CN-116314616-B - High-voltage Na3V2(PO4)2F3Flexible self-supporting anode at @ C, and preparation method and application thereof

Abstract

The invention relates to the technical field of flexible electrodes. The invention discloses a high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode and a preparation method and application thereof. The high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode is prepared from Na 3 V 2 (PO 4 ) 2 F 3 powder, polyacrylonitrile and an N, N-dimethylformamide solvent by preparing a flexible fiber film containing Na 3 V 2 (PO 4 ) 2 F 3 from a mixture of Na 3 V 2 (PO 4 ) 2 F 3 powder, polyacrylonitrile and the N, N-dimethylformamide solvent in an electrostatic spinning mode, and drying and calcining the flexible fiber film to obtain the Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode. The flexible self-supporting anode has a high-voltage platform and meets the requirements of the flexible sodium ion battery on electrochemical performance and mechanical performance.

Inventors

• LIU LIYING
• LIANG MIN
• SHI ZHICONG

Assignees

• 广东工业大学

Dates

Publication Date

20260508

Application Date

20230228

Claims (6)

1. 1. The preparation method of the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode is characterized by comprising the following steps of: (1) Preparing VPO 4 powder by adopting a sol-gel method; (2) Mixing VPO 4 powder and NaF, and preparing Na 3 V 2 (PO 4 ) 2 F 3 powder by a solid phase method; (3) Adding polyacrylonitrile into N, N-dimethylformamide solvent to form polymer solution, and dispersing Na 3 V 2 (PO 4 ) 2 F 3 powder into the polymer solution to obtain spinning solution; (4) Carrying out electrostatic spinning on the spinning solution to obtain a flexible fiber membrane containing Na 3 V 2 (PO 4 ) 2 F 3 ; (5) Sequentially carrying out vacuum drying and calcination treatment on the flexible fiber membrane to obtain the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode; in the step (2), the method for preparing Na 3 V 2 (PO 4 ) 2 F 3 powder by adopting a solid phase method comprises the following steps: Mixing and grinding VPO 4 and NaF with a molar ratio of 2 (3-3.15) for 5-20 min, pressing into tablets, and calcining at 600-700 ℃ for 1-6 h under inert atmosphere to obtain Na 3 V 2 (PO 4 ) 2 F 3 powder; In the step (5), after the flexible fiber membrane is dried for 3-11 hours at 90-120 ℃ in vacuum, the flexible fiber membrane is pre-calcined for 2.8-3.8 hours at 300-350 ℃ in air, and the pre-calcined flexible fiber membrane is calcined for 1-7 hours at 500-700 ℃ in inert atmosphere, wherein the temperature rising rate is 3 ℃ per minute.
2. 2. The method for preparing the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @ C flexible self-supporting positive electrode according to claim 1, wherein in the step (1), the method for preparing the VPO 4 powder by using a sol-gel method is as follows: C 6 H 8 O 7 ·H 2 O、NH 4 VO 3 and NH 4 H 2 PO 4 with the molar ratio of 1:1:1 are dissolved in deionized water, and are magnetically stirred for 3-6 h in an oil pan at 75-85 ℃ to obtain deep blue gel after water is evaporated; And freeze-drying the gel to form a loose porous block material after 30-36 h, and calcining the block material twice to obtain VPO 4 powder.
3. 3. The method for preparing the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting positive electrode according to claim 2, wherein the block material is subjected to two-time calcination as follows: the first calcination is carried out under inert atmosphere, and the calcination is carried out at 320-400 ℃ for 3-5 h; And (3) performing secondary calcination under an inert atmosphere, and calcining at 650-800 ℃ for 6-7 h.
4. 4. The method for preparing the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting positive electrode according to claim 1, wherein in the step (3), the mass ratio of polyacrylonitrile to Na 3 V 2 (PO 4 ) 2 F 3 powder is 1 (0.5-2).
5. 5. The method for preparing the high-voltage Na 3 V 2 (PO 4 ) 2 F 3 @C flexible self-supporting anode according to claim 1, wherein in the step (4), the electrospinning condition is that the voltage is 21 kV, the propelling flow rate is 0.2-0.6 ml/h, the rotating speed of a roller is 200 rpm, the reciprocating distance of a needle is 30 mm, the moving speed is 10 mm/s, and the distance between the needle and the roller is 8-12 cm.
6. 6. A sodium ion battery comprising the high voltage Na 3 V 2 (PO 4 ) 2 F 3 @ C flexible self-supporting positive electrode made by the method of making a high voltage Na 3 V 2 (PO 4 ) 2 F 3 @ C flexible self-supporting positive electrode of any one of claims 1-5.

Description

High-voltage Na 3V2(PO4)2F3 @C flexible self-supporting anode and preparation method and application thereof Technical Field The invention relates to the technical field of flexible electrodes, in particular to a high-voltage Na 3V2(PO4)2F3 @C flexible self-supporting anode, a preparation method and application. Background Along with development and progress of science and technology, people have put higher demands on portability and wearable performance of intelligent electronic devices, and flexible electronic devices have been developed, and have great development prospects. In order for flexible electronic devices to gain popularity, it is critical and challenging to develop a corresponding flexible energy storage system. The flexible energy storage device must meet the portable and flexible standards of the flexible electronic device and still provide uninterrupted power to the flexible electronic device after repeated folding. The application of the flexible lithium ion battery on the flexible device and the wearable equipment has been substantially developed, and compared with the lithium ion battery, the sodium ion battery has obvious safety advantage and cost advantage, and the energy storage mechanism is similar to that of the lithium ion battery. Sodium ion batteries have been considered as the next generation new energy storage batteries most likely to complement lithium ion batteries by virtue of the abundant and inexpensive sodium resource advantages and similar manufacturing processes as lithium ion batteries. In recent years, research on related materials of flexible sodium ion batteries is gradually established, graphene oxide/reduced graphene oxide, carbon nanotubes, carbon cloth and the like are used as carbon substrates, electrode materials are attached to the flexible substrates through methods of dip coating, electrodeposition, coating printing and the like, but the production methods of the graphene oxide/reduced graphene oxide and the carbon nanotubes are complex, high-quality graphene oxide and the carbon nanotubes are high in cost, meanwhile, the contact between the electrode materials and the flexible substrates is rigid contact, and active substances are easy to fall off in repeated charge and discharge processes, so that the electrochemical performance of the flexible sodium ion batteries is affected. Electrospinning technology is considered to be one of the most effective methods for preparing carbon nanofibers with controllable diameter and orientation. The electrostatic spinning has the advantages of few and simple operation steps, one-step molding, controllable morphology and the like. The electrostatic spinning method stretches the polymer solution into filaments through a high-voltage power supply to form nanofibers, and then the nanofiber film is obtained. The polymer liquid drop at the needle opening of the spinning machine generates electric field force opposite to the surface tension direction under a high-voltage electric field, and a Taylor cone is gradually formed along with the increase of the electric field force. When the electric field force overcomes the surface tension, the Taylor cone forms charged jet flow, and is stretched into filaments, and the solvent volatilizes to solidify the fibers, so that the fibers are finally distributed on the receiving device in a disordered manner. In addition, the electrostatic spinning method effectively encapsulates the nano material in the carbon nano fiber through an in-situ chemical method, so that the mechanical property requirement of flexible self-support can be met, and the transmission path of electrons and ions can be shortened. However, the carbon nanofibers have a size requirement on the electrode material, and an oversized electrode material can damage the integrity of the carbon nanofibers and further damage the good mechanical properties of the flexible self-supporting electrode. Na 3V2(PO4)2F3 is used as a polyanion compound, 1mol of Na 3V2(PO4)2F3 can reversibly intercalate 2mol of sodium ions, the specific discharge capacity reaches 128mAh g -1, and meanwhile, the structure stability and the thermal stability are better. Since F - is extremely electronegative, it exhibits an extremely high voltage plateau (approaching 3.9V). However, since the octahedrons of VO 6 in the structure are separated by the PO 4 tetrahedrons, na 3V2(PO4)2F3 has the disadvantages of low conductivity and small sodium ion diffusion coefficient, which greatly limits further development and application. The limitation of the electrostatic spinning on the electrode material size and the defects existing in Na 3V2(PO4)2F3 lead to no report of preparing a high-voltage Na 3V2(PO4)2F3 @C flexible self-supporting anode with good electrochemical performance and mechanical performance by an electrostatic spinning technology at present. Disclosure of Invention The invention aims to provide a high-voltage Na 3V2(PO4)2F3 @C flexible self-supporti