CN110838583B - Carbon nanotube/M-phase vanadium dioxide composite structure, preparation method thereof and application thereof in water-based zinc ion battery - Google Patents

Abstract

The invention discloses a carbon nanotube/M-phase vanadium dioxide composite structure, a preparation method and an application in an aqueous zinc ion battery. The preparation steps of the present invention are as follows: (1) adding carbon nanotubes into deionized water, and ultrasonically using a needle tip to obtain a suspension liquid 1; (2) adding vanadium pentoxide into the suspension liquid 1, then adding a small amount of hydrogen peroxide and stirring , obtain suspension 2; (3) carry out high temperature hydrothermal reaction with suspension 2 and naturally cool after several hours; (4) obtain primary product after product suction filtration, cleaning, freeze-drying; The primary product of carbon nanotubes/M-phase vanadium dioxide composite structure can be obtained by high temperature reduction under gas protection. The carbon nanotube/M-phase vanadium dioxide composite structure of the present invention exhibits excellent rate performance and good stability as a positive electrode material for an aqueous zinc ion battery. It has broad implications for material synthesis methodology and the design of other battery cathode materials.

Description

A kind of carbon nanotube/M phase vanadium dioxide composite structure and preparation method thereof and in water system Applications in Zinc-ion Batteries

technical field

The invention relates to the technical field of nanocomposite materials and electrochemistry, in particular to a carbon nanotube/M-phase vanadium dioxide composite structure, a preparation method thereof, and an application in an aqueous zinc-ion battery.

Background technique

Due to the high energy density and stability of Li-ion batteries in recent years, rechargeable ion batteries have received increasing attention. However, due to factors such as the low content of lithium metal in the crust and the expensiveness of lithium-ion batteries, other metal-ion batteries have gradually attracted attention (Liang, S., et al., ACS Energy Lett. 2018, 3, 2480-2501).

In 1988, Shoji et al. first reported a rechargeable Zn-MnO ₂ zinc-ion battery with a neutral or weakly acidic aqueous electrolyte, creating a precedent for aqueous zinc-ion batteries (Shoji, T., et al., J. Appl. .Electrochem.). Subsequently, more and more cathode materials have been paid attention to by researchers, there are mainly two types, manganese-based and vanadium-based (Zhang, N., et al., J.Am.Chem.Soc. 2016, 138, 12894-12901; Han, S.-D., et al., Chem.Mater. 2017, 29, 4874-4884; Jiang, B., et al., Electrochim. Acta 2017, 229, 422-428; Kundu, D., et al. , Nat. Energy 2016, 1, 16119; Yan, M., et al., Adv. Mater. 2018, 30, 1703725; Ding, J., et al., Adv. Mater. 2019, 1904369). Most of the above literatures do not study the charge-discharge specific capacity of cathode materials at high current densities (>10 A·g). Considering the huge polarization effect at high current densities, the charge-discharge specific capacity of cathode materials usually drops significantly at high current densities. Therefore, it is an urgent technical problem to find new cathode materials with better rate performance and better stability, especially with high specific capacity at higher current density.

Based on the above reasons, the present application is made.

SUMMARY OF THE INVENTION

In view of the above problems or defects in the prior art, the purpose of the present invention is to provide a carbon nanotube/M-phase vanadium dioxide composite structure, a preparation method thereof, and an application as a positive electrode material in an aqueous zinc-ion battery.

The invention adopts carbon nanotubes (CNT) as a three-dimensional frame, which can promote the transmission of electrolyte, reduce the strain effect during ion intercalation, and reduce the influence of side reactions in the electrode process; and carbon nanotubes and M-phase vanadium dioxide (VO ₂ (M)) is uniformly distributed, which avoids metal agglomeration during heat treatment; the prepared carbon nanotube/M-phase vanadium dioxide composite structure as a cathode material exhibits good rate performance in the test of aqueous zinc-ion batteries and outstanding cycle stability.

In order to realize the above-mentioned first purpose of the present invention, the technical scheme adopted in the present invention is as follows:

A carbon nanotube/M-phase vanadium dioxide composite structure, the composite structure comprises carbon nanotubes and M-phase vanadium dioxide nanoparticles, wherein: the M-phase vanadium dioxide nanoparticles are uniformly distributed on the carbon nanotubes The interior of the hollow tube and the surface of the 3D network structure of the carbon nanotubes.

The second object of the present invention is to provide the preparation method of the carbon nanotube/M-phase vanadium dioxide composite structure described above, and the method specifically comprises the following steps:

(1) Disperse carbon nanotubes

The carbon nanotubes are added to the dispersion liquid, and the suspension liquid 1 is obtained by ultrasonication of the needle tip;

(2) Dissolving vanadium pentoxide

Vanadium pentoxide is added to the suspension 1 described in step (1), then a small amount of aqueous hydrogen peroxide solution is added, and the mixture is uniformly stirred to obtain suspension 2;

(3) High temperature water and heat

The suspension 2 in step (2) is sealed into a polytetrafluoroethylene (PTFE) liner and placed in a reaction kettle, and reacted at 120 to 240° C. for 2 to 24 hours. After the reaction is completed, it is naturally cooled to room temperature;

(4) Preparation of carbon nanotube/M-phase vanadium dioxide composite structure

Suction filtration, cleaning and freeze-drying of the product in the reaction kettle of step (3) to obtain primary product; then transfer the primary product to a high-temperature reaction furnace, and under protective gas conditions, the temperature of the reaction furnace is raised to 400~ 800 DEG C, and then continue to reduce under the conditions of gas protection and 400-800 DEG C for 0.1-36 h at constant temperature, and then the carbon nanotube/M-phase vanadium dioxide composite structure can be obtained.

Further, in the above technical scheme, the carbon nanotubes in step (1) are any commercial carbon nanotubes, and the carbon nanotubes can be any one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes. any combination of .

Further, in the above-mentioned technical scheme, the dispersion described in step (1) includes but is not limited to any one or a combination of two or more of deionized water, alcohols, ethers, lipids, and alcohol ethers. as a carrier for dispersing carbon nanotubes. More preferably, the dispersion liquid is deionized water.

Further, in the above technical solution, the ultrasonic time in step (1) is 0.1-1 h.

Further, in the above technical scheme, the vanadium pentoxide described in step (2) is any commercial vanadium pentoxide.

Further, in the above technical solution, the amount ratio of the carbon nanotubes to the dispersion liquid in step (1) is (10-100) parts by mass: (20-80) parts by volume, wherein: between the parts by mass and the part by volume It is based on mg and mL.

Further, in the above technical solution, the dosage ratio of the carbon nanotubes in step (1) to the vanadium pentoxide in step (2) is (10-100) mg: (1-3) mmol.

Further, in the above technical solution, in the hydrogen peroxide aqueous solution described in step (2), the mass fraction of hydrogen peroxide is 30%.

Further, in the above technical solution, the dosage ratio of the vanadium pentoxide and the aqueous hydrogen peroxide solution in step (2) is (1-3) mole parts: (0.1-10) volume parts, wherein: the mole parts Parts by volume are based on mmol and mL.

Further, in the above technical solution, the stirring time in step (2) is 0.1-2h.

Further, in the above technical solution, the cleaning reagent used in the cleaning step of step (4) is any one of acetone, absolute ethanol or deionized water. More preferably, the temperature of the deionized water is 20-100°C.

Further, in the above-mentioned technical scheme, the protective gas described in step (4) is any one or several mixed gases formed in any proportion in nitrogen, argon, helium, hydrogen or ammonia, wherein: the nitrogen, The purity of argon, helium, hydrogen and ammonia is greater than or equal to 99.99%.

Further, in the above technical solution, the high temperature reaction furnace in step (4) adopts program-controlled heating, and the primary product is placed in the central area of the high temperature reaction furnace, and gas protection is introduced. After the reduction reaction, use air cooling or circulating water or shallow frozen water for cooling. The high temperature reaction furnace can be any one of a muffle furnace, a tube furnace or a microwave oven; the cavity material of the high temperature reaction furnace can be any one of quartz, corundum, ceramics or thermal insulation bricks.

Further, the heating rate of the high temperature reaction furnace is preferably 0.1-50°C/min.

Further, the flow rate of the protective gas is 5-500 mL/min.

The third object of the present invention is to provide the application of the above-mentioned carbon nanotube/M-phase vanadium dioxide composite structure as a positive electrode material in an aqueous zinc-ion battery.

A positive electrode material for an aqueous zinc ion battery, the positive electrode material comprises a positive electrode active material and a binder, wherein: the positive electrode active material is the carbon nanotube/M-phase vanadium dioxide composite structure described above.

A positive electrode of an aqueous zinc ion battery, the positive electrode comprises a current collector and a positive electrode material coated and/or filled on the current collector, wherein: the positive electrode material is the above-mentioned positive electrode material of the aqueous zinc ion battery.

An aqueous zinc ion battery, comprising a positive electrode and a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an aqueous electrolyte, wherein: the positive electrode is the above-mentioned positive electrode of the aqueous zinc ion battery; the negative electrode Extremely metallic zinc flakes, and the aqueous electrolyte is an aqueous solution containing zinc salt electrolyte.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The carbon nanotube/M-phase vanadium dioxide composite structure prepared by the invention can be used for the positive electrode of an aqueous zinc ion battery. The dense channels possessed by M-phase vanadium dioxide provide good supports for fast ion intercalation/deintercalation. At the same time, carbon nanotubes and M-phase vanadium dioxide are uniformly dispersed to form a three-dimensional porous structure. This structure can promote the transport of electrolyte, reduce the strain effect during ion intercalation, and reduce the influence of side reactions in the electrode process; and the carbon source (carbon nanotubes) and M-phase vanadium dioxide are evenly distributed, avoiding heat treatment. agglomeration of metals in the process. The positive electrode material of the aqueous zinc ion battery prepared by the method of the invention has the advantages of good rate performance, good stability and high Coulombic efficiency. The raw materials are all commercial materials, the preparation conditions are safe and simple, easy to control and environmentally friendly, the process conditions are low in cost, the preparation efficiency is high, the environment is friendly, the product quality and yield are high, suitable for low-carbon economy, and has good application and industrialization prospects. .

(2) The carbon nanotube/M-phase vanadium dioxide composite structure prepared by the present invention can be used in many fields such as high-efficiency energy storage and conversion, catalytic conversion, material adsorption and separation, and the like. The synthesis process of the composite structure does not involve strong acid and alkali, the synthesis technology is simple and controllable, and has a good application prospect.

Description of drawings

1 is a ball-and-stick model diagram of M-phase vanadium dioxide in the carbon nanotube/M-phase vanadium dioxide composite structure prepared by the present invention.

FIG. 2 is an X-ray powder diffraction (XRD) pattern of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 1. FIG.

In Fig. 3 (a) is a scanning electron microscope (SEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Examples 1, 5, and 9; (b) is the carbon nanotubes prepared in Examples 2, 3, and 4. Scanning electron microscope (SEM) image of the tube/M-phase vanadium dioxide composite structure; (c) is the scanning electron microscope (SEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Examples 6, 7, and 8.

FIG. 4 is a transmission electron microscope (TEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 2. FIG.

5 is a high-resolution lens (HRTEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 2. FIG.

FIG. 6 shows the rate performance performance of the carbon nanotube/M-phase vanadium dioxide composite structures prepared in Examples 1, 5, and 9 for use as a cathode material for an aqueous zinc-ion battery.

FIG. 7 shows the rate performance performance of the carbon nanotube/M-phase vanadium dioxide composite structures prepared in Examples 2, 3, and 4 for use as a cathode material for an aqueous zinc-ion battery.

FIG. 8 shows the rate performance performance of the carbon nanotube/M-phase vanadium dioxide composite structures prepared in Examples 6, 7, and 8 for use as a cathode material for an aqueous zinc-ion battery.

9 is a graph showing the stability test results of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 2 used in an aqueous zinc-ion battery.

Detailed ways

The present invention will be described in further detail below by means of an example of implementation. This example is implemented on the premise of the technology of the present invention. Now, the detailed implementation and specific operation process are given to illustrate the inventiveness of the present invention, but the protection scope of the present invention is not limited to the following examples of implementation.

From the information contained in this application, various changes to the precise description of the present invention can be readily made by those skilled in the art without departing from the spirit and scope of the appended claims. It is to be understood that the scope of the invention is not limited to the processes, properties or components defined, as these embodiments and other descriptions are intended to be illustrative only of particular aspects of the invention. Indeed, various modifications of the embodiments of the invention that are obvious to those skilled in the art or related fields are intended to be within the scope of the appended claims.

For a better understanding of the invention and not to limit the scope of the invention, all numbers expressing amounts, percentages, and other numerical values used in this application should in all cases be understood as modified by the word "about". Accordingly, unless expressly stated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At a minimum, each numerical parameter shall be deemed to have been obtained from the reported significant digits and by conventional rounding methods.

VO ₂ has a wide range of applications in optical devices, electronic devices and optoelectronic devices. Whereas in M _- phase VO2, the vanadium atoms are paired along the chain, resulting in unit cell doubling. The V atoms have staggered lateral displacements, and the oxygen octahedra are distorted (RM Wentzcovitch, et al., Physical Review Letters, 1994, 72, 3389-3392). This structure has denser ion intercalation channels and higher space utilization, which facilitates ion migration and further improves rate performance.

The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

The carbon nanotubes used in the following examples of the present invention were purchased from Suzhou Hengqiu Graphene Technology Co., Ltd., and the vanadium pentoxide (V ₂ O ₅ ) used was purchased from Saen Chemical Technology (Shanghai) Co., Ltd.

Example 1

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 60 mg of carbon nanotubes to 40 ml of deionized water and sonicate the needle tip for 8 minutes to obtain suspension 1, and then add 2 mmol of vanadium pentoxide and 5 ml of 30% hydrogen peroxide aqueous solution to the above suspension 1. , and stirred for 30 min to obtain suspension 2. Then, the above suspension 2 was sealed in a PTFE-lined reaction kettle and reacted at a constant temperature of 180 °C for 8 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours. Get primary products. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 600 °C at a heating rate of 15 °C/min, and was roasted at a constant temperature at 600 °C in an argon flow for 2 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 250 mL/min.

Example 2

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

90mg of carbon nanotubes were added to 45ml of deionized water and the needle tip was sonicated for 12 minutes to obtain suspension 1, and then 1mmol of vanadium pentoxide and 5ml of 30% hydrogen peroxide aqueous solution were sequentially added to the above suspension 1. , and stirred for 40 min to obtain suspension 2. Then, the above suspension 2 was sealed in a PTFE-lined reactor and reacted at a constant temperature at 200 °C for 12 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours. Get primary products. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 650 °C at a heating rate of 25 °C/min, and was roasted at a constant temperature of 650 °C in an argon flow for 2 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 100 mL/min.

Example 3

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

90mg of carbon nanotubes were added to 40ml of deionized water and the needle tip was sonicated for 8 minutes to obtain suspension 1, and then 3mmol of vanadium pentoxide and 10ml of 30% hydrogen peroxide aqueous solution were sequentially added to the above suspension 1. , and stirred for 20 min to obtain suspension 2. The above-mentioned suspension 2 was sealed in a PTFE-lined reactor and reacted at a constant temperature of 185 °C for 11 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours to obtain primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 660 °C at a heating rate of 20 °C/min, and was roasted at a constant temperature of 660 °C in an argon flow for 2 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 200 mL/min.

Example 4

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 30 mg of carbon nanotubes to 50 ml of deionized water and sonicate the needle tip for 15 minutes to obtain suspension 1, and then add 2 mmol of vanadium pentoxide and 10 ml of 30% hydrogen peroxide aqueous solution to the above suspension 1 in turn , and stirred for 90 min to obtain suspension 2. The above-mentioned suspension 2 was sealed in a PTFE-lined reactor and reacted at a constant temperature at 180 °C for 10 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours to obtain primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 580 °C at a heating rate of 10 °C/min, and was roasted at a constant temperature of 580 °C in an argon flow for 2 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 10 mL/min.

Example 5

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 30 mg of carbon nanotubes to 40 ml of deionized water and sonicate the needle tip for 20 minutes to obtain suspension 1, and then 1 mmol of vanadium pentoxide and 5 ml of 30% hydrogen peroxide aqueous solution were sequentially added to the above suspension 1. , and stirred for 15 min to obtain suspension 2. The above suspension 2 was sealed in a PTFE-lined reaction kettle for 15 hours at a constant temperature of 160 °C. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours to obtain primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 500 °C at a heating rate of 1 °C/min, and was roasted at a constant temperature of 500 °C in an argon flow for 3 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 500 mL/min.

Example 6

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 60 mg of carbon nanotubes to 50 ml of deionized water and sonicate the needle tip for 8 minutes to obtain suspension 1, and then add 3 mmol of vanadium pentoxide and 10 ml of 30% hydrogen peroxide aqueous solution to the above suspension 1 in turn, After stirring for 60 min, suspension 2 was obtained. The above suspension was then sealed into a PTFE-lined reaction kettle for 16 hours at a constant temperature of 190 °C. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours. , get the primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 800 °C at a heating rate of 50 °C/min. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 100 mL/min.

Example 7

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

90mg of carbon nanotubes were added to 45ml of deionized water and the needle tip was sonicated for 18 minutes to obtain suspension 1. Then 2mmol of vanadium pentoxide and 10ml of 30% hydrogen peroxide aqueous solution were added to the above suspension 1 in turn. , and stirred for 120 min to obtain suspension 2. The above-mentioned suspension 2 was sealed in a PTFE-lined reactor and reacted at a constant temperature of 180 °C for 15 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours. Get primary products. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 700 °C at a heating rate of 5 °C/min, and was roasted at a constant temperature of 700 °C in an argon flow for 1.5 hours. After the end, a carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 50 mL/min.

Example 8

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 30 mg of carbon nanotubes to 20 ml of deionized water and sonicate the needle tip for 20 minutes to obtain suspension 1, then add 1 mmol of vanadium pentoxide and 5 ml of 30% hydrogen peroxide aqueous solution to the above suspension 1 in turn, After stirring for 50 min, suspension 2 was obtained. The above-mentioned suspension 2 was sealed in a PTFE-lined reactor and reacted at a constant temperature of 180 °C for 12 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours to obtain primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 550 °C at a heating rate of 5 °C/min, and was roasted at a constant temperature of 550 °C in an argon flow for 2.5 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; the flow rate of the argon gas is 300 mL/min.

Example 9

The preparation method of a carbon nanotube/M-phase vanadium dioxide composite structure of the present embodiment includes the following steps:

Add 60 mg of carbon nanotubes to 20 ml of deionized water and sonicate the needle tip for 20 minutes to obtain suspension 1, and then add 2 mmol of vanadium pentoxide and 5 ml of 30% hydrogen peroxide aqueous solution to the above suspension 1 in turn, After stirring for 60 min, suspension 2 was obtained. The above suspension was sealed in a PTFE-lined reactor and reacted at a constant temperature of 180 °C for 12 hours. After the reaction, the product was suction filtered and washed with deionized water at room temperature for several times, and then freeze-dried at -60 °C for 24 hours to obtain the primary product. Finally, 0.2 g of the above-mentioned primary product was placed in a porcelain boat, moved into a tube furnace, and the tube furnace was heated to 400 °C at a heating rate of 10 °C/min, and was roasted at a constant temperature of 400 °C in an argon flow for 4 hours. After the end, the carbon nanotube/M-phase vanadium dioxide composite structure is obtained; wherein: the purity of the argon gas is greater than or equal to 99.99%; and the flow rate of the argon gas is 200 mL/min.

Test Results:

The obtained material is characterized by XRD pattern, and FIG. 2 is an X-ray powder diffraction (XRD) pattern of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 1 above. As can be seen from this figure, the product, except for carbon, is VO ₂ in the M phase (PDF: 82-0661).

In Fig. 3 (a) is a scanning electron microscope (SEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Examples 1, 5, and 9; (b) is the carbon nanotubes prepared in Examples 2, 3, and 4. Scanning electron microscope (SEM) image of the tube/M-phase vanadium dioxide composite structure; (c) is the scanning electron microscope (SEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Examples 6, 7, and 8.

4 is a transmission electron microscope (TEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 2, and the TEM image shows that the vanadium dioxide is irregular particles.

5 is a high-resolution lens (HRTEM) image of the carbon nanotube/M-phase vanadium dioxide composite structure prepared in Example 2. FIG. The (011) and (200) crystal planes displayed by the HRTEM prove that the product is definitely M-phase VO ₂ .

Application Example 1

The carbon nanotube/M-phase vanadium dioxide composite structure prepared in the above-mentioned embodiments of the present invention can be used as a positive electrode material in an aqueous zinc-ion battery.

The water-based zinc-ion battery of this application example is composed of a positive electrode, a negative electrode, an electrolyte, a glass fiber separator arranged between the positive electrode and the negative electrode, and a CR2032 battery case; wherein: the negative electrode is a metal zinc sheet, and the electrolyte is 2MZnSO _4. The positive electrode is a composite structure sample of carbon nanotube/M-phase vanadium dioxide as an active material, a poly(tetrafluoroethylene) (PTFE) suspension (60 wt%) as a binder, and acetylene as a conductive additive The black is mixed with a weight ratio of 8:1:1 and then coated on the surface of the copper foil to form.

The above-mentioned water-based zinc-ion battery is specifically prepared by assembling the positive electrode, negative electrode, electrolyte and separator into a battery case, and its specific capacity is tested by Blue Electric CT2001A.

As shown in Figures 6, 7, and 8, the carbon nanotube/M-phase vanadium dioxide composite structure prepared in each example is used for the rate performance performance of the cathode material of the aqueous zinc-ion battery, and has 248mAh·g at 2A·g ^-1 The specific capacity of ^-1 still retains 232.6mAh·g ^-1 at a large current density of 20A·g ^-1 , which has a specific capacity retention rate of 93.8% compared to 2A·g ^-1 . It can also maintain a specific capacity of 194.9mAh·g ^-1 at 40A·g ^-1 , and has an ultra-high rate capability. As shown in Fig. 9, in the further stability test, the carbon nanotube/M-phase vanadium dioxide composite structure prepared by the present invention still has 196.1mAh g-1 after 5000 cycles at a large current density of 20A·g ^{- 1} The specific capacity (85% retention rate) shows good stability.

In summary, the carbon nanotube/M-phase vanadium dioxide composite structure of the present invention exhibits excellent rate performance and good stability as a cathode material for an aqueous zinc-ion battery.

The invention uses carbon nanotubes as a three-dimensional frame, which promotes the transmission of electrolyte, reduces the strain effect during ion intercalation, and reduces the influence of side reactions in the electrode process; and the carbon source and metal salt are evenly distributed, avoiding the heat treatment process. Aggregation of metals; the prepared carbon nanotube/M-phase vanadium dioxide composite structure exhibits good rate capability and outstanding cycling stability in aqueous zinc-ion battery tests. The systematic study of this method can not only provide a novel vanadium-based aqueous zinc ion cathode material, but also have broad significance for the synthesis methodology of the material and the design of other battery cathode materials.

Claims (8)

1. A carbon nano tube/M-phase vanadium dioxide composite structure is characterized in that: the composite structure comprises a carbon nano tube and M-phase vanadium dioxide nano particles, wherein: the M-phase vanadium dioxide nanoparticles are uniformly distributed in the hollow cavity of the carbon nano tube and on the surface of the 3D network structure of the carbon nano tube; the carbon nano tube/M-phase vanadium dioxide composite structure is prepared by the following method, and the method comprises the following steps:

(1) dispersed carbon nanotubes

Adding carbon nanotubes into the dispersion liquid, and performing needle point ultrasound to obtain a suspension 1;

(2) dissolving vanadium pentoxide

Adding vanadium pentoxide into the suspension 1 in the step (1), then adding a small amount of aqueous hydrogen peroxide solution, and uniformly stirring to obtain a suspension 2;

(3) high temperature hydrothermal process

Sealing the suspension 2 in the step (2) into a Polytetrafluoroethylene (PTFE) lining, placing the lining into a reaction kettle, reacting for 2-24 hours at 120-240 ℃, and naturally cooling to room temperature after the reaction is finished;

(4) preparation of carbon nanotube/M-phase vanadium dioxide composite structure

Carrying out suction filtration, cleaning and freeze drying on the product in the reaction kettle in the step (3) to obtain a primary product; then transferring the primary product into a high-temperature reaction furnace, raising the temperature of the reaction furnace to 400-800 ℃ under the condition of protective gas, and then continuously reducing for 0.1-36 h under the conditions of gas protection and constant temperature of 400-800 ℃ to obtain the carbon nano tube/M-phase vanadium dioxide composite structure;

the dosage ratio of the carbon nano tube in the step (1) to the vanadium pentoxide in the step (2) is (10-100) mg: (1-3) mmol.

2. The carbon nanotube/M-phase vanadium dioxide composite structure of claim 1, wherein: the dosage ratio of the vanadium pentoxide to the aqueous hydrogen peroxide solution in the step (2) is (1-3) molar parts: (0.1-10) parts by volume, wherein: the molar parts and the volume parts are based on mmol and mL.

3. The carbon nanotube/M-phase vanadium dioxide composite structure of claim 1, wherein: the temperature rise rate of the high-temperature reaction furnace is 0.1-50 ℃/min.

4. The carbon nanotube/M-phase vanadium dioxide composite structure of claim 1, wherein: the flow rate of the protective gas is 5-500 mL/min.

5. The use of the carbon nanotube/M-phase vanadium dioxide composite structure of any one of claims 1 to 4 as a positive electrode material in an aqueous zinc-ion battery.

6. A positive electrode material for a water-based zinc-ion battery, characterized in that: the positive electrode material includes a positive electrode active material and a binder, wherein: the positive electrode active material is the carbon nanotube/M-phase vanadium dioxide composite structure according to any one of claims 1 to 4.

7. A positive electrode for a water-based zinc ion battery, characterized in that: the positive electrode comprises a current collector and a positive electrode material coated and/or filled on the current collector, wherein: the positive electrode material is the aqueous zinc-ion battery positive electrode material according to claim 6.

8. An aqueous zinc-ion battery characterized in that: comprising a positive electrode and a negative electrode, a separator provided between the positive electrode and the negative electrode, and an aqueous electrolyte, wherein: the positive electrode is the aqueous zinc-ion battery positive electrode according to claim 7; the negative electrode is a metal zinc sheet, and the aqueous electrolyte is an aqueous solution containing a zinc salt electrolyte.

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