A sodium vanadium phosphate composite material with a three-dimensional carbon network structure, its preparation method and application

Abstract

This invention provides a sodium vanadium phosphate composite material with a three-dimensional carbon network structure, its preparation method, and its application, relating to the field of sodium-ion battery electrode materials technology. The preparation method is as follows: vanadium source, sodium source, phosphorus source, reducing agent, and anhydrous ethanol are mixed and ground to obtain a mixed slurry; the mixed slurry is subjected to alternating solvothermal treatment and ball milling, followed by carbonization to obtain a sodium vanadium phosphate composite material with both surface carbon coating and an internal three-dimensional carbon skeleton. Solvothermal treatment coats the exterior with a carbon layer, while ball milling encapsulates a carbon conductive network within the sodium vanadium phosphate material. The alternating hydrothermal and ball milling processes, supplemented by solid-phase carbonization, cause the sodium vanadium phosphate particles to knead together, forming a three-dimensional conductive network on both the surface and inside the sodium vanadium phosphate grains. This not only improves the poor conductivity of sodium vanadium phosphate but also reduces the grain size, improves structural stability, and enhances the material's initial efficiency, specific capacity, and cycle life.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery electrode materials technology, and in particular to a sodium vanadium phosphate composite material with a three-dimensional carbon network structure, its preparation method and application. Background Technology

[0002] In the field of advanced energy storage technology, lithium-ion batteries are used in important areas such as portable electronic devices, electric vehicles, and smart grids. However, the abundance of lithium in the Earth's crust is low (only 0.0065%), resulting in low reserves and high costs of lithium-ion battery raw materials, hindering its large-scale application. Furthermore, the development of lithium-ion batteries still faces unresolved issues, such as: relatively low energy density, meaning they cannot store large amounts of energy; relatively slow charge and discharge rates, limiting their application in certain high-power demand scenarios; and capacity decay and shortened cycle life with increasing cycle count. Sodium, on the other hand, is the most abundant metallic element in the Earth's crust (2.74%), and its reserves in the ocean are also enormous. Compared to lithium, sodium materials are lower in cost, more widely available, and easier to promote and use. Sodium-ion batteries are also considered a promising energy storage technology, particularly for use as stationary batteries in smart grids, solar energy, and wind energy.

[0003] Rhombic sodium vanadium phosphate (NVP) is a polyanionic material with a robust structure, good ion mobility, and a high theoretical specific capacity (117.6 mAh·g). -1 Sodium vanadium phosphate (CN-P) is an excellent sodium-ion cathode material due to its high operating voltage (up to 3.4V). However, its poor cycle performance, poor conductivity, and complex synthesis process limit its use in sodium-ion batteries. Existing patent applications, such as CN115954456A, disclose a method for preparing carbon-coated CN-P with large-radius ion-doped modification, but this material has low capacity and an unstable voltage plateau. CN115744865A discloses a method for preparing a CN-P cathode material based on iron doping and carbon coating, utilizing solvothermal coating of carbon and iron particles onto CN-P, but the resulting material has low initial efficiency and incomplete coating. CN115719806A discloses a carbon-coated magnesium ion-doped modified CN-P cathode material and its preparation method, designing a carbon-coated magnesium ion-doped CN-P scheme, but its conductivity is poor and its capacity is low. While these solutions have achieved good results, their operation processes are complex and difficult to control. How to disclose a sodium vanadium phosphate composite material with both surface carbon coating and internal three-dimensional carbon skeleton, as well as its preparation method and application, and how to establish a complete three-dimensional conductive network to improve the conductivity and stability of sodium vanadium phosphate, are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium vanadium phosphate composite material with a three-dimensional carbon network structure, its preparation method and application, in order to solve the problems of poor cycle stability, poor conductivity, low first-efficiency and complex modification methods of existing sodium vanadium phosphate materials for sodium-ion batteries.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a sodium vanadium phosphate composite material with a three-dimensional carbon network structure, characterized by comprising the following steps:

[0007] 1) Mix vanadium source, sodium source, phosphorus source, reducing agent and anhydrous ethanol, and grind to obtain a mixed slurry;

[0008] 2) The mixed slurry is subjected to comprehensive processing to obtain a sodium vanadium phosphate composite material intermediate with a three-dimensional carbon network structure;

[0009] 3) Carbonize the sodium vanadium phosphate composite material intermediate with a three-dimensional carbon network structure to obtain a sodium vanadium phosphate composite material with a three-dimensional carbon network structure.

[0010] The integrated treatment includes ball milling and solvothermal treatment.

[0011] Preferably, the vanadium source in step 1) is vanadium pentoxide and / or vanadium trioxide;

[0012] The sodium source is disodium hydrogen phosphate and / or sodium oxalate;

[0013] The phosphorus source is disodium hydrogen phosphate and / or phosphoric acid;

[0014] The reducing agent is oxalic acid and / or vanadium pentoxide.

[0015] Preferably, in step 1), the molar ratio of vanadium source, sodium source, phosphorus source and reducing agent is 2 mol: 3 mol: 3 mol: 3 mol: 0.15-15 mL;

[0016] Preferably, the grinding speed in step 1) is 200-600 r / min, and the grinding time is 1-4 h.

[0017] Preferably, the solvothermal treatment is performed by mixing the slurry to be treated with a sucrose solution and reacting them to complete the solvothermal treatment.

[0018] The ball milling process is as follows: the slurry to be processed is mixed with sucrose and then ball milled to complete the ball milling process;

[0019] The ball milling and solvent heat treatment were repeated 1 to 3 times;

[0020] When the number of ball milling and solvent heat treatments is not 1, the ball milling and solvent heat treatments are performed alternately.

[0021] Preferably, the ball milling speed is 100-1000 r / min, and the ball milling time is 6-12 h;

[0022] The molar ratio of sucrose to phosphorus source added during the ball milling process is 0.5 to 10:1.

[0023] Preferably, the concentration of the sucrose solution used in the solvothermal treatment is 1-30 g / L, and the volume ratio of the sucrose solution to the slurry being treated is 2-5:1.

[0024] The solvent heat treatment temperature is 80–300℃, and the solvent heat treatment time is 2–12 hours.

[0025] Preferably, the carbonization temperature in step 3) is 600–900°C, the heating rate is 0.5–20°C / min, and the carbonization time is 10–24 h.

[0026] This invention provides a method for preparing sodium vanadium phosphate composite material with a three-dimensional carbon network structure.

[0027] This invention also provides an application of sodium vanadium phosphate composite material with a three-dimensional carbon network structure in sodium-ion batteries.

[0028] The present invention has at least the following beneficial effects:

[0029] 1. This invention employs alternating ball milling and solvothermal treatment. Ball milling encapsulates a carbon conductive network within the sodium vanadium phosphate material, while solvothermal treatment coats it with a carbon layer. This combined internal and external three-dimensional conductive network not only conducts electricity but also enhances structural stability. Supplemented by solid-phase carbonization, the sodium vanadium phosphate particles are kneaded together, resulting in a bulk sodium vanadium phosphate composite material with both surface carbon coating and an internal three-dimensional conductive carbon network. Compared to simply coating the surface of sodium vanadium phosphate grains with a carbon layer to form a conductive network, this invention improves the contact between sodium vanadium phosphate and the carbon layer, inhibits particle agglomeration, and forms a three-dimensional conductive network both on and inside the sodium vanadium phosphate grains. This not only improves the poor conductivity of sodium vanadium phosphate but also reduces the grain size, contributing to a simultaneous improvement in material conductivity, initial efficiency, specific capacity, and cycle life.

[0030] 2. When the sodium vanadium phosphate composite material with a three-dimensional carbon network structure prepared by solid-phase carbonization as described in this invention is applied to the cathode material of sodium-ion batteries, the construction of the three-dimensional conductive network not only helps to suppress the growth of particles in high-temperature carbonization and further control the particle size, but also helps to obtain sodium vanadium phosphate cathode material with uniform particle size and monodisperse structure.

[0031] 3. When the sodium vanadium phosphate composite material with a three-dimensional carbon network structure described in this invention is applied to the cathode material of sodium-ion batteries, the contradictory relationship between conductivity, coulombic efficiency, capacity and rate performance can be broken, and it can simultaneously have high coulombic efficiency, high specific capacity and high rate performance. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the molecular aggregation morphology and carbon structure of the sodium vanadium phosphate composite material with a three-dimensional carbon network structure described in this invention under different treatments.

[0033] Figure 2 This is a scanning electron microscope image of the sodium vanadium phosphate composite material with a three-dimensional carbon network structure prepared in Example 1 of the present invention;

[0034] Figure 3 The charge-discharge curve of a sodium-ion button battery assembled using the sodium vanadium phosphate composite material with a three-dimensional carbon network structure prepared in Example 1 of this invention at a current density of 20 mA / g is shown.

[0035] Figure 4 The rate performance diagram shows the sodium-ion button cell assembled using the sodium vanadium phosphate composite material with a three-dimensional carbon network structure prepared in Example 1 of this invention.

[0036] Figure 5 The charge-discharge curve of a sodium-ion button battery assembled from sodium vanadium phosphate composite material with a three-dimensional carbon network structure prepared in Comparative Example 1 of this invention is shown at a current density of 20 mA / g. Detailed Implementation

[0037] This invention provides a method for preparing a sodium vanadium phosphate composite material with a three-dimensional carbon network structure, comprising the following steps:

[0038] 1) Mix vanadium source, sodium source, phosphorus source, reducing agent and anhydrous ethanol, and grind to obtain a mixed slurry;

[0039] 2) The mixed slurry is subjected to comprehensive processing to obtain a sodium vanadium phosphate composite material intermediate with a three-dimensional carbon network structure;

[0040] 3) Carbonize the sodium vanadium phosphate composite material intermediate with a three-dimensional carbon network structure to obtain a sodium vanadium phosphate composite material with a three-dimensional carbon network structure.

[0041] The integrated treatment includes ball milling and solvothermal treatment.

[0042] In this invention, the vanadium source in step 1) is vanadium pentoxide and / or vanadium trioxide;

[0043] The sodium source is disodium hydrogen phosphate and / or sodium oxalate;

[0044] The phosphorus source is disodium hydrogen phosphate and / or phosphoric acid;

[0045] The reducing agent is oxalic acid and / or vanadium pentoxide.

[0046] In this invention, when the sodium source in step 1) is disodium hydrogen phosphate, no additional phosphorus source needs to be added.

[0047] In this invention, the molar volume ratio of vanadium source, sodium source, phosphorus source, reducing agent and anhydrous ethanol in step 1) is 2 mol: 3 mol: 3 mol: 3 mol: 0.15-15 mL, preferably 2 mol: 3 mol: 3 mol: 3 mol: 1-13 mL, more preferably 2 mol: 3 mol: 3 mol: 3 mol: 3-10 mL, and even more preferably 2 mol: 3 mol: 3 mol: 3 mol: 5-8 mL.

[0048] In this invention, the grinding speed in step 1) is 200-600 r / min, preferably 250-550 r / min, more preferably 300-500 r / min, and even more preferably 350-450 r / min; the grinding time is 1-4 h, preferably 1.5-3.5 h, more preferably 2-3 h, and even more preferably 2.5 h; the grinding is preferably ball milling.

[0049] In this invention, the solvothermal treatment is performed by mixing the slurry to be treated with a sucrose solution and reacting them to complete the solvothermal treatment.

[0050] The ball milling process involves mixing the slurry to be processed with sucrose, then ball milling the mixture to complete the process.

[0051] In this invention, the ball milling and solvothermal treatment are repeated 1 to 3 times, preferably 2 to 3 times; wherein, there is no limitation on the order of the first ball milling and the first solvothermal treatment.

[0052] In this invention, when the number of ball milling and solvothermal treatments is not 1, the ball milling and solvothermal treatments are performed alternately.

[0053] In this invention, the ball milling speed is 100-1000 r / min, preferably 300-800 r / min, more preferably 400-700 r / min, and even more preferably 500-600 r / min; the ball milling time is 6-12 h, preferably 7-11 h, more preferably 8-10 h, and even more preferably 9 h.

[0054] In this invention, the molar ratio of sucrose to phosphorus source added during the ball milling process is 0.5 to 10:1, preferably 2 to 8:1, more preferably 4 to 6:1, and even more preferably 5:1.

[0055] In this invention, the concentration of the sucrose solution used in the solvothermal treatment is 1-30 g / L, preferably 5-25 g / L, more preferably 10-20 g / L, and even more preferably 13-18 g / L; the volume ratio of the sucrose solution to the slurry being treated is 2-5:1, preferably 2.5-4.5:1, more preferably 3-4:1, and even more preferably 3.5:1.

[0056] In this invention, the temperature of the solvent heat treatment is 80-300°C, preferably 120-250°C, more preferably 150-220°C, and even more preferably 180-200°C; the time of the solvent heat treatment is 2-12 hours, preferably 4-10 hours, more preferably 5-8 hours, and even more preferably 6-7 hours.

[0057] Figure 1 This is a schematic diagram of the molecular aggregation morphology and carbon structure of the sodium vanadium phosphate composite material with a three-dimensional carbon network structure described in this invention under different treatments. Ball milling can encapsulate a carbon conductive network inside the sodium vanadium phosphate material, while solvothermal treatment can coat it with a carbon layer on the outside.

[0058] In this invention, after the comprehensive treatment is completed, the process further includes a drying step of the sodium vanadium phosphate composite intermediate with a three-dimensional carbon network structure. The drying is preferably vacuum drying, and the drying time is 6 to 10 hours, preferably 6.5 to 9.5 hours, more preferably 7 to 9 hours, even more preferably 7.5 to 8.5 hours, and more preferably 8 hours. The drying temperature is 60 to 80°C, preferably 65 to 75°C, more preferably 68 to 72°C, and more preferably 70°C.

[0059] In this invention, the carbonization temperature in step 3) is 600–900°C, preferably 650–850°C, more preferably 700–800°C, and even more preferably 730–760°C; the heating rate is 0.5–20°C / min, preferably 5–15°C / min, and even more preferably 8–12°C / min; the carbonization time is 10–24 h, preferably 14–20 h, even more preferably 16–18 h, and even more preferably 17 h.

[0060] This invention provides a method for preparing sodium vanadium phosphate composite material with a three-dimensional carbon network structure.

[0061] This invention also provides an application of sodium vanadium phosphate composite material with a three-dimensional carbon network structure in sodium-ion batteries.

[0062] In this invention, when the sodium vanadium phosphate composite material with a three-dimensional carbon network structure is applied to a sodium-ion battery, the conductive agent is preferably Ketjen Black conductive agent.

[0063] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0064] Example 1

[0065] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2.5h to obtain a mixed slurry.

[0066] After ball milling for 2.5 hours, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal treatment, the treated slurry was vacuum dried at 60°C for 8 hours. Then, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar, and the mixture was ball milled at 500 r / min for 9 hours. After the ball milling, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 300°C for 8 hours. After the solvothermal treatment, the intermediate was vacuum dried at 60°C for 8 hours. Then, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar, and the mixture was ball milled at 500 r / min for 9 hours. After ball milling, the above intermediate was vacuum dried at 60°C for 8 hours, then ground and placed in a magnetic boat. It was then placed in a tube furnace for carbonization, heated to 900°C at a rate of 8°C / min, held for 17 hours, and naturally cooled to room temperature to obtain the three-dimensional carbon network sodium vanadium phosphate composite material.

[0067] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0068] Figure 2 The image shown is a scanning electron microscope image of the three-dimensional carbon network sodium vanadium phosphate composite material prepared according to Example 1 of the present invention. It can be seen that the prepared sodium vanadium phosphate has a bulk coating structure, indicating that a three-dimensional carbon network conductive network has been successfully constructed. Figure 3 The charge-discharge curve of the three-dimensional carbon network sodium vanadium phosphate composite material prepared in Example 1 of the present invention at a current density of 20 mA / g. Figure 4 The rate performance diagram shows the sodium-ion button cell produced from the product of Example 1.

[0069] Example 2

[0070] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0071] After ball milling for 2 hours, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar and ball milled at 500 r / min for 9 hours. After ball milling, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200 °C for 8 hours. After the solvothermal reaction was completed, the above intermediate was vacuum dried at 60 °C for 8 hours, and then a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200 °C for 8 hours. After the solvothermal reaction was completed, the above intermediate was vacuum dried at 60 °C for 8 hours, ground, and placed in a magnetic boat. The boat was then placed in a tube furnace for carbonization, and the temperature was increased to 900 °C at a rate of 8 °C / min and held for 17 hours. After natural cooling to room temperature, the three-dimensional carbon network sodium vanadium phosphate composite material was obtained.

[0072] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0073] Example 3

[0074] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0075] After ball milling for 2.5 hours, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal reaction was completed, the intermediate was vacuum dried at 60°C for 8 hours. Then, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball mill jar, and the mixture was ball milled at 500 r / min for 9 hours. After ball milling, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball mill jar, and the mixture was ball milled at 500 r / min for 9 hours. After ball milling, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball mill jar, and the mixture was ball milled at 500 r / min for 9 hours. After three ball milling processes, the above intermediate was vacuum dried at 60°C for 8 hours, then ground and placed in a magnetic boat. It was then placed in a tube furnace for carbonization, heated to 900°C at a rate of 8°C / min, held for 17 hours, and then naturally cooled to room temperature to obtain the three-dimensional carbon network sodium vanadium phosphate composite material.

[0076] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0077] Example 4

[0078] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0079] After ball milling for 2.5 hours, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal reaction was completed, the above intermediate was vacuum dried at 60°C for 8 hours. Then, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball mill jar, and ball milling was performed at 500 r / min for 9 hours. After ball milling, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball mill jar, and ball milling was performed at 500 r / min for 9 hours. After ball milling, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal reaction is completed, the above intermediate is vacuum dried at 60°C for 8 hours, then ground and placed in a magnetic boat. It is then placed in a tube furnace for carbonization, heated to 900°C at a rate of 8°C / min, held for 17 hours, and naturally cooled to room temperature to obtain the three-dimensional carbon network sodium vanadium phosphate composite material.

[0080] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0081] Comparative Example 1

[0082] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0083] After ball milling for 2.5 hours, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal reaction was completed, the intermediate was vacuum dried at 60°C for 8 hours. Then, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar, and the mixture was ball milled at 500 r / min for 9 hours. After ball milling, the intermediate was vacuum dried at 60°C for 8 hours, ground, and placed in a magnetic boat. The boat was then placed in a tube furnace for carbonization, and the temperature was increased to 900°C at a rate of 8°C / min and held for 17 hours. After natural cooling to room temperature, the three-dimensional carbon network sodium vanadium phosphate composite material was obtained.

[0084] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box. Figure 5 This is a charge-discharge curve of the three-dimensional carbon network sodium vanadium phosphate composite material prepared in Comparative Example 1 of this invention at a current density of 20 mA / g. Figure 3 and Figure 5 The comparison shows that, compared to surface coating, the sodium vanadium phosphate bulk composite material, which combines surface carbon coating and internal three-dimensional conductive carbon network, exhibits better first-week coulombic efficiency and capacity.

[0085] Comparative Example 2

[0086] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0087] After ball milling for 2.5 hours, a sucrose solution with a volume twice that of the slurry and a concentration of 18 g / L was added, and the mixture was subjected to solvothermal treatment at 200°C for 8 hours. After the solvothermal reaction was completed, the intermediate was vacuum dried at 60°C for 8 hours, ground, placed in a magnetic boat, and carbonized in a tube furnace. The temperature was increased to 900°C at a rate of 8°C / min, held for 17 hours, and then naturally cooled to room temperature to obtain the three-dimensional carbon network sodium vanadium phosphate composite material.

[0088] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0089] Comparative Example 3

[0090] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0091] After ball milling for 2.5 hours, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar and ball milled at 500 r / min for 9 hours. After ball milling, the above intermediate was vacuum dried at 60 °C for 8 hours, then ground and placed in a magnetic boat. It was then placed in a tube furnace for carbonization, heated to 900 °C at a rate of 8 °C / min, held at that temperature for 17 hours, and then naturally cooled to room temperature to obtain the three-dimensional carbon network sodium vanadium phosphate composite material.

[0092] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0093] Comparative Example 4

[0094] 1.82g vanadium pentoxide, 3.6g sodium dihydrogen phosphate, 3.6g oxalic acid, 10mL anhydrous ethanol, 8 grinding balls with a diameter of 6mm and 16 grinding balls with a diameter of 12mm were placed in a ball milling jar and ball milled at 400r / min for 2h to obtain a mixed slurry.

[0095] After ball milling for 2.5 hours, 10 mL of anhydrous ethanol, 1 g of sucrose, 8 grinding balls with a diameter of 6 mm, and 16 grinding balls with a diameter of 12 mm were added to a ball milling jar and ball milled at 500 r / min for 9 hours. After ball milling, a sucrose solution with a concentration of 18 g / L and a volume twice that of the slurry to be treated was added, and the mixture was subjected to solvothermal treatment at 200 °C for 8 hours. After the solvothermal reaction was completed, the above intermediate was vacuum dried at 60 °C for 8 hours, ground, and placed in a magnetic boat. The boat was then placed in a tube furnace for carbonization, and the temperature was increased to 900 °C at a rate of 8 °C / min and held for 17 hours. After natural cooling to room temperature, the three-dimensional carbon network sodium vanadium phosphate composite material was obtained.

[0096] The three-dimensional carbon network sodium vanadium phosphate composite material prepared by the above method was used to prepare sodium-ion batteries. The specific steps are as follows: The three-dimensional carbon network sodium vanadium phosphate cathode material, polyvinylidene fluoride, and acetylene black were weighed at a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added. After ball milling at a rate of 450 r / min for 4 h, aluminum foil was uniformly coated onto the composite material. After vacuum drying at 80 °C for 24 h, the battery electrode was obtained. The obtained battery electrode was used as the working electrode, and the sodium sheet was used as the counter electrode. Sodium-ion button batteries were assembled in a glove box.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0098] The electrochemical performance of the sodium-ion coin cells prepared in the above examples and comparative examples was tested, and the charge-discharge specific capacity is shown in Table 1.

[0099] Table 1. Charge and discharge data of sodium-ion coin cells prepared in the embodiments and comparative examples of the present invention at a current density of 20 mA / g.

[0100]

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a sodium vanadium phosphate composite material having a three-dimensional carbon network structure, characterized by, The method comprises the following steps: 1) mixing a vanadium source, a sodium source, a phosphorus source, a reducing agent and anhydrous ethanol, and grinding to obtain a mixed slurry; 2) comprehensively treating the mixed slurry to obtain a sodium vanadium phosphate composite material intermediate with a three-dimensional carbon network structure; 3) carbonizing the sodium vanadium phosphate composite material intermediate with the three-dimensional carbon network structure to obtain a sodium vanadium phosphate composite material with the three-dimensional carbon network structure. The comprehensive treatment comprises ball milling treatment and solvothermal treatment, the ball milling treatment and the solvothermal treatment are repeatedly performed 1-3 times, the number of times of the ball milling treatment and the solvothermal treatment is different from 1, and the ball milling treatment and the solvothermal treatment are alternately performed. The solvothermal treatment is that the treated slurry is mixed with a sucrose solution for reaction to complete the solvothermal treatment. The ball milling treatment is that the treated slurry is mixed with sucrose for ball milling to complete the ball milling treatment.

2. The method for preparing a sodium vanadium phosphate composite material with a three-dimensional carbon network structure according to claim 1, characterized in that, In the step 1), the vanadium source is vanadium pentoxide and / or vanadium trioxide; The sodium source is sodium hydrogen phosphate and / or sodium oxalate; The phosphorus source is sodium hydrogen phosphate and / or phosphoric acid; The reducing agent is oxalic acid and / or vanadium pentoxide.

3. The method of claim 2, wherein the method is characterized by: In the step 1), the molar volume ratio of the vanadium source, the sodium source, the phosphorus source, the reducing agent and the anhydrous ethanol is 2mol:3mol:3mol:3mol:0.15-15mL.

4. The method of claim 2 or 3, wherein the method is characterized by, In the step 1), the rotation speed of the grinding is 200-600r / min, and the grinding time is 1-4h.

5. The method of claim 1, wherein the method is characterized by: The rotation speed of the ball milling treatment is 100-1000r / min, and the ball milling treatment time is 6-12h; The molar ratio of the added sucrose to the phosphorus source in the ball milling treatment process is 0.5-10:

1.

6. The method of claim 1 or 5, wherein the method is characterized by: The concentration of the sucrose solution used in the solvothermal treatment is 1-30g / L, and the volume ratio of the sucrose solution to the treated slurry is 2-5:1; The temperature of the solvothermal treatment is 80-300℃, and the solvothermal treatment time is 2-12h.

7. The method of claim 6, wherein the method is characterized by: In the step 3), the carbonization treatment temperature is 600-900℃, the heating rate is 0.5-20℃ / min, and the carbonization treatment time is 10-24h.

8. A sodium vanadium phosphate composite material with a three-dimensional carbon network structure obtained by the preparation method of the sodium vanadium phosphate composite material with the three-dimensional carbon network structure according to any one of claims 1-7.

9. The sodium vanadium phosphate composite material with the three-dimensional carbon network structure according to claim 8 is applied to a sodium ion battery.

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