CN115466417B - A kind of MXene/polyphosphazene-based flexible electrode material and its preparation method and application - Google Patents

Abstract

The invention discloses a preparation method and application of a high oxidation resistance MXene/polyphosphazene flexible electrode material. In the present invention, a large amount of single-layer or few-layer two-dimensional MXene is obtained by etching and stripping a fluorine-containing solution, a one-step in-situ polymerization method is used to prepare MXene/polyphosphazene composites, and then a sandwich-structured MXene/polyphosphazene is prepared by vacuum filtration Conductive thin film electrodes. After surface modification, the interlayer spacing of MXene composites increases, which is conducive to the rapid transport of electrolyte ions and the exposure of active sites; the composite has a higher affinity for electrolyte ions, which further improves the interlayer ion transport speed and ion storage capacity; and The surface-modified polyphosphazene hinders the reaction of MXene with oxygen and effectively improves the oxidation resistance of MXene. The operation process of the present invention is controllable and the process is simple. The prepared flexible film electrode material has the characteristics of good oxidation resistance, high capacity, and excellent flexibility. It does not need conductive agents and adhesives, greatly reduces costs, and has comparative advantages in the field of energy storage. Great application potential.

Description

A kind of MXene/polyphosphazene-based flexible electrode material and its preparation method and application

technical field

The invention belongs to the technical field of electrode materials, in particular to a preparation method and application of a polyphosphazene surface-modified MXene flexible electrode material.

Background technique

With the rapid development of science and technology, wearable electronic devices have brought convenience to our life. Wearable systems hold great promise for applications in healthy aging, patient monitoring, emergency management, home energy management, and self-health management. In order to realize the commercialization of wearable electronic devices, their power supply components also need to be flexible and high-performance. Therefore, high-performance flexible energy storage devices will increasingly show their potential market value. Electrode materials are key factors affecting the performance of energy storage devices (batteries, supercapacitors, etc.), and the development of electrode materials with both high flexibility and high capacity has become a major problem.

MXene is a novel two-dimensional transition metal carbon/nitride, which is etched and exfoliated to obtain loosely stacked nanosheets with abundant surface functional groups (-OH, =O, -Cl, or -F) and a small amount of point defects. The conductive inner transition metal carbon/nitride layer can quickly donate electrons to the electrochemically active sites; the subnanometer interlayer slits between the 2D flakes can ensure fast ion transport; the excellent mechanical properties of 2D materials can The self-supporting flexible electrodes are formed under the condition of , which makes MXene considered as an ideal electrode material for flexible energy storage devices.

Studies have shown that MXene materials store charges by intercalation, and interlayer spacing is one of the prerequisites for limiting the diffusion of electrolyte ions. However, the strong binding energy between MXene nanosheets (2–6 times that of graphite and _MoS2 ), and the high Young’s modulus perpendicular to the sheets, indicate that single-layer MXene sheets tend to form a stacked structure, which severely limits the electrolyte Penetration and rapid transport of ions. Therefore, it is very important to design a fast ion migration channel.

Due to the high proportion of metal atoms exposed on the surface, the unsaturated defects of MXene are easily oxidized to high-valent metal oxide semiconductors with collapse of the two-dimensional structure even under ambient conditions. This changes the surface chemistry and morphology of MXenes, which ultimately degrades the performance of MXenes in applications such as power storage. This not only limits the application of MXene itself, but also poses a great challenge to the preparation of MXene-based composite materials.

Polyphosphazene is a representative organic-inorganic hybrid material in which the nitrogen and phosphorus atoms in the main chain are arranged alternately through single and double bonds. Due to the wide variety of side groups, these polymers have many excellent physical and chemical properties, as well as related application properties. Most fundamentally, the unique backbone structure ensures its natural flame retardant synergy and thermal stability.

Contents of the invention

In order to simultaneously solve the problems of MXene self-stacking and easy oxidation, the present invention provides an MXene/polyphosphazene-based flexible electrode material and its preparation method and application. The present invention adopts a one-step polymerization method to modify polyphosphazene on the surface of MXene, and increases the interlayer distance to ensure rapid transport of electrolyte ions and full contact between ions and active sites while inhibiting the oxidation of MXene. The prepared product is used in It exhibits excellent performance in the fields of supercapacitors and various ion batteries.

The MXene composite material provided by the present invention is in-situ grafted on the surface of MXene nanosheets through the reaction of triethylamine-catalyzed polyphosphazene, R monomer and surface end groups, expressed as MXene/polyphosphazene.

The technical scheme provided by the invention is as follows:

In the first aspect, the present invention provides a kind of preparation method of MXene/polyphosphazene-based flexible electrode material, comprising the following steps:

(1) Add the MAX phase powder into LiF/HCl or hydrofluoric acid solution, stir and react for a certain period of time under heating conditions, after washing, add deionized water to the LiF/HCl system to strip, and add organic matter intercalation to the hydrofluoric acid system The agent was stripped, and the upper suspension was freeze-dried to obtain MXene nanosheets;

(2) Disperse the MXene nanosheets in an organic solvent containing hexachlorocyclotriphosphazene and R monomer, under the protection of an inert gas, add a catalyst to react to obtain MXene/polyphosphazene;

(3) Disperse MXene/polyphosphazene and MXene nanosheets in water, vacuum filter, and dry naturally in air to obtain a flexible film.

Further, in the step (1), the MAX phase powder includes but not limited to Ti ₃ AlC ₂ , Ti ₂ AlC, Ti ₃ AlCN, Ti ₂ AlN, Ti ₄ AlN ₃ , Ti ₃ SiC ₂ , Ti ₂ SnC, Ti ₃ SnC ₂ , Ta ₂ AlC, Ta ₄ AlC3, Nb ₂ AlC, Nb ₄ AlC ₃ , V ₂ AlC, V ₄ AlC ₃ , V ₂ GeC, V ₂ GaC, V _{2 ZnC, V 2 SnC} , Mo ₂ Ga ₂ C , Mo ₂ GeC, Cr ₂ AlC, Mo ₂ Ti ₂ AlC ₃ , Mo ₂ TiAlC ₂ , VCrAlC, TiVAlC, Ti ₂ VAlC ₂ , Cr ₂ TiAlC, TiNbAlC, VNbAlC, (W _2/3 Y _1/3 ) ₂ AlC , (Mo _2/3 Y _1/3 ) ₂ AlC, Mo _2/3 Sc _1/3 AlC.

Further, in the step (1), the concentration of the hydrochloric acid solution is 6-12M, the mass ratio of LiF to MAX phase powder is 1-6:1; the concentration of the hydrofluoric acid solution is 10-40wt%; the heating and stirring reaction time for 24-168 hours.

Further, in the step (1), organic intercalants include but are not limited to dimethyl sulfoxide, tetramethylammonium hydroxide and tetrabutylammonium hydroxide, after using LiF/HCl system to etch MXene, in the etching step Residual Li ⁺ can weaken the interlayer force of MXene nanosheets, so only need to add deionized water to peel off multi-layer MXene to obtain few-layer MXene nanosheets; after using HF system to etch MXene, an additional organic intercalation agent is needed To weaken the interlayer force of MXene nanosheets to achieve the effect of peeling off multilayer MXene.

Further, in the step (1), MXene nanosheets include but are not limited to Ti ₃ C ₂ , Ti ₂ C, Ti ₃ CN, V ₄ C ₃ , V ₂ C, Nb ₄ C ₃ , Nb ₂ C, Mo ₂ C, Mo _1.33 C, Mo ₂ Ti ₂ C ₃ , Mo ₂ TiC, W _1.33 C.

Further, in the step (2), R monomers include but are not limited to 4,4'-diaminodiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, 4,4'-diaminodiphenyl ether, 4,4'-dihydroxydiphenyl ether, 4,4'-dimercaptodiphenyl ether.

Further, in the step (2), the organic solvent is anhydrous acetonitrile.

Further, in the step (2), the catalyst is triethylamine.

Further, in the step (2), the mass ratio of hexachlorocyclotriphosphazene and MXene nanosheets is 1-100:100, the reaction temperature is 60-90°C, and the heating time is 6-18 hours.

Further, in the step (3), the mass ratio of MXene/polyphosphazene to MXene nanosheets is 0.5-4:1.

The method that the present invention adopts can obtain surface larger, the MXene nano sheet that terminal group functional group (-OH,=O,-F,-Cl) is abundant, chlorocyclotriphosphazene and R monomer are under the catalysis of triethylamine A nucleophilic substitution polycondensation reaction occurs to generate polyphosphazene, and the P-Cl group of hexachlorocyclotriphosphazene can react with the -OH on the MXene nanosheets so that the polyphosphazene is anchored on the surface of MXene.

In the second aspect, the present invention provides the MXene/polyphosphazene-based flexible electrode material prepared by the method described in the first aspect.

In a third aspect, the present invention provides the application of the MXene/polyphosphazene-based flexible electrode material described in the second aspect as a supercapacitor or battery electrode material.

The beneficial effects of the present invention are as follows:

The present invention uses polyphosphazene and R monomers to modify the surface of MXene to effectively prevent the self-stacking of MXene sheets, increase the layer spacing, widen the interlayer channels of MXene, and facilitate the rapid transmission of electrolyte ions. The increased interlayer spacing can achieve a high ion-accessible surface and expose more electrochemically active sites; the composite material has a higher affinity for electrolyte ions, which further improves the interlayer ion transport speed and ion storage capacity. These features lead to higher capacity and rate performance when the composite is used as an electrode material. In addition, the surface-modified polyphosphazene hinders the reaction of MXene with oxygen, effectively improving the oxidation resistance of MXene.

Description of drawings

Figure 1 is a schematic diagram of the technical route of polyphosphazene-modified MXene (taking Ti ₃ C ₂ as an example).

Figure 2 is the X-ray diffraction pattern (XRD pattern) of MXene (taking Ti ₃ C ₂ as an example) and MXene/polyphosphazene.

Figure 3 is the XRD pattern of MXene (taking Ti ₃ C ₂ as an example) and MXene/polyphosphazene after six months of storage at room temperature.

Figure 4 is the cyclic voltammetry curves of MXene (taking Ti ₃ C ₂ as an example) and MXene/polyphosphazene.

Figure 5 is a graph of the rate performance of MXene (taking Ti ₃ C ₂ as an example) and MXene/polyphosphazene.

Detailed ways

The present invention is described in detail below in conjunction with the examples, but the protection scope of the present invention is not limited to the following examples.

Example 1

Prepare MXene/polyphosphazene-based flexible electrode materials, the steps are as follows:

(1) Add 1g LiF into 25ml 9M HCl solution, stir for 5 minutes to dissolve and set aside. Afterwards, 1 g of Ti ₃ AlC ₂ powder was added into the above solution, and reacted at 40° C. for 24 hours. Then the powder obtained by the reaction was washed with deionized water, and centrifuged until the pH of the washed supernatant was close to 6. Add 100ml of deionized water to the multi-layered Ti ₃ C ₂ obtained by washing, sonicate for 1 hour under the protection of nitrogen, and centrifuge to obtain a dark green supernatant, which is the few-layer Ti ₃ C ₂ nanosheets, which are freeze-dried for later use.

(2) Weigh 200 mg of few-layer Ti ₃ C ₂ nanosheets and disperse them into 100 ml of anhydrous acetonitrile solution containing 10 mg of hexachlorocyclotriphosphazene and 24 mg of 4,4'-diaminodiphenylsulfone, and then add a small amount of triethylamine , reacted at 85° C. for 12 hours under the protection of nitrogen. After cooling to room temperature, the product was washed with anhydrous acetonitrile and dried in vacuum to obtain MXene/polyphosphazene composites.

(3) Weigh 10 mg MXene/polyphosphazene and 5 mg MXene and disperse in 30 ml deionized water, and vacuum filter to obtain a flexible self-supporting thin film electrode.

The prepared material was characterized by X-ray powder diffraction (see Figure 2), and the interlayer distance of the polyphosphazene surface-modified MXene composite material increased from 1.26nm of few-layer MXene to 1.47nm.

After storing MXene/polyphosphazene and MXene at room temperature for six months, it was found that MXene/polyphosphazene had no obvious oxidation, while MXene had observed the formation of TiO ₂ (see Figure 3), and the surface-modified polyphosphazene was effective Enhanced the antioxidant activity of MXene.

The prepared thin film electrode was directly used as a working electrode, and the CV research was carried out at a scan rate of 2mV s ^-1 in 3M H ₂ SO ₄ electrolyte solution, and it was found that the specific capacitance increased from 286F g ^-1 when unmodified to 380F g ^-1 (see Figure 4), the rate characteristic increased from 6% to 60% (see Figure 5).

Example 2

Prepare MXene/polyphosphazene-based flexible electrode materials, the steps are as follows:

(1) Disperse 0.5g of Nb ₄ AlC ₃ in 40mL of 50% HF solution and react at room temperature for 100 hours. Then the powder obtained by the reaction was washed with deionized water, and centrifuged until the pH of the washed supernatant was close to 6. The multi-layered Nb ₄ C ₃ obtained by washing was added to 10ml of 2.5wt% tetramethylammonium hydroxide aqueous solution, shaken by hand for 15 minutes, centrifuged to obtain the supernatant which was the few-layered Nb ₄ C ₃ nanosheets, and freeze-dried for later use.

(2) Weigh 200 mg of few-layer Nb ₄ C ₃ nanosheets and disperse them into 100 ml of anhydrous acetonitrile solution containing 10 mg of hexachlorocyclotriphosphazene and 24 mg of 4,4'-dihydroxydiphenyl sulfone, and then add a small amount of triethylamine, React at 85°C for 12 hours under the protection of nitrogen. After cooling to room temperature, the product was washed with anhydrous acetonitrile and dried in vacuum to obtain MXene/polyphosphazene composites.

(3) Weigh 10 mg MXene/polyphosphazene and 5 mg MXene and disperse in 30 ml deionized water, and vacuum filter to obtain a flexible self-supporting thin film electrode.

Example 3

Prepare MXene/polyphosphazene-based flexible electrode materials, the steps are as follows:

(1) Add 2g LiF into 25ml 12M HCl solution, stir for 5 minutes to dissolve and set aside. Afterwards, 1 g of Mo ₂ Ga ₂ C powder was added to the above solution, and reacted at 40° C. for 168 hours. Then the powder obtained by the reaction was washed with deionized water, centrifuged, washed three times with 1M HCl and 1M LiCl solutions successively, and then washed with deionized water until the pH of the supernatant was close to 6. Add 100ml of deionized water to the multilayer Mo ₂ C obtained by washing, sonicate for 1 hour under the protection of nitrogen, and centrifuge to obtain the supernatant, which is the few-layer Mo ₂ C nanosheets, which are freeze-dried for later use.

(2) Weigh 200 mg of few-layer Mo ₂ C nanosheets and disperse them into 100 ml of anhydrous acetonitrile solution containing 10 mg of hexachlorocyclotriphosphazene and 24 mg of 4,4'-diaminodiphenyl ether, and then add a small amount of triethylamine, React at 85°C for 12 hours under the protection of nitrogen. After cooling to room temperature, the product was washed with anhydrous acetonitrile and dried in vacuum to obtain MXene/polyphosphazene composites.

(3) Weigh 10 mg MXene/polyphosphazene and 5 mg MXene and disperse in 30 ml deionized water, and vacuum filter to obtain a flexible self-supporting thin film electrode.

Example 4

Prepare MXene/polyphosphazene-based flexible electrode materials, the steps are as follows:

(1) Disperse 1g Mo _2/3 Sc _1/3 AlC in 20mL HF solution and react at room temperature for 24 hours. Then the powder obtained by the reaction was washed with deionized water, and centrifuged until the pH of the washed supernatant was close to 6. The multi-layer Mo _1.33 C obtained by washing was added to 50ml of 8wt% tetramethylammonium hydroxide aqueous solution, shaken by hand for 15 minutes, washed with deionized water, centrifuged to obtain the supernatant which was the few-layer Mo _1.33 C nanosheets, and freeze-dried spare.

(2) Weigh 200mg of few-layer Mo _1.33 C nanosheets and disperse them into 100ml of anhydrous acetonitrile solution containing 10mg of hexachlorocyclotriphosphazene and 24mg of 4,4'-dihydroxydiphenyl ether, then add a small amount of triethylamine, React at 85°C for 12 hours under the protection of nitrogen. After cooling to room temperature, the product was washed with anhydrous acetonitrile and dried in vacuum to obtain MXene/polyphosphazene composites.

(3) Weigh 10 mg MXene/polyphosphazene and 5 mg MXene and disperse in 30 ml deionized water, and vacuum filter to obtain a flexible self-supporting thin film electrode.

Example 5

Prepare MXene/polyphosphazene-based flexible electrode materials, the steps are as follows:

(1) Disperse 1 g of V ₂ AlC in 20 mL of HF solution, and react at 35° C. for 120 hours. Then the powder obtained by the reaction was washed with deionized water, and centrifuged until the pH of the washed supernatant was close to 6. The multi-layer V ₂ C obtained by washing was added to 30ml of 25wt% tetramethylammonium hydroxide aqueous solution, stirred for 12 hours, after washing with deionized water, sonicated for 30 minutes under nitrogen protection, and the supernatant obtained by centrifugation was the few-layer V ₂ C nanosheets , freeze-dried for later use.

(2) Weigh 200 mg of few-layer V ₂ C nanosheets and disperse them into 100 ml of anhydrous acetonitrile solution containing 10 mg of hexachlorocyclotriphosphazene and 24 mg of 4,4'-dimercaptodiphenyl ether, and then add a small amount of triethylamine, React at 85°C for 12 hours under the protection of nitrogen. After cooling to room temperature, the product was washed with anhydrous acetonitrile and dried in vacuum to obtain MXene/polyphosphazene composites.

(3) Weigh 10 mg MXene/polyphosphazene and 5 mg MXene and disperse in 30 ml deionized water, and vacuum filter to obtain a flexible self-supporting thin film electrode.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any modification made by those skilled in the art within the technical scope disclosed in the present invention is equivalent to Replacement and improvement, etc., should be included in the scope of protection of the invention.

Claims (9)

1. The preparation method of the MXene/polyphosphazene-based flexible electrode material is characterized by comprising the following steps of:

(1) Adding MAX phase powder into LiF/HCl or hydrofluoric acid solution, stirring and reacting for a certain time under heating condition, washing, adding deionized water into LiF/HCl system for stripping, adding organic intercalation agent into hydrofluoric acid system for stripping, and freeze drying upper suspension to obtain MXene nanosheets;

(2) Dispersing the MXene nano-sheets into an organic solvent containing hexachlorocyclotriphosphazene and R monomers, and adding a catalyst under the protection of inert gas to react to obtain MXene/polyphosphazene; the R monomer comprises one or more of 4,4' -diaminodiphenyl sulfone, 4' -dihydroxydiphenyl sulfone, 4' -diaminodiphenyl ether, 4' -dihydroxydiphenyl ether and 4,4' -dimercaptodiphenyl ether;

(3) Dispersing the MXene/polyphosphazene and MXene nano-sheets in water, carrying out vacuum filtration, and naturally drying in air to obtain the flexible film.

2. The method of manufacturing according to claim 1, characterized in that: in the step (1), the MAX phase powder contains Ti ₃ AlC ₂ ，Ti ₂ AlC，Ti ₃ AlCN，Ti ₂ AlN，Ti ₄ AlN ₃ ，Ti ₃ SiC ₂ ，Ti ₂ SnC，Ti ₃ SnC ₂ ，Ta ₂ AlC，Ta ₄ AlC3，Nb ₂ AlC，Nb ₄ AlC ₃ ，V ₂ AlC，V ₄ AlC ₃ ，V ₂ GeC，V ₂ GaC，V ₂ ZnC，V ₂ SnC，Mo ₂ Ga ₂ C，Mo ₂ GeC，Cr ₂ AlC，Mo ₂ Ti ₂ AlC ₃ ，Mo ₂ TiAlC ₂ ，VCrAlC，TiVAlC，Ti ₂ VAlC ₂ ，Cr ₂ TiAlC，TiNbAlC，VNbAlC，(W _2/3 Y _1/3 ) ₂ AlC，(Mo _2/3 Y _1/3 ) ₂ AlC，Mo _2/3 Sc _1/3 One or more of AlC.

3. The method of manufacturing according to claim 1, characterized in that: in the step (1), the concentration of the hydrochloric acid solution is 6-12M, and the mass ratio of LiF to MAX phase powder is 1-6:1; the concentration of the hydrofluoric acid solution is 10-40wt%; the reaction time is 24-168 hours by heating and stirring.

4. The method of manufacturing according to claim 1, characterized in that: in the step (1), the organic intercalating agent comprises dimethyl sulfoxide, tetramethylammonium hydroxide and tetrabutylammonium hydroxide.

5. The method of manufacturing according to claim 1, characterized in that: in the step (2), the organic solvent is anhydrous acetonitrile, and the catalyst is triethylamine.

6. The method of manufacturing according to claim 1, characterized in that: in the step (2), the mass ratio of hexachlorocyclotriphosphazene to MXene nano-sheets is 1-100:100, the reaction temperature is 60-90 ℃, and the heating time is 6-18 hours.

7. The method of manufacturing according to claim 1, characterized in that: in the step (3), the mass ratio of the MXene/polyphosphazene to the MXene nano-sheets is 0.5-4:1.

8. An MXene/polyphosphazene based flexible electrode material, characterized in that: a method according to any one of claims 1 to 7.

9. Use of an MXene/polyphosphazene based flexible electrode material according to claim 8 as an electrode material for a super capacitor or a battery.