Vanadium-based nano-confined structure loaded nitrogen-doped carbon composite electrode material, and preparation method and application thereof

Abstract

This invention discloses a vanadium-based nanoconfined structure supported on nitrogen-doped carbon composite electrode material and its preparation and application. The material consists of a two-dimensional or near-two-dimensional nitrogen-doped carbon matrix and uniformly dispersed 1-10 nm vanadium-based nanostructures loaded on it. The carbon matrix achieves stable anchoring of the vanadium-based structure through spatial confinement. During electrochemical processes, the vanadium-based structure can transform into an amorphous vanadium oxide active phase, achieving energy storage through multi-ion insertion / extraction. Nitrogen-doped carbon not only provides a continuous conductive network but also enhances interface stability, regulates structural evolution, and alleviates structural distortion and dissolution problems caused by ion insertion in aqueous electrolytes. The preparation method involves compositing a vanadium source with a nitrogen-containing carbon precursor followed by heat treatment to construct the nanoconfined structure. The material of this invention exhibits high conductivity, good structural stability, and strong electrochemical reversibility, making it particularly suitable for aqueous secondary batteries. It demonstrates excellent rate performance and cycle stability in aqueous ammonium-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage materials technology, specifically to a vanadium-based nanoconfined structure supported nitrogen-doped carbon composite electrode material, its preparation method, and its application in aqueous secondary batteries. Background Technology

[0002] Vanadium-based oxides are considered promising electrode materials for aqueous energy storage systems due to their multivalent reversible redox properties, large interlayer spacing, and suitable potential windows. In recent years, aqueous ammonium-ion batteries have gradually become one of the emerging energy storage systems due to their high safety, low cost, and environmental friendliness. However, compared with traditional metal ion batteries (such as Li₂), they still face challenges in... + Na + ) different, NH4 + With its unique structure and chemical properties, NH4+ exhibits more complex behavior in electrochemical energy storage processes. On the one hand, NH4+... + It can interact with the host material through hydrogen bonding, and during insertion / deintercalation, it can easily cause local structural rearrangement or even lattice distortion; on the other hand, NH4 + The solvation structure in aqueous electrolytes is quite complex, and its intercalation process is usually accompanied by the synergistic effect of protons or solvent molecules, which further exacerbates the instability of the material structure.

[0003] Against this backdrop, the application of vanadium-based materials in aqueous ammonium-ion batteries still faces multiple challenges. First, vanadium-based materials have low intrinsic electronic conductivity, making them prone to significant polarization during charge and discharge, limiting rate performance. Second, vanadium is easily dissolved in aqueous electrolytes, leading to the loss of active materials and resulting in capacity decay. Furthermore, in NH4+, vanadium... + During repeated insertion / extraction processes, due to the combined effects of hydrogen bonding and volume effects, the material structure is prone to irreversible evolution or even collapse, which seriously affects cycle stability.

[0004] To address the aforementioned issues, existing technologies typically modify vanadium-based materials through carbon material composites, nanostructure manipulation, or defect introduction. For example, conductive carbon networks are constructed to enhance electron transport capabilities, or nanostructuring is used to shorten ion diffusion paths. However, existing technologies still have significant shortcomings: on the one hand, traditional composite methods often involve simple physical contacts with weak interfacial bonding, making it difficult to maintain structural stability during long-term cycling; on the other hand, although nanostructures can improve initial kinetic performance, they are still prone to aggregation or structural instability during repeated electrochemical processes, making it difficult to maintain a stable active phase. More importantly, existing research focuses primarily on the initial structural design of materials, neglecting the dynamic structural evolution behavior of materials during electrochemical processes. In aqueous ammonium-ion batteries, active materials often undergo a transformation from a crystalline state to an amorphous or low-order structure during charge and discharge, a process that directly affects the stability and reversibility of electrochemical performance. However, such structural evolution often lacks effective control methods, leading to uncontrollable active phases and thus limiting further improvements in material performance. Therefore, there is an urgent need to develop a vanadium-based composite electrode material that can achieve controllable structural evolution during electrochemical processes and has both good conductivity and interfacial stability, in order to meet the demand for high-performance electrode materials in aqueous ammonium-ion batteries. Summary of the Invention

[0005] The purpose of this invention is to address the problems of poor conductivity, insufficient structural stability, and uncontrollable structural evolution during electrochemical processes of existing vanadium-based electrode materials in aqueous ammonium-ion batteries. This invention provides a vanadium-based composite electrode material and its preparation method. Through structural regulation and interface design, the material achieves stable evolution during electrochemical processes, thereby improving its electrochemical performance and cycle stability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a vanadium-based nanoconfined structure supported nitrogen-doped carbon composite electrode material. In this material, by constructing a composite system of nitrogen-doped carbon matrix and vanadium-based nanostructure, the vanadium-based component is confined and dispersed at the nanoscale, and a stable interface structure is formed under the spatial constraint of the carbon matrix.

[0007] Preferably, the carbon matrix is ​​a two-dimensional or near-two-dimensional conductive structure that can provide a continuous electron transport path and restrict the nucleation and growth process of the vanadium-based components, thereby obtaining a size-controlled nanostructure.

[0008] During electrochemical charge-discharge processes, the vanadium-based nanostructure undergoes structural evolution, gradually transforming from an initial crystalline or low-aggregate state into an active phase dominated by amorphous vanadium oxides. This transformation process is regulated by the confinement of the carbon matrix and the interaction of interfaces, thereby preventing structural instability or uncontrollable evolution.

[0009] Furthermore, this structural evolution process is accompanied by ion insertion and deintercalation behavior, which constitutes the main energy storage mechanism.

[0010] In aqueous ammonium-ion batteries, due to NH4 + Due to hydrogen bonding and the synergistic effect with solvent molecules, materials are prone to structural perturbations and rearrangements during electrochemical processes. This invention effectively mitigates the adverse effects of such structural evolution by constructing a nanoconfined structure and a stable interface, enabling the material to maintain a stable active phase during repeated charge-discharge processes.

[0011] The present invention also provides a method for preparing the above-mentioned composite electrode material, comprising:

[0012] By combining a vanadium source with a nitrogen-containing carbon precursor and then heat-treating it under an inert atmosphere, vanadium species are formed into nano-confined structures within a carbon matrix. During the heat treatment process, the vanadium species undergo nucleation and growth, forming size-controlled nanostructures under the spatial constraint of the carbon matrix. Furthermore, the final structural morphology can be controlled by adjusting the solution conditions during the composite process to influence the dispersion state of the vanadium species.

[0013] The composite electrode material can be used in aqueous secondary batteries, and is especially suitable for aqueous ammonium ion battery systems.

[0014] Overall, the technical solutions conceived in this invention, compared with the prior art, can achieve at least the following beneficial effects.

[0015] (1) By constructing a nano-confined structure, the vanadium-based active components are uniformly dispersed, thereby shortening the electron and ion transport paths;

[0016] (2) Nitrogen-doped carbon matrix provides a continuous conductive network and enhances interface stability;

[0017] (3) The confined structure plays a regulatory role in the structural evolution of vanadium-based components, which helps to maintain a stable active phase;

[0018] (4) The material can undergo a controlled structural transformation during electrochemical processes, which is beneficial to improving the reversibility of the reaction;

[0019] (5) In an aqueous ammonium-ion battery system, the structure can mitigate the effects of NH4+. + The structural perturbation caused by embedding improves cycle stability.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Brief Description of the Drawings

[0021] Figure 1 This is a schematic diagram of the fabrication process of the vanadium-based nanoconfined structure loaded with nitrogen-doped carbon composite electrode material of the present invention; Figure 2 The image shows a transmission electron microscope (TEM) image of the composite electrode material obtained in Example 1. Figure 3 The X-ray diffraction (XRD) pattern of the material in Example 1; Figure 4 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the material in Example 1. Figure 5 The cyclic voltammetry (CV) curves of the material in Example 1 at different scan rates are shown. Figure 6 The rate performance curves of the material in Example 1 at different current densities are shown. Figure 7 The constant current charge-discharge curves of the material in Example 1 are shown. Figure 8 The long-cycle performance curve of the material in Example 1; Figure 9 The electrochemical impedance spectroscopy (Nyquist plot) of the material in Example 1 is shown. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but the implementation and protection scope of the present invention are not limited thereto.

[0023] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0024] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0025] Example 1

[0026] A method for preparing a vanadium-based nanoconfined structure supported nitrogen-doped carbon composite electrode material includes the following steps:

[0027] The following steps are required:

[0028] S1: Preparation of vanadium source solution

[0029] Ammonium metavanadate was dissolved in deionized water to prepare a solution with a concentration of 0.05 mol·L⁻¹. -1 A vanadium source solution was dissolved completely under magnetic stirring to form a homogeneous system. During this process, the pH of the solution was adjusted to approximately 6.5-7.5 to regulate the speciation and dispersion behavior of vanadium species in the solution.

[0030] S2: Construction of composite precursors

[0031] The nitrogen-doped carbon precursor was added to the vanadium source solution and ultrasonically dispersed for 30-60 min to allow vanadium species to be uniformly adsorbed on the surface and pores of the carbon matrix, forming a composite precursor system.

[0032] S3: Drying and Heat Treatment

[0033] The obtained composite precursor was dried at 60-80 °C and then placed in a tube furnace for heat treatment under a nitrogen atmosphere: heating rate: 5 °C·min -1 Heat treatment temperature: 800 ℃; Holding time: 2 h.

[0034] The material was then naturally cooled to room temperature to obtain a vanadium-based nanoconfined structure-supported nitrogen-doped carbon composite electrode material.

[0035] Examples 2-5

[0036] The materials were prepared according to the conditions in Table 1. The material structure was controlled by changing the type and concentration of vanadium source and the heat treatment conditions in different embodiments.

[0037] Example Vanadium source types <![CDATA[Vanadium source concentration (mol·L -1 ).]]> pH value Heat treatment Insulation time Material morphology 1 (Control) Ammonium metavanadate 0.05 6.5 800 2 h Quantum dot uniform loading 2 Sodium metavanadate 0.05 7.5 700 1 h Dispersed 3 Ammonium metavanadate 0.08 6.5 800 2h Dispersed relatively evenly 4 Potassium metavanadate 0.05 6.0 850 2 h Quantum dots uniformly distributed 5 Lithium metavanadate 0.05 5.8 900 3 h Localized mild aggregation

[0038] 1. Comparative Example 1 did not include nitrogen-doped carbon nanosheets, and the other preparation conditions were the same as in Example 1.

[0039] Electrode and battery assembly method: Using the materials obtained in Examples 1–5 and Comparative Example 1 as positive electrode active materials, the battery was assembled as follows: S1: Electrode preparation. The active material, conductive agent (Super P), and binder (PVDF) were mixed at a mass ratio of 8:1:1, NMP solvent was added and stirred into a slurry, which was then coated onto the current collector and vacuum dried at 80 °C for 12 h to obtain the working electrode. S2: Assembling an aqueous ammonium-ion battery. In an argon-protected glove box, a CR2032 coin cell was assembled using a zinc sheet as the negative electrode, glass fiber as the separator, and a 1 MNH4 salt aqueous solution as the electrolyte.

[0040] Electrochemical performance testing methods. Tests were conducted using the Xinwei Battery Testing System and the Chenhua Electrochemical Workstation, including constant current charge-discharge, cyclic voltammetry, and rate performance testing.

[0041] Analysis of Experimental Results

[0042] like Figure 1 As shown, the present invention provides a method for preparing a vanadium-based quantum dot-supported nitrogen-doped carbon composite electrode material.

[0043] like Figure 2 As shown, this is a TEM image of the composite material obtained in Example 1. It can be observed that vanadium-based species are uniformly distributed in the form of quantum dots on the surface of nitrogen-doped carbon nanosheets, with a particle size of about 1-10 nm, and no obvious agglomeration is observed.

[0044] like Figure 3 The image shows the XRD pattern of Example 1. The diffraction peaks in Example 1 are weak and significantly broadened, indicating that the vanadium-based species exist in a low-crystallization or quantum dot state.

[0045] like Figure 4The image shows the XPS test results. In Example 1, the V 2p peak indicates V... 4+ / V 5+ The coexistence state, along with the N 1s spectrum showing the presence of multiple nitrogen structures such as pyridine nitrogen and graphitic nitrogen, indicates that nitrogen doping of carbon successfully modulates the electronic structure.

[0046] like Figure 5 As shown, the CV curves of Example 1 maintain a good shape at different scan rates, exhibiting high reversibility and pseudocapacitive behavior.

[0047] like Figure 6 As shown, in Example 1, the concentration was 0.1-5 A·g -1 The quantum dot structure maintains a high capacity within the range, while the capacity of the comparative example 1 decreases significantly, indicating that the quantum dot structure significantly enhances the ion diffusion dynamics.

[0048] like Figure 7 As shown, the charge-discharge curve of Example 1 has a lower polarization voltage, indicating that its charge transfer impedance is lower.

[0049] like Figure 8 As shown, Example 1 exhibits excellent capacity retention during long-term cycling, while the comparison with the sample without nitrogen-doped carbon demonstrates that the nitrogen-doped carbon structure effectively inhibits the dissolution of active materials and structural collapse.

[0050] like Figure 9 As shown, the Nyquist curves indicate that Example 1 has a smaller charge transfer impedance, suggesting that its interfacial electrochemical reaction kinetics are superior.

[0051] In summary, this invention effectively enhances the electron transport capability and structural stability of materials by constructing a synergistic composite structure of vanadium-based quantum dots and nitrogen-doped carbon, thereby significantly improving their electrochemical performance in aqueous ammonium-ion batteries.

[0052] It should be noted that the above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vanadium-based nano-confined structure loaded nitrogen-doped carbon composite electrode material, characterized in that: It includes a nitrogen-doped carbon matrix and vanadium-based nanostructures dispersed and loaded thereon; the nitrogen-doped carbon matrix is ​​a two-dimensional or near-two-dimensional conductive carbon structure; the vanadium-based nanostructure has a characteristic size of 1-10 nm and is confined by the spatial confinement effect of the carbon matrix; the vanadium-based nanostructure can undergo structural evolution during electrochemical processes to form an active phase dominated by amorphous vanadium oxides, and the ion insertion / extraction behavior constitutes the main energy storage mechanism.

2. The material of claim 1, wherein: The vanadium-based nanostructures are selected from vanadium nitride, vanadium oxide, vanadium carbide, or combinations thereof.

3. The material of claim 1, wherein: The vanadium-based nanostructures are dispersed on the surface and / or in the pores of the carbon matrix, and are in a discrete or anchored state.

4. The material of claim 1, wherein: The nitrogen-doped carbon matrix contains graphitic nitrogen, pyridine nitrogen, and / or pyrrole nitrogen.

5. The material according to claim 1, characterized in that: The nitrogen-doped carbon matrix is ​​derived from the pyrolysis product of a nitrogen-containing organic precursor; the precursor is selected from g-C3N4, polymer precursors, or biomass carbon sources.

6. The material of claim 1, wherein: The material exhibits energy storage behavior based on multi-ion intercalation / deintercalation in aqueous electrolytes.

7. A method of making the material of claim 1, characterized by, include: (1) A composite precursor is formed by combining a vanadium source with a nitrogen-containing carbon precursor; (2) The composite precursor is heat-treated to form a nano-confined structure of vanadium species in a carbon matrix; the vanadium species undergo a nucleation-growth restricted process during the heat treatment process, thereby forming a size-controlled nanostructure.

8. The method of claim 7, wherein: The vanadium source is selected from vanadates, metavanadates, or soluble vanadium complexes.

9. The method of claim 7, wherein: During the heat treatment process, the nucleation and growth of vanadium species are restricted, thus controlling the nanostructure size to 1-10 nm.

10. A secondary battery characterized by comprising: Includes an electrode, said electrode comprising the material of any one of claims 1-6.

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