Fiber composite material for potassium metal negative electrode and preparation method and application thereof

Abstract

The application discloses a fiber composite material for a potassium metal negative electrode and a preparation method and application thereof, and relates to the technical field of material preparation.The fiber composite material for the potassium metal negative electrode is a selenium-sulfurized molybdenum / carbon fiber composite material, the diameter of the carbon fiber in the selenium-sulfurized molybdenum / carbon fiber composite material is 100-600 nm, and the loading amount of the selenium-sulfurized molybdenum is 40wt%-70wt%.The preparation method comprises the following steps: adding polyacrylonitrile and ammonium molybdate tetrahydrate into N,N dimethylformamide to stir to form a precursor solution, preparing a fiber membrane through an electrostatic spinning method, and stabilizing the fiber membrane through pre-oxidation; and placing the pre-oxidized fiber membrane, selenium powder and sulfur powder into a tube furnace to perform high-temperature sintering, so as to obtain the selenium-sulfurized molybdenum / carbon fiber composite material.The preparation method is simple and controllable, has low cost, raw materials are easy to obtain, and is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of material preparation, and particularly relates to a fiber composite material for a potassium metal negative electrode and a preparation method and application thereof. BACKGROUND

[0002] Due to abundant natural resources, a high theoretical specific capacity (687 mAh g -1 ) and a low working potential (-2.93 V vs. standard hydrogen electrode), metal potassium (K) is considered as a promising anode material for low-cost high-energy potassium batteries. However, the potassium metal anode has serious safety hazards due to uncontrollable dendrite growth and huge volume change during the potassium plating / stripping process, which limits its application in practical batteries. In the past few decades, many different methods have been proposed to overcome the above problems, including optimizing the liquid electrolyte, constructing an artificial solid electrolyte interface, and adopting new separators and solid electrolytes.

[0003] Nowadays, three-dimensional conductive frameworks have shown promise for the manufacture of dendrite-free potassium metal anodes. Compared with traditional current collectors (copper foils), frameworks with high electrical conductivity can reduce local current density by homogenizing ion / electron flux to some extent, thereby alleviating the problems of potassium dendrite formation and huge volume change. In order to induce potassium deposition within the framework, various different potassiumophilic sites have been introduced into the host structure, such as Ag particles, Sn particles, nitrogen-zinc doping, etc.

[0004] The application provides a fiber composite material for a potassium metal negative electrode and a preparation method and application thereof. Molybdenum selenosulfide is used as a potassiumophilic site to prepare a molybdenum selenosulfide / carbon fiber three-dimensional framework for a dendrite-free potassium metal anode. The presence of molybdenum selenosulfide helps the intercalation of potassium ions, and the potassiumophilic property of the final phase K2Se x S 1-x obtained by the reaction is conducive to the uniform deposition of potassium metal. In addition, the three-dimensional conductive carbon fiber network ensures the rapid diffusion of potassium ions, preventing the formation of potassium dendrites during the plating / stripping process, so that the molybdenum selenosulfide / carbon fiber can be applied to a potassium metal battery to stably cycle for 275 h. SUMMARY

[0005] The application aims to provide a fiber composite material for a potassium metal negative electrode and a preparation method and application thereof to solve the problems in the prior art, such as the uncontrollable dendrite growth and huge volume change during the potassium plating / stripping process, which causes the potassium metal anode to have serious safety hazards.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] The first aspect of the present application provides a fiber composite material for a potassium metal negative electrode, which is a selenium-sulfur molybdenum / carbon fiber composite material, wherein the carbon fibers are cross-linked and arranged in the selenium-sulfur molybdenum / carbon fiber composite material, and the diameter of the carbon fibers is 100-600 nm.

[0008] The loading amount of the selenium-sulfur molybdenum in the selenium-sulfur molybdenum / carbon fiber composite material is 40wt%-70wt%.

[0009] The second aspect of the present application provides a preparation method of a fiber composite material for a potassium metal negative electrode, which comprises the following steps:

[0010] (1) adding polyacrylonitrile (PAN) and ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 .4H2O) into N,N dimethylformamide (DMF) to stir to form a precursor solution, preparing a fiber membrane by electrospinning the precursor solution, and stabilizing the fiber membrane by pre-oxidation;

[0011] (2) placing the pre-oxidized fiber membrane, selenium powder and sulfur powder into a tube furnace for high-temperature sintering to obtain a selenium-sulfur molybdenum / carbon fiber composite material.

[0012] Preferably, the mass fraction of the polyacrylonitrile in the N,N dimethylformamide in step (1) is 8-20wt%.

[0013] Preferably, the mass ratio of the ammonium molybdate tetrahydrate to the polyacrylonitrile in step (1) is 0.3-1.0:1.

[0014] Preferably, the stirring temperature in step (1) is 25-70℃, and the stirring time is 5-24h.

[0015] Preferably, the electrospinning method in step (1) is specifically as follows: the push speed is 0.2-1.5mL / h, the spinning voltage is 13-22kV, the receiving distance is 10-20cm, the temperature is 20-40℃, and the humidity is 30-60%.

[0016] Preferably, the pre-oxidation temperature in step (1) is 200-300℃, the heating rate is 2-6℃ / min, and the holding time is 1-3h.

[0017] Preferably, the selenium powder and the sulfur powder are ground and then placed in a crucible in step (2), and the pre-oxidized fiber membrane is placed above the selenium powder and the sulfur powder, and then placed in the tube furnace.

[0018] Preferably, the high-temperature sintering temperature in step (2) is 600-1000℃, the heating rate is 2-6℃ / min, the holding time is 1-6h, and the protective atmosphere is argon or nitrogen.

[0019] Preferably, the molar ratio of the selenium powder and the sulfur powder is 1:0.5-2, and the molar ratio of the selenium powder and ammonium molybdate ((NH4)6Mo7O 24 .4H2O) is 7-28:1.

[0020] The third aspect of the present application provides an application of the selenium molybdenum sulfide / carbon fiber composite material in a potassium metal negative electrode, and the application is as follows:

[0021] The selenium molybdenum sulfide / carbon fiber composite material is made into an anode, the potassium metal is made into a cathode, and the anode and the cathode are immersed into a potassium ion electrolyte, a current is loaded on the two electrodes, and a selenium molybdenum sulfide / carbon fiber / potassium composite negative electrode is obtained by an electrochemical deposition method.

[0022] Preferably, the selenium molybdenum sulfide / carbon fiber composite material is cut into a round sheet with a diameter of 8-16 mm as the anode, and the potassium metal is rolled into a round sheet with the same size as the cathode.

[0023] Preferably, the anode and the cathode are immersed into the potassium ion electrolyte, and specifically, the anode and the cathode are assembled into a button cell in a glove box (water and oxygen content is less than 0.01 ppm).

[0024] Preferably, the potassium ion electrolyte is an electrolyte containing KPF6 or KTFSI, the concentration of potassium ions in the electrolyte is 0.8-4 M, and the organic solvent in the electrolyte is one or more than two of EC (ethylene carbonate), DEC (diethyl carbonate), EMC (ethyl methyl carbonate), DMC (dimethyl carbonate) and DME (dimethyl ether of ethylene glycol).

[0025] Preferably, the current size is 0.1-0.4 mA cm -2 ; and the deposition time is 10-50 h.

[0026] The fourth aspect of the present application provides an application of the selenium molybdenum sulfide / carbon fiber composite material in a potassium metal battery, and the potassium metal battery comprises a selenium molybdenum sulfide / carbon fiber / potassium composite negative electrode, which is made of the selenium molybdenum sulfide / carbon fiber composite material.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The selenium molybdenum sulfide / carbon fiber composite material has abundant metal / non-metal potassium-philic sites, which is beneficial to uniform potassium nucleation.

[0029] (2) The three-dimensional conductive nanofiber network of the selenium molybdenum sulfide / carbon fiber composite material ensures the rapid diffusion of potassium ions, prevents the formation of dendrites in the potassium metal negative electrode during the plating / pulling-off process, and also buffers the volume change during the potassium metal deposition process.

[0030] (3), In the application, the molybdenum selenosulfide / carbon fiber composite material is applied in the potassium metal negative electrode, a series of phase change processes of the molybdenum selenosulfide occur, the phase change significantly reduces the potassium nucleation energy barrier, strengthens the interaction between the potassium and the composite fiber interface, and then induces the uniform deposition of the potassium, and the formation of the potassium dendrite is inhibited.

[0031] (4), In the application, polyacrylonitrile (PAN), ammonium molybdate tetrahydrate ((NH4)6Mo7O 24 .4H2O), and DMF are used as raw materials to prepare a fiber membrane through electrospinning, and then the fiber membrane is sintered with selenium powder and sulfur powder at high temperature to obtain the molybdenum selenosulfide / carbon fiber composite material; the preparation method is simple and controllable, low in cost, and easy to obtain raw materials, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a scanning electron microscope (SEM) graph of the molybdenum selenosulfide / carbon fiber composite material in Example 1 of the application;

[0033] Figure 2 It is an X-ray diffraction (XRD) graph of the molybdenum selenosulfide / carbon fiber composite material in Example 1 of the application;

[0034] Figure 3 It is a cycle performance graph of the molybdenum selenosulfide / carbon fiber composite material / potassium composite negative electrode symmetrical battery in Example 1 of the application;

[0035] Figure 4 It is a cycle performance graph of the carbon fiber / potassium composite negative electrode symmetrical battery in Comparative Example 1 of the application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0037] Example 1:

[0038] Preparation method of molybdenum selenosulfide / carbon fiber:

[0039] (1) 1.0 g of PAN was added to 10 mL of DMF, stirred at 60℃ for 5 h, and then 0.5 g of ammonium molybdate tetrahydrate was added and stirred for 12 h to obtain a uniform and stable precursor solution.

[0040] (2) Take 10 mL of precursor solution for electrospinning, the pushing speed is 0.8 mL / h, the spinning voltage is 16 kV, the receiving distance is 18 cm, the temperature is 25℃, and the humidity is 50%, to obtain a fiber membrane.

[0041] (3) The obtained fiber membrane is pre-oxidized in air at 260℃ for 2h, and the heating rate is 2℃ / min.

[0042] (4) Take 0.3g of selenium powder and 0.3g of sulfur powder, grind them and place them in a crucible, then place the pre-oxidized fiber membrane above the selenium powder and sulfur powder, and then place it in a tube furnace. Carbonize at 800℃ for 3h in a nitrogen atmosphere in the tube furnace, with a heating rate of 3℃ / min, to obtain a selenium-sulfur molybdenum / carbon fiber composite material.

[0043] The scanning electron microscope (SEM) image of the selenium-sulfur molybdenum / carbon fiber composite material is shown in Figure 1 , the carbon fibers are cross-linked and arranged, and the fiber diameter is 100-600nm. X-ray diffraction (XRD) is used to detect the material, and from Figure 2 , it can be seen that there are characteristic peaks of selenium-sulfur molybdenum, indicating that the selenium-sulfur molybdenum / carbon fiber composite material is successfully prepared.

[0044] The application of selenium-sulfur molybdenum / carbon fiber in the negative electrode of potassium metal battery is as follows:

[0045] Cut the prepared selenium-sulfur molybdenum / carbon fiber into a round piece with a diameter of 10mm as the anode, and a potassium metal round piece with a diameter of 10mm as the cathode, and assemble them into a button cell in a glove box (water and oxygen content are both less than 0.01ppm) for electrodeposition. The electrolyte is 4M KTFSI dissolved in DME, the constant current is 0.2mA cm -2 , and the deposition time is 20h, to obtain a selenium-sulfur molybdenum / carbon fiber / potassium composite negative electrode. Take the selenium-sulfur molybdenum / carbon fiber / potassium composite negative electrode as the counter electrode and working electrode of the button cell, the separator is glass fiber, and the electrolyte is 4M KFSI dissolved in DME, to measure the cycle performance of potassium deposition / stripping.

[0046] Figure 3 The cycle performance chart of the selenium-sulfur molybdenum / carbon fiber / potassium composite negative electrode symmetric cell. At a current density of 1.0mA cm -2 , the surface capacity is 1.0mAh cm -2 , and it has excellent performance and can be stably cycled for 275h.

[0047] Example 2:

[0048] The difference between Example 1 and Example 2 is the preparation method of selenium-sulfur molybdenum / carbon fiber:

[0049] (1) 1.2 g of PAN was added to 8 mL of DMF and stirred at 50°C for 8 h, then 0.7 g of ammonium molybdate tetrahydrate was added and stirring was continued for 18 h to obtain a uniform and stable precursor solution.

[0050] (2) 8 mL of the precursor solution was taken for electrospinning, the pushing speed was 0.5 mL / h, the spinning voltage was 17 kV, the receiving distance was 16 cm, the temperature was 30°C, and the humidity was 40%, to obtain a fiber membrane.

[0051] (3) The obtained fiber membrane was pre-oxidized in air at 280°C for 1 h, and the heating rate was 5°C / min.

[0052] (4) 0.6 g of selenium powder and 0.5 g of sulfur powder were ground and placed in a crucible, and the pre-oxidized fiber membrane was placed on top of the selenium powder and sulfur powder, then placed in a tube furnace. Carbonization was carried out in a nitrogen atmosphere at 700°C for 4 h in the tube furnace, with a heating rate of 2°C / min, to obtain a molybdenum selenide / sulfide / carbon fiber composite material.

[0053] Example 3:

[0054] The difference from Example 1 is the preparation method of the molybdenum selenide / sulfide / carbon fiber:

[0055] (1) 0.8 g of PAN was added to 10 mL of DMF and stirred at 70°C for 5 h, then 0.45 g of ammonium molybdate tetrahydrate was added and stirring was continued for 8 h to obtain a uniform and stable precursor solution.

[0056] (2) 7 mL of the precursor solution was taken for electrospinning, the pushing speed was 0.9 mL / h, the spinning voltage was 20 kV, the receiving distance was 15 cm, the temperature was 25°C, and the humidity was 55%, to obtain a fiber membrane.

[0057] (3) The obtained fiber membrane was pre-oxidized in air at 230°C for 3 h, and the heating rate was 4°C / min.

[0058] (4) 0.4 g of selenium powder and 0.6 g of sulfur powder were ground and placed in a crucible, and the pre-oxidized fiber membrane was placed on top of the selenium powder and sulfur powder, then placed in a tube furnace. Carbonization was carried out in a nitrogen atmosphere at 1000°C for 2 h in the tube furnace, with a heating rate of 3°C / min, to obtain a molybdenum selenide / sulfide / carbon fiber composite material.

[0059] Comparative Example 1:

[0060] Similar to the steps and parameters of Example 1, the difference is that no ammonium molybdate tetrahydrate, selenium powder, and sulfur powder were added during the preparation process, and carbon fiber was prepared.

[0061] The carbon fiber prepared above was cut into a 10 mm diameter disc as an anode, and a 10 mm diameter potassium metal disc as a cathode, and assembled into a coin cell in a glove box (both water and oxygen contents were lower than 0.01 ppm) for electrodeposition. The electrolyte was 4 M KTFSI in DME, and the constant current was 0.2 mA cm -2 After deposition for 20 h, a carbon fiber / potassium composite anode was obtained. The carbon fiber / potassium composite anode was used as the counter electrode and working electrode of a coin cell, the separator was glass fiber, and the electrolyte was 4 M KFSI in DME, to measure the cycle performance of potassium deposition / stripping.

[0062] Figure 4 The cycle performance of the carbon fiber / potassium composite anode symmetric cell is shown in the figure. The current density was 1.0 mA cm -2 , and the surface capacity was 1.0 mAh cm -2 , and only stable for 78 h before short circuit, indicating serious dendrite growth.

[0063] In summary, the selenium sulfide molybdenum / carbon fiber composite material was prepared by Examples 1-3, and the loading of selenium sulfide molybdenum in the selenium sulfide molybdenum / carbon fiber composite material was 40wt%-70wt%, and the diameter of the carbon fiber was 100-600 nm. The selenium sulfide molybdenum / carbon fiber composite material was first applied to a potassium metal battery, and exhibited a cycle life of more than 275 h.

[0064] The selenium sulfide molybdenum / carbon fiber / potassium composite anode symmetric cell prepared in Example 1 was compared with the carbon fiber / potassium composite anode symmetric cell in Comparative Example 1, which proved that the selenium sulfide molybdenum / carbon fiber composite material prepared in the application could effectively inhibit dendrite growth and improve cycle stability, and had good guiding significance for the application of potassium metal anode in the potassium metal battery, and the method was helpful for the large-scale application of dendrite-free potassium metal anode.

[0065] The above is only used to help understand the method of the application and its core essence, but the protection scope of the application is not limited thereto. For those skilled in the art, according to the technical solution and inventive concept of the application, equivalent replacement or change within the technical scope disclosed by the application should be covered within the protection scope of the application. In summary, the content of the specification should not be understood as a limitation of the application.

Claims

1. Use of a molybdenum selenosulfide / carbon fiber / potassium composite negative electrode in a potassium metal battery, characterized in that, a molybdenum selenosulfide / carbon fiber composite material is prepared as an anode, potassium metal is prepared as a cathode, and the anode and the cathode are infiltrated into a potassium ion electrolyte, a current is loaded on the two poles, and a molybdenum selenosulfide / carbon fiber / potassium composite negative electrode is obtained by an electrochemical deposition method; the carbon fibers in the molybdenum selenosulfide / carbon fiber composite material are cross-linked and arranged, and the diameter of the carbon fibers is 100-600 nm; the loading amount of molybdenum selenosulfide in the molybdenum selenosulfide / carbon fiber composite material is 40 wt%-70 wt%; the preparation method of the molybdenum selenosulfide / carbon fiber composite material comprises the following steps: (1) polyacrylonitrile and ammonium molybdate tetrahydrate are added to N,N dimethylformamide to form a precursor solution, the precursor solution is prepared into a fiber membrane by an electrospinning method, and the fiber membrane is stabilized by pre-oxidation; (2) the pre-oxidized fiber membrane, selenium powder and sulfur powder are placed in a tube furnace for high-temperature sintering to obtain a molybdenum selenosulfide / carbon fiber composite material; the molar ratio of the selenium powder to the sulfur powder is 1:0.5-2, and the molar ratio of the selenium powder to the ammonium molybdate tetrahydrate is 7-28:

1.

2. Use of the molybdenum selenosulfide / carbon fiber / potassium composite negative electrode according to claim 1 in a potassium metal battery, characterized in that, In step (1), the mass fraction of polyacrylonitrile in N,N dimethylformamide is 8-20 wt%, and the mass ratio of the ammonium molybdate tetrahydrate to polyacrylonitrile is 0.3-1.0:

1.

3. Use of the molybdenum selenosulfide / carbon fiber / potassium composite negative electrode according to claim 1 in a potassium metal battery, characterized in that, In step (1), the stirring temperature is 25-70 ℃, and the stirring time is 5-24 h.

4. Use of the molybdenum selenosulfide / carbon fiber / potassium composite negative electrode according to claim 1 in a potassium metal battery, characterized in that, In step (1), the pre-oxidation temperature is 200-300 ℃, the heating rate is 2-6 ℃ / min, and the holding time is 1-3 h.

5. Use of the molybdenum selenosulfide / carbon fiber / potassium composite negative electrode according to claim 1 in a potassium metal battery, characterized in that, In step (2), the selenium powder and the sulfur powder are ground and placed in a crucible, and the pre-oxidized fiber membrane is placed above the selenium powder and the sulfur powder, and then placed in a tube furnace.

6. Use of the molybdenum selenosulfide / carbon fiber / potassium composite negative electrode according to claim 1 in a potassium metal battery, characterized in that, In step (2), the high-temperature sintering temperature is 600-1000 ℃, the heating rate is 2-6 ℃ / min, the holding time is 1-6 h, and the protective atmosphere is argon or nitrogen.

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