A method for ultrafast synthesis of nitrogen-doped carbon dots composite vanadium trioxide aqueous zinc ion battery positive electrode material using flash Joule heat

Abstract

The invention belongs to the technical field of battery materials, and discloses a method for ultrafast synthesis of nitrogen-doped carbon dots composite vanadium trioxide aqueous zinc ion battery positive electrode materials by flash Joule heat. The steps are: first, a certain mass of vanadium pentoxide powder is added to a sodium chloride solution of a certain concentration and mixed and stirred for a period of time, and then the sodium chloride-treated vanadium pentoxide powder is obtained by centrifugal drying. Subsequently, urea and the treated vanadium pentoxide powder are evenly mixed and fully ground according to a certain mass ratio. Finally, the ground powder is placed on a carbon conductive substrate of a Joule furnace, and the nitrogen-doped carbon dots composite vanadium trioxide aqueous zinc ion battery positive electrode material of the present invention can be prepared by flash Joule heat treatment. The nitrogen-doped carbon dots / vanadium trioxide composite material prepared by this method exhibits excellent charge and discharge performance and good cycle stability. The present invention has the remarkable characteristics of simple synthesis method, low production cost and mass production.

Description

Technical Field

[0001] The invention provides an ultrafast preparation method for a vanadium-based aqueous zinc ion battery positive electrode material, specifically a method for ultrafast synthesis of nitrogen-doped carbon dot composite vanadium trioxide aqueous zinc ion battery positive electrode material by flash Joule heat. Background Art

[0002] Among various energy storage systems, lithium-ion batteries have dominated the commercial secondary battery market due to their high energy density and long cycle life. However, lithium-ion batteries have the problems of flammable organic electrolytes and scarce lithium resources, which seriously affect their large-scale application. Therefore, it is imperative to design and develop aqueous secondary rechargeable batteries with low cost, safety, environmental protection and high energy density. Among the many aqueous energy storage systems, aqueous zinc-ion batteries have the significant advantages of high theoretical capacity (820mAh / g) and low redox potential. In recent years, aqueous zinc-ion batteries have gained more and more attention as a new type of green power source, and they have also shown broader application prospects in the field of energy storage.

[0003] The most widely studied positive electrode materials for aqueous zinc-ion batteries are manganese-based oxides, vanadium-based oxides, and Prussian blue. Among them, Prussian blue has a low capacity and poor cyclability; while manganese-based oxides have poor rate performance and rapid capacity decay. In contrast, vanadium-based oxides include vanadium pentoxide (V 2 O 5 ), vanadium dioxide (VO 2 ), vanadium trioxide (V 2 O 3 ) have the significant advantages of low price, abundant reserves and high theoretical capacity. Among these materials, vanadium trioxide has the characteristics of three-dimensional VV framework and tunnel structure and low toxicity, so it has attracted widespread attention from researchers. However, at the same time, vanadium trioxide has the problem of structural collapse caused by large spatial structure and valence state change during charging and discharging, as well as poor conductivity, which seriously hinders its application and development in the field of aqueous zinc-ion batteries.

[0004] Composite graphene, carbon nanotubes, carbon dots and other highly conductive materials are one of the common strategies to improve the electrochemical performance of vanadium trioxide. Carbon nanomaterials can effectively improve the conductivity of vanadium trioxide, reduce the Coulomb resistance encountered by zinc ions when they are embedded and extracted during the cycle, and thus increase the diffusion coefficient of zinc ions.

[0005] Prior to this invention, the synthesis of traditional carbon / vanadium trioxide composite materials was mostly based on hydrothermal and long-term calcination. The preparation method was time-consuming, labor-intensive, cumbersome, and costly, and was not suitable for large-scale industrial production. In contrast, the flash Joule heating method uses ultrashort pulse current to directly heat the sample, requiring extremely low energy consumption and can instantly reach ultra-high temperatures above 3000°C. It also has the characteristics of ultra-fast heating and ultra-fast cooling, which is very conducive to the rapid and large-scale production of various materials. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a vanadium-based aqueous zinc ion battery positive electrode material which has simple process, low production cost and is convenient for large-scale production.

[0007] In order to achieve the above-mentioned purpose of the invention, the present invention uses the flash Joule heating method and takes advantage of its ultra-fast heating characteristics to prepare and synthesize the positive electrode material of nitrogen-doped carbon dots composite vanadium trioxide.

[0008] It specifically includes the following steps:

[0009] The first step is to add a certain mass of vanadium pentoxide powder into a sodium chloride solution of a certain concentration, mix and stir at room temperature for a certain period of time, and then centrifuge and dry to obtain sodium chloride-treated vanadium pentoxide powder for use;

[0010] Step 2: Weigh a certain amount of vanadium pentoxide powder treated with urea and sodium chloride and grind it evenly for later use;

[0011] Step 3: Place the mixed powder on graphite paper in a Joule furnace and quickly process it through flash Joule heat to obtain the nitrogen-doped carbon dot composite vanadium trioxide aqueous zinc ion battery positive electrode material.

[0012] Further, in the above-mentioned preparation method, the usage ratio of vanadium pentoxide powder and sodium chloride solution is 1-5g:100mL, wherein the concentration of sodium chloride solution is 1-5mol / L; and the mixing and stirring time at room temperature is 72 hours.

[0013] In the above preparation method, the drying temperature of the vanadium pentoxide powder treated with sodium chloride is 50-80° C. and the drying time is 12 hours.

[0014] Further, in the above-mentioned preparation method, the mass ratio of the vanadium pentoxide powder treated with sodium chloride to urea is 1:0.5 to 1:2.

[0015] In the above-mentioned preparation method, the carbon conductive substrate used is carbon paper, graphite paper, carbon cloth or carbon fiber cloth.

[0016] Further in the above preparation method, the mass of the mixed powder placed on the carbon conductive substrate is 100 to 500 mg.

[0017] Further, in the above-mentioned preparation method, the parameters used for the flash Joule heat treatment are: voltage 10-25 volts, current 50-200 amperes, and heating time 200-500 milliseconds.

[0018] Further, in the above-mentioned preparation method, the flash Joule heat treatment is carried out in an air atmosphere, and the number of treatments is 1-5 times.

[0019] The beneficial effects of the present invention are:

[0020] Aiming at the disadvantages of the current carbon dot / vanadium trioxide composite material, which has harsh synthesis process, complicated method, long synthesis time and high cost, the present invention adopts flash Joule heating technology to synthesize nitrogen-doped carbon dot / vanadium trioxide composite material in one step at ultrafast speed. The advantages are simple synthesis process, low cost, large-scale production, and the synthesized composite material has excellent electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the reaction of preparing nitrogen-doped carbon dots / vanadium trioxide composite positive electrode materials by the method of the present invention;

[0022] Figure 2 is a scanning electron microscope (SEM) image of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 1 of the method of the present invention;

[0023] Figure 3 is a transmission electron microscope (HRTEM) image of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 1 of the method of the present invention;

[0024] Figure 4 is an X-ray diffraction (XRD) diagram of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 1 of the method of the present invention;

[0025] Figure 5 is an X-ray photoelectron spectrum (XPS) graph of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 1 of the method of the present invention;

[0026] Figure 6 is a capacity cycle diagram of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 1 of the method of the present invention;

[0027] Figure 7 This is a long cycle performance diagram of the nitrogen-doped carbon dot / vanadium trioxide composite cathode material in Example 1 of the method of the present invention;

[0028] Figure 8 It is a capacity cycle diagram of the nitrogen-doped carbon dot / vanadium trioxide composite positive electrode material in Example 2 and Example 3 of the method of the present invention. DETAILED DESCRIPTION

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0030] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0031] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0032] Embodiment 1:

[0033] (1) 2 g of vanadium pentoxide was added to 100 ml of 2 mol sodium chloride solution and stirred at room temperature for 72 hours, then centrifuged and washed at 60 degrees for 12 hours and dried for later use;

[0034] (2) weighing urea and sodium chloride treated vanadium pentoxide powder in a mass ratio of 1:1 and grinding them evenly for later use;

[0035] (3) Weigh 500 mg of the above mixed powder and place it on graphite paper in a Joule furnace, and start the rapid annealing mode, set the current to 15 volts and 200 amperes (the temperature can reach ∼1600 degrees), and process it once (time is about 300 milliseconds).

[0036] (4) The carbon dot / vanadium trioxide composite material, conductive carbon black and polyvinylidene fluoride were weighed in an agate mortar at a mass ratio of 70:20:10, and N-methylpyrrolidone solvent was added for thorough grinding. The slurry obtained by grinding was evenly coated on the surface of the titanium foil, and after coating, it was placed in a vacuum drying oven for drying for 12 hours. Subsequently, the dried titanium foil was cut into discs with a diameter of 12 mm and used as electrode plates, with metallic zinc as the counter electrode, 3 mol / L zinc trifluoromethanesulfonate as the electrolyte, and Waterman GF / D glass fiber membrane as the diaphragm to form a button cell. The assembled battery was subjected to charge and discharge tests, and the test voltage range was 0.2-1.6V.

[0037] Embodiment 2:

[0038] Example 1 was repeated, except that the mass ratio of urea to the vanadium pentoxide powder treated with sodium chloride was 1:2.

[0039] Embodiment 3:

[0040] Example 1 was repeated, except that the mass ratio of urea to the vanadium pentoxide powder treated with sodium chloride was 2:1.

[0041] like Figure 1As shown, the main preparation process of the nitrogen-doped carbon dot / vanadium trioxide composite material is: placing the uniformly mixed sodium chloride-treated vanadium pentoxide / urea sample on the graphite paper of the Joule furnace, and preparing the nitrogen-doped carbon dot / vanadium trioxide composite material by flash Joule heat treatment.

[0042] like Figure 2 As shown, the SEM morphology of the nitrogen-doped carbon dot / vanadium trioxide composite material prepared in Example 1 is an aggregated morphology of multilayer nanobelts.

[0043] like Figure 3 As shown, the HRTEM morphology of the nitrogen-doped carbon dot / vanadium trioxide composite material prepared in Example 1 is a nanobelt morphology, and the lattice spacing of 0.21 nm is consistent with the (110) crystal plane of graphite, confirming the successful preparation of the carbon dot / vanadium trioxide material composite material.

[0044] like Figure 4 As shown, the crystal structure of the nitrogen-doped carbon dot / vanadium trioxide composite material prepared in Example 1 is mainly vanadium trioxide, which further confirms the successful preparation of the carbon dot / vanadium trioxide material composite material.

[0045] like Figure 5 As shown, the high-resolution N1s and C1s XPS spectra of the nitrogen-doped carbon dots / vanadium trioxide composite material prepared in Example 1 show that nitrogen elements are successfully doped into the carbon dots, indicating the successful preparation of the nitrogen-doped carbon dots.

[0046] like Figure 6 As shown, the capacity cycling performance curve indicates that when the test current density is 1 A / g, the discharge specific capacity of the nitrogen-doped carbon dots / vanadium trioxide composite material is still as high as 330 mAh / g after 1000 cycles.

[0047] like Figure 7 As shown, the long cycle stability performance indicates that at a test current density of 10 A / g, the capacity of the nitrogen-doped carbon dots / vanadium trioxide composite material can still be maintained at 138.7 mAh / g after 5000 cycles.

[0048] like Figure 8 As shown, the capacity cycle performance curve shows that when the test current density is 1A / g, the capacity of the nitrogen-doped carbon dot / vanadium trioxide composite material prepared in Example 2 is only 24mAh / g after 150 cycles, which is significantly lower than the performance of the sample in Example 1. The capacity of the nitrogen-doped carbon dot / vanadium trioxide composite material prepared in Example 3 is only 90.1mAh / g after 600 cycles, which is also significantly lower than the performance of the sample in Example 1.

Claims

1. A method for ultrafast synthesis of nitrogen-doped carbon dots composite vanadium trioxide zinc ion battery positive electrode material by flash Joule heat, characterized in that: The steps include: The first step is to add a certain mass of vanadium pentoxide powder into a sodium chloride solution of a certain concentration, mix and stir at room temperature for a certain period of time, and then centrifuge and dry to obtain sodium chloride-treated vanadium pentoxide powder for use; Step 2: Weigh a certain mass of urea and the vanadium pentoxide powder treated with sodium chloride in the first step, grind them evenly for later use; wherein the mass ratio of the vanadium pentoxide powder treated with sodium chloride to urea is 1:1; Step 3: Place the powder ground in the second step on a carbon conductive substrate in a Joule furnace, and obtain the nitrogen-doped carbon dot composite vanadium trioxide aqueous zinc ion battery positive electrode material through flash Joule heat treatment.

2. The method according to claim 1, characterized in that: In the first step, the dosage ratio of vanadium pentoxide powder and sodium chloride solution is 1-5g:100mL, wherein the concentration of the sodium chloride solution is 1-5mol / L; the mixing and stirring time at room temperature is 72 hours.

3. The method according to claim 1, characterized in that In the first step, the drying temperature of the vanadium pentoxide powder treated with sodium chloride is 50-80° C. and the drying time is 12 hours.

4. The method according to claim 1, characterized in that: In the third step, the carbon conductive substrate used is carbon paper or carbon cloth.

5. The method according to claim 4, characterized in that In the third step, the carbon paper used is graphite paper, and the carbon cloth used is carbon fiber cloth.

6. The method according to claim 1, characterized in that In the third step, the parameters used for the flash Joule heat treatment are: voltage 10-25 volts, current 50-200 amperes, and heating time 200-500 milliseconds.

7. The method according to claim 1, characterized in that The flash Joule heat treatment is carried out in an air atmosphere, and the number of treatments is 1 to 5 times.

8. Use of the nitrogen-doped carbon dot composite vanadium trioxide obtained by the method according to any one of claims 1 to 7 as a positive electrode material for zinc ion batteries.

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