WO2020000166A1 - 钠离子电池正极材料及其制备方法和应用 - Google Patents

钠离子电池正极材料及其制备方法和应用 Download PDF

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WO2020000166A1
WO2020000166A1 PCT/CN2018/092763 CN2018092763W WO2020000166A1 WO 2020000166 A1 WO2020000166 A1 WO 2020000166A1 CN 2018092763 W CN2018092763 W CN 2018092763W WO 2020000166 A1 WO2020000166 A1 WO 2020000166A1
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sodium
sodium ion
ion battery
positive electrode
preparation
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PCT/CN2018/092763
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English (en)
French (fr)
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卓海涛
陈少军
罗垄垄
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深圳大学
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Priority to PCT/CN2018/092763 priority Critical patent/WO2020000166A1/zh
Publication of WO2020000166A1 publication Critical patent/WO2020000166A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention belongs to the field of nanomaterials and electrochemistry, and particularly relates to a method for preparing Na 3 V 2 (PO 4 ) 3 / C as a cathode material of a sodium ion battery.
  • lithium-ion batteries From portable electronic devices to eye-catching electric vehicles, lithium-ion batteries have been widely used as energy storage devices with high energy density. Although lithium-ion batteries now dominate the consumer market, due to the small crustal reserves of lithium (about 0.002%) and uneven distribution, lithium-ion batteries will face double bottlenecks in resources and prices in the future. Sodium is rich in elements, low in price, and has similar chemical properties to lithium. Sodium ion batteries have the advantages and great potential for sustainable use and commercialization in the field of energy storage.
  • Na 3 V 2 (PO 4 ) 3 with sodium superion conductor (NASICON) structure due to its three-dimensional diffusion of sodium ions, relatively high voltage platform (3.4V), high theoretical specific energy (400Whkg -1 ), and excellent Thermal stability makes Na 3 V 2 (PO 4 ) 3 one of the most promising sodium ion cathode materials.
  • Traditional technologies are mainly based on high-temperature solid-phase methods, sol-gel methods, and hydrothermal methods for the preparation of Na 3 V 2 (PO 4 ) 3 / C. These processes have the following advantages and disadvantages:
  • High-temperature solid-phase method is a traditional milling process, although it has its inherent disadvantages, such as high energy consumption, low efficiency, powder is not fine enough, and easy to mix with impurities.
  • the method has the advantages of non-agglomeration of the prepared powder particles, good filling property, low cost, large yield and simple preparation process.
  • the raw materials used in the sol-gel method are first dispersed in a solvent to form a low-viscosity solution, it is possible to obtain molecular-level uniformity in a short period of time. It is likely to be uniformly mixed at the molecular level. As a result of the solution reaction step, it is easy to uniformly and quantitatively incorporate some trace elements to achieve uniform doping at the molecular level.
  • the chemical reaction Compared with the solid-phase reaction, the chemical reaction will be easier to perform, and only requires a lower synthesis temperature. It is generally believed that the component diffusion in the sol-gel system is in the nanometer range, and the component diffusion is in the micron range during the solid-phase reaction. Within the range, the reaction proceeds easily and the temperature is low.
  • the disadvantage is that the raw materials used are relatively expensive, and some raw materials are organic, which is harmful to health; usually the entire sol-gel process takes a long time, which usually takes several days or weeks; there are a lot of micropores in the gel, which are drying. In the process, many gases and organics will escape and shrink.
  • the obtained powder has high purity, good dispersibility, uniformity, narrow distribution, no agglomeration, good crystal form, controllable shape, and good for environmental purification.
  • the disadvantage is that the hydrothermal method requires high temperature and high pressure steps, which makes it more dependent on production equipment, and also greatly increases economic costs and time costs.
  • Na 3 V 2 (PO 4 ) 3 / C powder is firstly made, and then it is made into a slurry with an adhesive to be coated into a film.
  • the existing Na 3 V 2 (PO 4 ) 3 / C powder material has complicated application procedures and high cost, and because of its particle structure and the presence of a binder, the electrode has a large internal resistance, low specific capacity, and weak rate performance. Defects such as poor cycle performance.
  • the object of the present invention is to provide a sodium ion battery cathode material Na 3 V 2 (PO 4 ) 3 / C and a preparation method thereof, in order to solve the high cost caused by the complicated process of the traditional preparation method, or the prepared Na 3 V 2 ( The technical problem of unstable PO 4 ) 3 / C particles.
  • Another object of the present invention is to provide a sodium ion battery positive electrode sheet and a sodium ion battery containing the positive electrode material, so as to solve the problem that the existing sodium ion battery positive electrode sheet and the electrochemical performance of the battery are not ideal.
  • a method for preparing a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps.
  • a method for preparing a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps:
  • a component including a vanadium source, a complexing agent, a sodium source, a phosphoric acid source compound, and a viscous agent in water to form a spinning solution;
  • the precursor of the fiber membrane after the pre-oxidation treatment is sintered to prepare a Na 3 V 2 (PO 4 ) 3 / C nanofiber membrane.
  • the spinning solution is prepared by dissolving a vanadium source, a complexing agent, a sodium source, and a phosphoric acid source compound in water to form a solution, and then adding the compound to an aqueous solution of polyvinyl alcohol. Spinning solution.
  • the vanadium source includes one or more of vanadium pentoxide, ammonium metavanadate, sodium orthovanadate, and sodium metavanadate;
  • the thickener includes one or more of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylonitrile, polystyrene, polyurethane, and polyethylene oxide;
  • the complexing agent includes one or more of anhydrous oxalic acid, citric acid, ascorbic acid, maleic acid, tartaric acid, oxalic acid, malic acid, and lactic acid;
  • the sodium source includes one or more of sodium dihydrogen phosphate, sodium phosphate, sodium carbonate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, and sodium citrate;
  • the phosphoric acid source includes one or more of sodium dihydrogen phosphate, sodium phosphate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate.
  • the molar ratio of the vanadium source to the complexing agent is 1: 1 to 1: 2.
  • the mass ratio of the viscous agent to the vanadium source is 6: 1-8: 1.
  • the process conditions of the electrospinning process are: the voltage selection is 15KV-30KV; the distance between the receiver and the needle is 10cm-20cm; the spinning rate is 0.1ml / h-0.6ml / h; the drum rotation speed is 500r / min-1000r / min; the inner diameter of the needle is 0.4mm-0.8mm.
  • the fibers in the fiber membrane are nano-scale fibers.
  • the hot-pressing process is a hot-pressing process at a pressure of 2-6Kg at 100 ° C-130 ° C for 10-20h;
  • the fiber membrane precursor after the hot-pressing treatment is heated in the air to a temperature of 220 ° C.-260 ° C. for 2-5 h for a temperature of 1 ° C./min-5° C./min.
  • the sintering includes two sinterings in a protective atmosphere, accompanied by organic carbonization, and the initial sintering temperature is 300-400 ° C and the time is 2-6h; the secondary sintering temperature is 600-900 ° C and the time is 5-10h.
  • a Na 3 V 2 (PO 4 ) 3 / C sodium ion battery cathode material is provided.
  • the Na 3 V 2 (PO 4 ) 3 / C sodium ion battery cathode material is prepared by the method for preparing the sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C according to the present invention.
  • a positive electrode sheet for a sodium ion battery is provided.
  • the sodium ion battery positive electrode sheet is formed by cutting the Na 3 V 2 (PO 4 ) 3 / C sodium ion positive electrode material of the present invention.
  • a sodium ion battery in another aspect of the present invention, includes the positive electrode sheet.
  • the preparation method of the Na 3 V 2 (PO 4 ) 3 / C cathode material is that on the one hand, the electrospinning technology is used to form the film, which avoids the tedious milling process;
  • the conductive agent and the positive electrode material are integrated and sintered without using a binder and a current collector, which simplifies the process and avoids the decrease in electrical performance caused by the use of a binder.
  • the sodium ion battery cathode material is a Na 3 V 2 (PO 4 ) 3 / C fiber membrane prepared by electrostatic spinning technology. Through special heat treatment and pre-oxidation and sintering processes, a free-standing electrode material can be prepared, avoiding the use of auxiliary materials. Additives (such as a binder) and a current collector make the ion of the positive electrode material of the sodium ion battery have a fast transport speed of electrons, small internal resistance, small polarization, and high energy density.
  • the positive electrode sheet of the sodium ion battery contains the positive electrode material of the sodium ion battery, the ions of the positive electrode sheet of the sodium ion battery have a fast transport speed of electrons, small internal resistance, small polarization effect, and high energy density.
  • the sodium ion battery contains the positive electrode sheet, and due to the ions of the positive electrode sheet, the electrons are transported fast, the internal resistance is small, the polarization effect is small, and the energy density is large, which makes the battery have high specific capacity and good rate performance. Good cycling performance.
  • FIG. 1 is an X-ray diffraction pattern of a Na 3 V 2 (PO 4 ) 3 / C material in an example of the present invention
  • FIG. 2 is a SEM spectrum of a Na 3 V 2 (PO 4 ) 3 / C material in an example of the present invention
  • FIG. 3 is a TEM spectrum of a Na 3 V 2 (PO 4 ) 3 / C material in an example of the present invention
  • FIG. 4 is the first three charge and discharge curves and cycle performance patterns of the electrode material in the embodiment of the present invention.
  • FIG. 5 is a result of a rate performance test of an electrode material in an embodiment of the present invention
  • a binder-free Na 3 V 2 (PO 4 ) 3 / C fiber cathode material is prepared through an electrostatic spinning technology.
  • the obtained cathode material has the advantages of high specific capacity and good rate performance.
  • the specific nanofiber electrode material with the above general formula Na 3 V 2 (PO 4 ) 3 / C is formed by sintering and forming the raw materials of Na 3 V 2 (PO 4 ) 3 and the source of the conductive agent, avoiding the use of adhesive Therefore, the energy density is higher.
  • the specific method for preparing sodium ion cathode material Na 3 V 2 (PO 4 ) 3 includes the following steps:
  • Step (1) disposing a component including a vanadium source, a complexing agent, a sodium source, a phosphoric acid source compound, and a viscous agent in water to form a spinning solution;
  • Step (2) Electrospinning the prepared spinning solution to obtain a fiber membrane precursor.
  • Step (3) The fiber membrane precursor is heat-pressed, and then the fiber membrane precursor is pre-oxidized in an environment containing oxygen.
  • Step (4) sintering the pre-oxidized fiber membrane precursor to obtain Na 3 V 2 (PO 4 ) 3 / C nanofiber cathode material.
  • the vanadium source, sodium source, and phosphoric acid source described in the above step (1) are added according to the stoichiometry of the elements in the chemical formula Na 3 V 2 (PO 4 ) 3 , such as the molar ratio, that is, the The molar ratio of V, Na, and P elements is 2: 3: 3, which can fluctuate within the range allowed by the error.
  • the vanadium source includes one or more of vanadium pentoxide, ammonium metavanadate, sodium orthovanadate, and sodium metavanadate; if the reaction effect and raw material availability are not considered, Other vanadium sources commonly used in the industry can be used;
  • the sodium salt includes one of sodium dihydrogen phosphate, sodium phosphate, sodium carbonate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, sodium citrate Or several types;
  • the phosphoric acid source includes one or more of sodium dihydrogen phosphate, sodium phosphate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and triammonium phosphate.
  • the complexing agent includes one or more of anhydrous oxalic acid, citric acid, ascorbic acid, maleic acid, tartaric acid, oxalic acid, malic acid, and lactic acid.
  • the carboxyl group is selected here as the complexing group. If the complexing ability is not considered, other complexing agents in the field can be used.
  • the complexing agent is combined with a high-priced example. In this embodiment, it is pentavalent vanadium. Ions, so that the interference of high-valent ions is shielded, eliminating the adverse effects of high-valent ions on the electrostatic spinning process.
  • the molar ratio of the vanadium source to the complexing agent is controlled to be 1: 1 to 1: 2.
  • An equal or excessive amount of complexing agent can sufficiently eliminate the adverse effects of vanadium ions on the electrospinning process.
  • the mass ratio of the viscous agent and the vanadium source is controlled to meet the viscosity requirements of the spinning solution.
  • the fibers in the fiber film in the step (2) are nano-scale fibers, which can be achieved by adjusting the process conditions of electrostatic spinning.
  • the obtained nanofiber sufficient membrane material has excellent electrochemical performance.
  • the selection conditions are: the voltage selection is 15KV-30KV; the distance between the receiver and the needle is 10cm-20cm; the spinning rate is 0.1ml / h-0.6ml / h; the drum speed is 500r / min-1000r / min; the needle model is 18 -25 (unit).
  • the hot-pressing treatment in the step (3) has two effects, removing most of the water in the fiber film while compacting the fiber film.
  • the oxygen-containing environment in the pre-oxidation process may be air or other oxygen-containing environments.
  • the hot-pressing process is a hot-pressing process at a temperature of 2-6 Kg at 100 ° C for 10-20 hours; the pre-oxidation process is a process in which the fiber membrane precursor after the hot-pressing process is heated at 2 ° C in the air. / min heating rate to (range) 260 °C for 3h for treatment.
  • the protective atmosphere for the sintering process in the step (4) may be a nitrogen environment, an argon environment, a vacuum, or another inert gas environment.
  • the sintering is performed under a protective atmosphere, accompanied by organic carbonization, and there is a secondary sintering.
  • the initial sintering temperature is 300-400 ° C and the time is 2-6h; the secondary sintering temperature is 600-900 ° C and the time is 5-10h.
  • the preparation method avoids the traditional powder making process, and the electrode sheet is integrally sintered, it also avoids the use of additives, while ensuring performance, greatly simplifying the process and reducing costs.
  • an embodiment of the present invention also provides a Na 3 V 2 (PO 4 ) 3 / C sodium ion battery cathode material.
  • the nanometer scale of the fiber membrane makes the electrode material have strong ion transport capacity, high specific capacity, and good rate ratio.
  • the use of an adhesive can further increase energy density, reduce internal resistance, and reduce polarization.
  • an embodiment of the present invention also provides a positive electrode sheet for a sodium ion battery.
  • the traditional process of the positive electrode sheet includes metal salts, adhesives, and conductive agents. Since the sodium ion positive electrode sheet is integrally sintered and formed, it can be composed only of the sodium ion positive electrode material Na 3 V 2 (PO 4 ) 3 / C. The structure is greatly simplified, and the polarization and the polarization are reduced. The internal resistance is optimized and the electrical performance is optimized.
  • an embodiment of the present invention also provides a sodium ion battery.
  • the structure of the positive electrode of the sodium ion battery may be a conventional sodium ion battery, or may be an improvement based on the conventional sodium ion battery.
  • the sodium ion battery includes a positive electrode, a separator, and a negative electrode, and the positive electrode, the separator, and the negative electrode are sequentially stacked and wound to form a battery cell; and the cell is installed in a battery case. The electrolyte is filled in the battery case.
  • the positive electrode sheet is the positive electrode sheet of the sodium ion battery described above.
  • This embodiment provides a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C.
  • the method for preparing the sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps:
  • (1) Spinning solution configuration Measure 25ml of deionized water in a beaker, add 3.5g of polyvinyl alcohol (PVA), and then stir at 70 ° C for 3h to stand for half an hour to form a polyvinyl alcohol aqueous solution. Then weigh 0.4680 g ammonium metavanadate, 0.7202 g of anhydrous oxalic acid, 0.6902 g of ammonium dihydrogen phosphate, and 0.4920 g of sodium acetate are dissolved in 8 ml of deionized water. After the dissolution is complete, slowly add it to the polyvinyl alcohol aqueous solution and keep it at 70 ° C. And dripping under stirring conditions, then turn off the heating device to allow it to continue stirring at room temperature for 5h and let stand for 2h to form a uniform spinning solution;
  • PVA polyvinyl alcohol
  • Hot pressing treatment and pre-oxidation The spinning precursor in the collecting step (2) is dried at 100 ° C for 10h in a drying box under a pressure of 2-6Kg, and then the precursor fiber is heated at 2 ° C / min in air. Pre-oxidation by heating to 260 °C for 3h;
  • step (3) The fiber membrane pre-treated in step (3) is cut into a square with a side length of about 3 cm, and then the fiber membrane is sandwiched between two ceramic sheets having a thickness of 0.1 cm and a side length of 4 cm. It is put into a tube furnace for pre-sintering at 350 ° C in an Ar atmosphere for 5h, and then sintering in an Ar atmosphere at 700 ° C for 8h;
  • step (4) Preparation of positive electrode material: The fiber film sintered and cooled in step (4) is directly punched into a circular positive electrode sheet under a coin cell punching machine.
  • the Na 3 V 2 (PO 4 ) 3 / C electrode material of this embodiment as an example, its structure is determined by an X-ray diffractometer.
  • the X-ray diffraction pattern (XRD) shown in FIG. 1 shows that there are no hybrid peaks in the Na 3 V 2 (PO 4 ) 3 / C material, and all the diffraction peaks can be well matched with the R3C space group. It is pure.
  • the SEM shown in FIG. 2 and the TEM image in FIG. 3 show that the Na 3 V 2 (PO 4 ) 3 nanofiber network structure we prepared has a diameter of about 200nm and a uniform size.
  • the nanofibers are coated with a size About 50nm Na 3 V 2 (PO 4 ) 3 particles, nanofibers are intertwined to form a three-dimensional network structure, which has good structural stability.
  • This embodiment provides a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C.
  • the method for preparing sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps:
  • (1) Spinning solution configuration Measure 25ml of deionized water in a beaker, add 3.5g of polyvinyl alcohol (PVA), and then stir at 70 ° C for 3h to stand for half an hour to form a polyvinyl alcohol aqueous solution. Then weigh 0.4680 g ammonium metavanadate, 0.7202 g of anhydrous oxalic acid, 0.6902 g of ammonium dihydrogen phosphate, and 0.3180 g of sodium carbonate are dissolved in 8 ml of deionized water. After the dissolution is complete, slowly add it to the polyvinyl alcohol aqueous solution and keep it at 70 ° C. And dripping under stirring conditions, then turn off the heating device to allow it to continue stirring at room temperature for 5h and let stand for 2h to form a uniform spinning solution;
  • PVA polyvinyl alcohol
  • Electrospinning Put the spinning solution configured in step (1) into a 30ml syringe.
  • the syringe is connected to the positive pole of the power supply, and the drum receiver is connected to the negative pole of the power supply.
  • the syringe and the receiver are at the same level and the receiving distance. It is 15cm, the voltage is 20KV, the needle model is No. 21, the syringe advance rate is 0.4ml / h, the drum rotation speed is 800r / min, and the fiber membrane is obtained by spinning for 20h;
  • Hot pressing treatment and pre-oxidation The spinning precursor in the collecting step (2) is dried at 100 ° C for 10h in a drying box under a pressure of 2-6Kg, and then the precursor fiber is heated at 2 ° C / min in air. Pre-oxidation by heating to 260 °C for 3h;
  • step (3) The fiber membrane pre-treated in step (3) is cut into a square with a side length of about 3 cm, and then the fiber membrane is sandwiched between two ceramic sheets having a thickness of 0.1 cm and a side length of 4 cm. It is put into a tube furnace for pre-sintering at 350 ° C in an Ar atmosphere for 5h, and then sintering in an Ar atmosphere at 700 ° C for 8h;
  • step (4) Preparation of positive electrode material: The fiber film sintered and cooled in step (4) is directly punched into a circular positive electrode sheet under a coin cell punching machine.
  • This embodiment provides a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C.
  • the method for preparing sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps:
  • Spinning solution configuration Measure 25ml of deionized water in a beaker, add 3.5g of polyvinyl alcohol (PVA), and then stir at 70 ° C for 3h to stand for half an hour to form a polyvinyl alcohol aqueous solution. Then weigh 0.4680 g ammonium metavanadate, 0.7202 g of anhydrous oxalic acid, 0.7199 g of sodium dihydrogen phosphate are dissolved in 8 ml of deionized water, and after the solution is completely dissolved, it is slowly added to the aqueous solution of polyvinyl alcohol and kept at 70 ° C under stirring. Then, turn off the heating device and let it continue to stir at room temperature for 5h and let stand for 2h to form a uniform spinning solution.
  • PVA polyvinyl alcohol
  • Electrospinning Put the spinning solution configured in step (1) into a 30ml syringe.
  • the syringe is connected to the positive pole of the power supply, and the drum receiver is connected to the negative pole of the power supply.
  • the syringe and the receiver are at the same level and the receiving distance. It is 15cm, the voltage is 20KV, the needle model is No. 21, the syringe advance rate is 0.4ml / h, the drum rotation speed is 800r / min, and the fiber membrane is obtained by spinning for 20h.
  • Hot pressing treatment and pre-oxidation The spinning precursor in the collecting step (2) is dried at 100 ° C for 10h in a drying box under a pressure of 2-6Kg, and then the precursor fiber is heated at 2 ° C / min in air. The rate was heated to 260 ° C for 3h to perform pre-oxidation.
  • step (3) The fiber membrane pre-treated in step (3) is cut into a square with a side length of about 3 cm, and then the fiber membrane is sandwiched between two ceramic sheets having a thickness of 0.1 cm and a side length of 4 cm. It was put into a tube furnace for pre-sintering at 350 ° C. for 5 h in an Ar atmosphere, and then sintered at 700 ° C. for 8 h.
  • step (4) Preparation of positive electrode material: The fiber film sintered and cooled in step (4) is directly punched into a circular positive electrode sheet under a coin cell punching machine.
  • This embodiment provides a sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C.
  • the method for preparing sodium ion cathode material Na 3 V 2 (PO 4 ) 3 / C includes the following steps:
  • Spinning solution configuration Measure 25ml of deionized water in a beaker, add 3.5g of polyvinyl alcohol (PVA), and then stir at 70 ° C for 3h to stand for half an hour to form a polyvinyl alcohol aqueous solution. Then weigh 0.4680 g ammonium metavanadate, 0.7202 g of anhydrous oxalic acid, 0.7199 g of sodium dihydrogen phosphate are dissolved in 8 ml of deionized water, and after the solution is completely dissolved, it is slowly added to the aqueous solution of polyvinyl alcohol and kept at 70 ° C under stirring. Then, turn off the heating device and let it continue to stir at room temperature for 5h and let stand for 2h to form a uniform spinning solution.
  • PVA polyvinyl alcohol
  • Electrospinning Put the spinning solution configured in step (1) into a 30ml syringe.
  • the syringe is connected to the positive pole of the power supply, and the drum receiver is connected to the negative pole of the power supply.
  • the syringe and the receiver are at the same level and the receiving distance. It is 15cm, the voltage is 20KV, the needle model is No. 21, the syringe advance rate is 0.6ml / h, the drum rotation speed is 800r / min, and the fiber membrane is obtained by spinning for 20h.
  • Hot pressing treatment and pre-oxidation The spinning precursor in the collecting step (2) is dried at 100 ° C for 10h in a drying box under a pressure of 2-6Kg, and then the precursor fiber is heated at 2 ° C / min in air. The rate was heated to 260 ° C for 3h to perform pre-oxidation.
  • step (3) The fiber membrane pre-treated in step (3) is cut into a square with a side length of about 3 cm, and then the fiber membrane is sandwiched between two ceramic sheets having a thickness of 0.1 cm and a side length of 4 cm. It was put into a tube furnace for pre-sintering at 350 ° C. for 5 h in an Ar atmosphere, and then sintered at 700 ° C. for 8 h.
  • step (4) Preparation of positive electrode material: The fiber film sintered and cooled in step (4) is directly punched into a circular positive electrode sheet under a coin cell punching machine.
  • the positive electrode material Na 3 V 2 (PO 4 ) 3 / C fiber membranes prepared in Examples 1-4 were directly made into positive electrode sheets, with sodium sheet as negative electrode, Celgard 2400 glass fiber as separator, and 1 mol / L electrolyte solution.
  • the propylene carbonate solution of NaClO4 and 2% by volume (calculated as propylene carbonate) of fluoroethylene carbonate (FEC) was allowed to stand for 12 hours and tested on a LAND CT2001A tester.
  • FIG. 4 is the first three charge-discharge curves and cycle performance patterns of the sample in Example 1.
  • the voltage of 2.8-4.0V and the rate of 0.1C there is only one voltage platform, which is about 3.4V.
  • Its first discharge specific capacity is 107mAh / g; the first charge and discharge efficiency is 92%, and the capacity has almost no attenuation after 100 cycles, showing good cycle performance.
  • Example 1 The test results of the rate performance of the electrode material in Example 1 are shown in FIG. 5. This material shows excellent rate performance, and at a high rate of 30C, it can still emit a specific capacity of 30mAh / g.

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Abstract

公开了一种柔性的无粘结剂钠离子电池Na 3V 2(PO 4) 3/C复合电极的制备方法。水为溶剂，加以增稠剂来调节溶液黏度，然后加入钒源、络合剂、钠源、磷酸源化合物制备成纺丝液，通过静电纺丝技术得到纺前体，然后将收集的纺前体进行热压处理和预氧化处理，然后在惰性气体中进行烧结得到Na 3V 2(PO 4) 3/C纤维膜，所得的纤维大小均匀，直径小，比表面大，可以直接剪裁成圆形电极片，用于钠离子电池中表现出较高的充放电比容量和良好循坏稳定性，并且该制备方法工艺简单，反应条件参数易于控制，有利于实现大规模生产。

Description

钠离子电池正极材料及其制备方法和应用 技术领域
本发明属于纳米材料与电化学领域，具体涉及一种钠离子电池正极材料Na 3V 2(PO 4) 3/C的制备方法。
背景技术
从便携式电子设备到时下引人注目的电动汽车，锂离子电池作为高能量密度的储能器件得到了广泛的应用。虽然现在锂离子电池在消费市场中占有主导地位，但是由于锂的地壳储量少(0.002％左右)且分布不均匀，使得锂离子电池在未来将会面临资源和价格的双重瓶颈。钠元素丰富，价格低廉，且与锂具有相似的化学性能，钠离子电池应用于储能领域具有可持续利用和商业化的优势和巨大潜力。
具备钠超离子导体(NASICON)结构的Na 3V 2(PO 4) 3 ，由于其钠离子三维扩散，相对较高的电压平台(3.4V)，高理论比能量(400Whkg -1)，以及优秀的热稳定性能让Na 3V 2(PO 4) 3成为目前最有前景的钠离子正极材料之一。传统技术主要基于高温固相法，溶胶-凝胶法、水热法制备Na 3V 2(PO 4) 3/C，这些工艺都有如下优缺点：
（1）高温固相法
高温固相法是一种传统的制粉工艺，虽然有其固有的缺点，如能耗大、效率低、粉体不够细、易混入杂质等。但该法具有制备的粉体颗粒无团聚、填充性好、成本低、产量大、制备工艺简单等优点。
（2）溶胶-凝胶法
由于溶胶－凝胶法中所用的原料首先被分散到溶剂中而形成低粘度的溶液，因此，就可以在很短的时间内获得分子水平的均匀性，在形成凝胶时，反应物之间很可能是在分子水平上被均匀地混合。由于经过溶液反应步骤，那么就很容易均匀定量地掺入一些微量元素，实现分子水平上的均匀掺杂。
与固相反应相比，化学反应将容易进行，而且仅需要较低的合成温度，一般认为溶胶一凝胶体系中组分的扩散在纳米范围内，而固相反应时组分扩散是在微米范围内，因此反应容易进行，温度较低。缺点是所使用的原料价格比较昂贵，有些原料为有机物，对健康有害；通常整个溶胶-凝胶过程所需时间较长，常需要几天或几周；凝胶中存在大量微孔，在干燥过程中又将会逸出许多气体及有机物，并产生收缩。
（3）水热法
其最大优点是一般不需高温烧结即可直接得到结晶粉末，避免了可能形成微粒硬团聚，也省去了研磨及由此带来的杂质。水热过程中通过调节反应条件可控制纳米微粒的晶体结构、结晶形态与晶粒纯度。既可以制备单组分微小单晶体，又可制备双组分或多组分的特殊化合物粉末。可制备金属、氧化物和复合氧化物等粉体材料。所得粉体材料的粒度范围通常为0.1μm至几微米，有些可以达到几十纳米。所得到的粉末纯度高、分散性好、均匀、分布窄、无团聚、晶型好、形状可控、利于环境净化等。缺点是：水热法需要高温高压步骤，使其对生产设备的依赖性比较强，同时也大大增加了经济成本，和时间成本。
总得来说，传统工艺，全都是采用先制成Na 3V 2(PO 4) 3/C粉材，然后将其与粘接剂制成浆料，涂覆成膜。导致现有Na 3V 2(PO 4) 3/C粉材应用工序复杂，成本高，而且由于其颗粒结构且粘结剂的存在，导致电极有如内阻大，比容量低，倍率性能弱，循环性能差等缺陷。
技术问题
本发明的目的是提供一种钠离子电池正极材料Na 3V 2(PO 4) 3/C及其制备方法，以解决传统制备方法工艺复杂导致的成本偏高，或制备的Na 3V 2(PO 4) 3/C颗粒不稳定的技术问题。
本发明的另一目的在于提供一种含有该正极材料的钠离子电池正极片以及钠离子电池以解决现有的钠离子电池正极片以及电池的电化学性能不理想的问题。
 技术解决方案
为了实现上述发明目的，本发明的一方面，提供了一种钠离子正极材料Na 3V 2(PO 4) 3/C的制备方法。所述制备方法包括以下步骤一种钠离子正极材料Na 3V 2(PO 4) 3/C的制备方法，包括以下步骤：
将包括钒源、络合剂、钠源、磷酸源化合物和粘稠剂的组分于水中配置成纺丝液；
将所述纺丝液进行静电纺丝处理，得到纤维膜前驱体；
将所述制备的纤维膜前驱体进行热压处理，然后在含氧气的环境中于进行预氧化处理；
将经所述预氧化处理后的纤维膜前驱体经过烧结处理，制备得到Na 3V 2(PO 4) 3/C纳米纤维膜。
优选的，所述纺丝液的配制方法为：将钒源、络合剂、钠源、磷酸源化合物溶解于水中，形成溶液，再加入到聚乙烯醇的水溶液中，混合处理后静置得到纺丝液。
优选的，所述钒源包括五氧化二钒、偏钒酸铵、正钒酸钠、偏钒酸钠中的一种或几种；
优选的，所述粘稠剂包括聚乙烯醇、聚乙烯吡咯烷酮、聚丙烯腈、聚苯乙烯、聚氨酯、聚环氧乙烷中的一种或几种；
优选的，所述络合剂包括无水草酸、柠檬酸、抗坏血酸、马来酸、酒石酸、乙二酸、苹果酸、乳酸中的一种或几种；
优选的，所述钠源包括磷酸二氢钠、磷酸钠、碳酸钠、硝酸钠、草酸钠、醋酸钠、硫酸钠、氢氧化钠、甲酸钠、柠檬酸钠中的一种或几种；
优选的，所述磷酸源包括磷酸二氢钠、磷酸钠、磷酸、磷酸二氢铵、磷酸氢二铵、磷酸三铵中的一种或几种。
优选的，所述钒源与络合剂摩尔比为1：1-1:2。
优选的，所述粘稠剂与钒源的质量比为6:1-8:1。
优选的，所述静电纺丝处理的工艺条件为：电压选择为15KV-30KV；接收器与针头距离为10cm-20cm；纺丝速率为0.1ml/h-0.6ml/h；滚筒转速为500r/min-1000r/min；针头内径为0.4mm-0.8mm。
所述纤维膜中的纤维为纳米尺度的纤维。
优选的，所述热压处理工艺，是在2-6Kg的压力下于100℃-130℃下热压处理10-20h；
所述预氧化工艺是将所述热压处理后的纤维膜前驱体在空气中以1℃/min-5℃/min的升温速率加热到220℃-260℃保温2-5h进行处理。
优选的，所述烧结包含两次在保护氛围中的烧结，同时伴随着有机碳化作用，初始烧结温度为300-400℃，时间为2-6h；二次烧结温度为600-900℃，时间为5-10h。
本发明的另一方面，提供了一种Na 3V 2(PO 4) 3/C钠离子电池正极材料。所述Na 3V 2(PO 4) 3/C钠离子电池正极材料本发明是由本发明钠离子正极材料Na 3V 2(PO 4) 3/C的制备方法制备获得。
本发明的再一方面，提供了一种钠离子电池正极片。所述钠离子电池正极片是由本发明Na 3V 2(PO 4) 3/C钠离子正极材料经裁剪处理形成。
本发明的又一方面，提供了一种钠离子电池。所述钠离子电池包含所述正极片。
 有益效果
与现有技术相比，所述Na 3V 2(PO 4) 3/C正极材料的制备方法一方面是采用的静电纺丝技术处理成膜，避免了繁琐的制粉工艺；另一方面将导电剂和正极材料一体化烧结成型，无需使用粘接剂，集电器，简化了工艺的同时，还避免了使用粘接剂导致的电学性能下降。
所述钠离子电池正极材料是由静电纺丝技术制备的Na 3V 2(PO 4) 3/C纤维膜，通过特殊的热处理和预氧化以及烧结工艺可以制备出独立式电极材料，避免使用辅助添加剂（如粘结剂）和集电器，使得该钠离子电池的正极材料的离子，电子的运输速度快，内阻小，极化作用小，能量密度大。
所述钠离子电池的正极片由于含有所述钠离子电池正极材料，使得该钠离子电池的正极片的离子，电子的运输速度快，内阻小，极化作用小，能量密度大。
所述钠离子电池含有所述正极片，又由于该正极片的离子，电子的运输速度快，内阻小，极化作用小，能量密度大，使得该电池具有比容量高，倍率性能好，循环性能好等优点。
 附图说明
图1为本发明实施例中Na 3V 2(PO 4) 3/C材料的X射线衍射图谱
图2为本发明实施例中Na 3V 2(PO 4) 3/C材料的SEM图谱
图3为本发明实施例中Na 3V 2(PO 4) 3/C材料的TEM图谱
图4为本发明实施例中电极材料前三次充放电曲线及循环性能图案
图5为本发明实施例中电极材料的倍率性能测试结果
 本发明的实施方式
为了使本发明要解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明实施例通过静电纺丝技术制备了无粘结剂Na 3V 2(PO 4) 3/C纤维正极材料，所得正极材料具有比容量高，倍率性能好等优点。以下通过具体实施例和附图对本发明作进一步详述。
具体的上述通式为Na 3V 2(PO 4) 3/C的纳米纤维电极材料是形成Na 3V 2(PO 4) 3原料和导电剂源原位烧结成型，避免了使用粘接剂，因此能量密度更高。具体的钠离子正极材料Na 3V 2(PO 4) 3制备方法包括如下步骤：
步骤（1）将包括钒源、络合剂、钠源、磷酸源化合物和粘稠剂的组分于水中配置成纺丝液；
步骤(2) 将配置好的纺丝液进行静电纺丝处理得到纤维膜前驱体。
步骤(3) 将纤维膜前驱体进行热压处理，然后将纤维膜前驱体在含氧气的环境中进行预氧化处理。
步骤(4) 将所述经预氧化处理后的纤维膜前驱体经过烧结得到Na 3V 2(PO 4) 3/C纳米纤维正极材料。
具体的上述步骤（1）中所述钒源、钠源、磷酸源按照化学式Na 3V 2(PO 4) 3中的元素化学计量比如摩尔比添加，即钒源、钠源、磷酸源中的V、Na、P元素的摩尔比为2:3:3,可在误差允许的范围内波动。
在具体的实施例中，所述钒源包括五氧化二钒、偏钒酸铵、正钒酸钠、偏钒酸钠中的一种或几种；若不考虑反应效果和原料易得性也可使用行业内常用其他钒源；所述钠盐包括磷酸二氢钠、磷酸钠、碳酸钠、硝酸钠、草酸钠、醋酸钠、硫酸钠、氢氧化钠、甲酸钠、柠檬酸钠中的一种或几种；所述磷酸源包括磷酸二氢钠、磷酸钠、磷酸、磷酸二氢铵、磷酸氢二铵、磷酸三铵中的一种或几种。
所述络合剂包括无水草酸、柠檬酸、抗坏血酸、马来酸、酒石酸、乙二酸、苹果酸、乳酸中的一种或几种。此处选用的是羧基作为络合基团，若不考虑络合能力也可选用本领域其他络合剂；在纺丝过程中，络合剂与高价例子结合，本实施例中为五价钒离子，从而使得高价离子的干扰作用被屏蔽，消除了高价离子对静电纺丝过程的不利影响。
在一实施例中，控制所述钒源与络合剂摩尔比为1：1-1:2。等量或过量的络合剂可以充分消除钒离子对静电纺丝过程的不利影响。
在一实施例中，控制所述粘稠剂和钒源的质量比为……可以满足纺丝液的粘度要求。
所述步骤（2）中的纤维膜中的纤维为纳米尺度纤维，通过调整静电纺丝的工艺条件即可实现。所得纳米纤维够能的膜材料具有优良的电化学性能。选取条件为：电压选择为15KV-30KV；接收器与针头距离为10cm-20cm；纺丝速率为0.1ml/h-0.6ml/h；滚筒转速为500r/min-1000r/min；针头型号为18-25（单位）。
所述步骤（3）中所述热压处理有两个效果，在将纤维膜压实的同时将纤维膜中大部分的水分去掉。所述预氧化处理中的含氧气环境可以是空气也可以是其他含氧环境。所述热压处理工艺，是在2-6Kg的压力下于100℃下热压处理10-20h；所述预氧化工艺是将所述热压处理后的纤维膜前驱体在空气中以2℃/min的升温速率加热到（范围）260℃保温3h进行处理。
所述步骤（4）中所述烧结处理的保护氛围可以是氮气环境，氩气环境，真空，或者其他惰性气体环境。所述烧结是在保护氛围下进行，伴随着有机碳化作用，并且存在二次烧结。初始烧结温度为300-400℃，时间为2-6h；二次烧结温度为600-900℃，时间为5-10h。
所述制备方法由于避免了传统的制粉工艺的流程，同时电极片一体烧结成型还避免了使用添加剂，在保证性能的同时，大大的简化工艺的降低了成本。
基于上文钠离子正极材料Na 3V 2(PO 4) 3/C的制备方法的基础上，本发明实施例还提供了一种Na 3V 2(PO 4) 3/C钠离子电池正极材料。纤维膜的纳米尺度使得该电极材料离子运输能力强，比容量高，倍率性好，同时不使用粘接剂能进一步增加能量密度减小内阻，降低极化。
一方面，本发明实施例还提供了一种钠离子电池正极片。传统工艺的正极片包括，金属盐，粘接剂，导电剂。而所述钠离子正极片由于是一体化烧结成型，只由钠离子正极材料Na 3V 2(PO 4) 3/C本身就可以构成，结构大大简化的同时，还减小了极化，降低了内阻，优化了电学性能。
同时，本发明实施例还提供了一种钠离子电池。所述钠离子电池正极的结构可以是常规的钠离子电池，也可以是依据常规钠离子电池进行的改进。一实施例中，所述钠离子电池包括正极、隔膜、负极，且所述正极、隔膜、负极依次层叠，并进行卷绕，制成电池电芯；且所述电芯装设于电池壳体内，电解液填充于电池壳体内。不管所述钠离子电池为何种结构，其正极片为上文所述钠离子电池正极片。
实施例1
本实施例提供了一种钠离子正极材料Na 3V 2(PO 4) 3/C。所述钠离子正极材料Na 3V 2(PO 4) 3/C制备方法包括如下步骤：
（1）纺丝液的配置：量取25ml去离子水于烧杯中，加入3.5g聚乙烯醇（PVA），然后在70℃搅拌3h后静置半小时形成聚乙烯醇水溶液，再称取0.4680g偏钒酸铵、0.7202g无水草酸、0.6902g磷酸二氢铵、0.4920g乙酸钠溶于8ml去离子水中，溶解完全后再将其缓慢滴加到聚乙烯醇水溶液中，保持在70℃及搅拌条件下滴加，之后关闭加热装置让其在室温下持续搅拌5h并静置2h形成均一的纺丝液；
（2）静电纺丝:将步骤（1）中配置好的纺丝液装入到30ml的注射器中，注射器接电源正极，滚筒接收器接电源负极，注射器与接收器处于同一水平高度，接受距离为15cm，电压为20KV，针头型号为21号，注射器推进速率为0.4ml/h，滚筒转速为800r/min，纺丝20h得到纤维膜；
（3）热压处理和预氧化：收集步骤（2）中的纺前体在2-6Kg的压力下于干燥箱中100℃干燥10h，然后将前驱体纤维在空气中以2℃/min升温速率加热到260℃保温3h进行预氧化；
（4）烧结:将步骤（3）中预处理后的纤维膜剪裁成边长为3cm左右的正方形，然后将纤维膜夹在两层厚度为0.1cm，边长4cm的陶瓷片之间，将其放入管式炉中在Ar气氛中350℃预烧结5h，然后在700℃下Ar气氛中烧结8h；
（5）正极材料制备：将步骤（4）中烧结冷却后的纤维膜直接在纽扣电池冲片机下冲裁成圆形的正极片。
以本实施例产物Na 3V 2(PO 4) 3/C电极材料为例，其结构由X射线衍射仪确定。附图1所示X射线衍射图谱(XRD)表明Na 3V 2(PO 4) 3/C材料中不存在杂峰，所有的衍射峰都能很好的与R3C空间群匹配，制备得到的材料是纯相的。
附图2所示的SEM和附图3中的TEM图像表明我们所制备的Na 3V 2(PO 4) 3纳米纤维网络结构，纳米纤维直径200nm左右，大小均一，纳米纤维中包覆着大小约50nm的Na 3V 2(PO 4) 3颗粒，纳米纤维相互交错形成三维网络状结构，具有很好的结构稳定性。
实施例2
本实施例提供了一种钠离子正极材料Na 3V 2(PO 4) 3/C。所述钠离子正极材料Na 3V 2(PO 4) 3/C制备方法包括如下步骤：
（1）纺丝液的配置：量取25ml去离子水于烧杯中，加入3.5g聚乙烯醇（PVA），然后在70℃搅拌3h后静置半小时形成聚乙烯醇水溶液，再称取0.4680g偏钒酸铵、0.7202g无水草酸、0.6902g磷酸二氢铵、0.3180g碳酸钠溶于8ml去离子水中，溶解完全后再将其缓慢滴加到聚乙烯醇水溶液中，保持在70℃及搅拌条件下滴加，之后关闭加热装置让其在室温下持续搅拌5h并静置2h形成均一的纺丝液；
（2）静电纺丝:将步骤（1）中配置好的纺丝液装入到30ml的注射器中，注射器接电源正极，滚筒接收器接电源负极，注射器与接收器处于同一水平高度，接受距离为15cm，电压为20KV，针头型号为21号，注射器推进速率为0.4ml/h，滚筒转速为800r/min，纺丝20h得到纤维膜；
（3）热压处理和预氧化：收集步骤（2）中的纺前体在2-6Kg的压力下于干燥箱中100℃干燥10h，然后将前驱体纤维在空气中以2℃/min升温速率加热到260℃保温3h进行预氧化；
（4）烧结:将步骤（3）中预处理后的纤维膜剪裁成边长为3cm左右的正方形，然后将纤维膜夹在两层厚度为0.1cm，边长4cm的陶瓷片之间，将其放入管式炉中在Ar气氛中350℃预烧结5h，然后在700℃下Ar气氛中烧结8h；
（5）正极材料制备：将步骤（4）中烧结冷却后的纤维膜直接在纽扣电池冲片机下冲裁成圆形的正极片。
实施例3
本实施例提供了一种钠离子正极材料Na 3V 2(PO 4) 3/C。所述钠离子正极材料Na 3V 2(PO 4) 3/C制备方法包括如下步骤：
（1）纺丝液的配置：量取25ml去离子水于烧杯中，加入3.5g聚乙烯醇（PVA），然后在70℃搅拌3h后静置半小时形成聚乙烯醇水溶液，再称取0.4680g偏钒酸铵、0.7202g无水草酸、0.7199g磷酸二氢钠溶于8ml去离子水中，溶解完全后再将其缓慢滴加到聚乙烯醇水溶液中，保持在70℃及搅拌条件下滴加，之后关闭加热装置让其在室温下持续搅拌5h并静置2h形成均一的纺丝液。
（2）静电纺丝:将步骤（1）中配置好的纺丝液装入到30ml的注射器中，注射器接电源正极，滚筒接收器接电源负极，注射器与接收器处于同一水平高度，接受距离为15cm，电压为20KV，针头型号为21号，注射器推进速率为0.4ml/h，滚筒转速为800r/min，纺丝20h得到纤维膜。
（3）热压处理和预氧化：收集步骤（2）中的纺前体在2-6Kg的压力下于干燥箱中100℃干燥10h，然后将前驱体纤维在空气中以2℃/min升温速率加热到260℃保温3h进行预氧化。
（4）烧结:将步骤（3）中预处理后的纤维膜剪裁成边长为3cm左右的正方形，然后将纤维膜夹在两层厚度为0.1cm，边长4cm的陶瓷片之间，将其放入管式炉中在Ar气氛中350℃预烧结5h，然后在700℃下Ar气氛中烧结8h。
（5）正极材料制备：将步骤（4）中烧结冷却后的纤维膜直接在纽扣电池冲片机下冲裁成圆形的正极片。
实施例4
本实施例提供了一种钠离子正极材料Na 3V 2(PO 4) 3/C。所述钠离子正极材料Na 3V 2(PO 4) 3/C制备方法包括如下步骤：
（1）纺丝液的配置：量取25ml去离子水于烧杯中，加入3.5g聚乙烯醇（PVA），然后在70℃搅拌3h后静置半小时形成聚乙烯醇水溶液，再称取0.4680g偏钒酸铵、0.7202g无水草酸、0.7199g磷酸二氢钠溶于8ml去离子水中，溶解完全后再将其缓慢滴加到聚乙烯醇水溶液中，保持在70℃及搅拌条件下滴加，之后关闭加热装置让其在室温下持续搅拌5h并静置2h形成均一的纺丝液。
（2）静电纺丝:将步骤（1）中配置好的纺丝液装入到30ml的注射器中，注射器接电源正极，滚筒接收器接电源负极，注射器与接收器处于同一水平高度，接受距离为15cm，电压为20KV，针头型号为21号，注射器推进速率为0.6ml/h，滚筒转速为800r/min，纺丝20h得到纤维膜。
（3）热压处理和预氧化：收集步骤（2）中的纺前体在2-6Kg的压力下于干燥箱中100℃干燥10h，然后将前驱体纤维在空气中以2℃/min升温速率加热到260℃保温3h进行预氧化。
（4）烧结:将步骤（3）中预处理后的纤维膜剪裁成边长为3cm左右的正方形，然后将纤维膜夹在两层厚度为0.1cm，边长4cm的陶瓷片之间，将其放入管式炉中在Ar气氛中350℃预烧结5h，然后在700℃下Ar气氛中烧结8h。
（5）正极材料制备：将步骤（4）中烧结冷却后的纤维膜直接在纽扣电池冲片机下冲裁成圆形的正极片。
分别将实施例1-4中制备出的正极材料Na 3V 2(PO 4) 3/C纤维膜直接制成正极片，以钠片为负极，Celgard2400玻璃纤维做隔膜，电解液用1mol/L的NaClO4和2体积％(以碳酸丙烯酯计)的氟代碳酸乙烯酯(FEC)的碳酸丙烯酯溶液，静置12h后在LAND CT2001A测试仪上进行测试。
其中，图4为实施例1中样品的前三次充放电曲线及循环性能图案，由图可知，在 2.8-4.0V的电压和0.1C的倍率下，只存在一个电压平台，在3.4V左右。其首次放电比容量为 107mAh/g；首次充放电效率为92%，100次循环后容量几乎无衰减，显示出了良好的循环性能。
实施例1中电极材料的倍率性能测试结果如图5所示。该材料显示优异的倍率性能，在高倍率30C情况下，仍可以放出30mAh/g的比容量。
经测试，其他实施例提供的正极材料相关电化学性能与实施例1相似。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种钠离子正极材料Na 3V 2(PO 4) 3/C的制备方法，其特征在于：包括以下步骤：
    将包括钒源、络合剂、钠源、磷酸源化合物和粘稠剂的组分溶解于水中配置成纺丝液；
    将所述纺丝液进行静电纺丝处理，得到纤维膜前驱体；
    将所述制备的纤维膜前驱体进行热压处理，然后在含氧气的环境中于进行预氧化处理；
    将经所述预氧化处理后的纤维膜前驱体经过烧结处理，制备得到Na 3V 2(PO 4) 3/C纤维膜。
  2. 如权利要求1所述的制备方法，其特征在于：所述纺丝液的配制方法为：将包括钒源、络合剂、钠源、磷酸源化合物组分溶解于水中，形成溶液，再加入到粘稠剂的水溶液中，混合处理后静置得到纺丝液。
  3. 如权利要求1所述的制备方法，其特征在于：所述钒源包括五氧化二钒、偏钒酸铵、正钒酸钠、偏钒酸钠中的一种或几种；和/或
    所述粘稠剂包括聚乙烯醇、聚乙烯吡咯烷酮、聚丙烯腈、聚苯乙烯、聚氨酯、聚环氧乙烷中的一种或几种；和/或
    所述络合剂包括无水草酸、柠檬酸、抗坏血酸、马来酸、酒石酸、乙二酸、苹果酸、乳酸中的一种或几种；和/或
    所述钠源包括磷酸二氢钠、磷酸钠、碳酸钠、硝酸钠、草酸钠、醋酸钠、硫酸钠、氢氧化钠、甲酸钠、柠檬酸钠中的一种或几种；和/或
    所述磷酸源包括磷酸二氢钠、磷酸钠、磷酸、磷酸二氢铵、磷酸氢二铵、磷酸三铵中的一种或几种。
  4. 如权利要求1所述的制备方法，其特征在于：所述钒源与络合剂摩尔比为1：1-1:2。和/或
    所述粘稠剂与钒源的质量比为6：1-8：1。和/或
  5. 如权利要求1所述的制备方法，其特征在于：所述静电纺丝处理的工艺条件为：电压选择为15KV-30KV；接收器与针头距离为10cm-20cm；纺丝速率为0.1ml/h-0.6ml/h；滚筒转速为500r/min-1000r/min；针头内径为0.4mm-0.8mm；和/或
    所述纤维膜中的纤维为纳米尺度的纤维。
  6. 如权利要求1所述的制备方法，其特征在于：所述热压处理工艺，是在2-6Kg的压力下于100℃-130℃下热压处理10-20h；
    所述预氧化工艺是将所述热压处理后的纤维膜前驱体在空气中以1℃/min-5℃/min的升温速率加热到220℃-260℃保温2-5h进行处理。
  7. 如权利要求1所述的制备方法，其特征在于：所述烧结包含两次在保护氛围中的烧结，同时伴随着有机碳化作用，初始烧结温度为300-400℃，时间为2-6h；二次烧结温度为600-900℃，时间为5-10h。
  8. 一种Na 3V 2(PO 4) 3/C钠离子电池正极材料，其特征在于：所述Na 3V 2(PO 4) 3/C钠离子电池正极材料由权利要求1-7任一所述的制备方法制备获得。
  9. 一种钠离子电池正极片，其特征在于：所述钠离子电池正极片是由权利要求8所述的Na 3V 2(PO 4) 3/C钠离子正极材料经裁剪处理形成。
  10. 一种钠离子电池，其特征在于包含所述正极片，所述正极片为权利要求9 所述的钠离子电池正极片。
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