Method for coating prussian blue analogue with PEDOT (poly (3, 4-ethylenedioxythiophene)) and application

Abstract

The invention relates to a method for coating a prussian blue analogue with PEDOT (poly (3, 4-ethylenedioxythiophene)) and application, and belongs to the field of sodium ion batteries. The method comprises the following steps: adding a Prussian blue analogue and a commercial PEDOT: PSS dispersion liquid into a dispersion system, and uniformly stirring; and slowly adding the precipitation solution into the dispersion system, so that the PEDOT is separated out on the surface of the Prussian blue analogue. A high-molecular polymer in a commercial PEDOT: PSS dispersion liquid is slowly precipitated on the surface of the Prussian blue analogue through a precipitation solution, so that PEDOT is uniformly distributed on the surface of the Prussian blue analogue to form a coating layer, conductive polymer PEDOT can be firmly attached to the surface of the Prussian blue analogue, and the conductivity is improved, so that the electrochemical performance is improved. The process is simple and convenient to operate, is very suitable for being used as a coating process of the Prussian blue analogue, and solves the problem that the Prussian blue analogue is difficult to coat.

Description

Technical Field

[0001] The invention belongs to the field of sodium ion batteries, and particularly relates to a method and application of PEDOT-coated Prussian blue analogs. Background Art

[0002] Nowadays, with the vigorous development of new energy and the extensive use of electronic devices, a low-cost battery is needed to meet the energy storage needs. Sodium-ion batteries can be used as the next-generation battery technology route due to their abundant resources and excellent electrochemical performance. The main cathode materials for sodium-ion batteries are transition metal oxides, polyanion compounds, and Prussian blue analogs. Among them, Prussian blue analogs have the advantages of low cost, high energy density, good environmental performance, excellent rate performance and low-temperature performance, and are expected to occupy a place in the future sodium-ion battery cathode material market. Therefore, exploring the performance of Prussian blue analogs has become a current research hotspot.

[0003] Prussian blue analogs have a three-dimensional open framework and are generally prepared by coprecipitation. However, due to the fast reaction rate, vacancy defects will be generated, thereby forming coordinated water. The coordinated water will hinder the diffusion of sodium ions during the charge and discharge process, resulting in a low specific capacity. Generally, a complexing agent is added during the reaction to reduce the reaction rate, and low-defect Prussian blue analogs can be prepared. However, to further improve the cycle performance, methods such as doping and coating are required.

[0004] After Prussian blue analogs are coated, the contact between the Prussian blue analogs and the electrolyte can be reduced, thereby reducing the dissolution of metal ions, thereby improving the rate performance and long cycle performance of the Prussian blue analogs. Other functional coating materials make the Prussian blue analogs less likely to absorb water, improve the air stability of the Prussian blue analogs, and facilitate the process processing of the Prussian blue analogs.

[0005] Since Prussian blue analogues decompose at high temperatures, they cannot be carbon-coated via a high-temperature solid-phase method. If physical coating is performed via a liquid-phase method, there is generally uneven coating, and many functional coating materials are generally difficult to chemically bond with Prussian blue analogues. During subsequent cleaning, homogenization and other treatments, the functional coating materials will fall off. Summary of the invention

[0006] The purpose of the present invention is to solve the problem that the coating layer of a Prussian blue analog is uneven and easy to fall off, and to provide a method and application of PEDOT coating a Prussian blue analog. The method comprises the following steps: uniformly mixing a PEDOT:PSS dispersion and a Prussian blue analog in a dispersed system, and then adding a precipitant to deposit PEDOT on the surface of the Prussian blue analog to form a PEDOT coating layer. Subsequent ethanol washing and homogenization will not destroy the composite coating layer.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A method for coating a Prussian blue analog with PEDOT, the method comprising:

[0009] (1) Prussian blue analogs and commercial PEDOT:PSS dispersion are added to the dispersion system and stirred evenly; the ratio of Prussian blue analogs to PEDOT:PSS dispersion is calculated according to the actual coating requirements, and a proper amount of solvent is added to allow the Prussian blue analogs to be dispersed.

[0010] (2) Slowly add the precipitate into the dispersion system to precipitate PEDOT on the surface of the Prussian blue analog.

[0011] Further, in step (1), the chemical formula of the Prussian blue analogue is: Na x M A [Fe(CN)6] y ·zH2O,M A It is a transition metal element, wherein 2>x>1.4, 1>y>0.7, 4>z>2 or z=0.

[0012] Furthermore, the M A Mn 2+ , Fe 2+ ,Co 2+ , Ni 2+ , Zn 2+ , V 3+ , VO 2+ , Cu 2+ ,Cr 3+ One or a combination of the following.

[0013] Furthermore, in step (1), the dispersion system is a solvent such as water, NMP, NMF, acetonitrile, etc.

[0014] Furthermore, in step (2), the precipitating solution is one of a salt solution, an acidic solution or an organic solvent.

[0015] Furthermore, the salt in the salt solution is Na2SO4 or MnCl2, the acidic solution is one of sulfuric acid, acetic acid, oxalic acid, lactic acid or citric acid, and the organic solvent is one of ethanol, NMP or acetonitrile, preferably ethanol.

[0016] Furthermore, in step (2), when the precipitating solution is a salt solution or an acidic solution, the solvent is one or more of water, ethanol, NMP, NMF or acetonitrile.

[0017] An application of the PEDOT-coated Prussian blue analogue prepared by the above method, wherein the PEDOT-coated Prussian blue analogue is used as a positive electrode material for a sodium ion battery.

[0018] The invention uses a precipitation liquid to slowly precipitate a high molecular polymer in a commercial PEDOT:PSS dispersion liquid on the surface of a Prussian blue analog, so that PEDOT is evenly distributed on the surface of the Prussian blue analog to form a coating layer, and the conductive polymer PEDOT can be firmly attached to the surface of the Prussian blue analog, and improve the conductive performance, thereby improving the electrochemical performance. The process is simple and convenient to operate, and is very suitable as a coating process for Prussian blue analogs, solving the problem of difficult coating of Prussian blue analogs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the SEM image of PEDOT@Prussian blue analog;

[0020] Figure 2 Graph showing the cycling performance of PEDOT@Prussian blue analogs. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the protection scope of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0022] Embodiment 1:

[0023] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) in 15 g of NMP and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0024] (2) During the stirring process, 120 g of acetic acid in NMP solution (mass fraction 40%) was slowly added into the dispersed system.

[0025] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h. The Prussian blue@PEDOT composite material was obtained and labeled as PB-1.

[0026] Embodiment 2:

[0027] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) in 15 g of NMP and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0028] (2) During the stirring process, 150 g of oxalic acid solution in NMP (mass fraction 1%) was slowly added into the dispersed system.

[0029] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h, and then collected to obtain a Prussian blue@PEDOT composite material, which was recorded as PB-2.

[0030] Embodiment 3:

[0031] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) in 15 g of water and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0032] (2) During the stirring process, 120 g of an aqueous solution of acetic acid (mass fraction 90%) was slowly added into the dispersed system.

[0033] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h, and then collected to obtain a Prussian blue@PEDOT composite material, which was recorded as PB-3.

[0034] Embodiment 4:

[0035] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) in 15 g of water and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A[Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0036] (2) During the stirring process, 150 ml of a citric acid ethanol-water mixed solution (1% by mass fraction of citric acid, 95% by volume fraction of ethanol) was slowly added into the dispersed system.

[0037] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h. The Prussian blue@PEDOT composite material was obtained and labeled as PB-4.

[0038] Embodiment 5:

[0039] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) in 15 g of water and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0040] (2) During the stirring process, 150 ml of acetonitrile was slowly added into the dispersion system.

[0041] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h, and then collected to obtain a Prussian blue@PEDOT composite material, which was recorded as PB-5.

[0042] Embodiment 6:

[0043] (1) Disperse 12 g of the finished product of the Prussian blue analogue and 0.6 g of MnCl2 in 100 g of water and stir for 30 min; the chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0044] (2) During the stirring process, 15 g of PEDOT:PSS dispersion (solid content 1-1.5%) was slowly added into the dispersion system.

[0045] (3) The lower precipitate was centrifuged, washed with ethanol, and dried under vacuum at 120°C for 12 h, and then collected to obtain a Prussian blue@PEDOT composite material, which was recorded as PB-6.

[0046] Comparative Example 1: The original Prussian blue analogue is used as a comparative example, denoted as PB-5. The chemical formula of the Prussian blue analogue is Na x M A [Fe(CN)6] y ·zH2O,M A Mn 2+ , where x=1.72, y=0.93, z=2.86.

[0047] Battery assembly: The Prussian blue material prepared in Examples 1-6 and Comparative Example 1 is mixed with Super P conductive carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1, and then N-methyl-2-pyrrolidone is added and mixed to form a positive electrode slurry. The prepared positive electrode slurry is applied on a clean aluminum foil, dried in a coating machine, rolled by an electric roller machine, and then cut into circular pole pieces with a diameter of 14 mm by a slicer to obtain a positive electrode sheet; the sodium sheet is placed in the center of the negative electrode shell of the button battery, 40 μL of electrolyte is dripped, and after the glass fiber diaphragm is placed, 40 μL of electrolyte is dripped, and then the positive electrode sheet, gasket, shrapnel and positive electrode shell are placed in turn, and then sealed with a sealing machine to prepare a button battery.

[0048] Test method: After the assembled button cell is left to stand for 12 hours, the cycle performance test is performed at a test temperature of 25°C, a voltage range of 2.0 to 3.8V, and a rate of 1.0C. The test results are as follows: Figure 2 shown.

[0049]

[0050]

[0051] Conclusion: Compared with the control example 1, the six examples are all light blue powders with no color difference, indicating that the PEDOT distribution is relatively uniform; from the SEM images of the example 1 Figure 1 It can be observed that the surface of Prussian blue is relatively rough and has a small amount of film-like substances, which shows that PEDOT can form a coating layer on the surface of Prussian blue. And in the cycle performance diagram, it can be seen that the electrical cycle performance of Prussian blue is significantly improved after PEDOT coating, indicating that the present invention deposits a uniform PEDOT conductive coating layer on the surface of Prussian blue through the PEDOT:PSS dispersion, which significantly improves the cycle performance of Prussian blue.

Claims

1. A method for coating a Prussian blue analog with PEDOT, characterized in that: The method is: (1) Prussian blue analogs and commercial PEDOT:PSS dispersion are added to the dispersion system and stirred evenly; (2) Slowly add the precipitate into the dispersion system to precipitate PEDOT on the surface of the Prussian blue analog.

2. The method for coating a Prussian blue analog with PEDOT according to claim 1, characterized in that: In step (1), the chemical formula of the Prussian blue analogue is: Na x M A [Fe(CN)6] y ·zH2O,M A It is a transition metal element, wherein 2>x>1.4, 1>y>0.7, 4>z>2 or z=0.

3. The method for coating a Prussian blue analog with PEDOT according to claim 2, characterized in that: The M A Mn 2+ , Fe 2+ ,Co 2+ , Ni 2+ , Zn 2+ , V 3+ , VO 2+ , Cu 2+ ,Cr 3+ One or a combination of the following.

4. The method for coating a Prussian blue analog with PEDOT according to claim 1, characterized in that: In step (1), the dispersion system is a solvent such as water, NMP, NMF, acetonitrile, etc.

5. The method for coating a Prussian blue analog with PEDOT according to claim 1, characterized in that: In step (2), the precipitating solution is one of a salt solution, an acidic solution or an organic solvent.

6. The method for coating a Prussian blue analog with PEDOT according to claim 5, characterized in that: The salt in the salt solution is Na2SO4 or MnCl2, the acidic solution is one of sulfuric acid, acetic acid, oxalic acid, lactic acid or citric acid, and the organic solvent is one of ethanol, NMP or acetonitrile.

7. The method for coating a Prussian blue analog with PEDOT according to claim 5, characterized in that: In step (2), when the precipitating solution is a salt solution or an acidic solution, the solvent is one or more of water, ethanol, NMP, NMF or acetonitrile.

8. An application of a PEDOT-coated Prussian blue analogue prepared by the method according to any one of claims 1 to 7, characterized in that: The PEDOT-coated Prussian blue analogue is used as a cathode material for sodium-ion batteries.

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