A porous nanometer iron phosphate material, a preparation method thereof and application thereof

Abstract

The present disclosure provides a porous nanometer iron phosphate material, a preparation method and application thereof. The preparation method comprises the following steps: mixing and reacting an iron source-containing hydrogel microemulsion and a phosphorus source-containing hydrogel microemulsion to obtain an intermediate; and calcining the intermediate to obtain the porous nanometer iron phosphate material. The preparation method is based on the space confinement effect of the hydrogel template, which enables the nucleation and growth of iron phosphate nanoparticles inside the network structure, effectively controls the micro-morphology and size of the product, and the gasification of the hydrogel can obtain a porous product, effectively improving the electrochemical performance of the iron phosphate material.

Description

Technical Field

[0001] This disclosure belongs to the field of battery materials technology, and relates to a porous nano-iron phosphate material, its preparation method and application. Background Technology

[0002] In recent years, lithium iron phosphate (LiFePO4) has seen significant development as a cathode material for lithium-ion batteries. Compared to other cathode materials, it exhibits clear advantages in specific application environments, such as excellent cycle performance, thermal stability, and safety. However, LiFePO4 is limited by its structural characteristics, exhibiting low electronic conductivity and a small lithium-ion diffusion coefficient, which restricts its use in high-rate power batteries and other applications. Iron phosphate (FePO4) is an important precursor material for the preparation of lithium iron phosphate. After Li removal from LiFePO4, FePO4 is formed. The volume change between the two before and after delithiation is minimal, and their morphologies are extremely similar. Therefore, the properties of the precursor FePO4, such as its structure, particle size, morphology, and dispersibility, are carried over to the LiFePO4 cathode material and significantly influence its electrochemical performance.

[0003] Currently, the traditional production process of iron phosphate mainly involves precipitation, which uses the reaction of phosphate and iron salt in solution and controls the reaction conditions to obtain battery-grade iron phosphate materials. For example, CN 117023537A discloses a method for preparing low-temperature, highly dispersible spherical nano-iron phosphate, which includes the following steps: dissolving ferrous iron salt as a base liquid, pouring in a soluble phosphate or phosphoric acid solution while stirring, and adding hydrogen peroxide solution dropwise to oxidize Fe. 2+ The temperature was raised to 50-70℃, the pH was adjusted with sodium hydroxide solution, and the mixture was reacted in an oil bath for 3 hours with constant stirring. The slurry was filtered while hot to obtain ferric phosphate precipitate, which was washed with pure water, filtered, dried, and calcined to obtain white ferric phosphate powder.

[0004] Compared to sol-gel, controlled crystallization, or hydrothermal methods, the precipitation method for preparing iron phosphate has advantages such as simple process flow, relatively low energy consumption, and low cost. However, the iron phosphate synthesized by this method often suffers from severe particle agglomeration, large particle size, small specific surface area, and poor compaction performance. These issues all degrade the electrochemical performance of the lithium iron phosphate materials prepared from it. Typically, to improve the inherent defects of LiFePO4 and enhance its electrical properties, surface coating, ion doping, nanostructuring, and the construction of porous structures are used to modify the precursor iron phosphate material.

[0005] Based on the above research, there is a need to provide a simple process for preparing porous iron phosphate nanomaterials with regular morphology, small particle size and high dispersibility. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] The purpose of this disclosure is to provide a porous nano-iron phosphate material, its preparation method and application. The preparation method is based on the spatial confinement effect of the hydrogel template, in which iron phosphate nanoparticles nucleate and grow within its network structure, effectively controlling the microstructure and size of the product. Furthermore, the hydrogel vaporization can yield porous products, effectively improving the electrochemical performance of the iron phosphate material.

[0008] To achieve this objective, the present disclosure adopts the following technical solution:

[0009] In a first aspect, this disclosure provides a method for preparing porous nano-iron phosphate materials, the method comprising the following steps:

[0010] (1) Mix and react an iron-containing hydrogel microemulsion with a phosphorus-containing hydrogel microemulsion to obtain an intermediate;

[0011] (2) The intermediate in step (1) is calcined to obtain the porous nano-iron phosphate material.

[0012] This disclosure directly uses an iron-containing hydrogel microemulsion and a phosphorus-containing hydrogel microemulsion to react, and uses the hydrogel microemulsion as a template to prepare iron phosphate nanospheres, wherein Fe is solubilized. 3+ PO4 3- The hydrogel core acts as a microreactor. After mixing, due to collisions between the micelle particles, the exchange and transfer of substances within the water core occur. Fe... 3 + PO4 3- The precipitation reaction takes place within the water core, and the resulting product nucleates and grows on the surface of the hydrogel's network framework structure, gradually transforming into uniformly sized spherical FePO4 materials. Therefore, the spatial confinement effect of the water core reactor disclosed in this invention effectively controls the particle size of iron phosphate particles and avoids further aggregation of nanoparticles.

[0013] Simultaneously, the hydrogel disclosed herein can self-assemble into a 3D interconnected network structure, Fe 3+ and PO4 3-The iron phosphate generated by complexing and adsorbing onto the surface of the hydrogel undergoes high-temperature calcination, during which the internal hydrogel vaporizes to form porous channels. This increases the specific surface area and porosity of the iron phosphate material, shortens the lithium ion transport path, and facilitates full contact between the electrode material and the electrolyte, thereby improving the electrochemical performance of the lithium iron phosphate battery. Therefore, this disclosure utilizes nano-sizing, where nano-sized iron phosphate can effectively shorten the lithium ion diffusion path and reduce the lithium ion diffusion resistance. Furthermore, through porousization, the porous structure provides abundant channels for the iron phosphate material, increasing its specific surface area and facilitating the large-scale storage and deintercalation of lithium ions.

[0014] In one embodiment, the method for preparing the iron-containing hydrogel microemulsion or the phosphorus-containing hydrogel microemulsion of step (1) includes:

[0015] An iron-containing hydrogel solution or a phosphorus-containing hydrogel solution is mixed with an organic phase solution to obtain the iron-containing hydrogel microemulsion or the phosphorus-containing hydrogel microemulsion.

[0016] In one embodiment, the concentration of the iron source in the iron-containing hydrogel solution 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. In the phosphorus-containing hydrogel solution, 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. Other unlisted values ​​within the range are also applicable.

[0017] In this reaction, the molar ratio of iron to phosphorus is (0.9-1.1):(0.9-1.1), and can be further selected as 1:1. The concentrations of iron and phosphorus sources in the hydrogel solution affect the morphology and properties of the product. If the concentrations of both iron and phosphorus sources are low, the crystal growth of the product may be incomplete and the crystallinity may be low. If the concentrations of both iron and phosphorus sources are high, the product may agglomerate.

[0018] In one embodiment, the pH of the iron-containing hydrogel solution is adjusted before mixing it with the organic phase solution.

[0019] In one embodiment, the pH adjustment to 1.8-2.2 may be, for example, 1.9, 2.0, 2.1 or 2.2, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0020] In one embodiment, the volumes of the iron-containing hydrogel solution and the phosphorus-containing hydrogel solution are each independently smaller than the volume of the organic phase solution.

[0021] The present invention discloses a method for mixing an iron-containing hydrogel solution or a phosphorus-containing hydrogel solution with an organic phase solution, comprising dropping the iron-containing hydrogel solution or the phosphorus-containing hydrogel solution into the organic phase solution, wherein the volume of the aqueous phase is smaller than that of the oil phase, thereby forming a water-in-oil state.

[0022] In one embodiment, a method for preparing the iron-containing hydrogel solution or the phosphorus-containing hydrogel solution includes:

[0023] Amines, organic acids, and water are mixed with an iron source or a phosphorus source to obtain the hydrogel solution containing the iron source or the hydrogel solution containing the phosphorus source.

[0024] In one embodiment, the amine substance includes any one or a combination of at least two of melamine, dimethacrylamide, polyethylene glycol diamine, or polyethyleneimine.

[0025] In one embodiment, the organic acid includes any one or a combination of at least two of o-hydroxybenzoic acid, maleic acid, succinic acid, or ethylene glycol dicarboxylic acid.

[0026] In the preparation of the hydrogel solution, melamine and o-hydroxybenzoic acid self-assemble into a 3D interconnected network structure in an aqueous medium through intermolecular hydrogen bonding. This three-dimensional structure is composed of cross-linked hydrogel nanowires, enabling Fe... 3+ and PO4 3- The iron phosphate generated by complexing and adsorbing on the surface of hydrogel nanowires is calcined at high temperature, and the hydrogel nanowires inside vaporize to form porous channels, thus giving the iron phosphate a porous structure.

[0027] In one embodiment, the amount of the amine added is 0.02-0.03 mol, for example, 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, 0.021 mol, 0.023 mol, 0.025 mol, 0.027 mol, or 0.029 mol, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] In one embodiment, the volume of the water is 20-30 mL, for example, 22 mL, 25 mL, 27 mL or 30 mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] In one embodiment, the organic phase solution includes a surfactant, a co-surfactant, and an organic solvent.

[0030] In one embodiment, the method for preparing the organic phase solution includes mixing a surfactant, a co-surfactant, and an organic solvent to obtain the organic phase solution.

[0031] 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. Other unlisted values ​​within the range are also applicable.

[0032] In one embodiment, the surfactant includes Triton X-100 (polyethylene glycol octylphenyl ether).

[0033] In one embodiment, the co-surfactant comprises n-hexanol.

[0034] In one embodiment, the organic solvent includes n-heptane.

[0035] In one embodiment, the temperature of the reaction in step (1) is 70-90°C, for example, 75°C, 80°C, 85°C or 90°C, and the time is 4-10h, for example, 5h, 8h or 10h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] In one embodiment, after the reaction described in step (1) is completed, aging, solid-liquid separation, washing and drying are also performed.

[0037] In one embodiment, the aging time is 3-5 hours, for example, 3 hours, 4 hours or 5 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] In one embodiment, the iron source includes ferric nitrate and / or ferric chloride.

[0039] In one embodiment, the phosphorus source includes any one or a combination of at least two of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, or sodium hydrogen phosphate.

[0040] 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 time is 4-10h, for example, 5h, 8h or 10h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] As an optional technical solution for the preparation method described in this disclosure, the preparation method includes the following steps:

[0042] (1) Mix 0.02-0.03 mol of amine, 0.02-0.03 mol of 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. 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.

[0043] After adjusting the pH of the iron-containing hydrogel solution to 1.8-2.2, it was mixed with the organic phase solution to obtain an iron-containing hydrogel microemulsion.

[0044] A phosphorus-containing hydrogel solution was mixed with an organic phase solution to obtain a phosphorus-containing hydrogel microemulsion.

[0045] The organic phase solution includes surfactants, co-surfactants, and organic solvents;

[0046] (2) The iron-containing hydrogel microemulsion described in step (1) is mixed with the phosphorus-containing hydrogel microemulsion described in step (1), and then reacted at 70-90℃ for 4-10h. After the reaction is completed, the mixture is aged for 3-5h, and then solid-liquid separation, washing and drying are performed to obtain the intermediate.

[0047] (3) The intermediate described in step (2) is calcined at 500-750°C for 4-10 hours to obtain the porous nano-iron phosphate material.

[0048] Secondly, this disclosure provides a porous nano-iron phosphate material, which is prepared by the preparation method described in the first aspect.

[0049] Thirdly, this disclosure provides a lithium iron phosphate material, which is obtained by mixing and calcining a lithium source, a carbon source, and a porous nano-iron phosphate material as described in the second aspect.

[0050] 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. Other unlisted values ​​within the range are also applicable.

[0051] In one embodiment, the calcination temperature is 650-750°C, for example, 680°C, 700°C or 750°C, and the time is 6-10h, for example, 6h, 8h or 10h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In one embodiment, the calcination is carried out in a protective gas, which includes nitrogen or argon.

[0053] The method of mixing the lithium source, carbon source and the porous nano-iron phosphate material disclosed herein includes ball milling, with ethanol as the grinding medium, and the ball milling time being 2-5 hours, for example, 3 hours, 4 hours or 5 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In one embodiment, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide, or lithium acetate, and the carbon source includes any one or a combination of at least two of glucose, sucrose, starch, or cellulose.

[0055] Compared with the prior art, this disclosure has the following beneficial effects:

[0056] This disclosure uses hydrogel microemulsions as templates to react iron-containing hydrogel microemulsions with phosphorus-containing hydrogel microemulsions to prepare iron phosphate nanospheres. The morphology and size of the materials well maintain the microstructure of the microemulsions. Furthermore, the spherical iron phosphate prepared by this disclosure has a porous structure, which increases the specific surface area and porosity of the iron phosphate material, shortens the lithium-ion transport path, and improves the electrochemical performance of lithium iron phosphate batteries. At the same time, the preparation method described in this disclosure has the advantages of simple equipment, easy operation, low energy consumption, and industrial production capability.

[0057] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0058] The accompanying drawings are provided to further understand the technical solutions herein and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions herein and do not constitute a limitation on the technical solutions herein.

[0059] Figure 1 This is a scanning electron microscope image of the nanoporous iron phosphate nanomaterial obtained in Example 1 of this disclosure;

[0060] Figure 2 This is a flowchart of the preparation method described in Embodiment 1 of this disclosure;

[0061] Figure 3 The image shows the XRD pattern of the nanoporous iron phosphate material obtained in Example 1 of this disclosure. Detailed Implementation

[0062] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0063] Example 1

[0064] This embodiment provides a method for preparing porous nano-iron phosphate materials, the flowchart of which is shown below. Figure 2 As shown, Fe 3+ Hydrogel microemulsions and PO4-containing 3- The product can be obtained by mixing and refluxing the hydrogel microemulsion, followed by washing and high-temperature calcination.

[0065] The specific preparation method includes the following steps:

[0066] (1) Mix 0.025 mol of melamine, 0.025 mol of o-hydroxybenzoic acid, and 25 mL of deionized water with 0.0013 mol of iron source or 0.0013 mol of phosphorus source. After stirring for 15 min, heat the mixture at 70 °C and continue stirring for 30 min to obtain a solution containing Fe. 3+ Hydrogel solutions or containing PO4 3- Hydrogel solution;

[0067] 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;

[0068] Fe 3+ After adjusting the pH of the hydrogel solution to 2, it was added dropwise to 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 microemulsions;

[0069] Will contain PO4 3- The hydrogel solution was added dropwise to 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 a solution containing PO4. 3- Hydrogel microemulsions;

[0070] The organic phase solution comprises Triton X-100, n-hexanol, and n-heptane, and is obtained by dispersing 1.5 g Triton X-100, 0.08 g n-hexanol, and 80 mL n-heptane.

[0071] (2) The Fe-containing material described in step (1) 3+ The hydrogel microemulsion and the PO4-containing solution described in step (1) 3-The hydrogel microemulsion was mixed and stirred at room temperature for 30 min. Then it was transferred to a reflux reaction apparatus and heated. The reaction was carried out at 80℃ for 8 h. After the reaction was completed, it was aged for 5 h. Then the product was collected by centrifugation and washed several times with deionized water, acetone and anhydrous ethanol. Then it was dried in a vacuum oven at 100℃ for 12 h to obtain FePO4·2H2O material.

[0072] (3) The FePO4·2H2O material obtained in step (2) was placed in a muffle furnace and calcined at 650°C for 8 hours at a heating rate of 8°C / min to obtain anhydrous porous iron phosphate nanomaterial. The scanning electron microscope image of the porous iron phosphate nanomaterial is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 3 As shown, and by Figure 3 It can be seen that the peak positions of the porous nano-iron phosphate material obtained in this disclosure correspond to those of the standard iron phosphate card.

[0073] Example 2

[0074] This embodiment provides a method for preparing porous nano-iron phosphate materials, the preparation method comprising the following steps:

[0075] (1) Mix 0.02 mol of melamine, 0.02 mol of o-hydroxybenzoic acid, and 20 mL of deionized water with 0.001 mol of iron source or 0.001 mol of phosphorus source. After stirring for 15 min, heat the mixture at 70 °C and continue stirring for 30 min to obtain a solution containing Fe. 3+ Hydrogel solutions or containing PO4 3- Hydrogel solution;

[0076] 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;

[0077] Fe 3+ After adjusting the pH of the hydrogel solution to 1.8, it was added dropwise to 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 microemulsions;

[0078] Will contain PO4 3- The hydrogel solution was added dropwise to 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 a solution containing PO4. 3- Hydrogel microemulsions;

[0079] The organic phase solution comprises Triton X-100, n-hexanol, and n-heptane, and is obtained by dispersing 1.5 g Triton X-100, 0.08 g n-hexanol, and 80 mL n-heptane.

[0080] (2) The Fe-containing material described in step (1) 3+ The hydrogel microemulsion and the PO4-containing solution described in step (1) 3- The hydrogel microemulsion was mixed and stirred at room temperature for 30 min. Then it was transferred to a reflux reaction apparatus and heated. The reaction was carried out at 70 °C for 10 h. After the reaction was completed, it was aged for 4 h. Then the product was collected by centrifugation and washed several times with deionized water, acetone and anhydrous ethanol. Then it was dried in a vacuum oven at 100 °C for 12 h to obtain FePO4·2H2O material.

[0081] (3) The FePO4·2H2O material described in step (2) is 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.

[0082] Example 3

[0083] This embodiment provides a method for preparing porous nano-iron phosphate materials, the preparation method comprising the following steps:

[0084] (1) Mix 0.025 mol of dimethacrylamide, 0.025 mol of succinic acid, and 25 mL of water with 0.0025 mol of iron source or 0.0025 mol of phosphorus source. After stirring for 15 min, heat the mixture at 70 °C and continue stirring for 30 min to obtain a solution containing Fe. 3+ Hydrogel solutions or containing PO4 3- Hydrogel solution;

[0085] 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;

[0086] Fe 3+ After adjusting the pH of the hydrogel solution to 2, it was added dropwise to 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 microemulsions;

[0087] Will contain PO4 3-The hydrogel solution was added dropwise to 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 a solution containing PO4. 3- Hydrogel microemulsions;

[0088] The organic phase solution comprises Triton X-100, n-hexanol, and n-heptane, and is obtained by dispersing 2g Triton X-100, 0.08g n-hexanol, and 80mL n-heptane.

[0089] (2) The Fe-containing material described in step (1) 3+ The hydrogel microemulsion and the PO4-containing solution described in step (1) 3- The hydrogel microemulsion was mixed and stirred at room temperature for 30 min. Then it was transferred to a reflux reaction apparatus and heated. The reaction was carried out at 90℃ for 4 h. After the reaction was completed, it was aged for 4 h. Then the product was collected by centrifugation and washed several times with deionized water, acetone and anhydrous ethanol. Then it was placed in a vacuum oven at 100℃ for 12 h to obtain FePO4·2H2O material.

[0090] (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.

[0091] Example 4

[0092] This embodiment provides a method for preparing porous nano-iron phosphate materials. Except for the reaction temperature of step (2) being 60°C, the preparation method is the same as that in Example 1.

[0093] Example 5

[0094] This embodiment provides a method for preparing porous nano-iron phosphate material. Except for the reaction temperature of 100°C in step (2), the preparation method is the same as that in Example 1.

[0095] Example 6

[0096] This embodiment provides a method for preparing porous nano-iron phosphate materials. The method reduces the amount of iron and phosphorus sources added, thus simplifying the preparation step (1) which involves Fe-containing materials. 3+ In the hydrogel solution, the concentration of the iron source is 0.02 mol / L, and the PO4-containing solution... 3- In the hydrogel solution, the concentration of the phosphorus source was 0.02 mol / L, and everything else was the same as in Example 1.

[0097] Example 7

[0098] This embodiment provides a method for preparing porous nano-iron phosphate materials. The method, besides increasing the amount of iron and phosphorus sources added, makes the Fe-containing material in step (1) more effective. 3+ In the hydrogel solution, the concentration of the iron source is 0.2 mol / L, and the PO4-containing solution... 3- In the hydrogel solution, the concentration of the phosphorus source was 0.2 mol / L, and everything else was the same as in Example 1.

[0099] Example 8

[0100] This embodiment provides a method for preparing porous nano-iron phosphate materials. The method, besides increasing the amount of iron and phosphorus sources added, makes the Fe-containing material in step (1) more effective. 3+ In the hydrogel solution, the concentration of the iron source is 0.3 mol / L, and the PO4-containing solution... 3- In the hydrogel solution, the concentration of the phosphorus source was 0.3 mol / L, and everything else was the same as in Example 1.

[0101] Comparative Example 1

[0102] This comparative example provides a method for preparing iron phosphate material. The preparation method is the same as in Example 1 except that step (1) is not performed and step (2) directly uses an aqueous solution of iron source and an aqueous solution of phosphorus source for mixing and reaction.

[0103] The iron source aqueous solution described in this comparative example was obtained by dispersing 0.0013 mol of ferric chloride in 25 mL of deionized water and then sonicating for 15 min. The phosphorus source aqueous solution was obtained by dispersing 0.0013 mol of ammonium dihydrogen phosphate in 25 mL of deionized water and then sonicating for 15 min.

[0104] Comparative Example 2

[0105] This comparative example provides a method for preparing iron phosphate material, wherein the preparation method omits melamine and o-hydroxybenzoic acid in step (1), resulting in a material containing Fe. 3+ Reverse microemulsions and PO4-containing 3- Except for the reverse microemulsion, everything else is the same as in Example 1.

[0106] Lithium carbonate, iron source, and carbon source were dispersed in anhydrous ethanol according to a stoichiometric ratio of 1:1.04:0.12. The mixture was ball-milled for 3 hours at 3000 rpm until homogeneous, and then spray-dried to obtain precursor powder. The precursor powder was then heated to 400°C for 1.5 hours under a nitrogen atmosphere at a heating rate of 5°C / min, and then calcined at 700°C for 8 hours to obtain LiFePO4 / C cathode material. The obtained cathode material was then formulated into coin cells for lithium-ion battery electrochemical performance testing (with the charge / discharge voltage controlled between 2.5-4.5V).

[0107] The test results are shown in the table below:

[0108] Table 1

[0109]

[0110]

[0111] The following can be seen from Table 1:

[0112] This disclosure uses hydrogel microemulsions as templates to directly introduce Fe... 3+ Hydrogel microemulsions and PO4-containing 3- Direct mixing and reaction of hydrogel microemulsions can significantly improve the electrochemical performance of iron phosphate, resulting in a battery with excellent electrochemical performance; as shown in Example 1 and Comparative Examples 1-2, Comparative Example 1 directly uses Fe-containing... 3+ Aqueous solutions containing PO4 3- Solid, irregular iron phosphate blocks were prepared by reacting with an aqueous solution. In Comparative Example 2, solid spherical iron phosphate particles were prepared by reacting with a reverse microemulsion. Therefore, the electrochemical performance of the resulting battery was significantly reduced. As can be seen from Examples 1 and 4-8, the reaction temperature and the concentrations of iron and phosphorus sources will affect the reaction results, thereby affecting the battery performance.

[0113] In summary, this disclosure provides a porous nano-iron phosphate material, its preparation method, and its application. The preparation method is based on the spatial confinement effect of the hydrogel template, allowing iron phosphate nanoparticles to nucleate and grow within its network structure, effectively controlling the microstructure and size of the product. Furthermore, hydrogel vaporization can yield porous products, effectively improving the electrochemical performance of the iron phosphate material.

Claims

1. A method for preparing porous nano-iron phosphate material, comprising the following steps: (1) Mix and react an iron-containing hydrogel microemulsion with a phosphorus-containing hydrogel microemulsion to obtain an intermediate; (2) The intermediate in step (1) is calcined to obtain the porous nano-iron phosphate material; The method for preparing the iron-containing hydrogel microemulsion in step (1) includes: The iron-containing hydrogel solution is mixed with an organic phase solution to obtain the iron-containing hydrogel microemulsion. In the iron-containing hydrogel solution, the concentration of the iron source is 0.05-0.2 mol / L; The method for preparing the phosphorus-containing hydrogel microemulsion in step (1) includes: A phosphorus-containing hydrogel solution is mixed with an organic phase solution to obtain the phosphorus-containing hydrogel microemulsion. In the phosphorus-containing hydrogel solution, the concentration of the phosphorus source is 0.05-0.2 mol / L.

2. The preparation method according to claim 1, wherein, Before mixing the iron-containing hydrogel solution with the organic phase solution, the pH of the iron-containing hydrogel solution is adjusted.

3. The preparation method according to claim 2, wherein, The pH is adjusted to 1.8-2.

2.

4. The preparation method according to claim 1, wherein, The volumes of the iron-containing hydrogel solution and the phosphorus-containing hydrogel solution are each independently smaller than the volume of the organic phase solution.

5. The preparation method according to claim 1, wherein, The method for preparing the iron-containing hydrogel solution or the phosphorus-containing hydrogel solution includes: Amines, organic acids, and water are mixed with an iron source or a phosphorus source to obtain the hydrogel solution containing the iron source or the hydrogel solution containing the phosphorus source.

6. The preparation method according to claim 5, wherein, The amines include any one or a combination of at least two of melamine, dimethacrylamide, polyethylene glycol diamine, or polyethyleneimine.

7. The preparation method according to claim 5, wherein, The organic acid includes any one or a combination of at least two of o-hydroxybenzoic acid, maleic acid, succinic acid, or ethylene glycol dicarboxylic acid.

8. The preparation method according to claim 5, wherein, The amount of the amine added is 0.02-0.03 mol, and the amount of the organic acid added is 0.02-0.03 mol.

9. The preparation method according to claim 5, wherein, The volume of the water is 20-30 mL.

10. The preparation method according to claim 1, wherein, The organic phase solution includes surfactants, co-surfactants, and organic solvents.

11. The preparation method according to claim 1, wherein, The method for preparing the organic phase solution includes mixing a surfactant, a co-surfactant, and an organic solvent to obtain the organic phase solution.

12. The preparation method according to claim 10, wherein, The mass ratio of the surfactant to the co-surfactant is (20-25):

1.

13. The preparation method according to claim 10, wherein, The surfactant includes Triton X-100.

14. The preparation method according to claim 10, wherein, The co-surfactant includes n-hexanol.

15. The preparation method according to claim 10, wherein, The organic solvent includes n-heptane.

16. The preparation method according to claim 1, wherein, The reaction in step (1) is carried out at a temperature of 70-90℃ for 4-10 hours.

17. The preparation method according to claim 1, wherein, After the reaction described in step (1) was completed, aging, solid-liquid separation, washing and drying were also carried out.

18. The preparation method according to claim 17, wherein, The aging time is 3-5 hours.

19. The preparation method according to any one of claims 1-18, wherein, The calcination temperature in step (2) is 500-750℃ and the time is 4-10h.

20. The preparation method according to claim 1, wherein, The preparation method includes the following steps: (1) Mix 0.02-0.03 mol of amine, 0.02-0.03 mol of 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. 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. After adjusting the pH of the iron-containing hydrogel solution to 1.8-2.2, it was mixed with the organic phase solution to obtain an iron-containing hydrogel microemulsion. A phosphorus-containing hydrogel solution was mixed with an organic phase solution to obtain a phosphorus-containing hydrogel microemulsion. The organic phase solution includes surfactants, co-surfactants, and organic solvents; (2) The iron-containing hydrogel microemulsion described in step (1) is mixed with the phosphorus-containing hydrogel microemulsion described in step (1), and then reacted at 70-90℃ for 4-10h. After the reaction is completed, the mixture is aged for 3-5h, and then solid-liquid separation, washing and drying are performed to obtain the intermediate. (3) The intermediate in step (2) is calcined at 500-750°C for 4-10 hours to obtain the porous nano-iron phosphate material.

21. A porous nano-iron phosphate material prepared by the preparation method according to any one of claims 1-20.

22. A lithium iron phosphate material obtained by mixing and calcining a lithium source, a carbon source, and the porous nano-iron phosphate material as described in claim 21.

23. The lithium iron phosphate material according to claim 22, wherein, The molar ratio of the porous nano-iron phosphate material, lithium source, and carbon source is (1-1.1):1:(0.1-0.15).

24. The lithium iron phosphate material according to claim 22, wherein, The roasting temperature is 650-750℃, and the time is 6-10h.

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