Cerium ion doped thermal cracking carbon coated sodium vanadium fluorophosphate positive electrode material, and preparation method and application thereof
The sodium vanadium fluorine phosphate positive electrode material prepared through cerium ion doping and microwave sintering processes solves the problems of low material conductivity and high energy consumption of traditional methods, and achieves efficient and uniform material preparation, improving electrochemical performance.
Patent Information
- Application Number
- CN202510434327.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2025-08-08
AI Technical Summary
In the prior art, the intrinsic conductivity of the sodium vanadium fluorine phosphate cathode material is low, which limits its application. In addition, the traditional ion doping modification method has high energy consumption and long production time, making it difficult to meet the demand for high efficiency and energy saving.
Thermal cracked carbon-coated sodium vanadium phosphate positive electrode material was prepared by cerium ion doping combined with microwave sintering. Through vacuum freeze-drying and microwave sintering processes, the production time was shortened and the electronic conductivity and particle distribution uniformity of the material were improved.
The prepared materials have good cycle stability and electron conductivity, and the particles are evenly distributed, which improves the electrochemical reaction efficiency and the electrochemical performance of the materials.
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Figure CN120440872A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of sodium ion battery positive electrode materials, and in particular relates to a cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate positive electrode material, a preparation method and uses thereof. Background Art
[0002] After decades of development, lithium-ion batteries have reached technological maturity and widespread application in various fields. Currently, a new type of energy storage device is needed to complement and expand the scope of lithium-ion batteries. Sodium-ion batteries share many similar chemical properties with lithium-ion batteries and are considered the most promising new energy storage device. Sodium vanadium fluorophosphate, as a positive electrode material for sodium-ion batteries, has advantages such as a stable open three-dimensional framework structure and high energy density. However, the low intrinsic conductivity of this material due to the presence of insulating [PO4] limits its further application.
[0003] At present, sodium vanadium fluorophosphate is usually modified by carbon coating, ion doping, and particle micromorphology design. Ion doping is one of the effective ways to improve the electrochemical properties of sodium vanadium fluorophosphate. By doping with cerium ions, the ion transmission channel can be effectively improved, the resistance of ions in the diffusion process can be reduced, and the ion transmission efficiency can be improved, thereby achieving the effect of improving the electrochemical performance of sodium vanadium fluorophosphate. However, at this stage, the ion doping modification method is more of a sol-gel method combined with high-temperature sintering in a tubular furnace. There are problems such as high energy consumption and long production time. Therefore, it is urgent to find a more efficient and energy-saving process. Summary of the Invention
[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate positive electrode material, a preparation method and uses. The sodium vanadium fluorophosphate positive electrode material prepared by the present invention has uniform particle distribution, good cycle stability, rate resistance and electronic conductivity.
[0005] To achieve the above object, the technical solution adopted by the present invention to solve the technical problem is: The present invention aims to provide a method for preparing a cerium ion-doped pyrolyzed carbon-coated sodium vanadium fluorophosphate cathode material, comprising the following steps: (1) Dissolve the vanadium source, phosphorus source, sodium source, fluorine source, cerium source and reducing agent in deionized water, heat and stir until uniform, and then freeze into a solid; (2) The frozen solid is dehydrated and crushed, and then microwave sintered to obtain a cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate positive electrode material.
[0006] Furthermore, in step (1), the molar ratio of the vanadium source, the phosphorus source, the sodium source, the fluorine source, the cerium source and the reducing agent is 1-3:1-3:2-4:2-4:0.05-0.15:2-4.
[0007] Further, the vanadium source is ammonium metavanadate, sodium metavanadate or vanadium pentoxide; The phosphorus source is ammonium dihydrogen phosphate, sodium dihydrogen phosphate or sodium phosphate; The sodium source is sodium fluoride, sodium carbonate or sodium acetate; The fluoride source is sodium fluoride or ammonium fluoride.
[0008] The reducing agent is one of citric acid, oxalic acid and tartaric acid.
[0009] Furthermore, the reducing agent is citric acid.
[0010] Furthermore, in step (1), the heating and stirring temperature is 65-75°C, and the stirring time is 1-2 h.
[0011] Furthermore, in step (1), the freezing temperature is -30 to -20°C, and the freezing time is 6 to 12 hours.
[0012] Furthermore, in step (2), vacuum freeze drying is used to remove moisture, the freeze drying temperature is -80~-60 ℃, the drying time is 12~24 h, and the pressure is 10~20 Pa.
[0013] Furthermore, the microwave sintering in step (2) is divided into two stages. In the first stage, the temperature is increased to 300-400 °C at a rate of 2-5 °C / min and kept at this temperature for 1-3 h. In the second stage, the temperature is increased to 650-750 °C at a rate of 2-5 °C / min and kept at this temperature for 0.5-2 h.
[0014] Furthermore, the microwave output frequency is 1.55~3.55 GHz, and the microwave output power is 1~2 KW.
[0015] Another object of the present invention is to provide a cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate positive electrode material, which is prepared by the above method.
[0016] Another object of the present invention is to provide the use of the above-mentioned sodium vanadium fluorophosphate positive electrode material in the preparation of sodium ion batteries.
[0017] Beneficial effects of the present invention: 1. The present invention prepares sodium vanadium fluorophosphate positive electrode material by combining vacuum freeze drying and microwave sintering from a sodium vanadium fluorophosphate precursor. During the freeze drying process, the moisture in the material evaporates in the form of gas, and the material's structure and appearance can be well preserved. Compared with the traditional sintering process, the microwave sintering process can heat the material as a whole, shortening the production time and improving production efficiency.
[0018] 2. The present invention prepares a cerium ion-doped thermal cracking carbon-coated sodium vanadium fluorophosphate positive electrode material by doping cerium ions. The agglomeration phenomenon of the material particles after doping and modification is significantly weakened, and the particle distribution is more uniform, which is conducive to providing more active sites for contact with the electrolyte, improving the electrochemical reaction efficiency, and thus enhancing the electrochemical performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 X-ray diffraction patterns of the pyrolytic carbon-coated sodium vanadium fluorophosphate and the cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate prepared in Examples 1 to 4; Figure 2 The scanning electron microscope images of the pyrolytic carbon-coated sodium vanadium fluorophosphate and the cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate prepared in Examples 1 and 2 are shown; Figure 3 The charge-discharge curves of the pyrolytic carbon-coated sodium vanadium fluorophosphate and the cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate prepared in Examples 1 to 4 after 100 cycles at a current density of 1 C; Figure 4 The charge-discharge curves of the pyrolytic carbon-coated sodium vanadium fluorophosphate and the cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate prepared in Examples 1 to 4 after 10 cycles at a current density of 0.2 to 20°C; Figure 5 The charge-discharge curves of the pyrolysis carbon-coated sodium vanadium fluorophosphate prepared in Comparative Examples 1 to 3 and samples prepared with different reducing agents after 100 cycles at a current density of 1 C; Figure 6 The charge-discharge curves of the pyrolysis carbon-coated sodium vanadium fluorophosphate prepared in Example 1 and Comparative Example 4 and the sample prepared using a traditional tube furnace after 100 cycles at a current density of 1 C; Figure 7 The charge-discharge curves of the cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate prepared in Example 3 and Comparative Example 5 and the cerium ion-doped sample prepared by calcination in a traditional tubular furnace after 100 cycles at 1 C. DETAILED DESCRIPTION
[0020] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.
[0021] Example 1 A pyrolysis carbon-coated sodium vanadium fluorophosphate cathode material, the preparation method of which is as follows: (1) Weigh 1.17 g of ammonium metavanadate into 75 mL of deionized water, heat and stir at 70 °C for 10 min to completely dissolve it, then add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue, add 1.15 g of ammonium dihydrogen phosphate and 0.63 g of sodium fluoride and continue stirring until all substances are mixed evenly, and transfer the sample to a -20 °C freezer and freeze for 12 h; (2) The frozen solid was placed at -80 °C and below 20 Pa for freeze drying for 24 h to obtain a dry precursor; (3) The precursor was placed in an argon atmosphere, and the temperature was first increased from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further increased to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a sodium vanadium fluorophosphate composite material (sample #1).
[0022] Example 2 A cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate cathode material, the preparation method of which is as follows: (1) Weigh 1.15 g of ammonium metavanadate into 75 mL of deionized water, heat and stir at 70 °C for 10 min to completely dissolve it, then add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue, then add 0.11 g of cerium nitrate hexahydrate, 1.15 g of ammonium dihydrogen phosphate, and 0.63 g of sodium fluoride and continue stirring until all substances are mixed evenly, transfer the sample to a -20 °C freezer and freeze for 12 h; (2) The frozen solid was placed at -80 °C and below 20 Pa for freeze drying for 24 h to obtain a dry precursor; (3) The precursor was placed in an argon atmosphere, and the temperature was first increased from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further increased to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a sodium vanadium fluorophosphate composite material (sample #2).
[0023] Example 3 A cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate cathode material, the preparation method of which is as follows: (1) Weigh 1.12 g of ammonium metavanadate into 75 mL of deionized water, heat and stir at 70 °C for 10 min to completely dissolve it, then add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue, then add 0.22 g of cerium nitrate hexahydrate, 1.15 g of ammonium dihydrogen phosphate, and 0.63 g of sodium fluoride and continue stirring until all substances are mixed evenly, transfer the sample to a -30 °C freezer and freeze for 12 h; (2) The frozen solid was placed at -80 °C and below 20 Pa for freeze drying for 24 h to obtain a dry precursor; (3) The precursor was placed in an argon atmosphere, and the temperature was first increased from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further increased to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a sodium vanadium fluorophosphate composite material (sample #3).
[0024] Example 4 A cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate cathode material, the preparation method of which is as follows: (1) Weigh 1.05 g of ammonium metavanadate into 75 mL of deionized water, heat and stir at 70 °C for 10 min to completely dissolve it, then add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue, then add 0.43 g of cerium nitrate hexahydrate, 1.15 g of ammonium dihydrogen phosphate, and 0.63 g of sodium fluoride and continue stirring until all substances are mixed evenly, transfer the sample to a freezer at -25 °C and freeze for 12 h; (2) The frozen solid was placed at -80 °C and below 20 Pa for freeze drying for 24 h to obtain a dry precursor; (3) The precursor was placed in an argon atmosphere, and the temperature was first increased from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further increased to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a sodium vanadium fluorophosphate composite material (sample #4).
[0025] Comparative Example 1 Compared with Example 1, the difference is that the product is prepared by the sol-gel method, and the specific process is as follows: S1: Weigh 1.17 g of ammonium metavanadate into 75 mL of deionized water and heat with stirring at 70 °C for 10 min to completely dissolve it. Then, add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue. Then, add 1.15 g of ammonium dihydrogen phosphate and 0.63 g of sodium fluoride and continue stirring until the solution becomes a sol. S2: Place the sample in an oven at 120 °C for 12 h to obtain dry precursor powder; S3: The precursor was placed in an argon atmosphere, and the temperature was first raised from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further raised to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a pyrolysis carbon-coated sodium vanadium fluorophosphate composite material (sample #5).
[0026] Comparative Example 2 Compared with Comparative Example 1, the difference is that oxalic acid is used as a reducing agent for calcination to prepare the product. The specific process is as follows: S1: Weigh 1.17 g of ammonium metavanadate into 75 mL of deionized water and heat with stirring at 70 °C for 10 min to completely dissolve it. Then, add 1.89 g of oxalic acid and continue stirring for 30 min until the solution turns transparent blue. Then, add 1.15 g of ammonium dihydrogen phosphate and 0.63 g of sodium fluoride and continue stirring until the solution becomes a sol. S2: Place the sample in an oven at 120 °C for 12 h to obtain dry precursor powder; S3: The precursor was placed in an argon atmosphere, and the temperature was first raised from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further raised to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a pyrolysis carbon-coated sodium vanadium fluorophosphate composite material (sample #6).
[0027] Comparative Example 3 Compared with Comparative Example 1, the difference is that tartaric acid is used as a reducing agent for calcination to prepare the product. The specific process is as follows: S1: Weigh 1.17 g of ammonium metavanadate into 75 mL of deionized water and heat with stirring at 70 °C for 10 min to completely dissolve it. Then, add 2.25 g of tartaric acid and continue stirring for 30 min until the solution turns transparent blue. Then, add 1.15 g of ammonium dihydrogen phosphate and 0.63 g of sodium fluoride and continue stirring until the solution becomes a sol. S2: Place the sample in an oven at 120 °C for 12 h to obtain dry precursor powder; S3: The precursor was placed in an argon atmosphere, and the temperature was first raised from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further raised to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 2 h to obtain a pyrolysis carbon-coated sodium vanadium fluorophosphate composite material (sample #7).
[0028] Comparative Example 4 Compared with Example 1, the difference is that the product is prepared by calcining in a traditional tubular furnace. The specific process is as follows: S1: Weigh 1.17 g of ammonium metavanadate into 75 mL of deionized water and heat with stirring at 70 °C for 10 min to completely dissolve it. Then, add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue. Then, add 1.15 g of ammonium dihydrogen phosphate and 0.63 g of sodium fluoride and continue stirring until all substances are mixed. Transfer the sample to a -20 °C freezer and freeze for 12 h. S2: freeze-dry the frozen solid at -80 °C and below 20 Pa for 24 h to obtain a dry precursor; S3: The precursor was placed in an argon atmosphere, and the temperature was first raised from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further raised to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 6 h to obtain a sodium vanadium fluorophosphate composite material (sample #8).
[0029] Comparative Example 5 Compared with Example 2, the difference is that the product is prepared by calcining in a traditional tubular furnace. The specific process is as follows: S1: Weigh 1.12 g of ammonium metavanadate into 75 mL of deionized water and heat with stirring at 70 °C for 10 min to completely dissolve it. Then, add 2.88 g of citric acid and continue stirring for 30 min until the solution turns transparent blue. Then, add 0.22 g of cerium nitrate hexahydrate, 1.15 g of ammonium dihydrogen phosphate, and 0.63 g of sodium fluoride and continue stirring until all substances are mixed. Transfer the sample to a -20 °C freezer and freeze for 12 h. S2: freeze-dry the frozen solid at -80 °C and below 20 Pa for 24 h to obtain a dry precursor; S3: The precursor was placed in an argon atmosphere, and the temperature was first raised from room temperature to 350 °C at a heating rate of 5 °C / min, and kept at this temperature for 1 h. Then, the temperature was further raised to 700 °C at a heating rate of 5 °C / min and kept at this temperature for 6 h to obtain a sodium vanadium fluorophosphate composite material (sample #9).
[0030] Experimental example 1. X-ray diffraction analysis was performed on samples #1 to 4 to obtain the following Figure 1 The X-ray diffraction patterns are shown. Sample #1 is the product without cerium ion doping and modification, and samples #2 to #4 are the products with cerium ion doping and modification.
[0031] Depend on Figure 1 It can be seen that the main diffraction peaks of the four groups of samples all correspond to the standard diffraction pattern (PDF#89-8485) without other impurity peaks, indicating that the crystal structure of the samples is not destroyed after the cerium ion doping modification treatment, and the prepared samples are still sodium vanadium fluorophosphate.
[0032] 2. Samples #1 and #2 were analyzed by scanning electron microscopy, and the following results were obtained: Figure 2 The SEM images shown are as follows. The left image is sodium vanadium fluorophosphate (sample #1), and the right image is the material modified by cerium doping (sample #3). Figure 2 It can be seen that the particle agglomeration of the sample after cerium ion doping modification is significantly weakened, and the particle distribution is more uniform.
[0033] 3. Assemble samples #1 to #4 into batteries and cycle them 100 times at a current density of 1 C to obtain the following Figure 3 The cross-flow charge-discharge curve shown in the figure shows that the sample doped with 0.22 g of cerium nitrate hexahydrate (sample #3) exhibits better electrochemical performance, and the discharge capacity at the first and last cycles is higher than that of other samples, indicating that the appropriate doping ratio can effectively improve the ion diffusion channel of the sample, increase the ion transfer rate, and also improve the structural stability of the sample and the capacity retention rate of the material.
[0034] 4. Assemble samples #1 to 4 into batteries and set the test voltage to 2 to 4.5 V, and the current density to 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 10 C, and 20 C. After 10 cycles, the charge and discharge curves of samples #1 to 4 are as follows: Figure 4 As shown in the figure, it can be seen that sample #2 has higher electrochemical stability at different current densities, and sample #5 has relatively low capacity at high current density and poor capacity retention.
[0035] 5. Assemble samples #5~7 into batteries and cycle them 100 times at a current density of 1 C to obtain the following Figure 5 The cross-current charge and discharge curve shown in the figure shows that sample #5 exhibits better cycle performance, and its first-cycle discharge capacity and capacity retention rate are better than those of other samples.
[0036] 6. Assemble sample #1, sample #3, and sample #8~9 into a battery and cycle it for 100 times at a current density of 1 C to obtain the following Figure 6 and Figure 7The cross-current charge and discharge curves are shown. Figure 6 It can be seen that the first-cycle discharge specific capacity and capacity retention rate of sample #1 are better than those of sample #8, indicating that the microwave sintering preparation designed by the present invention can not only save time, but also the prepared material also exhibits more excellent electrochemical properties.
[0037] from Figure 7 It can be seen that compared with sample #9, sample #3 exhibits better electrochemical performance, and the first-cycle discharge specific capacity and capacity retention rate are significantly improved, indicating that the material prepared by the cerium ion doping combined with microwave sintering method developed by the present invention has more excellent electrochemical performance.
[0038] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A method for preparing a cerium ion-doped pyrolysis carbon-coated sodium vanadium fluorophosphate cathode material, characterized in that: The following steps are involved: (1) Dissolve the vanadium source, phosphorus source, sodium source, fluorine source, cerium source and reducing agent in deionized water, heat and stir until uniform, and then freeze into a solid; (2) The frozen solid is dehydrated and crushed, and then microwave sintered to obtain a cerium ion-doped pyrolytic carbon-coated sodium vanadium fluorophosphate positive electrode material.
2. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of the vanadium source, phosphorus source, sodium source, fluorine source, cerium source and reducing agent is 1~3:1~3:2~4:2~4:0.05~0.15:2~4.
3. The preparation method according to claim 1 or 2, characterized in that The vanadium source is ammonium metavanadate, sodium metavanadate or vanadium pentoxide; The phosphorus source is ammonium dihydrogen phosphate, sodium dihydrogen phosphate or sodium phosphate; The sodium source is sodium fluoride, sodium carbonate or sodium acetate; The fluoride source is sodium fluoride or ammonium fluoride; The reducing agent is one of citric acid, oxalic acid and tartaric acid.
4. The preparation method according to claim 3, characterized in that The reducing agent is citric acid.
5. The preparation method according to claim 1, characterized in that In step (1), the heating and stirring temperature is 65-75°C, and the stirring time is 1-2 h.
6. The preparation method according to claim 1, characterized in that In step (1), the freezing temperature is -30~-20°C, and the freezing time is 6~12 h.
7. The preparation method according to claim 1, characterized in that In step (2), vacuum freeze drying is used to remove moisture. The freeze drying temperature is -80~-60 °C, the drying time is 12~24 h, and the pressure is 10~20 Pa.
8. The preparation method according to claim 1, characterized in that In step (2), the microwave sintering is divided into two stages. In the first stage, the temperature is raised to 300-400 °C at a rate of 2-5 °C / min and kept at this temperature for 1-3 h. In the second stage, the temperature is raised to 650-750 °C at a rate of 2-5 °C / min and kept at this temperature for 0.5-2 h.
9. A cerium ion doped pyrolysis carbon coated sodium vanadium fluorophosphate cathode material, characterized in that: The method according to any one of claims 1 to 8 is used to prepare the product.
10. Use of the sodium vanadium fluorophosphate positive electrode material according to claim 9 in the preparation of sodium ion batteries.