A CNT / VOOH composite material and its preparation method and application

Abstract

The present invention provides a CNT / VOOH composite material and its preparation method and application, belonging to the field of electrochemical material technology, comprising the following steps: (1) mixing carbon nanotubes with concentrated acid, heating, cooling, filtering, washing and drying to obtain acidified carbon nanotubes; (2) dispersing the carbon nanotubes described in step (1) in water, ultrasonically dispersing, adding a vanadium source and a sulfur source, adding ammonia water and stirring until the vanadium source is dissolved, to obtain a mixed solution; (3) pouring the mixed solution described in step (2) into a hydrothermal kettle for hydrothermal reaction; (4) after the hydrothermal reaction described in step (3) is completed, the hydrothermal kettle is cooled, the cooled product after the reaction is taken out, washed with a mixed solution of water and ethanol, and then dried to obtain a CNT / VOOH composite material. The present invention uses carbon nanotubes as a reaction medium, which not only increases the conductivity of the material, but also restricts the morphological growth of VOOH, generates oxygen vacancies, and greatly optimizes the electrochemical performance of VOOH.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical materials, and in particular relates to a CNT / VOOH composite material and a preparation method and application thereof. Background Art

[0002] Over the past few decades, lithium-ion batteries have been involved in all aspects of human life, such as electric vehicles and digital products. However, the increasing prices of lithium salts and lithium cathodes in recent years have forced researchers to look for new alternative batteries. Aqueous zinc-ion batteries (AZIBs) have become an attractive candidate for smart grids and large-scale energy storage systems (ESS) due to their high theoretical mass capacity (820 mA hg -1 ) and volume capacity (5855mAh cm -3 ), low energy storage cost, high safety and high ionic conductivity, etc. However, the development of AZIBs is limited by the advanced cathode with high energy density and long cycle life.

[0003] In recent years, a large number of cathode materials have been studied for use in the cathode of zinc-ion batteries, such as manganese-based materials, Prussian blue analogs and vanadium-based materials. Due to the natural abundance and multiple oxidation states of vanadium, vanadium-based compounds have been reported as potential host materials for AZIBs. VOOH material is a typical vanadium-based phase change material. It has great potential as a cathode material for zinc-ion batteries, but it has rarely been studied and reported. Wang et al. synthesized lepidocrocite VOOH hollow nanospheres, achieved good electrochemical performance, and proved that VOOH to Zn 0.3 The transformation of V2O5·nH2O and then Zn 2+ and H + Co-intercalation reaction mechanism. Zhang et al. prepared three different configurations of VOOH, among which rhombic VOOH showed the best electrochemical performance. -1 The capacity after 5000 cycles is 270mAh g -1 , and proposed that VOOH should be converted to Zn 0.36 The phase transition mechanism of V2O5·nH2O and Zn3(OH)2V2O7·2H2O is shown. It is worth noting that in this work, montroseite VOOH only exhibits a capacity of <100 mAh g -1 Specific capacity. There are no other reports on monoclinic VOOH in ZIBs. The advantage of VOOH's in-situ conversion to vanadium bronze warrants further attention from researchers. However, VOOH exhibits poor conductivity and structural stability, and different VOOH structures exhibit distinct reaction and failure mechanisms, making further improvements in capacity and cycling stability a major challenge. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a CNT / VOOH composite material and its preparation method and application. The CNT / VOOH composite material provided by the present invention not only increases the conductivity through carbon tubes and enriches oxygen vacancies, but also forms a novel morphology structure. The cathode of the CNT / VOOH material of the present invention is 10Ag -1 It has demonstrated a cycle life of 8500 times while maintaining a capacity of 205 mAhg. -1 High reversible capacity at 20Ag -1 Even at high current density, it still has 277mAhg -1 Rate performance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a CNT / VOOH composite material, comprising the following steps:

[0007] (1) mixing carbon nanotubes with concentrated acid, heating, cooling, filtering, washing, and drying to obtain acidified carbon nanotubes;

[0008] (2) dispersing the carbon nanotubes described in step (1) in water, ultrasonically dispersing, adding a vanadium source and a sulfur source, adding ammonia water and stirring until the vanadium source is dissolved, to obtain a mixed solution;

[0009] (3) pouring the mixed solution described in step (2) into a hydrothermal kettle for hydrothermal reaction;

[0010] (4) After the hydrothermal reaction in step (3) is completed, the hydrothermal reactor is cooled, and the product after the reaction is cooled is taken out, washed with a mixture of water and ethanol, and then dried to obtain a CNT / VOOH composite material.

[0011] Preferably, the heating temperature in step (1) is 80 to 170° C., and the heating time is 1 to 12 hours.

[0012] Preferably, the concentrated acid in step (1) is concentrated sulfuric acid and / or concentrated nitric acid.

[0013] Preferably, the ultrasonication time in step (2) is 1 to 5 hours; and the stirring time is 1 to 3 hours.

[0014] Preferably, in step (2), the vanadium source is sodium vanadate and / or ammonium vanadate; and the sulfur source is thioacetamide and / or thiourea.

[0015] Preferably, the millimole ratio of the vanadium source to the sulfur source in step (2) is 2-4:15-30 mmol.

[0016] Preferably, the conditions for the hydrothermal reaction in step (3) are: maintaining at 170-200° C. for 20-48 hours.

[0017] Preferably, the volume ratio of water to ethanol in step (4) is 1-2:1-5.

[0018] The present invention also provides a CNT / VOOH composite material prepared by the above preparation method.

[0019] The present invention also provides the use of the CNT / VOOH composite material prepared by the above preparation method in preparing the positive electrode of an aqueous zinc ion battery.

[0020] The CNT / VOOH composite material provided by the present invention not only increases the conductivity through carbon tubes and enriches oxygen vacancies, but also forms a novel morphology structure. -1 It has demonstrated a cycle life of 8500 times while maintaining a capacity of 205 mAhg. -1 High reversible capacity at 20Ag -1 Even at high current density, it still has 277mAhg -1 Rate performance. CNT / VOOH is a promising cathode material in ZIBs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD pattern of the CNT / VOOH composite material prepared in Example 1 of the present invention;

[0022] Figure 2 This is a scanning electron microscope (SEM) image of the CNT / VOOH composite material prepared in Example 1 of the present invention;

[0023] Figure 3 This is a scanning electron microscope image of VOOH prepared in Comparative Example 1 of the present invention;

[0024] Figure 4 This is a high-resolution transmission electron microscopy (HRTEM) image of the CNT / VOOH composite material prepared in Example 1 of the present invention;

[0025] Figure 5 This is a rate performance diagram of the CNT / VOOH composite material prepared in Example 1 of the present invention;

[0026] Figure 6 A comparison chart of the rate performance of the CNT / VOOH composite material prepared in Example 1 of the present invention and the vanadium-based material in the prior art;

[0027] Figure 7 The CNT / VOOH composite material prepared in Example 1 of the present invention was heated to 1Ag. -1 Cycle performance diagram;

[0028] Figure 8 This is a long cycle performance diagram of the CNT / VOOH composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a CNT / VOOH composite material, comprising the following steps:

[0030] (1) mixing carbon nanotubes with concentrated acid, heating, cooling, filtering, washing, and drying to obtain acidified carbon nanotubes;

[0031] (2) dispersing the carbon nanotubes described in step (1) in water, ultrasonically dispersing, adding a vanadium source and a sulfur source, adding ammonia water and stirring until the vanadium source is dissolved, to obtain a mixed solution;

[0032] (3) pouring the mixed solution described in step (2) into a hydrothermal kettle for hydrothermal reaction;

[0033] (4) After the hydrothermal reaction in step (3) is completed, the hydrothermal reactor is cooled, and the product after the reaction is cooled is taken out, washed with a mixture of water and ethanol, and then dried to obtain a CNT / VOOH composite material.

[0034] In the present invention, in the above step (1), the carbon nanotubes are preferably multi-walled carbon nanotubes, single-walled carbon nanotubes or single-walled carbon nanotube bundles; the diameter of the carbon nanotubes is preferably 10 to 80 nm, more preferably 40 to 60 nm, and most preferably 50 nm.

[0035] In the present invention, in step (1), the concentrated acid is preferably concentrated sulfuric acid and / or concentrated nitric acid; the mass concentration of the concentrated nitric acid is preferably 63-68%, more preferably 65%; the mass concentration of the concentrated sulfuric acid is not less than 70%. In the present invention, the concentrated nitric acid and concentrated sulfuric acid are preferably mixed in a volume ratio of 1:1-3.

[0036] In the present invention, in the above step (1), the heating temperature is preferably 80-170°C, more preferably 90-160°C, and most preferably 140°C; the heating time is preferably 1-12h, more preferably 5-10h, and most preferably 6h.

[0037] In the present invention, in the above step (1), the cooling, filtering, washing and drying methods are not particularly limited and can be carried out using conventional methods in the art. In the washing method, deionized water is preferably used for washing until neutral.

[0038] In the present invention, in the above step (2), the mass volume ratio of the carbon nanotubes to water is preferably 10-20 mg: 30-60 ml. The ultrasonic dispersion time is preferably 1-5 hours.

[0039] In the present invention, in the above step (2), the vanadium source is preferably sodium vanadate and / or ammonium vanadate; the sulfur source is preferably thioacetamide and / or thiourea; and the millimole ratio of the vanadium source to the sulfur source is preferably 2-4:15-30 mmol.

[0040] In the present invention, in the above step (3), the mixed solution is preferably poured into the liner of the hydrothermal reactor and then sealed. After the liner is installed in the outer reactor and fixed, it is preferably kept at 170-200°C for 20-48h, more preferably at 180°C for 24h.

[0041] In the present invention, in step (4), the volume ratio of water to ethanol is preferably 1-2:1-5. The washing method is preferably filtration under vacuum conditions three times. The present invention is not particularly limited to the drying method, but is preferably dried at 60-80°C for 2-12 hours.

[0042] The present invention also provides a CNT / VOOH composite material prepared by the above preparation method.

[0043] The present invention also provides the use of the CNT / VOOH composite material prepared by the above preparation method in preparing the positive electrode of an aqueous zinc ion battery.

[0044] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1

[0046] A method for preparing a CNT / VOOH composite material comprises the following steps:

[0047] 1. Heat multi-walled carbon nanotubes (MWCNTs) with a diameter of approximately 40 nm in 65% concentrated nitric acid at 140°C for 6 hours, cool, filter, and wash with deionized water until neutral, then dry for later use.

[0048] 2.10 mg of acidified carbon nanotubes were dispersed in 30 ml of water. After ultrasonication for 1 h, 2 mmol of ammonium metavanadate and 15 mmol of thioacetamide were added. 2 ml of ammonia water was added and stirred for 1 h to obtain a suspension.

[0049] 3. The mixed solution was transferred to a 50 ml hydrothermal reactor and kept at 180 ° C for 24 hours.

[0050] 4. The reactor was naturally cooled to room temperature, and then the cooled product after the reaction was taken out, vacuum filtered three times with water: alcohol at a volume ratio of 1:2, and dried at 60°C for 10 hours.

[0051] The electrical properties of the CNT / VOOH composite material prepared in Example 1 are as follows: Figure 1-2 and Figure 4-8 As shown;

[0052] in Figure 1 The XRD curve of CNT / VOOH shown is in good agreement with that of VOOH (PDF#11-0152 - PDF card of the standard database) with no extraneous peaks;

[0053] Figure 2 The CNT / VOOH material is star-shaped composed of nanorods and wrapped by multi-walled tubes. The size of each particle is about 1-2 microns.

[0054] Figure 4 HRTEM will show the lattice structure of CNT / VOOH more clearly. The interplanar spacing of 0.196 corresponds to the (131) crystal plane of VOOH.

[0055] Figure 5 Between 0.1 and 0.5Ag -1 At low current densities of 1, 2, 5, and 10 A g, the capacities of CNT / VOOH and VOOH are almost the same. However, as the current density increases, the CNT / VOOH cathode exhibits better capacity retention. -1 The rate capacities are maintained at 434, 411, 380, and 352 mAh g -1 Even at 20Ag -1 At high rates, it still maintains 323mAhg -1 High specific capacity. When it returns to 0.1Ag -1 When the specific capacity can be restored to 465mAhg -1 On the other hand, the VOOH electrode exhibits lower rate capability at 5, 10, and 20 Ag. -1 The rate capacities are 341, 310 and 277 mAh g -1 ;

[0056] Figure 6 The rate capacity of CNT / VOOH is superior to most vanadium-based materials in the existing technology, further demonstrating the positive effect of CNT channels on the performance improvement of VOOH.

[0057] Figure 7 CNT / VOOH still showed the best cycling performance, 1Ag -1 After 200 cycles at a current density of 1000, the remaining capacity reaches 313 mAh g -1 , while VOOH only has 210mAhg left -1 ;

[0058] Figure 8 The CNT / VOOH electrode exhibits an extremely long cycle life at 10Ag-1 After 1000, 3000, 5000 and 8000 cycles, the battery capacities remained at 325, 284, 238 and 205 mAh g. -1 Furthermore, the CE of the electrode remains high at 99–100% throughout the entire cycling process.

[0059] Example 2

[0060] A method for preparing a CNT / VOOH composite material comprises the following steps:

[0061] 1. Heat multi-walled carbon nanotubes (MWCNTs) with a diameter of approximately 60 nm in 65% concentrated nitric acid at 120°C for 9 hours, cool, filter, and wash with deionized water until neutral, then dry for later use.

[0062] 2.10 mg of acidified carbon nanotubes were dispersed in 60 ml of water. After ultrasonication for 3 h, 2 mmol of sodium vanadate and 16 mmol of thiourea were added, followed by 2 ml of ammonia water. The mixture was stirred for 1 h to obtain a mixed solution.

[0063] 3. The mixed solution was transferred to an 80 ml hydrothermal reactor and maintained at 160 ° C for 48 h.

[0064] 4. The reactor was naturally cooled to room temperature, and then the cooled product after the reaction was taken out, vacuum filtered three times with water: alcohol at a volume ratio of 2:1, and dried at 60°C for 12 hours.

[0065] Example 3

[0066] A method for preparing a CNT / VOOH composite material comprises the following steps:

[0067] 1. Mix multi-walled carbon nanotubes with a diameter of about 100 nm in concentrated nitric acid and concentrated nitric acid in a ratio of 1:1. Heat in an oil bath at 90 degrees for 12 hours, cool, filter, and wash with deionized water until neutral. Dry and set aside.

[0068] 2.20 mg of acidified carbon nanotubes were dispersed in 30 ml of water. After ultrasonication for 3 h, 2 mmol of ammonium metavanadate and 15 mmol of thioacetamide were added. 2 ml of ammonia water was added and stirred for 1 h to obtain a suspension.

[0069] 3. The mixed solution was transferred to a 50 ml hydrothermal reactor and kept at 170 ° C for 30 hours.

[0070] The reactor was naturally cooled to room temperature, and the cooled product after the reaction was taken out, vacuum filtered three times with water:alcohol at a volume ratio of 1:1, and dried at 80°C for 6 hours.

[0071] Example 4

[0072] A method for preparing a CNT / VOOH composite material comprises the following steps:

[0073] 1. Mix single-walled carbon nanotubes (SWNTs) with a diameter of approximately 40 nm in concentrated nitric acid and concentrated sulfuric acid at a ratio of 1:3. Heat in an oil bath at 80°C for 12 hours, cool, filter, and wash with deionized water until neutral. Dry and set aside.

[0074] 2.20 mg of acidified carbon nanotubes were dispersed in 60 ml of water. After ultrasonication for 4 h, 4 mmol of ammonium metavanadate and 30 mmol of thioacetamide were added, followed by 2 ml of aqueous ammonia and stirring for 1 h to obtain a suspension.

[0075] 3. The mixed solution was transferred to an 80 ml hydrothermal reactor and kept at 200 ° C for 24 hours.

[0076] 4. The reactor was naturally cooled to room temperature, and then the cooled product after the reaction was taken out, vacuum filtered three times with water: alcohol at a volume ratio of 1:5, and dried at 80°C for 3 hours.

[0077] Comparative Example 1

[0078] 1. Add 2 mmol of ammonium metavanadate and dissolve it in 30 ml of water. Add 2 ml of ammonia water and 15 mmol of thioacetamide while stirring. Continue stirring for 1 hour to obtain a suspension.

[0079] 2. The mixed solution was transferred to a 50 ml hydrothermal reactor and kept at 180 ° C for 24 hours.

[0080] 3. The reactor was naturally cooled to room temperature, and the cooled product after the reaction was taken out, vacuum filtered three times with water: alcohol in a volume ratio of 1:2, and dried at 60°C for 10 hours.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a CNT / VOOH composite material, characterized in that: The following steps are involved: (1) mixing carbon nanotubes with concentrated acid, heating, cooling, filtering, washing and drying to obtain acidified carbon nanotubes, wherein the heating temperature is 80 to 170° C. and the heating time is 1 to 12 hours; (2) dispersing the carbon nanotubes described in step (1) in water, ultrasonically dispersing, adding a vanadium source and a sulfur source, adding ammonia water and stirring until the vanadium source is dissolved, to obtain a mixed solution; (3) pouring the mixed solution described in step (2) into a hydrothermal kettle for hydrothermal reaction; (4) After the hydrothermal reaction in step (3) is completed, the hydrothermal reactor is cooled, and the product after the reaction is cooled is taken out, washed with a mixture of water and ethanol, and then dried to obtain a CNT / VOOH composite material.

2. The preparation method according to claim 1, characterized in that The concentrated acid in step (1) is concentrated sulfuric acid and / or concentrated nitric acid.

3. The preparation method according to claim 1, characterized in that In the step (2), the ultrasonication time is 1 to 5 hours; and the stirring time is 1 to 3 hours.

4. The preparation method according to claim 1, characterized in that In the step (2), the vanadium source is sodium vanadate and / or ammonium vanadate; and the sulfur source is thioacetamide and / or thiourea.

5. The preparation method according to claim 1, characterized in that The millimole ratio of the vanadium source to the sulfur source in step (2) is 2-4:15-30.

6. The preparation method according to claim 1, characterized in that The conditions of the hydrothermal reaction in step (3) are: maintaining at 170-200° C. for 20-48 hours.

7. The preparation method according to claim 1, characterized in that The volume ratio of water to ethanol in step (4) is 1-2:1-5.

8. The CNT / VOOH composite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the CNT / VOOH composite material according to claim 8 in preparing a positive electrode for an aqueous zinc ion battery.

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