阅读说明：本技术 柔性自支撑MXene/CuS超级电容器电极材料的制备方法 (Preparation method of flexible self-supporting MXene/CuS supercapacitor electrode material ) 是由 党阿磊 孙弋婷 刘鑫 李铁虎 赵廷凯 李�昊 艾艳玲 于 2020-11-24 设计创作，主要内容包括：本发明涉及一种柔性自支撑MXene/CuS超级电容器电极材料的制备方法,采用原位腐蚀、高功率超声辅助、离心筛分等方法获得了大量单层或者少层二维MXene(Ti_3C_2)；采用一步水热法制备纳米花状材料CuS；然后通过层层自组装(LBL,layer-by-layer)抽滤法制备三明治结构的MXene/CuS导电薄膜电极材料；以聚乙烯醇和硫酸为原料制备凝胶电解质,MXene/CuS导电薄膜作为电极材料,组合成固态电解质柔性自支撑对称超级电容器。本发明操作流程可控且工艺简单,所制备的柔性自支撑超级电容器电极材料具有环境友好、比容量高、柔性优良等特点,且不需要导电剂和粘接剂,大大降低成本,在能源存储等领域具有很好的应用潜力。(The invention relates to a preparation method of a flexible self-supporting MXene/CuS super capacitor electrode material, which adopts in-situ corrosion and high work powerA large amount of monolayer or few-layer two-dimensional MXene (Ti) is obtained by methods such as ultrasonic assistance, centrifugal screening and the like 3 C 2 ) (ii) a Preparing a nanoflower CuS by a one-step hydrothermal method; then preparing the MXene/CuS conductive film electrode material with a sandwich structure by a layer-by-layer self-assembly (LBL) suction filtration method; polyvinyl alcohol and sulfuric acid are used as raw materials to prepare gel electrolyte, and MXene/CuS conductive films are used as electrode materials to combine the solid electrolyte flexible self-supporting symmetrical super capacitor. The preparation method disclosed by the invention is controllable in operation flow and simple in process, and the prepared flexible self-supporting supercapacitor electrode material has the characteristics of environmental friendliness, high specific capacity, excellent flexibility and the like, does not need a conductive agent and an adhesive, greatly reduces the cost, and has good application potential in the fields of energy storage and the like.)

1. A preparation method of a flexible self-supporting MXene/CuS supercapacitor electrode material is characterized by comprising the following steps:

step 1, accordion-like Mxene or Ti₃C₂The preparation of (1):

etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method comprises the following steps: slowly adding 2-15 ml of concentrated hydrochloric acid into a container filled with 1-10 ml of deionized water, adding 0.1-5 g of LiF powder, and after LiF is completely dissolved, adding 0.1-3 g of MAX-phase ceramic powder Ti₃AlC₂Slowly adding;

putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, collecting and washing a product after reacting for 10-30 h to obtain a dark green MXene solution;

step 2, preparation of a two-dimensional MXene solution material:

treating the accordion-shaped MXene prepared in the step 1 by adopting a centrifugal screening method, namely, under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step 1 for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely a two-dimensional MXene solution;

step 3, preparing the nanoflower-shaped CuS by adopting a one-step hydrothermal method:

0.1-5 g of copper chloride dihydrate CuCl is added₂·H₂O and 0.1-5 g of thiourea CH₄N₂S is dissolved in 10-30 ml of deionized water, then thiourea is slowly dripped into the copper chloride solution, and the mixture is magnetically stirred for 10-40 min to be uniformly mixed, so that a precursor is obtained;

transferring the precursor solution into a polytetrafluoroethylene hydrothermal reaction kettle, and reacting for 3-10 h at 100-200 ℃; after the reaction is completed and the reaction product is cooled to room temperature, washing the product for many times by using deionized water and absolute ethyl alcohol, drying and grinding the product to obtain powder nano flower-shaped CuS;

step 4, preparing the MXene/CuS conductive film electrode material by adopting a layer-by-layer self-assembly suction filtration method:

carrying out suction filtration treatment on the MXene solution prepared in the step 2 to obtain a layer of clay-like Mxene with the thickness of 200 nm-2 microns;

dispersing the nano flower-shaped CuS prepared in the step (3) in deionized water, performing ultrasonic treatment to obtain a uniformly dispersed nano flower-shaped CuS solution, continuing to perform suction filtration to enable the CuS to be loaded on an MXene layer, and then continuing to add the MXene solution to obtain MXene-CuS-Mxene with a sandwich structure;

repeating the steps for 1-5 times, and drying to obtain the MXene/CuS conductive film;

step 5, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol PVA into 10-100 ml of deionized water under stirring, and slowly dropwise adding 1-10 ml of concentrated sulfuric acid H₂SO₄Stirring for 1-10 min to disperse the mixture evenly to form a mixed solution;

stirring the mixed solution, starting heating, and enabling the solution to be transparent when the temperature is raised to 50-100 ℃;

pouring the transparent liquid into a culture dish, freezing at-5-20 ℃ for 1-3H, taking out, and airing at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte;

step 6, assembling the flexible self-supporting MXene/CuS super capacitor: two MXene/CuS conductive films with the same size and mass and prepared in the step 4 are used as electrode materials, and PVA-H with the same size and mass and prepared in the step 5 is used as an electrode material₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene/CuS super capacitor.

2. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: in the step 1, the washing treatment of the product prepared by the etching method comprises the following steps: washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing with deionized water until the pH value is 6-7.

3. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: in the step 2, the two-dimensional MXene solution material after centrifugal screening treatment is a single-layer or few-layer Mxene, the surface Zeta potential of the Mxene is negative, and the size of the Mxene is 1-30 μm.

4. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 3, wherein: the few-layer Mxene comprises 1-3 layers.

5. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: in the step 3, the thickness of the nanoflower-shaped CuS sheet layer is 10 nm-1 mu m.

6. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: in the step 3, the one-step hydrothermal method product washing and drying treatment is to repeatedly wash the product with deionized water and absolute ethyl alcohol respectively and then dry the product at 40-80 ℃.

7. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: in the step 4, when the conductive film is prepared by an LBL suction filtration method, a microporous composite fiber membrane with the aperture size of 0.1-1 mu m is adopted.

8. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: when the MXene/CuS conductive film is prepared in the step 4, the content of the nano flower-shaped CuS is 1-20 wt%.

9. The preparation method of the flexible self-supporting MXene/CuS supercapacitor electrode material according to claim 1, wherein: the MXene/CuS conductive film and PVA-H in the step 6₂SO₄The gel electrolyte is 1-5 multiplied by 1-5 cm in size²。

10. A testing method of the flexible self-supporting MXene/CuS super capacitor electrode material prepared according to any one of claims 1 to 9 is characterized in that: testing the specific capacity of the flexible self-supporting MXene/CuS super capacitor: and performing CV test by adopting a cyclic voltammetry method, wherein the scanning speed range is 1-500 mV/s, and performing electrochemical test on the specific capacitance of the flexible self-supporting MXene/CuS super capacitor.

Technical Field

The invention belongs to the field of nano energy materials, and relates to a preparation method of a flexible self-supporting MXene/CuS super capacitor electrode material.

Background

With the rapid development of science and technology, wearable electronic products (intelligent sports equipment, electronic skins, flexible screens and the like) become a new hotspot, can be used in a plurality of fields such as medical care, navigation, social networks and the like, and bring convenience to our lives through the application of different scenes. In order to realize the industrialization of wearable electronic products, the energy storage device also needs to have high flexibility, so that the flexible supercapacitor increasingly shows a rather high market value. However, because the wearable electronic product has a small volume, and the capacity of the corresponding energy storage device cannot be guaranteed, the energy storage device of the wearable electronic product not only needs to guarantee high flexibility, but also needs to guarantee the capacity. Therefore, it is important to develop a flexible supercapacitor electrode material having high flexibility and high specific capacity.

MXene is a new two-dimensional inorganic compound composed of several atomic thicknesses of carbides, nitrides or carbonitrides of transition metals. The nano material has a unique two-dimensional layered structure, excellent physical property characteristics and high anisotropy of crystal growth, and has a metal or graphene-like ultrahigh-conductivity surface (-8000S/cm) and high energy and power density characteristics (the redox reaction of surface transition state metal and electrolyte ions can generate high pseudocapacitance), so that the nano material has great potential as an energy storage electrode material in recent research, and is considered as an ideal supercapacitor electrode material.

However, MXene with a two-dimensional structure is very prone to self-stacking during the preparation of the electrode material, thereby greatly hindering the transport of ions in the electrode material. Therefore, it still has a great challenge how to enable more electrolyte ions to perform oxidation-reduction reaction on the active sites of the two-dimensional material, so as to increase the transmission rate of the electrolyte ions in the electrode material while effectively improving the specific capacitive performance of the electrode material.

Most of the metal sulfides are semiconductors, and have good conductivity, corrosion resistance and chemical stability. When the metal sulfide is used as an electrode material, the metal sulfide has a higher electron transfer rate and thus has a higher specific capacity, and therefore, the metal sulfide is often used in the electrode material of an energy storage device. But the cycle performance is poor, which causes great reduction of electrochemical performance, and therefore, the further application of the electrode material is limited to a great extent.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a preparation method of a flexible self-supporting MXene/CuS supercapacitor electrode material.

Technical scheme

A preparation method of a flexible self-supporting MXene/CuS supercapacitor electrode material is characterized by comprising the following steps:

step 1, accordion-like Mxene or Ti₃C₂The preparation of (1):

etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method comprises the following steps: slowly adding 2-15 ml of concentrated hydrochloric acid into a container filled with 1-10 ml of deionized water, and then adding 0.1-5 g of concentrated hydrochloric acidLiF powder, after LiF is completely dissolved, 0.1-3 g MAX phase ceramic powder Ti is added₃AlC₂Slowly adding;

putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, collecting and washing a product after reacting for 10-30 h to obtain a dark green MXene solution;

step 2, preparation of a two-dimensional MXene solution material:

treating the accordion-shaped MXene prepared in the step 1 by adopting a centrifugal screening method, namely, under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step 1 for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely a two-dimensional MXene solution;

step 3, preparing the nanoflower-shaped CuS by adopting a one-step hydrothermal method:

0.1-5 g of copper chloride dihydrate CuCl is added₂·H₂O and 0.1-5 g of thiourea CH₄N₂S is dissolved in 10-30 ml of deionized water, then thiourea is slowly dripped into the copper chloride solution, and the mixture is magnetically stirred for 10-40 min to be uniformly mixed, so that a precursor is obtained;

transferring the precursor solution into a polytetrafluoroethylene hydrothermal reaction kettle, and reacting for 3-10 h at 100-200 ℃; after the reaction is completed and the reaction product is cooled to room temperature, washing the product for many times by using deionized water and absolute ethyl alcohol, drying and grinding the product to obtain powder nano flower-shaped CuS;

step 4, preparing the MXene/CuS conductive film electrode material by adopting a layer-by-layer self-assembly suction filtration method:

carrying out suction filtration treatment on the MXene solution prepared in the step 2 to obtain a layer of clay-like Mxene with the thickness of 200 nm-2 microns;

dispersing the nano flower-shaped CuS prepared in the step (3) in deionized water, performing ultrasonic treatment to obtain a uniformly dispersed nano flower-shaped CuS solution, continuing to perform suction filtration to enable the CuS to be loaded on an MXene layer, and then continuing to add the MXene solution to obtain MXene-CuS-Mxene with a sandwich structure;

repeating the steps for 1-5 times, and drying to obtain the MXene/CuS conductive film;

step 5, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol PVA into 10-100 ml of deionized water under stirring, and slowly dropwise adding 1-10 ml of concentrated sulfuric acid H₂SO₄Stirring for 1-10 min to disperse the mixture evenly to form a mixed solution;

stirring the mixed solution, starting heating, and enabling the solution to be transparent when the temperature is raised to 50-100 ℃;

pouring the transparent liquid into a culture dish, freezing at-5-20 ℃ for 1-3H, taking out, and airing at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte;

step 6, assembling the flexible self-supporting MXene/CuS super capacitor: two MXene/CuS conductive films with the same size and mass and prepared in the step 4 are used as electrode materials, and PVA-H with the same size and mass and prepared in the step 5 is used as an electrode material₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene/CuS super capacitor.

In the step 1, the washing treatment of the product prepared by the etching method comprises the following steps: washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing with deionized water until the pH value is 6-7.

In the step 2, the two-dimensional MXene solution material after centrifugal screening treatment is a single-layer or few-layer Mxene, the surface Zeta potential of the Mxene is negative, and the size of the Mxene is 1-30 μm.

The few-layer Mxene comprises 1-3 layers.

In the step 3, the thickness of the nanoflower-shaped CuS sheet layer is 10 nm-1 mu m.

In the step 3, the one-step hydrothermal method product washing and drying treatment is to repeatedly wash the product with deionized water and absolute ethyl alcohol respectively and then dry the product at 40-80 ℃.

In the step 4, when the conductive film is prepared by an LBL suction filtration method, a microporous composite fiber membrane with the aperture size of 0.1-1 mu m is adopted.

When the MXene/CuS conductive film is prepared in the step 4, the content of the nano flower-shaped CuS is 1-20 wt%.

The MXene/CuS conductive film and PVA-H in the step 6₂SO₄The gel electrolyte is 1-5 multiplied by 1-5 cm in size²。

A testing method of the prepared flexible self-supporting MXene/CuS super capacitor electrode material is characterized by comprising the following steps: testing the specific capacity of the flexible self-supporting MXene/CuS super capacitor: and performing CV test by adopting a cyclic voltammetry method, wherein the scanning speed range is 1-500 mV/s, and performing electrochemical test on the specific capacitance of the flexible self-supporting MXene/CuS super capacitor.

Advantageous effects

The invention provides a preparation method of a flexible self-supporting MXene/CuS super capacitor electrode material, which adopts methods of in-situ corrosion, high-power ultrasonic assistance, centrifugal screening and the like to obtain a large amount of single-layer or few-layer two-dimensional MXene (Ti)₃C₂) (ii) a Preparing a nanoflower CuS by a one-step hydrothermal method; then preparing the MXene/CuS conductive film electrode material with a sandwich structure by a layer-by-layer self-assembly (LBL) suction filtration method; polyvinyl alcohol and sulfuric acid are used as raw materials to prepare gel electrolyte, and MXene/CuS conductive films are used as electrode materials to combine the solid electrolyte flexible self-supporting symmetrical super capacitor. The preparation method disclosed by the invention is controllable in operation flow and simple in process, and the prepared flexible self-supporting supercapacitor electrode material has the characteristics of environmental friendliness, high specific capacity, excellent flexibility and the like, does not need a conductive agent and an adhesive, greatly reduces the cost, and has good application potential in the fields of energy storage and the like.

The invention provides a preparation method of an MXene/CuS super capacitor electrode material which is self-supporting, environment-friendly and high in specific capacity, and the super capacitor mainly has the following advantages over the prior art:

(1) compared with the accordion-shaped or multilayer MXene, when the MXene is formed into a macroscopic electrode material, the increased specific surface area can enable more electrolyte ions and active sites to perform redox reaction (pseudo capacitance), and the specific capacity of the electrode material is improved.

(2) The nanoflower-shaped CuS is prepared by a one-step hydrothermal method, and the process is simple and the cost is low. The MXene/CuS conductive film electrode material is obtained by adopting CuS and MXene with high specific capacitance through an LBL suction filtration method, on one hand, the specific capacity of the super capacitor is improved by adding the metal sulfide; on the other hand, the nano flower-shaped CuS is inserted into the MXene interlayer, so that the aggregation and self-polymerization of MXene can be effectively prevented, and the transmission resistance of ions and the like in the electrode material is greatly reduced.

(3) The MXene/CuS conductive film electrode material obtained by carrying out LBL suction filtration on the nano flower-shaped CuS and MXene can obtain the three-dimensional flexible self-supporting conductive film without adding any conductive agent or adhesive, so that the production cost is greatly reduced.

(4) Compared with the traditional liquid electrolyte, the gel electrolyte has the advantages of greenness, no pollution, no toxicity, no liquid leakage risk and good electronic flow channel. The raw materials of polyvinyl alcohol (PVA) and sulfuric acid adopted by the invention are easy to obtain, and the operation process is simple and feasible, so that the solid electrolyte flexible self-supporting MXene/CuS super capacitor electrode material prepared by the invention has great application potential in the field of energy.

Drawings

FIG. 1 SEM photograph of MXene conductive film electrode material prepared in the invention

FIG. 2 SEM photograph of nanoflower-shaped CuS prepared in the present invention

FIG. 3 is an SEM photograph of a flexible MXene/CuS conductive thin film electrode material prepared in the invention

FIG. 4 is a macro photo of the flexible MXene/CuS conductive film electrode material prepared in the invention

FIG. 5 shows the specific capacitance change of the flexible MXene/CuS conductive film electrode material prepared in the present invention under different scanning rate conditions

FIG. 6 shows the specific capacitance variation of the flexible MXene/CuS conductive thin film electrode material with different CuS contents in the invention

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

example 1

Preparation of flexible self-supporting MXene super capacitor electrode material and research of electrochemical performance of flexible self-supporting MXene super capacitor electrode material

Preparing accordion MXene: etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method specifically comprises the following steps: measuring 2-15 ml of concentrated hydrochloric acid and 1-10 ml of deionized water, slowly adding the concentrated hydrochloric acid into a container filled with the deionized water, then weighing 0.1-5 g of LiF powder, adding the LiF powder into the diluted hydrochloric acid, and after LiF is completely dissolved, then adding 0.1-3 g of MAX-phase ceramic powder Ti₃AlC₂The addition was slow. And (3) putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, and collecting a product after reacting for 10-30 h. Washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing the product with deionized water until the pH value is 6-7 to finally obtain the dark green MXene solution.

Step two, preparing a single-layer or few-layer MXene material: processing the accordion-shaped MXene prepared in the first step by adopting a centrifugal screening method to obtain a single-layer MXene, wherein the specific steps are as follows: and (3) under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step one for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely the two-dimensional MXene solution.

Step three, preparing the MXene thin film electrode material: the method specifically comprises the following steps: and (4) carrying out suction filtration treatment on the MXene solution prepared in the second step to obtain a thin layer of clay-like MXene. Drying at 40-80 deg.C to obtain MXene conductive film with thickness of 2 μm (shown in figure 1).

Step four, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol (PVA) into 10-100 ml of deionized water under continuous stirring, and then slowly dropwise adding 1-10 ml of concentrated sulfuric acid (H) into the solution₂SO₄) And stirring for 1-10 min to disperse the mixture uniformly. And (3) placing the beaker filled with the mixed solution on a magnetic stirrer, starting heating, and observing that the solution becomes transparent when the temperature is raised to 50-100 ℃. Pouring the transparent liquid into a culture dish prepared in advance, freezing for 1-3 h at the temperature of-5-20 ℃, taking out,drying at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte.

Step five, assembling the flexible self-supporting MXene super capacitor: cutting two pieces of 1-5 x (1-5) cm²The MXene conductive film prepared in the third step is used as an electrode material, and the PVA-H prepared in the fourth step and the size of the electrode material is cut₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene super capacitor.

Testing the specific capacitance of the flexible self-supporting MXene super capacitor: and (4) performing an electrochemical test on the specific capacitance of the flexible self-supporting MXene super capacitor in the fifth step at different scanning speeds by adopting a cyclic voltammetry (CV test). Research shows that the specific capacity of the flexible self-supporting MXene super capacitor changes along with the change of the scanning speed, and the specific capacity can reach 334.41F/cm when the scanning speed is 5mV/s³As shown in fig. 6.

Example 2

Preparation of flexible self-supporting MXene/CuS-5 (the content of CuS is 5 wt%) supercapacitor electrode material and research on electrochemical properties of supercapacitor electrode material

Preparing accordion MXene: etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method specifically comprises the following steps: measuring 2-15 ml of concentrated hydrochloric acid and 1-10 ml of deionized water, slowly adding the concentrated hydrochloric acid into a container filled with the deionized water, then weighing 0.1-5 g of LiF powder, adding the LiF powder into the diluted hydrochloric acid, and after LiF is completely dissolved, then adding 0.1-3 g of MAX-phase ceramic powder Ti₃AlC₂The addition was slow. And (3) putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, and collecting a product after reacting for 10-30 h. Washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing the product with deionized water until the pH value is 6-7 to finally obtain the dark green MXene solution.

Step two, preparing a single-layer or few-layer MXene material: processing the accordion-shaped MXene prepared in the first step by adopting a centrifugal screening method to obtain a single-layer MXene, wherein the specific steps are as follows: and (3) under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step one for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely the two-dimensional MXene solution.

Step three, preparing the nano flower-shaped CuS: a one-step hydrothermal method is adopted, and specifically comprises the following steps: 0.1-5 g of copper chloride dihydrate (CuCl) is added₂·H₂O) and 0.1 to 5g of thiourea (CH)₄N₂S) dissolving in 10-30 ml of deionized water, then slowly dripping thiourea into the copper chloride solution, and continuously magnetically stirring for 10-40 min to uniformly mix to obtain the precursor. And transferring the prepared precursor solution into a polytetrafluoroethylene hydrothermal reaction kettle, and reacting for 3-10 h at 100-200 ℃. And after the reaction is completed and the reaction product is cooled to room temperature, repeatedly washing the reaction product by using deionized water and absolute ethyl alcohol, drying the reaction product at 40-80 ℃, and grinding the reaction product to obtain the powdery nano flower-shaped CuS (shown in figure 2).

Preparing a flexible self-supporting MXene/CuS-5 film electrode material: preparing a conductive film by adopting an LBL suction filtration method, which specifically comprises the following steps: and (3) carrying out suction filtration treatment on the MXene solution prepared in the second step to obtain a thin layer of clay-like MXene. Dispersing the nano flower-shaped CuS prepared in the third step in deionized water, performing ultrasonic treatment to obtain a uniformly dispersed nano flower-shaped CuS solution, continuing to perform suction filtration to enable the CuS to be negative on an MXene layer, and then continuing to add the MXene solution to obtain MXene-CuS-MXene with a sandwich structure (wherein the content of the nano flower-shaped CuS is 5 wt%). Repeating the steps for 1-5 times, and drying to obtain the flexible MXene/CuS-5 conductive film with the thickness of 2.7 microns.

Step five, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol (PVA) into 10-100 ml of deionized water under continuous stirring, and then slowly dropwise adding 1-10 ml of concentrated sulfuric acid (H) into the solution₂SO₄) And stirring for 1-10 min to disperse the mixture uniformly. And (3) placing the beaker filled with the mixed solution on a magnetic stirrer, starting heating, and observing that the solution becomes transparent when the temperature is raised to 50-100 ℃. When the transparent liquid is poured into a culture dish prepared in advance, the transparent liquid is frozen at the temperature of minus 5 to 20 ℃ for 1 to 3 hours and then taken outDrying at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte.

Step six, assembling the flexible self-supporting MXene/CuS-5 super capacitor: cutting two pieces of 1-5 x (1-5) cm²The MXene/CuS-5 conductive film prepared in the fourth step is used as an electrode material, and the PVA-H prepared in the fifth step and the size of the electrode material are cut₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene/CuS-5 supercapacitor.

Seventhly, testing the specific capacitance of the flexible self-supporting MXene/CuS-5 super capacitor: and (3) performing an electrochemical test on the specific capacitance of the flexible self-supporting MXene/CuS-5 supercapacitor in the sixth step at different scanning speeds by adopting a cyclic voltammetry (CV test). When the content of CuS is 5 wt%, the specific capacity can reach 407.98F/cm³As shown in fig. 6.

Example 3

Preparation of flexible self-supporting MXene/CuS-15 (the content of CuS is 15 wt%) supercapacitor electrode material and research on electrochemical properties of supercapacitor electrode material

Preparing accordion MXene: etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method specifically comprises the following steps: measuring 2-15 ml of concentrated hydrochloric acid and 1-10 ml of deionized water, slowly adding the concentrated hydrochloric acid into a container filled with the deionized water, then weighing 0.1-5 g of LiF powder, adding the LiF powder into the diluted hydrochloric acid, and after LiF is completely dissolved, then adding 0.1-3 g of MAX-phase ceramic powder Ti₃AlC₂The addition was slow. And (3) putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, and collecting a product after reacting for 10-30 h. Washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing the product with deionized water until the pH value is 6-7 to finally obtain the dark green MXene solution.

Step two, preparing a single-layer or few-layer MXene material: processing the accordion-shaped MXene prepared in the first step by adopting a centrifugal screening method to obtain a single-layer MXene, wherein the specific steps are as follows: and (3) under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step one for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely the two-dimensional MXene solution.

Step three, preparing the nano flower-shaped CuS: a one-step hydrothermal method is adopted, and specifically comprises the following steps: 0.1-5 g of copper chloride dihydrate (CuCl) is added₂·H₂O) and 0.1 to 5g of thiourea (CH)₄N₂S) dissolving in 10-30 ml of deionized water, then slowly dripping thiourea into the copper chloride solution, and continuously magnetically stirring for 10-40 min to uniformly mix to obtain the precursor. And transferring the prepared precursor solution into a polytetrafluoroethylene hydrothermal reaction kettle, and reacting for 3-10 h at 100-200 ℃. And after the reaction is completed and the reaction product is cooled to room temperature, repeatedly washing the reaction product by using deionized water and absolute ethyl alcohol, drying the reaction product at 40-80 ℃, and grinding the reaction product to obtain the powdery nano flower-shaped CuS (shown in figure 2).

Step four, preparing the MXene/CuS-15 conductive film electrode material: preparing a conductive film by adopting an LBL suction filtration method, which specifically comprises the following steps: and (3) carrying out suction filtration treatment on the MXene solution prepared in the second step to obtain a thin layer of clay-like MXene. Dispersing the nano flower-shaped CuS prepared in the third step in deionized water, performing ultrasonic treatment to obtain a uniformly dispersed nano flower-shaped CuS solution, continuing to perform suction filtration to enable the CuS to be negative on an MXene layer, and then continuing to add the MXene solution to obtain MXene-CuS-MXene with a sandwich structure (wherein the content of the nano flower-shaped CuS is 15 wt%). Repeating the steps for 1-5 times, and drying to obtain the flexible MXene/CuS-15 conductive film electrode material with the thickness of 5 microns. SEM and macro photographs of the electrode cross section are shown in fig. 3 and 4, respectively.

Step five, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol (PVA) into 10-100 ml of deionized water under continuous stirring, and then slowly dropwise adding 1-10 ml of concentrated sulfuric acid (H) into the solution₂SO₄) And stirring for 1-10 min to disperse the mixture uniformly. And (3) placing the beaker filled with the mixed solution on a magnetic stirrer, starting heating, and observing that the solution becomes transparent when the temperature is raised to 50-100 ℃. When the transparent liquid is poured into a culture dish prepared in advance, freezing the transparent liquid for 1 to 3 hours at the temperature of between 5 ℃ below zero and 20 DEG CTaking out, and airing at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte.

Step six, assembling the flexible self-supporting MXene/CuS-15 super capacitor: cutting two pieces of 1-5 x (1-5) cm²The MXene/CuS-15 conductive film prepared in the fourth step is used as an electrode material, and the PVA-H prepared in the fifth step and the size of the electrode material are cut₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene/CuS-15 supercapacitor.

Seventhly, testing the specific capacitance of the flexible self-supporting MXene/CuS-15 super capacitor: and (3) performing an electrochemical test on the specific capacitance of the flexible self-supporting MXene/CuS-15 supercapacitor in the sixth step at different scanning speeds by adopting a cyclic voltammetry (CV test). The specific capacity of the MXene/CuS-15 super capacitor changes along with the change of the scanning speed, when the scanning speed is 5mV/s and the CuS content is 15 wt%, the specific capacity reaches the maximum, and the ratio can reach 967.09F/cm³(as shown in fig. 5 and 6).

Example 4

Preparation of flexible self-supporting MXene/CuS-20 (the content of CuS is 20 wt%) supercapacitor electrode material and research on electrochemical properties of supercapacitor electrode material

Preparing accordion MXene: etching Ti by using LiF and HCl mixed solution₃AlC₂The preparation method specifically comprises the following steps: measuring 2-15 ml of concentrated hydrochloric acid and 1-10 ml of deionized water, slowly adding the concentrated hydrochloric acid into a container filled with the deionized water, then weighing 0.1-5 g of LiF powder, adding the LiF powder into the diluted hydrochloric acid, and after LiF is completely dissolved, then adding 0.1-3 g of MAX-phase ceramic powder Ti₃AlC₂The addition was slow. And (3) putting the container on a magnetic stirrer, adjusting the temperature to 20-50 ℃, adjusting the rotating speed to 100-300 r/min, and collecting a product after reacting for 10-30 h. Washing with concentrated hydrochloric acid for 5-10 times, and repeatedly washing the product with deionized water until the pH value is 6-7 to finally obtain the dark green MXene solution.

Step two, preparing a single-layer or few-layer MXene material: processing the accordion-shaped MXene prepared in the first step by adopting a centrifugal screening method to obtain a single-layer MXene, wherein the specific steps are as follows: and (3) under the condition that the ultrasonic power is 50-250W, carrying out ultrasonic treatment on the solution obtained in the step one for 5-50 min by using an ultrasonic cell crusher, then centrifuging the solution for 10-50 min under the condition that the rotating speed is 1000-8000 r/min, and collecting the centrifuged supernatant, namely the two-dimensional MXene solution.

Step three, preparing the nano flower-shaped CuS: a one-step hydrothermal method is adopted, and specifically comprises the following steps: 0.1-5 g of copper chloride dihydrate (CuCl) is added₂·H₂O) and 0.1 to 5g of thiourea (CH)₄N₂S) dissolving in 10-30 ml of deionized water, then slowly dripping thiourea into the copper chloride solution, and continuously magnetically stirring for 10-40 min to uniformly mix to obtain the precursor. And transferring the prepared precursor solution into a polytetrafluoroethylene hydrothermal reaction kettle, and reacting for 3-10 h at 100-200 ℃. And after the reaction is completed and the reaction product is cooled to room temperature, repeatedly washing the reaction product by using deionized water and absolute ethyl alcohol, drying the reaction product at 40-80 ℃, and grinding the reaction product to obtain the powdery nano flower-shaped CuS (shown in figure 2).

Step four, preparing the MXene/CuS-20 conductive film electrode material: preparing a conductive film by adopting an LBL suction filtration method, which specifically comprises the following steps: and (3) carrying out suction filtration treatment on the MXene solution prepared in the second step to obtain a thin layer of clay-like MXene. Dispersing the nano flower-shaped CuS prepared in the third step in deionized water, performing ultrasonic treatment to obtain a uniformly dispersed nano flower-shaped CuS solution, continuing to perform suction filtration to enable the CuS to be negative on an MXene layer, and then continuing to add the MXene solution to obtain MXene-CuS-MXene with a sandwich structure (wherein the content of the nano flower-shaped CuS is 20 wt%). Repeating the steps for 1-5 times, and drying to obtain the flexible MXene/CuS-20 conductive film.

Step five, PVA-H₂SO₄Preparation of gel electrolyte: slowly adding 1-10 g of polyvinyl alcohol (PVA) into 10-100 ml of deionized water under continuous stirring, and then slowly dropwise adding 1-10 ml of concentrated sulfuric acid (H) into the solution₂SO₄) And stirring for 1-10 min to disperse the mixture uniformly. And (3) placing the beaker filled with the mixed solution on a magnetic stirrer, starting heating, and observing that the solution becomes transparent when the temperature is raised to 50-100 ℃. When the transparent liquid is poured into a culture dish prepared in advanceFreezing at-5-20 ℃ for 1-3H, taking out, and airing at indoor temperature to obtain PVA-H₂SO₄A gel electrolyte.

Step six, assembling the flexible self-supporting MXene/CuS-20 super capacitor: cutting two pieces of 1-5 x (1-5) cm²The MXene/CuS-20 conductive film prepared in the fourth step is used as an electrode material, and the PVA-H prepared in the fifth step and with the same size as the electrode material are cut₂SO₄The gel electrolyte is used as a solid electrolyte, and the positive electrode material and the negative electrode material are adhered to two sides of the gel electrolyte to obtain the flexible self-supporting symmetrical MXene/CuS-20 supercapacitor.

Seventhly, testing the specific capacitance of the flexible self-supporting MXene/CuS-20 super capacitor: and (3) performing an electrochemical test on the specific capacitance of the flexible self-supporting MXene/CuS-20 supercapacitor in the sixth step at different scanning speeds by adopting a cyclic voltammetry (CV test). When the content of CuS is 5 wt%, the specific capacity is 971.30F/cm³As shown in fig. 6.