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CN-122000452-A - Method for in-situ construction of PVDF-HFP-based composite solid electrolyte NaF-rich interface layer by plasma assistance and application thereof

CN122000452ACN 122000452 ACN122000452 ACN 122000452ACN-122000452-A

Abstract

The invention discloses a method for constructing a PVDF-HFP-based composite solid electrolyte NaF-rich interface layer in situ with the aid of plasma and application thereof, and relates to the technical field of solid batteries. The invention adopts dielectric barrier discharge plasma technology to modify the surface of PVDF-HFP composite solid electrolyte to optimize the interface components, improves the interface compatibility of the composite solid electrolyte and electrode materials, enhances the ion transmission performance of PVDF-HFP based composite solid electrolyte, and reduces the interface impedance between the composite solid electrolyte and the electrode. The surface NaF ratio of the PVDF-HFP based composite solid electrolyte obtained after the modification by the plasma treatment is improved from 21.49% to 67.48%, the ionic conductivity of the example 3 is improved by nearly 2 times compared with that of the comparative example 1, the interface impedance of the solid sodium symmetrical battery is reduced by nearly 40%, and the PVDF-HFP based composite solid electrolyte shows excellent multiplying power and cycle performance when being applied to sodium metal solid batteries. The method of the invention has the advantages of easy operation, short period and low cost, and is helpful for promoting the commercial application of PVDF-HFP based composite solid electrolyte.

Inventors

  • LIANG FENG
  • CHEN SONG
  • HOU MINJIE
  • YANG BIN

Assignees

  • 昆明理工大学

Dates

Publication Date
20260508
Application Date
20260205

Claims (10)

  1. 1. A method for preparing PVDF-HFP based composite solid electrolyte, which is characterized by comprising the following steps: (1) Preparing polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) based composite solid electrolyte, namely weighing PVDF-HFP, inorganic filler and additive powder according to a preset proportion, dissolving the inorganic filler, PVDF-HFP and additive in a solvent, stirring for a first preset time to obtain a first mixed solution, carrying out ultrasonic mixing on the first mixed solution for a second preset time to obtain composite solid electrolyte precursor slurry, casting the composite solid electrolyte precursor slurry on a preset template, carrying out vacuum drying to remove the solvent, forming, taking out the PVDF-HFP based composite solid electrolyte from the preset template, and rolling to obtain a PVDF-HFP based composite solid electrolyte membrane, wherein the additive comprises polyethylene glycol (PEG) and sodium hexafluorophosphate (NaPF 6 ); (2) And (3) performing plasma-assisted in-situ construction on the surface of the PVDF-HFP-based composite solid electrolyte membrane obtained in the step (1) by adopting dielectric barrier discharge plasma in a nitrogen atmosphere so as to convert the PVDF-HFP and the additive on the surface of the PVDF-HFP-based composite solid electrolyte into sodium fluoride (NaF) and obtain the PVDF-HFP-based composite solid electrolyte with a NaF-rich interface layer.
  2. 2. The method of claim 1, wherein the predetermined ratio is PVDF-HFP, the sum of the inorganic filler and additive powder and the PVDF-HFP, the sum of the inorganic filler and additive powder is PVDF-HFP (wt.40%), the inorganic filler (wt.40%), the additive polyethylene glycol (PEG) and sodium hexafluorophosphate (NaPF 6 ) are each (wt.10%).
  3. 3. The method of claim 1, wherein the inorganic filler is sodium ion superconductor (NASICON) inorganic solid electrolyte Na 3 Zr 2 Si 2 PO 12 synthesized by solid phase sintering.
  4. 4. The method of claim 1, wherein the solvent comprises acetone, N-Dimethylformamide (DMF), and the additive is polyethylene glycol (PEG) or sodium hexafluorophosphate (NaPF 6 ).
  5. 5. The method according to claim 1, wherein the step of stirring the PVDF-HFP, inorganic filler and additive in the solvent for a first predetermined time includes stirring the PVDF-HFP, inorganic filler and additive in the solvent for a first predetermined time by using a magnetic stirrer to obtain a first mixed solution, and the step of transferring the first mixed solution to be ultrasonically mixed for a second predetermined time includes ultrasonically mixing the first mixed solution for the second predetermined time by using an ultrasonic instrument to obtain a composite solid electrolyte precursor slurry, wherein the first predetermined time is 8 hours to 12 hours, and the second predetermined time is 30 to 60 minutes.
  6. 6. The method according to claim 1, wherein the step of performing plasma modification treatment on the surface of the PVDF-HFP based composite solid electrolyte comprises performing plasma modification treatment on both the front and back surfaces of the PVDF-HFP based composite solid electrolyte, wherein the plasma modification treatment uses a preset gas flow rate, a preset voltage, a preset current and a third preset time at atmospheric pressure, the preset gas flow rate is the preset gas flow rate for the nitrogen atmosphere, the preset voltage is a voltage applied to the front and back surfaces of the PVDF-HFP based composite solid electrolyte and is 50V-100V, the preset current is a current of 1A and the third preset time is 10 seconds-60 seconds.
  7. 7. The method according to claim 1, wherein the step of casting the precursor slurry into the preset template and then vacuum drying to form the PVDF-HFP based composite solid electrolyte membrane comprises casting the precursor slurry onto the surface of the preset template, placing the precursor slurry into a vacuum drying oven to dry for a fourth preset time, and then adjusting the temperature in the vacuum drying oven to a preset temperature and maintaining the temperature for a fifth preset time to obtain the PVDF-HFP based composite solid electrolyte membrane, wherein the fourth preset time ranges from 1 hour to 2 hours, the preset temperature ranges from 60 ℃, and the fifth preset time ranges from 12 hours.
  8. 8. The method according to claim 1, wherein the PVDF-HFP based composite solid electrolyte membrane has a thickness of 30 μm to 60. Mu.m, and the plasma surface modification treatment modifies both sides of the PVDF-HFP based composite solid electrolyte membrane to obtain the PVDF-HFP based composite solid electrolyte with NaF-rich interface layer having a thickness of 30 μm to 60. Mu.m.
  9. 9. The PVDF-HFP based composite solid electrolyte with the NaF-rich interface layer comprises a matrix and the NaF-rich interface layer formed on the front surface and the back surface of the matrix, wherein the matrix comprises a PVDF-HFP polymer matrix, a PEG plasticizer, an inorganic filler of NASICON (Na 3 Zr 2 Si 2 PO 12 ) and a sodium salt additive of NaPF 6 , and the NaF-rich interface layer is formed by dissociation of C-F covalent bonds on the front surface and the back surface of the matrix and in-situ decomposition of NaPF 6 .
  10. 10. A sodium metal battery is characterized in that the NaF-rich interfacial layer PVDF-HFP-based composite solid electrolyte, a sodium metal negative electrode and a sodium vanadium phosphate positive electrode in the claims 1-9 are assembled into the sodium metal battery.

Description

Method for in-situ construction of PVDF-HFP-based composite solid electrolyte NaF-rich interface layer by plasma assistance and application thereof Technical Field The invention relates to the field of solid battery materials, in particular to a method for enriching a NaF interface layer of PVDF-HFP-based composite solid electrolyte and application thereof. Background With the rapid development of new energy industry, energy storage devices with high safety and high energy density become research hotspots. Solid-state sodium metal batteries are considered as one of the energy storage technologies with great potential for the next generation because of the abundant sodium resource reserves, low cost and excellent safety. The performance of the solid electrolyte, which is used as a core component of a solid sodium metal battery, directly determines the energy density, the cycling stability and the safety performance of the battery. Among them, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) is often used as a matrix material of a composite solid electrolyte because of its excellent electrochemical stability, thermal stability, mechanical processability and electrode suitability. In the prior art, the PVDF-HFP based composite solid electrolyte is prepared by the processes of solution casting, drying and forming and the like of raw materials such as a polymer blend, inorganic electrolyte powder, sodium salt and the like, and an ion conduction channel is constructed by adding inorganic electrolyte powder such as NASICON (sodium super ion conductor) and the like for improving the ion conduction performance, and PEG (polyethylene glycol) is introduced for improving the flexibility of a polymer matrix and the ion migration environment. However, the PVDF-HFP based composite solid electrolyte prepared by the process generally has a solid electrolyte interface layer mainly comprising organic components, and the solid electrolyte interface layer generally has poor mechanical properties, resulting in poor compatibility with an electrode interface and insufficient interface stability, thereby exacerbating interface side reactions and forming a large interface impedance to hinder ion transmission, and reducing the battery cycle performance. Therefore, developing a PVDF-HFP based composite solid electrolyte and a preparation method of a stable interface layer thereof has important significance for improving the performance of sodium-based solid batteries and promoting the industrialized application of the sodium-based solid batteries. Disclosure of Invention The invention aims to overcome the defects of poor interface compatibility, high interface impedance, difficult inhibition of sodium dendrite growth, limited battery performance and the like of a PVDF-HFP-based composite solid electrolyte and an electrode in the prior art, and provides a method for constructing a NaF-rich interface layer of the PVDF-HFP-based composite solid electrolyte in situ by plasma assistance and application thereof. Through dielectric barrier discharge plasma technology with specific parameters, a NaF-rich interface layer is formed in situ at a solid electrolyte interface, so that the optimization of interface components is realized, the interface impedance is reduced, the interface stability and the sodium dendrite resistance are improved, and finally the cycle life and the electrochemical performance of the sodium-based solid-state battery are obviously improved. The technical scheme of the invention is as follows: The PVDF-HFP-based composite solid electrolyte containing the NaF-rich interface layer comprises a matrix and the NaF-rich interface layer formed on the front surface and the back surface of the matrix, wherein the matrix comprises a PVDF-HFP polymer matrix, a PEG plasticizer, an NASICON (Na 3Zr2Si2PO12) inorganic electrolyte filler and a NaPF 6 sodium salt additive, the composite electrolyte matrix is subjected to dielectric barrier discharge plasma treatment with specific parameters, and the dissociation of C-F covalent bonds and the in-situ decomposition of NaPF 6 in the PVDF-HFP matrix are realized through the reaction of high-energy particle collision generated by plasma and high-activity components, so that the NaF-rich high-performance solid electrolyte interface layer is formed in-situ at the solid electrolyte interface, and the technological parameters of the dielectric barrier discharge plasma comprise that the discharge voltage is 50-100V, the discharge current is 1A, and nitrogen is used as a plasma source. In order to realize the above-mentioned plasma-assisted in-situ construction method of PVDF-HFP based composite solid electrolyte NaF-rich interface layer, the method specifically comprises the following steps: (1) Preparing polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) based composite solid electrolyte, namely weighing PVDF-HFP, inorganic filler and additive powder according to a p