An in-situ preparation method of a lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material

Abstract

The application belongs to the technical field of electrode materials, and discloses an in-situ preparation method of a lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material, which utilizes melamine, formaldehyde, ammonium polyphosphate and a mixture to prepare in-situ polymerization double-layer coated modified ammonium polyphosphate; after lithium hydroxide monohydrate is dissolved, glacial acetic acid and an aqueous solution of the in-situ polymerization double-layer coated modified ammonium polyphosphate are added and uniformly mixed to obtain a lithium acetate and ammonium polyphosphate mixed suspension; nano lithium-rich manganese-based compound powder and an organic carbon source are sequentially added to the mixed suspension of lithium acetate and ammonium polyphosphate to obtain organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder, and the powder is calcined; after inorganic carbon source and the obtained calcined product are uniformly mixed, a binder is added, and drying and pressing are performed to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material. The preparation method is simple, low in cost, high in efficiency, and the prepared lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material has good water resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and particularly relates to an in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material. BACKGROUND

[0002] At present, one component in an electronic or electrical device is used as two ends of input or output current in a conductive medium (solid, gas, vacuum or electrolyte solution). The pole of input current is called anode or positive pole, and the pole of output current is called cathode or negative pole. Electrodes have various types, such as cathode, anode, welding electrode, furnace electrode and the like. In a battery, an electrode generally refers to a position where an oxidation-reduction reaction occurs with an electrolyte solution. Electrodes have positive and negative poles, and generally, the positive pole is the cathode, obtains electrons and occurs reduction reaction, and the negative pole is the anode, loses electrons and occurs oxidation reaction. Electrodes can be metal or non-metal, as long as they can exchange electrons with an electrolyte solution to become electrodes. However, the raw material ammonium polyphosphate used in the existing in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material has poor water resistance, resulting in poor water resistance of the prepared lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material and affecting the preparation efficiency. Therefore, it is urgent to design a new in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material.

[0003] Through the above analysis, the problems and defects of the prior art are that the raw material ammonium polyphosphate used in the existing in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material has poor water resistance, resulting in poor water resistance of the prepared lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material and affecting the preparation efficiency. SUMMARY

[0004] In view of the problems existing in the prior art, the application provides an in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material.

[0005] The application is implemented as follows: an in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material, which comprises the following steps:

[0006] Step one: preparation of in-situ polymerization double-layer coated modified ammonium polyphosphate: a prepolymer is prepared from melamine and formaldehyde solution; ammonium polyphosphate and water are mixed, and then the prepolymer, an initiator, an organic solvent and a mixture are added for reaction, drying, crushing, to obtain in-situ polymerization double-layer coated modified ammonium polyphosphate;

[0007] Step two: preparation of acetic acid lithium and ammonium polyphosphate mixed suspension: after single water lithium hydroxide is mixed with pure water, stirred and dissolved to be clear, glacial acetic acid is added, the pH value of the reaction system is adjusted to 7, and the in-situ polymerization double-layer coated modified ammonium polyphosphate aqueous solution is uniformly mixed, to obtain acetic acid lithium and ammonium polyphosphate mixed suspension;

[0008] Step three, preparation of the organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor: the nano lithium-rich manganese-based compound powder is added into the mixed suspension of lithium acetate and ammonium polyphosphate and titrated, and after standing, the filtrate is washed and dried, and then added into the solution of the organic carbon source, stirred, filtered, washed, and dried to obtain the organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder;

[0009] Step four, preparation of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material: the organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder is calcined, and the inorganic carbon source is mixed with the obtained calcined product, a binder is added, and stirring is performed to obtain a uniform mixture; the obtained carbon coated lithium iron phosphate-lithium-rich manganese-based dual-phase positive electrode slurry is coated on an aluminum foil substrate and dried and pressed to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material.

[0010] Further, the preparation method of the in-situ polymerization double-layer coated modified ammonium polyphosphate in step one comprises:

[0011] (1) urea is subjected to boiling reaction to generate cyanic acid, and the generated trimerized amine gas is condensed, dissolved, impurities are removed, and melamine is obtained by recrystallization, with ammonia gas as a carrier and silica gel as a catalyst;

[0012] (2) the melamine obtained in step (1) is mixed with formaldehyde solution and water in a certain proportion, and then placed in a mixer, and the pH, temperature, and time of the reaction are controlled to generate a prepolymer;

[0013] (3) ammonium polyphosphate and water are mixed in a certain proportion, the pH and temperature of the reaction are controlled, the prepolymer is added and reacted for a certain period of time, dried, and crushed to obtain melamine formaldehyde resin modified ammonium polyphosphate;

[0014] (4) an initiator and an organic solvent are added to the melamine formaldehyde resin modified ammonium polyphosphate, stirred, and then a mixture of acrylic acid and acrylic ester is added, the temperature is controlled, and the reaction is carried out, dried, and crushed to obtain the in-situ polymerization double-layer coated modified ammonium polyphosphate powder.

[0015] Further, the boiling reaction in step (1) is carried out at 380-400℃ for 15-20 min;

[0016] the pH of the reaction in step (2) is 8, the temperature of the reaction is 80-85℃, and the time of the reaction is 40-60 min; the concentration of the melamine is 20-25wt%, and the concentration of the formaldehyde is 12-15wt%;

[0017] The ammonium polyphosphate and water in the step (3) are mixed in a ratio of 70-90:100, the prepolymer and ammonium polyphosphate are added in a ratio of 1:6, and drying is performed at 120-150℃ until a constant weight is obtained;

[0018] The initiator in the step (4) is at least one of organic peroxide or persulfate; and the organic solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol, benzene or toluene.

[0019] Further, the preparation method of the mixed suspension of lithium acetate and ammonium polyphosphate in the step two comprises:

[0020] (1) The lithium hydroxide monohydrate and pure water are stirred and dissolved in a certain weight ratio to be clear by a stirrer, glacial acetic acid is added in a certain molar ratio with lithium element, and stirring is performed to mix uniformly, so as to obtain a reaction system;

[0021] (2) The pH value of the reaction system is adjusted to 7 by using lithium hydroxide or glacial acetic acid; after detecting that the pH value has no change, insoluble impurities are removed by filtration, so as to obtain an aqueous solution of lithium acetate;

[0022] (3) The aqueous solution of lithium acetate and the aqueous solution of in-situ polymerization double-layer coated modified ammonium polyphosphate prepared in step one are mixed and stirred uniformly, so as to obtain a mixed suspension of lithium acetate and ammonium polyphosphate.

[0023] Further, the lithium hydroxide monohydrate and pure water are stirred and dissolved in a weight ratio of 1:2 in the step (1); and the molar ratio of the glacial acetic acid to lithium element is 1:1.

[0024] The concentration of the mixed suspension of lithium acetate and ammonium polyphosphate in the step (3) is 0.05-6.5 mol / L.

[0025] Further, the preparation method of the lithium iron phosphate-rich lithium manganese-based dual-phase precursor coated with the organic carbon source in the step three comprises:

[0026] (1) The nano lithium-rich manganese-based compound powder is added into the mixed suspension of lithium acetate and ammonium polyphosphate, and titration is performed by using an aqueous solution of ferrous chloride under the condition of continuous stirring, so as to make lithium iron phosphate nucleate and grow on the nano lithium-rich manganese-based powder, and obtain a lithium iron phosphate-rich lithium manganese-based dual-phase precursor slurry;

[0027] (2) The obtained lithium iron phosphate-rich lithium manganese-based dual-phase precursor slurry is left to stand and then filtered, the obtained filter residue is washed by using deionized water and then dried, so as to obtain a lithium iron phosphate-rich lithium manganese-based dual-phase precursor powder;

[0028] (3) the lithium phosphate- lithium-rich manganese-based dual-phase precursor powder obtained is added into a solution of an organic carbon source, stirred until uniform, filtered, the filter residue is washed with deionized water and dried to obtain the lithium phosphate- lithium-rich manganese-based dual-phase precursor powder coated with the organic carbon source.

[0029] Further, the mass ratio of the total mass of lithium acetate and ammonium polyphosphate in the mixed suspension of lithium acetate and ammonium polyphosphate in step (1) to the mass of the nano lithium-rich manganese-based powder is 0.3-2.5:1;

[0030] The standing time in step (2) is more than 2h, and the mass of the organic carbon source in step (3) is 81% of the mass of the lithium phosphate- lithium-rich manganese-based dual-phase precursor powder.

[0031] Further, the preparation method of the lithium phosphate- lithium-rich manganese-based dual-phase electrode material in step four comprises:

[0032] (1) the lithium phosphate- lithium-rich manganese-based dual-phase precursor powder coated with the organic carbon source obtained is calcined under nitrogen atmosphere to obtain the lithium phosphate- lithium-rich manganese-based dual-phase electrode material coated with the organic carbon source;

[0033] (2) the inorganic carbon source is mixed with the lithium phosphate- lithium-rich manganese-based dual-phase electrode material coated with the organic carbon source obtained, a binder is added and stirred until uniform to obtain the lithium phosphate- lithium-rich manganese-based dual-phase positive electrode slurry coated with carbon;

[0034] (3) the lithium phosphate- lithium-rich manganese-based dual-phase positive electrode slurry coated with carbon obtained is coated on an aluminum foil substrate, and is sequentially subjected to drying and pressing to obtain the lithium phosphate- lithium-rich manganese-based dual-phase electrode material.

[0035] Further, the calcination process in step (1) is as follows: the temperature is raised to 900℃ at a temperature raising rate of 30℃ / min, the temperature is kept constant for 12-24h, and then the temperature is cooled to room temperature at a temperature lowering rate of 35℃ / min.

[0036] Further, the inorganic carbon source in step (2) is any one or a combination of more than one of graphite, carbon black, carbon microspheres, carbon nanomicrospheres, carbon nanotubes, carbon nanofibers or carbon gel.

[0037] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions of the present application to be protected are analyzed from the following aspects:

[0038] First, in view of the technical problems existing in the prior art and the difficulty in solving the problems, the technical solutions of the present application to be protected are closely combined with the results and data in the research and development process, and the technical problems solved by the technical solutions are analyzed in detail and profoundly, and some creative technical effects brought about after the problems are solved. The specific description is as follows:

[0039] The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the application comprises the following steps: adding a nano lithium-rich manganese compound powder and an organic carbon source into a mixed suspension liquid of lithium acetate and ammonium polyphosphate to prepare a lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder coated with the organic carbon source on the surface, and the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material prepared by the method has good water resistance.

[0040] Secondly, the technical effect and advantages of the technical solution to be protected by the application are described as follows from the perspective of the product as a whole or from the perspective of the product:

[0041] The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the application is simple, easy to implement, low in cost, high in efficiency, and the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material prepared by the method has good water resistance. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments of the application will be briefly introduced as follows. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0043] Figure 1 is a flow chart of the in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the embodiments of the application;

[0044] Figure 2 is a flow chart of the preparation method of the mixed suspension liquid of lithium acetate and ammonium polyphosphate provided by the embodiments of the application;

[0045] Figure 3 is a flow chart of the preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the embodiments of the application. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0047] In view of the problems in the prior art, the present application provides an in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material, which is described in detail below with reference to the accompanying drawings.

[0048] I. Explanation of examples. In order for those skilled in the art to fully understand how the present application is specifically implemented, this part is an explanation of the examples of the technical scheme of the claims.

[0049] As shown in Figure 1 The in-situ preparation method of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the embodiments of the present application includes the following steps:

[0050] S101, preparation of in-situ polymerization double-layer coated modified ammonium polyphosphate: a prepolymer is prepared from melamine and formaldehyde solution; ammonium polyphosphate and water are mixed and then the prepolymer is added, followed by addition of an initiator, an organic solvent and a mixture for reaction, drying, and crushing to obtain in-situ polymerization double-layer coated modified ammonium polyphosphate;

[0051] S102, preparation of a mixed suspension of lithium acetate and ammonium polyphosphate: after single water lithium hydroxide is mixed with pure water and stirred to dissolve until clear, glacial acetic acid is added to adjust the pH value of the reaction system to 7, and the in-situ polymerization double-layer coated modified ammonium polyphosphate aqueous solution is mixed uniformly to obtain a mixed suspension of lithium acetate and ammonium polyphosphate;

[0052] S103, preparation of organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor: nano lithium-rich manganese-based compound powder is added to the mixed suspension of lithium acetate and ammonium polyphosphate and titrated, and then filtered after standing; the filter residue is washed and dried, and then added to a solution of organic carbon source, stirred uniformly, filtered, the filter residue is washed and dried to obtain organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder;

[0053] S104, preparation of lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material: the organic carbon source coated lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder is calcined, and inorganic carbon source is mixed with the obtained calcined product, a binder is added and stirred uniformly; the obtained carbon coated lithium iron phosphate-lithium-rich manganese-based dual-phase positive electrode slurry is coated on an aluminum foil substrate and dried and pressed to obtain lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material.

[0054] The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material is simple and easy to implement, low in cost, high in efficiency, and good in water resistance.

[0055] The preparation method of the in-situ polymerization double-layer coated modified ammonium polyphosphate in step S101 comprises the following steps:

[0056] (1) Boiling reaction of urea is carried out with ammonia as a carrier and silica gel as a catalyst, cyanic acid is generated by decomposition, and the generated trimer amine gas is captured by cooling, dissolved, impurities are removed, and trimer cyanamide is obtained by recrystallization;

[0057] (2) The trimer cyanamide prepared in step (1) is uniformly mixed with formaldehyde solution and water in a certain proportion, and then placed in a mixer, the reaction pH, reaction temperature and reaction time are controlled, and a prepolymer is generated;

[0058] (3) Ammonium polyphosphate and water are uniformly mixed in a certain proportion, the pH and reaction temperature are controlled, the prepolymer is added and reacted for a certain time, dried, and crushed to obtain trimer cyanamide formaldehyde resin modified ammonium polyphosphate;

[0059] (4) An initiator and an organic solvent are added to the trimer cyanamide formaldehyde resin modified ammonium polyphosphate, stirred, then a mixture of acrylic acid and acrylic ester is added, the temperature is controlled, and reaction is carried out, dried, and crushed to obtain in-situ polymerization double-layer coated modified ammonium polyphosphate powder.

[0060] The boiling reaction in step (1) is carried out at 380-400 DEG C for 15-20 min;

[0061] The reaction pH in step (2) is 8, the reaction temperature is 80-85 DEG C, and the reaction time is 40-60 min; the concentration of the trimer cyanamide is 20-25 wt%, and the concentration of the formaldehyde is 12-15 wt%;

[0062] The ammonium polyphosphate and water in step (3) are mixed in a ratio of 70-90:100, the prepolymer and ammonium polyphosphate are added in a ratio of 1:6, and dried to constant weight at 120-150 DEG C;

[0063] The initiator in step (4) is at least one of organic peroxide or persulfate; and the organic solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol, benzene or toluene.

[0064] The preparation method of the in-situ polymerization double-layer coated modified ammonium polyphosphate provided by the embodiment of the present application is prepared by using the in-situ polymerization method, taking ammonium polyphosphate as raw material, and performing double-layer coating modification on the surface of the ammonium polyphosphate, so that the modified ammonium polyphosphate not only has improved flame retardant effect, but also has improved water resistance and dispersibility in polymers, and the water resistance of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material is greatly improved.

[0065] As shown in Figure 2 The preparation method of the mixed suspension liquid of lithium acetate and ammonium polyphosphate in step S102 provided by the embodiment of the present application comprises:

[0066] S201, stirring and dissolving lithium hydroxide monohydrate and pure water in a certain weight ratio to be clear, adding glacial acetic acid in a certain molar ratio with lithium element, stirring and mixing uniformly to obtain a reaction system;

[0067] S202, adjusting the pH value of the reaction system to 7 by using lithium hydroxide or glacial acetic acid; after detecting that the pH value has no change, removing the insoluble impurities by filtration to obtain an aqueous solution of lithium acetate;

[0068] S203, mixing and stirring the aqueous solution of lithium acetate and the aqueous solution of the in-situ polymerization double-layer coated modified ammonium polyphosphate prepared in S101 uniformly to obtain a mixed suspension liquid of lithium acetate and ammonium polyphosphate.

[0069] In step S201 provided by the embodiment of the present application, the lithium hydroxide monohydrate and the pure water are stirred and dissolved in a weight ratio of 1:2, and the molar ratio of the glacial acetic acid to the lithium element is 1:1;

[0070] The concentration of the mixed suspension liquid of lithium acetate and ammonium polyphosphate in step S203 is 0.05-6.5 mol / L.

[0071] The preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase precursor coated with the organic carbon source in step S103 provided by the embodiment of the present application comprises:

[0072] (1) adding nano lithium-rich manganese-based compound powder into the mixed suspension liquid of lithium acetate and ammonium polyphosphate and titrating with an aqueous solution of ferrous chloride under the condition of continuous stirring, so that lithium iron phosphate nucleates and grows on the nano lithium-rich manganese-based powder to obtain a lithium iron phosphate-lithium-rich manganese-based dual-phase precursor slurry;

[0073] (2) filtering the obtained lithium iron phosphate-lithium-rich manganese-based dual-phase precursor slurry after standing, washing the obtained filter residue with deionized water, and drying to obtain lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder;

[0074] (3) the obtained lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder is added into a solution of organic carbon source, stirred uniformly, filtered, the filter residue is washed with deionized water and dried to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder coated with organic carbon source.

[0075] The lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder obtained by adding the nano lithium-rich manganese-based compound powder and the organic carbon source into the mixed suspension of lithium acetate and ammonium polyphosphate in sequence for reaction has the surface coated with the organic carbon source and is more stable in chemical property.

[0076] The total mass of lithium acetate and ammonium polyphosphate in the mixed suspension of lithium acetate and ammonium polyphosphate in step (1) is 0.3-2.5:1 of the mass of the nano lithium-rich manganese-based powder.

[0077] The standing time in step (2) is more than 2h, and the mass of the organic carbon source in step (3) is 81% of the mass of the lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder.

[0078] As shown in Figure 3 The preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material in step S104 includes:

[0079] S301, the obtained lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder coated with organic carbon source is calcined under the protection of nitrogen atmosphere to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material coated with organic carbon source;

[0080] S302, the inorganic carbon source is uniformly mixed with the obtained lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material coated with organic carbon source, a binder is added and stirred uniformly to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase positive electrode slurry coated with carbon;

[0081] S303, the obtained lithium iron phosphate-lithium-rich manganese-based dual-phase positive electrode slurry coated with carbon is coated on an aluminum foil substrate, and is sequentially subjected to drying and pressing to obtain the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material.

[0082] The calcination process in step S301 includes: increasing the temperature to 900℃ at a temperature increasing rate of 30℃ / min, constant temperature calcination for 12-24h, and cooling to room temperature at a temperature decreasing rate of 35℃ / min.

[0083] The inorganic carbon source in step S302 is any one or a combination of more than one of graphite, carbon black, carbon microspheres, carbon nanomicrospheres, carbon nanotubes, carbon nanofibers or carbon gel.

[0084] The lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material is prepared by calcining the lithium iron phosphate-lithium-rich manganese-based dual-phase precursor powder coated with an organic carbon source and then reacting with an inorganic carbon source, so that the efficiency of preparing the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material is improved.

[0085] II. Evidence of the effects of the embodiments. The embodiments have achieved some positive effects in the research and use process, and indeed have great advantages compared with the prior art. The following content is described in combination with the data and charts of the test process.

[0086] According to data checking, the conductivity of the untreated electrode material is generally in the order of 10 -8 The conductivity of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material prepared by the in-situ preparation method provided by the embodiments can reach 1.55 S / cm, and the conductivity of the electrode material can be improved by one order of magnitude. After the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material provided by the embodiments is assembled into a battery, the charge-discharge specific capacity of the battery provided by the embodiments is improved by 35% compared with the battery assembled by the ordinary electrode material after 500 cycles of charge-discharge at 1C rate.

[0087] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any modification, equivalent replacement and improvement made by any person skilled in the art within the technical range disclosed by the present application, as long as it is within the spirit and principles of the present application, should be covered within the protection scope of the present application.

Claims

1. A method for in-situ preparation of a lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material, characterized in that, The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material includes the following steps: Step 1: Preparation of in-situ polymerized bilayer-coated modified ammonium polyphosphate: A prepolymer is prepared using melamine and formaldehyde solution; ammonium polyphosphate and water are mixed and added to the prepolymer, then an initiator, organic solvent and mixture are added to react, dried and pulverized to obtain in-situ polymerized bilayer-coated modified ammonium polyphosphate. Step 2: Preparation of a mixed suspension of lithium acetate and ammonium polyphosphate: Lithium hydroxide monohydrate is mixed with pure water and stirred until clear. Glacial acetic acid is then added to adjust the pH of the reaction system to 7. The mixture is then mixed with an aqueous solution of in-situ polymerized bilayer-coated modified ammonium polyphosphate to obtain a mixed suspension of lithium acetate and ammonium polyphosphate. Step 3: Preparation of organic carbon source-coated lithium iron phosphate-lithium-rich manganese-based biphase precursor: Add nano-lithium-rich manganese-based compound powder to a mixed suspension of lithium acetate and ammonium polyphosphate and titrate. After standing, filter, wash and dry the filter residue, add it to the organic carbon source solution, stir and filter, wash and dry the filter residue to obtain organic carbon source-coated lithium iron phosphate-lithium-rich manganese-based biphase precursor powder. Step 4: Preparation of lithium iron phosphate-lithium-rich manganese-based biphase electrode material: The lithium iron phosphate-lithium-rich manganese-based biphase precursor powder coated with organic carbon source is calcined. The inorganic carbon source is mixed with the obtained calcined product, and a binder is added and stirred evenly. The obtained carbon-coated lithium iron phosphate-lithium-rich manganese-based biphase cathode slurry is coated on an aluminum foil substrate, dried and pressed to obtain the lithium iron phosphate-lithium-rich manganese-based biphase electrode material. The preparation method of in-situ polymerized bilayer coated modified ammonium polyphosphate in step one includes: (1) Using ammonia as a carrier and silica gel as a catalyst, urea is boiled to decompose and generate cyanic acid. The melamine gas generated by condensation is cooled, collected, dissolved, impurities removed, and recrystallized to obtain melamine. (2) The melamine prepared in step (1) is mixed with formaldehyde solution and water in a certain proportion and then placed in a mixer. The reaction pH, reaction temperature and reaction time are controlled to generate a prepolymer. (3) Mix ammonium polyphosphate and water in a certain proportion, control the pH and reaction temperature, add the prepolymer and react for a certain time, dry and crush to obtain melamine formaldehyde resin modified ammonium polyphosphate. (4) Add an initiator and an organic solvent to the melamine-formaldehyde resin modified ammonium polyphosphate, stir well, then add a mixture of acrylic acid and acrylate substances, control the temperature, carry out the reaction, dry, and pulverize to obtain in-situ polymerized double-layer coated modified ammonium polyphosphate powder. The boiling reaction in step (1) is carried out at 380-400℃ for 15-20 minutes. The reaction pH in step (2) is 8, the reaction temperature is 80-85℃, and the reaction time is 40-60 min; the concentration of melamine is 20-25 wt%, and the concentration of formaldehyde is 12-15 wt%. In step (3), ammonium polyphosphate and water are mixed in a ratio of 70-90:100, the prepolymer and ammonium polyphosphate are added in a ratio of 1:6, and dried at 120-150°C to constant weight. The initiator in step (4) is at least one of organic peroxide or persulfate; the organic solvent is at least one of methanol, ethanol, propanol, isopropanol, butanol, benzene or toluene.

2. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 1, characterized in that, The method for preparing the mixed suspension of lithium acetate and ammonium polyphosphate in step two includes: (1) Lithium hydroxide monohydrate and pure water were stirred and dissolved in a certain weight ratio using a stirrer until clear. Glacial acetic acid with a certain molar ratio of lithium was added and stirred until uniform to obtain the reaction system. (2) Adjust the pH of the reaction system to 7 using lithium hydroxide or glacial acetic acid; after confirming that the pH has not changed, filter to remove insoluble impurities and obtain an aqueous solution of lithium acetate. (3) Mix the aqueous solution of lithium acetate and the aqueous solution of in-situ polymerized bilayer coated modified ammonium polyphosphate prepared in step one until they are homogeneous to obtain a mixed suspension of lithium acetate and ammonium polyphosphate.

3. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 1, characterized in that, In step (1), lithium hydroxide monohydrate is dissolved in pure water at a weight ratio of 1:2, and the molar ratio of glacial acetic acid to lithium is 1:

1. The concentration of the mixed suspension of lithium acetate and ammonium polyphosphate in step (3) is 0.05–6.5 mol / L.

4. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 1, characterized in that, The preparation method of the organic carbon source-coated lithium iron phosphate-lithium-rich manganese-based biphase precursor in step three includes: (1) Add the nano-lithium-rich manganese-based compound powder to a mixed suspension of lithium acetate and ammonium polyphosphate and titrate with an aqueous solution of ferrous chloride while continuing to stir, so that lithium iron phosphate nucleates and grows on the nano-lithium-rich manganese-based powder to obtain lithium iron phosphate-lithium-rich manganese-based biphase precursor slurry. (2) After the obtained lithium iron phosphate-lithium-rich manganese-based biphase precursor slurry was allowed to stand, it was filtered. The filter residue was washed with deionized water and dried to obtain lithium iron phosphate-lithium-rich manganese-based biphase precursor powder. (3) The obtained lithium iron phosphate-lithium-rich manganese-based biphase precursor powder was added to the solution of organic carbon source, stirred evenly, filtered, and the filter residue was washed with deionized water and dried to obtain organic carbon source coated lithium iron phosphate-lithium-rich manganese-based biphase precursor powder.

5. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 4, characterized in that, In step (1), the total mass ratio of lithium acetate and ammonium polyphosphate in the mixed suspension to the mass ratio of the nano-lithium-rich manganese-based powder is 0.3–2.5:

1. The settling time in step (2) is more than 2 hours, and the mass of the organic carbon source in step (3) is 81% of the mass of the lithium iron phosphate-lithium-rich manganese-based biphase precursor powder.

6. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 1, characterized in that, The preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material in step four includes: (1) The obtained organic carbon source coated lithium iron phosphate-lithium-rich manganese-based biphase precursor powder was calcined under nitrogen atmosphere protection to obtain organic carbon source coated lithium iron phosphate-lithium-rich manganese-based biphase electrode material. (2) After mixing the inorganic carbon source with the obtained organic carbon source-coated lithium iron phosphate-lithium-rich manganese-based biphase electrode material, a binder is added and stirred evenly to obtain carbon-coated lithium iron phosphate-lithium-rich manganese-based biphase cathode slurry. (3) The carbon-coated lithium iron phosphate-lithium-rich manganese-based biphase cathode slurry is coated onto an aluminum foil substrate and then dried and pressed in sequence to obtain lithium iron phosphate-lithium-rich manganese-based biphase electrode material.

7. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 6, characterized in that, The roasting process in step (1) is as follows: the temperature is increased to 900℃ at a heating rate of 30℃ / min, and roasted at a constant temperature for 12 to 24 hours, and then cooled to room temperature at a cooling rate of 35℃ / min.

8. The in-situ preparation method of the lithium iron phosphate-lithium-rich manganese-based dual-phase electrode material as described in claim 6, characterized in that, The inorganic carbon source in step (2) is any one or more of graphite, carbon black, carbon microspheres, carbon nanospheres, carbon nanotubes, carbon nanofibers or carbon gels.

Images