Surface-loaded nanoparticle Prussian blue analogues, preparation methods and applications

Abstract

This application relates to a Prussian blue analogue with surface-loaded nanoparticles, a preparation method and an application, which includes: dissolving sodium ferrocyanide and a dispersant in a first solvent, adding an acid etchant after stirring, carrying out a hydrothermal reaction, and obtaining FeHCF powder after separation and drying; dissolving a copper ion source and a chelating agent in a second solvent, and mixing evenly to obtain solution A; dissolving the FeHCF powder, the dispersant and sodium ferrocyanide in a third solvent, and mixing evenly to obtain solution B; mixing solution A and solution B evenly to obtain a mixed solution, and obtaining a Prussian blue analogue with surface-loaded nanoparticles after aging, separation and drying. This application can effectively solve the problems of many defects in Prussian blue-based materials in the prior art, structural distortion of the materials during long-term cycling, and dissolution of the surface layer materials in the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and particularly relates to a Prussian blue analogue with surface-loaded nanoparticles, a preparation method and an application thereof. Background Art

[0002] In recent years, with the rapid development of new energy, power batteries and energy storage batteries have been greatly popularized and applied. Due to their excellent energy density and cycle life, lithium ion batteries are widely used in portable devices and electric vehicle fields.

[0003] However, due to the scarcity of lithium element, the high risk of lithium ion batteries, as well as the high cost and safety limitations, the development and application of lithium ion batteries are restricted. The crustal reserves of sodium element are much higher than those of lithium element. Sodium ion batteries have a similar working mechanism to lithium ion batteries, and sodium ion batteries have excellent safety. The low cost and high safety make sodium ion batteries become one of the most potential alternatives to lithium ion batteries.

[0004] However, the commercial application of sodium ion batteries is still restricted by many factors, especially the cathode materials. The cathode materials of sodium ion batteries can be divided into three categories: transition metal layered oxides, polyanion compounds, and Prussian blue compounds. Transition metal layered oxides have a high specific capacity, but poor air stability, and most of the synthesis processes require high-temperature sintering, which increases the production cost of the materials. Polyanion compounds represented by sodium vanadium phosphate have high stability and cycle performance, but due to the inherent properties of the materials themselves, their energy density is low and the conductivity is poor. In addition, the prices of elements such as vanadium are high and toxic, which hinders the low-cost and high-safety industrial development of polyanion compounds. Prussian blue analogues are considered to be promising cathode materials for sodium ion batteries because of their advantages such as high theoretical specific capacity and low cost, and their framework structure can enable sodium ions to quickly deintercalate / insert, thus showing excellent structural stability and rate performance.

[0005] The mainstream preparation method of Prussian blue materials is the chemical co-precipitation method, which has advantages such as low cost and simple process. However, Prussian blue materials prepared by the chemical co-precipitation method generally contain a large number of defects in the crystal lattice, such as vacancies and crystal water, due to rapid crystallization. These defects seriously affect the conductivity, sodium ion diffusion rate and structural stability of the materials. During long cycling, due to the repeated deintercalation and intercalation of sodium ions during charge and discharge, the stress generated will cause irreversible distortion of the material structure, and at the same time, the surface layer material may also dissolve to a certain extent in the electrolyte, thus affecting the capacity and cycle performance of sodium ion batteries. These disadvantages seriously limit the practical application of Prussian blue analogues in sodium ion battery electrode materials. Summary of the Invention

[0006] The present application provides a Prussian blue analogue with surface-loaded nanoparticles, a preparation method and an application, which can effectively solve the problems of many defects in Prussian blue-based materials in the prior art, structural distortion of the materials during long cycles, and dissolution of the surface layer materials in the electrolyte.

[0007] In a first aspect, an embodiment of the present application provides a preparation method of a Prussian blue analogue with surface-loaded nanoparticles, which includes:

[0008] Dissolve sodium ferrocyanide and a dispersant in a first solvent, add an acid etchant after stirring, carry out a hydrothermal reaction, and obtain FeHCF powder after separation and drying;

[0009] Dissolve a copper ion source and a chelating agent in a second solvent, and mix evenly to obtain solution A;

[0010] Dissolve FeHCF powder, a dispersant and sodium ferrocyanide in a third solvent, and mix evenly to obtain solution B;

[0011] Mix solution A and solution B evenly to obtain a mixed solution, and obtain a Prussian blue analogue with surface-loaded nanoparticles after aging, separation and drying.

[0012] Combined with the first aspect, in one embodiment, the reaction temperature of the hydrothermal reaction is 60-100 °C, and the reaction time is 20-24 h;

[0013] And / or, the dispersant includes at least one of polyvinylpyrrolidone and carboxymethyl cellulose;

[0014] And / or, the acid etchant includes at least one of hydrochloric acid and citric acid;

[0015] And / or, the copper ion source includes at least one of copper chloride and copper sulfate;

[0016] And / or, the chelating agent includes at least one of sodium citrate, EDTA, and EDHA.

[0017] [[ID=3)]]Combined with the first aspect, in one embodiment, when preparing FeHCF powder, the molar ratio of sodium ferrocyanide to the acid etchant is 1:(5-7).

[0018] Combined with the first aspect, in one embodiment, when preparing FeHCF powder, the mass ratio of sodium ferrocyanide to the dispersant is 1:(0.5-2).

[0019] Combined with the first aspect, in one embodiment, the molar ratio of the copper ion source to the chelating agent is 1:(1-2).

[0020] In combination with the first aspect, in one embodiment, when preparing Solution B, the mass ratio of the FeHCF powder, the dispersant, and sodium ferrocyanide is 0.1:(0.5 - 1.5):(0.1 - 0.2).

[0021] In combination with the first aspect, in one embodiment, in the mixed solution, the molar ratio of the copper ion source to sodium ferrocyanide is (0.8 - 1.2):(0.8 - 1.2).

[0022] In the second aspect, the embodiments of the present application provide a Prussian blue analogue with surface - loaded nanoparticles, which is prepared by using the preparation method of the Prussian blue analogue with surface - loaded nanoparticles described in any one of the above.

[0023] In combination with the second aspect, in one embodiment, the edge length of the cubic crystal of the Prussian blue analogue is 1 - 3 μm.

[0024] In the third aspect, the embodiments of the present application provide an application of the Prussian blue analogue with surface - loaded nanoparticles described above in the preparation of a cathode material for a sodium - ion battery.

[0025] The beneficial effects brought by the technical solutions provided by the embodiments of the present application at least include:

[0026] In the present application, the Prussian blue analogue with surface - loaded nanoparticles is prepared in two steps by the single - iron - source method and the co - precipitation method. Through the single - iron - source method, sodium ferrocyanide undergoes self - decomposition under acidic heating conditions, and the generated free divalent iron ions react with the undecomposed sodium ferrocyanide to form FeHCF, that is, NaFe[Fe(CN)6]. The FeHCF prepared by the single - iron - source method has higher crystallinity and fewer defects. Then, the FeHCF powder, the dispersant, and sodium ferrocyanide are dissolved in a third solvent to obtain a uniformly mixed FeHCF suspension. The copper ion source and the chelating agent are dissolved in a solvent to obtain free +2 - valent copper ions. The copper ions react with sodium ferrocyanide to form CuHCF, that is, NaCu[Fe(CN)6] nanoparticles, which grow uniformly on the surface of the FeHCF cubic grains to obtain the Prussian blue analogue with surface - loaded nanoparticles, FeHCF / CuHCF.

[0027] By uniformly loading CuHCF nanoparticles on the surface of FeHCF, the CuHCF nanoparticles can provide more active sites, effectively reduce the specific capacity loss caused by the loading structure, relieve the structural distortion caused by the internal stress of the material during long - term cycling to a certain extent while increasing the capacity, inhibit the dissolution of the surface material in the electrolyte, and improve the capacity and cycle stability of the material.

[0028] Compared with the coated or core-shell structure, by using the preparation method of the present application, CuHCF nanoparticles are uniformly and dispersedly loaded on the surface of FeHCF instead of being densely wrapped on the surface of FeHCF, which can release internal stress to a greater extent and alleviate the structural expansion problem caused by battery charge and discharge cycles.

[0029] When the Prussian blue analogue with surface-loaded nanoparticles prepared by the preparation method of the present application is used as the cathode material of a sodium-ion battery, it has an ultra-high specific capacity and excellent cycle stability. It has an ultra-high specific capacity of more than 122.51 mAh / g at a current density of 20 mA / g, and a capacity retention rate as high as 91.52% after 800 cycles at a current density of 100 mA / g, and has excellent rate performance. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 XRD patterns of the Prussian blue analogues prepared in Example 1 and Comparative Example 1;

[0032] Figure 2 SEM images of the Prussian blue analogues prepared in Example 1 and Comparative Example 1;

[0033] Figure 3 EDS energy spectrum of the Prussian blue analogue prepared in Example 1;

[0034] Figure 4 EDS energy spectrum of the Prussian blue analogue prepared in Comparative Example 1;

[0035] Figure 5 Cycling performance graphs of the Prussian blue analogues prepared in Example 1 and Comparative Example 1 at a current density of 20 mA / g;

[0036] Figure 6 Cycling performance graphs of the Prussian blue analogues prepared in Example 1 and Comparative Example 1 at a current density of 100 mA / g;

[0037] Figure 7 Rate performance graphs of the Prussian blue analogues prepared in Example 1 and Comparative Example 1;

[0038] Figure 8 Sodium-ion battery impedance performance curves of the Prussian blue analogues prepared in Example 1 and Comparative Example 1. Detailed Description of the Embodiments

[0039] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0040] The present invention provides a method for preparing a surface-loaded nanoparticle Prussian blue analogue, which comprises the following steps:

[0041] 101: Sodium ferrocyanide and a dispersant are dissolved in a first solvent, stirred thoroughly, and then an acid etchant is added to carry out a hydrothermal reaction. After separation and drying, FeHCF powder is obtained. The FeHCF powder, dispersant, and sodium ferrocyanide are dissolved in a third solvent and mixed uniformly to obtain solution B.

[0042] 102: dissolving the copper ion source and the chelating agent in the second solvent and mixing them uniformly to obtain solution A;

[0043] 103: Evenly mix solution A and solution B to obtain a mixed solution, age the solution, separate the solution, and dry the solution to obtain a Prussian blue analog with surface-loaded nanoparticles. Solution A can be slowly added to solution B.

[0044] The present application is a two-step preparation of a Prussian blue analogue with surface-loaded nanoparticles by a single iron source method and a coprecipitation method. In step 101, sodium ferrocyanide is self-decomposed under acidic heating conditions by a single iron source method, and the free divalent iron ions produced react with undecomposed sodium ferrocyanide to generate FeHCF, i.e., NaFe[Fe(CN)6]. The FeHCF prepared by the single iron source method has higher crystallinity and fewer defects. The FeHCF powder, dispersant, and sodium ferrocyanide are then dissolved in a third solvent to obtain a uniformly mixed FeHCF suspension. In step 102, a copper ion source and a chelating agent are dissolved in a solvent to obtain free +2-valent copper ions. In step 103, copper ions react with sodium ferrocyanide to generate CuHCF, i.e., NaCu[Fe(CN)6] nanoparticles, which grow uniformly on the surface of FeHCF cubic grains to obtain a Prussian blue analogue FeHCF / CuHCF with surface-loaded nanoparticles.

[0045] By uniformly loading CuHCF nanoparticles on the surface of FeHCF, the CuHCF nanoparticles can provide more active sites, effectively reduce the specific capacity loss caused by the loading structure, relieve the structural distortion caused by the internal stress of the material during long cycling to a certain extent while increasing the capacity, inhibit the dissolution of the surface material in the electrolyte, and improve the capacity and cycle stability of the material.

[0046] Compared with the coating or core-shell structure, by the preparation method of the present application, the CuHCF nanoparticles are uniformly and dispersedly loaded on the surface of FeHCF instead of being densely coated on the surface of FeHCF, which can release the internal stress to a greater extent and relieve the structural expansion problem caused by the charge and discharge cycles of the battery.

[0047] It should be noted that there is no strict order between the above step 101 and step 102. That is to say, the above step 101 and step 102 can be implemented simultaneously, or solution A can be prepared first and then solution B, or solution B can be prepared first and then solution A.

[0048] It should be noted that the reaction temperature of the hydrothermal reaction is 60-100 °C, and the reaction time is 20-24 h.

[0049] Preferably, the reaction temperature of the hydrothermal reaction is 80 °C, and the reaction time is 22 h.

[0050] The dispersant plays a role in making the solution uniform, and there are various choices. For example, the dispersant includes at least one of polyvinylpyrrolidone and carboxymethyl cellulose.

[0051] The acid etchant plays a role in acid etching sodium ferrocyanide, breaking chemical bonds, and releasing Fe2+. There are various choices. For example, the acid etchant includes at least one of hydrochloric acid and citric acid.

[0052] The copper ion source plays a role in providing divalent copper ions, and there are various choices. For example, the copper ion source includes at least one of copper chloride and copper sulfate.

[0053] The chelating agent plays a role in chelating copper ions and reducing the precipitation reaction rate. There are various choices. For example, the chelating agent includes at least one of sodium citrate, EDTA, and EDHA.

[0054] The first solvent, the second solvent, and the third solvent can be selected as deionized water, propylene glycol, etc.

[0055] Preferably, in step 101, when preparing the FeHCF powder, the molar ratio of the sodium ferrocyanide to the acid etchant is 1:(5-7). Preferably, the molar ratio of the sodium ferrocyanide to the acid etchant is 1:6.

[0056] Preferably, in step 101, when preparing the FeHCF powder, the mass ratio of sodium ferrocyanide to the dispersant is 1:(0.5 - 2).

[0057] Preferably, in step 102, the molar ratio of the copper ion source to the chelating agent is 1:(1 - 2).

[0058] Preferably, in step 101, when preparing solution B, the mass ratio of the FeHCF powder, the dispersant and sodium ferrocyanide is 0.1:(0.5 - 1.5):(0.1 - 0.2).

[0059] Preferably, in step 103, in the mixed solution, the molar ratio of the copper ion source to sodium ferrocyanide is (0.8 - 1.2):(0.8 - 1.2). Preferably, the molar ratio of the copper ion source to sodium ferrocyanide is 1:1. Obviously, the sodium ferrocyanide here refers to the sodium ferrocyanide added when preparing solution B.

[0060] The embodiment of the present application also provides a Prussian blue analogue with surface - loaded nanoparticles, which is prepared by using any one of the preparation methods of the Prussian blue analogue with surface - loaded nanoparticles provided in the above embodiments. The Prussian blue analogue uses FeHCF as a carrier, and CuHCF nanoparticles grow on the surface of FeHCF.

[0061] Preferably, the edge length of the cubic crystal of the Prussian blue analogue is 1 - 3 μm.

[0062] The embodiment of the present application also provides an application of the Prussian blue analogue with surface - loaded nanoparticles in the preparation of a cathode material for a sodium - ion battery.

[0063] The following further elaborates the present application in combination with examples and comparative examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that after reading the content taught in the present application, those skilled in the art can make various changes or modifications to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0064] Example 1

[0065] This example provides a preparation method of a Prussian blue analogue with surface - loaded nanoparticles, which specifically includes the following steps:

[0066] S1. Dissolve 1.936 g of sodium ferrocyanide and 2 g of polyvinylpyrrolidone K30 in 500 mL of deionized water. After sufficient stirring, add 24 mmol of hydrochloric acid and react at 80 °C for 22 h. After washing, separation and drying, FeHCF powder is obtained;

[0067] S2. Dissolve 0.5 mmol of copper chloride and 0.5 mmol of sodium citrate in 40 mL of deionized water, and mix evenly to obtain solution A; take 0.1 g of the FeHCF powder obtained in step S1, 1 g of polyvinylpyrrolidone K30, and 0.2 g of sodium ferrocyanide, dissolve them in 60 mL of deionized water, and mix evenly to obtain solution B;

[0068] S3. Titrate solution A into solution B at a rate of 1 mL / min, mix evenly to obtain a mixed solution, age it for 24 h at room temperature, then wash, separate, and dry it at 90 °C to obtain the Prussian blue analogue FeHCF / CuHCF with nanoparticles loaded on its surface.

[0069] Example 2

[0070] This example provides a method for preparing a Prussian blue analogue with nanoparticles loaded on its surface, which specifically includes the following steps:

[0071] S1. Dissolve 1.936 g of sodium ferrocyanide and 3 g of polyvinylpyrrolidone K30 in 500 mL of deionized water, add 20 mmol of hydrochloric acid after sufficient stirring, react at 80 °C for 22 h, and obtain the FeHCF powder after washing, separating, and drying;

[0072] S2. Dissolve 0.5 mmol of copper chloride and 1 mmol of sodium citrate in 40 mL of deionized water, and mix evenly to obtain solution A; take 0.1 g of the FeHCF powder obtained in step S1, 0.5 g of polyvinylpyrrolidone K30, and 0.2 g of sodium ferrocyanide, dissolve them in 60 mL of deionized water, and mix evenly to obtain solution B;

[0073] S3. Titrate solution A into solution B at a rate of 1 mL / min, mix evenly to obtain a mixed solution, age it for 20 h at room temperature, then wash, separate, and dry it at 90 °C to obtain the Prussian blue analogue FeHCF / CuHCF with nanoparticles loaded on its surface.

[0074] Example 3

[0075] This example provides a method for preparing a Prussian blue analogue with nanoparticles loaded on its surface, which specifically includes the following steps:

[0076] S1. Dissolve 1.936 g of sodium ferrocyanide and 3.5 g of polyvinylpyrrolidone K30 in 500 mL of deionized water, add 28 mmol of hydrochloric acid after sufficient stirring, react at 80 °C for 22 h, and obtain the FeHCF powder after washing, separating, and drying;

[0077] S2. 0.3mmol copper chloride and 0.5mmol sodium citrate were dissolved in 40mL of deionized water and mixed to obtain solution A; 0.1g of FeHCF powder obtained in step S1, 0.8g of polyvinylpyrrolidone K30 and 0.15g of sodium ferrocyanide were dissolved in 60mL of deionized water and mixed to obtain solution B;

[0078] S3. Solution A was titrated into solution B at a rate of 1 mL / min, and the mixture was uniformly mixed to obtain a mixed solution. After aging at room temperature for 22 h, the solution was washed and separated, and dried at 90°C to obtain a Prussian blue analog FeHCF / CuHCF with surface-loaded nanoparticles.

[0079] Comparative Example 1

[0080] This comparative example provides a method for preparing a Prussian blue analog material FeHCF, which specifically comprises the following steps: dissolving 1.936 g of sodium ferrocyanide and 2 g of polyvinylpyrrolidone K30 in 500 mL of deionized water, adding 24 mmol of hydrochloric acid after sufficient stirring, reacting at 80°C for 22 hours, and obtaining the Prussian blue analog material FeHCF after washing, separation, and drying.

[0081] Figure 1 The XRD patterns of the FeHCF / CuHCF prepared in Example 1 and the FeHCF prepared in Comparative Example 1 show that both the FeHCF / CuHCF prepared in Example 1 and the FeHCF prepared in Comparative Example 1 have a cubic crystal structure with a space group of Fm-3m (225).

[0082] Figure 2 SEM images of FeHCF / CuHCF prepared in Example 1 and FeHCF prepared in Comparative Example 1, wherein (a) and (b) are morphology images of the FeHCF material prepared in Comparative Example 1, and (c) and (d) are morphology images of the FeHCF / CuHCF material prepared in Example 1; it can be seen from the figures that both FeHCF / CuHCF and FeHCF have cubic structures and good crystallinity, and the particle size is 1 μm to 3 μm; it can be seen from (c) and (d) that nanoparticles are uniformly grown on the surface of the FeHCF / CuHCF material cubes, and it can be seen from (a) and (b) that the surface of the FeHCF material is smooth.

[0083] Figure 3 This is the EDS spectrum of FeHCF / CuHCF prepared in Example 1. It can be seen from the figure that the material is composed of Na, Fe, C, N, and Cu elements.

[0084] Figure 4 This is the EDS spectrum of FeHCF prepared in Comparative Example 1. It can be seen from the figure that the material is composed of Na, Fe, C, and N elements.

[0085] Application Example

[0086] The Prussian blue analogue materials prepared in Example 1 and Comparative Example 1 were mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) in a mass ratio of 7:2:1, an appropriate amount of N-methylpyrrolidone was added, and after ultrasonic dispersion, a slurry was formed. The slurry was coated on aluminum foil and vacuum dried for 12 h, and then pressed into a pole piece. Using the prepared material as the positive electrode, a sodium sheet as the negative electrode, a glass fiber as the separator, and NaClO4 as the electrolyte, a button battery (CR2032) was assembled, and its electrochemical performance was tested using a Blue Power battery test system.

[0087] The constant current charge-discharge cycling performance diagrams of the materials prepared in Example 1 and Comparative Example 1 at a current density of 20 mA / g are as Figure 5 shown, and the cycling performance diagrams at a current density of 100 mA / g are as Figure 6 shown.

[0088] From Figure 5 and Figure 6 it can be seen that the FeHCF / CuHCF electrode material prepared in Example 1 has an initial discharge specific capacity of 122.51 mAh / g at a current density of 20 mA / g and a capacity retention rate as high as 91.52% after 800 cycles at a current density of 100 mA / g; the FeHCF electrode material prepared in Comparative Example 1 has an initial discharge specific capacity of only 86.22 mAh / g at a current density of 20 mA / g and a capacity retention rate of 81.62% after 800 cycles at a current density of 100 mA / g.

[0089] Figure 7 The rate performance diagrams of FeHCF / CuHCF prepared in Example 1 and FeHCF prepared in Comparative Example 1 are shown. It can be seen from the figure that the reversible capacity can reach 130 mAh / g at a current density of 20 mA / g, and there is still a reversible capacity of more than 105 mAh / g at a large current of 2 A / g, and when the current returns to a small current, the capacity is not lost; it shows that the material prepared in this application has excellent rate performance.

[0090] To explore the electrochemical performance of the material, the transfer kinetics of Na + during the charge-discharge process was measured by electrochemical impedance spectroscopy (EIS) in the range of 0.1 HZ to 100 KHZ.

[0091] Figure 8The Nyquist plot obtained by fitting shows that the impedance spectra of Example 1 and Comparative Example 1 have similar shapes. The curve consists of a semicircle and a straight line. In the equivalent circuit diagram, Rs represents the ohmic impedance from the electrolyte, which is usually related to the intersection of the starting point and the horizontal axis in the high-frequency region; Rct represents the charge transfer resistance at the electrode / electrolyte interface, which is a semicircle in the high-frequency range; W represents the Warburg diffusion impedance of ions, which is an inclined line in the low-frequency region; the combination of Rct and W is called the Faraday impedance. It can be seen from the figure that the semicircle of Example 1 is smaller than that of Comparative Example 1, which proves that the material of Example 1 has a faster charge transfer rate.

[0092] From the above test results, it can be seen that when the Prussian blue analogue FeHCF / CuHCF with surface-loaded nanoparticles prepared in this application is used as the positive electrode material of a sodium-ion battery, it has a high initial capacity and exhibits very strong cycle stability.

[0093] In the description of this application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application. Unless otherwise clearly specified and defined, the terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0094] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0095] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of a Prussian blue analogue with surface-loaded nanoparticles, characterized in that, It includes: Dissolve sodium ferrocyanide and a dispersant in a first solvent, add an acid etchant after stirring, conduct a hydrothermal reaction, and obtain FeHCF powder after separation and drying. The dispersant includes at least one of polyvinylpyrrolidone and carboxymethyl cellulose, and the acid etchant includes at least one of hydrochloric acid and citric acid; Dissolve a copper ion source and a chelating agent in a second solvent, mix evenly to obtain solution A. The chelating agent includes at least one of sodium citrate, EDTA, and EDHA; Dissolve FeHCF powder, a dispersant, and sodium ferrocyanide in a third solvent, mix evenly to obtain solution B; Mix solution A and solution B evenly to obtain a mixed solution, and obtain a Prussian blue analogue with surface-loaded nanoparticles after aging, separation, and drying.

2. The preparation method of the Prussian blue analogue with surface-loaded nanoparticles according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction is 60 - 100 °C, and the reaction time is 20 - 24 h; And / or, the copper ion source includes at least one of copper chloride and copper sulfate.

3. The preparation method of the surface-loaded nanoparticle Prussian blue analogue according to claim 1, characterized in that: When preparing FeHCF powder, the molar ratio of sodium ferrocyanide to the acid etchant is 1:(5 - 7).

4. The preparation method of the surface-loaded nanoparticle Prussian blue analogue according to claim 1, characterized in that: When preparing FeHCF powder, the mass ratio of sodium ferrocyanide to the dispersant is 1:(0.5 - 2).

5. The preparation method of the surface-loaded nanoparticle Prussian blue analogue according to claim 1, characterized in that: The molar ratio of the copper ion source to the chelating agent is 1:(1 - 2).

6. The preparation method of the surface-loaded nanoparticle Prussian blue analogue according to claim 1, characterized in that: When preparing solution B, the mass ratio of FeHCF powder, the dispersant, and sodium ferrocyanide is 0.1:(0.5 - 1.5):(0.1 - 0.2).

7. The preparation method of the surface-loaded nanoparticle Prussian blue analogue according to claim 1, characterized in that: In the mixed solution, the molar ratio of the copper ion source to sodium ferrocyanide is (0.8 - 1.2):(0.8 - 1.2).

8. A Prussian blue analogue with surface-loaded nanoparticles, characterized in that: It is prepared by using the preparation method of the Prussian blue analogue with surface-loaded nanoparticles according to any one of claims 1 to 7.

9. The Prussian blue analogue with surface-loaded nanoparticles according to claim 8, characterized in that: The edge length of the cubic crystal of the Prussian blue analogue is 1 - 3 μm.

10. Application of the Prussian blue analogue with surface-loaded nanoparticles according to claim 8 or 9 in the preparation of a cathode material for a sodium-ion battery.

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