Msa-mxene material and preparation method and application thereof

Abstract

The application discloses an MSA-MXene material and a preparation method and application thereof. The MSA-MXene material is prepared by using a MXene with an F end group as raw material through a Lewis acid molten salt assisted method, the end group, the interlayer spacing and the pore structure are co-adjusted in the molten salt process, the preparation of the high-performance MXene material is realized, and the rolling method can be used to realize the efficient and convenient preparation of the dense MXene electrode. The application provides a train of thought for solving the problem of the large-scale industrialized preparation of the MXene electrode with ultra-high performance in a limited volume.

Description

Technical Field

[0001] This invention belongs to the field of two-dimensional nanomaterials technology, and more specifically relates to an MSA-MXene material, its preparation method, and its application. Background Technology

[0002] In recent years, due to the development of the new energy industry, dense electrodes with high energy density and areal capacitance have attracted much attention, and solving the problems of low conductivity and areal capacitance caused by their thicker dimensions has become increasingly urgent. Two-dimensional MXene materials, due to their unique metal-like structure, possess excellent electrical conductivity, abundant surface active sites, and excellent machine flexibility, and have wide applications in the energy storage field. Currently, the main method for preparing MXene materials is etching with high-concentration hydrofluoric acid or a mixture of fluoride and strong acid. MXene etched using a mixture of fluoride and hydrochloric acid has a small interlayer spacing, and the introduced F end groups have been shown to be detrimental to electrochemical performance. Although the Lewis acid molten salt etching method proposed to address this issue can provide a wider interlayer spacing and Cl end groups with better performance, there are few reports on this process, and the rate performance of MXene decreases above 500°C. Therefore, finding a high-performance MXene preparation process has become a major focus. Summary of the Invention

[0003] To address the current technical challenges, this invention provides a higher-performance MSA-MXene material, a denser MSA-MXene electrode, and a method for preparing the same.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for preparing MSA-MXene material involves reacting MXene powder with F-terminal groups with a ZnCl2 molten salt system via a Lewis acid-molten salt-assisted reaction to prepare MSA-MXene material with Cl-terminal groups.

[0006] Preferably, MXene powder and ZnCl2 are first ground evenly, then NaCl and KCl are added and grinding is continued. The ground mixture is placed in a tube furnace for heat treatment to obtain a crude product. The crude product is added to deionized water and centrifuged multiple times. The precipitate obtained is ultrasonicated and centrifuged to obtain MSA-MXene material.

[0007] Preferably, the molar ratio of MXene, ZnCl2, NaCl to KCl is 1:2.5-3.5:1.5-2.5:1.5-2.5.

[0008] Preferably, the heat treatment process is carried out under an inert atmosphere, with the temperature increased to 400-480°C at a heating rate of 4°C / min and held for 5-6 hours; the centrifugation speed is 3500-4000 r / min and the time is 5-10 min / cycle.

[0009] Preferably, the method for preparing the MXene powder is as follows: the MXene precursor is poured into a mixed solution of fluorine or fluoride and strong acid, placed in an oil bath, and reacted at 50°C for 24 hours. The resulting solution is centrifuged, washed with dilute hydrochloric acid, washed with deionized water, and dried to obtain powdered MXene with terminal F groups.

[0010] 11. The MSA-MXene material prepared by the above method has a two-dimensional layered transition metal carbide structure with the structural formula Ti3C2T. x Among them, the surface functional group T x The material contains surface-capped end groups -Cl and -F, with chlorine comprising 1.5–1.6% and fluorine comprising 17–17.1% of the material; the material also contains intercalated solvent metal cations Zn. 2+ Na + and K + The interlayer spacing ranges from It also has a porous structure on its surface.

[0011] The present invention also provides the application of the above-mentioned MSA-MXene material in the fields of conductive materials or energy storage materials.

[0012] A method for preparing an MSA-MXene electrode involves using the aforementioned MSA-MXene material via a rolling method. Specifically, the MSA-MXene material is uniformly rolled onto a PET film, followed by freeze-drying.

[0013] Preferably, the product is rolled multiple times with rollers and then freeze-dried in a refrigerator at a temperature of 2–10°C for 5–7 hours.

[0014] The materials and preparation method provided by this invention have the following advantages compared with the prior art:

[0015] 1. MSA-MXene materials prepared using the Lewis acid molten salt assisted method allow for the co-tuning of end groups, interlayer spacing, and porosity, significantly improving their performance. Compared to single LiF+HCl etching, replacing the less conductive F end groups with superior Cl end groups, and further enhancing performance through heat treatment and the superior conductivity of LiF+HCl during the molten salt process, significantly improves the material's properties. + Zn, a solvent metal cation with a larger radius 2+The combined effect of the embedded MXene layers expands the interlayer spacing, which is beneficial for increasing the contact area between electrolyte ions and the material, as well as the transport and exchange of electrolyte ions. Simultaneously, a porous structure is formed, resulting in lower electron transfer resistance and faster ion diffusion rates, thus improving the kinetic performance of MXene. Compared to the single Lewis acid molten salt etching method, this method avoids the damage to MXene material properties caused by high temperatures of 500℃, improving the rate performance and cycle stability of MXene. Overall, this method exhibits a "1+1>2" effect compared to single LiF+HCl etching and Lewis acid molten salt etching, providing some inspiration for the current preparation of high-performance MXene materials.

[0016] 2. The dense MSA-MXene electrode prepared by the rolling method offers advantages over the commonly used method of filtration to produce films of limited size. It is more convenient and efficient, enabling the fabrication of large-area, low-cost dense MSA-MXene electrodes. Electrodes prepared using this method require no additional current collectors, binders, or conductive agents. Furthermore, during the rolling process, the compression effect shortens the distance between different MXene molecules at the microscopic level, resulting in a tightly packed MXene cluster. This further shortens the transport of electrolyte ions, contributing to overall electrode performance. This method also provides strong inspiration for the large-scale industrial fabrication of electrodes.

[0017] 3. The obtained dense MSA-MXene electrode still exhibits considerable mass specific capacitance and excellent areal specific capacitance under high loading, which provides a good solution to the problem that many current MXene materials have good specific capacitance under low loading but low specific capacitance under high loading. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 The SEM image of MSA-MXene prepared in Example 1 of this invention shows an accordion-like structure, proving the successful preparation of MXene. Furthermore, the presence of a certain amount of pores on its surface demonstrates that this method can construct a pore structure of a specific size.

[0020] Figure 2The surface density of the active material prepared according to this invention is 9.9 mg / cm³. 2 ,

[0021] 16.97 mg / cm 2 24.05 mg / cm 2 and 45.26 mg / cm 2 A comparison of the areal capacitance and mass capacitance curves of the MSA-MXene electrode at different scan rates.

[0022] Figure 3 The XRD patterns of MSA-MXene, MS-MXene, and A-MXene prepared for this invention show that MSA-MXene has the smallest (002) characteristic peak angle, which means it has the largest interlayer spacing.

[0023] Figure 4 The figure shows the XPS spectra of MSA-MXene and A-MXene prepared in this invention. In comparison, MSA-MXene has a characteristic peak of Cl element and a weaker characteristic peak of F element, indicating that Cl element has successfully substituted F element.

[0024] Figure 5 The MSA-MXene prepared for this invention has the same loading capacity (9.9 mg / cm³) as MS-MXene and A-MXene. 2 Comparison of cyclic voltammetry (CV) curves at a scan rate of 2 mV / s.

[0025] Figure 6 The figure shows MSA-MXene prepared according to the present invention, along with MS-MXene and A-MXene, at the same loading amount of 9.9 mg / cm³. 2 A comparison of the constant current charge-discharge (GCD) curves at a sweep rate of 2 mV / s.

[0026] Figure 7 The MSA-MXene prepared for this invention has the same loading capacity (9.9 mg / cm³) as MS-MXene and A-MXene. 2 A comparison of area capacitance and mass capacitance curves at different scanning speeds.

[0027] Figure 8 The surface density of the active material prepared according to this invention is 9.9 mg / cm³. 2 16.97 mg / cm 2 24.05 mg / cm 2 A comparison of the areal capacitance and mass capacitance curves of the A-MXene electrode at different scan rates. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention presents a Lewis acid molten salt-assisted method for preparing MSA-MXene materials. During the molten salt process, the end groups, interlayer spacing, and pore structure are simultaneously controlled in one step, enabling the preparation of high-performance MXene materials. Furthermore, a rolling method is used to efficiently and conveniently prepare dense MXene electrodes. This invention provides a solution for achieving ultra-high performance MXene electrodes with limited volume, enabling large-scale industrial preparation.

[0030] Example 1:

[0031] First, 30 ml of 12 mol / ml concentrated hydrochloric acid and 10 ml of deionized water were mixed and placed into a reaction vessel. Then, 3.2 g of lithium fluoride was added and the mixture was stirred at 500 rpm for 10 min on a magnetic stirrer. Next, 2 g of the precursor Ti3AlC2 was weighed and placed into the stirred LiF + HCl solution. The mixture was then placed in an oil bath and reacted at 50°C for 24 h to obtain MXene.

[0032] Subsequently, the MXene mixture obtained from the reaction was centrifuged at 3500 rpm for 5 min, the supernatant was discarded, and the precipitate was retained. Then, an appropriate amount of dilute hydrochloric acid was added, and the mixture was centrifuged four times at 3500 rpm for 5 min each time, retaining only the precipitate. Next, an appropriate amount of deionized water was added, and the mixture was centrifuged three times at 3500 rpm for 10 min each time, retaining only the precipitate. Finally, the mixture was dried in a freezer to obtain powdered MXene.

[0033] Next, 1.7 g of MXene, 4.08 g of ZnCl2, 1.17 g of NaCl, and 1.49 g of KCl were weighed according to a molar ratio of 1:3:2:2. The MXene was the powdered MXene prepared in the previous work. First, the weighed MXene and ZnCl2 were poured into a grinding mortar and ground for 10 min. Then, the weighed NaCl and KCl were added to the grinding mortar, and grinding continued for another 10 min. Next, the ground MXene mixture was poured into a corundum boat and placed in a tube furnace under nitrogen purging for 20 min. The mixture was then reacted at 450 °C for 4 h at a heating rate of 4 °C / min. After melting the salt, a molten salt-assisted MXene (MSA-MXene) mixture containing impurities was obtained. An appropriate amount of deionized water was added, and the mixture was centrifuged twice at 3500 r / min for 5 min, retaining only the centrifuged precipitate to remove excess soluble impurity salts. The solution was then sonicated for 4 hours to obtain a final, smaller-scale MSA-MXene solution. It was then centrifuged once at 3500 rpm for 5 minutes to remove a large amount of water, and the centrifuged precipitate was retained.

[0034] The clay-like MSA-MXene in the centrifuge tube is scraped out and spread onto a PET film. The clay-like MSA-MXene is then rolled evenly with a rolling pin to obtain a dense MSA-MXene layer spread on the PET film. The layer is then placed in a refrigerator at 5°C for 6 hours to freeze dry, thus obtaining a dry MSA-MXene film.

[0035] SEM testing of a portion of MSA-MXene powder taken from the film revealed ( Figure 1 The sample exhibits an accordion-like structure, providing preliminary evidence of the successful preparation of MXene. Furthermore, the molten salt treatment did not alter the overall layered structure of MXene, and its large interlayer open structure indicates a significant interlayer spacing. Additionally, the presence of a certain amount of porosity on its surface demonstrates successful porosity control.

[0036] The active material prepared from this sample using the rolling method had a surface density of 9.9 mg / cm³. 2 The MSA-MXene film was then cut to prepare an MSA-MXene electrode, and its electrochemical performance was tested.

[0037] Example 2:

[0038] The MSA-MXene powder prepared in Example 1 was used to prepare an active material with a mass area density of 16.97 mg / cm³ using the rolling method described in Example 1. 2 The MSA-MXene film was then cut to prepare an MSA-MXene electrode, and its electrochemical performance was tested.

[0039] Example 3:

[0040] The MSA-MXene powder prepared in Example 1 was used to prepare an active material with a mass area density of 24.05 mg / cm³ using the rolling method of Example 1. 2 The MSA-MXene film was then cut to prepare an MSA-MXene electrode, and its electrochemical performance was tested.

[0041] Example 4:

[0042] The MSA-MXene powder prepared in Example 1 was used to prepare an active material with a mass area density of 45.26 mg / cm³ using the rolling method of Example 1. 2 The MSA-MXene film was then cut to prepare an MSA-MXene electrode, and its electrochemical performance was tested.

[0043] The comparison of areal capacitance and mass capacitance curves of MSA-MXene electrodes with different loadings prepared in Examples 1-4 at different scan rates is shown in the figure below. Figure 2 As shown, the surface density of the active material is 9.9 mg / cm³. 2 16.97 mg / cm 2 24.05 mg / cm 2 and 45.26 mg / cm 2 The MSA-MXene electrode exhibited specific capacitances of 391 F / g (red line), 250 F / g (blue line), 259 F / g (purple line), and 182 F / g (green line) at a scan rate of 2 mV / s, and a specific capacitance of 45.26 mg / cm³. 2 The MSA-MXene isoprene has an area capacitance of up to 11468 mF / cm². 2 This indicates that the MSA-MXene prepared by this invention exhibits excellent specific capacitance at a mass load of 9.9, which is the commonly used commercial mass load; and high areal capacitance at a mass load of 45.26, which is far beyond the commercial mass load. It can adapt to corresponding mass load requirements.

[0044] Comparative Example 1:

[0045] First, 30 ml of 12 mol / ml concentrated hydrochloric acid and 10 ml of deionized water were mixed and placed into a reaction vessel. Then, 3.2 g of lithium fluoride was added and the mixture was stirred at 500 rpm for 10 min on a magnetic stirrer. Next, 2 g of the precursor Ti3AlC2 was weighed and placed into the stirred LiF + HCl solution. The mixture was then placed in an oil bath and reacted at 50°C for 24 h to obtain MXene.

[0046] Subsequently, the MXene mixture obtained from the reaction was centrifuged at 3500 rpm for 5 min, the supernatant was discarded, and the precipitate was retained. Then, an appropriate amount of dilute hydrochloric acid was added, and the mixture was centrifuged four times at 3500 rpm for 5 min each time, retaining only the precipitate. Next, an appropriate amount of deionized water was added, and the mixture was centrifuged three times at 3500 rpm for 10 min each time, retaining only the precipitate. Finally, the mixture was dried in a freezer to obtain powdered MXene.

[0047] A portion of powdered MXene was sonicated for 2 hours. The resulting acid-etched MXene (AcidMXene, or A-MXene) solution was then freeze-dried in a freeze dryer to obtain dried A-MXene powder. This A-MXene sample was then prepared into an active material with a surface area density of 9.9 mg / cm³ using the rolling method described in Example 1. 2 The A-MXene film was then cut to prepare an A-MXene electrode, and its electrochemical performance was tested.

[0048] Comparative Example 2:

[0049] The A-MXene sample prepared in Comparative Example 1 was processed using the rolling method of Example 1 to obtain an active material with a mass area density of 19.97 mg / cm³. 2 The A-MXene film was then cut to prepare an A-MXene electrode, and its electrochemical performance was tested.

[0050] Comparative Example 3:

[0051] The A-MXene sample prepared in Comparative Example 1 was processed using the rolling method of Example 1 to obtain an active material with a surface area density of 24.05 mg / cm³. 2 The A-MXene film was then cut to prepare an A-MXene electrode, and its electrochemical performance was tested.

[0052] Comparative Example 4:

[0053] First, weigh 1g of precursor Ti3AlC2, 4.08g of ZnCl2, 1.17g of NaCl, and 1.49g of KCl according to a molar ratio of 1:3:2:2. Then, in batches, add the precursors Ti3AlC2 and ZnCl2 to a grinding mortar and grind for 10 minutes. Next, add the remaining NaCl and KCl and grind for another 10 minutes. Then, pour the ground mixture into an alumina boat. Place the alumina boat in a tube furnace and aerate for 20 minutes. Then, raise the temperature to 450℃ at a rate of 4℃ / min and react for 4 hours. Finally, remove the molten salt MXene (Molten Salt MXene, i.e., MS-MXene) mixture by centrifugation at 3500 rpm for 5 minutes to remove soluble impurities.

[0054] After removing impurities, MS-MXene is sonicated for 2 hours. The sonicated MS-MXene solution is then placed in a freeze dryer for freeze drying to obtain dried MS-MXene powder.

[0055] The MS-MXene sample prepared in Comparative Example 4 was processed using the rolling method in Example 1 to achieve an active material surface density of 9.9 mg / cm³. 2 The A-MXene film was then cut to prepare an A-MXene electrode, and its electrochemical performance was tested.

[0056] Structural and electrochemical performance test results of MSA-MXene, MS-MXene, and A-MXene

[0057] 1) XRD characterization analysis was performed on the MSA-MXene, MS-MXene, and A-MXene prepared above. Figure 3 It was found that the 002 characteristic peak of MSA-MXene has a large intensity and a small angle, indicating that its interlayer spacing is large, reaching [a certain level]. This surpasses numerous related reports. Furthermore, comparing the characteristic peaks of the precursor Ti3AlC2 reveals that MSA-MXene exhibits a weaker peak, indicating that this method successfully etched the precursor to obtain MXene. This is further supported by the XPS total spectrum (…). Figure 4 It is not difficult to see that MSA-MXene contains Cl, with a content of 1.52 at.%, and also contains F, with a content of 17.03 at.%. Furthermore, compared with A-MXene, MSA-MXene has an increased chlorine content and a decreased fluorine content.

[0058] 2) The MSA-MXene prepared above has the same loading capacity (9.9 mg / cm³) as MS-MXene and A-MXene. 2 The CV and GCD curves at a scan rate of 2 mV / s are shown below. Figure 5 andFigure 6 As shown, the CV curve of the MSA-MXene electrode is rectangular, and the GCD curve is a symmetrical triangle with no obvious charge / discharge plateau. This indicates that the material's main energy storage comes from pseudocapacitance. The CV curve of A-MXene is rectangular, while the CV curve of MS-MXene is a battery-type curve with a pair of redox peaks.

[0059] 3) Figure 7 The MSA-MXene prepared above was prepared at the same loading level as MS-MXene and A-MXene (9.9 mg / cm³). 2 Comparison of areal capacitance and specific mass capacitance curves at different scan rates. MS-MXene exhibits a specific capacitance of 27 F / g at a scan rate of 2 mV / s. At a scan rate of 2 mV / s, the loading is 9.9 mg / cm³. 2 The specific capacitance of MSA-MXene is 243 F / g. The areal specific capacitance and mass specific capacitance data corresponding to the three curves clearly demonstrate that the MSA-MXene sample prepared in this invention has superior charge storage capacity compared to the other two comparative samples.

[0060] 4) Figure 8 The surface density of the active material prepared according to this invention is 9.9 mg / cm³. 2 16.97 mg / cm 2 24.05 mg / cm 2 A comparison of the areal capacitance and mass capacitance curves of the A-MXene electrode at different scan rates. At a scan rate of 2 mV / s, the loading was 9.9 mg / cm³. 2 19.97 mg / cm 2 24.05 mg / cm 2 The specific capacitances of the A-MXene samples were 243 F / g, 166 F / g, and 164 F / g, respectively. The MSA-MXene samples prepared in this invention exhibit superior charge storage capacity compared to A-MXene under any loading.

[0061] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0062] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method of preparing an MSA-MXene material, characterized in that, The MSA-MXene material is prepared by a Lewis acid molten salt assisted reaction of MXene powder with an F end group and a ZnCl2 molten salt system, and the specific steps are as follows: the MXene powder and ZnCl2 are first ground uniformly, then NaCl and KCl are added and ground, the ground mixture is placed in a tube furnace for heat treatment, and a crude product is obtained; the crude product is added to deionized water and centrifuged for multiple times, and the obtained precipitate is subjected to ultrasonic treatment and centrifugation to obtain the MSA-MXene material; The molar ratio of the MXene, ZnCl2, NaCl and KCl is 1:2.5-3.5:1.5-2.5:1.5-2.5; The heat treatment process is carried out under an inert atmosphere, the temperature is raised to 400-480℃ at a temperature raising speed of 4℃ / min, and the temperature is kept for 3-5h; the centrifugal speed is 3500-4000r / min, and the time is 5-10min / time; The MSA-MXene is a transition metal carbide with a two-dimensional layered structure, and its structural formula is Ti3C2T x , wherein the surface functional group T x includes surface capping groups -Cl and -F, the atomic ratio of chlorine in the material is 1.5-1.6%, and the atomic ratio of fluorine in the material is 17-17.1%; the material has interlayer embedded solvent metal cations Zn 2+ , Na + , and K + , the interlayer spacing ranges from , and the surface has a pore structure.

2. The method of claim 1, wherein the MSA-MXene material is prepared by a process comprising: The preparation method of the MXene powder is as follows: the MXene precursor Ti3AlC2 is poured into a mixed solution of fluoric acid or fluoride and a strong acid, and is placed in an oil bath pot, and is reacted at 50℃ for 24h, the obtained solution is subjected to centrifugation, dilute hydrochloric acid washing, deionized water washing and drying to obtain the powder-like MXene with an end group F.

3. The MSA-MXene material prepared by the preparation method according to any one of claims 1-2.

4. The application of the MSA-MXene material according to claim 3 in the field of conductive materials or energy storage materials.

5. A method of preparing an MSA-MXene electrode, characterized by, The MSA-MXene material according to claim 3 is prepared by a rolling method, specifically, the MSA-MXene material is uniformly rolled on a PET film, and cold freeze drying is completed.

6. The method of claim 5, wherein the MSA-MXene electrode is prepared by, The roller is rolled for multiple times, and then is placed in a refrigerator with a temperature of 3-10℃ for cold freeze drying for 5-7h.

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