Soft-hard carbon coated sodium vanadium phosphate composite material, preparation method and application
By coating the sodium vanadium phosphate positive electrode material with a soft-hard carbon composite, the problems of poor conductivity and rate performance were solved, high specific capacity, excellent rate performance and cycle stability were achieved, and its commercial application was promoted.
Patent Information
- Application Number
- CN202510639407.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2025-03-25
- Filing Date
- 2025-05-19
- Publication Date
- 2025-09-12
AI Technical Summary
Existing sodium vanadium phosphate positive electrode materials have problems with poor conductivity and rate performance, which limits their commercial application.
A soft-hard carbon composite method is adopted in which a soft carbon layer and a hard carbon layer are coated with sodium vanadium phosphate to form a composite material, thereby improving the electrical conductivity and electrochemical properties of the material.
The specific capacity, rate performance and cycle stability of the material are significantly improved, achieving excellent electrochemical performance, and is suitable for sodium ion battery positive electrode materials.
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Figure CN120637418A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of sodium ion batteries, and in particular relates to a preparation method and application of a soft-hard coated sodium vanadium phosphate positive electrode material. Background Art
[0002] With the continuous advancement of science and technology and rapid population and economic growth, electricity consumption is increasing year by year. The reserves of non-renewable energy sources such as coal and oil are dwindling, while the overexploitation of fossil fuels has brought immeasurable consequences. Greenhouse gas emissions, primarily carbon dioxide, have contributed to rising global temperatures, rising sea levels, and vegetation destruction, among other ecological and environmental issues. These factors have also greatly promoted the development of new energy sources such as hydrogen, wind, and solar power. These sustainable energy sources require efficient energy storage systems to convert them into electricity. Among the various energy storage systems, batteries are one of the most promising technologies.
[0003] Over the past few decades, lithium-ion batteries have been widely used in our daily lives due to their high operating voltage, long lifespan, high safety, environmental friendliness, and lack of memory effect. These batteries are used in mobile phones, laptops, cars, and large-scale energy storage systems. However, with their widespread use, many challenges have also emerged. 70% of the Earth's lithium resources are located in South America, with uneven distribution. As lithium resources become increasingly depleted, the price of lithium ore is rising. Furthermore, despite the advanced technology of lithium-ion batteries, electric vehicle fires and explosions are frequent. This poses new challenges to future energy development, and the development of alternatives to lithium-ion batteries is urgent. Sodium, an element in the same main group as lithium, is more abundant and less expensive in the Earth's crust. Furthermore, sodium-ion batteries share similar operating principles, allowing them to be manufactured using the same production processes as lithium-ion batteries, thus reducing costs. Therefore, sodium-ion batteries are more suitable for large-scale energy storage.
[0004] At present, there are three main directions for positive electrode materials of sodium ion batteries, namely oxides, polyanions and Prussian blue positive electrode materials. Sodium vanadium phosphate (NVP) is the most widely used and studied polyanion material, which has a unique NASICON framework structure and a capacity of 117.6 mAh g -1 NVP has the advantages of high theoretical specific capacity, high voltage platform of 3.4V, low cost, strong cycle ability, high safety, good ionic conductivity and high energy density. However, NVP also has some defects, such as low crystallinity, low electronic conductivity, low specific surface area and large sodium ion radius, which limit the commercialization progress of NVP. Therefore, how to improve the conductivity of sodium vanadium phosphate and exert its material activity has become the key to improving the rate performance, cycle performance and capacity of sodium vanadium phosphate and promoting the commercial application of sodium vanadium phosphate positive electrode materials. Summary of the Invention
[0005] The purpose of the present invention is to provide a soft-hard carbon composite sodium vanadium phosphate electrode material and a preparation method. The preparation process is simple and the energy consumption is low. The obtained sodium vanadium phosphate carbon composite material has good electrochemical properties, which solves the problems of poor conductivity and rate performance of existing sodium vanadium phosphate positive electrode materials.
[0006] In order to achieve the above object, the present invention adopts the following technical solutions:
[0007] A soft-hard carbon-coated sodium vanadium phosphate composite material comprises sodium vanadium phosphate co-coated with a soft carbon layer and a hard carbon layer.
[0008] Furthermore, the composite material is prepared by the following method:
[0009] (1) dispersing a soft carbon source, a hard carbon source, a sodium source, a vanadium source, and a phosphorus source in ethanol to obtain a mixed solution;
[0010] (2) The mixed solution was transferred to a ball mill and ball milled at a speed of 400 r / min.
[0011] (3) After the ball milling, the liquid is dried to obtain a precursor, which is placed in an inert atmosphere (hydrogen-argon mixture 5% / 95%), pre-calcined at 300° C. for 1 hour, and then calcined at 900° C. to obtain the composite material.
[0012] Furthermore, the molar ratio of the sodium source, the vanadium source and the phosphorus source is 3:2:3.
[0013] Furthermore, the soft carbon source is perylenetetracarboxylic dianhydride, and the hard carbon source is glucose.
[0014] Furthermore, the sodium source is selected from at least one of sodium carbonate, sodium bicarbonate, and sodium chloride.
[0015] Furthermore, the vanadium source is selected from at least one of vanadium acetylacetonate, ammonium metavanadate, and vanadium pentoxide.
[0016] Furthermore, the phosphorus source is selected from at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and phosphoric acid.
[0017] Furthermore, the ball milling time is 8 to 12 hours.
[0018] Furthermore, the calcination time is 6 to 12 hours.
[0019] On this basis, the present invention also provides the use of the soft-hard carbon-coated sodium vanadium phosphate composite material as a positive electrode material for sodium ion batteries, and tests its electrochemical performance. For example, the soft-hard carbon-coated sodium vanadium phosphate composite material is ground with a conductive agent and a binder in a ratio of 7:2:1. After thorough mixing, NMP is added to form a uniform slurry. The slurry is then coated on aluminum foil as a test electrode. Sodium metal is used as the counter electrode, and the electrolyte is 1M NaClO4 in PC with 10.0% FEC. A sodium half-cell is prepared to test its electrochemical performance. The conductive agent used is acetylene black, and the binder is PVDF. The method for assembling and preparing the positive electrode material for sodium ion batteries can also refer to existing methods.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] (1) The present invention uses a simple ball milling method and high-temperature annealing to synthesize sodium vanadium phosphate positive electrode materials with different soft-hard carbon ratios. The preparation method is simple and reliable, with a short process and low cost, and has good industrial prospects.
[0022] (2) The present invention improves the specific capacity, rate performance and cycle stability of the material through the synergistic effect between soft and hard carbon. At the same time, the carbon layer provides a good transmission path for electrons and sodium ions, thereby improving the kinetic properties of the material. The unique and stable NASICON structure and the excellent carbon layer structure can effectively buffer the volume expansion of the material and improve the cycle stability of the material.
[0023] (3) The soft-hard carbon-coated sodium vanadium phosphate composite material of the present invention is used as a positive electrode material to prepare sodium ion batteries, showing excellent electrochemical performance. At a rate of 1C, the specific capacity reaches 100.9 mAh / g, and after 5000 cycles at 20C, it has a specific capacity of 82.3 mA h / g, and the capacity retention rate is as high as 100.1%. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 These are the X-ray diffraction patterns (XRD) of the soft-hard carbon-coated sodium vanadium phosphate composite materials prepared in Examples 1, 2, 3, 4, and 5.
[0025] Figure 2 This is a scanning electron microscope (SEM) image of the soft-hard carbon-coated sodium vanadium phosphate composite material prepared in Example 4.
[0026] Figure 3 This is the charge and discharge curve of the sodium ion battery assembled with the soft-hard carbon-coated sodium vanadium phosphate composite material prepared in Example 4 at a 1C rate.
[0027] Figure 4This is a graph of the cycling performance of a sodium ion battery assembled with the soft-hard carbon-coated sodium vanadium phosphate composite material prepared in Example 4 at different rates.
[0028] Figure 5 This is a 20C rate cycling performance diagram of a sodium ion battery assembled with the soft-hard carbon-coated sodium vanadium phosphate composite material prepared in Example 4. DETAILED DESCRIPTION
[0029] In order to better understand the present invention, five experiments with different ratios of soft and hard carbon are conducted below in conjunction with specific examples to further illustrate the content of the present invention. However, the content of the present invention is not limited to the following examples.
[0030] Example 1
[0031] First, weigh 1.5 mmol (0.1590 g) of anhydrous sodium carbonate, 2.0 mmol (0.2342 g) of ammonium metavanadate, 3.0 mmol (0.3451 g) of ammonium dihydrogen phosphate, and 0.20 g of perylenetetracarboxylic dianhydride (PTCDA) into an agate ball mill and add 20 ml of anhydrous ethanol. After weighing the chemicals, transfer the ball mill to a ball mill and set the mill program. One cycle consists of 15 minutes of forward rotation, 3 minutes of rest, 15 minutes of reverse rotation, and 3 minutes of rest. This cycle is repeated 16 times, or 8 hours of ball milling. After ball milling, the resulting red slurry is dried in a forced-air drying oven at 60°C for 2 hours. After drying the anhydrous ethanol, a red powder is obtained. The red powder is then transferred to an agate mortar for further grinding. After 30 minutes of grinding, the powder is transferred to a crucible and calcined in a quartz tube furnace. The calcination atmosphere is a mixed inert atmosphere with a volume ratio of argon and hydrogen of 95:5. The heating rate is 10℃ / min. It is first pre-calcined at 300℃ for 1 hour, and then heated to 900℃ and calcined for 6 hours to obtain a soft carbon-coated sodium vanadium phosphate positive electrode material.
[0032] The X-ray diffraction pattern (XRD) of the prepared soft carbon coated sodium vanadium phosphate cathode material is shown in Figure 1 .
[0033] The sodium ion battery composite cathode material prepared in this example was assembled with sodium sheets into a button-type half-cell. Electrochemical performance tests showed that the soft carbon-coated sodium vanadium phosphate cathode material exhibited good electrochemical performance. Constant current charge and discharge tests at a 1C rate showed an initial discharge capacity of 83.5 mAh g -1 After 100 cycles, the specific capacity can still be maintained at 81.6 mAh g -1 The constant current charge and discharge test was carried out at a rate of 10C, and its first discharge capacity can reach 82.1mAh g -1 After 1000 cycles, the specific capacity can still be maintained at 78.3 mAh g-1 .
[0034] Example 2
[0035] First, 1.5 mmol (0.1590 g) of anhydrous sodium carbonate, 2.0 mmol (0.2342 g) of ammonium metavanadate, 3.0 mmol (0.3451 g) of ammonium dihydrogen phosphate, 0.05 g of anhydrous glucose, and 0.15 g of perylenetetracarboxylic dianhydride (PTCDA) were weighed and placed in an agate ball mill. 20 ml of anhydrous ethanol was added. After weighing the chemicals, the ball mill was transferred to a ball mill and programmed. One cycle consisted of 15 minutes of forward rotation, 3 minutes of rest, 15 minutes of reverse rotation, and 3 minutes of rest. A total of 16 cycles, or 8 hours of ball milling, were performed. After ball milling, the resulting red slurry was dried in a forced-air drying oven at 60°C for 2 hours. The anhydrous ethanol was dried to obtain a red powder. The red powder was then transferred to an agate mortar for further grinding. After 30 minutes of grinding, the powder was transferred to a crucible and calcined in a quartz tube furnace. The calcination atmosphere is a mixed inert atmosphere with a volume ratio of argon and hydrogen of 95:5. The heating rate is 10℃ / min. It is first pre-calcined at 300℃ for 1 hour, and then heated to 900℃ and calcined for 6 hours to obtain a soft-hard carbon-coated sodium vanadium phosphate positive electrode material.
[0036] The X-ray diffraction pattern (XRD) of the prepared soft-hard carbon coated sodium vanadium phosphate cathode material is shown in Figure 1 .
[0037] The sodium ion battery composite cathode material prepared in this example was assembled with sodium sheets into a button-type half-cell. Electrochemical performance tests showed that the soft-hard carbon-coated sodium vanadium phosphate cathode material exhibited good electrochemical performance. Constant current charge and discharge tests at a 1C rate showed an initial discharge capacity of 99.2 mAh g -1 After 100 cycles, the specific capacity can still be maintained at 94.3 mAh g -1 The constant current charge and discharge test was carried out at a rate of 10C, and its first discharge capacity can reach 90.9mAh g -1 After 1000 cycles, the specific capacity can still be maintained at 89.9 mAh g -1 .
[0038] Example 3
[0039] First, 1.5 mmol (0.1590 g) of anhydrous sodium carbonate, 2.0 mmol (0.2342 g) of ammonium metavanadate, 3.0 mmol (0.3451 g) of ammonium dihydrogen phosphate, 0.10 g of anhydrous glucose, and 0.10 g of perylenetetracarboxylic dianhydride (PTCDA) were weighed and placed in an agate ball mill. 20 ml of anhydrous ethanol was added. After weighing the chemicals, the ball mill was transferred to a ball mill and programmed. One cycle consisted of 15 minutes of forward rotation, 3 minutes of rest, 15 minutes of reverse rotation, and 3 minutes of rest. A total of 16 cycles, or 8 hours of ball milling, were performed. After ball milling, the resulting red slurry was dried in a forced-air drying oven at 60°C for 2 hours. The anhydrous ethanol was dried to obtain a red powder. The red powder was then transferred to an agate mortar for further grinding. After 30 minutes of grinding, the powder was transferred to a crucible and calcined in a quartz tube furnace. The calcination atmosphere is a mixed inert atmosphere with a volume ratio of argon and hydrogen of 95:5. The heating rate is 10℃ / min. It is first pre-calcined at 300℃ for 1 hour, and then heated to 900℃ and calcined for 6 hours to obtain a soft-hard carbon-coated sodium vanadium phosphate positive electrode material.
[0040] The X-ray diffraction pattern (XRD) of the prepared soft-hard carbon coated sodium vanadium phosphate cathode material is shown in Figure 1 .
[0041] The sodium ion battery composite cathode material prepared in this example was assembled with sodium sheets into a button-type half-cell. Electrochemical performance tests showed that the soft-hard carbon-coated sodium vanadium phosphate cathode material exhibited good electrochemical performance. Constant current charge and discharge tests at a 1C rate showed an initial discharge capacity of 93.8 mAh g -1 After 100 cycles, the specific capacity can still be maintained at 95.0 mAh g -1 The constant current charge and discharge test was carried out at a rate of 10C, and its first discharge capacity can reach 97.8mAh g -1 After 1000 cycles, the specific capacity can still be maintained at 99.0 mAh g -1 .
[0042] Example 4
[0043] First, 1.5 mmol (0.1590 g) of anhydrous sodium carbonate, 2.0 mmol (0.2342 g) of ammonium metavanadate, 3.0 mmol (0.3451 g) of ammonium dihydrogen phosphate, 0.15 g of anhydrous glucose, and 0.05 g of perylenetetracarboxylic dianhydride (PTCDA) were weighed and placed in an agate ball mill. 20 ml of anhydrous ethanol was added. After weighing the chemicals, the ball mill was transferred to a ball mill and programmed. One cycle consisted of 15 minutes of forward rotation, 3 minutes of rest, 15 minutes of reverse rotation, and 3 minutes of rest. A total of 16 cycles, or 8 hours of ball milling, were performed. After ball milling, the resulting red slurry was dried in a forced-air drying oven at 60°C for 2 hours. The anhydrous ethanol was dried to obtain a red powder. The red powder was then transferred to an agate mortar for further grinding. After 30 minutes of grinding, the powder was transferred to a crucible and calcined in a quartz tube furnace. The calcination atmosphere is a mixed inert atmosphere with a volume ratio of argon and hydrogen of 95:5. The heating rate is 10℃ / min. It is first pre-calcined at 300℃ for 1 hour, and then heated to 900℃ and calcined for 6 hours to obtain a soft-hard carbon-coated sodium vanadium phosphate positive electrode material.
[0044] The X-ray diffraction pattern (XRD) of the prepared soft-hard carbon coated sodium vanadium phosphate cathode material is shown in Figure 1 The obtained soft-hard carbon coated sodium vanadium phosphate cathode material is shown in the scanning electron microscope (SEM) Figure 2 ,Depend on Figure 2 It can be seen that the soft-hard carbon coated sodium vanadium phosphate positive electrode material sample presents irregular block particles and contains many gaps.
[0045] The sodium ion battery composite cathode material prepared in this example was assembled with sodium sheets into a button-type half-cell. Electrochemical performance tests showed that the soft-hard carbon-coated sodium vanadium phosphate cathode material exhibited good electrochemical performance. Constant current charge and discharge tests at a 1C rate showed an initial discharge capacity of 101.6 mAh g -1 After 100 cycles, the specific capacity can still be maintained at 99.8 mAh g -1 , Figure 3 This is the first cycle charge and discharge curve, from Figure 3 It can be found that the material has a voltage platform at around 3.4V, corresponding to V 3+ / V 4+ The constant current charge and discharge test was carried out at a rate of 10C, and its first discharge capacity could reach 102.1mAh g -1 After 1000 cycles, the specific capacity can still be maintained at 102.4 mAh g -1 . Figure 4 This is the rate performance diagram of the soft-hard carbon coated sodium vanadium phosphate cathode material. Figure 4It can be seen that the material's specific capacity remains very stable after undergoing a current shock from a low rate to a high rate and then back to a low rate, showing excellent stability and rate performance. In particular, in a long cycle test at a rate of 20C, its first discharge specific capacity is 81.8 mAh g -1 After 5000 cycles, the specific capacity can still be maintained at 82.3 mAh g -1 ,like Figure 5 As shown, the capacity retention rate is as high as 100.6%.
[0046] Example 5
[0047] First, weigh 1.5mmol (0.1590g) of anhydrous sodium carbonate, 2.0mmol (0.2342g) of ammonium metavanadate, 3.0mmol (0.3451g) of ammonium dihydrogen phosphate, and 0.20g of anhydrous glucose and place them in an agate ball mill jar. Add 20ml of anhydrous ethanol. After weighing the drugs, transfer the ball mill jar to a ball mill and set the ball mill program. Run forward for 15 minutes, stop for 3 minutes, reverse for 15 minutes, and stop for 3 minutes. This is one cycle, and a total of 16 cycles, or 8 hours of ball milling, are repeated. After the ball milling is completed, the resulting red slurry is placed in a forced air drying oven at 60°C and dried for 2 hours. After the anhydrous ethanol is dried, a red powder is obtained. The red powder is then transferred to an agate mortar for further grinding. After grinding for 30 minutes, the powder is transferred to a crucible and the crucible is placed in a tubular furnace quartz tube for calcination. The calcination atmosphere is a mixed inert atmosphere with a volume ratio of argon and hydrogen of 95:5. The heating rate is 10℃ / min. It is first pre-calcined at 300℃ for 1 hour, and then heated to 900℃ and calcined for 6 hours to obtain a hard carbon-coated sodium vanadium phosphate positive electrode material.
[0048] The X-ray diffraction pattern (XRD) of the prepared hard carbon coated sodium vanadium phosphate cathode material is shown in Figure 1 .
[0049] The sodium ion battery composite cathode material prepared in this example was assembled with sodium sheets into a button-type half-cell. Electrochemical performance tests showed that the hard carbon-coated sodium vanadium phosphate cathode material exhibited good electrochemical performance. Constant current charge and discharge tests at a 1C rate showed an initial discharge capacity of 97.6 mAh g -1 After 100 cycles, the specific capacity can still be maintained at 95.6 mAh g -1 The constant current charge and discharge test was carried out at a rate of 10C, and its first discharge capacity can reach 93.8mAh g -1 After 1000 cycles, the specific capacity can still be maintained at 88.6 mAh g -1 .
[0050] Matters not covered by the present invention are known technologies.
[0051] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.
Claims
1. A soft-hard carbon-coated sodium vanadium phosphate composite material, characterized in that: The invention comprises sodium vanadium phosphate coated with a soft carbon layer and a hard carbon layer.
2. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 1, characterized in that: The preparation method of the composite material comprises the following steps: (1) dispersing a soft carbon source, a hard carbon source, a sodium source, a vanadium source, and a phosphorus source in ethanol to obtain a mixed solution; (2) The mixed solution was transferred to a ball mill and ball milled at a speed of 400 r / min. (3) After the ball milling, the liquid is dried to obtain a precursor, and the precursor is placed in an inert atmosphere and calcined at 900° C. to obtain the composite material.
3. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 2, characterized in that: The molar ratio of the sodium source, the vanadium source and the phosphorus source is 3:2:
3.
4. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 3, characterized in that: The soft carbon source is perylenetetracarboxylic dianhydride, and the hard carbon source is glucose.
5. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 3, characterized in that: The sodium source is selected from at least one of sodium carbonate, sodium bicarbonate and sodium chloride.
6. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 3, characterized in that: The vanadium source is selected from at least one of vanadium acetylacetonate, ammonium metavanadate, and vanadium pentoxide.
7. The soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 3, characterized in that: The phosphorus source is selected from at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and phosphoric acid.
8. The method for preparing the soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 2, characterized in that: The ball milling time is 8 to 12 hours.
9. The method for preparing the soft-hard carbon-coated sodium vanadium phosphate composite material according to claim 2, characterized in that: The calcination time is 6 to 12 hours.
10. Use of the soft-hard carbon-coated sodium vanadium phosphate composite material according to any one of claims 1 to 9, characterized in that: Used as positive electrode material for sodium ion batteries.