Carbon-coated vanadium dioxide nano material as well as preparation method and application thereof
By preparing carbon-coated vanadium dioxide nanomaterials in lithium-ion capacitor batteries, the problems of aggregation, volume expansion and impedance increase of VO2 materials in the battery are solved, simplified the synthesis process, and significantly improved the rate performance and cycle stability of the battery.
Patent Information
- Application Number
- CN202411760446.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-04-04
AI Technical Summary
The existing VO2 materials have problems of increasing impedance during aggregation, volume expansion and charging and discharge in lithium-ion capacitor batteries, and the introduction and recombination process of carbon materials is cumbersome, which increases the difficulty of synthesis.
The tetravalent vanadium solution was obtained by reducing the vanadium source under the action of a reducing agent and hydrothermal reaction with sodium alginate to prepare a carbon-coated vanadium dioxide nanomaterial. Sodium alginate not only acts as a carbon source, but also limits the growth of VO2 crystals and simplifies the synthesis process.
The prepared carbon-coated vanadium dioxide nanomaterial has a high specific surface area and excellent conductivity, which significantly improves the rate performance and cycle stability of lithium-ion capacitor batteries, and the discharge specific capacity can reach 90mAh/g.
Smart Images
Figure CN119750646A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of nanomaterials, and in particular to a carbon-coated vanadium dioxide nanomaterial and a preparation method and application thereof. Background Art
[0002] Lithium-ion capacitors combine the advantages of lithium-ion batteries and supercapacitors in their design to achieve high energy and power density as well as fast charging performance and long cycle life. Among many materials, vanadium-based materials such as V2O5, LiV3O8, VO2(B) and Li3V2(PO4)3 are compounds with intercalation chemistry characteristics, and their layered or open framework structures allow simple ion movement. This ideal structure allows reversible lithium absorption / release and is structurally flexible, providing multiple channels for lithium ion insertion and deintercalation, thereby achieving excellent specific capacity. Among various vanadium oxides, the metastable monoclinic VO2 (B) is a layered structure formed by shared edges. During the charge storage process, this unique structure provides a large number of channels that can enter the vanadium dioxide bulk phase, promoting the insertion and deintercalation reactions of lithium ions, thereby obtaining excellent electrochemical performance.
[0003] However, VO2 still has problems such as self-aggregation, volume expansion, and increased impedance during charging and discharging. The most direct way to solve these problems is to compound VO2 with carbon materials, but the introduction of carbon materials usually involves tedious experimental processes, which increases the difficulty of synthesis. Summary of the invention
[0004] In view of this, the technical problem to be solved by the present invention is to provide a carbon-coated vanadium dioxide nanomaterial and a preparation method and application thereof. The prepared carbon-coated vanadium dioxide nanomaterial has a simple synthesis method and excellent electrochemical performance.
[0005] To achieve the above object, the present invention provides a method for preparing a carbon-coated vanadium dioxide nanomaterial, comprising the following steps:
[0006] Reducing the vanadium source under the action of a reducing agent to obtain a tetravalent vanadium solution;
[0007] The tetravalent vanadium solution and sodium alginate are mixed to undergo a hydrothermal reaction to obtain carbon-coated vanadium dioxide nanoparticles.
[0008] The present invention first reduces the vanadium source compound to obtain a blue tetravalent vanadium solution.
[0009] The solvent of the solution is preferably water.
[0010] Preferably, the vanadium source is selected from one or more of vanadium pentoxide, ammonium metavanadate, and ammonium polyvanadate.
[0011] Preferably, the reducing agent is selected from one or more of ethylene glycol, oxalic acid, citric acid and tartaric acid.
[0012] Preferably, the vanadium source is an aqueous solution of a vanadium source.
[0013] In the aqueous solution of the vanadium source, the concentration of the vanadium source is preferably 0.1 to 0.5 mol / L, more preferably 0.3 to 0.5 mol / L.
[0014] The amount of the reducing agent is preferably 5% to 20% in excess of the stoichiometric ratio, more preferably 10% to 20% in excess, and further preferably 20% in excess.
[0015] The reduction temperature is preferably 90-100° C., more preferably 90° C.; the reduction time is preferably 2-4 h, more preferably 2 h.
[0016] Then the tetravalent vanadium solution and sodium alginate are mixed to carry out a hydrothermal reaction.
[0017] The present invention uses sodium alginate as a carbon source and can limit the growth of VO2 crystals to prepare carbon-coated VO2 nanorods.
[0018] The sodium alginate is preferably in the form of sodium alginate hydrogel.
[0019] The present invention has no particular limitation on the preparation method of the sodium alginate hydrogel, which may be a method well known to those skilled in the art. In some specific embodiments of the present invention, the sodium alginate hydrogel is preferably obtained by mixing sodium alginate and water at 60-90° C. for 2-4 hours.
[0020] The mass fraction of the sodium alginate hydrogel is preferably 5% to 10%.
[0021] During the hydrothermal reaction, the concentration of sodium alginate in the reaction system is preferably 1 wt% to 5 wt%.
[0022] The pH value of the hydrothermal reaction is preferably 5-8.
[0023] In the present invention, an alkaline compound can be used to adjust the pH value of the system, and the alkaline compound is preferably NaOH, KOH, etc.
[0024] The temperature of the hydrothermal reaction is preferably 120-180° C., more preferably 160-180° C.; the time of the hydrothermal reaction is preferably 8-16 h, more preferably 10-12 h.
[0025] Preferably, in the present invention, after the hydrothermal reaction is completed, the obtained nanomaterial is filtered, washed and dried to obtain the carbon-coated vanadium dioxide nanomaterial.
[0026] The drying temperature is preferably 50-70° C., more preferably 60° C.; the drying time is preferably 8-12 h, more preferably 10 h.
[0027] The present invention has no particular limitation on the drying method, and it may be a drying method well known to those skilled in the art. The present invention preferably uses vacuum drying.
[0028] The carbon-coated vanadium dioxide nanomaterial prepared by the invention has the morphology of nanorods with a diameter of 10-30 nm and a length of 40-100 nm.
[0029] The present invention also provides a carbon-coated vanadium dioxide nanomaterial prepared by the above preparation method.
[0030] The carbon-coated vanadium dioxide nanomaterial provided by the present invention has a high specific surface area and excellent electrical conductivity, and can effectively improve the rate performance and cycle stability of aqueous zinc ion batteries.
[0031] Based on this, the present invention provides a battery positive electrode material, including the carbon-coated vanadium dioxide nanomaterial prepared by the above preparation method.
[0032] The present invention has no special limitation on other components of the above-mentioned battery positive electrode material, which may be components generally applicable to battery positive electrode materials, including but not limited to polyvinylidene fluoride (PVDF), Ketjen black, etc.
[0033] The present invention also provides a battery, comprising the above-mentioned battery positive electrode material.
[0034] The present invention has no special limitation on the electrolyte of the above-mentioned battery, and it can be a general electrolyte well known to those skilled in the art, including but not limited to LiPF6 and the like.
[0035] The present invention has no special limitation on the counter electrode material of the above-mentioned battery, and it can be a common counter electrode material well known to those skilled in the art, including but not limited to lithium sheet.
[0036] Compared with the prior art, the present invention provides a method for preparing a carbon-coated vanadium dioxide nanomaterial, comprising the following steps: reducing a vanadium source under the action of a reducing agent to obtain a 4-valent vanadium solution; and subjecting the 4-valent vanadium solution and sodium alginate to a hydrothermal reaction to obtain carbon-coated vanadium dioxide nanoparticles.
[0037] The present invention adopts sodium alginate as the carbon source, which can limit the growth of VO2 crystals. The prepared carbon-coated vanadium dioxide nanomaterial has a high specific surface area and excellent electrical conductivity, and can effectively improve the rate performance and cycle stability of aqueous zinc ion batteries. At a current density of 800mA / g, the specific capacity can reach 90mAh / g, which has a good prospect for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 is the XRD pattern of carbon-coated vanadium dioxide prepared in Example 1;
[0039] Figure 2 is a TEM image of carbon-coated vanadium dioxide prepared in Example 1;
[0040] Figure 3 This is a charge and discharge curve of the carbon-coated vanadium dioxide prepared in Example 1. DETAILED DESCRIPTION
[0041] In order to further illustrate the present invention, the following is a detailed description in conjunction with the embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.
[0042] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.
[0043] Example 1
[0044] Take a certain amount of vanadium pentoxide powder and disperse it in a certain amount of deionized water, and control the molar concentration to 0.3 mol / L; then add a certain amount of ethylene glycol as a reducing agent, with an excess of 20% according to the stoichiometric ratio, and then heat to 90°C and stir for 2 hours to form a blue solution A, dissolve sodium alginate in deionized water, stir at 60°C for 2 hours, and prepare a 10wt% sodium alginate hydrogel solution B; add 1 volume of solution B to 1 volume of solution A under stirring, add 10wt% NaOH solution, adjust the solution pH to 5, and transfer the solution to a hydrothermal reactor and react at 160°C for 10 hours. After filtering, washing, and vacuum drying at 60°C for 10 hours, carbon-coated VO2 with a diameter of 10nm and a length of 40nm is obtained.
[0045] According to the mass ratio of 8:1:1, the prepared carbon-coated nano-VO2, polyvinylidene fluoride (PVDF), and Ketjen black were mixed and slurried to prepare the positive electrode material, 1.0 M LiPF6 was used as the electrolyte, and the lithium sheet was used as the counter electrode to assemble the battery. At a current density of 800mA / g, the discharge specific capacity was 75mAh / g.
[0046] Figure 1 is the XRD pattern of carbon-coated vanadium dioxide prepared in Example 1, Figure 1 It can be seen that the diffraction peaks of the prepared VO2 coincide with the diffraction peaks of PDF card number 31-1438, and there are no impurity peaks, indicating that the prepared phase is VO2 (B).
[0047] Figure 2 is a TEM image of carbon-coated vanadium dioxide prepared in Example 1. Figure 2 It can be seen that the prepared VO2 nanorods have uniform particle size distribution, with a length of 30-50nm and a diameter of 10-20nm.
[0048] Figure 3 is the charge and discharge curve of carbon-coated vanadium dioxide prepared in Example 1, Figure 3 It can be seen that the prepared VO2 has good rate performance.
[0049] Example 2
[0050] Take a certain amount of ammonium metavanadate powder and disperse it in a certain amount of deionized water, and control the molar concentration to be 0.5mol / L; then add a certain amount of oxalic acid as a reducing agent, with an excess of 20% according to the stoichiometric ratio, and then heat to 90℃ and stir for 2h to form a blue solution A, dissolve sodium alginate in deionized water, stir at 60℃ for 2h, and prepare a 10wt% sodium alginate hydrogel solution B; add 1 volume of solution B to 2 volumes of solution A under stirring, add 10wt% NaOH solution, adjust the solution pH to 8, and transfer the solution to a hydrothermal reactor and react at 160℃ for 12h. After filtering, washing, and vacuum drying at 60℃ for 10h, carbon-coated VO2 with a diameter of 20nm and a length of 60nm is obtained. 。
[0051] According to the mass ratio of 8:1:1, the prepared carbon-coated nano-VO2, polyvinylidene fluoride (PVDF), and Ketjen black were mixed and slurried to prepare the positive electrode material, 1.0 M LiPF6 was used as the electrolyte, and the lithium sheet was used as the counter electrode to assemble the battery. At a current density of 800mA / g, the discharge specific capacity was 90mAh / g.
[0052] Example 3
[0053] Take a certain amount of ammonium polyvanadate powder and disperse it in a certain amount of deionized water, and control the molar concentration to be 0.4 mol / L; then add a certain amount of citric acid as a reducing agent, with an excess of 20% according to the stoichiometric ratio, and then heat to 90°C and stir for 2 hours to form a blue solution A, dissolve sodium alginate in deionized water, stir at 60°C for 2 hours, and prepare a 10wt% sodium alginate hydrogel solution B; add 1 volume of solution B to 3 volumes of solution A under stirring, add 10wt% NaOH solution, adjust the solution pH to 8, and transfer the solution to a hydrothermal reactor and react at 180°C for 12 hours. After filtering, washing, and vacuum drying at 60°C for 10 hours, carbon-coated VO2 with a diameter of 15nm and a length of 100nm is obtained.
[0054] According to the mass ratio of 8:1:1, the prepared carbon-coated nano-VO2, polyvinylidene fluoride (PVDF), and Ketjen black were mixed and slurried to prepare the positive electrode material, 1.0 M LiPF6 was used as the electrolyte, and the lithium sheet was used as the counter electrode to assemble the battery. At a current density of 800mA / g, the discharge specific capacity was 88mAh / g.
[0055] The above embodiments are only used to help understand the method and core idea of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a carbon-coated vanadium dioxide nanomaterial, comprising the following steps: Reducing the vanadium source under the action of a reducing agent to obtain a tetravalent vanadium solution; The tetravalent vanadium solution and sodium alginate are mixed to undergo a hydrothermal reaction to obtain carbon-coated vanadium dioxide nanoparticles.
2. The preparation method according to claim 1, characterized in that: The vanadium source is selected from one or more of vanadium pentoxide, ammonium metavanadate, and ammonium polyvanadate.
3. The preparation method according to claim 1, characterized in that: The reducing agent is selected from one or more of ethylene glycol, oxalic acid, citric acid and tartaric acid.
4. The preparation method according to claim 1, characterized in that: The vanadium source is an aqueous solution of a vanadium source; In the aqueous solution of the vanadium source, the concentration of the vanadium source is 0.1-0.5 mol / L.
5. The preparation method according to claim 1, characterized in that: The amount of the reducing agent used is 5% to 20% in excess according to the stoichiometric ratio.
6. The preparation method according to claim 1, characterized in that: The reduction temperature is 90-100° C., and the reduction time is 2-4 hours.
7. The preparation method according to claim 1, characterized in that: The sodium alginate is sodium alginate hydrogel; The sodium alginate hydrogel is obtained by mixing sodium alginate and water at 60-90° C. for 2-4 hours; The mass fraction of the sodium alginate hydrogel is 5% to 10%.
8. The preparation method according to claim 1, characterized in that: During the hydrothermal reaction, the concentration of sodium alginate in the reaction system is 1wt%~5wt%; The pH value of the hydrothermal reaction is 5-8; The temperature of the hydrothermal reaction is 120-180° C., and the time of the hydrothermal reaction is 8-16 hours.
9. The carbon-coated vanadium dioxide nanomaterial prepared by the preparation method according to any one of claims 1 to 8.
10. A battery positive electrode material, comprising a carbon-coated vanadium dioxide nanomaterial prepared by the preparation method according to any one of claims 1 to 8.