CN113675408A

CN113675408A - MoS for high-performance potassium ion battery2/Ti3C2Preparation method of MXene composite material

Info

Publication number: CN113675408A
Application number: CN202111023143.0A
Authority: CN
Inventors: 尹龙卫; 赵瑞正; 王成祥; 赵丹阳; 惠晓斌; 丁明洁
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-09-02
Filing date: 2021-09-01
Publication date: 2021-11-19
Anticipated expiration: 2041-09-01
Also published as: CN112054199A; CN113675408B

Abstract

The invention provides a MoS for a high-performance potassium ion battery₂/Ti₃C₂The preparation method of the MXene composite material comprises the following steps: subjecting a plurality of layers of et-Ti₃C₂Dispersing MXene nano-sheet in intercalation agent solution, reacting at room temperature, centrifuging, washing, and drying to obtain in-Ti₃C₂MXene nanosheets; adding the mixed solution of a molybdenum precursor and a sulfur precursor into in-Ti under the conditions of ultrasound and stirring₃C₂In the MXene nano-sheet dispersion liquid,carrying out high-temperature reaction on the obtained mixed solution; after the reaction is finished, centrifuging, washing and drying to obtain the catalyst. The composite material overcomes the defects of a single material and solves the problem that K is caused by⁺The problems of rapid reversible capacity attenuation and poor cycle stability caused by huge volume expansion and crushing of the electrode in the repeated embedding/separating process are solved, so that the cycle stability and the specific capacity of the potassium ion battery are obviously improved.

Description

MoS for high-performance potassium ion battery2/Ti3C2Preparation method of MXene composite material

Technical Field

The invention relates to a MoS for a high-performance potassium ion battery₂/Ti₃C₂A preparation method of MXene composite material belongs to the technical field of potassium ion batteries.

Background

Currently, despite the successful commercialization of Lithium Ion Batteries (LIBs), future energy demands are still not met due to the high cost and uneven distribution of lithium resources. In recent years, Potassium Ion Batteries (PIBs) have been considered as a promising alternative to LIBs due to their abundant potassium reserves, low cost and their electrochemical properties similar to lithium. Furthermore, K/K⁺Standard redox potential and Na/Na of (-2.93V vs Standard Hydrogen Electrode (SHE))⁺(-2.71Vvs SHE) is relatively low and closer to Li/Li⁺Standard redox potential of (-3.04V vs SHE). In addition, in the electrolyte of Propylene Carbonate (PC) solvent, with

And

compared with, K⁺Minimum Stokes radius of

Further proving K⁺Fast diffusion kinetics in the electrolyte. However, because

Greater than

And

resulting in slow reaction kinetics and large volume expansion in the circulation process, fast capacity attenuation and poor rate capability. In this regard, suitable electrode materials are sought to accommodate rapid K⁺The large volume change during the insertion/extraction process is a major challenge in the development of PIBs.

At present, the transition metal sulfide is an alkali metal ion battery electrode material with great prospect due to large theoretical capacity and low cost, and has attracted wide attention of people at home and abroad. Wherein, molybdenum disulfide (MoS)₂) Has a unique layered structure, an open 2D diffusion path, an interlayer spacing (0.62nm) greater than that of graphite (0.33nm), and is a very promising K⁺The negative electrode material is rapidly inserted/removed. Furthermore, MoS₂Provides a large number of oxidation-reduction sites through multi-electron transfer and has higher theoretical specific capacity (670mAh g)^-1). However, pure MoS₂The electrode is at K⁺The large volume expansion and pulverization during repeated intercalation/deintercalation can lead to problems of rapid capacity fade and poor cycle stability. In addition, its rapid charge/discharge capability is limited due to the inherently low conductivity. To solve this problem, many improvements to MoS have been proposed₂Strategy for electrochemical performance, an effective and straightforward strategy is to take full advantage of the conductive substrate to prevent adjacent MoS₂Agglomeration of the nanoplatelets and buffering of volume changes during cycling. Therefore, a new conductive substrate is explored to realize and reduce the layer MoS₂Controlled surface coupling of nanoplatelets remains a significant challenge.

Among various conductive substrates, Ti₃C₂MXene material has high conductivity (6.76X 10)⁵S m^-1) The interlayer spacing is adjustable, the hydrophilicity is strong, and the like, and the material can be used as a substrate material for efficient electron transportation and enhancement of alkali metal ion batteries and super capacitors. According to calculation, due to Ti₃C₂K of MXene⁺The diffusion barrier (0.103eV) is lower than that of the pristine graphene (0.64eV), so Ti₃C₂MXene negative electrode can realize faster K⁺Transport and higher charge/discharge rates. More importantly, Ti₃C₂The abundant surface functional groups of MXene materials can also act as conductive substrates for nucleation and loading of other active materials. Based on the advantages, the high specific energy few-layer MoS is reasonably designed₂Nanosheet and high power Ti₃C₂MXene composites are very challenging and important for high performance PIBs. About MoS₂The preparation of composites with MXene is also reported in the patent literature. For example, chinese patent document CN107660114A provides a method for preparing a molybdenum disulfide/MXene layered composite wave-absorbing material, which comprises the steps of: mixing the molybdenum disulfide reaction solution with MXene materials, preparing initial powder of the molybdenum disulfide/MXene layered composite material through hydrothermal reaction, washing and drying to obtain the molybdenum disulfide/MXene layered composite wave-absorbing material. The method has complex reaction process, and the prepared composite material is seriously stacked, which is not beneficial to the improvement of the wave absorption performance. Chinese patent document CN109671949A provides a method for preparing an MXene-based flexible composite anode material, which discloses a method for preparing an MXene/transition metal sulfide: mixing metal salt of transition metal element with a sulfur source, adding MXene material and alkaline solution to obtain a mixed solution, and carrying out hydrothermal reaction in a high-pressure reaction kettle to obtain the MXene/transition metal sulfide composite material. MXene prepared by HF etching only has thicker lamella and smaller interlayer spacing, which is not beneficial to the compounding with transition metal sulfide and the improvement of performance.

Currently, existing MoS₂With Ti₃C₂The compounding method of the MXene composite material has the problems of common and complex reaction process and serious stacking of obtained products,difficult to realize MoS₂And Ti₃C₂MXene has synergistic effect. Chinese patent document CN106532015A proposes to use 49% HF for etching Ti₃AlC₂Precursor preparation of accordion-shaped Ti₃C₂MXene cannot fundamentally solve the problem of Ti because the prepared material is not of a few-layer intercalation structure and does not have three-dimensional morphology₃C₂The self-stacking effect of MXene also fails to provide a better path for the transport of ions during electrochemical reaction. Therefore, the high specific energy few-layer MoS is reasonably designed₂Nanosheet and high power Ti₃C₂The MXene material is coupled to obtain high-performance MoS₂/Ti₃C₂MXene composite materials have great challenge and importance for high-performance potassium ion batteries. The invention is therefore proposed.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a MoS for a high-performance potassium ion battery₂/Ti₃C₂A preparation method of MXene composite material. The invention successfully synthesizes the MoS with the 3D interconnection network through the ion exchange and electrostatic adsorption processes₂/Ti₃C₂MXene composite material, few-layer MoS in obtained composite material₂Nano sheet vertically loaded in Ti₃C₂On MXene. MoS of the invention₂/Ti₃C₂MXene composite material incorporating Ti₃C₂MXene structure and few-layer MoS₂The excellent characteristics of the nano-sheet, on one hand, the unique structure can effectively inhibit MoS₂Aggregation and volume change of the nanosheets, thereby improving the electrical conductivity of the composite material; on the other hand, MoS₂And Ti₃C₂The synergistic effect between these two components of MXene can significantly improve battery performance through novel battery capacitance Dual Mode Energy Storage (DMES) behavior. MoS of the invention₂/Ti₃C₂The MXene composite material overcomes the defects of the traditional single material and solves the problem that K is generated⁺Large volume expansion and pulverization of electrodes during repeated intercalation/deintercalation resulting in rapid decay of reversible capacity and poor cycle stabilityThe problem is solved, so that the cycling stability and the specific capacity of the potassium ion battery are obviously improved.

Description of terms:

room temperature: has a well-known meaning, in particular 25. + -. 5 ℃.

The technical scheme of the invention is as follows:

MoS for high-performance potassium ion battery₂/Ti₃C₂The preparation method of the MXene composite material comprises the following steps:

(1) subjecting a plurality of layers of et-Ti₃C₂Dispersing MXene nano-sheet in intercalation agent solution, reacting at room temperature, centrifuging, washing, and drying to obtain in-Ti₃C₂MXene nanosheets;

(2) adding the mixed solution of a molybdenum precursor and a sulfur precursor into in-Ti under the conditions of ultrasound and stirring₃C₂In MXene nanosheet dispersion liquid, carrying out high-temperature reaction on the obtained mixed liquid; after the reaction is finished, centrifuging, washing and drying to obtain MoS₂/Ti₃C₂MXene composite material.

According to the invention, et-Ti as described in step (1)₃C₂The MXene nano-sheet uses HF as etching agent to selectively etch Ti₃AlC₂Obtained, which can be prepared according to the prior art; preferably, said et-Ti₃C₂The preparation method of the MXene nanosheet comprises the following steps:

mixing Ti₃AlC₂Slowly adding the powder into the HF solution for 0.5h, and stirring and reacting for 24h at 35 ℃; repeatedly washing the obtained substance with deionized water, centrifuging and decanting until the pH of the supernatant is 6-7, and freeze-drying the obtained precipitate at-30 ℃ for 24 hours to obtain et-Ti₃C₂MXene nanosheets; the mass fraction of the HF solution is 10-50 wt%, and the volume of the HF solution and Ti are₃AlC₂The mass ratio of the powder is 10-30 mL: 1g of the total weight of the composition.

According to the present invention, preferably, the intercalation agent in step (1) is NaOH, LiOH or KOH; the et-Ti₃C₂The mass ratio of the MXene nano-sheet to the intercalating agent is 1: 0.8-2.4, and the further advantage isSelecting the ratio of 1: 1-2; the intercalation agent can expand Ti₃C₂The interlayer spacing of MXene nano-sheets increases active sites.

According to the invention, the concentration of the intercalation agent solution in the step (1) is preferably 1-3 mol/L.

According to the invention, the reaction time in the step (1) is preferably 5-8 h.

According to the present invention, preferably, the washing in step (1) is 6 times by deionized water; the drying is to freeze-dry the washed product at-30 ℃ for 24 h.

According to the present invention, it is preferable that in-Ti is mentioned in the step (2)₃C₂The concentration of the MXene nanosheet dispersion is 5.0-8.0 mg/mL, and more preferably 6.6-6.7 mg/mL.

According to the present invention, preferably, the molybdenum precursor in the step (2) is sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) or ammonium molybdate ((NH)₄)₂MoO₄)。

According to the present invention, it is preferable that the molybdenum element in the molybdenum precursor in the step (2) is in-Ti₃C₂The mass ratio of the MXene nanosheets is 1: 3-5.

According to the present invention, it is preferred that the sulfur precursor in step (2) is thioacetamide (CH)₃CSNH₂) Or thiourea (NH)₂CSNH₂)。

According to the present invention, it is preferable that elemental sulfur and in-Ti in the sulfur precursor in the step (2)₃C₂The mass ratio of the MXene nanosheets is 1: 2-3.

According to the invention, preferably, the mixed solution of the molybdenum precursor and the sulfur precursor in the step (2) is obtained by dissolving the molybdenum precursor and the sulfur precursor in deionized water, wherein the mass concentration of the molybdenum precursor in the mixed solution is 2-6 mg/mL, and the mass concentration of the sulfur precursor in the mixed solution is 4-8 mg/mL; the mixed solution of the molybdenum precursor and the sulfur precursor is added into the system in a dropwise manner.

According to the invention, the reaction temperature in the step (2) is preferably 180-220 ℃, and the reaction time is 18-36 h.

According to the invention, preferably, the washing in the step (2) is centrifugal washing with water and absolute ethyl alcohol for 4-6 times respectively; the drying is freeze drying for 24-48 h at-30 ℃.

According to the invention, the MoS prepared by the preparation method₂/Ti₃C₂The MXene composite material is used as a negative electrode material and applied to a potassium ion battery, and the application method comprises the following steps:

mixing MoS₂/Ti₃C₂Mixing an MXene composite material, a polyvinylidene fluoride (PVDF) binder and conductive carbon black (super-PLI) according to a mass ratio of 70:15:15, uniformly grinding, adding N-methyl pyrrolidone serving as a solvent, stirring for 12 hours, preparing uniform slurry, uniformly coating the uniform slurry on a copper foil, and performing vacuum drying to obtain a negative electrode material for a potassium ion battery; the mass of the N-methyl pyrrolidone is MoS₂/Ti₃C₂The total mass of the MXene composite material, the polyvinylidene fluoride binder and the conductive carbon black is 2-3 times of that of the MXene composite material.

The invention has the following technical characteristics and beneficial effects:

1. the invention utilizes intercalation agent to let-Ti₃C₂Intercalation treatment is carried out on MXene nano-sheets, and cations of the intercalating agent are inserted into Ti₃C₂T_xInterlamination, meanwhile, the-OH in the intercalation agent can replace the-F surface functional group to obtain in-Ti with larger interlayer spacing₃C₂MXene nano-sheet. Ti with larger interlayer spacing₃C₂The MXene framework provides larger specific surface area and ion exchange sites, is favorable for full contact of electrode materials and electrolyte, and improves the charge transfer efficiency. Then, through ion exchange and electrostatic adsorption processes, the MoS of few layers₂The nano-sheets are uniformly loaded on the surface of the nano-sheet with a 3D interconnection network structure in-Ti₃C₂MXene, thereby exposing more active sites and improving the storage capacity of potassium. The preparation method solves the problem of MoS₂The aggregation and the volume change of the nano-sheets, thereby remarkably improving the cycling stability and the specific capacity of the potassium ion battery.

2. The invention is madePrepared MoS₂/Ti₃C₂In the MXene composite material, the conductive in-Ti is uniformly loaded₃C₂Few-layer MoS on MXene substrate₂The nanoplatelets have enhanced conductivity and reduced volume expansion and aggregation during cycling, resulting in high capacity and stable energy storage. At the same time, in-Ti₃C₂And MoS₂The components have strong Mo-C covalent bonds, so that atom charge polarization is further caused, charge absorption is improved, effective interface electron transfer is realized, the capacitance performance is enhanced, faster and more stable energy storage is ensured, and the method has great significance in preparing the potassium ion battery cathode. The preparation method adopts a specific adding sequence of the molybdenum source and the sulfur source, the molybdenum source and the sulfur source are basically nucleated in the process of stirring in deionized water in the ion exchange process in the early stage, and then the molybdenum source and the sulfur source are electrically conducted in-Ti₃C₂Uniformly growing MXene substrate into MoS₂If the adding sequence of the molybdenum source or the sulfur source is changed, part of the sulfur source or the molybdenum source can excessively change in-Ti₃C₂The chemical property and charge distribution of the MXene surface cannot obtain MoS with uniform appearance and excellent performance₂/Ti₃C₂MXene composite material.

3. The invention uses Ti₃C₂Compared with the traditional carbon materials such as graphene and the like, the MXene nano-sheet is used as a substrate material, and Ti₃C₂MXene has fast ion diffusion capacity, the MoS of the invention₂With Ti₃C₂The coupling mode of MXene materials can greatly improve MoS₂/Ti₃C₂Reversible capacity, cycle life and rate capability of MXene electrodes. Experiments prove that the MoS prepared by the invention₂/Ti₃C₂MXene negative electrode material at 0.1A g^-1After circulating for 200 times under the current density of (2), 360.0mAh g can be provided^-1And at 0.5A g^-1The reversible capacity is 195.5mAh g after 1300 cycles^-1Has long cycle stability, and the attenuation rate of each cycle is only 0.01 percent.

4. The preparation method of the inventionThe novel MoS is successfully prepared by the simple and convenient ion exchange and electrostatic adsorption process₂/Ti₃C₂The MXene composite material can be popularized to the preparation of other composite materials, and plays a certain reference role in widening energy material systems. The invention provides a new idea for developing a high-performance potassium storage anode material with a DMES mechanism. The method has the advantages of simple operation, easily obtained raw materials, low cost and easy large-scale industrialized popularization and application.

Drawings

FIG. 1 is the MoS prepared in example 1₂/Ti₃C₂SEM (a-b) and TEM (c-d) images of MXene composite materials.

FIG. 2 shows in-Ti prepared in example 1₃C₂SEM image of MXene nanosheet.

FIG. 3 is Ti₃AlC₂、et-Ti₃C₂MXene, in-Ti prepared in comparative example 1₃C₂MXene and MoS prepared in example 1₂/Ti₃C₂XRD pattern of MXene composite material.

FIG. 4 shows MoS prepared in example 1₂/Ti₃C₂Mapping map of MXene composite material.

FIG. 5 is a MoS prepared in comparative example 2₂SEM (a) and TEM (b) images of the materials.

FIG. 6 is an in-Ti alloy prepared in comparative example 3₃C₂SEM image of MXene nano-sheet, wherein (a) is in-Ti obtained by low intercalation agent concentration₃C₂SEM image of MXene nano-sheet, wherein (b) is in-Ti obtained by high intercalator concentration₃C₂SEM image of MXene nanosheet.

FIG. 7 is a MoS prepared in comparative example 3₂/Ti₃C₂SEM image of MXene composite material, wherein (a) is MoS obtained by low intercalation agent concentration₂/Ti₃C₂SEM image of MXene composite material, wherein (b) is MoS obtained by high intercalator concentration₂/Ti₃C₂SEM images of MXene composites.

FIG. 8 shows MoS obtained in comparative example 4₂/Ti₃C₂SEM images of MXene composites.

FIG. 9 shows MoS prepared in comparative example 2 of test example 1₂Nanosheets, in-Ti prepared in comparative example 1₃C₂MXene materials and MoS prepared in example 1₂/Ti₃C₂Cycle performance curve of MXene composite.

FIG. 10 shows MoS prepared in example 1 of Experimental example 1₂/Ti₃C₂Long cycle performance curve of MXene composite.

FIG. 11 is a MoS prepared in comparative example 3₂/Ti₃C₂Cycle performance curve of MXene composite.

FIG. 12 is a MoS prepared in comparative example 4₂/Ti₃C₂Cycle performance curve of MXene composite.

Detailed Description

The present invention is further described below with reference to the following drawings and examples, but is not limited thereto.

The raw materials used in the examples are all conventional raw materials unless otherwise specified, and are commercially available; the methods used in the examples are prior art unless otherwise specified.

Example 1

(1) preparation of et-Ti₃C₂MXene nano-sheet

1g of Ti with the grain diameter of less than 38 mu m₃AlC₂Slowly adding the powder into 20mL of HF solution with the mass fraction of 40 wt% for 0.5h to avoid overheating exothermic reaction, and stirring for reaction at 35 ℃ for 24 h; repeatedly washing the obtained substance with deionized water, centrifuging and decanting until the pH of the supernatant is 6-7, and freeze-drying the obtained precipitate at-30 ℃ for 24 hours to obtain et-Ti₃C₂MXene nano-sheet.

(2) Preparation of in-Ti₃C₂MXene nano-sheet

1g of et-Ti₃C₂MXene nanosheets dispersed in 20mL of 1.8mol/L NaOH solution, and the resulting mixture was allowed to stand at room temperatureContinuously stirring and reacting for 6 hours; after the reaction is finished, centrifuging, washing the obtained precipitate for 6 times by using deionized water, and freeze-drying the product obtained by washing at-30 ℃ for 24 hours to obtain in-Ti₃C₂MXene nano-sheet.

(3) Preparation of MoS₂/Ti₃C₂MXene composite material

0.2g of in-Ti prepared in the step (2)₃C₂Dispersing MXene nano-sheets in 30mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain in-Ti₃C₂MXene nanosheet dispersion; then 0.12g of sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) and 0.2g of thioacetamide (CH)₃CSNH₂) Dissolving the molybdenum precursor and the sulfur precursor in 30mL of deionized water, and magnetically stirring to obtain a mixed solution of the molybdenum precursor and the sulfur precursor; under the conditions of ultrasonic and magnetic stirring, dropwise adding the mixed solution of a molybdenum precursor and a sulfur precursor into in-Ti₃C₂Continuously stirring the MXene nanosheet dispersion liquid for 1h, transferring the obtained mixed liquid into a 100mL stainless steel autoclave with a polytetrafluoroethylene lining, and reacting for 24h at 200 ℃; naturally cooling to room temperature, respectively centrifugally washing the obtained black precipitate with deionized water and absolute ethyl alcohol for 5 times, and freeze-drying the washed product at-30 ℃ for 24 hours to obtain MoS₂/Ti₃C₂MXene composite material.

MoS prepared in this example₂/Ti₃C₂SEM and TEM images of MXene composite are shown in FIG. 1, and from FIG. 1, it can be seen that MoS is a few layers₂The nano-sheets are uniformly supported on Ti₃C₂MXene forms a 3D interconnected conductive network structure, thereby exposing more active sites and improving the storage capacity of potassium.

in-Ti prepared in this example₃C₂The SEM image of MXene nanosheets is shown in FIG. 2, and as can be seen from FIG. 2, the obtained in-Ti₃C₂The MXene nano-sheet has an accordion structure with uniform appearance.

MoS prepared in this example₂/Ti₃C₂The XRD pattern of MXene composite material is shown in figure 3. As can be seen from figure 3, this is the materialThe materials prepared in the examples had Ti₃C₂MXene and MoS₂Diffraction peaks common to both and compared to et-Ti₃C₂MXene material, the interlamellar spacing of the obtained composite material is obviously enlarged; as can also be seen in FIG. 3, in-Ti₃C₂Interlayer spacing of MXene nanosheets compared with et-Ti₃C₂MXene nanosheets are significantly enlarged.

MoS prepared in this example₂/Ti₃C₂The mapping diagram of MXene composite material is shown in FIG. 4, and from FIG. 4, MoS can be seen₂Nanosheet being in Ti₃C₂Uniform growth on MXene.

Example 2

(1) preparation of et-Ti₃C₂MXene nano-sheet

(2) Preparation of in-Ti₃C₂MXene nano-sheet

1g of et-Ti₃C₂MXene nanosheets are dispersed in 30mL of 1.8mol/LNaOH solution, and the obtained mixture is continuously stirred and reacted for 6 hours at room temperature; after the reaction is finished, centrifuging, washing the obtained precipitate for 6 times by using deionized water, and freeze-drying the product obtained by washing at-30 ℃ for 24 hours to obtain in-Ti₃C₂MXene nano-sheet.

(3) Preparation of MoS₂/Ti₃C₂MXene composite material

0.2g of in-Ti prepared in the step (2)₃C₂Dispersing MXene nano-sheets in 30mL of deionized water, and carrying out ultrasonic treatment for 30min to obtainin-Ti₃C₂MXene nanosheet dispersion; then 0.12g of sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) and 0.2g of thioacetamide (CH)₃CSNH₂) Dissolving the molybdenum precursor and the sulfur precursor in 30mL of deionized water, and magnetically stirring to obtain a mixed solution of the molybdenum precursor and the sulfur precursor; under the conditions of ultrasonic and magnetic stirring, dropwise adding the mixed solution of a molybdenum precursor and a sulfur precursor into in-Ti₃C₂Continuously stirring the MXene nanosheet dispersion liquid for 1h, transferring the obtained mixed liquid into a 100mL stainless steel autoclave with a polytetrafluoroethylene lining, and reacting for 24h at 200 ℃; naturally cooling to room temperature, respectively centrifugally washing the obtained black precipitate with deionized water and absolute ethyl alcohol for 5 times, and freeze-drying the washed product at-30 ℃ for 24 hours to obtain MoS₂/Ti₃C₂MXene composite material.

Example 3

(1) preparation of et-Ti₃C₂MXene nano-sheet

(2) Preparation of in-Ti₃C₂MXene nano-sheet

1g of et-Ti₃C₂MXene nanosheets are dispersed in 20mL of 1.8mol/L NaOH solution, and the obtained mixture is continuously stirred and reacted for 6 hours at room temperature; after the reaction is finished, centrifuging, washing the obtained precipitate for 6 times by using deionized water, and freeze-drying the product obtained by washing at-30 ℃ for 24 hours to obtain in-Ti₃C₂MXene nano-sheet.

(3) Preparation of MoS₂/Ti₃C₂MXene composite material

0.2g of in-Ti prepared in the step (2)₃C₂Dispersing MXene nano-sheets in 30mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain in-Ti₃C₂MXene nanosheet dispersion; then 0.12g of sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) and 0.2g of thioacetyl (CH)₃CSNH₂) Dissolving the molybdenum precursor and the sulfur precursor in 30mL of deionized water, and magnetically stirring to obtain a mixed solution of the molybdenum precursor and the sulfur precursor; under the conditions of ultrasonic and magnetic stirring, dropwise adding the mixed solution of a molybdenum precursor and a sulfur precursor into in-Ti₃C₂Continuously stirring the MXene nanosheet dispersion liquid for 1h, transferring the obtained mixed liquid into a 100mL stainless steel autoclave with a polytetrafluoroethylene lining, and reacting for 24h at 180 ℃; naturally cooling to room temperature, respectively centrifugally washing the obtained black precipitate with deionized water and absolute ethyl alcohol for 5 times, and freeze-drying the washed product at-30 ℃ for 24 hours to obtain MoS₂/Ti₃C₂MXene composite material.

Comparative example 1

in-Ti₃C₂The preparation method of the MXene material comprises the following steps:

(1) the procedure was as described in step (1) of example 1.

(2) 1g of et-Ti₃C₂MXene nanosheets are dispersed in 20mL of 1.8mol/L NaOH solution, and the obtained mixture is continuously stirred and reacted for 6 hours at room temperature; after the reaction is finished, centrifuging, washing the obtained precipitate for 6 times by using deionized water, and freeze-drying the product obtained by washing at-30 ℃ for 24 hours to obtain in-Ti₃C₂MXene nano-sheet.

in-Ti prepared in this comparative example₃C₂The XRD pattern of MXene material is shown in figure 3.

Comparative example 2

MoS₂The preparation method of the nanosheet comprises the following steps:

0.12g of sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) and 0.2g of thioacetamide (CH)₃CSNH₂) Dissolved in 60mL of deionized waterAfter a homogeneous solution was formed under magnetic stirring, the resulting mixture was transferred to a 100mL stainless steel autoclave lined with polytetrafluoroethylene and reacted at 200 ℃ for 24 h. After the reaction is finished, naturally cooling to room temperature, centrifuging, respectively centrifugally washing the obtained black precipitate for 5 times by using deionized water and absolute ethyl alcohol, and then freeze-drying at-30 ℃ for 24 hours to obtain MoS₂Nanosheets.

MoS prepared in this comparative example₂SEM and TEM photographs of the nanosheets are shown in FIG. 5, and it can be seen from FIG. 5 that the MoS was prepared₂The stacking of the nanosheets is severe.

Comparative example 3

MoS₂/Ti₃C₂MXene composite was prepared as described in example 1, except that: the concentration of the NaOH solution in the step (2) is 0.5mol/L and 4mol/L respectively.

in-Ti prepared in this comparative example₃C₂The SEM image of MXene nanosheets is shown in FIG. 6, and it can be seen from FIG. 6a that et-Ti₃C₂The ratio of MXene nano-sheet to intercalation agent is low, the intercalation effect is not obvious, and et-Ti can be seen from figure 6b₃C₂Too high ratio of MXene nanosheet to intercalating agent results in-Ti₃C₂The nanosheet is damaged.

MoS obtained in this comparative example₂/Ti₃C₂The SEM image of the MXene composite is shown in FIG. 7, and it can be seen from FIG. 7a that et-Ti₃C₂The ratio of MXene nano-sheet to intercalation agent is low, and the obtained MoS₂/Ti₃C₂MoS in MXene composite material₂The nano-sheets are distributed in Ti₃C₂MXene nanosheet surface with only a small amount of embedded Ti₃C₂MXene nanosheet interlayer; as can be seen in FIG. 7b, et-Ti₃C₂The ratio of MXene nano-sheet to intercalation agent is too high, resulting in-Ti₃C₂The nanosheet was damaged and MoS could not be obtained₂The nano-sheets are uniformly supported on Ti₃C₂MXene surface and interlaminar morphology.

Comparative example 4

MoS₂/Ti₃C₂The preparation method of the MXene composite material comprises the following steps:

(1) preparation of et-Ti₃C₂MXene nano-sheet

(2) Preparation of MoS₂/Ti₃C₂MXene composite material

0.2g of et-Ti prepared in step (1)₃C₂Dispersing MXene nano-sheets in 30mL of deionized water, and carrying out ultrasonic treatment for 30min to obtain et-Ti₃C₂MXene nanosheet dispersion; then 0.12g of sodium molybdate dihydrate (Na)₂MoO₄·2H₂O) and 0.2g of thioacetamide (CH)₃CSNH₂) Dissolving the molybdenum precursor and the sulfur precursor in 30mL of deionized water, and magnetically stirring to obtain a mixed solution of the molybdenum precursor and the sulfur precursor; under the conditions of ultrasonic and magnetic stirring, dropwise adding a mixed solution of a molybdenum precursor and a sulfur precursor into et-Ti₃C₂Continuously stirring the MXene nanosheet dispersion liquid for 1h, transferring the obtained mixed liquid into a 100mL stainless steel autoclave with a polytetrafluoroethylene lining, and reacting for 24h at 180 ℃; naturally cooling to room temperature, respectively centrifugally washing the obtained black precipitate with deionized water and absolute ethyl alcohol for 5 times, and freeze-drying the washed product at-30 ℃ for 24 hours to obtain MoS₂/Ti₃C₂MXene composite material.

MoS was obtained in this comparative example₂/Ti₃C₂The SEM image of the MXene composite material is shown in FIG. 8, and it can be seen from FIG. 8 that Ti₃C₂MXene close packing with only a small amount of MoS₂Embedding between layers, MoS cannot be obtained₂Nanosheet being in Ti₃C₂MXene surface and interlayer vertical negativityA loaded composite material.

Test example 1

MoS obtained in example 1₂/Ti₃C₂MXene composite, in-Ti obtained in comparative example 1₃C₂MXene materials, MoS obtained in comparative example 2₂Nanosheets, comparative example 3 and MoS prepared in comparative example 4₂/Ti₃C₂The MXene composite material is used as a negative electrode material to be applied to a potassium ion battery, and the electrochemical performance of the potassium ion battery is tested by the specific method as follows:

MoS obtained in example 1₂/Ti₃C₂MXene composite, in-Ti obtained in comparative example 1₃C₂MXene materials, MoS obtained in comparative example 2₂Nanosheets, comparative example 3 and MoS prepared in comparative example 4₂/Ti₃C₂The MXene composite material is an active substance, the active substance, polyvinylidene fluoride (PVDF, HSV900) binder and conductive carbon black (super-PLI) are mixed according to the mass ratio of 70:15:15, then the mixture is uniformly ground, N-methyl pyrrolidone serving as a solvent is added (the mass of the N-methyl pyrrolidone is 3 times of the total mass of the active substance, the polyvinylidene fluoride binder and the conductive carbon black), the mixture is stirred for 12 hours to prepare uniform slurry, the uniform slurry is uniformly coated on copper foil, and the uniform slurry is dried in vacuum at 80 ℃ for 12 hours to obtain the negative electrode material for the potassium ion battery. Potassium metal as counter electrode, glass fiber membrane (GF/D whatman) as diaphragm, potassium hexafluorophosphate (KPF)₆) A solution obtained by dissolving a mixed solvent of Ethylene Carbonate (EC) and diethyl carbonate (DEC) was used as an electrolyte (the volume ratio of ethylene carbonate to diethyl carbonate was 1:1, the concentration of potassium hexafluorophosphate in the electrolyte is 0.8mol/L), and assembling the button cell 2025 in a vacuum glove box.

MoS obtained in example 1₂/Ti₃C₂MXene composite, in-Ti obtained in comparative example 1₃C₂MXene materials, MoS obtained in comparative example 2₂The cycle performance curve of the electrode with the nanosheet as the negative electrode material is shown in fig. 9, and it can be seen from fig. 9 that the MoS prepared in the embodiment 1 of the invention₂/Ti₃C₂MXene composite material electrode in 0.1Ag^-1After 200 cycles at a current density of 360.0mAhg^-1Has a reversible capacity significantly better than that of in-Ti of comparative example 1₃C₂MXene and MoS₂Reversible capacities of nanosheet electrodes 158.6 and 63.9mAhg^-1And excellent cycle performance is shown.

MoS prepared according to the invention in example 1₂/Ti₃C₂The long cycle performance curve of MXene composite is shown in FIG. 10, and can be seen from FIG. 10 at 0.5A g^-1At a current density of 195.5mAh g for 1300 cycles^-1The reversible capacity of (2) shows an excellent long-cycle stability, with a rate of decay per cycle of only 0.01%.

MoS prepared in comparative example 3₂/Ti₃C₂The cycle performance curve of the electrode using MXene composite material as the negative electrode material is shown in FIG. 11. from FIG. 11, it can be seen that MoS is obtained by using the intercalator with low concentration and high concentration₂/Ti₃C₂MXene composite material electrode at 0.1A g^-1Respectively has a current density of 95.9mAhg after 200 cycles^-1And 108.8mAhg^-1The reversible capacity of (a) is fast in performance decay during the circulation process, and is obviously inferior to that of the embodiment 1 of the invention. From the above, it can be seen that the intercalator concentration and ratio are such that a high performance long life MoS is produced₂/Ti₃C₂The MXene composite material electrode has extremely important function.

MoS prepared in comparative example 3₂/Ti₃C₂The cycle performance curve of the electrode taking MXene composite material as the negative electrode material is shown in FIG. 12, and the MoS obtained from FIG. 12₂/Ti₃C₂The MXene composite material is used as the negative electrode of the potassium ion battery and is 0.1Ag^-1The performance decays very fast at current density.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. MoS for high-performance potassium ion battery₂/Ti₃C₂The preparation method of the MXene composite material comprises the following steps:

2. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the intercalation agent in the step (1) is NaOH, LiOH or KOH; the et-Ti₃C₂The mass ratio of the MXene nanosheets to the intercalating agent is 1: 0.8-2.4, and preferably 1: 1-2.

3. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the concentration of the intercalation agent solution in the step (1) is 1-3 mol/L.

4. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the reaction time in the step (1) is 5-8 hours; the washing is carried out for 6 times by using deionized water; the drying is to freeze-dry the washed product at-30 ℃ for 24 h.

5. The MoS of claim 1₂/Ti₃C₂The preparation method of MXene composite material is characterized in that the in-Ti₃C₂The concentration of the MXene nanosheet dispersion is 5.0-8.0 mg/mL, preferably 6.6-6.7 mg/mL.

6. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the molybdenum precursor in the step (2) is sodium molybdate dihydrate or ammonium molybdate; molybdenum element and in-Ti in the molybdenum precursor₃C₂The mass ratio of the MXene nanosheets is 1: 3-5.

7. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the sulfur precursor in the step (2) is thioacetamide or thiourea; the sulfur precursor contains sulfur element and in-Ti₃C₂The mass ratio of the MXene nanosheets is 1: 2-3.

8. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the mass concentration of a molybdenum precursor in the mixed solution in the step (2) is 2-6 mg/mL, and the mass concentration of a sulfur precursor in the mixed solution is 4-8 mg/mL; the mixed solution of the molybdenum precursor and the sulfur precursor is added into the system in a dropwise manner.

9. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the reaction temperature in the step (2) is 180-220 ℃, and the reaction time is 18-36 hours.

10. The MoS of claim 1₂/Ti₃C₂The preparation method of the MXene composite material is characterized in that the washing in the step (2) is centrifugal washing for 4-6 times by respectively using water and ethanol; the drying is freeze drying for 24-48 h at-30 ℃.