Porous iron phosphate nanomaterial, and preparation method therefor and use thereof

Abstract

Provided in the present disclosure are a porous iron phosphate nanomaterial, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: mixing and reacting an iron-source-containing hydrogel microemulsion with a phosphorus-source-containing hydrogel microemulsion, so as to obtain an intermediate; and calcining the intermediate, so as to obtain the porous iron phosphate nanomaterial. In the preparation method of the present disclosure, based on a spatial confinement effect of a hydrogel template, iron phosphate nanoparticles are nucleated and grown in a network structure of the hydrogel template, thereby effectively improving the microstructure and size of a product; and a porous product can be obtained by gasifying the hydrogel, thereby effectively improving the electrochemical performance of the iron phosphate material.

Description

A porous nano-iron phosphate material and its preparation method and application Technical Field

[0001] The present disclosure belongs to the technical field of battery materials and relates to a porous nano-iron phosphate material and a preparation method and application thereof. Background Art

[0002] In recent years, lithium iron phosphate (LiFePO4) has made significant progress as a positive electrode material for lithium-ion batteries. Compared with other positive electrode materials, this material has obvious advantages in specific usage environments, such as excellent cyclability, thermal stability and safety performance. However, the LiFePO4 material is limited by its own structural characteristics. It has defects such as low electronic conductivity and small lithium ion diffusion coefficient, which limits its use in scenarios such as high-rate power batteries. Iron phosphate (FePO4) is an important precursor material for the preparation of lithium iron phosphate. After LiFePO4 is de-Li, FePO4 will be formed. The volume of the two does not change much before and after de-Li, and their morphology is also very similar. Therefore, the properties of the precursor FePO4, such as structure, particle size, morphology and dispersibility, will be carried over to the LiFePO4 positive electrode material and have an important impact on its electrochemical performance.

[0003] At present, the traditional production process of iron phosphate is mainly precipitation method, which uses phosphate and iron salt to react in solution and control the reaction conditions to produce battery-grade iron phosphate material. For example, CN 117023537A discloses a method for preparing low-temperature and highly dispersible spherical nano-iron phosphate, which includes the following steps: dissolving divalent iron salt as a base liquid, pouring soluble phosphate or phosphoric acid solution under stirring, and adding hydrogen peroxide solution to oxidize Fe 2+ , heat to 50-70℃, adjust pH with sodium hydroxide solution, react in an oil bath for 3h under constant stirring, filter the slurry while hot to obtain iron phosphate precipitate, wash with pure water, filter, dry, and calcine to obtain white iron phosphate powder.

[0004] While the precipitation method for preparing iron phosphate (FePO4) offers advantages over sol-gel, controlled crystallization, or hydrothermal methods, such as a simple process flow and relatively low energy consumption and cost, the FePO4 synthesized using this method often suffers from severe particle agglomeration, large particle size, small specific surface area, and poor compaction properties. These factors can degrade the electrochemical performance of the resulting lithium iron phosphate. To mitigate inherent defects in LiFePO4 and enhance its electrical performance, the precursor FePO4 is often modified through surface coating, ion doping, nanocrystallization, and the creation of porous structures.

[0005] Based on the above research, it is necessary to provide a preparation method for porous nano-iron phosphate materials with a simple process, regular morphology, small particle size and high dispersibility.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The purpose of the present disclosure is to provide a porous nano-iron phosphate material and its preparation method and application. The preparation method is based on the spatial confinement effect of a hydrogel template. Iron phosphate nanoparticles nucleate and grow within its network structure, effectively controlling the microscopic morphology and size of the product. The hydrogel is vaporized to obtain a porous product, effectively improving the electrochemical properties of the iron phosphate material.

[0009] To achieve this purpose, the present disclosure adopts the following technical solutions:

[0010] In a first aspect, the present disclosure provides a method for preparing a porous nano-iron phosphate material, the preparation method comprising the following steps:

[0011] (1) mixing and reacting a hydrogel microemulsion containing an iron source and a hydrogel microemulsion containing a phosphorus source to obtain an intermediate;

[0012] (2) calcining the intermediate of step (1) to obtain the porous nano-iron phosphate material.

[0013] The present invention directly adopts the mixed reaction of hydrogel microemulsion containing iron source and hydrogel microemulsion containing phosphorus source, and uses hydrogel microemulsion as template to prepare iron phosphate nanoparticles, wherein Fe is solubilized. 3+ PO4 3- The hydrogel core is used as a microreactor. After the two are mixed, the collision between the micelle particles causes the mutual exchange and transfer of substances in the water core. 3+ PO4 3- The precipitation reaction takes place in the water core, and the generated product nucleates and grows on the surface of the hydrogel's network skeleton structure and gradually transforms into spherical FePO4 materials of uniform size. Therefore, the restrictive effect of the spatial structure of the water core reactor disclosed in the present invention effectively controls the particle size of the iron phosphate particles and avoids further agglomeration of the nanoparticles.

[0014] At the same time, the hydrogel disclosed in the present invention can self-assemble into a 3D interconnected network structure. 3+ and PO4 3-The iron phosphate is complexed and adsorbed on the surface of the hydrogel. After high-temperature calcination, the hydrogel inside it vaporizes to form porous channels, which increases the specific surface area and porosity of the iron phosphate material, shortens the transmission path of lithium ions, and is beneficial to the full contact between the electrode material and the electrolyte, thereby improving the electrochemical performance of the lithium iron phosphate battery; therefore, the present invention discloses that nano-scale iron phosphate can effectively shorten the diffusion path of lithium ions and reduce the diffusion resistance of lithium ions through nano-sizing; through porosity, the porous structure can provide rich pores for the iron phosphate material, increase its specific surface area, and be beneficial to the large-scale storage and deintercalation of lithium ions.

[0015] In one embodiment, the method for preparing the hydrogel microemulsion containing an iron source or the hydrogel microemulsion containing a phosphorus source in step (1) comprises:

[0016] Mixing the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source with the organic phase solution to obtain the hydrogel microemulsion containing an iron source or the hydrogel microemulsion containing a phosphorus source;

[0017] In one embodiment, in the hydrogel solution containing an iron source, the concentration of the iron source is 0.05-0.2 mol / L, for example, it can be 0.08 mol / L, 0.1 mol / L, 0.15 mol / L or 0.18 mol / L, and in the hydrogel solution containing a phosphorus source, the concentration of the phosphorus source is 0.05-0.2 mol / L, for example, it can be 0.08 mol / L, 0.1 mol / L, 0.15 mol / L or 0.18 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] During the reaction disclosed herein, the molar ratio of iron to phosphorus is (0.9-1.1):(0.9-1.1), and can further be selected as 1:1; and the concentration of the iron source and the phosphorus source in the hydrogel solution will affect the morphology and performance of the product. If the concentrations of the iron source and the phosphorus source are both low, it may cause incomplete crystal growth of the product and low crystallinity; if the concentrations of the iron source and the phosphorus source are both high, it may cause product agglomeration.

[0019] In one embodiment, the pH of the hydrogel solution containing the iron source is adjusted before the hydrogel solution containing the iron source is mixed with the organic phase solution.

[0020] In one embodiment, the pH is adjusted to 1.8-2.2, for example, 1.9, 2.0, 2.1 or 2.2, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] In one embodiment, the volumes of the hydrogel solution containing an iron source and the hydrogel solution containing a phosphorus source are independently smaller than the volume of the organic phase solution.

[0022] The mixing of the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source with the organic phase solution disclosed herein comprises dripping the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source into the organic phase solution, wherein the volume of the water phase is smaller than that of the oil phase, thereby forming a water-in-oil state.

[0023] In one embodiment, the method for preparing the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source comprises:

[0024] The amine substance, organic acid and water are mixed with the iron source or phosphorus source to obtain the hydrogel solution containing the iron source or the hydrogel solution containing the phosphorus source.

[0025] In one embodiment, the amine substance includes any one or a combination of at least two of melamine, dimethylacrylamide, polyethylene glycol diamine or polyethylene imine.

[0026] In one embodiment, the organic acid includes any one of o-hydroxybenzoic acid, maleic acid, succinic acid or glycolic acid, or a combination of at least two thereof.

[0027] In the process of preparing the hydrogel solution, melamine and o-hydroxybenzoic acid self-assemble into a 3D interconnected network structure in an aqueous medium through intermolecular hydrogen bonding forces. The three-dimensional structure is composed of cross-linked hydrogel nanowires, so that Fe 3+ and PO4 3- The iron phosphate is complexed and adsorbed on the surface of the hydrogel nanowires. After the generated iron phosphate is calcined at high temperature, the hydrogel nanowires inside it vaporize to form porous channels, thereby obtaining a porous structure of the iron phosphate.

[0028] In one embodiment, the amount of the amine substance added is 0.02-0.03 mol, for example, it can be 0.021 mol, 0.023 mol, 0.025 mol, 0.027 mol or 0.029 mol, and the amount of the organic acid added is 0.02-0.03 mol, for example, it can be 0.021 mol, 0.023 mol, 0.025 mol, 0.027 mol or 0.029 mol, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] In one embodiment, the volume of water is 20-30 mL, for example, 22 mL, 25 mL, 27 mL or 30 mL, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] In one embodiment, the organic phase solution includes a surfactant, a co-surfactant and an organic solvent.

[0031] In one embodiment, the method for preparing the organic phase solution comprises mixing a surfactant, a co-surfactant and an organic solvent to obtain an organic phase solution.

[0032] In one embodiment, the mass ratio of the surfactant to the co-surfactant is (20-25):1, for example, it can be 20:1, 22:1, 24:1 or 25:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In one embodiment, the surfactant comprises Triton X-100 (polyethylene glycol octylphenyl ether).

[0034] In one embodiment, the co-surfactant comprises n-hexanol.

[0035] In one embodiment, the organic solvent comprises n-heptane.

[0036] In one embodiment, the reaction temperature of step (1) is 70-90°C, for example, 75°C, 80°C, 85°C or 90°C, and the reaction time is 4-10h, for example, 5h, 8h or 10h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] In one embodiment, after the reaction in step (1) is completed, aging, solid-liquid separation, washing and drying are further performed.

[0038] In one embodiment, the aging time is 3-5 hours, for example, 3 hours, 4 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] In one embodiment, the iron source comprises ferric nitrate and / or ferric chloride.

[0040] In one embodiment, the phosphorus source includes any one of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, or sodium hydrogen phosphate, or a combination of at least two thereof.

[0041] In one embodiment, the calcination temperature in step (2) is 500-750°C, for example, 550°C, 650°C, 700°C or 750°C, and the calcination time is 4-10h, for example, 5h, 8h or 10h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] As an optional technical solution of the preparation method disclosed in the present invention, the preparation method comprises the following steps:

[0043] (1) mixing 0.02-0.03 mol of an amine substance, 0.02-0.03 mol of an organic acid, and 20-30 mL of water with an iron source or a phosphorus source to obtain a hydrogel solution containing an iron source or a hydrogel solution containing a phosphorus source, wherein the concentration of the iron source in the hydrogel solution containing the iron source is 0.05-0.2 mol / L, and the concentration of the phosphorus source in the hydrogel solution containing the phosphorus source is 0.05-0.2 mol / L;

[0044] The hydrogel solution containing the iron source is adjusted to pH 1.8-2.2, and then mixed with the organic phase solution to obtain a hydrogel microemulsion containing the iron source;

[0045] mixing the hydrogel solution containing the phosphorus source with the organic phase solution to obtain a hydrogel microemulsion containing the phosphorus source;

[0046] The organic phase solution includes a surfactant, a cosurfactant and an organic solvent;

[0047] (2) mixing the hydrogel microemulsion containing an iron source described in step (1) with the hydrogel microemulsion containing a phosphorus source described in step (1), and then reacting at 70-90° C. for 4-10 hours, aging for 3-5 hours after the reaction, and then performing solid-liquid separation, washing, and drying to obtain an intermediate;

[0048] (3) calcining the intermediate of step (2) at 500-750° C. for 4-10 hours to obtain the porous nano-iron phosphate material.

[0049] In a second aspect, the present disclosure provides a porous nano-iron phosphate material, which is prepared by the preparation method described in the first aspect.

[0050] In a third aspect, the present disclosure provides a lithium iron phosphate material, which is obtained by mixing and calcining a lithium source, a carbon source, and the porous nano-iron phosphate material as described in the second aspect.

[0051] In one embodiment, the molar ratio of the porous nano-iron phosphate material, the lithium source and the carbon source is (1-1.1):1:(0.1-0.15), for example, it can be 1:1:0.12, 1.05:1:0.14 or 1.1:1:0.15, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] In one embodiment, the calcination temperature is 650-750°C, for example, 680°C, 700°C or 750°C, and the calcination time is 6-10h, for example, 6h, 8h or 10h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In one embodiment, the calcination is performed in a protective gas comprising nitrogen or argon.

[0054] The method of mixing the lithium source, carbon source and the porous nano-iron phosphate material disclosed in the present invention includes ball milling, the grinding medium is ethanol, and the ball milling time is 2-5 hours, for example, it can be 3 hours, 4 hours or 5 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] In one embodiment, the lithium source includes any one of lithium carbonate, lithium hydroxide or lithium acetate, or a combination of at least two thereof, and the carbon source includes any one of glucose, sucrose, starch or cellulose, or a combination of at least two thereof.

[0056] Compared with the prior art, the present disclosure has the following beneficial effects:

[0057] The present invention uses a hydrogel microemulsion as a template, reacts a hydrogel microemulsion containing an iron source with a hydrogel microemulsion containing a phosphorus source, and produces iron phosphate nanospheres. The morphology and size of the material well maintain the microstructure of the microemulsion. In addition, the spherical iron phosphate prepared in the present invention has a porous structure, which increases the specific surface area and porosity of the iron phosphate material, shortens the transmission path of lithium ions, and improves the electrochemical performance of lithium iron phosphate batteries. At the same time, the preparation method described in the present invention has the advantages of simple equipment, easy operation, low energy consumption, and industrial production capability.

[0058] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0060] FIG1 is a scanning electron microscope image of the nanoporous nano-iron phosphate material obtained in Example 1 of the present disclosure;

[0061] FIG2 is a flow chart of the preparation method described in Example 1 of the present disclosure;

[0062] FIG3 is an XRD diagram of the nanoporous nano-iron phosphate material obtained in Example 1 of the present disclosure. DETAILED DESCRIPTION

[0063] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0064] Example 1

[0065] This embodiment provides a method for preparing a porous nano-iron phosphate material. The flow chart of the preparation method is shown in FIG2 . 3+ Hydrogel microemulsion and PO4 3- The product can be obtained by mixing the hydrogel microemulsion and reflux heating, washing and high-temperature calcination;

[0066] The specific preparation method comprises the following steps:

[0067] (1) 0.025 mol of melamine, 0.025 mol of o-hydroxybenzoic acid and 25 mL of deionized water were mixed with 0.0013 mol of iron source or 0.0013 mol of phosphorus source, stirred for 15 min, and then the mixture was heated at 70 ° C and stirred for 30 min to obtain Fe-containing 3+ Hydrogel solution or PO4 3- hydrogel solution;

[0068] The iron source is ferric chloride, containing Fe 3+ In the hydrogel solution, the concentration of the iron source is 0.052 mol / L; the phosphorus source is ammonium dihydrogen phosphate, containing PO4 3- In the hydrogel solution, the concentration of the phosphorus source is 0.052 mol / L;

[0069] Containing Fe 3+ After adjusting the pH of the hydrogel solution to 2, it was added dropwise into the organic phase solution under stirring and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain Fe-containing 3+ hydrogel microemulsion;

[0070] Contains PO4 3- The hydrogel solution was added dropwise into the organic phase solution under stirring conditions and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain a PO4-containing 3- hydrogel microemulsion;

[0071] The organic phase solution includes Triton X-100, n-hexanol and n-heptane, and is obtained by dispersing 1.5 g of Triton X-100, 0.08 g of n-hexanol and 80 mL of n-heptane;

[0072] (2) the Fe-containing 3+ The hydrogel microemulsion and the PO4-containing 3-The mixture was mixed with a hydrogel microemulsion, stirred at room temperature for 30 minutes, transferred to a reflux reaction device and heated, reacted at 80°C for 8 hours, aged for 5 hours after the reaction, and then centrifuged to collect the product. The product was washed several times with deionized water, acetone and anhydrous ethanol, and then dried in a vacuum oven at 100°C for 12 hours to obtain FePO4·2H2O material.

[0073] (3) The FePO4·2H2O material described in step (2) is placed in a muffle furnace and calcined at 650°C for 8 hours at a heating rate of 8°C / min to obtain the anhydrous porous nano-iron phosphate material. The scanning electron microscope image of the porous nano-iron phosphate material is shown in Figure 1, and the XRD pattern is shown in Figure 3. As can be seen from Figure 3, the peak positions of the porous nano-iron phosphate material obtained in the present invention correspond to those of the standard iron phosphate card.

[0074] Example 2

[0075] This embodiment provides a method for preparing a porous nano-iron phosphate material, the preparation method comprising the following steps:

[0076] (1) 0.02 mol of melamine, 0.02 mol of o-hydroxybenzoic acid and 20 mL of deionized water were mixed with 0.001 mol of iron source or 0.001 mol of phosphorus source, stirred for 15 min, and then the mixture was heated at 70 ° C and stirred for 30 min to obtain Fe-containing 3+ Hydrogel solution or PO4 3- hydrogel solution;

[0077] The iron source is ferric chloride, containing Fe 3+ In the hydrogel solution, the concentration of the iron source is 0.05 mol / L; the phosphorus source is ammonium dihydrogen phosphate, containing PO4 3- In the hydrogel solution, the concentration of the phosphorus source is 0.05 mol / L;

[0078] Containing Fe 3+ After adjusting the pH of the hydrogel solution to 1.8, it was added dropwise into the organic phase solution under stirring and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain Fe-containing 3+ hydrogel microemulsion;

[0079] Contains PO4 3- The hydrogel solution was added dropwise into the organic phase solution under stirring conditions and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain a PO4-containing 3- hydrogel microemulsion;

[0080] The organic phase solution includes Triton X-100, n-hexanol and n-heptane, and is obtained by dispersing 1.5 g of Triton X-100, 0.08 g of n-hexanol and 80 mL of n-heptane;

[0081] (2) the Fe-containing 3+ The hydrogel microemulsion and the PO4-containing 3- The mixture was mixed with a hydrogel microemulsion, stirred at room temperature for 30 minutes, transferred to a reflux reaction device and heated, reacted at 70°C for 10 hours, aged for 4 hours after the reaction, and then centrifuged to collect the product. The product was washed several times with deionized water, acetone and anhydrous ethanol, and then dried in a vacuum oven at 100°C for 12 hours to obtain FePO4·2H2O material.

[0082] (3) The FePO4·2H2O material prepared in step (2) was placed in a muffle furnace and calcined at 600°C for 8 hours at a heating rate of 8°C / min to obtain the anhydrous porous nano-iron phosphate material.

[0083] Example 3

[0084] This embodiment provides a method for preparing a porous nano-iron phosphate material, the preparation method comprising the following steps:

[0085] (1) 0.025 mol of dimethylacrylamide, 0.025 mol of succinic acid and 25 mL of water were mixed with 0.0025 mol of iron source or 0.0025 mol of phosphorus source, stirred for 15 min, and then the mixture was heated at 70 ° C and stirred for 30 min to obtain Fe-containing 3+ Hydrogel solution or PO4 3- hydrogel solution;

[0086] The iron source is ferric chloride, containing Fe 3+ In the hydrogel solution, the concentration of the iron source is 0.1 mol / L; the phosphorus source is ammonium dihydrogen phosphate, containing PO4 3- In the hydrogel solution, the concentration of the phosphorus source is 0.1 mol / L;

[0087] Containing Fe 3+ After adjusting the pH of the hydrogel solution to 2, it was added dropwise into the organic phase solution under stirring and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain Fe-containing 3+ hydrogel microemulsion;

[0088] Contains PO4 3-The hydrogel solution was added dropwise into the organic phase solution under stirring conditions and stirred at 50 ° C for 1.5 h. After cooling to room temperature, stirring was continued for 30 min to obtain a PO4-containing 3- hydrogel microemulsion;

[0089] The organic phase solution includes Triton X-100, n-hexanol and n-heptane, and is obtained by dispersing 2 g of Triton X-100, 0.08 g of n-hexanol and 80 mL of n-heptane;

[0090] (2) the Fe-containing 3+ The hydrogel microemulsion and the PO4-containing 3- The mixture was mixed with a hydrogel microemulsion, stirred at room temperature for 30 minutes, transferred to a reflux reaction device and heated, reacted at 90°C for 4 hours, aged for 4 hours after the reaction, and then centrifuged to collect the product. The product was washed several times with deionized water, acetone and anhydrous ethanol, and then dried in a vacuum oven at 100°C for 12 hours to obtain FePO4·2H2O material.

[0091] (3) The FePO4·2H2O material described in step (2) is placed in a muffle furnace and calcined at 650°C for 10 hours at a heating rate of 8°C / min to obtain the anhydrous porous nano-iron phosphate material.

[0092] Example 4

[0093] This embodiment provides a method for preparing a porous nano-iron phosphate material. The preparation method is the same as that of Example 1 except that the reaction temperature in step (2) is 60°C.

[0094] Example 5

[0095] This embodiment provides a method for preparing a porous nano-iron phosphate material. The preparation method is the same as that of Example 1 except that the reaction temperature in step (2) is 100°C.

[0096] Example 6

[0097] This embodiment provides a method for preparing a porous nano-iron phosphate material. In addition to reducing the amount of iron source and phosphorus source added, the preparation method makes the Fe-containing 3+ In the hydrogel solution, the concentration of the iron source is 0.02 mol / L, and the PO4 3- The hydrogel solution was the same as in Example 1 except that the concentration of the phosphorus source was 0.02 mol / L.

[0098] Example 7

[0099] This embodiment provides a method for preparing a porous nano-iron phosphate material. In addition to increasing the amount of iron source and phosphorus source added, the Fe-containing 3+ In the hydrogel solution, the concentration of the iron source is 0.2 mol / L, and the PO4 3- In the hydrogel solution, the concentration of the phosphorus source was 0.2 mol / L, and the rest was the same as in Example 1.

[0100] Example 8

[0101] This embodiment provides a method for preparing a porous nano-iron phosphate material. In addition to increasing the amount of iron source and phosphorus source added, the Fe-containing 3+ In the hydrogel solution, the concentration of the iron source is 0.3 mol / L, and the PO4 3- The hydrogel solution was the same as in Example 1 except that the concentration of the phosphorus source was 0.3 mol / L.

[0102] Comparative Example 1

[0103] This comparative example provides a method for preparing an iron phosphate material, which is the same as Example 1 except that step (1) is not performed and the iron source aqueous solution and the phosphorus source aqueous solution are directly mixed and reacted in step (2);

[0104] The iron source aqueous solution in this comparative example was obtained by dispersing 0.0013 mol ferric chloride in 25 mL deionized water and ultrasonically treating it for 15 minutes. The phosphorus source aqueous solution was obtained by dispersing 0.0013 mol ammonium dihydrogen phosphate in 25 mL deionized water and ultrasonically treating it for 15 minutes.

[0105] Comparative Example 2

[0106] This comparative example provides a method for preparing an iron phosphate material. The method includes the following steps: step (1) wherein melamine and o-hydroxybenzoic acid are not added to obtain an iron phosphate material. 3+ The reverse microemulsion and PO4 3- Except for the reverse microemulsion, the rest are the same as in Example 1.

[0107] Lithium carbonate, the iron phosphate material obtained in the above embodiments and comparative examples, and glucose were dispersed in anhydrous ethanol according to a stoichiometric ratio of lithium source, iron source, and carbon source of 1:1.04:0.12, ball-milled for 3 h until uniformly mixed at a rotation speed of 3000 rpm, and then spray-dried to obtain a precursor powder. Subsequently, the precursor powder was heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere and kept warm for 1.5 h, and then heated to 700°C and calcined at a high temperature for 8 h to obtain LiFePO4 / C positive electrode material; the obtained positive electrode material was prepared into a button battery for lithium ion battery electrochemical performance test (the charge and discharge voltage was controlled between 2.5-4.5 V).

[0108] The test results are shown in the following table:

[0109] Table 1

[0110] From Table 1 we can see the following:

[0111] The present invention uses hydrogel microemulsion as a template to directly 3+ Hydrogel microemulsion with PO4 3- The hydrogel microemulsion of the embodiment 1 is directly mixed and reacted, which can significantly improve the electrochemical performance of iron phosphate and obtain a battery with excellent electrochemical performance; it can be seen from Example 1 and Comparative Examples 1-2 that Comparative Example 1 directly uses Fe 3+ Aqueous solution containing PO4 3- In Example 1, solid irregular iron phosphate blocks were obtained by reaction with an aqueous solution of 2% Fe 2+, and solid spherical iron phosphate particles were obtained by reaction with an inverse microemulsion. Therefore, the electrochemical performance of the obtained battery was significantly reduced. It can be seen from Example 1 and Examples 4-8 that the reaction temperature and the concentrations of the iron source and phosphorus source will affect the reaction results, thereby affecting the battery performance.

[0112] In summary, the present disclosure provides a porous nano-iron phosphate material and its preparation method and application. The preparation method is based on the spatial confinement effect of the hydrogel template. Iron phosphate nanoparticles nucleate and grow inside its network structure, effectively controlling the microscopic morphology and size of the product. The hydrogel gasification can obtain a porous product, which effectively improves the electrochemical properties of the iron phosphate material.

Claims

1. A method for preparing a porous nano iron phosphate material, comprising the following steps: (1) Mixing and reacting a hydrogel microemulsion containing an iron source with a hydrogel microemulsion containing a phosphorus source to obtain an intermediate; (2) Calcining the intermediate obtained in step (1) to obtain the porous nano iron phosphate material.

2. The preparation method according to claim 1, wherein, The method for preparing the hydrogel microemulsion containing an iron source or the hydrogel microemulsion containing a phosphorus source in step (1) includes: Mixing a hydrogel solution containing an iron source or a hydrogel solution containing a phosphorus source with an organic phase solution to obtain the hydrogel microemulsion containing an iron source or the hydrogel microemulsion containing a phosphorus source.

3. The preparation method according to claim 1 or 2, wherein In the hydrogel solution containing an iron source, the concentration of the iron source is 0.05 - 0.2 mol / L, and in the hydrogel solution containing a phosphorus source, the concentration of the phosphorus source is 0.05 - 0.2 mol / L.

4. The preparation method according to claim 2 or 3, wherein Before mixing the hydrogel solution containing an iron source with the organic phase solution, the pH of the hydrogel solution containing an iron source is adjusted first; Optionally, the pH is adjusted to 1.8 - 2.

2.

5. The preparation method according to any one of claims 2-4, wherein, The volumes of the hydrogel solution containing an iron source and the hydrogel solution containing a phosphorus source are each independently less than the volume of the organic phase solution.

6. The preparation method according to any one of claims 2-5, wherein, The method for preparing the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source includes: Mixing an amine substance, an organic acid, and water with an iron source or a phosphorus source to obtain the hydrogel solution containing an iron source or the hydrogel solution containing a phosphorus source.

7. The preparation method according to claim 6, wherein, The amine substance includes any one or a combination of at least two of melamine, dimethylacrylamide, polyethylene glycol diamine, or polyethyleneimine.

8. The preparation method according to claim 6 or 7, wherein The organic acid includes any one or a combination of at least two of o-hydroxybenzoic acid, maleic acid, succinic acid, or glycolic acid.

9. The preparation method according to any one of claims 6-8, wherein, The addition amount of the amine substance is 0.02 - 0.03 mol, and the addition amount of the organic acid is 0.02 - 0.03 mol.

10. The preparation method according to any one of claims 6-9, wherein, The volume of the water is 20 - 30 mL.

11. The preparation method according to any one of claims 2-10, wherein, The organic phase solution includes a surfactant, a co-surfactant, and an organic solvent; Optionally, the method for preparing the organic phase solution includes mixing a surfactant, a co-surfactant, and an organic solvent to obtain an organic phase solution; Optionally, the mass ratio of the surfactant to the co-surfactant is (20 - 25):1; Optionally, the surfactant includes Triton X-100; Optionally, the co-surfactant includes n-hexanol; Optionally, the organic solvent includes n-heptane.

12. The preparation method according to any one of claims 1-11, wherein, The temperature of the reaction in step (1) is 70 - 90 °C, and the time is 4 - 10 h; Optionally, after the reaction in step (1), aging, solid-liquid separation, washing, and drying are also carried out; Optionally, the aging time is 3 - 5 h; Optionally, the calcination temperature in step (2) is 500 - 750 °C, and the time is 4 - 10 h.

13. The preparation method according to any one of claims 1-12, wherein, The preparation method includes the following steps: (1) Mix 0.02 - 0.03 mol of an amine substance, 0.02 - 0.03 mol of an organic acid, and 20 - 30 mL of water with an iron source or a phosphorus source to obtain an iron-source-containing hydrogel solution or a phosphorus-source-containing hydrogel solution. In the iron-source-containing hydrogel solution, the concentration of the iron source is 0.05 - 0.2 mol / L, and in the phosphorus-source-containing hydrogel solution, the concentration of the phosphorus source is 0.05 - 0.2 mol / L; After adjusting the pH of the iron-source-containing hydrogel solution to 1.8 - 2.2, mix it with an organic phase solution to obtain an iron-source-containing hydrogel microemulsion; Mix the phosphorus-source-containing hydrogel solution with an organic phase solution to obtain a phosphorus-source-containing hydrogel microemulsion; The organic phase solution includes a surfactant, a co-surfactant, and an organic solvent; (2) Mix the iron-source-containing hydrogel microemulsion obtained in step (1) with the phosphorus-source-containing hydrogel microemulsion obtained in step (1), then react at 70 - 90 °C for 4 - 10 h. After the reaction ends, carry out aging for 3 - 5 h, then perform solid-liquid separation, washing, and drying to obtain an intermediate; (3) Calcinate the intermediate obtained in step (2) at 500 - 750 °C for 4 - 10 h to obtain the porous nano iron phosphate material.

14. A porous nano iron phosphate material prepared by the preparation method according to any one of claims 1 - 13.

15. A lithium iron phosphate material obtained by mixing and calcining a lithium source, a carbon source, and the porous nano iron phosphate material according to claim 8.

16. The lithium iron phosphate material according to claim 15, wherein, The molar ratio of the porous nano iron phosphate material, the lithium source, and the carbon source is (1 - 1.1):1:(0.1 - 0.15); Optionally, the calcination temperature is 650 - 750 °C and the time is 6 - 10 h.

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