Prussian blue sodium-ion battery cathode material, preparation method and use thereof
By using specific complexing agents and nonionic surfactants to prepare single-crystal Prussian blue materials, the problems of low specific capacity and poor kinetic performance of Prussian blue materials were solved, achieving high specific capacity, excellent Na+ diffusion kinetics and improved thermal stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-15
- Publication Date
- 2026-04-07
AI Technical Summary
Prussian blue materials prepared in the prior art suffer from problems such as low specific capacity, poor kinetic performance and low yield. This is mainly due to the excessively high concentration of conventional complexing agents, which leads to reduced particle size and uneven distribution, resulting in a polycrystalline structure.
By using specific complexing agents such as pyromellitic acid, methanetriacetic acid, or nitric acid, and adding nonionic surfactants, the concentration of the complexing agent in the precursor solution is controlled to near saturation. Large-particle-size, highly crystalline single-crystal Prussian blue materials are prepared through co-precipitation reaction, thereby improving sodium content and nucleation control to form a low-defect structure.
It improves the specific capacity and Na+ diffusion kinetics of Prussian blue material, enhances thermal stability and tap density, and improves the cycling stability and safety of the electrode.
Smart Images
Figure CN117566764B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of sodium ion batteries, in particular to a Prussian blue sodium ion battery positive electrode material and a preparation method and application thereof. BACKGROUND
[0002] With the rapid development of the electric vehicle, large-scale energy storage power station and smart grid industries, the demand for energy storage devices in the industry is increasing. Lithium ion batteries are the most commonly used energy storage devices, and their processes are mature and their energy storage performance is excellent, but their further development is limited by the shortage of lithium resources. Therefore, it is particularly important to develop a new electrochemical energy storage system. Among them, sodium ion batteries are very promising due to their similar performance and same working principle as lithium ion batteries.
[0003] The development of sodium ion batteries is often limited by positive electrode materials. The positive electrode materials that can be used in sodium ion batteries mainly include layered transition metal oxides, polyanion compounds and Prussian blue analogues. Among them, Prussian blue analogues have a three-dimensional open framework structure built by cyanide, which does not contain an oxygen lattice and has a weak interaction with Na + , so that the rapid reversible deintercalation of Na + can be achieved. When used as a positive electrode material for sodium ion batteries, the theoretical mass specific capacity of Prussian blue analogues is as high as 170 mAh / g, and the sodium storage potential is high and the cycle stability is good, so it is considered to be one of the most promising positive electrode materials for sodium ion batteries.
[0004] Prussian blue materials have polycrystalline structure and single crystal structure. Generally speaking, there are a large number of crystal boundaries on the surface and inside of the polycrystalline structure material, which will provide a channel for the penetration of the electrolyte when used as an electrode material, resulting in more serious side reactions between the electrode and the organic electrolyte. This not only slows down the ion diffusion kinetics inside the electrode, but also causes the active material of the electrode to powder and lose electrical contact. For Prussian blue materials, the polycrystalline structure also means that the structure of the material usually has a defect-rich and water-rich characteristic, which will cause the Na + migration energy to increase and thus affect the related electrochemical performance. At the same time, serious agglomeration occurs between the nanoparticles of the polycrystalline structure material, resulting in a too large cluster volume, so that the tap density of the nanocrystalline material is often not suitable for commercial applications. In contrast, single crystal structure materials can reduce the influence of the above aspects and exhibit better performance in terms of ion diffusion kinetics and cycle stability. In addition, due to higher thermal stability, tap density and volumetric energy density, single crystal structure positive electrode materials exhibit more reliable safety and competitiveness than polycrystalline positive electrode materials in practical applications.
[0005] Prussian blue materials are generally synthesized using a solvent co-precipitation method. This involves reacting transition metal salts, sodium ferrocyanide, and other raw materials in an aqueous solution and allowing the mixture to stand for a period of time before separating the resulting Prussian blue material from the aqueous solution. In related technologies, to increase the sodium content of Prussian blue materials, conventional complexing agents such as sodium citrate are typically added to high concentrations during the preparation process to create a sodium-rich environment, thereby improving the specific capacity of the battery.
[0006] However, in the process of realizing this invention, the inventors discovered that the Prussian blue materials prepared in related technologies still have a series of problems such as low specific capacity (caused by low sodium content and high water content), poor kinetic performance and low yield, which makes the resulting material formulation unsuitable for scale-up testing. Summary of the Invention
[0007] The inventors discovered that the Prussian blue materials prepared in related technologies suffer from a series of problems, such as low specific capacity (due to low sodium content and high water content), poor kinetic performance, and low yield. This is because when the concentration of complexing agents such as sodium citrate used in conventional applications is too high, it will cause the particle size of the Prussian blue materials generated in the reaction to decrease and become unevenly distributed, ultimately resulting in a polycrystalline structure of the prepared Prussian blue materials.
[0008] In view of this, the present invention provides a Prussian blue sodium-ion battery cathode material, its preparation method and application, to solve the problems of low specific capacity, poor kinetic performance and low yield of Prussian blue materials prepared in related technologies.
[0009] In a first aspect, the present invention provides a method for preparing a Prussian blue sodium-ion battery cathode material, comprising the following steps:
[0010] Sodium ferrocyanide, a complexing agent, and a nonionic surfactant are dissolved in deionized water to obtain a first precursor solution; wherein the complexing agent includes at least one of pyromellitic glycerol, methanetriacetic acid, and aminotriacetic acid.
[0011] The ferrous salt, complexing agent, and nonionic surfactant were dissolved in deionized water to obtain the second precursor solution.
[0012] Sodium salt and nonionic surfactant were dissolved in deionized water to obtain the third precursor solution;
[0013] The first and second precursor solutions were added dropwise to the third precursor solution under the action of a peristaltic pump to carry out a co-precipitation reaction and then aged to obtain the reaction product.
[0014] The reaction product is subjected to solid-liquid separation, and the solid is washed and dried.
[0015] In the above preparation method, when preparing Prussian blue sodium-ion battery cathode materials, specific complexing agents (pyromellitic acetic acid, methanetriacetic acid, or nitrilotriacetic acid) are selected, and nonionic surfactants are added. This guides the growth of Prussian blue materials and overcomes the problems of reduced particle size and uneven distribution caused by excessively high concentrations when using conventional complexing agents such as sodium citrate. The introduction of nonionic surfactants further increases the concentration of these specific complexing agents to near saturation. This provides an extremely sodium-rich environment and significantly enhances the complexing ability of the complexing agents, greatly inhibiting Fe... 2+ The release of [a substance] further decreases the reaction kinetics, making it more favorable for synthesizing products with large particle size and high crystallinity; at the same time, it increases the saturation of the complexing agent in the precursor solution, reducing the molar proportion of water molecules in the precursor solution, thereby reducing the activity of water molecules. This allows Na [to be synthesized] more efficiently during the synthesis process. + It can compete for and occupy more binding sites. Therefore, the above preparation method can not only increase the sodium content of the prepared Prussian blue-like materials, thereby increasing the specific capacity of the materials, but also control the nucleation and growth rate of the obtained Prussian blue-like materials, forming large-size single crystals. The low-defect structure of the single crystals is conducive to extremely low metal ion dissolution, excellent specific capacity, and excellent Na+ content. + Diffusion kinetics mitigated the rate and capacity decay caused by the long sodium ion diffusion path in polycrystalline structures. Meanwhile, the thermal stability and tap density of single-crystal materials were significantly improved compared to polycrystalline structures.
[0016] The chemical structural formulas of pyromellitic acid, methanetriacetic acid, and aminoacetic acid are shown below:
[0017]
[0018] In one optional embodiment, in the first precursor solution, the concentration of sodium ferrocyanide is 20–60 mmol / L, the concentration of the complexing agent is 200–300 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
[0019] In one optional embodiment, in the second precursor solution, the concentration of the ferrous salt is 40–80 mmol / L, the concentration of the complexing agent is 200–300 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
[0020] In one optional embodiment, the concentration of the sodium salt in the third precursor solution is 20–100 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
[0021] In one alternative embodiment, the nonionic surfactant comprises polyvinyl alcohol and / or polyvinylpyrrolidone;
[0022] And / or, the ferrous salt comprises ferrous sulfate and / or ferrous chloride;
[0023] And / or, the sodium salt includes at least one of sodium chloride, sodium sulfate, and sodium pyrophosphate.
[0024] In one optional embodiment, when the first precursor solution and the second precursor solution are dripped into the third precursor solution, the peristaltic pump has a peristaltic rate of 60 to 140 mL / min.
[0025] And / or, the coprecipitation reaction is carried out under stirring conditions, with a reaction temperature of 80-100°C, a stirring speed of 50-200 rpm, and a stirring time of 6-10 h;
[0026] And / or, the aging time is 10 to 60 hours;
[0027] And / or, the drying conditions include: a drying temperature of 100–140°C and a drying time of 12–96 h.
[0028] In one alternative embodiment, the preparation method is carried out in a protective gas atmosphere, the protective gas being selected from nitrogen and / or argon.
[0029] Secondly, the present invention provides a Prussian blue sodium-ion battery cathode material, which is prepared by the above-described preparation method.
[0030] Thirdly, the present invention provides the use of the above-mentioned Prussian blue sodium-ion battery cathode material in the preparation of sodium-ion batteries.
[0031] Fourthly, the present invention provides a sodium-ion battery comprising the aforementioned Prussian blue sodium-ion battery cathode material. Attached Figure Description
[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0033] Figure 1 The images show the XRD test results of the cathode materials prepared in Examples 1-3;
[0034] Figure 2 The image shows the SEM test results of the cathode material prepared in Example 1.
[0035] Figure 3 The image shows the SEM test results of the cathode material prepared in Comparative Example 1.
[0036] Figure 4 The image shows the SEM test results of the cathode material prepared in Comparative Example 2.
[0037] Figure 5 The image shows the SEM test results of the cathode material prepared in Comparative Example 3. Detailed Implementation
[0038] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0039] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0040] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.
[0041] Example 1
[0042] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0043] (1) Under nitrogen protection, sodium ferrocyanide, complexing agent (triacetic acid) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water and stirred to form the first precursor solution;
[0044] In the first precursor solution obtained, the concentration of sodium ferrocyanide was 40 mmol / L, the concentration of complexing agent (triacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0045] (2) Under nitrogen protection, ferrous salt (ferrous sulfate), complexing agent (triacetic acid) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water to form a second precursor solution;
[0046] In the obtained second precursor solution, the concentration of ferrous salt (ferrous sulfate) was 60 mmol / L, the concentration of complexing agent (triacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0047] (3) Under nitrogen protection, sodium salt (sodium chloride) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water in a reactor to form a third precursor solution;
[0048] In the obtained third precursor solution, the concentration of sodium salt (sodium chloride) is 40 mmol / L and the concentration of nonionic surfactant (polyvinyl alcohol) is 10 g / L.
[0049] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0050] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0051] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0052] Example 2
[0053] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0054] (1) Under nitrogen protection, sodium ferrocyanide, complexing agent (methanetriacetic acid) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water and stirred to form the first precursor solution;
[0055] In the first precursor solution, the concentration of sodium ferrocyanide was 40 mmol / L, the concentration of complexing agent (methanetriacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0056] (2) Under nitrogen protection, ferrous salt (ferrous chloride), complexing agent (methanetriacetic acid) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water to form a second precursor solution;
[0057] In the obtained second precursor solution, the concentration of ferrous salt (ferrous chloride) was 60 mmol / L, the concentration of complexing agent (methanetriacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0058] (3) Under nitrogen protection, sodium salt (sodium sulfate) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water in a reactor to form a third precursor solution;
[0059] In the obtained third precursor solution, the concentration of sodium salt (sodium sulfate) was 40 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0060] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0061] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0062] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0063] Example 3
[0064] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0065] (1) Under nitrogen protection, sodium ferrocyanide, complexing agent (aminotriacetic acid) and nonionic surfactant (polyvinylpyrrolidone) are dissolved in deionized water and stirred to form the first precursor solution;
[0066] In the first precursor solution obtained, the concentration of sodium ferrocyanide was 40 mmol / L, the concentration of complexing agent (aminotriacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinylpyrrolidone) was 10 g / L.
[0067] (2) Under nitrogen protection, ferrous salt (ferrous sulfate), complexing agent (aminotriacetic acid) and nonionic surfactant (polyvinylpyrrolidone) are dissolved in deionized water to form a second precursor solution;
[0068] In the obtained second precursor solution, the concentration of ferrous salt (ferrous sulfate) was 60 mmol / L, the concentration of complexing agent (aminotriacetic acid) was 250 mmol / L, and the concentration of nonionic surfactant (polyvinylpyrrolidone) was 10 g / L.
[0069] (3) Under nitrogen protection, sodium salt (sodium pyrophosphate) and nonionic surfactant (polyvinylpyrrolidone) are dissolved in deionized water in a reactor to form a third precursor solution;
[0070] In the obtained third precursor solution, the concentration of sodium salt (sodium pyrophosphate) was 40 mmol / L, and the concentration of nonionic surfactant (polyvinylpyrrolidone) was 10 g / L.
[0071] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0072] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0073] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0074] Comparative Example 1
[0075] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0076] (1) Under nitrogen protection, sodium ferrocyanide, complexing agent (sodium citrate) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water and stirred to form the first precursor solution;
[0077] In the first precursor solution obtained, the concentration of sodium ferrocyanide is 40 mmol / L, the concentration of complexing agent (sodium citrate) is 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) is 10 g / L.
[0078] (2) Under nitrogen protection, ferrous salt (ferrous sulfate), complexing agent (sodium citrate) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water to form a second precursor solution;
[0079] In the obtained second precursor solution, the concentration of ferrous salt (ferrous sulfate) is 60 mmol / L, the concentration of complexing agent (sodium citrate) is 250 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) is 10 g / L.
[0080] (3) Under nitrogen protection, sodium salt (sodium chloride) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water in a reactor to form a third precursor solution;
[0081] In the obtained third precursor solution, the concentration of sodium salt (sodium chloride) is 40 mmol / L and the concentration of nonionic surfactant (polyvinyl alcohol) is 10 g / L.
[0082] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0083] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0084] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0085] Comparative Example 2
[0086] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0087] (1) Under nitrogen protection, sodium ferrocyanide and complexing agent (triacetic acid) are dissolved in deionized water and stirred to form the first precursor solution;
[0088] In the first precursor solution, the concentration of sodium ferrocyanide was 40 mmol / L and the concentration of complexing agent (triacetic acid) was 150 mmol / L.
[0089] (2) Under nitrogen protection, ferrous salt (ferrous sulfate) and complexing agent (triacetic acid) are dissolved in deionized water to form a second precursor solution;
[0090] In the obtained second precursor solution, the concentration of ferrous salt (ferrous sulfate) was 60 mmol / L and the concentration of complexing agent (triacetic acid) was 150 mmol / L.
[0091] (3) Under nitrogen protection, sodium salt (sodium chloride) is dissolved in deionized water in a reactor to form a third precursor solution;
[0092] In the obtained third precursor solution, the concentration of sodium salt (sodium chloride) was 40 mmol / L;
[0093] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0094] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0095] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0096] Comparative Example 3
[0097] Prussian blue sodium-ion battery cathode material was prepared according to the following method:
[0098] (1) Under nitrogen protection, sodium ferrocyanide and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water and stirred to form the first precursor solution;
[0099] In the first precursor solution obtained, the concentration of sodium ferrocyanide was 40 mmol / L and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0100] (2) Under nitrogen protection, ferrous salt (ferrous sulfate) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water to form a second precursor solution;
[0101] In the obtained second precursor solution, the concentration of ferrous salt (ferrous sulfate) was 60 mmol / L, and the concentration of nonionic surfactant (polyvinyl alcohol) was 10 g / L.
[0102] (3) Under nitrogen protection, sodium salt (sodium chloride) and nonionic surfactant (polyvinyl alcohol) are dissolved in deionized water in a reactor to form a third precursor solution;
[0103] In the obtained third precursor solution, the concentration of sodium salt (sodium chloride) is 40 mmol / L and the concentration of nonionic surfactant (polyvinyl alcohol) is 10 g / L.
[0104] (4) Under nitrogen protection, the first and second precursor solutions were added dropwise to the third precursor solution in the reactor at a constant rate by a peristaltic pump (peristaltic rate of 100 mL / min) to carry out co-precipitation reaction. After the first and second precursor solutions were added, the temperature was kept constant at 90℃ and stirred at a stirring speed of 100 rpm for 8 hours.
[0105] (5) After the reaction is complete, the obtained material is left to stand at room temperature for 12 hours to obtain the reaction product;
[0106] (6) The reaction product obtained in step (5) is centrifuged, and the resulting solid is washed with deionized water and anhydrous ethanol. Then it is placed in a vacuum oven and dried at 120°C for 96 hours to obtain Prussian blue sodium ion battery cathode material.
[0107] Experimental Example 1
[0108] The cathode materials prepared in Examples 1-3 were subjected to XRD tests, and the test results are as follows: Figure 1 As shown. SEM tests were performed on the cathode materials prepared in Example 1 and Comparative Examples 1-3, respectively. The test results are shown below. Figures 2-5 As shown. Among them, Figure 1 The images show the XRD test results of the cathode materials prepared in Examples 1-3. Figure 2 The image shows the SEM test results of the cathode material prepared in Example 1. Figure 3 The image shows the SEM test results of the cathode material prepared in Comparative Example 1. Figure 4 The image shows the SEM test results of the cathode material prepared in Comparative Example 2. Figure 5 The image shows the SEM test results of the cathode material prepared in Comparative Example 3.
[0109] Depend on Figure 1 As can be seen from the XRD patterns of the cathode materials prepared in Examples 1-3, the product transforms from a cubic phase to a monoclinic phase as the complexing agent changes from nitrilotriacetic acid (Example 3) to methanetriacetic acid (Example 2) and then to pyromellitic triacetic acid (Example 1). Simultaneously, the product color changes from dark blue to white. In particular, the XRD pattern of Example 1 shows a peak splitting near 27°, indicating that the material undergoes lattice distortion due to the increased sodium content, thus exhibiting a monoclinic phase structure. According to literature reports, the above phenomena all indicate an increase in the sodium content of the product, meaning that changing the complexing agent contributes to increasing the initial sodium content of the product.
[0110] Depend on Figure 2 It can be seen that the Prussian blue material prepared in Example 1, using pyromellitic acetic acid as a complexing agent and polyvinyl alcohol as a nonionic surfactant, exhibits a more regular shape, displaying a single-crystal morphology with no fine grains adhering to the surface; Figure 3 It can be seen that the Prussian blue material particles prepared in Comparative Example 1, using sodium citrate as a complexing agent and polyvinyl alcohol as a nonionic surfactant, exhibit a multi-layered, stepped morphology on their surface, with particle sizes around 1 μm and varying sizes. Figure 4 It can be seen that the Prussian blue material prepared in Comparative Example 2, which uses pyromellitic acetic acid as a complexing agent and does not use a nonionic surfactant, forms a multi-layered, stepped morphology on its surface, with particle sizes around 3 μm and uneven size; Figure 5 It can be seen that the Prussian blue material prepared by Comparative Example 3, which does not use a complexing agent and uses polyvinyl alcohol as a nonionic surfactant, has fine grains and severe agglomeration. This is because the reaction kinetics of the Prussian blue preparation process are relatively fast, usually generating nanoscale grains.
[0111] Experiment Example 2
[0112] Sodium-ion half-cells were prepared using the positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-3, respectively, according to the following method:
[0113] The sodium-ion half-cell was a CR2025 coin cell. Before the experiment, the positive electrode active material needed to be dried in a vacuum environment (10⁻⁵ Pa) at 120℃ for 10 hours. The positive electrode slurry consisted of active material, conductive agent (KB), and binder (PVDF) in a weight ratio of 7:2:1. After adding an appropriate amount of NMP, it was stirred using a high-speed vibrating homogenizer and then coated onto a 15μm carbon-coated aluminum foil. The resulting coated electrode was dried in a vacuum oven at 120℃ for 24 hours, and then cut into round pieces for later use. During battery assembly, in a glove box under Ar atmosphere protection, the assembly was performed following the sequence: positive electrode shell - positive electrode sheet - glass fiber separator - negative electrode sheet / sodium metal sheet - current collector - spring sheet - negative electrode shell, with an appropriate amount of electrolyte added. The resulting coin cell was left to stand for 24 hours before electrochemical testing.
[0114] The initial discharge specific capacity and capacity retention rate after 25, 50, 100, and 200 cycles of each sodium-ion battery prepared above were tested. The test conditions were as follows: constant current charge and discharge tests were performed using a battery testing system. The prepared button batteries were placed on the test channel after being left to stand for 24 hours. The steps were set by software. The constant current charge and discharge steps were: stand, constant current charging (100mA / g, 4V), stand, constant current discharging (100mA / g, 2V), cycle, and end. The stand time was entered in the stand step, the cutoff voltage and current density were entered in the constant current charging and discharging steps, and the cycle start step and cycle number were entered in the cycle step.
[0115] The test results are shown in Table 1.
[0116] Table 1. Capacity and cycle performance test results of various sodium-ion batteries
[0117]
[0118] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing a Prussian blue sodium-ion battery cathode material, characterized in that, Includes the following steps: Sodium ferrocyanide, a complexing agent, and a nonionic surfactant are dissolved in deionized water to obtain a first precursor solution; wherein the complexing agent is pyromellitic acid. The ferrous salt, complexing agent, and nonionic surfactant were dissolved in deionized water to obtain the second precursor solution. Sodium salt and nonionic surfactant were dissolved in deionized water to obtain the third precursor solution; The first and second precursor solutions were added dropwise to the third precursor solution under the action of a peristaltic pump to carry out a co-precipitation reaction and then aged to obtain the reaction product. The reaction product is subjected to solid-liquid separation, and the solid is washed and dried.
2. The preparation method according to claim 1, characterized in that, In the first precursor solution, the concentration of sodium ferrocyanide is 20–60 mmol / L, the concentration of the complexing agent is 200–300 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
3. The preparation method according to claim 1, characterized in that, In the second precursor solution, the concentration of the ferrous salt is 40–80 mmol / L, the concentration of the complexing agent is 200–300 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
4. The preparation method according to claim 1, characterized in that, In the third precursor solution, the concentration of the sodium salt is 20–100 mmol / L, and the concentration of the nonionic surfactant is 5–20 g / L.
5. The preparation method according to claim 1, characterized in that, The nonionic surfactant includes polyvinyl alcohol and / or polyvinylpyrrolidone; And / or, the ferrous salt comprises ferrous sulfate and / or ferrous chloride; And / or, the sodium salt includes at least one of sodium chloride, sodium sulfate, and sodium pyrophosphate.
6. The preparation method according to claim 1, characterized in that, When the first precursor solution and the second precursor solution are dripped into the third precursor solution, the peristaltic pump has a peristaltic rate of 60-140 mL / min. And / or, the coprecipitation reaction is carried out under stirring conditions, with a reaction temperature of 80-100°C, a stirring speed of 50-200 rpm, and a stirring time of 6-10 h; And / or, the aging time is 10 to 60 hours; And / or, the drying conditions include: a drying temperature of 100–140°C and a drying time of 12–96 h.
7. The preparation method according to claim 1, characterized in that, The preparation method is carried out in a protective gas atmosphere, wherein the protective gas is selected from nitrogen and / or argon.
8. A Prussian blue sodium-ion battery cathode material, characterized in that, The Prussian blue sodium-ion battery cathode material is prepared using the preparation method described in any one of claims 1 to 7.
9. The use of the Prussian blue sodium-ion battery cathode material according to claim 8 in the preparation of sodium-ion batteries.
10. A sodium-ion battery, characterized in that, The sodium-ion battery includes the Prussian blue sodium-ion battery cathode material as described in claim 8.
Citation Information
Patent Citations
Prussian blue sodium ion battery positive electrode material and preparation method thereof
CN111943225A