A low-site manganese iron prussian blue analogue positive electrode material, a preparation method thereof and application thereof in preparation of a sodium ion battery

Abstract

This invention discloses a low-vacancy manganese iron Prussian blue analog cathode material, its preparation method, and its application in sodium-ion battery manufacturing, belonging to the field of sodium-ion battery technology. The method includes: adding sodium ferrocyanide and sodium citrate to deionized water to obtain solution A; adding manganese chloride and sodium citrate to deionized water to obtain solution B; adding solutions A and B to a sodium citrate solution, treating and repeatedly washing the precipitate, and drying to obtain a monoclinic manganese iron Prussian blue analog; adding this to a sodium ethylenediaminetetraacetate solution, and treating to obtain the low-vacancy manganese iron Prussian blue analog cathode material. This invention uses sodium ethylenediaminetetraacetate solution to modify PBAs, which, compared to acid-base etching modification used for Prussian blue analogs, does not produce highly toxic CN. ‑ It also does not produce insoluble hydroxide precipitates, while increasing the sodium content of PBAs, enhancing structural stability, and suppressing the content of lattice water.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a low-vacancy manganese iron Prussian blue analog cathode material, its preparation method, and its application in the preparation of sodium-ion batteries. Background Technology

[0002] Energy issues have always constrained the development of human society, and finite traditional fossil fuels such as natural gas, oil, and coal remain the primary driving force for human development. To alleviate the escalating energy crisis and the resulting environmental pollution, there is a growing call for the development and utilization of renewable and clean energy sources such as solar, tidal, and wind power. The key to solving these problems lies in how to store these intermittent and geographically limited clean energy sources on a large scale. Among energy storage systems (EESs) on the market, recyclable secondary batteries, with their superior energy conversion efficiency and environmental benefits, exhibit huge market demand. In particular, the successful commercialization of rechargeable lithium-ion batteries has enabled the widespread application of electric vehicles and portable digital products in people's daily lives. However, the large-scale demand for rechargeable lithium-ion batteries has also led to competition for lithium resources. Insufficient lithium supply inevitably leads to rising lithium prices, hindering the further development and application of lithium-ion batteries. Furthermore, due to the widespread distribution of sodium resources, sodium-ion batteries (SIBs) have become another research hotspot in the field of secondary batteries and are expected to replace lithium-ion batteries.

[0003] Although sodium and lithium belong to the same main group and have similar physical and chemical properties, Na+ is different from Li+. + Having a large ionic radius, sodium-ion batteries exhibit different intercalation behaviors in similar electrode materials, and may even slow down redox kinetics and worsen structural distortion, preventing the electrode material from exhibiting ideal electrochemical performance. This is one of the reasons why SIBs have been slow to achieve large-scale commercial application. This is especially true for sodium-ion battery cathode materials, where the Na+... + The migration process generates significant lattice distortion and severe capacity decay, which seriously hinders the commercialization of sodium-ion batteries. Among various sodium-ion battery cathode materials, Prussian blue analogues (PBAs) are considered highly promising due to their large guest ion channel structure, simple synthesis process, and high theoretical capacity. The general chemical formula of PBAs can be represented as A... x T1[T2(CN)6] y □ 1-y·nH2O, wherein 0<x<2; 0<y<1; A is an alkaline cation; T is a transition metal ion; □ is a vacancy occupied by coordinated water. However, the synthesis environment of PBAs is usually an aqueous solution, and PBAs prepared by conventional rapid precipitation method usually have a large number of vacancies. The existence of these vacancies provides space for coordinated water, which greatly reduces the efficiency and stability of PBAs during charging and discharging.

[0004] So far, many studies have been conducted to improve the electrochemical performance of PBAs. For example, the nucleation and crystal growth rate of PBAs are slowed down by introducing an appropriate amount of sodium citrate in the rapid precipitation method. Alternatively, a vacancy repair strategy is adopted, that is, adding a large amount of Na4Fe(CN)6·10H2O during or after the synthesis of PBAs to achieve the purpose of repairing vacancies and inhibiting coordinated water, and PBAs with high discharge capacity and low vacancies are obtained respectively. Despite these successes, most experiments are still based on low-salt solutions, which are not suitable for general large-scale industrial production.

[0005] Therefore, in order to improve the yield of PBAs, reduce production costs and reduce the generation of polluted water, it is necessary to further study and improve the synthesis of PBAs in high-salt solutions. SUMMARY OF THE INVENTION

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and briefly introduce preferred embodiments. Simplifications or omissions may be made in this section, the abstract of the specification and the title of the invention of the present application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] The present invention is proposed in view of the above-mentioned and / or the problems existing in the prior art.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of low-vacancy manganese-iron Prussian blue analogue cathode material.

[0009] In order to solve the above technical problems, the present invention provides the following technical solution: comprising,

[0010] sodium ferrocyanide and sodium citrate are added into deionized water at a molar ratio of 1.5 to 2.5:1 to obtain solution A;

[0011] manganese chloride and sodium citrate are added into deionized water at a molar ratio of 1.5 to 2.5:1 to obtain solution B;

[0012] solution A and solution B are added into 4~5×10 -4After stirring in a sodium citrate solution of mol / ml and allowing it to stand at room temperature for aging, the precipitate was filtered out. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and dried to obtain a monoclinic manganese iron Prussian blue analogue.

[0013] Monoclinic Prussian blue analogues were added to a sodium ethylenediaminetetraacetate solution, ultrasonically vibrated, and then allowed to stand at room temperature for aging before filtering out the precipitate. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and then dried to obtain a low-vacancy manganese iron Prussian blue analogue cathode material.

[0014] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the concentration of the sodium ethylenediaminetetraacetate solution is 1–5 × 10⁻⁶. -4 mol / ml.

[0015] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the stirring speed is 200-1200 r / min.

[0016] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the stirring time is 0.1 to 2 hours.

[0017] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the ultrasonic oscillation time is 0.1 to 0.6 h.

[0018] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the aging time is 1 to 60 hours.

[0019] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the drying temperature is 100-200°C.

[0020] In a preferred embodiment of the preparation method of the low-vacancy manganese iron Prussian blue analog cathode material of the present invention, the drying time is 12-48 hours.

[0021] Another objective of this invention is to overcome the shortcomings of the prior art and provide a low-vacancy manganese iron Prussian blue analog cathode material.

[0022] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a low-vacancy manganese iron Prussian blue analog cathode material in the preparation of sodium-ion batteries.

[0023] Beneficial effects of this invention:

[0024] This invention uses sodium oxalate tetraacetate solution to modify PBAs, which, compared to the acid-base etching modification used for Prussian blue analogues, does not produce highly toxic CN. - It also does not produce insoluble hydroxide precipitates, while increasing the sodium content of PBAs, enhancing structural stability, and suppressing the content of lattice water.

[0025] This invention obtains sodium-rich monoclinic PBA particles with numerous vacancy defects through a co-precipitation method assisted by a chelating agent. The obtained PBA particles with vacancy defects are then dispersed in a sodium ethylenediaminetetraacetate solution by ultrasonic vibration to repair the vacancy. This improves the sodium content in the PBA particles, enhances the structural stability of the PBA particles, and reduces the lattice water content. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0027] Figure 1 This is a scanning electron microscope image of the low-vacancy manganese-iron Prussian blue analog cathode material prepared in this embodiment.

[0028] Figure 2 The image shows the XRD pattern of the low-vacancy manganese-iron Prussian blue analog cathode material prepared in this embodiment.

[0029] Figure 3 This is the XPS full spectrum of the low-vacancy manganese-iron Prussian blue analog cathode material prepared in this embodiment. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0033] Unless otherwise specified, all raw materials used in this invention are commercially available in the field.

[0034] Example 1

[0035] This embodiment provides a method for preparing a low-vacancy manganese-iron Prussian blue analog cathode material, specifically as follows:

[0036] 1) Add 20 mmol of sodium ferrocyanide and 9 mmol of sodium citrate to 35 mL of deionized water and stir thoroughly to form solution A, wherein the molar ratio of sodium ferrocyanide to sodium citrate is 20:9.

[0037] 2) Add 20 mmol of manganese chloride and 9 mmol of sodium citrate to 35 mL of deionized water and stir thoroughly to form solution B, in which the molar ratio of manganese chloride to sodium citrate is 20:9.

[0038] 3) Add solutions A and B to 5×10 -4 After stirring in a sodium citrate solution at 25°C for 12 hours, the precipitate was filtered out. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and dried at 120°C to obtain a monoclinic manganese iron Prussian blue analogue.

[0039] 4) Add monoclinic Prussian blue analogue to 1×10 -4 After ultrasonic vibration in a sodium ethylenediaminetetraacetate solution, the precipitate was aged at 25°C for 12 hours and then filtered out. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and dried at 120°C to obtain a low-vacancy manganese iron Prussian blue analog cathode material.

[0040] Appendix Figure 1 The image shown is a scanning electron microscope image of the low-vacancy manganese iron Prussian blue analog cathode material prepared in this embodiment. It can be seen that the prepared material has reached the nanoscale and exhibits a typical Prussian blue cubic particle shape.

[0041] Appendix Figure 2 The XRD pattern of the low-vacancy manganese-iron Prussian blue analog cathode material prepared in this embodiment shows that the material has a monoclinic lattice structure, which reflects the rich sodium content of the material.

[0042] Appendix Figure 3 The XPS full spectrum of the low-vacancy manganese-iron Prussian blue analog cathode material prepared in this embodiment shows the presence of Na, Mn, Fe, C, N and O elements in the prepared material.

[0043] Example 2

[0044] The difference between this embodiment and Embodiment 1 is that the molar ratio of sodium ferrocyanide and sodium citrate in step 1) is adjusted to 10:6.

[0045] The remaining preparation methods are the same as in Example 1, resulting in the low-vacancy manganese iron Prussian blue analog cathode material of this example.

[0046] Example 3

[0047] The difference between this embodiment and Embodiment 1 is that the molar ratio of manganese chloride and sodium citrate in step 2) is adjusted to 10:6.

[0048] The remaining preparation methods are the same as in Example 1, resulting in the low-vacancy manganese iron Prussian blue analog cathode material of this example.

[0049] Example 4

[0050] This example is used to explore the effect of different sodium ethylenediaminetetraacetate solutions on the experimental results, specifically:

[0051] Adjust the concentration of the ethylenediaminetetraacetic acid solution in step 4) to 0.5, 2, and 3 × 10⁻⁶ respectively. -4 mol / ml;

[0052] The remaining preparation methods are the same as in Example 1, resulting in the low-vacancy manganese iron Prussian blue analog cathode material of this example.

[0053] Comparative Example 1

[0054] Comparative Example 1 is based on Example 1, except that Comparative Example 1 does not use sodium ethylenediaminetetraacetate solution;

[0055] The remaining steps are the same as in Example 1, resulting in the low-vacancy manganese iron Prussian blue analog cathode material of Comparative Example 1.

[0056] Application testing

[0057] Using the low-vacancy manganese-iron Prussian blue analog cathode material prepared in Examples 1-3 and Comparative Example 1 as the cathode, elemental sodium metal as the anode, glass fiber film (Whatman GF / D) as the battery separator, and a NaPF6 diethyl carbonate (DEC) / ethylene carbonate (EC) solution as the electrolyte, coin-type half-cells were assembled in an argon-filled glove box. The cells were then charged and discharged using an electrochemical workstation at a current density of 100 mA / g and a voltage range of 2.0-4.2 V. The electrochemical test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As can be seen from Table 1, the EDTA-treated samples in Example 1... 2- The repaired low-vacancy manganese iron Prussian blue analog cathode material exhibited the highest discharge capacity and the highest cycle stability.

[0061] The electrochemical performance of the low-vacancy manganese iron Prussian blue analog cathode material prepared in Example 4 was tested and compared with that in Example 1. The results are shown in Table 2.

[0062] Table 2

[0063]

[0064] It can be seen that with EDTA 2- With increasing EDTA concentration, the discharge capacity and cycle stability of the prepared samples showed an initial increase followed by a decrease. 2- Concentration reached 1×10 -4 At that time, the prepared samples showed good discharge capacity and cycle stability, which was due to the low concentration of EDTA. 2- The hydrolysis equilibrium of PBAs cannot be effectively regulated, while excessively high concentrations of EDTA... 2- This excessively affects the structure and elemental composition of PBA grains.

[0065] This invention innovatively utilizes the principle of weak hydrolysis of PBAs precipitated in water and uses EDTA, which has strong chelation properties with transition metal elements. 2- This invention aims to regulate the hydrolysis equilibrium of PBAs, thereby reducing PBA vacancies. Furthermore, compared to commonly used acid-base modified PBAs, EDTA... 2- Modified PBAs do not produce toxic CN like acid-modified PBAs. - It will not produce insoluble hydroxide precipitates like alkali modification.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a low-vacancy manganese-iron Prussian blue analog cathode material, characterized in that: include, Sodium ferrocyanide and sodium citrate were added to deionized water at a molar ratio of 1.5–2.5:1 to obtain solution A; Manganese chloride and sodium citrate were added to deionized water at a molar ratio of 1.5–2.5:1 to obtain solution B; Solution A and solution B were added to 4-5 × 10 -4 After stirring in a sodium citrate solution of mol / ml and allowing it to stand at room temperature for aging, the precipitate was filtered out. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and dried to obtain a monoclinic manganese iron Prussian blue analogue. Monoclinic Prussian blue analogues were added to a sodium ethylenediaminetetraacetate solution, ultrasonically vibrated, and then allowed to stand at room temperature for aging before filtering out the precipitate. The precipitate was washed multiple times with deionized water and anhydrous ethanol, and then dried to obtain a low-vacancy manganese iron Prussian blue analogue cathode material. The concentration of the sodium ethylenediaminetetraacetate solution is 1–5 × 10⁻⁶. -4 mol / ml.

2. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The stirring speed is 200–1200 r / min.

3. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The stirring time is 0.1 to 2 hours.

4. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The duration of the ultrasonic oscillation is 0.1 to 0.6 hours.

5. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The aging time is 1 to 60 hours.

6. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The drying temperature is 100–200°C.

7. The method for preparing the low-vacancy manganese-iron Prussian blue analog cathode material as described in claim 1, characterized in that: The drying time is 12 to 48 hours.

8. The low-vacancy manganese iron Prussian blue analog cathode material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the low-vacancy manganese iron Prussian blue analog cathode material as described in claim 8 in the preparation of sodium-ion batteries.

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