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CN-121991606-A - Conductive-adhesive bifunctional polymer adhesive, preparation method thereof and application thereof in sodium ion battery

CN121991606ACN 121991606 ACN121991606 ACN 121991606ACN-121991606-A

Abstract

The invention belongs to the field of sodium ion battery binders, and discloses a conductive-bonding bifunctional polymer binder, a preparation method thereof and application thereof in sodium ion batteries. The invention prepares the conjugated polymer containing C=C by preparing strong reducing solution from ether solvent, aromatic hydrocarbon compound and metallic sodium to controllably defluorinate polyvinylidene fluoride, and endows the conjugated polymer with good electronic conductivity. The electrode prepared by the conductive adhesive can effectively reduce the proportion of traditional inactive components, remarkably improve the multiplying power performance and energy density of the electrode, and provide wide research prospect and application value for the design and development of high-performance sodium ion batteries.

Inventors

  • LI FUJUN
  • LI FEI
  • WEI XIANGSHUAI

Assignees

  • 南开大学

Dates

Publication Date
20260508
Application Date
20260119

Claims (10)

  1. 1. A method for preparing a conductive-adhesive bifunctional polymer adhesive, which is characterized by comprising the following steps: s1, mixing metal sodium, aromatic hydrocarbon compounds and ether solvents, and reacting to form a strong-reducibility solution; S2, dissolving polyvinylidene fluoride in an organic solvent to form a polyvinylidene fluoride solution; S3, mixing the strong-reducibility solution with the polyvinylidene fluoride solution, and carrying out defluorination under the stirring condition, wherein a carbon-carbon double bond conjugated structure is introduced in situ on a polyvinylidene fluoride molecular chain in the defluorination; s4, carrying out recrystallization treatment on the reacted solution, washing and drying to obtain modified polyvinylidene fluoride powder, namely the conductive-bonding bifunctional polymer binder.
  2. 2. The preparation method of claim 1, wherein in the step S1, the aromatic hydrocarbon compound is one or more of 2, 2-bipyridine, biphenyl, naphthalene, anthracene and benzophenone, the ether solvent is one or more of ethylene glycol diethyl ether, ethylene glycol dimethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran, and the concentration of the strong reducing solution is 0.01 mol L -1 ~1 mol L -1 .
  3. 3. The preparation method of claim 1, wherein in the step S2, the organic solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide and dimethyl sulfoxide, the molecular weight of polyvinylidene fluoride is 400,000-2,000,000, and the mass ratio of polyvinylidene fluoride to the organic solvent is 1:10-1:100.
  4. 4. The preparation method according to claim 1, wherein the volume ratio of the strong reducing solution to the polyvinylidene fluoride solution is 0.2:1-0.3:1, the reaction temperature is 25-60 ℃, and the reaction time is 0.5-3 hours.
  5. 5. The method according to claim 1, wherein in step S4, the re-crystallization is performed by adding the mixed solution after the reaction to water or ethanol to form a precipitate, and the drying is performed under a vacuum condition of 60-80 ℃.
  6. 6. A conductive-adhesive bifunctional polymeric binder prepared by the process of any one of claims 1 to 5, having the structural formula: wherein x+y is 1, and x:y is 1:0 to 0:1.
  7. 7. A sodium ion battery electrode sheet comprising a current collector and an active material layer disposed on the surface of the current collector, wherein the active material layer comprises an active material, a conductive agent, and the conductive-adhesive bifunctional polymer binder of claim 6.
  8. 8. The sodium ion battery electrode sheet according to claim 7, wherein the mass ratio of the active material is 93% to 98%, the mass ratio of the conductive-adhesive bifunctional polymer binder is 2% to 7%, and the mass ratio of the conductive agent is 0% to 2%, based on 100% of the total mass of the active material layer.
  9. 9. A sodium ion battery comprising a positive plate, a negative plate, a diaphragm and electrolyte, wherein the positive plate and/or the negative plate is the sodium ion battery electrode plate according to claim 7 or 8.
  10. 10. The sodium ion battery of claim 9, wherein the active material of the positive electrode sheet is at least one of a layered oxide, a polyanion compound or a Prussian blue type material, and the active material of the negative electrode sheet is a hard carbon or metallic sodium sheet.

Description

Conductive-adhesive bifunctional polymer adhesive, preparation method thereof and application thereof in sodium ion battery Technical Field The invention belongs to the technical field of sodium ion batteries, and particularly relates to a conductive-bonding bifunctional polymer binder, a preparation method thereof and application thereof in sodium ion batteries. Background The sodium resources are abundant in the crust, uniformly distributed and low in cost, and the application of the sodium ion battery in large-scale energy storage is expected to be promoted. The energy density is used as a core index for improving the performance and the economy of the battery, and the application value and the industrialization potential of the battery are directly determined. Sodium ion batteries are limited in energy density by the relatively large intrinsic mass and radius of the sodium ions, resulting in limited electrode material capacity and lower battery operating voltages. In recent years, increasing the energy density of sodium ion batteries has become an important research point, and the main strategy is to optimize electrode materials and electrolyte. The method can enhance the energy storage capacity of the battery by developing high-voltage/high-capacity positive electrode materials (such as element doping and anion redox strategies), improving the performance of hard carbon materials and exploring a higher-capacity negative electrode system (such as alloy materials), widens the electrochemical window of electrolyte and builds a stable solid electrolyte interface, and is beneficial to ensuring the stable operation of the battery under high voltage. However, the energy density of sodium ion batteries is generally 80-160 Wh/kg, and the traditional modification method is difficult to bring about remarkable breakthrough, and the energy density is approaching the limit. The energy density is not only dependent on the capacity of the electrode material and the operating voltage of the battery, but is also affected by the overall quality. Besides active substances, the electrode also comprises inactive components such as a binder, a conductive agent and the like, and the mass ratio of the inactive components is about 5% -20%. Thus, the energy density of the battery can be further increased by increasing the active material loading by decreasing the inactive component ratio. The binder is a key material with a large proportion in the inactive component, and mainly comprises polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR) and the like. Currently, research work in this area has focused mainly on improving its cohesiveness and elasticity by manipulating the molecular structure. However, these binders are generally poor in conductivity, and require the addition of a large amount of conductive agents (e.g., carbon black, super P, etc.) to the battery to ensure efficient electron transport, while the introduction of a large amount of inactive components limits the improvement in energy density of the battery. In order to reduce the content of inactive components, researchers have attempted to develop conductive adhesives. The prior art mainly adopts a physical blending strategy, namely, mechanically mixing traditional binders such as PVDF and the like with externally added conductive polymers such as polyaniline, polypyrrole, polythiophene or poly-p-phenylene ethylene and the like (for example, a comparison document CN104282912A, CN104861897A, CN 115216245A). However, the method has inherent defects that (1) the physical mixing is uneven, the phase separation is easy to occur, the stability of the electrode slurry is influenced, (2) the interface resistance between the insulating adhesive matrix and the conductive filling phase is large, the electron conduction efficiency is limited, and (3) the functions of the adhesive and the conductive agent are mutually independent, so that the total content of inactive substances cannot be fundamentally reduced. Another technique (such as CN114824258 a) attempts to improve the mechanical properties of PVDF by crosslinking and then compounding with conductive polymers, but does not change the nature of the physical composite conductivity, the process is complex and the uniformity of the conductive network is to be improved. Therefore, a single-component material which enables the binder to have good cohesiveness and intrinsic high electronic conductivity through molecular design is developed, the traditional system of the binder and the conductive agent is fundamentally replaced, and the method has important significance for realizing the high-energy-density sodium ion battery. Disclosure of Invention Aiming at the defects that most of the existing conductive adhesives are interface problems, low electronic conduction efficiency and high ratio of inactive components in the physical blending composite material, the invention aims to