Preparation Method and Application of MXene Solid-State Potassium-Ion Supercapacitor Electrode Material with Long Endurance and Fast Charging

Abstract

Preparation method and application of an MXene solid potassium ion supercapacitor electrode material with long endurance and fast charging. Put pure titanium powder, aluminum powder and graphite powder into a vacuum hot pressing sintering furnace, and perform hot pressing sintering to obtain MAX phase Ti3AlC2. Add the MAX phase Ti3AlC2 to a mixed solution of H2SO4 and NH4F, carry out constant temperature magnetic stirring in a constant temperature water bath at 80 °C, after ultrasonic stratification in an ultrasonic wave at room temperature for 1 h, carry out suction filtration, centrifugal cleaning and suction filtration, and vacuum drying to obtain an MXene solid potassium ion supercapacitor electrode material with long endurance and fast charging. The advantages are: simple process, mild conditions, preparing an MXene electrode material with high crystallinity and large spacing, improving the diffusion efficiency of potassium ions on the contact end face and the transfer rate of internal electrons, greatly improving the energy density and rate performance of MXene in solid potassium ion supercapacitors, and having the characteristics of long endurance and fast charging.

Description

Technical Field

[0001] The present invention belongs to the field of solid-state potassium-ion supercapacitors, and particularly relates to a preparation method and application of an electrode material for a long-endurance and fast-charging MXene (SN-Ti3C2) solid-state potassium-ion supercapacitor. Background Art

[0002] Potassium-ion supercapacitors can be used as auxiliary power sources for electric vehicles and form a hybrid power system with batteries. Due to their high power density and fast charge-discharge characteristics, they can provide a large amount of energy for electric vehicles in a short time to meet high-power requirements such as acceleration and climbing. However, aqueous potassium-ion supercapacitors are limited in their wide application due to problems such as a low working voltage window and safety hazards caused by dendrites. Solid-state potassium-ion supercapacitors support a higher voltage window and have good safety, which is one of the future development directions. However, due to the large ionic radius of potassium ions, repeated insertion leads to the destruction of the electrode material structure, a sharp drop in the energy density, and problems such as a large interfacial resistance and low ionic conductivity at the contact surface between the solid electrolyte and the electrode material, which seriously affect the energy density and rate performance of solid-state potassium-ion supercapacitors. Therefore, it is necessary to develop new electrode materials to improve related problems.

[0003] Due to its two-dimensional structure similar to carbon materials, controllable layer structure, high specific surface area, rich controllable surface functional groups, excellent electrical conductivity, and good chemical stability, MXene materials are predicted to be a new generation of energy storage materials and an ideal alternative to carbon electrodes. CN 117945402 A discloses a "preparation method of carbon vacancy defect multi-layer hexagonal hole MXene material for aqueous potassium ion supercapacitor". In this method, dehydrogenated titanium powder, pure aluminum powder, and modified spherical graphite powder are placed in a vacuum hot-pressing sintering furnace. After hot-pressing sintering in the vacuum hot-pressing sintering furnace with argon as the protective atmosphere, it is cooled with liquid nitrogen to obtain MAX phase Ti3AlC2 with hexagonal carbon vacancies; microwave-assisted etching is used to prepare hexagonal hole MXene to obtain a multi-layer hexagonal hole MXene negative electrode material. The advantages are that the prepared multi-layer hexagonal hole MXene directly captures potassium ions with a large radius and its own volume does not undergo serious deformation. Moreover, the mass specific capacity of the aqueous potassium ion supercapacitor is greatly improved, and it has the characteristics of small attenuation of the mass specific capacity during long-cycle charge and discharge. However, the MXene material prepared by the HF and HCl plus fluoride liquid phase method in this method is etched to form a multi-layer hexagonal hole MXene material. The specific surface area of MXene can be increased through the structure of the hexagonal holes, providing more active sites for the storage of potassium ions in the electrolyte. However, the layer spacing of this material is tight and the crystal structure is incomplete. The tight layer spacing is not conducive to the insertion and extraction of large-radius potassium ions, and the incomplete crystal structure is not conducive to ion diffusion and electron transfer; when used in a solid-state potassium ion supercapacitor, it severely limits the improvement of the energy density and rate performance of MXene in the solid-state potassium ion supercapacitor. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method and application of a long-endurance fast-charging MXene (SN-Ti3C2) solid-state potassium ion supercapacitor electrode material. The preparation process flow is simple. The prepared MXene (SN-Ti3C2) solid-state potassium ion supercapacitor electrode material has good crystallinity and layer spacing, and can be used as an electrode material for a solid-state potassium ion supercapacitor, so that the solid-state potassium ion supercapacitor has a large voltage window, high energy density, and excellent rate performance.

[0005] The technical solution of the present invention is as follows:

[0006] A preparation method of a long-endurance fast-charging MXene solid-state potassium ion supercapacitor electrode material, the specific steps are as follows:

[0007] (1) Preparation of MAX phase Ti3AlC2

[0008] Put pure titanium powder, aluminum powder, and ball-milled spherical graphite powder into a vacuum hot-pressing sintering furnace according to a molar ratio of 3.1:1.12:1.35. Conduct hot-pressing sintering in the vacuum hot-pressing sintering furnace with argon as the protective gas. The sintering temperature is 1500 °C, the pressure of the press head of the vacuum hot-pressing sintering furnace is set to 15 T, and the hot-pressing sintering time is 5 h; after the hot-pressing sintering is completed, cool it with the furnace to obtain the MAX phase Ti3AlC2;

[0009] (2) Preparation of long-endurance fast-charging MXene (SN-Ti3C2) electrode material

[0010] According to every 1 g of MAX phase Ti3AlC2, add 36 mL of the mixed solution of H2SO4 and NH4F. Conduct constant-temperature magnetic stirring in a constant-temperature water bath at 80 °C. Add the MAX phase Ti3AlC2 to the mixed solution of H2SO4 and NH4F. The molar ratio of H2SO4 to NH4F is 2:1. Seal it and conduct constant-temperature stirring at 80 °C for 6 h. After ultrasonic stratification at room temperature for 1 h, conduct suction filtration. Wash the filter cake by centrifugation with deionized water, conduct suction filtration, and dry it in a vacuum drying oven under vacuum to obtain the long-endurance fast-charging MXene (SN-Ti3C2) solid-state potassium ion supercapacitor electrode material.

[0011] Further, the power of the vacuum hot-pressing sintering furnace is 50 KW.

[0012] Further, the diameter of the effective contact surface of the press head of the vacuum hot-pressing sintering furnace is Φ75 mm.

[0013] Further, the inflation pressure of the argon protective atmosphere is 0.04 MPa.

[0014] Further, the concentration of sulfuric acid used is 3 mol·L -1 .

[0015] Further, the rotation speed of the magnetic stirring is 600 r / min.

[0016] Further, during centrifugal cleaning, the centrifugal speed is 3500 r / min and the centrifugal time is 20 min.

[0017] Application of a long-endurance fast-charging MXene (SN-Ti3C2) solid-state potassium ion supercapacitor electrode material as an electrode material in a solid-state potassium ion supercapacitor.

[0018] Application of a long-endurance fast-charging MXene (SN-Ti3C2) solid-state potassium ion supercapacitor electrode material as a positive and negative electrode material in a solid-state potassium ion supercapacitor.

[0019] Further, the preparation process of the solid-state potassium ion supercapacitor is as follows:

[0020] (1) Preparation of positive and negative electrode sheets

[0021] Mix the prepared long-endurance fast-charging MXene (SN-Ti3C2), acetylene black, and PVDF in a mass ratio of 9:0.5:0.5, grind for 30 min, add NMP solvent dropwise, and stir evenly to form an electrode slurry; evenly coat the electrode slurry on carbon cloth, then dry at 80 °C for 24 h, and cut to obtain the positive and negative electrode sheets of long-endurance fast-charging MXene.

[0022] (2) Preparation of potassium-ion solid electrolyte

[0023] Weigh KCl, K2S, Sb2S3, and elemental sulfur in a molar ratio of 1.1:3:1:2, and then mix and grind them; then put them into an alumina corundum crucible, place the crucible in a vacuum sintering furnace, and sinter at a constant temperature of 550 °C for 12 h. Subsequently, take it out after cooling with the furnace and grind it into powder to obtain the K3SbS3Cl potassium-ion solid electrolyte.

[0024] (3) Assembly of solid-state potassium-ion supercapacitor

[0025] Sequentially load and assemble into a symmetric solid-state potassium-ion supercapacitor in the order of the positive electrode sheet of long-endurance fast-charging MXene, the K3SbS3Cl potassium-ion solid electrolyte, and the negative electrode sheet of long-endurance fast-charging MXene.

[0026] Advantages of the present invention:

[0027] (1) The present invention prepares a high-crystallinity and large-spacing MXene (SN-Ti3C2) electrode material by using a mild liquid-phase etching method of H2SO4 plus NH4F; compared with the HF and HCl methods, the high crystallinity endows the MXene (SN-Ti3C2) electrode material with a relatively complete structure, increasing its surface area; this increases the number of active sites, providing favorable conditions for the adsorption of potassium ions; secondly, the high crystallinity makes the MXene (SN-Ti3C2) electrode material have fewer defects, reducing the targets of attack by oxygen and water molecules, improving the antioxidant ability of the MXene (SN-Ti3C2) electrode material and enhancing the cyclic stability performance of electrochemistry; finally, the large-spacing MXene (SN-Ti3C2) electrode material is conducive to the full contact of the electrolyte, realizing the insertion of a high number of potassium ions, and at the same time alleviating the problem of structural damage caused by the insertion and extraction of large-diameter potassium ions; the high-crystallinity and large-spacing MXene (SN-Ti3C2) electrode material has a complete structure, fewer defects and a large interlayer spacing; this increases the contact area between the electrolyte and the electrode material, improves the diffusion efficiency of potassium ions at the contact end face and the transfer rate of internal electrons, greatly improving the energy density and rate performance of MXene in solid-state potassium-ion supercapacitors, and having the characteristics of long endurance and fast charging.

[0028] (2) The symmetric solid-state potassium-ion supercapacitor assembled by the present invention realizes good cyclic stability under a relatively large voltage window; the prepared solid electrolyte of sulfide-based ion conductor avoids the generation of dendrites and has good thermal stability; at the same time, it has a high ionic conductivity, improving the diffusion efficiency of potassium ions in the electrolyte and enhancing the rate performance and safety performance; this enables the solid-state potassium-ion supercapacitor with a high-crystallinity and large-spacing MXene (SN-Ti3C2) prepared by the H2SO4 method as the electrode sheet to have a broad application space. Description of the Drawings

[0029] Figure 1 are the XRD diagrams of HF-Ti3C2, HN-Ti3C2 and SN-Ti3C2 of the present invention (corresponding to Example 1, Comparative Example 1 and Comparative Example 2);

[0030] Figure 2 are the EIS diagrams of HF-Ti3C2, HN-Ti3C2 and SN-Ti3C2 of the present invention (corresponding to Example 1, Comparative Example 1 and Comparative Example 2);

[0031] Figure 3 is the SEM diagram of MXene (SN-Ti3C2) of the present invention (corresponding to Example 1);

[0032] Figure 4It is the GCD curve graph of the MXene (SN-Ti3C2) solid potassium ion supercapacitor of the present invention (corresponding to Example 1);

[0033] Figure 5 It is the SEM image of MXene (HF-Ti3C2) prepared by HF etching of the present invention (corresponding to Comparative Example 1);

[0034] Figure 6 It is the GCD curve graph of the MXene (HF-Ti3C2) solid potassium ion supercapacitor of the present invention (corresponding to Comparative Example 1);

[0035] Figure 7 It is the SEM image of MXene (HN-Ti3C2) prepared by HCl plus NH4F of the present invention (corresponding to Comparative Example 2);

[0036] Figure 8 It is the GCD curve graph of the MXene (HN-Ti3C2) solid potassium ion supercapacitor of the present invention (corresponding to Comparative Example 2). Detailed implementation manners

[0037] Example 1

[0038] 1). Preparation of MAX phase Ti3AlC2

[0039] Put pure titanium powder, aluminum powder and ball-milled spherical graphite powder into a vacuum hot pressing sintering furnace according to a molar ratio of 3.1:1.12:1.35, and carry out hot pressing sintering in the vacuum hot pressing sintering furnace with argon as the protective gas. The inflation pressure of the argon protective atmosphere is 0.04 MPa, the power of the vacuum hot pressing sintering furnace is 50 KW, the diameter of the effective contact surface of the pressure head is Φ75 mm, the sintering temperature is 1500 °C, the pressure of the pressure head of the vacuum hot pressing sintering furnace is set to 15 T, and the hot pressing sintering time is 5 h; after the hot pressing sintering is completed, cool with the furnace to obtain MAX phase Ti3AlC2;

[0040] 2). Preparation of long-endurance and fast-charging MXene (SN-Ti3C2) electrode material

[0041] ① Weigh 1 g of the MAX phase Ti3AlC2 prepared in step 1) for standby;

[0042] ② Prepare an etching solution of H2SO4—NH4F, the volume of the mixed solution is 36 mL, and the molar ratio of H2SO4 to NH4F is 2:1;

[0043] First step: Prepare 36 mL of 3 mol·L -1 H2SO4 solution;

[0044] Step 2: Weigh 2 g of NH4F, pour into 36 mL of H2SO4 solution, stir on a stirrer at 450 r / min for 10 min until NH4F is completely dissolved;

[0045] ③ Pour 1g of MAX phase Ti3AlC2 prepared in step 1) into 36mL H2SO4-NH4F etching solution prepared in step 2)② within 5 minutes, seal, and perform constant temperature magnetic stirring in a constant temperature water bath for 6 hours, temperature: 80°C, speed: 600r / min; after ultrasonic stratification at room temperature for 1 hour, filter to remove H2SO4-NH4F etching solution; finally, add 30mL of deionized water and centrifuge at a speed of 3500r / min for 20 minutes to clean and remove impurities, and finally filter again and dry in a vacuum drying oven for 8 hours to obtain a long-life fast-charging MXene (SN-Ti3C2) electrode material;

[0046] 3). Preparation of solid-state potassium ion supercapacitor

[0047] (1) Preparation of positive and negative electrode sheets

[0048] The prepared long-life fast-charging MXene (SN-Ti3C2) electrode material, acetylene black and PVDF were mixed in a mass ratio of 9:0.5:0.5, then ground in an agate mortar for 30 minutes, NMP solvent was added dropwise, and stirred evenly to form an electrode slurry. The electrode slurry was evenly coated on the carbon cloth after ultrasonic cleaning and drying, and dried at 80°C for 24 hours, and the positive and negative electrode sheets of the long-life fast-charging MXene (SN-Ti3C2) were cut out to be 8 cm × 5 cm;

[0049] (2) Preparation of potassium ion (K3SbS3Cl) solid electrolyte

[0050] Weigh KCl, K2S, Sb2S3, and S in a molar ratio of 1.1:3:1:2, mix and grind; then put them into an alumina corundum crucible, put the crucible into a vacuum sintering furnace, and sinter at a constant temperature of 550°C for 12 hours. Then, take them out of the furnace after cooling, grind them into powder, and obtain a potassium ion (K3SbS3Cl) solid electrolyte for standby use;

[0051] (3) Assembly of solid-state potassium ion supercapacitors

[0052] The positive electrode sheet of long-life fast-charging MXene (SN-Ti3C2), the potassium ion (K3SbS3Cl) solid electrolyte and the negative electrode sheet of long-life fast-charging MXene (SN-Ti3C2) are loaded and assembled in sequence to form a symmetrical solid-state potassium ion supercapacitor.

[0053] like Figure 1As shown in the figure, comparing the XRD patterns of HF-Ti3C2, HN-Ti3C2, and SN-Ti3C2, the (002) diffraction peak of SN-Ti3C2 prepared in Example 1 has the strongest intensity, the highest crystallinity, and fewer internal defects, which is beneficial to improving the cycle stability of SN-Ti3C2; the offset of the (002) diffraction peak of SN-Ti3C2 to a smaller angle is the largest, indicating that it has a larger lattice spacing, which is beneficial to the insertion and extraction of large-diameter potassium ions and improves the rate performance. As Figure 2 shown, comparing the EIS diagrams of HF-Ti3C2, HN-Ti3C2, and SN-Ti3C2, SN-Ti3C2 has a smaller arc radius, a lower charge transfer resistance, and a higher slope in the high-frequency region, indicating a higher diffusion efficiency, which shows that SN-Ti3C2 has a higher conductivity and ion diffusion efficiency. As Figure 3 shown, it can be seen from the SEM image of SN-Ti3C2 that SN-Ti3C2 has a larger interlayer distance, which is beneficial to the deep penetration of the electrolyte and improves the energy density. As Figure 4 shown, it can be seen from the GCD curve of SN-Ti3C2 at a high current density that after 1000 charge-discharge cycles, the capacity decays from 492.2 F / g to 275.6 F / g, and the capacity retention rate is 55.6%; the test results show that the large-spacing SN-Ti3C2 with high crystallinity has excellent stability, high rate performance, and high specific capacity in a symmetric solid-state potassium ion supercapacitor.

[0054] Comparative Example 1

[0055] 1). Preparation of MAX phase Ti3AlC2

[0056] Put pure titanium powder, aluminum powder, and ball-milled spherical graphite powder into a vacuum hot-press sintering furnace according to a molar ratio of 3.1:1.12:1.35, and carry out hot-press sintering in the vacuum hot-press sintering furnace with argon as the protective gas. The inflation pressure of the argon protective atmosphere is 0.04 MPa, the power of the vacuum hot-press sintering furnace is 50 KW, the diameter of the effective contact surface of the pressure head is Φ75 mm, the sintering temperature is 1500 °C, the pressure of the pressure head of the vacuum hot-press sintering furnace is set to 15 T, and the hot-press sintering time is 5 h; after the hot-press sintering is completed, it is cooled with the furnace to obtain MAX phase Ti3AlC2;

[0057] 2). Preparation of multi-layer MXene (HF-Ti3C2) electrode material by severe etching with hydrofluoric acid

[0058] ① Weigh 1 g of the MAX phase Ti3AlC2 prepared in step 1) for standby;

[0059] ② Prepare an HF etching solution with a mass concentration of 40%, and the solution volume is 36 mL;

[0060] ③ Place the HF etching solution in a constant temperature water bath for constant temperature magnetic stirring, temperature: 80 °C, rotation speed: 600 r / min.

[0061] Pour 1 g of MAX phase Ti3AlC2 into 36 mL of the HF etching solution prepared in step 2)② within 5 minutes, seal it, and perform constant temperature magnetic stirring in a constant temperature water bath for 6 h, temperature: 80 °C, rotation speed: 600 r / min; after ultrasonic stratification at room temperature for 1 h, perform suction filtration to remove the HF etching solution; finally, add 30 mL of deionized water and centrifuge for 20 min at a rotation speed of 3500 r / min for cleaning and impurity removal, and finally perform suction filtration again, and dry it in a vacuum drying oven for 8 h to obtain a multi-layer MXene (HF-Ti3C2) electrode material;

[0062] 3). Preparation of solid-state potassium ion supercapacitor

[0063] (1) Preparation of positive and negative electrode plates

[0064] Mix the prepared multi-layer MXene (HF-Ti3C2) electrode material, acetylene black and PVDF according to a mass ratio of 9:0.5:0.5, then grind it in an agate mortar for 30 min, add NMP solvent dropwise, stir evenly to form an electrode slurry, uniformly coat the electrode slurry on the carbon cloth after ultrasonic cleaning and drying, dry it at 80 °C for 24 h, and cut out positive and negative electrode plates of multi-layer MXene (HF-Ti3C2) with a size of 8 cm × 5 cm;

[0065] (2) Preparation of potassium ion (K3SbS3Cl) solid electrolyte

[0066] Same as Example 1;

[0067] (3) Assembly of solid-state potassium ion supercapacitor

[0068] Sequentially load and assemble into a symmetric solid-state potassium ion supercapacitor in the order of the positive electrode plate of multi-layer MXene (HF-Ti3C2), the potassium ion (K3SbS3Cl) solid electrolyte prepared in Example 1, and the negative electrode plate of multi-layer MXene (HF-Ti3C2).

[0069] As Figure 1 shown, by comparing the XRD patterns of HF-Ti3C2, HN-Ti3C2 and SN-Ti3C2 in the figure, the (002) diffraction peak intensity of HF-Ti3C2 prepared in Comparative Example 1 is the lowest, the crystallinity is the worst, and there are more internal defects, which is not conducive to improving the cycle stability of HF-Ti3C2; the offset of the (002) diffraction peak of HF-Ti3C2 to a small angle is the smallest, which indicates that it has a smaller lattice spacing, which is not conducive to the insertion and extraction of large-diameter potassium ions and reduces the rate performance. AsFigure 2 As shown in the figure, by comparing the EIS diagrams of HF-Ti3C2, HN-Ti3C2, and SN-Ti3C2, HF-Ti3C2 has the largest arc radius, indicating a relatively large charge transfer resistance, and has a lower slope in the high-frequency region, indicating a lower diffusion efficiency. This shows that HF-Ti3C2 has a lower conductivity and ion diffusion efficiency. As Figure 5 shown in the figure, it can be seen from the SEM image of HF-Ti3C2 that HF-Ti3C2 has a smaller interlayer distance, which is not conducive to the deep penetration of the electrolyte and reduces the energy density. As Figure 6 shown in the figure, it can be seen from the GCD curve of HF-Ti3C2 at a high current density that after 1000 charge-discharge cycles, the capacitance decays from 421.6 F / g to 121.3 F / g, and the capacitance retention rate is 28.2%. The test results show that multilayer HF-Ti3C2 has poor stability and low specific capacitance in symmetric solid-state potassium-ion supercapacitors, which is not ideal for the application of solid-state potassium-ion supercapacitors.

[0070] Comparative Example 2

[0071] 1). Preparation of MAX-phase Ti3AlC2

[0072] Put pure titanium powder, aluminum powder, and ball-milled spherical graphite powder into a vacuum hot-pressing sintering furnace according to a molar ratio of 3.1:1.12:1.35, and perform hot-pressing sintering in the vacuum hot-pressing sintering furnace with argon as the protective gas. The inflation pressure of the argon protective atmosphere is 0.04 MPa, the power of the vacuum hot-pressing sintering furnace is 50 KW, the diameter of the effective contact surface of the pressure head is Φ75 mm, the sintering temperature is 1500 °C, the pressure of the pressure head of the vacuum hot-pressing sintering furnace is set to 15 T, and the hot-pressing sintering time is 5 h; after the hot-pressing sintering is completed, cool it with the furnace to obtain MAX-phase Ti3AlC2;

[0073] 2). Preparation of multilayer MXene (HN-Ti3C2) electrode material

[0074] ① Weigh 1 g of the MAX-phase Ti3AlC2 prepared in step 1) for standby;

[0075] ② Prepare the HCl—NH4F etching solution

[0076] First step: Prepare 36 mL of 9 mol·L -1 HCl solution;

[0077] Second step: Weigh 2 g of NH4F, pour it into 36 mL of HCl solution, and stir it at a speed of 450 r / min on a stirrer for 10 min until NH4F is completely dissolved;

[0078] ③ Slowly pour 1 g of the MAX phase Ti3AlC2 prepared in step 1) into 36 mL of the HCl—NH4F etching solution within 5 minutes, seal it, and carry out constant-temperature magnetic stirring in a constant-temperature water bath for 6 h, with the temperature at 80 °C and the rotation speed at 600 r / min; then, after ultrasonic stratification at room temperature for 1 h, carry out suction filtration to remove the HCl—NH4F etching solution; finally, add 30 mL of deionized water and centrifuge for 20 min at a rotation speed of 3500 r / min to wash and remove impurities, and then carry out suction filtration again. Dry it in a vacuum drying oven for 8 h to obtain the multi-layer MXene (HN-Ti3C2) electrode material.

[0079] 3). Preparation of solid-state potassium-ion supercapacitor

[0080] (1) Preparation of positive and negative electrode plates

[0081] Mix the prepared multi-layer MXene (HN-Ti3C2) electrode material, acetylene black, and PVDF in a mass ratio of 9:0.5:0.5, then grind it in an agate mortar for 30 min, add NMP solvent dropwise, stir evenly to form an electrode slurry, evenly coat the electrode slurry on the carbon cloth after ultrasonic cleaning and drying, and then dry it at 80 °C for 24 h. Cut out the positive and negative electrode plates of multi-layer MXene (HN-Ti3C2) with a size of 8 cm × 5 cm.

[0082] (2) Preparation of potassium-ion (K3SbS3Cl) solid electrolyte

[0083] Same as Example 1;

[0084] (3) Assembly of solid-state potassium-ion supercapacitor

[0085] Sequentially load and assemble into a symmetric solid-state potassium-ion supercapacitor in the order of the positive electrode plate of multi-layer MXene (HN-Ti3C2), the potassium-ion (K3SbS3Cl) solid electrolyte prepared in Example 1, and the negative electrode plate of multi-layer MXene (HN-Ti3C2).

[0086] As Figure 1 shown, by comparing the XRD patterns of HF-Ti3C2, HN-Ti3C2, and SN-Ti3C2 in the figure, the intensity of the (002) diffraction peak of HN-Ti3C2 in Comparative Example 2 is lower than that of SN-Ti3C2 prepared by the sulfuric acid method in Example 1, and there are a certain number of internal defects, which is not conducive to improving the cycle stability of HN-Ti3C2; the offset of the (002) diffraction peak of HN-Ti3C2 towards a small angle is moderate but lower than that of SN-Ti3C2 prepared by the sulfuric acid method in Example 1, indicating that its lattice spacing is smaller than that of the MXene material prepared by the sulfuric acid method of SN-Ti3C2, and the migration rate of large-diameter potassium ions is lower, reducing the rate performance. As Figure 2As shown in the figure, by comparing the EIS diagrams of HF-Ti3C2, HN-Ti3C2, and SN-Ti3C2, HN-Ti3C2 has a larger arc radius, indicating a larger charge transfer resistance, and a lower slope in the high-frequency region, indicating a lower diffusion efficiency. This shows that HN-Ti3C2 has a lower conductivity and ion diffusion efficiency. As Figure 7 shown, it can be seen from the SEM image of HN-Ti3C2 that HN-Ti3C2 has a certain number of relatively large interlayer distances, which is conducive to the deep penetration of the electrolyte and has a high energy density. As Figure 8 shown, it can be seen from the GCD curve of HN-Ti3C2 at a high current density that after 1000 charge-discharge cycles, the capacitance decays from 470.1 F / g to 165.3 F / g, and the capacitance retention rate is 35%. The test results show that multi-layer HN-Ti3C2 has poor stability and a high specific capacitance in a symmetric solid-state potassium-ion supercapacitor, which is not ideal for the application of solid-state potassium-ion supercapacitors.

Claims

1. A method for preparing a long-life fast-charging MXene solid-state potassium ion supercapacitor electrode material, characterized by: The specific steps are as follows: (1) Preparation of MAX phase Ti3AlC2 Pure titanium powder, aluminum powder and ball-milled spherical graphite powder were placed in a vacuum hot-pressing sintering furnace in a molar ratio of 3.1:1.12:1.35, and hot-pressed sintering was performed in the vacuum hot-pressing sintering furnace with argon as the protective gas. The sintering temperature was 1500°C, the pressure head pressure of the vacuum hot-pressing sintering furnace was set to 15T, and the hot-pressing sintering time was 5h. After the hot-pressing sintering was completed, the MAX phase Ti3AlC2 was obtained by cooling the furnace. (2) Preparation of long-life fast-charging MXene electrode materials For every 1g of MAX phase Ti3AlC2, 36mL of a mixture of H2SO4 and NH4F was added, wherein the molar ratio of H2SO4 to NH4F was 2:

1. The mixture was sealed and stirred at a constant temperature of 80°C for 6h. After ultrasonic stratification at room temperature for 1h, the mixture was filtered and the filter cake was centrifugally washed with deionized water, filtered, and vacuum dried to obtain a long-life, fast-charging MXene solid-state potassium ion supercapacitor electrode material.

2. The preparation method of the long-endurance and fast-charging MXene solid potassium ion supercapacitor electrode material according to claim 1, characterized in that: The power of the vacuum hot pressing sintering furnace is 50KW.

3. The preparation method of the long-endurance and fast-charging MXene solid-state potassium ion supercapacitor electrode material according to claim 1, wherein: The diameter of the effective contact surface of the pressure head of the vacuum hot pressing sintering furnace is Φ75mm.

4. The preparation method of the MXene solid potassium ion supercapacitor electrode material with long endurance and fast charging according to claim 1, characterized in that: The filling pressure of the argon protective atmosphere is 0.04MPa.

5. The preparation method of the long-endurance and fast-charging MXene solid potassium ion supercapacitor electrode material according to claim 1, characterized in that: Use a sulfuric acid concentration of 3 mol·L -1 .

6. The preparation method of the long-endurance and fast-charging MXene solid potassium-ion supercapacitor electrode material according to claim 1, characterized in that: The speed of magnetic stirring was 600 r / min.

7. The preparation method of the MXene solid-state potassium ion supercapacitor electrode material with long endurance and fast charging according to claim 1, characterized in that: During centrifugal washing, the centrifugal speed was 3500 r / min and the centrifugal time was 20 min.

8. Use of the supercapacitor electrode material prepared by the preparation method according to claim 1 in a solid-state potassium ion supercapacitor.

9. Use of the supercapacitor electrode material prepared by the preparation method as claimed in claim 1 as positive and negative electrode materials in a solid potassium ion supercapacitor.

10. The use according to claim 8, characterized in that: The preparation process of the solid-state potassium ion supercapacitor is as follows: (1) Preparation of positive and negative electrode sheets The prepared long-life fast-charging MXene, acetylene black and PVDF were mixed in a mass ratio of 9:0.5:0.5, ground for 30 minutes, and NMP solvent was added dropwise, and stirred evenly to form an electrode slurry; the electrode slurry was evenly coated on the carbon cloth, and then dried at 80°C for 24 hours, and cut to obtain the positive and negative electrode sheets of the long-life fast-charging MXene; (2) Preparation of potassium ion solid electrolyte KCl, K2S, Sb2S3, and S were weighed in a molar ratio of 1.1:3:1:2, and then mixed and ground; then put into an alumina corundum crucible, put the crucible into a vacuum sintering furnace, and then sintered at a constant temperature of 550°C for 12 hours; then, taken out with the furnace cooling, ground into powder, and obtained K3SbS3Cl potassium ion solid electrolyte; (3) Assembly of solid-state potassium ion supercapacitors The positive electrode sheet of long-life fast-charging MXene, the K3SbS3Cl potassium ion solid electrolyte and the negative electrode sheet of long-life fast-charging MXene are loaded and assembled in sequence to form a symmetrical solid-state potassium ion supercapacitor.

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