A fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte, a preparation method and application thereof

Abstract

The application discloses a fluorine quantum dot combined fluorinated UIO-66 (FUIO) molecular sieve composite polymer solid electrolyte and a preparation method and application thereof, and belongs to the technical field of lithium metal batteries. The electrolyte comprises H-FCDs@FUIO, polyethylene oxide and a lithium salt; the H-FCDs@FUIO is formed by combining fluorine quantum dots and FUIO through fluorophilic interaction, hydrogen bonding and coordination; and the FUIO is a fluorinated UIO-66 molecular sieve. The electrolyte has high ion conductivity, a wide electrochemical window, good stability and the like by introducing the double fluorine structure of the fluorine quantum dots and the FUIO molecular sieve and synergizing the polyethylene oxide, and when the electrolyte is applied to the preparation of a solid-state lithium metal battery, the Coulomb efficiency of the battery can be obviously improved and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] This invention relates to a fluorine quantum dot-based FUIO molecular sieve composite polymer solid electrolyte, as well as its preparation method and its application in solid lithium metal batteries, belonging to the field of lithium metal battery technology. Background Technology

[0002] The ever-increasing demand for high-energy-density storage systems in electric vehicles, portable electronic devices, and other applications has spurred in-depth and systematic research into rechargeable batteries to meet practical needs. Safety issues arising from leakage and combustion of liquid electrolytes commonly used in lithium metal batteries are frequent. Therefore, developing solid-state lithium metal batteries with high safety, high energy density, and a wide operating temperature range is of paramount importance.

[0003] Polymer solid-state electrolytes (SPEs) are considered the most promising new electrolytes due to their advantages such as high flexibility, low cost, strong plasticity, and excellent interfacial compatibility with lithium metal. However, the high crystallinity of the polymer matrix leads to poor ion migration, resulting in low ionic conductivity, which is the biggest challenge facing this electrolyte. At the same time, the electrochemical window of polymer solid-state electrolytes is narrow (typically below 4.0V), limiting their compatibility with high-voltage cathode materials. Furthermore, the mechanical strength of polymer electrolytes is insufficient to suppress lithium dendrite growth, which typically leads to capacity reduction and, more seriously, internal short circuits in the battery.

[0004] Therefore, it is of great significance to develop a solid polymer electrolyte that combines high conductivity, wide electrochemical window and good stability. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the first objective of this invention is to provide a solid electrolyte composed of fluorine quantum dots and FUIO molecular sieves. This electrolyte, by introducing a dual-fluorine structure of fluorine quantum dots and FUIO molecular sieves, and synergistically combining with polyethylene oxide, exhibits characteristics such as high ionic conductivity, wide electrochemical window, and good stability.

[0006] The second objective of this invention is to provide a method for preparing a solid electrolyte of fluorine quantum dots combined with FUIO molecular sieve composite polymer. This method is simple, uses readily available raw materials, is inexpensive, and is suitable for large-scale industrial production.

[0007] The third objective of this invention is to provide an application of a fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte, which has high ionic conductivity, wide chemical window and stability. When applied to the preparation of solid lithium metal batteries, it can significantly improve the coulombic efficiency of the battery and extend the battery cycle life.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a fluorine quantum dot-based FUIO molecular sieve composite polymer solid electrolyte, comprising H-FCDs@FUIO, polyethylene oxide (PEO), and lithium salt; wherein the H-FCDs@FUIO is formed by combining fluorine quantum dots and FUIO through fluorine-loving interactions, hydrogen bonds, and coordination interactions; and wherein the FUIO is a fluorinated UIO-66 molecular sieve.

[0009] The solid electrolyte of the present invention, which combines fluorine quantum dots with FUIO molecular sieve composite polymer, exhibits stable structure and excellent performance. Specifically, due to the abundance of hydroxyl and CF bonds on the surface of fluorine quantum dots, they readily form OH···F or OH···O type hydrogen bond networks and can attract lithium salt anions through electrostatic interactions. However, if fluorine quantum dots are directly added to polyethylene oxide, the quantum dots are prone to uneven dispersion and agglomeration, severely restricting the electrolyte's performance. Therefore, the present invention employs fluorinated UIO-66 molecular sieve (FUIO) and fluorine quantum dots for composite modification. FUIO has a regular octahedral crystal structure and a three-dimensional interconnected network, and its highly uniform microporous structure surface is rich in fluorine functional groups. Unlike the prior art where ZIF67 anchors nitrogen-doped boron quantum dots through N-Co coordination, the present invention utilizes the fluorinated structural characteristics of FUIO, which can simultaneously generate fluorinophilic interactions, multiple hydrogen bonds, and coordination interactions with fluorine quantum dots, firmly and uniformly anchoring the fluorine quantum dots to the metal center of the FUIO framework, forming a structurally stable H-FCDs@FUIO composite.

[0010] This composite approach not only effectively suppresses quantum dot aggregation but also introduces a unique ion regulation mechanism: On one hand, the molecular sieve effect of FUIO allows lithium ions to selectively pass through its pores, while fluorine quantum dots and FUIO work together to trap anions. The highly fluorinated pore environment and the surface of the fluorine quantum dots synergistically form a strong electronegativity, which enhances electrostatic repulsion and steric hindrance for lithium salt anions, significantly suppressing anion polarization and thus significantly improving lithium ion migration efficiency and system conductivity. On the other hand, the ultra-high specific surface area of ​​FUIO increases the volume of free chain segments at the interface in contact with the polymer electrolyte, further improving ion transport. More importantly, the abundant F element introduced in H-FCDs@FUIO can enhance antioxidant capacity through a strong electronegativity environment, making it more difficult for the electrolyte to lose electrons, thereby increasing the electrolyte's electrochemical stability window from below 4V inherent to polyethylene oxide to above 5V. It can also induce the formation of a robust SEI layer rich in LiF at the lithium anode interface, improving interfacial mechanical strength and effectively suppressing lithium dendrite growth, thus significantly improving the cycle stability and safety of the battery.

[0011] As a preferred embodiment, the mass ratio of H-FCDs to FUIO in the H-FCDs@FUIO is (5~7.5):100. If too much H-FCDs is added, the highly electronegative CF bonds on the fluorocarbon dot surface will excessively bind lithium ions (e.g., forming strong F···Li⁺ coordination), reducing the dissociation and migration rate of lithium ions; if too little H-FCDs is added, it will lead to insufficient anion suppression, a significant decrease in high voltage stability and interface protection capability.

[0012] As a preferred embodiment, the FUIO has an octahedral crystal structure with an average pore size of 3.5~4 nm. The FUIO of this invention has a regular crystal structure with equal pore sizes, which allows for better fixation of fluorine quantum dots and better screening of lithium ions.

[0013] As a preferred embodiment, the preparation process of FUIO is as follows: zirconium salt and fluorine-containing organic ligand are subjected to a solvothermal reaction in the presence of an organic solvent and glacial acetic acid.

[0014] As a preferred embodiment, the zirconium salt comprises at least one of zirconium nitrate and ZrCl4, the fluorinated organic ligand comprises tetrafluoroterephthalic acid, the organic solvent comprises DMF, and the solution thermal reaction is carried out at a temperature of 120-140°C for 24-48 hours. In this invention, if the temperature is too low, the reaction energy is insufficient, leading to insufficient reaction energy between the fluorinated organic ligand and ZrCl4. 4+ Incomplete coordination results in poor crystallinity of the generated FUIO; while excessively high temperatures lead to overly vigorous reactions, causing partial decomposition of fluorinated organic ligands or the generation of amorphous impurities, and even pore collapse. Although thermal stability is improved, pore characteristics are deteriorated.

[0015] As a preferred embodiment, the molar ratio of the zirconium salt to the fluorinated organic ligand is (1~2):(1~2). In this invention, it is necessary to control the molar ratio of the zirconium salt to the fluorinated organic ligand within a similar molar range to ensure that Zr... 4+ The ions can obtain sufficient ligands without excess, thus ensuring the special stereostructure of the FUIO particles. A further preferred ratio is 1:(1~1.2).

[0016] As a preferred embodiment, the regulator comprises glacial acetic acid.

[0017] As a preferred embodiment, the mass ratio of H-FCDs@FUIO to polyethylene oxide is (1~11):100. Within the preferred mass ratio range of this invention, good film-forming properties and flexibility can be maintained while ensuring excellent lithium-ion migration efficiency and interfacial stability. If the mass ratio is too low, the filler content is too small, making it difficult to form continuous and fast ion transport channels. The electrostatic repulsion and steric hindrance effects on anions are insufficient, and the crystallinity of the PEO matrix is ​​only reduced to a limited extent, resulting in no significant improvement in lithium-ion migration efficiency and system conductivity. Furthermore, the lack of fluorine makes it difficult to stably broaden the electrochemical stability window to above 5V. When the mass ratio is too high, although it can significantly reduce the crystallinity of PEO, provide abundant anion trapping sites, and enhance interfacial LiF formation, excessive inorganic fillers will, to some extent, damage the continuity and flexibility of the PEO chain segments.

[0018] As a preferred embodiment, the ratio of lithium salt to polyethylene oxide is 1:(10~20) based on the molar ratio of lithium ions in the lithium salt to oxygen atoms in the polyethylene oxide. The ratio of lithium salt to polyethylene oxide is preferably controlled within a preferred range. If the ratio of polyethylene oxide is too high, more crystalline regions will form in the polyethylene oxide matrix, and the presence of these crystalline regions will inhibit lithium ion transport. Conversely, if the ratio of polyethylene oxide is too low, the insufficient number of alkoxy ether chains will reduce the adsorption capacity for lithium ion transport and decrease ionic conductivity.

[0019] As a preferred embodiment, the lithium salt comprises lithium bis(trifluoromethanesulfonyl)imide. The lithium salt containing polar organic groups preferred in this invention can improve its dispersibility and dissociation in organic solid electrolytes, and can also produce a better synergistic effect with the introduced H-FCDs@FUIO.

[0020] This invention also provides a method for preparing a solid electrolyte of fluorine quantum dots combined with FUIO molecular sieve composite polymer. The method involves mixing H-FCDs@FUIO, polyethylene oxide, lithium salt, and solvent evenly, and then sequentially molding and drying the mixture to obtain the desired product.

[0021] As a preferred embodiment, the solvent is an organic solvent, such as methanol.

[0022] As a preferred embodiment, the mixing time is 25~30℃ for 12 hours, and the solution after the reaction is completed needs to be allowed to stand for 12~16 hours to allow the product to precipitate.

[0023] As a preferred embodiment, the solid powder obtained after settling needs to be washed with a centrifuge at a speed of 5000~8000 r / min for 5~10 min each time, using anhydrous ethanol as the solvent, and washed three times. The solid powder obtained after washing also needs to be dried in a vacuum oven at a temperature of 55~60℃. Too high a temperature will cause FUIO to decompose and change its structure, while too low a temperature will result in solvent residue. The drying time is 10~12 h.

[0024] As a preferred embodiment, the preparation process of H-FCDs@FUIO involves mixing and reacting H-FCDs with FUIO in a solvent. In this invention, the surface of H-FCDs is rich in hydroxyl groups, which can form OH···F or OH···O type hydrogen bonds with the abundant terminal hydroxyl groups on the Zr6O4(OH)4 cluster of FUIO, or coordinate with the metal center of FUIO. Simultaneously, the abundant CF bonds in H-FCDs can interact with the F in FUIO through fluorophilic interactions, thereby forming a more structurally stable H-FCDs@FUIO composite, effectively suppressing quantum dot aggregation while retaining their respective properties.

[0025] As a preferred embodiment, the H-FCDs are obtained by a condensation reaction of a fluorinated aromatic aldehyde and an α-H-containing aldehyde under alkaline conditions. The fluorinated aromatic aldehyde and the α-H-containing aldehyde repeatedly undergo the Claisen-Schmidt reaction to form a fluorinated α,β-unsaturated aldehyde-ketone polymer, which is then dehydrated. The resulting polymer further crosslinks and cyclizes to form a carbon dot network with conjugated structures and abundant fluorine functional groups. Compared with traditional hydrothermal reactions, the method employed in this invention provides milder reaction conditions, which is more conducive to preserving fluorine functional groups. The special cross-condensation reaction mode helps to reduce the influence of side reactions, and this reaction method achieves gram-scale preparation of fluorine quantum dots with considerable yield.

[0026] As a preferred embodiment, the molar ratio of the fluorinated aromatic aldehyde to the α-H-containing aldehyde is (1~2):(2~3). If the content of the α-H-containing aldehyde in the system is low, the reaction is incomplete, and there is an excess of fluorinated aromatic aldehyde, which increases the side reactions; while if the α-H-containing aldehyde is in excess, the self-condensation reaction of the α-H-containing aldehyde dominates, and the fluorination ratio of the obtained product is too low.

[0027] As a preferred embodiment, the fluorinated aromatic aldehyde includes pentafluorobenzaldehyde, and the α-H-containing aldehyde includes acetaldehyde.

[0028] As a preferred embodiment, the condensation reaction is performed under the following conditions: a temperature of 25-35°C and a time of 4-5 days.

[0029] As a preferred embodiment, the conditions for the mixing reaction are: temperature of 25~30℃ and time of 12~24h.

[0030] Under the preferred condensation and mixing reaction conditions of this invention, a composite polymer solid electrolyte with superior overall performance can be obtained.

[0031] Finally, this invention also provides an application of a fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte, which is used to prepare solid lithium metal batteries. Thanks to the high ionic conductivity, wide chemical window and stability of this electrolyte, solid lithium metal batteries can significantly improve the coulombic efficiency and extend the cycle life of the battery, while also being able to match high-voltage cathode materials.

[0032] The preparation process of the solid-state lithium metal battery involved in this invention is as follows: assembling the negative electrode shell, negative electrode sheet, solid electrolyte, positive electrode sheet, and positive electrode shell in sequence. The negative electrode sheet is lithium metal; the positive electrode sheet preparation steps are as follows: weighing lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride, adding N-methylpyrrolidone and stirring to form a uniform slurry, then uniformly coating it onto aluminum foil using a coating machine, drying it under vacuum, and cutting it into positive electrode discs using a die-cutting machine.

[0033] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0034] (1) The fluorine quantum dot combined with FUIO molecular sieve composite solid electrolyte of the present invention can effectively promote the dissociation of lithium salt. The hydroxyl groups on the surface of H-FCDs form OH···F or OH···O type hydrogen bonds with the abundant terminal hydroxyl groups on the Zr6O4(OH)4 cluster of FUIO, adsorbing anions in lithium salt and releasing more free lithium ions, which can improve the ionic conductivity of the electrolyte. At the same time, the unique pore size after being combined with FUIO can act as a molecular sieve, capturing larger anions in the electrolyte and allowing only lithium ions to pass through freely, further improving the conductivity of the system. In addition, H-FCDs@FUIO contains a large amount of F element, which is conducive to the formation of a LiF-rich SEI layer at the interface between the electrolyte and the negative electrode, improving the mechanical properties of the SEI layer, inhibiting the formation of lithium dendrites, and thus improving the battery stability. At the same time, the introduction of a large amount of F improves the oxidation resistance of the system, making it more difficult for the electrolyte to lose electrons, thereby increasing the electrochemical stability window from less than 4V inherent to PEO to more than 5V.

[0035] (2) This invention benefits from the high ionic conductivity, wide chemical window and stability of the fluorine quantum dot combined with FUIO molecular sieve composite solid electrolyte. When applied to the preparation of solid lithium metal batteries, the solid lithium metal batteries can significantly improve the coulombic efficiency of the batteries and extend the cycle life of the batteries. At the same time, it can be matched with high voltage cathode materials, which greatly expands its application range. Attached Figure Description

[0036] Figure 1In the image, a is a scanning electron microscope (SEM) image of FUIO prepared in Example 1 of this invention, and b is a scanning electron microscope (SEM) image of H-FCDs@FUIO prepared in Example 1.

[0037] Figure 2 The ionic conductivity diagrams of the fluorine quantum dot-combined FUIO molecular sieve composite solid electrolytes prepared in Examples 1-5 at different temperatures are shown.

[0038] Figure 3 Linear sweep voltammetry curves of two electrolyte membranes: H-FCDs@FUIO (5wt%) / PEO electrolyte and PEO electrolyte.

[0039] Figure 4 To test the cycling performance of Li||H-FCDs@FUIO(5wt%) / PEO electrolyte and PEO electrolyte full cells and Li||PEO||LFP full cells, two electrolyte membranes were assembled with H-FCDs@FUIO(5wt%) / PEO and PEO electrolyte, respectively, at 1C and 80℃. Detailed Implementation

[0040] The present invention will be further described in detail below through specific embodiments, but this should not be construed as limiting the scope of protection of the claims of the present invention.

[0041] Conductivity measurements were performed using an SP-200 electrochemical workstation. The prepared boron quantum dots were combined with a ZIF67 molecular sieve composite solid polymer electrolyte to assemble an SS / SS (SS, stainless steel electrode) battery. The corresponding formula is:

[0042]

[0043] In the formula, v is the ionic conductivity, L is the electrolyte thickness, S is the contact area between the electrolyte and the stainless steel electrode sheet, and R is the electrolyte impedance.

[0044] Example 1

[0045] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0046] In step (2), 4.29 g (10 mmol) of Zr(NO3)4-5H2O was dissolved in 90 ml of DMF. Then, 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution, and the mixture was stirred at room temperature until the solid was completely dissolved. The mixture was transferred to a 200 ml reactor and reacted at 120 °C for 24 hours. After the reaction, the product was washed three times with DMF and centrifuged at 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0047] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0048] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.004 g of H-FCDs@FUIO were dissolved in 9 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (1 wt%). At 30 °C, the ionic conductivity was 6.9 × 10⁻⁶. -5 S / cm, where 1wt% refers to the percentage of H-FCDs@FUIO in the mass of PEO, and the remaining mass fractions are calculated in the same way.

[0049] Example 2

[0050] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0051] In step (2), 4.29 g (10 mmol) of Zr(NO3)4-5H2O was dissolved in 90 ml of DMF. Then, 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution, and the mixture was stirred at room temperature until the solid was completely dissolved. The mixture was transferred to a 200 ml reactor and reacted at 120 °C for 24 hours. After the reaction, the product was washed three times with DMF and centrifuged at 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0052] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0053] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.012 g of H-FCDs@FUIO were dissolved in 8 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (3 wt%). At 30 °C, the ionic conductivity was 8.9 × 10⁻⁶. -5 S / cm.

[0054] Example 3

[0055] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0056] In step (2), 4.29 g (10 mmol) of Zr(NO3)4-5H2O was dissolved in 90 ml of DMF. Then, 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution, and the mixture was stirred at room temperature until the solid was completely dissolved. The mixture was transferred to a 200 ml reactor and reacted at 120 °C for 24 hours. After the reaction, the product was washed three times with DMF and centrifuged at 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0057] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0058] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.020 g of H-FCDs@FUIO were dissolved in 8 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (5 wt%). At 30 °C, the ionic conductivity was 9.8 × 10⁻⁶. -5 S / cm.

[0059] Example 4

[0060] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0061] In step (2), 2.33 g (10 mmol) of ZrCl4 was dissolved in 90 ml of DMF, and then 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution. The mixture was stirred at room temperature until the solid was completely dissolved. The mixed solution was transferred to a 200 ml reactor and reacted at 130 °C for 20 hours. After the reaction, the product was washed three times with DMF and centrifuged at a speed of 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0062] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0063] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.028 g of H-FCDs@FUIO were dissolved in 8 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (7 wt%). At 30 °C, the ionic conductivity was 3 × 10⁻⁶. -5 S / cm.

[0064] Example 5

[0065] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0066] In step (2), 4.29 g (10 mmol) of Zr(NO3)4-5H2O was dissolved in 90 ml of DMF. Then, 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution, and the mixture was stirred at room temperature until the solid was completely dissolved. The mixture was transferred to a 200 ml reactor and reacted at 120 °C for 24 hours. After the reaction, the product was washed three times with DMF and centrifuged at 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0067] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0068] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.036 g of H-FCDs@FUIO were dissolved in 8 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (9 wt%). At 30 °C, the ionic conductivity was 1.8 × 10⁻⁶. -5 S / cm.

[0069] Example 6

[0070] Step (1): 10 mL of pentafluorobenzaldehyde and 20 mL of acetaldehyde (40% aqueous solution) were stirred and slowly added to a solution of 6 g of sodium hydroxide dissolved in 5 mL of water (dissolved 15 min in advance), and stirred for 5 days. After that, the liquid portion was poured off, the solid residue was separated, diluted with 2 L of deionized water and transferred to a 1000 D dialysis bag for purification. After the pH of the dialysate reached 7, it was transferred to a freeze dryer for lyophilization to finally obtain the product H-FCDs.

[0071] In step (2), 4.29 g (10 mmol) of Zr(NO3)4-5H2O was dissolved in 90 ml of DMF. Then, 2.38 g (10 mmol) of tetrafluoroterephthalic acid and 12 ml of glacial acetic acid were added to the above solution, and the mixture was stirred at room temperature until the solid was completely dissolved. The mixture was transferred to a 200 ml reactor and reacted at 120 °C for 24 hours. After the reaction, the product was washed three times with DMF and centrifuged at 6000 r / min for 5 min each time. The product was then washed three times with methanol in the same manner. The precipitate was dried in a vacuum oven at 60 °C for 12 h to obtain the product FUIO.

[0072] In step (3), 0.375g of H-FCDs obtained in step (1) and 5g of FUIO obtained in step (2) were added to 40ml of methanol and stirred at room temperature for 12 hours. After the reaction was completed, the reaction product was separated by centrifugation and the precipitate was dried in a vacuum oven at 60℃ for 12 hours to obtain H-FCDs@FUIO.

[0073] In step (4), 0.4 g of PEO, 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide, and 0.044 g of H-FCDs@FUIO were dissolved in 9 ml of acetonitrile solution. After stirring at room temperature for 24 h, the solution was poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO / H-FCDs@FUIO (11 wt%). At 30 °C, the ionic conductivity was 1.77 × 10⁻⁶. -5 S / cm.

[0074] Example 7

[0075] The only difference from Example 3 is that the mass ratio of H-FCDs to FUIO is changed to 5:100; all other steps and conditions are the same. At 30°C, the ionic conductivity is 8.6 × 10⁻⁶. -5 S / cm.

[0076] Comparative Example 1

[0077] 0.4 g of PEO and 0.1467 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in 8 ml of acetonitrile solution and stirred at room temperature for 24 h. The mixture was then poured into a polytetrafluoroethylene mold, dried at room temperature for 6 h, and then vacuum dried at 60 °C for 12 h to obtain the composite polymer electrolyte, denoted as PEO. At 30 °C, the ionic conductivity was 7.4 × 10⁻⁶. -6 S / cm.

[0078] Comparative Example 2

[0079] The only difference from Example 3 is that FUIO was not prepared or added; all other steps and conditions were the same. At 30°C, the ionic conductivity was 3.8 × 10⁻⁶. -5 S / cm.

[0080] Comparative Example 3

[0081] The only difference from Example 3 is that an equal mass of UIO-66 (purchased from Adamas, trade number 013556384) was used instead of FUIO. All other steps and conditions remained the same, with an ionic conductivity of 5.1 × 10⁻⁶ at 30°C. -5 S / cm.

[0082] Figure 1 In the image, 'a' is a scanning electron microscope (SEM) image of FUIO prepared in Example 1, and 'b' is a scanning electron microscope (SEM) image of H-FCDs@FUIO prepared in Example 1. Figure 1 It can be seen that the size of the nanoparticles changed before and after being combined with H-FCDs, indicating that H-FCDs are combined with each other through fluoride-loving interactions, hydrogen bonds and coordination. At the same time, the nanoparticles still maintain an octahedral structure, and the good three-dimensional framework constrains the aggregation of quantum dots.

[0083] Figure 2 The graphs show the ionic conductivity of the fluorine quantum dot-combined FUIO molecular sieve composite solid electrolytes prepared in Examples 1-6 at different temperatures. As can be seen from the graphs, the conductivity increases with increasing temperature. Under the same conditions, the PEO / H-FCDs@FUIO (5wt%) electrolyte membrane exhibits the highest conductivity, reaching 9.8 × 10⁻⁶ at 30℃. -5 S / cm.

[0084] Figure 3Linear scanning voltammetry curves of two electrolyte membranes, H-FCDs@FUIO(5wt%) / PEO electrolyte and PEO electrolyte, show that the electrochemical window of H-FCDs@FUIO(5wt%) / PEO electrolyte has widened from 3.9V to 4.8V.

[0085] Figure 4 To construct Li||H-FCDs@FUIO(5wt%) / PEO electrolyte and Li||PEO||LFP full cells using two electrolyte membranes, H-FCDs@FUIO(5wt%) / PEO SPEs||LFP electrolyte and PEO electrolyte, cycle performance was tested at 1C and 80℃. The modified battery showed a capacity of 154 mAh / g and a coulombic efficiency close to 99%, significantly better than the pure PEO solid-state battery (138 mAh / g). Furthermore, after 300 cycles, the modified battery still retained 85.7% of its capacity (132 mAh / g), maintaining good efficiency. In contrast, the pure PEO solid-state battery's capacity decreased to 70 mAh / g after 300 cycles, a loss of nearly 50%.

Claims

1. A fluorine quantum dot-combined FUIO molecular sieve composite polymer solid electrolyte, characterized in that: Contains H-FCDs@FUIO, polyethylene oxide, and lithium salt; The H-FCDs@FUIO is formed by combining fluorine quantum dots and FUIO through fluorinative interactions, hydrogen bonds, and coordination; the FUIO is fluorinated UIO-66 molecular sieve.

2. The fluorine quantum dot-combined FUIO molecular sieve composite polymer solid electrolyte according to claim 1, characterized in that: The mass ratio of H-FCDs to FUIO in the H-FCDs@FUIO is (5~7.5):

100.

3. A fluorine quantum dot-combined FUIO molecular sieve composite polymer solid electrolyte according to claim 1 or 2, characterized in that: The FUIO has an octahedral crystal structure with an average pore size of 3.5~4 nm.

4. The fluorine quantum dot-combined FUIO molecular sieve composite polymer solid electrolyte according to claim 3, characterized in that: The preparation process of FUIO is as follows: zirconium salt and fluorine-containing organic ligand are subjected to a solvothermal reaction in the presence of organic solvent and regulator. Preferably, the zirconium salt includes at least one of zirconium nitrate and ZrCl4, the fluorinated organic ligand includes tetrafluoroterephthalic acid, the organic solvent includes DMF, the solution thermal reaction temperature is 120~140℃, the time is 20~48h, the molar ratio of the zirconium salt to the fluorinated organic ligand is (1~2):(1~2), and the regulator includes glacial acetic acid.

5. The fluorine quantum dot-combined FUIO molecular sieve composite polymer solid electrolyte according to claim 4, characterized in that: The mass ratio of H-FCDs@FUIO to polyethylene oxide is (1~11):100; The ratio of lithium salt to polyethylene oxide is 1:(10~20), calculated as the molar ratio of lithium ions in lithium salt to oxygen atoms in polyethylene oxide.

6. A method for preparing a solid electrolyte of fluorine quantum dots combined with FUIO molecular sieve composite polymer as described in any one of claims 1 to 5, characterized in that: After H-FCDs@FUIO, polyethylene oxide, lithium salt and solvent are mixed evenly, the mixture is then formed by injection molding and dried in sequence to obtain the final product.

7. The method for preparing the fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte according to claim 6, characterized in that: The preparation process of H-FCDs@FUIO is as follows: H-FCDs and FUIO are mixed and reacted in a solvent to obtain the product; The H-FCDs are obtained by condensation reaction of fluorinated aromatic aldehydes and α-H-containing aldehydes under alkaline conditions.

8. The method for preparing the fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte according to claim 7, characterized in that: The molar ratio of the fluorinated aromatic aldehyde and the α-H-containing aldehyde is (1~2):(2~3); The fluorinated aromatic aldehydes include pentafluorobenzaldehyde, and the α-H-containing aldehydes include acetaldehyde; The conditions for the condensation reaction are: temperature of 25~35℃ and time of 4~5 days.

9. The method for preparing a fluorine quantum dot combined with FUIO molecular sieve composite polymer solid electrolyte according to claim 7 or 8, characterized in that: The conditions for the mixing reaction are: temperature 25~30℃, time 12~24h.

10. The application of a solid electrolyte based on a fluorine quantum dot-combined FUIO molecular sieve composite polymer as described in any one of claims 1 to 5, characterized in that: It is used in the preparation of solid-state lithium metal batteries.

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