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CN-122025776-A - PVDF-TrFE polymer solid electrolyte based on carbon quantum dot modification and preparation method thereof

CN122025776ACN 122025776 ACN122025776 ACN 122025776ACN-122025776-A

Abstract

The invention provides a PVDF-TrFE polymer solid electrolyte based on carbon quantum dot modification and a preparation method thereof, belonging to the technical field of polymer solid electrolytes. The solid electrolyte takes PVDF-TrFE as a polymer matrix, and simultaneously, a film forming additive and a carbon quantum dot functional filler are added, so that the solid electrolyte not only has higher ionic conductivity, but also can induce uniform deposition of lithium and inhibit dendritic crystal growth. The room-temperature ion conductivity of the PVDF-TrFE polymer solid electrolyte prepared by the invention can reach 7.56 multiplied by 10 ‑4 S/cm, and the Li-Li symmetrical battery assembled by the PVDF-TrFE polymer solid electrolyte prepared by the invention can stably circulate for more than 650 hours without short circuit under the current density of 0.1 mA/cm < 2 >, and has excellent electrochemical stability.

Inventors

  • PENG XIAOLI
  • ZHOU YUQING
  • TANG CHENXIA
  • WEN TAO
  • HU XIAORAN
  • ZHANG QIAN

Assignees

  • 电子科技大学

Dates

Publication Date
20260512
Application Date
20260130

Claims (10)

  1. 1. A PVDF-TrFE polymer solid electrolyte modified based on carbon quantum dots, which is characterized in that the components of the polymer solid electrolyte comprise a polymer matrix, an organic solvent, lithium salt, a plasticizer, a film-forming additive and a functional filler; The polymer matrix is PVDF-TrFE; the film forming additive is fluoroethylene carbonate; the functional filler is histidine functionalized carbon quantum dots.
  2. 2. The PVDF-TrFE polymer solid electrolyte of claim 1, wherein said lithium salt is any one of lithium bis-fluorosulfonimide, lithium hexafluorophosphate, lithium bis-fluorosulfonimide, lithium bis-trifluoromethanesulfonyl imide.
  3. 3. The PVDF-TrFE polymer solid electrolyte of claim 1, wherein said organic solvent is any one of dimethylformamide, acetonitrile, N-methylpyrrolidone, acetone, tetrahydrofuran, dimethyl sulfoxide, trimethyl phosphate.
  4. 4. The PVDF-TrFE polymer solid electrolyte of claim 1, wherein said plasticizer is any one of succinonitrile, adiponitrile, glutaronitrile, ethylene carbonate, sulfolane, trimethylolpropane, polyethylene glycol.
  5. 5. The PVDF-TrFE polymer solid electrolyte according to claim 1, wherein the mass percentage of fluoroethylene carbonate to the polymer matrix is 5% to 10%.
  6. 6. The PVDF-TrFE polymer solid electrolyte of claim 1, wherein the mass percentage of histidine-functionalized carbon quantum dots to the polymer matrix is 2% -3%.
  7. 7. The PVDF-TrFE polymer solid electrolyte of claim 1, wherein said histidine-functionalized carbon quantum dots are obtained according to the following preparation method: Dissolving raw materials in deionized water, reacting for 2-6 hours at 120-200 ℃, naturally cooling, dialyzing, purifying and freeze-drying a reaction product obtained after the reaction is finished to obtain histidine functionalized carbon quantum dot powder with uniform particle size; The raw materials comprise a carbon source and a nitrogen source; The carbon source is citric acid; The nitrogen source is histidine.
  8. 8. The PVDF-TrFE polymer solid electrolyte according to claim 7, wherein the ratio of the amounts of citric acid to histidine is 1 (0.02 to 0.12).
  9. 9. The PVDF-TrFE polymer solid electrolyte according to claim 7, wherein the dialysis is selected to have a molecular weight cut-off of 500 to 1000 Da.
  10. 10. A method for preparing a PVDF-TrFE polymer solid electrolyte according to any one of claims 1 to 9, comprising the steps of: step 1, dissolving a polymer matrix in an organic solvent, and stirring until the polymer matrix is clear to obtain a solution A; Step 2, sequentially adding lithium salt, plasticizer and film forming additive into the solution A, and uniformly stirring to obtain a glue solution B; step 3, adding histidine functionalized carbon quantum dots into the glue solution B, and performing ultrasonic treatment to enable the histidine functionalized carbon quantum dots to achieve molecular-level/nano-level dispersion in the glue solution to obtain mixed slurry; and 4, uniformly coating the mixed slurry on a substrate to form an electrolyte membrane, drying, and removing a membrane layer from the surface of the substrate after drying to obtain the required PVDF-TrFE polymer solid electrolyte.

Description

PVDF-TrFE polymer solid electrolyte based on carbon quantum dot modification and preparation method thereof Technical Field The invention belongs to the technical field of polymer solid electrolytes, and particularly relates to a PVDF-TrFE polymer solid electrolyte based on carbon quantum dot modification and a preparation method thereof. Background With the rapid development of portable electronic devices and electric vehicles, the market demands for energy storage systems with high energy density and high safety are increasingly urgent. The traditional commercial lithium ion battery uses liquid organic electrolyte, has potential safety hazards of inflammability, easy leakage and the like, and cannot be matched with a lithium metal anode with high specific energy (dendrites are easy to puncture a diaphragm, so that the battery is short-circuited and fires). quasi-Solid Polymer Electrolytes (SPEs) are considered as critical materials for next generation lithium batteries due to their good processability, flexibility and safety. Among the numerous polymer matrices, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) is a typical "ferroelectric", the presence of TrFE allowing the polymer chains to naturally form a polar characterThe higher the polarity of the phase (all-trans conformation), the higher the dielectric constant (epsilon > 12), and the higher the dielectric constant, the weakening of coulombic acting force of Li + and anionic groups, promoting dissociation of lithium salt and lowering ion migration activation energy, meanwhile, the rigid chain segment of beta phase enables P (VDF-TrFE) to have better elastic modulus than pure PVDF, and can physically inhibit lithium dendrite penetration, so that PVDF-TrFE based polymer electrolyte is of great interest. However, the existing PVDF-TrFE-based electrolytes still face the following serious challenges in practical applications: The ion conductivity at room temperature is limited, namely PVDF-TrFE semi-crystalline polymer, the high crystallinity area of which prevents the segmental motion of lithium ions (Li+) so that the ion conductivity at room temperature is usually lower than 10 −5 S/cm and the requirement of rapid charge and discharge cannot be met. Interfacial compatibility and dendrite problems when using lithium metal as the negative electrode, deposition of lithium ions on the surface of the negative electrode tends to be non-uniform due to the lack of effective "lithium-philic" sites in the PVDF-TrFE backbone itself. Such non-uniform deposition may result in excessive local current density, induce a tip effect, and grow needle-like lithium dendrites. Lithium dendrites can not only puncture the electrolyte membrane causing a short circuit, but also continuously consume electrolyte, resulting in rapid decay of the battery cycle life. The limitation of the modification means is that in order to increase the conductivity, the industry often adds large amounts of plasticizers (such as succinonitrile SN), but this sacrifices the mechanical strength of the film. In order to inhibit dendrites, inorganic nanofillers (such as SiO 2 and LLZO) are often added, but the inorganic nanofillers have high surface energy, are easy to agglomerate in a polymer matrix, lead to phase separation, and increase interface impedance. A method for preparing a composite solid electrolyte is disclosed in patent CN114784372 a. Therefore, developing a novel modified polymer electrolyte which can not only effectively improve the ionic conductivity, but also induce the uniform deposition of lithium and inhibit the growth of dendrites is a technical problem to be solved currently. Disclosure of Invention Aiming at the problems existing in the background technology, the invention aims to provide a PVDF-TrFE polymer solid electrolyte based on carbon quantum dot modification and a preparation method thereof. The solid electrolyte takes PVDF-TrFE as a polymer matrix, and simultaneously, a film forming additive and a carbon quantum dot functional filler are added, so that the solid electrolyte not only has higher ionic conductivity, but also can induce uniform deposition of lithium and inhibit dendritic crystal growth. In order to achieve the above purpose, the technical scheme of the invention is as follows: a PVDF-TrFE polymer solid electrolyte modified based on carbon quantum dots, wherein the components of the polymer solid electrolyte comprise a polymer matrix, an organic solvent, lithium salt, a plasticizer, a film-forming additive and a functional filler; The polymer matrix is PVDF-TrFE; The film forming additive is fluoroethylene carbonate (FEC); the functional filler is histidine functionalized carbon quantum dots (His-CQDs). Further, the lithium salt is any one of lithium bis (fluorosulfonyl) imide (LiFSI), lithium hexafluorophosphate (LiPF 6), lithium bis (fluorosulfonyl) imide (LiFSI), and lithium bis (trifluoromethanesulfonyl) imide (LiTFSI). Further, the organic solve