements in the chemical composition general formula are weighed according to the molar ratio, for example, the chemical composition general formula of the LATP (lithium aluminum titanium phosphate) is Li 1+c Al c Ti 2-c (PO4)3, and in the preparation method of the LATP, "weighed according to the molar ratio" specifically means that the Li source, the Al source, the Ti source and the P source are weighed according to the molar ratio of the elements Li, Al, Ti and P, i.e. (1+c):c:(2-c):3.

[0036] In the present application, the D50 particle size of the ion conductive agent is in nanometer size, preferably 20-200 nm, which can be achieved by grinding and / or ball milling and / or sand milling LATP (lithium aluminum titanium phosphate), LLTO (lithium lanthanum titanate), LAGP (lithium aluminum germanium phosphate) to a D50 particle size in nanometer size. When ball milling is used to achieve a D50 particle size of 20-200 nm of the ion conductive agent, the rotation speed of the ball mill is 100-700 rpm, and the ball milling time is 2-24 h.

[0037] In a second aspect, the present application provides a preparation method of a lithium manganese iron phosphate precursor, which comprises the following steps:

[0038] S1. Mixing the ion conductive agent and the manganese source, iron source, M1 source, and phosphorus source required for the inner core layer, and reacting under the condition of pH = 2-12, aging to obtain a precursor containing the ion conductive agent;

[0039] S2. Mixing the precursor containing the ion conductive agent obtained in step S1 and the manganese source, iron source, M2 source, and phosphorus source required for the outer shell layer, and reacting under the condition of pH = 2-12, aging to obtain a lithium manganese iron phosphate precursor.

[0040] Preferably, in step S1, the molar ratio of Mn element of the manganese source, Fe element of the iron source, and M1 element of the M1 source is Mn:Fe:M1 = x:(1-x-y):y, 0.5≤x<1, 0

[0041] More preferably, in step S1, the molar ratio of Mn element of the manganese source, Fe element of the iron source, and M1 element of the M1 source is Mn:Fe:M1 = (0.500-0.948):(0.050-0.498):(0.002-0.050).

[0042] Further preferably, in step S1, the molar ratio of Mn element of the manganese source, Fe element of the iron source, and M1 element of the M1 source is Mn:Fe:M1 = 0.900:(0.050-0.098):(0.002-0.050).

[0043] Preferably, in step S2, the molar ratio of the Mn element of the manganese source, the Fe element of the iron source, and the M2 element of the M2 source is Mn:Fe:M2=a:(1-a-b):b, 0

[0044] More preferably, in step S2, the molar ratio of the Mn element of the manganese source, the Fe element of the iron source, and the M2 element of the M2 source is Mn:Fe:M2=(0.100-0.400):(0.550-0.898):(0.002-0.050).

[0045] More preferably, in step S2, the molar ratio of the Mn element of the manganese source, the Fe element of the iron source, and the M2 element of the M2 source is Mn:Fe:M2=(0.100-0.400):(0.550-0.898):(0.002-0.050).

[0046] Preferably, in step S1, the ion conductive agent is an ion conductive agent suspension; the mass fraction of the ion conductive agent in the ion conductive agent suspension is 0.1-30%, specifically 0.8-13.5% or 0.81-13.07%; the solvent of the ion conductive agent suspension is at least one of water, anhydrous ethanol, methanol, and acetone.

[0047] Preferably, in step S1 and / or S2, the pH regulator is at least one of ammonia, sodium hydroxide, potassium hydroxide, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, and citric acid.

[0048] More preferably, the concentration of the ammonia is 0.1-15 mol / L, specifically 2-5 mol / L.

[0049] Preferably, in step S1 and / or S2, the pH range is 4-7.

[0050] Preferably, at least one of the following (1)-(5) is included:

[0051] (1) In step S1 and / or S2, the manganese source is at least one of manganese sulfate, manganese oxalate, manganese phosphate, and manganese nitrate.

[0052] (2) In step S1 and / or S2, the iron source is at least one of ferrous sulfate, ferrous oxalate, ferrous nitrate, and ferrous chloride.

[0053] (3) In step S1, the M1 source is at least one of oxalate, chloride, nitrate, sulfate, phosphate, hydroxide of Ti, Mg, Al, Ni, Nb, Co, Cu, Si respectively;

[0054] (4) In step S2, the M2 source is at least one of oxalate, chloride, nitrate, sulfate, phosphate, hydroxide of Ti, Mg, Al, Ni, Nb, Co, Cu, Si respectively;

[0055] (5) In step S1 and / or S2, the phosphorus source is at least one of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate.

[0056] Preferably, in step S1 and / or S2, the temperature of the reaction is 20-80℃.

[0057] Preferably, in step S1 and / or S2, the reaction is carried out under the condition of rotation speed of 100-800rpm.

[0058] Preferably, in step S1 and / or S2, the temperature of the aging is 20-80℃ and the time is 2-12h.

[0059] Preferably, in step S2, after the aging, further comprising filtering, washing, drying.

[0060] Preferably, in step S1 and / or S2, the reaction and / or the aging is carried out under the protection of inert gas.

[0061] More preferably, the inert gas is at least one of nitrogen, helium, neon, argon.

[0062] In a third aspect, the application provides application of the above-mentioned lithium iron manganese phosphate precursor in lithium iron manganese phosphate material.

[0063] In a fourth aspect, the application provides a preparation method of lithium iron manganese phosphate material, which comprises the following steps:

[0064] Mixing the lithium iron manganese phosphate precursor, lithium source, carbon source and phosphorus source, sintering, to obtain the lithium iron manganese phosphate material.

[0065] In the preparation method of the lithium iron manganese phosphate material, the lithium source penetrates into the inner core layer and the shell layer of the lithium iron manganese phosphate precursor during sintering, and finally obtains the lithium iron manganese phosphate material with the inner core containing ion conductive agent, the inner core layer containing manganese-rich and iron-poor lithium iron manganese phosphate, the shell layer containing manganese-poor and iron-rich lithium iron manganese phosphate, and the surface of the shell layer being wrapped with carbon.

[0066] The existence of the lithium manganese iron phosphate precursor lays the foundation for the structure of the lithium manganese iron phosphate material, and the specific structure of the lithium manganese iron iron phosphate precursor can effectively inhibit the dissolution of Mn and promote the diffusion of lithium ions, and provide a stable environment for the diffusion of lithium ions, thereby improving the conductivity and structural stability of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

[0067] Preferably, the sintering is carried out in a protective atmosphere.

[0068] More preferably, the protective atmosphere is at least one of nitrogen, argon, hydrogen, helium, neon.

[0069] Preferably, at least one of the following (1)-(6) is included:

[0070] (1) The ratio of the total amount of substance of metal elements in the lithium manganese iron phosphate precursor, the amount of substance of Li element in the lithium source, and the total amount of substance of P element in the mixture is metal element: Li: P = 1: (1.00-1.10): (1.00-1.10), wherein the total amount of substance of metal elements in the lithium manganese iron phosphate precursor refers to the total amount of substance of Mn elements, Fe elements, M1 elements, M2 elements in the lithium manganese iron phosphate precursor, and the total amount of substance of P elements in the mixture refers to the total amount of substance of P elements in the lithium manganese iron phosphate precursor, P elements in the lithium source, and P elements in the phosphorus source;

[0071] (2) The mass of the carbon source accounts for 1.5-6.0% of the total mass of the lithium manganese iron phosphate precursor, the lithium source, the phosphorus source, and the carbon source;

[0072] (3) The sintering temperature is 500-900℃, and the time is 6-20h;

[0073] (4) The lithium source is at least one of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate;

[0074] (5) The carbon source is at least one of sucrose, glucose, citric acid, fructose, starch, maltose, lactose, ascorbic acid, polypropylene, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), carbon nanotubes (CNT), and graphene;

[0075] (6) The phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0076] The commonly used sucrose, glucose, citric acid, fructose, starch, maltose, lactose, ascorbic acid, polypropylene, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), carbon nanotubes (CNT), and graphene can be used in the present application.

[0077] More preferably, the carbon source is glucose and carbon nanotubes in a mass ratio of (0.1-10):1.

[0078] More preferably, the carbon source is glucose and PEG in a mass ratio of (0.1-10):1.

[0079] In a fifth aspect, the present application provides a lithium iron manganese phosphate material prepared by the method of the fourth aspect.

[0080] In a sixth aspect, the present application provides an electrode material comprising the lithium iron manganese phosphate material of the fifth aspect, a conductive agent and a binder.

[0081] In the present application, the conductive agent and the binder are conventional conductive agents and binders in the art.

[0082] In a seventh aspect, a method for preparing an electrode material comprises the following steps:

[0083] Mixing the lithium iron manganese phosphate material of the fifth aspect, the conductive agent and the binder to obtain the electrode material.

[0084] In an eighth aspect, the present application provides an electrode comprising a current collector, wherein the surface of the current collector is provided with the electrode material of the seventh aspect.

[0085] In the present application, conventional current collectors in the art can be used in the present application.

[0086] In a ninth aspect, the present application provides a method for preparing an electrode comprising the following steps:

[0087] Coating the electrode material of the seventh aspect on a current collector to obtain the electrode.

[0088] In a tenth aspect, the present application provides a lithium ion battery comprising an electrode group and an electrolyte, wherein the electrode group and the electrolyte are sealed in a battery shell; the electrode group comprises a positive electrode, a separator and a negative electrode, wherein the separator is arranged between the positive electrode and the negative electrode; the positive electrode is the electrode of the eighth aspect.

[0089] In the present application, the separator, the electrolyte and the negative electrode are conventional separators, electrolytes and negative electrodes in the art.

[0090] Compared with the prior art, the present application has the following beneficial effects:

[0091] The lithium iron manganese phosphate precursor of the present application has a specific structure comprising a core, a core layer and a shell layer, which can effectively inhibit Mn dissolution and promote lithium ion diffusion, and provide a stable environment for lithium ion diffusion, thereby being beneficial to improving the conductivity and structural stability of the lithium iron manganese phosphate material prepared by using the lithium iron manganese phosphate precursor.

[0092] In addition, when the mass percentage of the core of the inner core to the mass of the lithium manganese iron phosphate precursor is too large, the active material of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor will be reduced in quantity, which will affect the energy density of the lithium ion battery and hinder the diffusion of lithium ions, and is not conducive to improving the electrical conductivity of the lithium manganese iron iron phosphate material prepared by using the lithium manganese iron phosphate precursor. When the mass percentage of the core of the inner core to the mass of the lithium manganese iron phosphate precursor is too small, the specific structure of the lithium manganese iron phosphate precursor cannot well promote the diffusion of lithium ions, and is not conducive to improving the electrical conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

[0093] In addition, in the present application, the inner core layer and the shell layer of the lithium manganese iron phosphate precursor can respectively control the internal crystal structure of the inner core layer and the shell layer by adding appropriate amounts of doping metal elements M1 and M2, which is helpful to improve the stability of the specific structure of the lithium manganese iron phosphate precursor, thereby protecting and promoting the diffusion of lithium ions, and is conducive to improving the electrical conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor. When the amounts of the doping metal elements M1 and M2 added to the inner core layer and the shell layer are too much, the doping metal elements M1 and M2 will destroy the internal crystal structure of the inner core layer and the shell layer, which is not conducive to maintaining the stability of the specific structure of the lithium manganese iron phosphate precursor, thereby not conducive to improving the electrical conductivity and structural stability of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor. At the same time, the doping metal elements M1 and M2 will gather at the grain boundaries, which may have an adverse effect on the performance of the lithium manganese iron phosphate material. When the amounts of the doping metal elements M1 and M2 added to the inner core layer and the shell layer are too small, the doping metal elements M1 and M2 cannot well control the internal crystal structure of the inner core layer and the shell layer, which is not conducive to constructing a stable specific structure of the lithium manganese iron phosphate precursor, cannot promote the diffusion of lithium ions, and is not conducive to improving the electrical conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor. BRIEF DESCRIPTION OF DRAWINGS

[0094] Figure 1 It is a structure schematic diagram of the lithium manganese iron phosphate precursor of Example 1.

[0095] Figure 2 It is a SEM and EDS diagram of the lithium manganese iron phosphate precursor of Example 1. Figures A and B are SEM diagrams of the lithium manganese iron phosphate precursor of Example 1, and Figures C-E are EDS diagrams of manganese elements, iron elements and phosphorus elements in the lithium manganese iron phosphate precursor, respectively.

[0096] Figure 3 It is a SEM diagram of the lithium manganese iron phosphate material of Application Example 1.

[0097] Figure 4 It is a charge-discharge curve diagram of the lithium manganese iron phosphate material of Application Example 1. DETAILED DESCRIPTION

[0098] In order to better illustrate the purposes, technical solutions and advantages of the present application, the present application will be further described below in conjunction with specific examples.

[0099] The experimental methods not specified in the following example embodiments are generally in accordance with the conventional conditions in the art or in accordance with the conditions suggested by the manufacturers; the raw materials, reagents and the like used, if not specifically stated, are all raw materials and reagents that can be obtained through commercial channels such as conventional markets.

[0100] In the examples, comparative examples, application examples and comparative application examples of the present application, the reagents are used as follows:

[0101] The chemical composition of LATP (lithium aluminum titanium phosphate) has a general formula of Li 1.4 Al 0.4 Ti 1.6 (PO4)3, and the preparation method is as follows: lithium carbonate, aluminum oxide, titanium oxide and ammonium dihydrogen phosphate are weighed according to the molar ratio (i.e., the molar ratio of lithium carbonate, aluminum oxide, titanium oxide and ammonium dihydrogen phosphate is 0.7:0.2:1.6:3), mixed, heat treated at 800℃ for 15h, to obtain LATP; 1000g of the LATP is added into 1500mL of pure water, ball milled at a speed of 600rpm for 12h, dried, and then ground and broken, to obtain LATP with a D50 particle size of 100nm;

[0102] The chemical composition of LAGP (lithium aluminum germanium phosphate) has a general formula of Li 1.4 Al 0.4 Ge 1.6 (PO4)3, and the preparation method is as follows: lithium carbonate, aluminum oxide, germanium dioxide and ammonium dihydrogen phosphate are weighed according to the molar ratio (i.e., the molar ratio of lithium carbonate, aluminum oxide, germanium dioxide and ammonium dihydrogen phosphate is 0.7:0.2:1.6:3), mixed, heat treated at 900℃ for 8h, to obtain LAGP; 1000g of the LAGP is added into 1500mL of pure water, ball milled at a speed of 600rpm for 12h, dried, and then ground and broken, to obtain LAGP with a D50 particle size of 100nm;

[0103] The chemical composition of LLTO (lithium lanthanum titanate) has a general formula of Li 0.3 La 0.567 TiO3, and the preparation method is as follows: lithium carbonate, lanthanum oxide and titanium oxide are weighed according to the molar ratio (i.e., the molar ratio of lithium carbonate, lanthanum oxide and titanium oxide is 0.15:0.28:1), mixed, heat treated at 1100℃ for 12h, to obtain LLTO; 1000g of the LLTO is added into 1500mL of pure water, ball milled at a speed of 600rpm for 12h, dried, and then ground and broken, to obtain LLTO with a D50 particle size of 100nm;

[0104] Glucose, D769078 (model or catalog number), Macron (manufacturer);

[0105] Carbon nanotubes (CNT), G991390 (model or catalog number), Macron (manufacturer);

[0106] Polyethylene glycol (PEG), PEG-800 (model or catalog number), Wanhua Chemical (manufacturer);

[0107] Sucrose, S818045 (model or catalog number), Macron (manufacturer);

[0108] In the present application, the D50 particle size is measured by a Malvern Panalytical laser D50 particle size instrument Mastersizer 3000.

[0109] Example 1

[0110] The present embodiment provides a lithium manganese iron phosphate precursor, a structural schematic diagram of which is shown as Figure 1 The lithium manganese iron phosphate precursor comprises, from inside to outside, a core core, a core layer, and a shell layer.

[0111] The core core is an ion conductive agent LATP, and the mass percentage of the core core in the lithium manganese iron phosphate precursor is 3.00%.

[0112] The core layer contains Mn elements, Fe elements, Mg elements, P elements, and O elements, the molar ratio of the Mn elements, Fe elements, and Mg elements is Mn:Fe:Mg = 0.900:0.095:0.005, the ratio of the total amount of substance of the Mn elements, Fe elements, and Mg elements to the amount of substance of the P elements is (Mn+Fe+Mg):P = 1:1, the molar ratio of the P elements and O elements is P:O = 1:4, and the mass percentage of the core layer in the lithium manganese iron phosphate precursor is 60.37%.

[0113] The shell layer contains Mn elements, Fe elements, Ti elements, P elements, and O elements, the molar ratio of the Mn elements, Fe elements, and Ti elements is Mn:Fe:Ti = 0.100:0.895:0.005, the ratio of the total amount of substance of the Mn elements, Fe elements, and Ti elements to the amount of substance of the P elements is (Mn+Fe+Ti):P = 1:1, the molar ratio of the P elements and O elements is P:O = 1:4, and the mass percentage of the shell layer in the lithium manganese iron phosphate precursor is 36.63%.

[0114] The preparation method of the above lithium manganese iron phosphate precursor comprises the following steps:

[0115] S1. In 6.30 L of pure water, 11.340 mol of manganese sulfate (MnSO4), 1.200 mol of ferrous sulfate (FeSO4), and 0.063 mol of magnesium sulfate (MgSO4, M1 source) were added to prepare solution A1; in 6.30 L of pure water, 12.603 mol of ammonium dihydrogen phosphate (NH4H2PO4) was added to prepare solution B1;

[0116] In a reaction kettle, 2102 mL of a 5.00% mass fraction LATP suspension (ion conductive agent suspension, solvent: pure water), and 20 L of pure water were added, and the pH was adjusted to 6.0 with 2 mol / L ammonia water, nitrogen was introduced, the air in the reaction kettle was discharged, and the nitrogen was continuously introduced. Solution A1 and solution B1 were added to the reaction kettle, and 2 mol / L ammonia water was added while controlling the feeding rate of the ammonia water to maintain the system pH at 6.0. The reaction was carried out at 50°C and 450 rpm, and the stirring was stopped when the D50 particle size of the particles in the system was 2.0-2.5 μm. The system was aged at 50°C for 2 h to obtain a precursor containing an ion conductive agent;

[0117] S2. In 3.80 L of pure water, 0.760 mol of manganese sulfate (MnSO4), 6.802 mol of ferrous sulfate (FeSO4), and 0.038 mol of titanium sulfate (Ti(SO4)2, M2 source) were added to prepare solution A2, and in 3.80 L of pure water, 7.600 mol of ammonium dihydrogen phosphate (NH4H2PO4) was added to prepare solution B2;

[0118] The nitrogen was continuously introduced, solution A2 and solution B2 were added to the precursor containing the ion conductive agent obtained in step S1, and 2 mol / L ammonia water was added while controlling the feeding rate of the ammonia water to maintain the system pH at 6.0. The reaction was carried out at 50°C and 450 rpm, and the stirring was stopped when the D50 particle size of the particles in the system was 6.0-8.0 μm. The system was aged at 50°C for 4 h, filtered, washed with pure water for 4-6 times, filtered, and dried in a vacuum drying oven at 100°C overnight to obtain a lithium manganese iron phosphate precursor. The SEM and EDS images of the lithium manganese iron phosphate precursor are shown in Figure 2 ;

[0119] In step S1, the molar ratio of Mn element of the manganese source, Fe element of the iron source, and Mg element of the magnesium source was Mn:Fe:Mg=0.900:0.095:0.005, and the ratio of the total amount of substance of Mn element of the manganese source, Fe element of the iron source, and Mg element of the magnesium source to the amount of substance of P element of the phosphorus source was (Mn+Fe+Mg):P=1:1.

[0120] In step S2, the molar ratio of Mn element of the manganese source, Fe element of the iron source, and Ti element of the Ti source is Mn:Fe:Ti=0.100:0.895:0.005; and the ratio of the total amount of substance of the Mn element of the manganese source, the Fe element of the iron source, and the Ti element of the Ti source to the amount of substance of the P element of the phosphorus source is (Mn+Fe+Ti):P=1:1.

[0121] Examples 2-3 and Comparative Examples 1-2

[0122] Examples 2-3 and Comparative Examples 1-2 provide different lithium manganese iron phosphate precursors, which differ from Example 1 in that the mass fraction of the ion conductive agent LATP suspension, the amount of LATP, and the mass percentage of the inner core, the inner core layer, and the shell layer in the lithium manganese iron phosphate precursor are different, and the rest are consistent with Example 1, as shown in the following table:

[0123] Table 1 Amount of ion conductive agent LATP in Examples 1-3 and Comparative Examples 1-2

[0124] Examples 4-5

[0125] Examples 4-5 provide different lithium manganese iron phosphate precursors, which differ from Example 1 in that the type of ion conductive agent is different, and the rest are consistent with Example 1, as shown in the following table:

[0126] Table 2 Type of ion conductive agent in Examples 1, 4-5

[0127]

[0128] Examples 6-7 and Comparative Examples 3-4

[0129] Examples 6-7 and Comparative Examples 3-4 provide different lithium manganese iron phosphate precursors, which differ from Example 1 in that the molar ratio of Mn element, Fe element, and Mg element (Mn:Fe:Mg) in the inner core layer and the amount of each related raw material in step S1 are different, and the rest are consistent with Example 1, as shown in the following table:

[0130] Table 3 Experimental parameters of Examples 1, 6-7, and Comparative Examples 3-4

[0131]

[0132] Examples 8-9

[0133] Examples 8-9 provide different lithium manganese iron phosphate precursors, which differ from Example 1 in that the type of M1 source in step S1 and the amount of each related raw material in step S1 are different, and the rest are consistent with Example 1, as shown in the following table:

[0134] Table 4 Experimental parameters of Examples 1, 8-9

[0135]

[0136]

[0137] Examples 10-11 and Comparative Examples 5-6

[0138] Examples 10-11 and Comparative Examples 5-6 provide different lithium manganese iron phosphate precursors, which are different from Example 1 in that the molar ratio of Mn element, Fe element, Ti element in the shell layer (Mn:Fe:Ti) and the amount of each relevant raw material in step S2 are different, and the rest are consistent with Example 1, as shown in the following table:

[0139] Table 5 Experimental parameters of Examples 1, 10-11 and Comparative Examples 5-6

[0140]

[0141] Examples 12-13

[0142] Examples 12-13 provide different lithium manganese iron phosphate precursors, which are different from Example 1 in that the type of M2 source in step S2 and the amount of each relevant raw material in step S2 are different, and the rest are consistent with Example 1, as shown in the following table:

[0143] Table 6 Experimental parameters of Examples 1, 12-13

[0144]

[0145] Application Examples and Comparative Application Examples

[0146] Application Example 1

[0147] This application example provides a lithium manganese iron phosphate material, the SEM image of which is shown in Figure 3 The preparation method comprises the following steps:

[0148] The lithium manganese iron phosphate precursor (1500g) of Example 1, lithium source lithium carbonate (Li2CO3), carbon source and phosphorus source ammonium dihydrogen phosphate are uniformly mixed, put into a quartz crucible and placed in a box furnace, heated to 620℃ at a speed of 10℃ / min under nitrogen protection, sintered for 10h, and cooled to room temperature to obtain the lithium manganese iron phosphate material;

[0149] The ratio of the total amount of substance of metal elements in the lithium manganese iron phosphate precursor, the amount of substance of Li element in the lithium source (lithium carbonate), and the total amount of substance of P element in the mixture is metal element: Li: P = 1: 1.05: 1.05, wherein the total amount of substance of metal elements in the lithium manganese iron phosphate precursor refers to the total amount of substance of Mn element, Fe element, M1 element, and M2 element in the lithium manganese iron phosphate precursor, and the total amount of substance of P element in the mixture refers to the total amount of substance of P element in the lithium manganese iron phosphate precursor, P element in the lithium source, and P element in the phosphorus source (ammonium dihydrogen phosphate).

[0150] The mass of the carbon source accounts for 5% of the total mass of the lithium manganese iron phosphate precursor, the lithium source, the phosphorus source, and the carbon source, and the carbon source is glucose and carbon nanotubes (CNT) with a mass ratio of 10:1.

[0151] Application Example 2-13

[0152] Application Example 2-13 provides different lithium manganese iron phosphate materials, which are different from Application Example 1 in that Application Example 2-13 respectively uses the lithium manganese iron phosphate precursor of Example 2-13 instead of the lithium manganese iron phosphate precursor of Example 1, and the rest is consistent with Application Example 1.

[0153] Application Examples 14-16

[0154] Application Examples 14-16 provide different lithium manganese iron phosphate materials, which are different from Application Example 1 in that the types of carbon sources in Application Examples 14-16 are different, and the rest is consistent with Application Example 1, as shown in the following table:

[0155] Table 7 Types of carbon sources in Application Examples 1, 14-16

[0156] Kind of carbon source Application Example 1 Glucose and carbon nanotubes at a mass ratio of 10:1 Application Example 14 Glucose and PEG at a mass ratio of 10:1 Application Example 15 All glucose Application Example 16 All sucrose

[0157] Comparative Application Examples 1-6

[0158] Comparative Application Examples 1-6 provide different lithium manganese iron phosphate materials, which are different from Application Example 1 in that Comparative Application Examples 1-6 respectively use the lithium manganese iron phosphate precursor of Comparative Examples 1-6 instead of the lithium manganese iron phosphate precursor of Example 1, and the rest is consistent with Application Example 1.

[0159] Performance Test

[0160] The performance of the lithium manganese iron phosphate materials of each application example and comparative application example is tested, as follows:

[0161] (1) Preparation of a button-type lithium ion battery

[0162] A1. Put the lithium iron manganese phosphate material of each application example or comparative application example and the conductive agent (carbon black) into an oven, and after baking at 120°C for 4 h, transfer to cool in a dry vessel; then, take the corresponding proportions of lithium iron manganese phosphate material, binder (polyvinylidene fluoride, PVDF), and conductive agent (carbon black) in a mass ratio of 80:10:10, and add them to a 50 mL beaker, then add N-methyl pyrrolidone solution, and mix into a paste with a stirrer to obtain an electrode material;

[0163] A2. Uniformly coat the electrode material on an aluminum foil (current collector) to obtain a positive electrode sheet (electrode) with a single-sided area density of 60 g / m 2 , and then place it in a forced air drying oven at 120°C for 2 h, press it, and cut it into a circular positive electrode sheet with a diameter of 12 mm;

[0164] A3. In an argon atmosphere glove box, use the circular positive electrode sheet as the positive electrode, lithium sheet as the negative electrode, aluminum foil as the current collector, 1 mol / L LiPF6 ethylene carbonate solution, dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 as the electrolyte, and polypropylene microporous membrane Celgard 2300 as the separator, set the separator between the positive electrode and the negative electrode, and use the positive electrode, separator, and negative electrode as an electrode group, seal the electrode group and electrolyte with a battery shell, and obtain a lithium ion battery (CR2032 type button lithium ion battery).

[0165] (2) Test of each performance parameter

[0166] Place the assembled button lithium ion battery on a battery test system (a battery test system of the Blue Power series) at 25°C±2°C for charge-discharge cycle testing; the test conditions are as follows: the charge-discharge rate is 0.1C, 1C, and 8C, the voltage range is 2.5V-4.3V, one cycle is defined as one charge and one discharge, and record the conductivity, charge specific capacity, discharge specific capacity, first charge-discharge efficiency (i.e., first cycle coulombic efficiency), and capacity retention rate after 200 cycles; wherein:

[0167] Discharge specific capacity (mAh / g) = discharge capacity (unit: mAh) / mass of lithium iron manganese phosphate material (unit: g);

[0168] Charge specific capacity (mAh / g) = charge capacity (unit: mAh) / mass of lithium iron manganese phosphate material (unit: g);

[0169] First charge-discharge efficiency (%) = first discharge specific capacity / first charge specific capacity;

[0170] Capacity retention rate (%) after 200 cycles = discharge specific capacity of the 200th cycle / discharge specific capacity of the 1st cycle;

[0171] The experimental results are shown as follows:

[0172] Table 8 Performance test results of the lithium manganese iron phosphate materials of each application example and the comparative application

[0173]

[0174]

[0175] Figure 4 The charge-discharge curve of the lithium manganese iron phosphate material of application example 1 is shown in FIG. 1.

[0176] From Table 8 and Figure 4 It can be seen that the lithium manganese iron phosphate precursor has a specific structure including a core core, a core layer and a shell layer, which can effectively inhibit Mn dissolution and promote lithium ion diffusion, and provide a stable environment for lithium ion diffusion, thereby improving the conductivity and structural stability of the lithium manganese iron phosphate material prepared from the lithium manganese iron phosphate precursor.

[0177] Specifically, by comparing examples 1-3 and comparative examples 1-2, it can be seen that when the mass percentage of the core core in the lithium manganese iron phosphate precursor is too large, the active material of the lithium manganese iron phosphate material prepared from the lithium manganese iron phosphate precursor will decrease in quantity, affecting the energy density of the lithium ion battery, and hindering the diffusion of lithium ions, which is not conducive to improving the conductivity of the lithium manganese iron phosphate material prepared from the lithium manganese iron phosphate precursor. When the mass percentage of the core core in the lithium manganese iron phosphate precursor is too small, the specific structure of the lithium manganese iron phosphate precursor cannot well promote the diffusion of lithium ions, and is also not conducive to improving the conductivity of the lithium manganese iron phosphate material prepared from the lithium manganese iron phosphate precursor.

[0178] As can be seen by comparing the examples 1, 6-11 and the comparative examples 3-6, in the present application, the inner core layer and the shell layer of the lithium manganese iron phosphate precursor are respectively adjusted by adding appropriate amounts of the doping metal elements M1 and M2, so as to respectively control the internal crystal structure of the inner core layer and the shell layer, which helps to improve the stability of the specific structure of the lithium manganese iron phosphate precursor, thereby protecting and promoting the diffusion of lithium ions, and further helps to improve the conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor. When the amounts of the doping metal elements M1 and M2 added in the inner core layer and the shell layer are too much, the doping metal elements M1 and M2 will destroy the internal crystal structure of the inner core layer and the shell layer, which is not conducive to maintaining the stability of the specific structure of the lithium manganese iron phosphate precursor, thereby not conducive to improving the conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor; at the same time, the doping metal elements M1 and M2 will gather at the grain boundaries, which may adversely affect the performance of the lithium manganese iron phosphate material. When the amounts of the doping metal elements M1 and M2 added in the inner core layer and the shell layer are too little, the doping metal elements M1 and M2 cannot well control the internal crystal structure of the inner core layer and the shell layer, which is not conducive to constructing a stable specific structure of the lithium manganese iron phosphate precursor, and cannot promote the diffusion of lithium ions, which is not conducive to improving the conductivity of the lithium manganese iron phosphate material prepared by using the lithium manganese iron phosphate precursor.

[0179] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for preparing lithium manganese iron phosphate material, characterized in that: The preparation method comprises the following steps: A lithium iron manganese phosphate precursor, a lithium source, a carbon source and a phosphorus source are mixed and sintered to obtain a lithium iron manganese phosphate material; The carbon source is glucose and carbon nanotubes in a mass ratio of (0.1-10):1; The lithium manganese iron phosphate precursor is composed of an inner core, an inner core layer and an outer shell layer from the inside to the outside; The core is an ion conductive agent, and the mass of the core accounts for 0.50-8.00% of the mass of the lithium manganese iron phosphate precursor; The inner core layer contains Mn, Fe, M1, and P, wherein M1 is a doping metal element; the molar ratio of Mn, Fe, and M1 is Mn:Fe:M1=x:(1-xy):y, 0.5≤x<1, 0<y≤0.05; the molar ratio of the sum of the amounts of Mn, Fe, and M1 to the amount of P is (Mn+Fe+M1):P=1:(0.6-1.05); the mass of the inner core layer accounts for 52.00-69.00% of the mass of the lithium manganese iron phosphate precursor; The outer shell layer contains Mn element, Fe element, M2 element, and P element, wherein the M2 element is a doping metal element; the molar ratio of the Mn element, Fe element, and M2 element is Mn:Fe:M2=a:(1-ab):b, 0<a<0.5, 0<b≤0.05; the ratio of the sum of the amount of the Mn element, Fe element, and M2 element to the amount of the P element is (Mn+Fe+M2):P=1:(0.6-1.05); the mass of the outer shell layer accounts for 23.00-47.50% of the mass of the lithium manganese iron phosphate precursor.

2. The method for preparing the lithium manganese iron phosphate material according to claim 1, wherein: Include at least one of the following (1)-(8): (1) The mass of the inner core layer accounts for 57.00-62.00% of the mass of the lithium manganese iron phosphate precursor; (2) The mass of the outer shell layer accounts for 34.00-38.00% of the mass of the lithium manganese iron phosphate precursor; (3) The inner core layer further contains an O element; and in the inner core layer, the molar ratio of the P element to the O element is P:O=1:4; (4) The outer shell layer further contains an O element; and in the outer shell layer, the molar ratio of the P element to the O element is P:O=1:4; (5) In the inner core layer, the molar ratio of the Mn element, the Fe element, and the M1 element is Mn:Fe:M1=(0.500-0.948):(0.050-0.498):(0.002-0.050); (6) In the outer shell layer, the molar ratio of the Mn element, Fe element, and M2 element is Mn:Fe:M2=(0.100-0.400):(0.550-0.898):(0.002-0.050); (7) The M1 element and the M2 element are independently selected from at least one of Ti, Mg, Al, Ni, Nb, Co, Cu, and Si; (8) The ion conductive agent is at least one of LATP, LAGP and LLTO.

3. The method for preparing the lithium manganese iron phosphate material according to claim 2, wherein: Include at least one of the following (1)-(7): (1) The mass of the inner core layer accounts for 57.26-61.93% of the mass of the lithium manganese iron phosphate precursor; (2) The mass of the outer shell layer accounts for 34.50-37.80% of the mass of the lithium iron manganese phosphate precursor, and specifically may be 34.74-37.57%; (3) In the inner core layer, the molar ratio of the Mn element, the Fe element, and the M1 element is Mn:Fe:M1=0.900:(0.050-0.098):(0.002-0.050); (4) In the outer shell layer, the molar ratio of the Mn element, the Fe element, and the M2 element is Mn:Fe:M2=0.100:(0.850-0.898):(0.002-0.050); (5) The chemical composition formula of the LATP is Li 1+c Al c Ti 2-c (PO4)3,0<c≤0.5; (6) The chemical composition formula of the LAGP is Li 1+d Al d Ge 2-d (PO4)3,0<d≤0.5; (7) The general chemical formula of the LLTO is Li 3e La 2 / 3-e Ti f T 1-f O3, where 0 < e < 2 / 3 and 0 < f ≤ 1. Herein, T is independently selected from at least one of Nb, W, Hf, Ru, Mo, Nd, Ba, Ga, In, Ge, Sn, Sb, and Se.

4. The method for preparing the lithium manganese iron phosphate material according to claim 1, characterized in that: The preparation method of the lithium manganese iron phosphate precursor comprises the following steps: S1. Mixing the ion conductive agent and the manganese source, iron source, M1 source, and phosphorus source required for the inner core layer, reacting at pH = 2-12, and aging to obtain a precursor containing an ion conductive agent; S2. Mix the precursor containing the ion conductive agent obtained in step S1 with the manganese source, iron source, M2 source, and phosphorus source required for the outer shell layer, react under the condition of pH = 2-12, and age to obtain a lithium manganese iron phosphate precursor.

5. The method for preparing the lithium manganese iron phosphate material according to claim 4, wherein: Include at least one of the following (1)-(4): (1) In step S1 and / or S2, the pH range is 4-7; (2) In step S1 and / or S2, the reaction temperature is 20-80°C; (3) In step S1, the molar ratio of the Mn element of the manganese source, the Fe element of the iron source, and the M1 element of the M1 source is Mn:Fe:M1=x:(1-xy):y, 0.5≤x<1, 0<y≤0.05; the molar ratio of the sum of the amount of the Mn element of the manganese source, the Fe element of the iron source, and the M1 element of the M1 source to the amount of the P element of the phosphorus source is (Mn+Fe+M1):P=1:(0.6-1.05); (4) In step S2, the molar ratio of the Mn element of the manganese source, the Fe element of the iron source, and the M2 element of the M2 source is Mn:Fe:M2=a:(1-ab):b, 0<a<0.5, 0<b≤0.05; the ratio of the sum of the amount of the Mn element of the manganese source, the Fe element of the iron source, and the M2 element of the M2 source to the amount of the P element of the phosphorus source is (Mn+Fe+M2):P=1:(0.6-1.05).

6. The method for preparing the lithium manganese iron phosphate material according to claim 4, wherein: Include at least one of the following (1)-(5): (1) In step S1 and / or S2, the manganese source is at least one of manganese sulfate, manganese oxalate, manganese phosphate, and manganese nitrate; (2) In step S1 and / or S2, the iron source is at least one of ferrous sulfate, ferrous oxalate, ferrous nitrate, and ferrous chloride; (3) In step S1, the M1 source is at least one of oxalates, chlorides, nitrates, sulfates, phosphates, and hydroxides of each of Ti, Mg, Al, Ni, Nb, Co, Cu, and Si; (4) In step S2, the M2 source is at least one of oxalates, chlorides, nitrates, sulfates, phosphates, and hydroxides of each of Ti, Mg, Al, Ni, Nb, Co, Cu, and Si; (5) In step S1 and / or S2, the phosphorus source is at least one of phosphoric acid, lithium dihydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

7. The method for preparing the lithium manganese iron phosphate material according to claim 1, wherein: Include at least one of the following (1)-(5): (1) The ratio of the total amount of metal elements in the lithium iron manganese phosphate precursor, the amount of Li element in the lithium source, and the total amount of P element in the mixture is metal element: Li: P = 1: (1.00-1.10): (1.00-1.10), wherein the total amount of metal elements in the lithium iron manganese phosphate precursor refers to the total amount of Mn element, Fe element, M1 element, and M2 element in the lithium iron manganese phosphate precursor, and the total amount of P element in the mixture refers to the total amount of P element in the lithium iron manganese phosphate precursor, P element in the lithium source, and P element in the phosphorus source; (2) The mass of the carbon source accounts for 1.5-6.0% of the total mass of the lithium manganese iron phosphate precursor, the lithium source, the phosphorus source and the carbon source; (3) The sintering temperature is 500-900°C and the sintering time is 6-20h; (4) The lithium source is at least one of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate; (5) The phosphorus source is at least one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

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

9. An electrode material, characterized in that The electrode material contains the lithium manganese iron phosphate material as claimed in claim 8, a conductive agent and a binder.

10. A method for preparing an electrode material, characterized in that: The steps include: The lithium manganese iron phosphate material as claimed in claim 8, a conductive agent and a binder are mixed to obtain an electrode material.

11. An electrode, characterized in that: It comprises a current collector, the surface of which is provided with the electrode material as claimed in claim 9.

12. A method for preparing an electrode, characterized in that: The steps include: The electrode material as claimed in claim 9 is coated on the current collector to obtain the electrode.

13. A lithium ion battery, characterized in that: It includes an electrode group and an electrolyte, which are sealed in a battery shell; the electrode group includes a positive electrode, a separator and a negative electrode, and the separator is arranged between the positive electrode and the negative electrode; the positive electrode is the electrode as claimed in claim 11.

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