CN117497777A - Preparation method of a high-performance IL-MW-Mxene/CF composite electrode material and its application in vanadium batteries - Google Patents

Abstract

The invention particularly relates to a preparation method of a high-performance IL-MW-Mxene/CF composite electrode material and application of the high-performance IL-MW-Mxene/CF composite electrode material in a vanadium battery. First of all in high purity Ti ₃ AlC ₂ The MAX phase material is used as a precursor, and a mild ionic liquid-HCl mixed system is adopted to etch the material after the pretreatment of absolute ethyl alcohol; multilayer Ti by microwave assisted delamination technique ₃ C ₂ T _x Carrying out rapid stripping to obtain the ion-electron coupled two-dimensional lamellar IL-MW-MXene material, and adopting a physical adsorption method to carry out lamellar IL-MW-MXene is loaded on the surface of the carbon felt to obtain the IL-MW-MXene/CF composite material with high conductivity, high specific surface area and high catalytic activity. The cathode material is used as a cathode material of the vanadium battery, so that the cathode reaction dynamics of the vanadium battery can be effectively improved, and the battery efficiency and the cycling stability are improved. The method is simple and efficient, has low cost and has wide application prospect in the aspect of high-performance electrode materials.

Description

Preparation method of a high-performance IL-MW-Mxene/CF composite electrode material and its application in Applications in vanadium batteries

Technical field

The invention belongs to the technical field of battery materials and energy storage, and specifically relates to a preparation method of high-performance IL-MW-Mxene/CF composite electrode material and its application in vanadium batteries.

Background technique

With the increasing depletion of traditional fossil energy and the gradual intensification of environmental pollution, it is very urgent to develop clean and efficient renewable energy. Due to the instability and discontinuity of renewable energy sources such as wind energy and solar energy, large-scale energy storage technology is an effective way to stably output and efficiently utilize clean energy. As a promising large-scale energy storage device, vanadium batteries have the advantages of long cycle life, large energy storage capacity, flexible design, and green environmental protection, and have attracted keen attention from researchers.

Electrode materials are the place where electrochemical reactions occur and are the core materials for energy storage and conversion. They have a decisive impact on battery performance. Designing high-performance advanced electrode materials can effectively reduce battery polarization and improve battery operation stability and energy efficiency under high current density.

Polyacrylonitrile (PAN)-based porous carbon fiber felt is the most commonly used electrode material in vanadium batteries, with good mechanical properties, abundant pores, low cost and excellent chemical stability. However, its electrochemical reactivity is relatively poor, which severely limits the performance of vanadium batteries. The development of new electrode materials with excellent electrocatalytic activity can effectively improve the electrode reaction kinetics of vanadium batteries. Studies have shown that the negative electrode reaction process of vanadium batteries is more difficult to carry out than the positive electrode process, and its electrochemical reaction rate constant and the diffusion coefficient of active ions are significantly lower than the positive electrode reaction. Therefore, designing anode materials with excellent electrocatalytic activity for the anode reaction can further improve the performance of vanadium batteries.

Contents of the invention

In view of the above background and technical problems, the present invention provides a preparation method of high-performance IL-MW-Mxene/CF composite electrode material and its application in vanadium batteries.

The technical solution adopted by the present invention is:

A method for preparing high-performance IL-MW-Mxene/CF composite electrode material, including the following steps:

1) Pretreatment of Ti ₃ AlC ₂ MAX phase material: Soak Ti ₃ AlC ₂ MAX phase in absolute ethanol for 1 hour, ultrasonic for 30 minutes to remove excess impurities, wash and dry to obtain MAX phase powder;

2) Etch the pretreated MAX phase powder: use ionic liquid-hydrochloric acid as the etchant, the etching temperature is 30~60°C, and the etching time is 12~72h. After etching, the product is etched with deionized water and Wash with absolute ethanol until neutral, and then dry in vacuum to obtain a multi-layer Ti ₃ C ₂ T _x sample for later use;

3) Peel off and stratify the multi-layer Ti ₃ C ₂ T _x sample obtained after etching: disperse the multi-layer Ti ₃ C ₂ T _x sample in water, and use microwave-assisted delamination technology to separate the multi-layer Ti ₃ C ₂ T x sample into The _x sample was further layered, and the resulting product was cooled to room temperature, then centrifugally washed with deionized water and ethanol, and dried under vacuum to obtain IL-MW-MXene;

4) Preparation of IL-MW-MXene/CF composite electrode material: Soak the carbon-based porous electrode material in a Nafion aqueous solution containing IL-MW-MXene, then dry it at 50°C, and repeat the soaking and drying operations 1 to 3 times. , the IL-MW-MXene sheet material is uniformly bonded to the surface of the carbon fiber, and the IL-MW-MXene/CF composite electrode material is obtained.

Further, in the above preparation method, step 2), the ionic liquid-hydrochloric acid etchant is a mixed solution of 5 to 9 mol/LHCl and 1 to 10 wt% pyridine hexafluorophosphate ionic liquid or 5 to 9 mol/LHCl. A mixed solution of L HCl and imidazole in hexafluorophosphate ionic liquid.

Further, in step 3) of the above preparation method, the technical conditions for microwave-assisted layering are: microwave power is 750W, and processing time is 2 to 10 minutes.

Further, in step 4) of the above preparation method, the carbon-based porous electrode material is polyacrylonitrile-based carbon fiber material.

Furthermore, in step 4) of the above preparation method, the carbon-based porous electrode material is polyacrylonitrile-based graphite felt, carbon felt or carbon paper carbon cloth.

Further, in step 4) of the above preparation method, the mass concentration of the Nafion aqueous solution is 0.05wt%~2wt%.

Further, in step 4) of the above preparation method, the concentration of IL-MW-Mxene in the Nafion aqueous solution is 1 to 10 mg/mL.

The IL-MW-Mxene/CF composite electrode material prepared by any of the above preparation methods is used as a negative electrode in a vanadium battery.

The beneficial effects of the present invention are:

1. The etching system used in the present invention is ionic liquid-hydrochloric acid, which is more gentle and efficient. Due to the insertion of imidazole or pyridine cations, an ion-electron coupled MXene material can finally be obtained, and the electrochemical activity will be further enhanced.

2. The present invention uses microwave-assisted exfoliation technology to prepare two-dimensional lamellar MXene materials. Compared with the traditional ultrasonic layering method, it has the advantages of simplicity, short time consumption, low cost, and easy implementation of large-scale production.

3. In view of the relatively lagging kinetics of the negative electrode reaction of vanadium batteries, the present invention uses the prepared IL-MW-MXene material as a catalyst for the negative electrode reaction of vanadium batteries to narrow the kinetic gap between positive and negative electrode reactions and further improve the performance of vanadium batteries.

4. The present invention uses a green and mild ionic liquid-hydrochloric acid etching system, combined with a simple and efficient microwave-assisted stripping technology, to prepare an ion-electron coupled two-dimensional metal (IL-MW-MXene) material with a two-dimensional structure. Load it onto the surface of carbon felt fiber to obtain a new IL-MW-MXene/CF composite electrode material. This material shows excellent electrocatalytic activity for the negative electrode process of vanadium batteries, which can effectively reduce battery polarization and improve battery energy efficiency.

Description of the drawings

Figure 1 is a scanning electron microscope photograph of pre-treated MAX (a), etched layered Ti3C2Tx (b), and IL-MW-MXene (c); a transmission electron microscope photograph of IL-MW-Mxene (d).

Figure 2 is a SEM photo of blank CF (a) and IL-MW-Mxene/CF (b) prepared in Example 1.

Figure 3 is the cyclic voltammogram curve of blank CF and IL-MW-Mxene/CF electrodes in 0.8mol/LV ³⁺ +2mol/LH ₂ SO ₄ electrolyte.

Figure 4 is the charge and discharge curves of a symmetrical vanadium battery with both positive and negative electrodes made of CF and an asymmetric vanadium battery with blank CF as the positive electrode and IL-MW-MXene/CF prepared in Example 1 as the negative electrode at a current density of 200mA·cm ^-2 (a) and (b) diagrams of energy efficiency under different current densities.

Detailed ways

In order to enable other technical researchers in this field to better understand the technical solution of the present invention, a detailed description will be given below in conjunction with the accompanying drawings and examples.

Example 1

(1) Comparative example—blank CF electrode material

The commercially available finished polyacrylonitrile carbon felt CF has a thickness of 2 mm, a porosity of 95%, a fiber diameter of 5 to 10 μm, and a surface morphology as shown in Figure 2(a).

(2) IL-MW-Mxene/CF composite electrode material

The preparation method includes the following steps:

1) Pretreatment of Ti ₃ AlC ₂ MAX phase material:

Soak the Ti ₃ AlC ₂ MAX phase in absolute ethanol for 1 hour, put it into an ultrasonic machine and ultrasonic for 30 minutes to remove excess impurities, clean it, and dry it to obtain MAX phase powder. The product is shown in Figure 1(a).

2) Etch the pretreated MAX phase powder:

Immerse 500mg MAX phase powder into 50mL, 9mol/L HCl solution, add 3g C ₄ mimPF ₆ to the solution, and stir at 50°C for 24 hours. The product is washed with deionized water until neutral, and washed with absolute ethanol. Remove excess C ₄ mimPF ₆ ; centrifuge and wash, then vacuum dry at 50°C for 12 hours to obtain a multi-layer Ti ₃ C ₂ T _x sample. The product is shown in Figure 1(b).

3) Preparation of IL-MW-MXene:

Take 100 mg of the multi-layer Ti ₃ C _{2 T} After centrifugal washing with water and ethanol, and drying under vacuum conditions at 60°C for 10 h, IL-MW-MXene was obtained. The product is shown in Figure 1(cd).

4) Preparation of IL-MW-MXene/CF composite electrode material:

Take 50mg of IL-MW-MXene sample and disperse it into 25mL, 0.05wt% Nafion aqueous solution. Disperse it ultrasonically for 30 minutes. Cut the CF into appropriate sizes and soak it in the above mixture. Dry it under vacuum at 50℃. Repeat soaking and drying. Operate three times to make the IL-MW-MXene sheet material evenly bonded to the surface of the carbon fiber to obtain the IL-MW-MXene/CF composite electrode material. Figure 2(b) is a scanning electron microscope photo of the obtained IL-MW-MXene/CF composite electrode material. It can be seen that the fiber diameter is about 5 μm, and the two-dimensional layered MXene material is evenly distributed on the surface.

Example 2 Electrochemical properties of IL-MW-Mxene/CF composite electrode material

(1) Cyclic voltammetry test

Method: Blank CF and IL-MW-Mxene/CF composite electrode materials (area 1×1cm ² , thickness 1mm) were used as working electrodes, saturated calomel electrode was used as reference electrode, and platinum sheet (2×2cm ² ) was used as auxiliary electrode A three-electrode system is formed, and the electrolyte is 0.8MV ³⁺ +2M H ₂ SO ₄ .

As shown in Figure 3, the reaction current on the IL-MW-Mxene/CF composite electrode is significantly larger than that of the blank CF, and the redox peak position difference ΔEp is significantly smaller than that of the blank CF, indicating that after introducing IL-MW-MXene on the CF surface, the electrode pair The electrocatalytic activity of the negative electrode reaction of vanadium batteries has been significantly improved.

(2) Single battery charge and discharge test

Method: Use blank CF as the positive electrode, use blank CF and IL-MW-Mxene/CF as the negative electrode respectively, use the conductive plastic plate as the current collecting plate, Nafion212 membrane as the separator, the original electrolyte of the positive and negative electrodes is 1.7 mol· L ^-1 VOSO ₄ +3.0mol·L ^-1 H ₂ SO ₄ solution, the volume ratio of positive and negative electrolytes is 2:1. The test temperature is 25°C, the charge and discharge cut-off voltages are 1.6V and 0.8V respectively, the current density is 150-200mA·cm ^-2 , and the charge and discharge cycle is 5 times at each current density. The electrolyte flow rate was controlled at 30 mL·min ^-1 using a peristaltic pump.

As shown in Figure 4(a), compared with the symmetrical battery with CF as both positive and negative electrodes, the asymmetric battery with IL-MW-MXene/CF as the negative electrode shows lower current density at 150mA·cm ^-2 The charging platform and higher discharge platform indicate that it has a lower polarization overpotential, and correspondingly its energy efficiency at various current densities (Figure 4(b)) is also relatively high.

Claims (8)

1. The preparation method of the high-performance IL-MW-Mxene/CF composite electrode material is characterized by comprising the following steps:

1)Ti ₃ AlC ₂ pretreatment of MAX phase material: ti is mixed with ₃ AlC ₂ Soaking MAX phase in absolute ethanol for 1h, performing ultrasonic treatment for 30min to remove excessive impurities, cleaning, and oven drying to obtain MAX phase powder;

2) Etching the pretreated MAX phase powder: the ionic liquid-hydrochloric acid is used as an etchant, the etching temperature is 30-60 ℃, the etching time is 12-72 hours, the product is washed to be neutral by deionized water and absolute ethyl alcohol after etching, and then the multi-layer Ti is obtained by vacuum drying ₃ C ₂ T _x A sample is prepared for standby;

3) The multi-layer Ti obtained after etching ₃ C ₂ T _x The sample was peeled and layered: multilayer Ti ₃ C ₂ T _x Dispersing the sample in water, and layering multiple layers of Ti by using microwave-assisted layering technology ₃ C ₂ T _x The sample was further delaminated and the resulting product cooled to room temperature, thenCentrifugal washing with deionized water and ethanol, and vacuum drying to obtain IL-MW-MXene;

4) Preparation of IL-MW-MXene/CF composite electrode material: soaking the carbon-based porous electrode material in Nafion aqueous solution containing IL-MW-MXene, then drying at 50 ℃, and repeating the soaking and drying operation for 1-3 times, so that the IL-MW-MXene sheet material is uniformly adhered to the surface of the carbon fiber, and the IL-MW-MXene/CF composite electrode material is obtained.

2. The preparation method according to claim 1, wherein in the step 2), the ionic liquid-hydrochloric acid etchant is a mixed solution of 5-9 mol/L HCl and 1-10 wt% of hexafluorophosphate ionic liquid of pyridine or a mixed solution of 5-9 mol/L HCl and hexafluorophosphate ionic liquid of imidazole.

3. The method according to claim 1, wherein in step 3), the microwave-assisted delamination technique conditions are: the microwave power is 750W, and the treatment time is 2-10 min.

4. The method of claim 1, wherein in step 4), the carbon-based porous electrode material is a polyacrylonitrile-based carbon fiber material.

5. The method of claim 4, wherein in step 4), the carbon-based porous electrode material is a polyacrylonitrile-based graphite felt, a carbon felt, or a carbon paper carbon cloth.

6. The method according to claim 1, wherein in the step 4), the mass concentration of the Nafion aqueous solution is 0.05wt% to 2wt%.

7. The method according to claim 1, wherein in step 4), the concentration of the IL-MW-Mxene in the Nafion aqueous solution is 1-10 mg/mL.

8. The use of the IL-MW-Mxene/CF composite electrode material prepared by the method of any one of claims 1-7 as a negative electrode in a vanadium battery.