Vanadium-based electrode material, preparation method thereof, and lithium-ion battery positive electrode sheet

Abstract

The present invention belongs to the field of electrode material technology, and specifically relates to vanadium-based electrode materials and preparation methods thereof and lithium-ion battery positive electrode sheets. The present invention provides a new type of vanadium-based electrode material Li x Na y VO 3‑z M w , wherein M is selected from F, Cl, or Br. The present invention first mixes a vanadium source with a soluble sodium salt aqueous solution, uses a solution-freeze drying method to produce β-NaVO3 powder, then mixes the β-NaVO3 powder with a lithium halide, and uses a solvothermal method to achieve ion exchange to obtain a vanadium-based electrode material. The vanadium-based electrode material of the present invention is made from inexpensive and readily available raw materials, while having good electrochemical properties, structural stability, and thermal stability, while overcoming the low ionic and electronic conductivity problems of existing vanadium-based electrode materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and in particular relates to a vanadium-based electrode material and a preparation method thereof, and a positive electrode sheet for a lithium-ion battery. Background Art

[0002] To address energy shortages and environmental degradation, the development and utilization of environmentally friendly renewable energy has become a hot topic for researchers. Lithium-ion batteries, with their high specific energy, high operating voltage, and excellent cycle performance, are widely used in portable mobile devices and electric vehicles.

[0003] Cathode materials significantly impact the performance of lithium-ion batteries. However, the key elements required for preparing cathode materials, such as nickel, cobalt, and manganese, are limited in resources. Continued consumption inevitably leads to rising costs and resource shortages. Therefore, developing cathode materials with superior performance, low cost, and environmental friendliness is crucial.

[0004] The abundance of vanadium in the Earth's crust is far higher than that of nickel, cobalt, and manganese, making the use of vanadium-based compounds a cost-effective option. Furthermore, vanadium's multivalent states enable multi-electron redox reactions, giving vanadium-based electrode materials a high theoretical specific capacity. This makes vanadium-based compounds a promising research prospect and valuable asset in the field of lithium-ion battery energy storage materials. However, existing vanadium-based electrode materials suffer from low ionic and electronic conductivity, hindering their application. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a vanadium-based electrode material and a preparation method thereof and a positive electrode sheet for a lithium-ion battery. x Na y VO 3-z M w , wherein M is selected from F, Cl or Br. The present invention first mixes a vanadium source with a soluble sodium salt aqueous solution, uses a solution-freeze drying method to prepare β-NaVO3 powder, then mixes the β-NaVO3 powder with a lithium halide, and uses a solvent thermal method to achieve ion exchange to obtain a vanadium-based electrode material. The vanadium-based electrode material of the present invention is made from inexpensive and readily available raw materials, and while having good electrochemical properties, structural stability and thermal stability, it overcomes the problems of low ionic conductivity and electronic conductivity of prior vanadium-based electrode materials.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention protects a vanadium-based electrode material, the chemical formula of which is: Li x Na y VO 3-z Mw , wherein M is selected from F, Cl or Br.

[0008] When M is selected from F, 0<x<0.1, 0<y<1, 0<z<0.1, 0<w≤0.1.

[0009] When M is selected from Cl or Br, 0<x<1, 0<y<1, 0<z<0.2, 0.1≤w≤1.

[0010] Preferably, the crystal structure of the vanadium-based electrode material belongs to the orthorhombic system.

[0011] Preferably, when M is selected from F, 0.01≤x≤0.098, 0.093≤y≤0.98, 0.02≤z≤0.09, and 0.01≤w≤0.1.

[0012] Preferably, when M is selected from Cl, 0.1≤x≤0.98, 0.08≤x≤0.95, 0.05≤z≤0.19, and 0.1≤w≤1.

[0013] Preferably, when M is selected from Br, 0.1≤x≤0.88, 0.48≤x≤0.95, 0.07≤z≤0.1, and 0.1≤w≤1.

[0014] The present invention also provides a method for preparing a vanadium-based electrode material, comprising the following steps:

[0015] The vanadium source is added to a soluble sodium salt aqueous solution and mixed evenly, and then heated to obtain a sample. The heating process promotes uniform mixing of the raw materials on the one hand, and evaporates water on the other hand. The heating conditions are: heating and stirring at 50°C~70°C for 1h~10h to obtain a sample.

[0016] The sample is freeze-dried, that is, the solution-freeze-drying method is used to obtain β-NaVO3 powder. This method was obtained through laboratory exploration. β-phase sodium metavanadate cannot be prepared by high-temperature solid-phase method, and the solution method directly uses low-temperature drying, which often contains impurities. The freeze-drying method can obtain β-NaVO3 with higher purity. Moreover, the β-NaVO3 prepared by the solution-freeze-drying method has oxygen vacancies, which is conducive to ion diffusion.

[0017] β-NaVO3 powder is added to the alcohol solution of lithium halide and subjected to solvent thermal treatment by solvent thermal method. At this time, ion exchange occurs, and Na + With Li + Exchange, M - and VO3 - Ion exchange to obtain vanadium-based electrode materials.

[0018] Wherein, the lithium halide is selected from lithium fluoride, lithium chloride or lithium bromide.

[0019] Preferably, the molar ratio of the vanadium source to the soluble sodium salt is 0.9 to 1.2:1. Experimental results show that if the molar ratio of the vanadium source to the soluble sodium salt is less than 0.9:1, impurities appear in the β-NaVO3 powder.

[0020] Preferably, the concentration of the soluble sodium salt aqueous solution is greater than 0.1 mol / L. If it is lower than 0.1 mol / L, the pH value cannot be guaranteed to be greater than 10, which is not conducive to the formation of VO3 - The maximum concentration of the soluble sodium salt aqueous solution is its saturation concentration.

[0021] Preferably, the soluble sodium salt is selected from one or more of Na2CO3, NaHCO3, and NaOH.

[0022] Preferably, the vanadium source is selected from one or more of V2O5, NH4VO3, and V2O3.

[0023] Preferably, the solvent thermal treatment conditions are: heating at 50° C. to 120° C. for 3 h to 48 h.

[0024] Preferably, the molar ratio of lithium halide to β-NaVO3 powder is 5-10:1.

[0025] Preferably, the solvent of the alcohol solution of lithium halide is one of ethanol, propanol, and pentanol, or a mixture of two of them.

[0026] The present invention also protects a lithium-ion battery positive electrode sheet, which is made of a vanadium-based electrode material, a conductive agent, a binder and a current collector. The vanadium-based electrode material, the conductive agent and the binder are mixed in a solvent to obtain a slurry, the slurry is evenly coated on the current collector, and the solvent is evaporated after drying to obtain the lithium-ion battery positive electrode sheet.

[0027] Preferably, the conductive agent is selected from one or more of Super P conductive carbon black, conductive acetylene black, ordered mesoporous carbon CMK-3, carbon nanotubes, and graphene; the binder is selected from polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, polytetrafluoroethylene, or polyvinyl alcohol; the solvent is selected from N-methylpyrrolidone; and the current collector is selected from aluminum foil or copper foil.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention provides a new type of vanadium-based electrode material Li x Na y VO 3-z M w , wherein M is selected from F, Cl or Br; vanadium-based electrode material Li x Na y VO 3-z M wThe crystal structure belongs to the orthorhombic system, which is the crystal system of β-NaVO3. The product Li obtained after ion exchange x Na y VO 3-z M w The original crystal system of β-NaVO3 is maintained; in the orthorhombic NaVO3, VO5 polyhedrons are connected into VO3 chains, extending along the b-axis direction. The crystal structure is open and has multi-dimensional ion diffusion channels, so the Li after ion exchange x Na y VO 3-z M w Maintaining the original structure is conducive to ion diffusion. The introduction of halogen atoms does not change the open crystal structure of the parent phase, but due to the difference in atomic radius, it causes lattice distortion and defects, which change the Li x Na y VO 3-z M w The band structure of Li x Na y VO 3-z M w In addition, a certain degree of lattice distortion effectively expands the lithium ion diffusion path, thereby improving the ionic conductivity.

[0030] 2. The vanadium-based electrode material of the present invention is Li x Na y VO 3-z M w , and has good electrochemical compatibility with halide solid electrolytes with similar composition and structure.

[0031] 3. Li prepared by the method of the present invention x Na y VO 3-z M w It has oxygen vacancy defects, which are beneficial to the diffusion of lithium ions.

[0032] 4. The vanadium-based electrode material Li of the present invention x Na y VO 3-z M w It has good electrochemical properties, structural stability and thermal stability, and is a positive electrode material with research value and application potential.

[0033] 5. The present invention provides a method for preparing a vanadium-based electrode material. The raw materials used in the preparation process are simple and inexpensive, the reaction conditions are simple and mild, and no complicated preparation process is involved. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1This is a cycle performance diagram of the vanadium-based electrode materials of Examples 1 to 4 of the present invention and Comparative Example 1.

[0035] Figure 2 This is a rate performance diagram of the vanadium-based electrode materials of Examples 1 to 4 of the present invention and Comparative Example 1.

[0036] Figure 3 This is a graph showing the first charge and discharge curves of the vanadium-based electrode materials of Examples 1 to 4 of the present invention and Comparative Example 1.

[0037] Figure 4 The EIS graphs of the vanadium-based electrode materials of Example 4 of the present invention and Comparative Example 1 are shown; Figure 4 Figure (a) is the EIS diagram of the vanadium-based electrode material of Comparative Example 1. Figure 4 Figure (b) is the EIS diagram of the vanadium-based electrode material of Example 4. Figure 4 Figure (c) shows the real impedance and ω of the vanadium-based electrode material of Example 4 and Comparative Example 1. −1 / 2 Linear relationship graph, Figure 4 Figure (d) is a comparison of the lithium ion diffusion coefficients of the vanadium-based electrode materials of Example 4 and Comparative Example 1.

[0038] Figure 5 The thermogravimetric curves of the vanadium-based electrode materials of Example 4 and Comparative Example 1 of the present invention are shown.

[0039] Figure 6 The SEM image and elemental analysis diagram of the vanadium-based electrode material of Example 4 of the present invention; Figure 6 Figure a is a SEM image. Figure 6 Figure b is the element analysis diagram.

[0040] Figure 7 This is the electron spin resonance image of the vanadium-based electrode material of Example 4 of the present invention. DETAILED DESCRIPTION

[0041] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0042] Considering the problem that the ionic conductivity and electronic conductivity of the existing vanadium-based electrode materials are both low, the present invention provides a new vanadium-based electrode material Li x Na y VO 3-z M w, wherein M is selected from F, Cl or Br. When M is selected from F, 0<x<0.1, 0<y<1, 0<z<0.1, 0<w≤0.1; when M is selected from Cl or Br, 0<x<1, 0<y<1, 0<z<0.2, 0.1≤w≤1. The present invention first prepares orthorhombic β-NaVO3, and then uses β-NaVO3 and lithium halide F to react. - 、Cl - or Br - Ion exchange was performed to obtain vanadium-based electrode material Li x Na y VO 3-z M w . Vanadium-based electrode material Li x Na y VO 3-z M w It not only maintains the original orthorhombic crystal system of β-NaVO3, but also has a structure and composition similar to that of halide solid electrolytes with high ionic conductivity and electrochemical compatibility. In addition, the introduction of halogen atoms leads to lattice distortion, which improves the Li x Na y VO 3-z M w The experimental results show that NaVO3 or LiVO3 of other crystal systems will not undergo ion exchange under the conditions of the technical solution of the present invention, thereby producing Li x Na y VO 3-z M w product.

[0043] The technical solution of the present invention is studied using examples and comparative examples. In the examples, different ion exchange times result in different final chemical compositions. The specific research methods and results are shown below:

[0044] Example 1

[0045] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.1 Na 0.95 VO 2.95 Cl 0.1 , including the following steps:

[0046] S1. Weigh 0.01 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.1 mol / L Na2CO3 solution.

[0047] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 4 hours.

[0048] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0049] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0050] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 10:1, and stir magnetically for 30 minutes to obtain a mixed solution.

[0051] S6. Transfer the mixed solution to a reactor and place it in an 80°C oven for ion exchange reaction for 3 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium chloride, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0052] Example 2

[0053] The preparation method of the vanadium-based electrode material is the same as the preparation steps of Example 1, except that the ion exchange reaction time is replaced by 6 hours from 3 hours. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.2 Na 0.8 VO 2.9 Cl 0.2 , including the following steps:

[0054] S1. Weigh 0.01 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.1 mol / L Na2CO3 solution.

[0055] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 4 hours.

[0056] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0057] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0058] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 10:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0059] S6. Transfer the mixed solution to a reactor and place it in an oven at 80°C for ion exchange reaction for 6 hours to obtain an ion exchange product. After the reaction, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium chloride, and then place it in an oven at 50°C for drying to obtain a vanadium-based electrode material.

[0060] Example 3

[0061] The preparation method of the vanadium-based electrode material is the same as the preparation steps of Example 1, except that the ion exchange reaction time is replaced by 12 hours from 3 hours. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.5 Na 0.5 VO 2.9 Cl 0.5 , including the following steps:

[0062] S1. Weigh 0.01 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.1 mol / L Na2CO3 solution.

[0063] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 4 hours.

[0064] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0065] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0066] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 10:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0067] S6. Transfer the mixed solution to a reactor and place it in an 80°C oven for ion exchange reaction for 12 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium chloride, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0068] Example 4

[0069] The preparation method of the vanadium-based electrode material is the same as the preparation steps of Example 1, except that the ion exchange reaction time is replaced by 24 hours from 3 hours. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.77 Na 0.68 VO 2.84 Cl 0.67 , including the following steps:

[0070] S1. Weigh 0.01 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.1 mol / L Na2CO3 solution.

[0071] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 4 hours.

[0072] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0073] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0074] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 10:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0075] S6. Transfer the mixed solution to a reactor and place it in an oven at 80°C for 24 hours to carry out an ion exchange reaction to obtain an ion exchange product. After the reaction, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it four times to remove excess lithium chloride, and then place it in an oven at 50°C for drying to obtain a vanadium-based electrode material.

[0076] Example 5

[0077] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.98 Na0.08 VO 2.81 C1, comprising the steps of:

[0078] S1. Weigh 0.012 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.12 mol / L Na2CO3 solution.

[0079] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 50°C water bath and heat it to allow Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 4 hours.

[0080] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0081] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0082] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 5:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0083] S6. Transfer the mixed solution to a reactor and place it in a 50°C oven for ion exchange reaction for 48 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium chloride, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0084] Example 6

[0085] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.098 Na 0.093 VO 2.91 F 0.1 , including the following steps:

[0086] S1. Weigh 0.012 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.12 mol / L Na2CO3 solution.

[0087] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 6 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 10 hours.

[0088] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0089] S4. Add lithium fluoride to ethanol and stir thoroughly to dissolve, to obtain a saturated lithium fluoride ethanol solution.

[0090] S5. Add β-NaVO3 powder to the saturated ethanol solution of lithium fluoride, control the molar ratio of LiF:β-NaVO3 to be 7:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0091] S6. Transfer the mixed solution to a reactor and place it in a 70°C oven for ion exchange reaction for 48 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge 4 times to remove excess lithium fluoride, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0092] Example 7

[0093] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.88 Na 0.48 VO 2.93 Br 0.9 , including the following steps:

[0094] S1. Weigh 0.012 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.12 mol / L Na2CO3 solution.

[0095] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 50°C water bath and heat it to allow the Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water to obtain a sample.

[0096] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0097] S4. Add lithium bromide to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium bromide with a concentration of 5 mol / L.

[0098] S5. Add β-NaVO3 powder to the ethanol solution of lithium bromide, control the molar ratio of LiBr:β-NaVO3 to be 6:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0099] S6. Transfer the mixed solution to a reactor and place it in a 50°C oven for ion exchange reaction for 26 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium bromide, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0100] Example 8

[0101] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.1 Na 0.95 VO 2.9 Br 0.1 , including the following steps:

[0102] S1. Weigh 0.009 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.09 mol / L Na2CO3 solution.

[0103] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 60°C water bath and heat it to allow the Na2CO3 and V2O5 to react for 10 hours. During the reaction, gradually evaporate the water to obtain a sample.

[0104] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0105] S4. Add lithium bromide to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium bromide with a concentration of 5 mol / L.

[0106] S5. Add β-NaVO3 powder to the ethanol solution of lithium bromide, control the molar ratio of LiBr:β-NaVO3 to be 6:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0107] S6. Transfer the mixed solution to a reactor and place it in an oven at 100°C for ion exchange reaction for 3 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it 4 times to remove excess lithium bromide, and then place it in an oven at 50°C for drying to obtain a vanadium-based electrode material.

[0108] Example 9

[0109] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.98 Na 0.17 VO 2.81 Br, comprising the following steps:

[0110] S1. Weigh 0.012 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.12 mol / L Na2CO3 solution.

[0111] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 50°C water bath and heat it to allow the Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water to obtain a sample.

[0112] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0113] S4. Add lithium bromide to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium bromide with a concentration of 5 mol / L.

[0114] S5. Add β-NaVO3 powder to the ethanol solution of lithium bromide, control the molar ratio of LiBr:β-NaVO3 to be 6:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0115] S6. Transfer the mixed solution to a reactor and place it in a 120°C oven for ion exchange reaction for 48 hours to obtain an ion exchange product. After the reaction, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge it four times to remove excess lithium bromide, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0116] Example 10

[0117] Preparation method of vanadium-based electrode material. The chemical formula of the vanadium-based electrode material in this embodiment is: Li 0.01 Na 0.98 VO 2.98 F 0.01 , including the following steps:

[0118] S1. Weigh 0.012 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.12 mol / L Na2CO3 solution.

[0119] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow Na2CO3 and V2O5 to react for 6 hours. During the reaction, gradually evaporate the water and continue heating and stirring for 10 hours.

[0120] S3. Pour the viscous sample into a culture dish, place it in a freeze dryer cold trap for pre-freezing for 3 hours, and freeze-dry it for 12 hours after it is completely frozen to obtain β-NaVO3 powder.

[0121] S4. Add lithium fluoride to ethanol and stir thoroughly to dissolve, to obtain a saturated lithium fluoride ethanol solution.

[0122] S5. Add β-NaVO3 powder to the saturated ethanol solution of lithium fluoride, control the molar ratio of LiF:β-NaVO3 to be 7:1, and magnetically stir for 30 minutes to obtain a mixed solution.

[0123] S6. Transfer the mixed solution to a reactor and place it in a 50°C oven for ion exchange reaction for 12 hours to obtain an ion exchange product. After the reaction is completed, wait for the reactor to cool, wash the ion exchange product with ethanol, centrifuge 4 times to remove excess lithium fluoride, and then place it in a 50°C oven for drying to obtain a vanadium-based electrode material.

[0124] Comparative Example 1

[0125] The preparation method of the vanadium-based electrode material is the same as the preparation steps of Example 1, except that the ion exchange reaction time is replaced by 0 h from 3 h, and includes the following steps:

[0126] S1. Weigh 0.01 mol of Na2CO3 and add it to a beaker containing 100 mL of deionized water. Stir thoroughly at 300 rpm for 15 min to obtain a 0.1 mol / L Na2CO3 solution.

[0127] S2. Weigh 0.01 mol of V2O5 and add it to the Na2CO3 solution. After magnetic stirring for 30 minutes, place the beaker in a 70°C water bath and heat it to allow the Na2CO3 and V2O5 to react for 3 hours. During the reaction, gradually evaporate the water to obtain a sample.

[0128] S3. Pour the sample into a culture dish and place it in a freeze dryer cold trap for pre-freezing for 3 hours. After it is completely frozen, freeze-dry it for 12 hours to obtain β-NaVO3 powder.

[0129] S4. Add lithium chloride to ethanol and stir thoroughly to dissolve, to obtain an ethanol solution of lithium chloride with a concentration of 5 mol / L.

[0130] S5. Add β-NaVO3 powder to the ethanol solution of lithium chloride, control the molar ratio of LiCl:β-NaVO3 to 10:1, and stir magnetically for 30 minutes to obtain a mixed solution.

[0131] S6. The mixed solution was washed with ethanol, centrifuged four times to remove excess lithium chloride, and then dried in an oven at 50° C. to obtain a vanadium-based electrode material.

[0132] Examples 1 to 6 of the present invention all produce vanadium-based electrode materials with good electrochemical properties, structural stability, and thermal stability. The vanadium-based electrode materials of Examples 1 to 4 are taken as examples and compared with Comparative Example 1. The specific research methods and results are shown below:

[0133] Assembly of lithium-ion battery: The vanadium-based electrode materials obtained in Comparative Example 1 and Examples 1 to 4 were respectively ground and mixed with the conductive agent carbon nanotubes and the binder polyvinylidene fluoride in a mass ratio of 7:2:1, and then N-methylpyrrolidone was added and mixed to form a uniform slurry. The slurry was applied to an aluminum foil current collector with a spatula, dried, and cut into discs with a diameter of 10 mm. The discs were placed in a glove box to obtain the positive electrode sheets of the lithium-ion battery.

[0134] The positive electrode sheets of lithium ion batteries prepared in Comparative Example 1 and Examples 1 to 4 were respectively assembled with lithium sheets, commercial polypropylene separators and lithium secondary electrolytes to form 2032 button batteries. The cycle performance and rate performance of the positive electrode sheets of lithium ion batteries were tested using the Xinwei battery testing system. The cycle performance test was carried out in the voltage range of 1.0V to 3.5V and at a rate of 50mAh·g -1 The rate performance test was carried out in the voltage range of 1.0V~3.5V, respectively at 25mA·g -1 , 50mA·g -1 , 100mA·g -1 , 150mA·g -1 , 200mA·g -1 and 20 mA·g -1 Ten cycles were performed at the current density of 1000 and 1000 respectively. The test results are shown in Table 1. Figure 1 and Figure 2 shown.

[0135] Table 1. Capacity retention of vanadium-based electrode materials after 100 cycles in Comparative Example 1 and Examples 1 to 4.

[0136]

[0137] Table 1 shows the retention capacity of the vanadium-based electrode materials of Comparative Example 1 and Examples 1 to 4 after 100 cycles. The retention capacity of Comparative Example 1 after the cycle is only 53 mAh·g -1The retention capacity after the cycle of Examples 1 to 4 is higher than that of Comparative Example 1, indicating that the vanadium-based electrode materials of Examples 1 to 4 have better cycle performance and charge-discharge capacity.

[0138] Figure 1 1 is a cycle performance diagram of Comparative Example 1 and Examples 1 to 4. The discharge specific capacities of Examples 1 to 4 are all higher than that of Comparative Example 1, and the capacity decay rate is significantly lower than that of Comparative Example 1, indicating that ion exchange improves the cycle stability of the vanadium-based electrode material.

[0139] Figure 2 Figure 2 shows the rate performance of Comparative Example 1 and Examples 1 through 4. At each current density, the discharge specific capacities of Examples 1 through 4 are significantly higher than those of Comparative Example 1, demonstrating that the ion exchange reaction effectively improves the rate performance of the vanadium-based electrode material. In summary, the vanadium-based electrode material provided by the present invention exhibits excellent electrochemical performance.

[0140] Figure 3 The first charge and discharge curves of the vanadium-based electrode materials of Examples 1 to 4 and Comparative Example 1 are shown. Figure 3 The results show that during the first charge and discharge process, a clear charge and discharge platform can be observed for the vanadium-based electrode materials of Examples 1 to 4, indicating that a stable two-phase reaction occurs in Examples 1 to 4, indicating that the vanadium-based electrode materials have better structural stability. At the same time, the average discharge platform of Examples 1 to 4 is significantly higher than the average discharge potential of Comparative Example 1. Therefore, the vanadium-based electrode materials of Examples 1 to 4 have higher specific energy. The charge and discharge platform voltage difference of the vanadium-based electrode materials of Examples 1 to 4 is significantly smaller than that of the vanadium-based electrode material of Comparative Example 1, indicating that the vanadium-based electrode materials of Examples 1 to 4 have higher electronic conductivity and smaller electrochemical polarization.

[0141] Figure 4 The EIS graphs of the vanadium-based electrode materials of Example 4 and Comparative Example 1 of the present invention are shown. According to the EIS graphs, the lithium ion diffusion coefficients of Comparative Example 1 and Example 4 are 1.97×10 -8 cm 2. s -1 and 4.2×10 -8 cm 2. s -1 According to the Nernst-Einstein equation, ionic conductivity is proportional to the lithium ion diffusion coefficient, and it is concluded that Example 4 has higher ionic conductivity than Comparative Example 1. Figure 2 and Figure 4 The results show that the vanadium-based electrode material of Example 4 has higher ionic conductivity and thus exhibits better rate performance.

[0142] Figure 5Thermogravimetric curves of the vanadium-based electrode materials of Example 4 and Comparative Example 1 show no significant mass change within the 300°C range, indicating no significant decomposition, demonstrating good thermal stability. The vanadium-based electrode material of Comparative Example 1 exhibits a slight mass change during heating, due to a small amount of adsorbed water. However, Example 4 exhibits almost no mass change, indicating that the hygroscopic properties of the vanadium-based electrode material in air decrease after the ion exchange reaction, making it more stable.

[0143] Figure 6 The results showed that the vanadium-based electrode material of Example 4 had a nanosheet-like morphology and a high specific surface area, which shortened the transport paths of ions and electrons and enhanced reaction kinetics. Elemental analysis showed that the vanadium-based electrode material of Example 4 contained Na, O, V, and Cl, with a high Cl content.

[0144] Figure 7 The results show that the vanadium-based electrode material of Example 4 has oxygen vacancies, and the presence of oxygen vacancies is beneficial to ion diffusion.

[0145] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and variations. The above-mentioned embodiments are only preferred embodiments for fully illustrating the present invention, and their scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art on the basis of the present invention are all within the scope of protection of the present invention, and the scope of protection of the present invention shall be subject to the claims.

Claims

1. A vanadium-based electrode material, characterized in that: The chemical formula of vanadium-based electrode material is: Li x Na y VO 3-z M w , wherein M is selected from F, Cl or Br; When M is selected from F, 0<x<0.1, 0<y<1, 0<z<0.1, 0<w≤0.1; When M is selected from Cl or Br, 0<x<1, 0<y<1, 0<z<0.2, 0.1≤w≤1; Vanadium-based electrode material Li x Na y VO 3-z M w The crystal structure belongs to the orthorhombic system, and the vanadium-based electrode material Li x Na y VO 3-z M w With oxygen vacancy defects.

2. A method for preparing the vanadium-based electrode material according to claim 1, characterized in that: The steps include: The vanadium source is added to a soluble sodium salt aqueous solution, mixed evenly, and then heated and stirred at 50°C to 70°C for 1h to 10h to obtain a sample; The sample was freeze-dried to obtain β-NaVO3 powder; β-NaVO3 powder is added to the alcohol solution of lithium halide and subjected to solvent thermal treatment. At this time, ion exchange occurs, and Na + With Li + Exchange, M - and VO3 - Ion exchange to obtain vanadium-based electrode materials; Wherein, the lithium halide is selected from lithium fluoride, lithium chloride or lithium bromide.

3. The method for preparing a vanadium-based electrode material according to claim 2, wherein: The molar ratio of the vanadium source to the soluble sodium salt is 0.9-1.2:

1.

4. The method for preparing a vanadium-based electrode material according to claim 2, wherein: The concentration of the soluble sodium salt aqueous solution is greater than 0.1 mol / L and less than or equal to the saturation concentration.

5. The method for preparing a vanadium-based electrode material according to claim 2, wherein: The conditions of the solvent thermal treatment are: heating at 50°C~120°C for 3h~48h.

6. The method for preparing a vanadium-based electrode material according to claim 2, wherein: The molar ratio of lithium halide to β-NaVO3 powder is 5~10:

1.

7. The method for preparing a vanadium-based electrode material according to claim 2, wherein: The solvent of the alcohol solution of lithium halide is one of ethanol, propanol and pentanol or a mixture of two of them.

8. A positive electrode plate for a lithium-ion battery, characterized in that: The positive electrode sheet of a lithium-ion battery is made from the vanadium-based electrode material according to claim 1, a conductive agent, a binder and a current collector.

9. The positive electrode plate of a lithium-ion battery according to claim 8, characterized in that: The vanadium-based electrode material, conductive agent and binder are mixed together in a solvent to obtain a slurry, the slurry is evenly coated on a current collector, and after the solvent is evaporated, a positive electrode sheet of a lithium-ion battery is obtained.

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