WO2022032751A1

WO2022032751A1 - Phosphorus-doped cose2/mxene composite material and preparation method therefor

Info

Publication number: WO2022032751A1
Application number: PCT/CN2020/112574
Authority: WO
Inventors: 张业龙; 周健文; 徐晓丹; 孙宏阳; 叶铨恩; 宋伟东; 刘争
Original assignee: 五邑大学
Priority date: 2020-08-10
Filing date: 2020-08-31
Publication date: 2022-02-17
Also published as: CN112018346A

Abstract

A phosphorus-doped CoSe₂/MXene composite material and a preparation method therefor. A MXene material is used as a framework, CoSe₂ is synthesized and supported on the MXene, and a phosphorus-doped CoSe₂/MXene composite material is used to prepare a high-performance potassium ion battery negative electrode material. The metallic properties of CoSe₂ and the good electrical conductivity of MXene jointly accelerate ion transfer and improve rate performance. The MXene as a framework inhibits agglomeration, increases active sites and specific surface area, and stabilizes the overall structure. A special self-repairing layered space can adapt to volume expansion after repeated intercalation of potassium ions, thereby improving cyclic stability. A small amount of heteroatom doping with phosphorus increases the electronegativity of the CoSe₂/MXene composite, and increases the adsorption capacity, thereby improving charging and discharging capacities. Results have shown that this unique material structure, when used as a negative electrode for a potassium ion battery, improves structural stability, exhibits excellent potassium storage performance, high specific capacity, and good cyclic stability, and can be prepared simply and quickly.

Description

A phosphorus-doped CoSe 2/Mxene composite material and preparation method thereof

technical field

The invention belongs to the technical field of new energy, and in particular relates to a phosphorus-doped CoSe ₂ /MXene composite material and a preparation method thereof.

Background technique

With the rapid growth of large-scale commercial applications, the widespread application of lithium-ion batteries in electronic devices and electric vehicles makes lithium resources scarce, and its cost continues to rise, which has gradually become a concern. In addition, the safety of lithium dendrites is not high, which is another major problem faced by lithium-ion batteries. Therefore, it is necessary to find new energy storage devices with low cost and high safety as an alternative to Li-ion batteries. Potassium is abundant and inexpensive compared to the natural abundance of lithium in the Earth's crust. Potassium-ion batteries have become a promising alternative to lithium-ion batteries, and their research is continuing to deepen. However, the large size and slow reaction kinetics of potassium ions lead to poor battery performance.

CoSe ₂ is a transition metal phosphorus compound, which is an important class of alkali ion intercalation materials. It has the characteristics of large capacity, high conversion rate and high safety, and has good application prospects. However, its shortcomings are also obvious, such as poor conductivity, easy agglomeration, poor rate performance caused by large volume expansion during charge and discharge, and rapid capacity decay.

MXene has a unique accordion-like multilayer structure and good electrical conductivity, and is considered as a potential electrode material. The accordion-like multi-layer structure of MXene is beneficial to increase the contact area during ion diffusion; good electrical conductivity can accelerate the ion diffusion kinetics; surface functional groups can enhance the adsorption capacity. However, its interlayer spacing is small, and the surface functional groups have certain adsorption properties, so the ideal rapid ion migration effect cannot be achieved when used alone. To solve the above problems, immobilizing CoSe _on conductive materials and synthesizing special nanostructures, and increasing the active sites and interlayer spacing by phosphorus doping, are expected to improve its potassium storage performance. MXene has a unique layered structure and good electrical conductivity, which is a good load frame material.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, one of the objectives of the present invention is to provide a phosphorus-doped CoSe ₂ /MXene composite material. Another object of the present invention is to provide a method for preparing the above phosphorus-doped CoSe ₂ /MXene composite material. Further, the present invention provides an application of a phosphorus-doped CoSe ₂ /MXene composite material, and the phosphorus-doped CoSe ₂ /MXene composite material is used for a potassium ion battery negative electrode.

The present invention adopts following technical scheme:

The present invention designs and constructs a phosphorus-doped CoSe ₂ /MXene negative electrode material for high-performance potassium storage. Using the MXene material as a framework, the synthesized CoSe ₂ is loaded on MXene, and a small amount of phosphorus is used to doped CoSe ₂ /MXene composite material. The specific plans are as follows:

A phosphorus-doped CoSe ₂ /MXene composite material and a preparation method thereof, the preparation method belongs to a solvothermal method, and specifically comprises the following steps:

(1) Weigh an appropriate amount of CoSe ₂ nanoparticles, add the CoSe ₂ nanoparticles into an appropriate amount of solvent, and fully stir to obtain a uniformly distributed suspension;

(2) Mix the MXene nanosheets, suspension, phosphorus source and water to prepare a mixed solution with a concentration of 1-100 mg/ml, and then stir for 6-12 h;

(3) Pour the stirred mixture into the lining of the reactor, seal the reactor, put it in an oven and heat it to 120-220°C, continue to react for 12-18h, and cool down naturally, centrifuge, wash, and then vacuum Dry in a drying oven at 50-80 °C to obtain a crude product;

(4) The crude product obtained in step (3) is ground with a mortar to obtain a solid powder with uniform distribution, which is put into the corundum ark, and is gradually heated to 200-350 ° C in a tube furnace full of protective atmosphere, and calcined for 2 -4h, after the furnace temperature was lower than 40 °C, the calcined product was collected to obtain phosphorus-doped CoSe ₂ /MXene composites.

Further, the solvent is at least one of N,N-dimethylformamide, ethanol and acetone, preferably N,N-dimethylformamide; the detergent is deionized water, ethanol At least one of the above, preferably, firstly wash with deionized water for 3-9 times and then wash with absolute ethanol for 3-9 times.

Further, the MXene is one or more of Ti ₃ C ₂ T _x , V ₃ C ₂ T _x , V ₂ CT _x , Nb ₄ C ₃ T _x , and Ti ₃ CNT _x . For example, Ti ₂ CT _x , V ₂ CT _x , preferably, Ti ₃ C ₂ T _x and V ₃ C ₂ T _x in a mass ratio of 1:1-5.

Further, the phosphorus source is one or more of triphenylphosphine, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

Further, the size of CoSe ₂ nanoparticles is 15nm-120nm, and the size of MXene nanosheets is 100nm-1500nm.

Further, the phosphorus doping amount in the phosphorus-doped CoSe ₂ /MXene composite material is 0.1-20wt%, for example, 0.1-4wt%, 6-10wt%, 7-13wt%.

Further, in step (3), the reaction kettle is heated to 120-220°C in an oven, preferably 140-180°C, such as 140°C, 160°C, 180°C, and the reaction time is 12-18h, such as 12h, 15h , 18h.

Further, the molar ratio of the MXene nanosheets, the CoSe ₂ nanoparticles and the phosphorus source is 1:1:0.01-0.8.

Further, the rotational speed of centrifugation described in step (3) is 5500-9000r/min, preferably 7500r/min, and the centrifugation time is 3-8min, such as 3min, 4min, 5min, 6min, 7min, 8min; The temperature is 50-80°C, preferably 60°C, and the drying time is 12-16h, such as 12h, 14h, 16h.

Further, in step (4), the protective gas is one or more of argon, helium and nitrogen, preferably argon.

A phosphorus-doped CoSe ₂ /MXene composite material is obtained by a preparation method of phosphorus-doped CoSe ₂ /MXene.

A potassium ion battery negative electrode, comprising the phosphorus-doped CoSe ₂ /Mxene composite material.

Beneficial effects of the present invention:

(1) MXene can act as a skeleton, providing a layered structure support, larger transfer and ion adsorption area; CoSe ₂ nanoparticles can be mainly concentrated at the edge of the sheet, and CoSe ₂ nanomaterials grow and nucleate in the MXene sheet, It can effectively increase the interlayer spacing, increase the specific surface area, increase the area between the electrode material and the electrolyte, reduce the resistance of electron transport and ion diffusion, and the interaction between the layered MXene and the nanomaterial CoSe ₂ prevents agglomeration; The electrochemically active sites and vacancies are beneficial to increase the ion transport channel, make the components of the CoSe ₂ /MXene composite closely combine, strengthen the synergistic effect of the components, and at the same time help to increase the conductivity and interlayer spacing of the composite material, To a certain extent, the volume expansion is inhibited, thereby improving its electrochemical performance. It can be seen that MXene, CoSe ₂ and phosphorus atoms have a synergistic effect.

(2) Phosphorus-doped CoSe ₂ /MXene composites greatly expand the distance between the sheets while maintaining the accordion-like layered structure, which effectively hinders the stacking of the material sheets, and has obvious advantages in reversible capacity and cycle performance.

(3) The material of the invention is simple in preparation, low in cost, safe and controllable, and the doping amount is controllable, and the application of the phosphorus-doped CoSe ₂ /MXene composite material as a potassium ion battery negative electrode material can be conveniently realized.

Description of drawings

Fig. 1 is the scanning electron microscope image of the MXene material alone in Comparative Example 1;

Fig. 2 is the scanning electron microscope image of phosphorus-doped CoSe ₂ /MXene composite material in Example 1;

3 is a graph showing the cycle performance of the potassium-ion battery assembled with phosphorus-doped CoSe ₂ /MXene composite material in Example 1 at a current density of 100 mA/g.

Figure 4 is a graph of the cycle performance measured at a current density of 100 mA/g for a potassium-ion battery assembled with a single MXene negative electrode material in Comparative Example 1;

Figure 5 is a graph of the cycle performance measured at a current density of 100 mA/g for a potassium-ion battery assembled with a single CoSe ₂ negative electrode material in Comparative Example 2.

6 is a graph showing the cycle performance of the potassium ion battery assembled with CoSe ₂ /MXene material in Comparative Example 3 at a current density of 100 mA/g.

FIG. 7 is a schematic diagram showing the comparison of the test impedance of the potassium ion battery assembled by the single MXene material, the CoSe ₂ /MXene material, and the phosphorus-doped CoSe ₂ /MXene composite material.

detailed description

In order to better explain the present invention, further description will now be given in conjunction with the following specific embodiments, but the present invention is not limited to the specific embodiments. Wherein, the materials are commercially available unless otherwise specified.

Wherein, the materials can be commercially available unless otherwise specified;

The CoSe ₂ nanoparticles were purchased from Taizhou Juna New Energy Co., Ltd., brand 2D Semiconductors, model: 7579.65, purity: 99.999%, type: electronic, optical material, optical band gap of 0.5eV;

The Ti ₃ C ₂ T _x nanoparticles were purchased from Beijing Beike New Material Technology Co., Ltd., number BK2020011814, size: 1-5 μm, purity: 99%, product application fields: energy storage, catalysis, analytical chemistry, etc.

The methods are conventional methods unless otherwise specified.

Example 1

A preparation method of phosphorus-doped CoSe ₂ /MXene composite material, comprising the following steps:

(1) Weigh 21.6 mg of CoSe ₂ nanoparticles, add them to 10 ml of N,N-dimethylformamide (DMF), mix well to obtain a uniformly distributed suspension, and add 16.7 mg of MXene (Ti ₃ C ₂ T _x ) nanosheets, suspension, 0.6 mg of sodium dihydrogen phosphate and 15 ml of deionized water were mixed, followed by magnetic stirring for 7 h;

(2) Pour the stirred mixed solution into the lining of the reactor with a capacity of 60ml, seal the reactor, put it in an oven and heat it to 180°C, continue the reaction for 14h, and cool down naturally, and centrifuge at 7500r/min For 5 min, the filter residue was first washed with deionized water for 5 times and then with absolute ethanol for 5 times, and then the drying temperature was set at 60°C in a vacuum drying oven, and the drying time was 12 h to obtain a crude product;

(3) The crude product obtained in step (2) is ground with a mortar to obtain uniformly distributed solid powder, which is put into a corundum ark, and is gradually heated to 300° C. in a tube furnace filled with an argon atmosphere, and calcined for 4h, The calcined products were collected after the furnace temperature was lower than 40 °C to obtain phosphorus-doped CoSe ₂ /MXene composites.

Phosphorus-doped CoSe ₂ /MXene composite material was used as the active ingredient, mixed with conductive agent super P carbon and polyvinylidene fluoride binder in a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone was added. Stir well and coat it on the copper foil. After drying, the cut piece is used as the working electrode. Using 1M KFSI EC (ethylene carbonate), PC (propylene carbonate) (1:1) as the electrolyte, the metal potassium sheet is cut to Appropriately sized as the counter electrode, glass fibers were cut to a size smaller than the cell casing but larger than the cell pole piece as a separator, and assembled into a 2032 type coin half cell; all assembly was performed in an inert atmosphere glove box.

Under the current density of 100mA/g, the specific capacity of the electrode is stable at 327.8mA h/g after 100 times of charge and discharge, which is the highest value of _{CoSe 2} _/ MXene ( 278.1mA h/g) material, 1.17 times that of pure CoSe ₂ (110.2mA h/g) material, 5.3 times that of pure MXene (61.1mA h/g) material, and the Coulomb efficiency is 97.8%. The obtained phosphorus-doped CoSe ₂ /MXene composite has good potassium storage performance and charge-discharge cycling stability.

Example 2

(1) Weigh 21.6 mg of CoSe ₂ nanoparticles, add them to 10 ml of N,N-dimethylformamide (DMF), mix well to obtain a uniformly distributed suspension, and add 16.7 mg of MXene (Ti ₃ C ₂ T _x ) nanosheets, suspension, 0.4 mg of sodium dihydrogen phosphate and 20 ml of deionized water were mixed, followed by magnetic stirring for 7 h;

(2) Pour the stirred mixed solution into the lining of the reactor with a capacity of 60ml, seal the reactor, put it in an oven and heat it to 180°C, continue the reaction for 12h, and cool down naturally, and centrifuge at 7500r/min For 5 min, firstly wash the filter residue with deionized water for 5 times and then with anhydrous ethanol for 5 times, then set the drying temperature in the vacuum drying oven to 60°C, and the drying time is 14h to obtain the crude product;

Phosphorus-doped CoSe ₂ /MXene composite material was used as the active ingredient, mixed with conductive agent super P carbon and polyvinylidene fluoride binder in a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone was added. Stir well and coat on copper foil. After drying, the cut pieces are used as working electrodes. Using 1M KFSI EC (ethylene carbonate) and PC (propylene carbonate) (1:1) as electrolyte, the potassium metal pieces are cut to Appropriately sized as the counter electrode, glass fibers were cut to a size smaller than the cell casing but larger than the cell pole piece as a separator, and assembled into a 2032 type coin half cell; all assembly was performed in an inert atmosphere glove box.

The potassium ion battery assembled with the phosphorus-doped CoSe ₂ /MXene composite negative electrode material in this example has a stable specific capacity of 333.5 mA h/g and a Coulombic efficiency of 99.7% after being charged and discharged for 100 times at a current density of 100 mA/g. The phosphorus-doped CoSe ₂ /MXene composite obtained in this example has good potassium storage performance and charge-discharge cycle stability.

Example 3

(1) Weigh 43.2 mg of CoSe ₂ nanoparticles, add them to 12 ml of N,N-dimethylformamide (DMF), mix well to obtain a uniformly distributed suspension, and add 32 mg of MXene (Ti ₃ C ₂ T _x ) nanosheets, suspension, 1 mg of sodium dihydrogen phosphate and 25 ml of deionized water were mixed, and then magnetically stirred for 9 h;

(3) Grind the crude product obtained in step (2) with a mortar to obtain a solid powder to make the distribution uniform, put it into a corundum ark, and gradually heat it up to 300° C. in a tube furnace filled with an argon atmosphere, and calcined for 4 hours. , and the calcined products were collected after the furnace temperature was lower than 40 °C to obtain phosphorus-doped CoSe ₂ /MXene composites.

At the current density of 100 mA/g, the potassium ion battery assembled with the phosphorus-doped CoSe ₂ /MXene composite negative electrode material in this example has a stable specific capacity of 319.3 mA h/g and a Coulombic efficiency of 99.7% after being charged and discharged for 100 times. The phosphorus-doped CoSe ₂ /MXene composite obtained in this example has good potassium storage performance and charge-discharge cycle stability.

Example 4

(1) Weigh 43.2 mg of CoSe ₂ nanoparticles, add them to 10 ml of N,N-dimethylformamide (DMF), mix well to obtain a uniformly distributed suspension, and add 32 mg of MXene (Ti ₃ C ₂ T _x ) nanosheets, suspension, 1.8 mg of sodium dihydrogen phosphate and 20 ml of deionized water were mixed, and then magnetically stirred for 7 hours;

(2) Pour the stirred mixed solution into the lining of the reactor with a capacity of 60ml, seal the reactor, put it in an oven and heat it to 180°C, continue the reaction for 12h, and cool down naturally, and centrifuge at 7500r/min For 5 min, the filter residue was first washed with deionized water for 5 times and then with absolute ethanol for 5 times, and then the drying temperature was set at 60°C in a vacuum drying oven, and the drying time was 12 h to obtain a crude product;

(3) Grind the crude product obtained in step (2) with a mortar to obtain a solid powder to make the distribution uniform, put it into a corundum ark, gradually heat it up to 300° C. in a tube furnace filled with an argon atmosphere, and calcine it for 3 hours. , and the calcined products were collected after the furnace temperature was lower than 40 °C to obtain phosphorus-doped CoSe ₂ /MXene composites.

Under the current density of 100 mA/g, the potassium ion battery assembled with the phosphorus-doped CoSe ₂ /MXene composite negative electrode material in this example has a stable specific capacity of 335.2 mA h/g and a Coulombic efficiency of 98.6% after being charged and discharged for 100 times. The phosphorus-doped CoSe ₂ /MXene composite obtained in this example has good potassium storage performance and charge-discharge cycle stability.

Comparative Example 1

Weigh 80mg of MXene material, 10mg of super P and 10mg of polyvinylidene fluoride binder and mix, add a small amount of N-methylpyrrolidone, coat it on copper foil after stirring, dry at 90 °C for 3 hours, and slice it with a microtome. The copper foil was cut into a circular shape as the working electrode. After drying, it was placed in an inert atmosphere glove box with an oxygen and water content below 0.4 ppm. A 2032 type button battery was assembled with a metal potassium sheet as the counter electrode and glass fiber as the separator.

Figure 4 shows the cycle performance of the potassium ion battery assembled with MXene material at a current density of 100 mA/g.

It can be seen from the figure that the potassium ion battery assembled with MXene material has good cycle stability during the charging and discharging process at a current density of 100 mA/g, but the specific capacity is small, which is 61.1 mA h/g.

Comparative Example 2

Weigh 80mg of CoSe ₂ material, 10mg of super P and 10mg of polyvinylidene fluoride binder and mix, add a small amount of N-methylpyrrolidone, coat on copper foil after stirring, dry at 90°C for 3h, use a microtome The copper foil was cut into a circular shape as the working electrode. After drying, it was placed in an inert atmosphere glove box with an oxygen and water content below 0.4 ppm. A 2032 button battery was assembled with a metal potassium sheet as the counter electrode and glass fiber as the separator.

Figure 5 shows the cycle performance of the potassium ion battery assembled with CoSe ₂ material at a current density of 100 mA/g.

It can be seen from the figure that the specific capacity of the potassium ion battery assembled with CoSe ₂ material is relatively unstable during the charging and discharging process at a current density of 100 mA/g, which is 110.2 mA h/g.

Comparative Example 3

(1) Weigh 21.6 mg of CoSe ₂ nanoparticles, add them to 10 ml of N,N-dimethylformamide (DMF), mix well to obtain a uniformly distributed suspension, and add 16.7 mg of MXene (Ti ₃ C ₂ T _x ) nanosheets, the suspension and 15ml of deionized water were mixed, and then magnetically stirred for 7h;

(2) pour the mixed solution after stirring into the lining of the reaction kettle with a capacity of 60ml, seal the reaction kettle, put it into an oven and heat to 180°C, continue the reaction for 14h, and naturally cool down to obtain a precipitate;

(3) The precipitate obtained in step (2) was first washed 5 times with deionized water and then 5 times with absolute ethanol, and the product was moved to a centrifuge and centrifuged for 5 minutes under the condition of 7500 r/min, and then set in a vacuum drying box The drying temperature was 60°C and the drying time was 12h to obtain the crude product;

(4) The crude product obtained in step (3) is ground with a mortar to obtain a solid powder with uniform distribution, which is put into a corundum ark, and is gradually heated to 300° C. in a tube furnace filled with an argon atmosphere, and calcined for 4 hours. The calcined products were collected after the furnace temperature was lower than 40 °C to obtain CoSe ₂ /MXene composites.

The CoSe ₂ /MXene composite material was used as the active ingredient, and it was mixed with the conductive agent super P carbon and the polyvinylidene fluoride binder in a mass ratio of 8:1:1. Coated on copper foil, dried and cut as the working electrode, with 1M KFSI EC (ethylene carbonate), PC (propylene carbonate) (1:1) as the electrolyte, the potassium metal sheet was cut to a suitable size as the electrolyte. For the counter electrode, glass fiber was cut to a size smaller than the cell casing but larger than the cell pole piece as a separator, and assembled into a 2032 type coin half cell; all assembly was performed in an inert atmosphere glove box.

Figure 6 is a graph of the cycle performance of the potassium ion battery assembled with CoSe ₂ /MXene material at a current density of 100 mA/g.

It can be seen from the figure that the potassium-ion battery assembled with CoSe ₂ /MXene material has good cycling stability during the charge-discharge process at a current density of 100 mA/g, and the specific capacity is 278.1 mA h/g.

FIG. 1 is a scanning electron microscope image of the single MXene material in Comparative Example 1, and FIG. 2 is a scanning electron microscope image of the phosphorus-doped CoSe ₂ /MXene composite material in Example 1. It can be seen from Figure 1-2 that the MXene material before doping exhibits an accordion-like layered structure, with complete separation between layers, complete structure, and no layered fracture. The doped MXene material exhibits a large number of fine phosphorus-doped CoSe ₂ nanoparticles uniformly attached to the surface of the MXene material. The introduction of phosphorus-doped CoSe ₂ nanoparticles expands the distance between the sheets without agglomeration, indicating that phosphorus The doped CoSe ₂ /MXene composites greatly enlarged the distance between the lamellae while maintaining the accordion-like layered structure, which effectively hindered the stacking of the material lamellae.

Figure 3 shows the cycle performance of the potassium-ion battery assembled with phosphorus-doped CoSe ₂ /MXene composite material in Example 1 at a current density of 100 mA/g, and the reversible capacity after 100 cycles is 272.8 mA h/g; Figure 3 4 is the cycle performance diagram of the potassium ion battery assembled with the MXene anode material in Comparative Example 1 at a current density of 100 mA/g, and the reversible capacity after 100 cycles is 61.1 mA h/g; Figure 5 is Comparative Example 2 The cycle performance of the potassium-ion battery assembled with the single CoSe ₂ negative electrode material in 100 mA/g at a current density of 100 mA/g shows that the nanosheets are easy to agglomerate and their structure is unstable, the charge and discharge performance is poor, and the specific capacity declines after 30 cycles; Figure 6 shows the cycle performance of the potassium ion battery assembled with CoSe ₂ /MXene material at a current density of 100 mA/g in Comparative Example 3. The potassium ion battery assembled with CoSe ₂ /MXene material was charged and discharged at a current density of 100 mA/g Good potassium storage performance in the process, high specific capacity and stable charge-discharge performance, the battery performance is still not ideal, and its electrochemical performance needs to be further improved.

It can be seen from Figure 3-6 that the reversible capacity of the single MXene material after 100 cycles is very low, only 61.1 mA h/g; the single CoSe ₂ material has the ability to store potassium, but the material is easy to agglomerate and structurally during the charging and discharging process. Instability; although the CoSe ₂ /MXene material without phosphorus atom has high reversible capacity and good cycle performance, the phosphorus-doped CoSe ₂ /MXene composite still has obvious advantages in reversible capacity and cycle performance.

This is because MXene can act as a framework, providing layered structural support, larger transfer and ion adsorption area; CoSe ₂ nanoparticles can be mainly concentrated at the edge of the sheet, and CoSe ₂ nanomaterials grow and nucleate on the MXene sheet, It can effectively increase the interlayer spacing, increase the specific surface area, increase the area between the electrode material and the electrolyte, reduce the resistance of electron transport and ion diffusion, and the interaction between the layered structure MXene and the nanomaterial CoSe ₂ prevents agglomeration; The electrochemically active sites and vacancies are beneficial to increase the ion transport channel, make the components of the CoSe ₂ /MXene composite closely combine, strengthen the synergy of the components, and at the same time help to increase the conductivity and interlayer spacing of the composite, The volume expansion is inhibited to a certain extent, thereby improving its electrochemical performance. It can be seen that MXene, CoSe ₂ and phosphorus atoms have a synergistic effect.

FIG. 7 is a schematic diagram showing the comparison of the test impedance of the potassium ion battery assembled with the MXene material alone, the CoSe ₂ material alone, the CoSe ₂ /MXene material, and the phosphorus-doped CoSe ₂ /MXene composite material. The semicircle diameter of the curve in the mid-frequency region represents the charge transfer resistance Rct. It can be seen from Figure 7 that the Rct values of phosphorus-doped CoSe ₂ /MXene, CoSe ₂ /MXene material, single CoSe ₂ material, and single MXene material increase in turn, indicating that Its charge transfer resistance increases sequentially. Compared with the MXene material, the charge transfer resistance Rct of the CoSe ₂ /MXene composite material becomes smaller. Due to the growth and nucleation of the CoSe ₂ nanomaterial in the MXene sheet, the increase of the interlayer spacing increases the specific surface area, and the area between the electrode material and the electrolyte increases. The transport channel of ions and electrons, together with MXene with good conductivity, accelerates ion transfer and reduces the resistance of electron transport. Compared with the undoped CoSe ₂ /MXene material, the charge transfer resistance Rct of the phosphorus-doped CoSe ₂ /MXene composite material is further reduced, which is due to the increased electronegativity of the CoSe ₂ /MXene composite material due to a small amount of heteroatom phosphorus doping, and the adsorption The capacity is increased to improve the ion transfer capacity. Phosphorus doping further increases the interlayer spacing, increases the specific surface area, and increases the electron transport channel, and the synergistic effect reduces the electron and ion transport resistance.

The above are only preferred specific operation cases of the present invention, and are not used to limit the scope of use of the invention patent, and indirect applications in other related fields are all within the scope of protection of the present invention.

Claims

A preparation method of phosphorus-doped CoSe 2 /Mxene composite material, characterized in that it comprises the following preparation steps:

(1) disperse the CoSe nanoparticles in a solvent to obtain a suspension;

(2) Mix the MXene nanosheets, suspension, phosphorus source and water to prepare a mixed solution with a concentration of 1-100mg/ml, and stir for 6-12h;

(3) heating the stirred mixed solution to 120-220 ° C, reacting for 12-18 h, cooling, centrifuging, washing, and drying to obtain a crude product;

(4) The crude product described in step (3) is fully ground, calcined at 200-350° C. for 2-4 hours in a protective atmosphere, cooled and collected to obtain a phosphorus-doped CoSe 2 /MXene composite material.
The preparation method of phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the solvent is at least one of N,N-dimethylformamide, cyclohexane, and xylene; The detergent is at least one of water and ethanol.
The preparation method of phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the MXene is Ti 3 C 2 T x , V 3 C 2 T x , V 2 CT x , Nb 4 C One or more of 3 T x , Ti 3 CNT x .
The preparation method of phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the phosphorus source is one or more of triphenylphosphine, sodium dihydrogen phosphate, potassium dihydrogen phosphate .
The method for preparing a phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the phosphorus-doped CoSe 2 /MXene composite material has a phosphorus doping amount of 0.1-20wt%.
The preparation method of phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the molar ratio of the MXene nanosheets, CoSe 2 nanoparticles and phosphorus source is 1:1:0.01-0.8.
The preparation method of phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, characterized in that, in step (3), the rotating speed of the centrifugation is 5500-9000 r/min, and the centrifugation time is 3-8 min.
The method for preparing phosphorus-doped CoSe 2 /Mxene composite material according to claim 1, wherein the protective gas in step (4) is one or more of argon, helium, and nitrogen.
A potassium ion battery negative electrode, characterized in that it comprises the phosphorus-doped CoSe 2 /Mxene composite material prepared by the preparation method according to any one of claims 1-8.
A potassium ion battery, characterized in that it comprises the battery negative electrode of claim 9 .