Vanadium-based positive electrode material, preparation method and application thereof

Abstract

The application discloses a vanadium-based positive electrode material and a preparation method and application thereof. The vanadium-based positive electrode material comprises a nitrogen-doped carbon matrix, quantum dot-sized vanadium nitride and vanadium trioxide loaded on the nitrogen-doped carbon matrix, a non-homogeneous interface is formed between the nitrogen-doped carbon matrix and the quantum dots, a heterojunction is formed between the quantum dot-sized vanadium nitride and the quantum dot-sized vanadium trioxide, and the nitrogen-doped carbon matrix is formed by calcining melamine. The preparation method comprises the following steps: adding ammonium metavanadate and melamine in a molar ratio of 1:2-4 into a dimethyl sulfoxide aqueous solution, stirring, obtaining a homogeneous solid solution, centrifuging, drying, sintering at 555 DEG C-1555 DEG C for 1h-5h in an inert atmosphere, and naturally cooling to obtain the vanadium-based positive electrode material. The vanadium-based positive electrode material has abundant heterojunctions, the preparation process is simple, the conditions are easy to control, the vanadium-based positive electrode material has long cycle stability, high specific capacity and excellent rate performance when used as a positive electrode of a zinc ion battery, and the zinc ion storage performance is outstanding.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, specifically relating to a vanadium-based cathode material, its preparation method, and its application. Background Technology

[0002] With the continuous growth in demand for consumer electronics, the steady development of electric vehicles, and increasingly stringent requirements for the safety and environmental friendliness of energy storage systems, aqueous energy storage devices are showing great potential in the next-generation battery market. Among the many aqueous batteries, rechargeable zinc-ion batteries have attracted widespread attention due to their high theoretical capacity (820 mAh / g), abundant zinc resources, high safety, and environmental friendliness. However, they still face challenges such as controversial and complex energy storage mechanisms and less-than-ideal performance, hindering their practical application. To address these issues, the development of advanced cathode materials (such as manganese-based oxides, Prussian blue analogs, organic compounds, and vanadium-based compounds) is crucial.

[0003] Vanadium-based compounds possess a typical layered structure and abundant valence states, along with higher energy density and theoretical capacity, effectively improving the performance of zinc-ion storage and making them a suitable choice for cathode materials in aqueous zinc-ion batteries. However, at high discharge depths, their rate performance and cycle stability are generally poor. This is because their inherent ionic / electronic conductivity and structural stability cannot keep pace with the rapid and large-volume generation of Zn. 2+ Insertion / extraction matching is crucial. To address these issues, it is essential to develop novel aqueous zinc-ion battery cathode materials with superior performance and stable structure.

[0004] Vanadium nitride possesses a high theoretical specific capacity and belongs to the interstitial compound or alloy group. The introduction of nitrogen into the transition metal lattice increases the d-electron density, resulting in an electronic structure similar to that of noble metals. However, vanadium nitride obtained through conventional preparation methods is typically composed of clustered particles, which severely hinders its electrochemical performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a vanadium-based cathode material with a large specific surface area, many active sites and abundant heterojunctions. It also provides a preparation method and application that is simple in process, easy to control under conditions, and conducive to large-scale production.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0007] A vanadium-based cathode material, wherein the vanadium-based cathode material is a vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material, comprising a nitrogen-doped carbon matrix and vanadium nitride and vanadium trioxide of quantum dot size loaded on the nitrogen-doped carbon matrix, wherein a heterogeneous interface is formed between the nitrogen-doped carbon matrix and the quantum dots, and a heterojunction is formed between the vanadium nitride quantum dots and the vanadium trioxide quantum dots, wherein the nitrogen-doped carbon matrix is ​​formed by calcining melamine.

[0008] In the aforementioned vanadium-based cathode material, preferably, the quantum dot particle size is ≤5nm.

[0009] As a general technical concept, the present invention also provides a method for preparing a vanadium-based cathode material, comprising the following steps:

[0010] (1) Add ammonium metavanadate and melamine to a mixed solution of dimethyl sulfoxide and water in a molar ratio of 1:2 to 4, stir, and obtain a homogeneous solid solution;

[0011] (2) Centrifuge and dry the homogeneous solid solution obtained in step (1) to obtain a mixed powder;

[0012] (3) The mixed powder obtained in step (2) is sintered in an inert gas atmosphere at a sintering temperature of 500℃~1000℃ and a sintering time of 1h~5h. After sintering, it is naturally cooled to room temperature to obtain vanadium-based cathode material, namely vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material.

[0013] In the preferred method for preparing the vanadium-based cathode material described above, in step (1), melamine is first dissolved in a mixed solution of dimethyl sulfoxide and water, and stirred and mixed for the first time to obtain a mixed solution; ammonium metavanadate is added to the mixed solution, and stirred and mixed for the second time to obtain a homogeneous solid solution of melamine and ammonium metavanadate.

[0014] In the above-mentioned method for preparing vanadium-based cathode materials, preferably, in step (1), the molar ratio of ammonium metavanadate and melamine is 1:3.

[0015] In the above-mentioned method for preparing vanadium-based cathode materials, preferably, in step (1), the volume ratio of dimethyl sulfoxide to water is 1:2 to 5.

[0016] In the above-mentioned method for preparing vanadium-based cathode materials, preferably, in step (2), the centrifugation rate is 8000 r / min to 9500 r / min.

[0017] In the above-mentioned method for preparing vanadium-based cathode materials, preferably, in step (2), the drying is vacuum drying, the temperature of the vacuum drying is 60℃~100℃, and the time of the vacuum drying is 12h~24h.

[0018] In the above-mentioned method for preparing vanadium-based cathode materials, preferably, in step (3), the inert gas is nitrogen or argon.

[0019] As a general technical concept, the present invention also provides an application of the above-mentioned vanadium-based cathode material and the vanadium-based cathode material prepared by the above-mentioned preparation method in zinc-ion batteries (i.e., zinc storage application).

[0020] In the above applications, preferably, the zinc-ion battery is an aqueous zinc-ion battery.

[0021] The main innovation of this invention is as follows:

[0022] Construction of dual heterostructure: a heterostructure between vanadium nitride quantum dots and vanadium trioxide quantum dots, and a heterojunction between a nitrogen-doped carbon matrix and the two types of quantum dots. This invention uses melamine as the nitrogen source and ammonium metavanadate as the vanadium source. It mainly achieves partial nitridation and partial oxidation by adjusting the melamine content based on a fixed amount of ammonium metavanadate, thereby constructing a heterostructure of vanadium nitride and vanadium oxide. The vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material of this invention has enhanced structural stability due to the synergistic effect of the two phases and the rich heterostructure between them. Its outstanding advantages can be mainly reflected in two aspects: (1) when it undergoes deep charge and discharge at different rates and then gradually returns to a current density of 0.1 A / g for deep charge and discharge, it can obtain a retention rate of up to 97.6%; (2) after 2000 charge and discharge cycles at a high current density of 10 A / g, it can still obtain an initial capacity retention rate of 87%. This heterostructure material fully leverages the high conductivity of vanadium nitride and the high capacity of vanadium trioxide. Combined with the structural stability of the heterostructure, the electrochemical performance of this electrode material is comprehensively improved.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) The vanadium-based cathode material of the present invention is formed by partially nitriding the vanadium source with ammonia gas generated from the calcination of melamine, and simultaneously loading quantum dot-sized vanadium nitride and vanadium trioxide onto the nitrogen-doped carbon matrix generated by the calcination. This cathode material combines the advantages and synergistic effects of the heterogeneous structure between the vanadium nitride quantum dots and vanadium trioxide quantum dots, and also incorporates the advantages of quantum dot size design, resulting in a large specific surface area, more active sites, shorter ion diffusion paths, and effective buffering of volume changes during charge and discharge. This enables the material to provide higher capacitance and stable cycle performance for aqueous zinc-ion batteries. In addition, the heterogeneous interface formed between the quantum dots and the carbon substrate facilitates charge transfer and improves the conductivity of the material.

[0025] (2) The preparation method of this invention employs a one-step solution-phase assisted thermal nitration method, in which melamine is carbonized at high temperature to form a nitrogen-doped carbon matrix, which serves as the nucleation substrate. Vanadium nitride / vanadium trioxide heterojunction quantum dots are then uniformly dispersed in the nitrogen-doped carbon matrix. By designing and optimizing the molar ratio of ammonium metavanadate to melamine in the precursor to 1:2-4, vanadium nitride / vanadium trioxide heterojunction quantum dots with different ratios on the nitrogen-doped carbon matrix are obtained. Due to the size advantage of quantum dots, the vanadium-based cathode material obtains a larger specific surface area, more active sites, and a shorter ion diffusion path, and can effectively buffer the volume change of the material during charge and discharge. The heterogeneous interface formed between the quantum dots and the carbon substrate is conducive to charge transfer and improves the conductivity of the material. The heterostructure formed by the contact between vanadium nitride and vanadium trioxide quantum dots can give full play to the advantages of both phases and synergistically improve its electrochemical performance in all aspects.

[0026] (3) Compared with the prior art, the preparation method of the present invention is simple, low-cost, and easy to control, which is conducive to large-scale production. The synthesized vanadium-based cathode material has excellent electrical properties, which is conducive to industrial application and helps to promote the practical application of zero-dimensional quantum dot materials.

[0027] (4) This invention is the first to propose the application of vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material in zinc-ion battery cathode, which not only has long cycle stability, but also high specific capacity, excellent rate performance, and outstanding zinc-ion storage performance. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the vanadium-based cathode material in Example 1 of the present invention.

[0029] Figure 2 The images are transmission electron microscope (TEM) images of the vanadium-based cathode material in Example 1 of this invention at different magnifications.

[0030] Figure 3 The X-ray diffraction patterns are those of the cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0031] Figure 4 The diagram shows the rate performance of the cathode materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention in an aqueous zinc-ion battery.

[0032] Figure 5 This is a graph showing the cycling performance of the vanadium-based cathode material in an aqueous zinc-ion battery at a current density of 10 A / g, as described in Example 1 of this invention. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. In the following embodiments, unless otherwise specified, the raw materials and instruments used are commercially available, and the data obtained are the average values ​​of three or more repeated experiments. In the following embodiments, the room temperature conditions are all between 20°C and 30°C.

[0034] Example 1

[0035] A vanadium-based cathode material of the present invention is a vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material, specifically comprising a nitrogen-doped carbon matrix and vanadium nitride and vanadium trioxide quantum dots of the same size loaded on the nitrogen-doped carbon matrix. A heterogeneous interface is formed between the nitrogen-doped carbon matrix and the quantum dots, and a heterojunction is formed between the vanadium nitride quantum dots and the vanadium trioxide quantum dots. The nitrogen-doped carbon matrix is ​​formed by calcining melamine, the quantum dot particle size is less than or equal to 5 nm, and there are abundant heterojunction interfaces, such as... Figure 1 and 2 As shown. Figure 1 This is a scanning electron microscope image of the vanadium-based cathode material from Example 1. Figure 2 The images show transmission electron microscopy (TEM) images of the vanadium-based cathode material in Example 1 at different magnifications. As can be seen from the images, the lattice spacings of 0.241 nm and 0.204 nm correspond to the (110) crystal plane of V2O3 and the (200) crystal plane of VN, respectively. This confirms that V2O3 and VN are closely adjacent and have abundant heterostructures, providing a large number of crystal defects and active sites for the material, which further promotes ion / electron transfer and improves electronic conductivity.

[0036] A method for preparing a vanadium-based cathode material according to the present invention includes the following steps:

[0037] (1) Mix 12 mL of water and 6 mL of dimethyl sulfoxide uniformly to obtain a dimethyl sulfoxide aqueous solution. Weigh 0.5675 g (approximately 0.0045 mol) of melamine and add it to the above solution. Stir vigorously for 1 h to obtain a homogeneous mixed solution. Then slowly add 0.1755 g (approximately 0.0015 mol) of ammonium metavanadate to the above mixed solution and stir for 1 h to obtain a homogeneous solid solution of melamine and ammonium metavanadate.

[0038] (2) The homogeneous solid solution obtained in step (1) is centrifuged at 9000 r / min. The separated precipitate is dried in a vacuum drying oven at 60℃ for 24 h, and then naturally cooled to room temperature to obtain a dry mixed powder.

[0039] (3) Place the mixed powder obtained in step (2) into a crucible, put it into a tube furnace, and sinter it at 800°C at 5°C / min under a nitrogen atmosphere. Then, cool it naturally to room temperature to obtain the vanadium-based cathode material.

[0040] To verify the electrochemical performance of the vanadium-based cathode material prepared in this embodiment, it was further applied as a cathode material in an aqueous zinc-ion battery: the prepared vanadium-based cathode material, binder, and conductive agent were dissolved in N-methylpyrrolidone at a mass ratio of 7:2:1 to prepare a slurry, which was coated on carbon paper, vacuum dried, and used as the cathode. Zinc foil was used as the anode, glass fiber filter paper was used as the separator, and 2M zinc trifluoromethanesulfonate was used as the electrolyte. An aqueous zinc-ion battery was assembled and its electrochemical performance was tested.

[0041] Electrochemical testing results show that the aqueous zinc-ion battery assembled with the vanadium-based cathode material prepared in this embodiment achieves a maximum discharge specific capacity of 626 mA h / g after activation at a current density of 0.1 A / g, and retains 87% of its capacity after 2000 cycles at a high current density of 10 A / g. Figure 4 As shown in the rate performance graph, after cycling at different current densities, the battery still has a discharge specific capacity of 596 mA h / g at a current density of 0.1 A / g.

[0042] Comparative Example 1

[0043] A vanadium trioxide quantum dot cathode material was prepared using a method that was essentially the same as in Example 1, except that the mass of melamine added in step (1) was 0.1892 g (approximately 0.0015 mol). Electrochemical performance tests were performed according to the steps of Example 1. The results showed that the vanadium trioxide quantum dot cathode material prepared in this comparative example achieved a maximum discharge specific capacity of 453 mA h / g after activation at a current density of 0.1 A / g. Figure 4 As shown in the rate performance graph, after cycling at different current densities, the specific discharge capacity of this battery at a current density of 0.1 A / g is 319 mA h / g.

[0044] Comparative Example 2

[0045] A vanadium nitride quantum dot cathode material was prepared using a method that was essentially the same as in Example 1, except that the mass of melamine added in step (1) was 0.9458 g (approximately 0.0075 mol). Electrochemical performance tests were performed according to the steps of Example 1. The results showed that the vanadium nitride quantum dot cathode material, after activation at a current density of 0.1 A / g, achieved a maximum discharge specific capacity of 502 mA h / g. Figure 4 As shown in the rate performance graph, after cycling at different current densities, the discharge specific capacity of this battery at a current density of 0.1 A / g is 423 mA h / g.

[0046] Table 1 Comparison of electrochemical performance between Comparative Examples 1 and 2 and Example 1

[0047]

[0048] In practical research, the applicant discovered that when the molar ratio of ammonium metavanadate to melamine is greater than 1:2, the prepared material is vanadium trioxide cathode material that has not been nitrided; when the molar ratio of ammonium metavanadate to melamine is 1:2 to 4 (including the endpoint value), the prepared material is vanadium nitride / vanadium trioxide heterojunction cathode material (the content of V2O3 in the product was calculated to be about 15% through further XRD refinement); when the molar ratio of ammonium metavanadate to melamine is further reduced to less than 1:4, the prepared material is vanadium nitride quantum dot cathode material.

[0049] Figure 3 The X-ray diffraction patterns of the cathode materials prepared in Examples 1, 1, and 2 of this invention are shown in the figures. It can be seen from the figures that the vanadium nitride / vanadium trioxide heterojunction quantum dot cathode materials, vanadium trioxide quantum dot cathode materials, and vanadium nitride quantum dot cathode materials prepared in Examples 1, 1, and 2 correspond well with the standard cards of VN and V2O3 (PDF#35-0768-VN, PDF#34-0187-V2O3).

[0050] Combining the data in Table 1 and Figure 4 As can be seen, the vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material with a two-phase composite heterostructure in Example 1 has significantly improved discharge specific capacity and rate performance compared with Comparative Example 1 and Comparative Example 2. This is due to the advantage of quantum dot size and the synergistic effect of vanadium nitride and vanadium trioxide, which fully utilizes the high conductivity of vanadium nitride and the high capacity of vanadium trioxide, resulting in a comprehensive improvement in the electrochemical performance of the electrode material.

[0051] Figure 5 This is a graph showing the cycling performance of the vanadium-based cathode material of Example 1 of the present invention in an aqueous zinc-ion battery at a current density of 10 A / g. The vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material of Example 1, after 2000 cycles in an aqueous zinc-ion battery at a current density of 10 A / g, still maintains a discharge specific capacity of 283.9 mA h / g, with a capacity retention of 87% and a coulombic efficiency close to 100%, demonstrating excellent cycle stability.

[0052] Therefore, this invention introduces a new synthesis method, controls the nanostructure, constructs a heterostructure and combines it with nitrogen-doped conductive carbon materials, which plays an important role in improving the performance of vanadium nitride cathode materials.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A vanadium-based cathode material, characterized in that, The vanadium-based cathode material is a vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material, comprising a nitrogen-doped carbon matrix and vanadium nitride and vanadium trioxide of quantum dot size loaded on the nitrogen-doped carbon matrix. A heterogeneous interface is formed between the nitrogen-doped carbon matrix and the quantum dots, and a heterojunction is formed between the vanadium nitride quantum dots and the vanadium trioxide quantum dots. The nitrogen-doped carbon matrix is ​​formed by calcining melamine.

2. The vanadium-based cathode material according to claim 1, characterized in that, The particle size of the quantum dots is ≤5 nm.

3. A method for preparing a vanadium-based cathode material, characterized in that, Includes the following steps: (1) Add ammonium metavanadate and melamine to a mixed solution of dimethyl sulfoxide and water in a molar ratio of 1:2 to 4, stir, and obtain a homogeneous solid solution; (2) Centrifuge and dry the homogeneous solid solution obtained in step (1) to obtain a mixed powder; (3) The mixed powder obtained in step (2) is sintered in an inert gas atmosphere at a sintering temperature of 500℃~1000℃ and a sintering time of 1h~5h. After sintering, it is naturally cooled to room temperature to obtain vanadium-based cathode material, namely vanadium nitride / vanadium trioxide heterojunction quantum dot cathode material.

4. The method for preparing the vanadium-based cathode material according to claim 3, characterized in that, In step (1), the melamine is first dissolved in a mixed solution of dimethyl sulfoxide and water, and stirred for the first time to obtain a mixed solution; ammonium metavanadate is added to the mixed solution, and stirred for the second time to obtain a homogeneous solid solution of melamine and ammonium metavanadate.

5. The method for preparing the vanadium-based cathode material according to claim 3, characterized in that, In step (1), the molar ratio of ammonium metavanadate and melamine is 1:

3.

6. The method for preparing vanadium-based cathode material according to claim 3, characterized in that, In step (1), the volume ratio of dimethyl sulfoxide to water is 1:2 to 5.

7. The method for preparing the vanadium-based cathode material according to claim 3, characterized in that, In step (2), the centrifugation rate is 8000 r / min to 9500 r / min.

8. The method for preparing vanadium-based cathode material according to claim 3, characterized in that, In step (2), the drying is vacuum drying, the temperature of the vacuum drying is 60℃~100℃, and the time of the vacuum drying is 12h~24h.

9. The method for preparing the vanadium-based cathode material according to claim 3, characterized in that, In step (3), the inert gas is nitrogen or argon.

10. The application of a vanadium-based cathode material as described in claim 1 or 2, or a vanadium-based cathode material prepared by the preparation method described in any one of claims 3 to 9, in an aqueous zinc-ion battery.

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