Induced preparation method of positive electrode material of Prussian blue potassium ion battery

Abstract

The invention provides an induced preparation method of a positive electrode material of a Prussian blue potassium ion battery. The method comprises the following steps: S1, dissolving cyanide salt in deionized water to form a solution A; s2, dissolving ferrite, a complexing agent and an acid-base regulator in deionized water to form a solution B, and adding a nucleation template to induce crystallization after the solution B is uniformly mixed; s3, under the protection of inert atmosphere, slowly adding the solution A obtained in the step S1 into the solution B obtained in the step S2, continuously stirring to react, and then carrying out preliminary centrifugation to obtain solid powder; and S4, putting the solid powder obtained in the step S3 into a graphite mold, and removing crystal water through Joule heating to obtain the Prussian blue positive electrode material. The complexing agent and the nucleation template are used for inducing slow and ordered crystallization, crystal water is removed through rapid heating, crystal boundary slippage is avoided, the material stability is improved, the preparation method is simple, convenient and efficient, the yield is high, and the reaction is easy to control.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to an induced preparation method of Prussian blue potassium-ion battery cathode material and its application in potassium-ion batteries. Background Technology

[0002] Potassium-ion batteries, with their abundant resources and low cost, demonstrate enormous application potential. Potassium reserves in the Earth's crust far exceed those of lithium, and their widespread distribution reduces dependence on scarce resources. Furthermore, potassium-ion batteries exhibit performance similar to lithium-ion batteries in terms of operating voltage and energy density, with some systems even compatible with lithium-ion battery manufacturing processes, facilitating industrialization. Therefore, potassium-ion batteries are expected to become an important technological path to alleviate lithium resource shortages and promote the diversification of energy storage technologies.

[0003] Prussian blue analogues, as cathode materials for potassium-ion batteries, have become a candidate due to their simple synthesis, low cost, open framework, tunable atomic arrangement, and low operating cost. Their three-dimensional ion channels can accommodate the insertion and extraction of larger potassium ions, providing an ideal platform for high-capacity potassium storage. High-energy ball milling of Prussian blue analogues is simple and yield-efficient, but requires prolonged high-energy input and the materials are prone to agglomeration, forming micron-sized particles, which is detrimental to electrochemical performance. Hydrothermal methods can promote material dispersion and avoid agglomeration, but require sophisticated production equipment and are not environmentally friendly. Co-precipitation methods, with uniform distribution of metal ions and cyanide ions and high product homogeneity, are widely used preparation techniques.

[0004] However, traditional coprecipitation synthesis methods still suffer from problems such as lattice defects and high water of crystallization content, leading to rapid capacity decay. This is mainly because rapid nucleation reactions cause local supersaturation, forming ferricyanide vacancies that hinder potassium ion transport; lattice water occupies potassium ion sites, reducing effective capacity and triggering side reactions during cycling. Therefore, optimizing coprecipitation technology to achieve precise defect control and low-temperature, efficient dehydration is essential for promoting the large-scale application of highly stable Prussian blue cathode materials. Summary of the Invention

[0005] To address the problems existing in the background technology, this invention provides an induced preparation method and application of Prussian blue potassium-ion battery cathode material. The method utilizes a complexing agent and a nucleation template to induce slow and orderly crystallization, and removes the water of crystallization by rapid heating to avoid grain boundary slip, thereby improving the stability of the material. Moreover, the preparation method is simple, efficient, has a high yield, and the reaction is easy to control.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0007] In a first aspect, the present invention provides a method for the induced preparation of a Prussian blue potassium-ion battery cathode material, comprising the following steps:

[0008] S1. Dissolve the cyanide salt in deionized water to form solution A;

[0009] S2. Dissolve ferrous salt, complexing agent, and acid-base regulator in deionized water to form solution B. After solution B is mixed evenly, add nucleation template to induce crystallization.

[0010] S3. Under an inert atmosphere, the solution A obtained in step S1 is slowly added dropwise to the solution B obtained in step S2. After the reaction is completed by continuous stirring, a preliminary centrifugation is performed to obtain a solid powder.

[0011] S4. Place the solid powder obtained in step S3 into a graphite mold, and remove the water of crystallization by Joule heating to obtain Prussian blue cathode material.

[0012] According to the above scheme, the cyanide salt is one or a combination of potassium ferricyanide or sodium ferricyanide; the ferrous salt is one or a combination of ferrous chloride or ferrous sulfate; the complexing agent is one or a combination of ethylenediaminetetraacetic acid, polyvinylpyrrolidone, polyvinyl alcohol, and sodium dodecyl sulfate; the acid-base regulator is one or a combination of ascorbic acid, citric acid, oxalic acid, dilute hydrochloric acid, and dilute sulfuric acid; and the nucleation template is one or a combination of graphene, carbon nanotubes, and expanded graphite.

[0013] According to the above scheme, the molar ratio of cyanide to ferrous salt is 1:0.9 to 1.1.

[0014] According to the above scheme, the amount of complexing agent added is 3% to 10% of the total mass of cyanide and ferrous salt; the amount of acid-base regulator added is 0.5 to 1.5 g per 20 ml of deionized water; and the amount of nucleating template added is 1% to 5% of the total mass of cyanide and ferrous salt.

[0015] According to the above scheme, the stirring rate of the dissolution process and the continuous stirring process in steps S1, S2 and S3 is 500 to 1000 rpm, the reaction time is 12 to 24 h, and the dropping rate is 2 to 10 ml / min.

[0016] According to the above scheme, the inert atmosphere is either nitrogen or argon.

[0017] According to the above scheme, the centrifugation speed is 8000-12000 rpm and the centrifugation time is 1-5 min.

[0018] According to the above scheme, the Joule heating temperature in step S4 is 100-300℃, the heating time is 1-2s, the holding time is 3-10s, and the atmosphere is either nitrogen or argon.

[0019] Secondly, the present invention provides a Prussian blue potassium-ion battery cathode material, which is obtained by the above method.

[0020] Thirdly, the present invention provides the application of the above-mentioned Prussian blue potassium-ion battery cathode material in the preparation of potassium-ion cathode sheets, wherein the Prussian blue potassium-ion battery cathode material serves as the active material of the potassium-ion battery cathode sheet.

[0021] Specifically, Prussian blue cathode material is mixed evenly with Ketjen black and polyvinylidene fluoride, coated onto carbon-coated aluminum foil, and dried to form a potassium-ion battery cathode sheet. The mass ratio of Prussian blue cathode material, Ketjen black, and polyvinylidene fluoride is 7-8:1-2:1.

[0022] The principle of this invention is as follows:

[0023] Cyanide and ferrous ions undergo a coordination reaction in solution to generate Prussian blue cathode material. A pH adjuster is added to the ferrous salt solution to control the pH between 3 and 4, preventing the oxidation of ferrous iron to ferric iron. Simultaneously, a complexing agent is added, and after complete dissolution by stirring, it forms a stable complex with the ferrous ions, reducing the concentration of free ferrous ions, inducing a slow cyanide coordination reaction rate, and suppressing lattice defects caused by rapid reactions. The complexing agent's coordination ability also reduces the lattice water content. A uniformly dispersed nucleation template provides a large reaction substrate, inducing ordered crystallization of Prussian blue, improving crystallinity and reaction rate, and inhibiting particle agglomeration. Joule heating for rapid sintering further removes water of crystallization while avoiding prolonged high-temperature environments that could lead to crystal facet migration.

[0024] The beneficial effects of this invention are:

[0025] 1) This invention induces a slow and orderly coordination reaction through the combined action of complexing agents and nucleation templates. The strong complexing coordination ability can not only replace the water of crystallization in the crystal lattice and reduce the water content, but also reduce defects. The nucleation template increases the coordination reaction rate, thereby realizing the rapid preparation of highly crystalline Prussian blue cathode materials.

[0026] 2) By rapidly performing Joule heat treatment, the water of crystallization is removed at an instantaneous high temperature, thereby protecting the crystal structure and reducing the internal water content. Compared with traditional methods for removing water content at high temperatures, this method has a higher preparation efficiency.

[0027] 3) The complexing agent and nucleating template used in this invention have low cost, do not produce harmful substances during the preparation process, can be reused, and have good prospects for industrial application. Attached Figure Description

[0028] Figure 1 This is a SEM image of the Prussian blue potassium-ion battery cathode material of the present invention;

[0029] Figure 2 XPS image of the Prussian blue potassium ion battery cathode material of this invention;

[0030] Figure 3 This is a diagram showing the electrochemical performance of the Prussian blue potassium-ion battery cathode material of this invention. Detailed Implementation

[0031] The principles and features of the present invention are described below with reference to the accompanying drawings and specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0032] Prussian blue analogues are considered high-performance cathode materials for potassium-ion batteries due to their simple synthesis, low cost, open framework, tunable atomic arrangement, and low operating cost. Coprecipitation promotes uniform distribution of metal ions and cyanide ions, resulting in highly uniform products, and is a widely used preparation technique. However, traditional coprecipitation synthesis methods suffer from lattice defects and high water of crystallization content, leading to rapid capacity decay. The inventors optimized the coprecipitation technique by utilizing the synergistic effect of complexing agents and nucleation templates to achieve precise defect control and low-temperature, efficient dehydration, thus obtaining Prussian blue potassium-ion cathode materials.

[0033] This invention provides an induced preparation method for Prussian blue potassium-ion battery cathode material, comprising the following steps:

[0034] S1. Dissolve the cyanide salt in deionized water to form solution A;

[0035] S2. Dissolve ferrous salt, complexing agent, and acid-base regulator in deionized water to form solution B. After solution B is mixed evenly, add nucleation template to induce crystallization.

[0036] S3. Under an inert atmosphere, the solution A obtained in step S1 is slowly added dropwise to the solution B obtained in step S2. After the reaction is completed by continuous stirring, a preliminary centrifugation is performed to obtain a solid powder.

[0037] S4. Place the solid powder obtained in step S3 into a graphite mold, and remove the water of crystallization by Joule heating to obtain Prussian blue cathode material.

[0038] In some specific embodiments, solution A and solution B undergo a co-precipitation reaction under continuous stirring, and after Joule heating post-treatment, Prussian blue potassium ion battery cathode material is obtained.

[0039] Preferably, the cyanide salt is one or a combination of potassium ferricyanide or sodium ferricyanide; the ferrous salt is one or a combination of ferrous chloride or ferrous sulfate; the complexing agent is one or a combination of ethylenediaminetetraacetic acid, polyvinylpyrrolidone, polyvinyl alcohol, and sodium dodecyl sulfate; the acid-base regulator is one or a combination of ascorbic acid, citric acid, oxalic acid, dilute hydrochloric acid, and dilute sulfuric acid; and the nucleating template is one or a combination of graphene, carbon nanotubes, and expanded graphite.

[0040] Preferably, the molar ratio of the cyanide to the ferrous salt is 1:0.9 to 1.1.

[0041] Preferably, the amount of the complexing agent added is 3% to 10% of the total mass of cyanide and ferrous salt; the amount of the acid-base regulator added is 0.5 to 1.5 g per 20 ml of deionized water; and the amount of the nucleating template added is 1% to 5% of the total mass of cyanide and ferrous salt.

[0042] Preferably, the stirring rate of the dissolution process and the continuous stirring process in steps S1, S2 and S3 is 500 to 1000 rpm, the reaction time is 12 to 24 h, and the dropping rate is 2 to 10 ml / min.

[0043] Preferably, the inert atmosphere is either nitrogen or argon.

[0044] Preferably, the centrifugation speed is 8000-12000 rpm and the centrifugation time is 1-5 min.

[0045] Preferably, in step S4, the Joule heating temperature is 100–300°C, the heating time is 1–2 seconds, the holding time is 3–10 seconds, and the atmosphere is either nitrogen or argon.

[0046] The present invention also provides the Prussian blue potassium ion battery cathode material prepared as described above.

[0047] The aforementioned Prussian blue potassium-ion battery cathode material can be used as an active material in the preparation of potassium-ion battery cathode sheets.

[0048] Specifically, Prussian blue cathode material is mixed evenly with Ketjen black and polyvinylidene fluoride, coated onto carbon-coated aluminum foil, and dried to form a potassium-ion battery cathode sheet. The mass ratio of Prussian blue cathode material, Ketjen black, and polyvinylidene fluoride is 7-8:1-2:1.

[0049] The following are specific examples.

[0050] Example 1

[0051] This invention provides a method for inducing the preparation of Prussian blue potassium-ion battery cathode material, as follows:

[0052] 1) Dissolve 3.29g of potassium ferricyanide in 100ml of deionized water and accelerate the dissolution by stirring at 600rpm to form solution A;

[0053] 2) Dissolve 1.27g ferrous chloride, 0.25g ethylenediaminetetraacetic acid, and 4g ascorbic acid in 100ml deionized water and accelerate the dissolution by stirring at 600rpm to form solution B;

[0054] 3) After solution B is dissolved, add 0.14g of carbon nanotubes and stir continuously at a stirring rate of 600rpm to form a suspension;

[0055] 4) Under nitrogen protection, solution A was added dropwise to solution B at a rate of 6 ml / min to obtain a mixed solution, and the mixture was stirred continuously for 24 hours.

[0056] 5) Centrifuge the mixed solution at 10,000 rpm for 5 minutes to separate the solid powder;

[0057] 6) Place the solid powder in a graphite mold, heat it to 200°C in 1 second using a Joule thermometer under nitrogen protection, hold it at that temperature for 10 seconds, and then let it cool naturally to obtain the Prussian blue cathode material.

[0058] The Prussian blue potassium-ion battery cathode material prepared in Example 1 was characterized using scanning electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), and the results are as follows: Figure 1 and Figure 2 As shown.

[0059] Figure 1 The scanning electron microscope (SEM) image shows the morphology of the Prussian blue potassium-ion battery cathode material. Figure 1 It is evident that the overall morphology exhibits micron-sized flakes with smooth surfaces and regular shapes. This is attributed to the slow reaction rate induced by the complexing agent and the directional, ordered crystallization induced by the nucleation template. Furthermore, the larger particles contribute to increasing the material's tap density, thereby enhancing the overall energy density of the battery.

[0060] Figure 2 X-ray photoelectron spectroscopy (XPS) was used to analyze the chemical state of iron ions in the Prussian blue potassium-ion battery cathode material. The characteristic peaks at 724.7 eV and 711.1 eV correspond to the characteristic peaks of ferrous ions (Fe2+), and the two smaller peaks (marked in pink) correspond to the satellite peaks of ferric ions (Fe3+), proving the presence of two iron ions in the Prussian blue cathode material.

[0061] Application examples

[0062] The Prussian blue potassium-ion battery cathode material prepared in Example 1 was used as an active material to prepare the cathode of a potassium-ion battery. The specific preparation method was as follows: the active material, Ketjen black as a conductive agent, and polyvinylidene fluoride as a binder were mixed evenly and coated on aluminum foil. After drying, a cathode sheet was formed. The mass ratio of the active material, Ketjen black and polyvinylidene fluoride was 7-8:1-2:1.

[0063] The prepared positive electrode and pure potassium electrode sheet were assembled into a half-cell, and the electrochemical performance was tested. The results are as follows: Figure 3 As shown.

[0064] Figure 3 The figure shows the electrochemical cycling diagram of the Prussian blue cathode material. At a current density of 20 mA / g, the initial capacity of the Prussian blue cathode material is 128 mAh / g, and the capacity retention is 92.7% after 150 cycles and 88.9% after 300 cycles, demonstrating that the induced Prussian blue cathode material has good electrochemical capacity and cycling stability.

[0065] Example 2

[0066] 1) Dissolve 3.29g of potassium ferricyanide in 100ml of deionized water and accelerate the dissolution by stirring at 600rpm to form solution A;

[0067] 2) Dissolve 1.67g ferrous sulfate, 0.31g sodium dodecyl sulfate, and 3.5g citric acid in 100ml deionized water and accelerate the dissolution by stirring at 600rpm to form solution B;

[0068] 3) After solution B is dissolved, add 0.21g of graphene and stir continuously at a stirring rate of 600rpm to form a suspension;

[0069] 4) Under nitrogen protection, solution A was added dropwise to solution B at a rate of 6 ml / min to obtain a mixed solution, and the mixture was stirred continuously for 24 hours.

[0070] 5) Centrifuge the mixed solution at 10,000 rpm for 5 minutes to separate the solid powder;

[0071] 6) Place the solid powder in a graphite mold, heat it to 200°C in 1 second using a Joule thermometer under nitrogen protection, hold it at that temperature for 10 seconds, and then let it cool naturally to obtain the Prussian blue cathode material.

[0072] Example 3

[0073] 1) Dissolve 2.81g of sodium ferricyanide in 100ml of deionized water and accelerate the dissolution by stirring at 600rpm to form solution A;

[0074] 2) Dissolve 1.18g ferrous chloride, 0.38g polyvinyl alcohol, and 6.25g oxalic acid in 100ml deionized water and accelerate the dissolution by stirring at 600rpm to form solution B;

[0075] 3) After solution B is dissolved, add 0.18g of expanded graphite and stir continuously at a stirring rate of 600rpm to form a suspension;

[0076] 4) Under nitrogen protection, solution A was added dropwise to solution B at a rate of 6 ml / min to obtain a mixed solution, and the mixture was stirred continuously for 24 hours.

[0077] 5) Centrifuge the mixed solution at 10,000 rpm for 5 minutes to separate the solid powder;

[0078] 6) Place the solid powder in a graphite mold, heat it to 200°C in 1 second using a Joule thermometer under nitrogen protection, hold it at that temperature for 10 seconds, and then let it cool naturally to obtain the Prussian blue cathode material.

[0079] Both Examples 2 and 3 yielded Prussian blue potassium-ion battery cathode materials with excellent electrochemical performance.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the induced preparation of a Prussian blue potassium-ion battery cathode material, characterized in that, Includes the following steps: S1. Dissolve the cyanide salt in deionized water to form solution A; S2. Dissolve ferrous salt, complexing agent, and acid-base regulator in deionized water to form solution B. After solution B is mixed evenly, add nucleation template to induce crystallization. S3. Under an inert atmosphere, the solution A obtained in step S1 is slowly added dropwise to the solution B obtained in step S2. After the reaction is completed by continuous stirring, a preliminary centrifugation is performed to obtain a solid powder. S4. Place the solid powder obtained in step S3 into a graphite mold, and remove the water of crystallization by Joule heating to obtain Prussian blue cathode material.

2. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1, characterized in that, The cyanide salt is one or a combination of potassium ferricyanide or sodium ferricyanide; the ferrous salt is one or a combination of ferrous chloride or ferrous sulfate; the complexing agent is one or a combination of ethylenediaminetetraacetic acid, polyvinylpyrrolidone, polyvinyl alcohol, and sodium dodecyl sulfate; the acid-base regulator is one or a combination of ascorbic acid, citric acid, oxalic acid, dilute hydrochloric acid, and dilute sulfuric acid; and the nucleation template is one or a combination of graphene, carbon nanotubes, and expanded graphite.

3. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1 or 2, characterized in that, The molar ratio of the cyanide to the ferrous salt is 1:0.9 to 1.

1.

4. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1 or 2, characterized in that, The complexing agent is added at 3% to 10% of the total mass of cyanide and ferrous salt; the acid-base regulator is added at 0.5 to 1.5 g per 20 ml of deionized water; and the nucleating template is added at 1% to 5% of the total mass of cyanide and ferrous salt.

5. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1, characterized in that, The stirring rate for the dissolution process and the continuous stirring process described in steps S1, S2 and S3 is 500 to 1000 rpm, the reaction time is 12 to 24 h, and the dropping rate is 2 to 10 ml / min.

6. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1, characterized in that, The inert atmosphere is either nitrogen or argon.

7. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1, characterized in that, The centrifugation speed is 8000-12000 rpm, and the centrifugation time is 1-5 min.

8. The method for inducing the preparation of Prussian blue potassium-ion battery cathode material according to claim 1, characterized in that, In step S4, the Joule heating temperature is 100–300°C, the heating time is 1–2 seconds, the holding time is 3–10 seconds, and the atmosphere is either nitrogen or argon.

9. A Prussian blue potassium-ion battery cathode material, characterized in that, Obtained by the method described in any one of claims 1 to 8.

10. The application of the Prussian blue potassium-ion battery cathode material according to claim 9 in the preparation of potassium-ion cathode sheets, characterized in that, The Prussian blue potassium-ion battery cathode material is used as the active material of the potassium-ion battery cathode sheet.

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