A fluorinated enhanced composite polymer electrolyte and a preparation method and application thereof

Abstract

The present invention relates to a fluorinated reinforced composite polymer electrolyte and a method of preparation and use thereof. The fluorinated reinforced composite polymer solid-state electrolyte comprises an organic polymer matrix, and a lithium salt and a fluorinated filler dispersed in the organic polymer matrix; the fluorinated filler comprises a metal fluoride dissolved in the organic polymer matrix.

Description

Technical Field

[0001] This invention relates to a dissolved fluorination-enhanced composite polymer electrolyte, its preparation method, and its application, belonging to the field of new energy technology. Background Technology

[0002] The pursuit of higher energy density and safety in batteries is of great significance for the development and practical application of electrochemical energy storage devices. Solid-state batteries are constructed by replacing traditional flammable liquid electrolytes with solid electrolytes that offer higher thermal stability. Solid-state lithium metal batteries, in particular, show promise for simultaneous upgrades in both energy density and safety when lithium metal is combined with a solid electrolyte. Solid electrolytes are a key component of solid-state batteries. Polymer solid electrolytes, represented by polyethylene oxide (PEO)-based electrolytes, have been extensively studied due to their ease of manufacture and flexibility. In PEO electrolytes, lithium ions are believed to migrate via vibrations in the -COC- segments, a behavior largely influenced by the degree of disorder in the microscopic regions of PEO. However, pure PEO electrolytes exhibit relatively poor lithium-ion conductivity, mechanical properties, and thermal stability. Adding functional fillers to polymers, and optimizing multi-scale interactions and conductive interfaces within the system, can construct composite polymer solid electrolytes, comprehensively improving their overall performance. To date, various fillers have been developed to enhance PEO-based polymer electrolytes, such as lithium-ion conductor fillers like LLZO and LATP. While these lithium-ion conductive fillers inherently contribute sufficiently high lithium-ion conductivity to composite electrolytes, the ceramic materials containing heavy metals in the system typically require complex fabrication processes to obtain customized nanostructures. Furthermore, the ceramic / polymer interface within the polymer can degrade due to potential side reactions or gravitational separation, significantly impacting the lithium-ion transport performance of the polymer electrolyte during long-term electrochemical operation. In fact, most filler reinforcement strategies aim to enhance their crosslinking effect with the PEO matrix while suppressing TFSI in the polymer system. - Anion movement increases the lithium-ion transference number (t). Li+ However, the deep crosslinking mechanism between the filler and PEO and the associated physical scenario of charge transport remain unclear. The strong interactions between acidic oxides (e.g., Al₂O₃) or metal-organic framework (MOF) type fillers and PEO and its lithium salts have long been attributed to surface Lewis acid-base reactions. However, efficient research on improving the overall performance of polymer electrolytes by modulating the Lewis acid-base mechanism within the polymer is still lacking.

[0003] Fluorides play a crucial role in non-aqueous electrolyte systems due to their excellent effect on suppressing lithium anode dendrite formation and improving cathode operating voltage. Although fluorination strategies have shown some positive effects on electrolyte conductivity, cathode and anode stability in both liquid and solid electrolyte systems, homogenization and global dispersion of fluorinated components remain a significant challenge for PEO-based polymer electrolytes.

[0004] Furthermore, when a conversion-reactive fluoride cathode is matched with metallic lithium, the battery can theoretically provide an energy density of up to 850 Wh / kg. However, this battery system typically suffers from the deactivation and dissolution of cathode conversion products, leading to problems such as fluoride (F) loss and rapid capacity decline. The architecture of solid-state lithium / fluoride batteries can enhance the volume compaction effect of conversion products and suppress their extrusion (or dissolution) into the electrolyte. Based on this consideration, the inventors recently successfully realized a ceramic-based solid-state Li||FeF3 battery with significantly improved cycle reversibility (Energy Storage Mater., 47, 551-560, 2022; ACSEnergy Lett., 5, 1167-1176, 2020.). However, higher capacity release and better cycle durability still require a softer cathode interface contact to replace the hard ceramic interface contact. Therefore, we constructed an enhanced composite polymer electrolyte by stacking g-C3N4 polymer microspheres with better mechanical strength in a soft PEO matrix, and based on this, we built a solid-state Li||FeF3 battery. Thanks to the softening of the cathode interface, the conversion-reaction solid-state Li||FeF3 battery achieved a significant improvement in cycle stability, providing a new avenue for its practical application. However, in this system, due to phase separation between g-C3N4 and PEO within the polymer, the negative effects caused by component heterogeneity remain significant in the electrolyte, leading to potential coarsening of the polymer electrolyte film (especially after repeated cycling). In the Li||FeF3 battery system, driven by the F concentration gradient and trapped by heterogeneous grain boundaries, F-containing active materials readily and irreversibly migrate into the electrolyte, resulting in capacity decay, a phenomenon particularly pronounced during early cycling. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a fluorinated reinforced composite polymer solid electrolyte membrane, its preparation method, and its application.

[0006] In a first aspect, the present invention provides a fluorinated reinforced composite polymer solid electrolyte, comprising: an organic polymer matrix, and a lithium salt and a fluorinated filler dispersed in the organic polymer matrix; wherein the fluorinated filler comprises a metal fluoride dissolved in the organic polymer matrix.

[0007] Preferably, the fluorinated filler comprises porous metal fluoride nanoparticles and metal fluorides dissolved in an organic polymer matrix.

[0008] Preferably, the metal fluoride dissolved in the organic polymer matrix is ​​obtained by dissolving porous metal fluoride nanoparticles.

[0009] In this disclosure, porous metal fluoride nanoparticles are used as filler materials for polymer electrolytes to prepare fluorinated composite solid electrolyte membranes. The porous metal fluoride nanoparticles (nanostructures) with high specific surface area and strong Lewis acidity are wholly or mostly dissolved in the polymer system, no longer retaining their particulate structure (i.e., metal fluoride dissolved in the organic polymer matrix), achieving sufficient homogeneous fluorination enhancement of the polymer electrolyte system. Due to the strong interaction between the high specific surface area porous metal fluoride and the polymer and lithium salt, the conductivity of the composite polymer electrolyte is significantly improved. The porous metal fluoride also promotes the dissociation of anions in the polymer system, increasing the lithium-ion transference number of the polymer electrolyte. The interface between the fluorinated composite polymer electrolyte and lithium metal is extremely stable, and the composition of the SEI (solid electrolyte interphase) on the lithium metal surface can be adjusted to reduce interface passivation. The lithium metal symmetric battery based on the fluorinated composite polymer electrolyte exhibits very low interfacial resistance and overpotential during long-term aging and cycling. Based on this fluorinated reinforced composite polymer solid electrolyte, the conversion-type solid-state lithium / fluoride battery can provide an additional F source at the fluorinated cathode interface to compensate for the F loss of the fluoride cathode during the conversion reaction, thereby achieving better conversion reaction reversibility.

[0010] Preferably, the organic polymer includes at least one of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP.

[0011] The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiFSI), lithium hexafluorophosphate (LiPF6), and lithium perchlorate (LiClO4).

[0012] Preferably, when the fluorinated filler contains only metal fluorides dissolved in the organic polymer matrix, the mass percentage of the fluorinated filler in the fluorinated reinforced composite polymer solid electrolyte is 5 wt% to 30 wt%, preferably 5 wt% to 15 wt%.

[0013] Preferably, when the fluorinated filler comprises porous metal fluoride nanoparticles and metal fluoride dissolved in the organic polymer matrix, the mass percentage of the fluorinated filler in the fluorinated reinforced composite polymer solid electrolyte is 5 wt% to 30 wt%, preferably 15 to 30 wt%; and the mass of the porous metal fluoride nanoparticles does not exceed 50 wt% of the total mass of the metal fluoride dissolved in the organic polymer matrix and the porous metal fluoride nanoparticles, preferably not exceeding 20 wt% of the total mass of the metal fluoride dissolved in the organic polymer matrix and the porous metal fluoride nanoparticles.

[0014] Preferably, the porous metal fluoride nanoparticles include at least one of nanoporous aluminum fluoride AlF3, nanoporous magnesium fluoride MgF2, nanoporous cerium fluoride CeF3, and nanoporous oxygen-doped zirconium fluoride O-ZrF4; the metal fluoride is at least one of AlF3, MgF2, CeF3, and O-ZrF4.

[0015] Furthermore, preferably, the porous metal fluoride nanoparticles have a mesoporous structure with a mesoporous pore size of 4–60 nm.

[0016] Furthermore, preferably, the porous metal fluoride nanoparticles have a particle size of 10–100 nm and a specific surface area of ​​45–300 m². 2 / g.

[0017] Preferably, the molar mass of the organic polymer is calculated based on the molar mass of the polymeric monomers used to form the organic polymer, and the molar ratio of the organic polymer to the lithium salt is (10-20):1; preferably, the monomer of the polyethylene oxide is ethylene oxide C2H4O monomer, and the polyethylene oxide:lithium salt = ethylene oxide C2H4O monomer:lithium salt = (10-20):1.

[0018] Preferably, the thickness of the fluorinated reinforced composite solid electrolyte is 25–200 μm.

[0019] Secondly, the present invention provides a method for preparing a fluorinated reinforced composite polymer electrolyte, comprising:

[0020] (1) Organic polymer, lithium salt and porous metal fluoride nanoparticles are added to an organic solvent and mixed to obtain a mixed slurry;

[0021] (2) The obtained mixed slurry is cast onto a substrate to form a composite polymer film precursor;

[0022] (3) The substrate coated with the composite polymer film precursor is heated to 40-80°C under vacuum and kept at that temperature for at least 24 hours, and then air-cooled to room temperature to obtain the fluorinated reinforced composite polymer electrolyte.

[0023] In this disclosure, polymer, lithium salt, and high-specific-surface-area porous metal fluoride powders are mixed and dissolved in an organic solvent, then formed into a film and dried in a polytetrafluoroethylene mold to obtain a fluorinated reinforced composite polymer solid electrolyte membrane. The porous metal fluoride can be partially dissolved in the polymer system. Moreover, when the high-specific-surface-area porous metal fluoride is mixed with the polymer electrolyte, thanks to the partial dissolution-fluorination process, the metal fluoride interacts strongly with the polymer and lithium salt, ensuring the mechanical properties and thickness control of the final fluorinated reinforced polymer solid electrolyte membrane.

[0024] Preferably, the method for synthesizing the porous metal fluoride nanoparticles includes:

[0025] (1) Add the hydrated nitrate of the metal corresponding to the metal element in the porous metal fluoride and polyethylene glycol (PEG) to the ethylene glycol solution and stir at 40-60°C for 4-8 hours to obtain a transparent solution.

[0026] (2) Then add hydrofluoric acid aqueous solution dropwise to the transparent solution to obtain a wet sol of fluoride; preferably, the mass fraction of hydrofluoric acid aqueous solution is 40%;

[0027] (3) The wet sol of fluoride is aged at 25-90°C for 12-24 hours to obtain the wet gel of fluoride;

[0028] (4) The wet gel of fluoride is aged at 120-150°C for 12-24 hours to obtain dry gel powder of metal fluoride.

[0029] (5) The obtained dry gel powder of metal fluoride is calcined in air at 350-450°C for 3-5 hours to obtain the porous metal fluoride nanoparticles.

[0030] Preferably, in step (1), the organic solvent is one of acetonitrile (CAN), dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

[0031] Preferably, in step (1), the mixing method is stirring, which is stirring at room temperature to 60°C for 4 to 8 hours.

[0032] Preferably, in step (1), the porous metal fluoride nanoparticles account for 5 wt% to 30 wt% of the total mass of the organic polymer, lithium salt, and porous metal fluoride nanoparticles. In this case, the content of porous metal fluoride nanoparticles takes into account the portion dissolved in the organic polymer, which is actually the total amount of all fluorinated fillers added.

[0033] Preferably, in step (2), the substrate is a polytetrafluoroethylene plastic sheet.

[0034] Thirdly, this invention provides a lithium metal symmetric battery system based on a solid-state electrolyte. The lithium metal symmetric battery system includes the aforementioned fluorinated reinforced composite polymer solid-state electrolyte and lithium metal sheets located on both sides of the fluorinated reinforced composite polymer solid-state electrolyte. When the fluorinated reinforced composite polymer solid-state electrolyte is used in a lithium metal symmetric battery, it exhibits good interfacial stability and extremely low interfacial impedance, which can significantly reduce the voltage polarization difference during lithium metal deposition / stripping, enhance the cycle stability of the symmetric battery, and ensure that the lithium metal surface remains smooth and dense even after long-term cycling.

[0035] Fourthly, the present invention provides a lithium metal battery based on a fluorinated reinforced composite polymer solid electrolyte, the solid lithium metal battery comprising a positive electrode, a negative electrode, and a fluorinated reinforced composite polymer solid electrolyte located between the positive electrode and the negative electrode.

[0036] Preferably, the negative electrode is a lithium metal sheet.

[0037] Preferably, the positive electrode is at least one selected from FeF3, FeF2, iron-oxygen fluoride compounds, CuF2, CuOHF, carbon-sulfur complexes, FeS2, LiMn2O4, LiFePO4, LiCoO2, nickel-rich ternary systems, and lithium-rich manganese-based solid solutions. FeF3 is the most preferred positive electrode. When the fluorinated polymer solid electrolyte is used in a Li||FeF3 lithium metal battery, the reversibility and cycle stability of the iron fluoride conversion reaction positive electrode are greatly enhanced due to the replenishment of fluorine source at the positive electrode fluorination interface and the morphological stability of the lithium negative electrode. This results in a reversible capacity of up to 650 mAh / g and a long battery life of more than 900 cycles.

[0038] Fifthly, the present invention provides a solid lithium / fluoride battery with a pouch configuration based on a fluorinated reinforced composite polymer solid electrolyte, the pouch battery comprising a positive electrode, a negative electrode, and a fluorinated reinforced composite polymer solid electrolyte located between the positive electrode and the negative electrode.

[0039] Preferably, the negative electrode is a thin-film lithium metal (lithium metal film, preferably with a thickness of 45 to 100 micrometers), and the positive electrode is at least one of FeF3, FeF2, ferrofluorine compound, CuF2, and CuOHF.

[0040] Preferably, the positive electrode contains 3-15 wt% of a metal fluoride; the metal fluoride is at least one selected from AlF3, MgF2, CeF3, and O-ZrF4. During the preparation of the positive electrode film, a small amount (3-15%) of porous metal fluoride corresponding to the fluorinated filler in the electrolyte film is added to the positive electrode mixture as a positive electrode enhancer to construct an integrated soft-pack solid-state fluorine-based lithium metal battery. The high specific surface area porous metal additive in the positive electrode film can firstly improve the positive electrode reaction kinetics. Secondly, the porous metal fluoride in the positive electrode can compensate for F loss during interfacial cycling, thereby improving the cycle reversibility of the conversion reaction-type fluoride positive electrode. Finally, this fluorinated additive in the positive electrode network is expected to improve the interfacial compatibility and integrated connection between the fluorinated electrolyte and the fluorinated positive electrode.

[0041] Preferably, the positive electrode of the integrated fluorine-based solid-state pouch battery is FeF3. By adding 8% of porous nanostructured AlF3 during the preparation of the positive electrode film, the capacity and cycle stability of the integrated fluorine-based solid-state pouch battery with lithium negative electrode-fluorinated polymer electrolyte-iron fluoride positive electrode are significantly improved.

[0042] The present invention has the following positive and progressive effects.

[0043] (1) This invention uses porous metal fluorides as fillers in polymer electrolytes to prepare fluorinated reinforced composite polymer solid electrolytes. Compared with traditional polymer electrolytes modified with coarse-particle fillers, this fluorinated polymer electrolyte exhibits significant advantages. First, the ultrafine metal fluorides with high specific surface area nanostructures undergo a thorough cross-linking reaction with the polymer matrix. This strong interaction effectively ensures the mechanical properties of the electrolyte membrane during the thinning process, enabling the ultrathin manufacturing of composite polymer membranes (down to 25 micrometers). On the other hand, the ultrafine porous metal fluorides can partially dissolve in the polymer system, allowing the filler concentration to increase within a certain range without performance degradation of the electrolyte membrane. The resulting special wrinkled morphology on the surface of the composite polymer membrane helps the polymer membrane resist tearing and maintain high integrity and stability, especially during the polymer membrane forming and thinning process.

[0044] (2) In this invention, the porous metal fluoride can interact strongly with the polymer matrix and lithium salt, forming abundant high-speed lithium conduction channels at the interface between the polymer and the porous metal fluoride. The resulting composite polymer electrolyte has a conductivity as high as 10 at 30°C. -4 ~10 -5The S / cm ratio is at least one order of magnitude higher than that of pure polymer electrolyte systems. Due to the strong dissociation effect of porous metal fluorides on lithium salts and their strong adsorption effect on anions, the lithium-ion transference number of the composite polymer is as high as 0.69. The high conductivity and high transference number can effectively ensure the reduction of polarization of the composite electrolyte membrane during solid-state electrolytic cell cycling, thereby improving the cycle stability of the battery.

[0045] (3) The fluorinated reinforced composite polymer solid electrolyte of this invention exhibits excellent stability and extremely low interfacial impedance at the interface with lithium metal. The single-interface resistance of the polyoxyethylene fluorinated polymer electrolyte at the lithium metal interface is as low as 10 Ω·cm. 2 Furthermore, it can remain stable at this value for up to 20 days. In comparison, the interfacial impedance of the corresponding non-fluorinated electrolyte membrane in contact with metallic lithium decreases from 10.5 Ω·cm within 14 days. 2 Increased to 22.5 Ω·cm 2 When fluorinated electrolytes are used in lithium metal symmetric batteries, the fluorination at the interface facilitates the enrichment of high ionic conductivity components (such as Li₂O), the suppression of interfacial passivation components (such as Li₂CO₃), and the control of lithium dendrite growth. This significantly reduces the polarization potential difference during the reversible deposition / stripping of lithium metal and enhances the cycle stability of the symmetric battery. Correspondingly, the surface morphology of lithium metal in solid-state lithium metal batteries remains dense after 300 hours of cycling.

[0046] (4) When the fluorinated composite polymer electrolyte of the present invention is used in a solid lithium / fluoride metal battery, the fluorinated cathode interface formed can better compensate for the F loss of the fluoride cathode during cycling, and greatly enhance the reversibility of the conversion reaction and the cycling stability of the fluoride cathode.

[0047] (5) This invention demonstrates for the first time a large-size fluorine-based solid-state pouch cell with a conversion reaction and its successful operation. The pouch cell based on a fluorinated enhanced composite polymer electrolyte exhibits high capacity (~600 mAh / g) and long cycle stability (greater than 900 cycles). This large-size, thin-layer, all-solid-state lithium iron fluoride conversion pouch cell can effectively promote the future practical application of fluorine-based battery systems. Attached Figure Description

[0048] Figure 1 The image shows the XRD pattern of porous AlF3 synthesized by the sol-gel method.

[0049] Figure 2 SEM image of nanoporous AlF3;

[0050] Figure 3Photographs of the process for preparing a polymer membrane with nanoporous AlF3 composite: including photos of AlF3 powder, LiTFSI and PEO mixed in acetonitrile solvent, AlF3 fluorinated reinforced composite polymer membrane, and photos showing the composite polymer membrane thickness of 45 μm;

[0051] Figure 4 The morphology of the composite polymer electrolyte reinforced with nanoporous AlF3;

[0052] Figure 5 The conductivity variation of composite polymer electrolytes reinforced with different contents (0%, 5%, 10%, 20% or 30%) of nanoporous AlF3 filler at different test temperatures (30-70℃);

[0053] Figure 6 The interfacial AC impedance spectrum of a lithium metal symmetric battery based on a high specific surface area nanoporous AlF3 fluorination-enhanced composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) as a function of time.

[0054] Figure 7 The interfacial AC impedance spectrum shows the time evolution of a lithium metal symmetric battery based on pure polymer electrolyte (LiTFSI-PEO).

[0055] Figure 8 To achieve a lithium metal symmetric battery at 0.1 mA / cm², a composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) based on high specific surface area nanoporous AlF3 was developed. 2 Potential curves of lithium metal deposition / stripping cycles, with an inset showing magnified potential curves at specific cycle stages;

[0056] Figure 9 The image shows the potential curves of lithium metal symmetric batteries based on high specific surface area nanoporous AlF3 composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) under different current densities during lithium metal deposition / stripping cycles. Insert: Comparison of magnified potential curves at specific cycling stages.

[0057] Figure 10 To achieve a lithium metal symmetric battery at 0.1 mA / cm², a composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) based on high specific surface area nanoporous AlF3 was developed. 2 SEM images of lithium metal deposition after 300 hours of deposition / stripping under the specified conditions;

[0058] Figure 11The charge-discharge curves of a solid-state Li||FeF3 battery based on a high specific surface area nanoporous AlF3 composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) at different electrochemical cycling stages are shown in the figure at a current density of 700 mA / g and a voltage range of 1.2-3.9 V.

[0059] Figure 12 This image shows the cycle performance of a solid-state lithium / iron fluoride pouch cell based on a high specific surface area nanoporous AlF3 composite polymer solid electrolyte. Left inset: Charge-discharge curves for different cycle stages; Right inset: Image of the pouch cell.

[0060] Figure 13 The graph shows the cycling performance of a pouch-type solid-state lithium / iron fluoride battery with a cathode enhanced by a composite polymer solid electrolyte (LiTFSI-PEO-0.2AlF3) based on high specific surface area nanoporous AlF3. 8 wt% of nanoporous AlF3 is introduced into the cathode film to enhance the cathode. Left inset: Charge-discharge curves at different cycling stages; Right inset: Actual image of the pouch-type battery.

[0061] Figure 14 To develop a lithium metal symmetric battery based on a high specific surface area nanoporous MgF2 composite polymer solid electrolyte (LiTFSI-PEO-0.2MgF2) at 0.1 mA / cm², 2 Potential curves of lithium metal deposition / stripping cycles;

[0062] Figure 15 The charge-discharge curves of a solid-state Li||FeF3 battery based on a high specific surface area nanoporous MgF2 composite polymer solid electrolyte (LiTFSI-PEO-0.2MgF2) at different electrochemical cycling stages are shown in the figure at a current density of 525 mA / g and a voltage range of 1.2-3.9 V.

[0063] Figure 16 This is a comparison of the discharge capacity of solid-state Li||FeF3 batteries after the first 300 cycles, based on a 20 wt% nanoporous AlF3 fluorinated reinforced composite polymer electrolyte and a 20 wt% commercial AlF3-filled composite polymer electrolyte. The voltage range is 1.2–3.9 V, and the current densities are 358 mAh / g (mesoporous aluminum fluoride) and 200 mAh / g (commercial aluminum fluoride), respectively.

[0064] Figure 17 Charge-discharge curves of a solid-state Li||FeF3 battery at different electrochemical cycling stages, based on a 20 wt% nanoporous AlF3 fluorinated reinforced composite polymer electrolyte and a 20 wt% commercial AlF3-filled composite polymer electrolyte. Detailed Implementation

[0065] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0066] This invention uses porous metal fluorides as fillers in polymer electrolytes to prepare fluorinated composite solid electrolyte membranes. The porous metal fluorides, with their high specific surface area and strong Lewis acidity, can partially dissolve in the polymer system, achieving thorough homogeneous fluorination reinforcement of the polymer electrolyte system. Specifically, porous metal fluorides are first prepared, then the fluoride powder is mixed with lithium salt and polymer in an organic solvent to form a polymer precursor slurry. Finally, the uniformly stirred slurry is cast into a polytetrafluoroethylene (PTFE) mold, and the organic solvent is completely evaporated in a vacuum environment to obtain the fluorinated polymer electrolyte membrane. The mass ratio of the porous metal fluoride in the fluorinated composite solid electrolyte membrane is 5 wt% to 30 wt%.

[0067] The aforementioned porous metal fluorides include AlF3 with a high specific surface area nanoporous structure, MgF2 with a high specific surface area nanoporous structure, ZrF4 with a high specific surface area nanoporous structure, and CeF3 with a high specific surface area nanoporous structure.

[0068] The fluorinated reinforced composite polymer solid electrolyte of this invention is composed of a porous metal fluoride-filled pure polymer electrolyte. The porous metal fluoride composite polymer electrolyte comprises a polymer matrix, a lithium salt, and the porous metal fluoride. The polymer can be at least one of polyethylene oxide (PEO), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP. The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), and lithium perchlorate (LiClO4). The polymer and lithium salt are preferably polyethylene oxide (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), respectively. The molar ratio of ethylene oxide monomer [EO] to lithium salt is in the range of (10–20):1.

[0069] The following exemplarily illustrates the preparation method of the fluorinated reinforced composite polymer solid electrolyte provided by the present invention.

[0070] Fluorinated composite polymer solid electrolyte membranes are prepared by solution casting using porous metal fluorides as polymer electrolyte fillers. The porous metal fluoride is preferably high specific surface area nanoporous AlF3, with a pore size ranging from 2 to 15 nm and a specific surface area of ​​188 m². 2 / g. As an example, first mix 360mg LiTFSI and 880mg PEO powder (where [EO]:Li + A fluorinated precursor slurry (with a ratio ranging from 10 to 20) is added to 20 mL of acetonitrile solution. Then, 65–531 mg of high specific surface area AlF3 powder is added to the solution. The mixture is stirred at room temperature for at least 12 hours to obtain a reddish-brown precursor slurry. The slurry is then cast onto a polytetrafluoroethylene (PTFE) plate and evaporated at room temperature. Finally, the electrolyte membrane is peeled off from the PTFE mold and vacuum dried at 60°C for 12 hours for later use. The thickness of the fluorinated reinforced composite polymer solid electrolyte membrane can be adjusted as needed by adjusting the slurry volume and the mold area; its thickness is generally 25–200 micrometers.

[0071] The solid-state lithium metal symmetric battery system provided by this invention is a battery in which both sides are lithium metal sheets. The current density for lithium deposition and stripping cycle tests of the lithium metal symmetric battery system can be 0.1–1.2 mA / cm². 2 The deposition or stripping time in each cycle can be 0.5 to 1 hour.

[0072] The solid-state lithium metal battery provided by this invention uses a lithium metal sheet as the negative electrode, and the positive electrode can be at least one of FeF3, FeF2, CuF2, CuOHF, carbon-sulfur composites, FeS2, LiMn2O4, LiFePO4, LiCoO2, nickel-rich ternary systems, and lithium-rich manganese-based solid solutions. A fluorinated reinforced composite polymer electrolyte is placed between the positive and negative electrodes.

[0073] This invention provides a large-size fluorine-based solid-state pouch battery based on a fluorinated reinforced composite solid-state polymer electrolyte. The negative electrode uses a thin-layer lithium strip (45 micrometers thick), and the positive electrode film contains a fluoride positive electrode (active material), a small amount of conductive carbon, a polymer, and a lithium salt. The fluorinated reinforced composite polymer electrolyte is located between the positive and negative electrodes. As a preferred example, during the preparation of the positive electrode film, a small amount (3-15 wt%) of porous metal fluoride is added to the positive electrode mixture as a reinforcing agent to construct an integrated solid-state fluorine-based lithium metal pouch battery. The high specific surface area porous metal fluoride additive in the positive electrode film effectively improves the positive electrode reaction kinetics, enhances the F compensation capability of the fluorination interface, and improves the cycle reversibility of the conversion reaction fluoride positive electrode.

[0074] In this invention, a fluorinated composite solid electrolyte membrane was obtained by using porous metal fluorides as fillers for the polymer electrolyte. The mesoporous metal fluoride nanoparticles, possessing high specific surface area and strong Lewis acidity, can partially dissolve in the polymer system, fluorinate the polymer matrix, and interact strongly with the polymer, thereby improving the lithium-ion conductivity of the composite polymer. The porous metal fluorides also promote the dissociation of lithium salts and the movement of anions after dissociation, increasing the lithium-ion transference number of the composite (up to 0.67). Contact between the fluorinated polymer and lithium can induce the enrichment of highly conductive Li₂O components at the interface, making this material the main SEI component on the cycling lithium metal anode to mitigate interface passivation. The optimized solid-state lithium symmetric battery exhibited considerably low interfacial resistance and overpotential during long-term aging and cycling. The solid-state lithium / fluoride battery based on the fluorinated electrolyte achieves better conversion reversibility because the fluorinated interface can provide additional F resources to compensate for F losses in the conversion reaction process of the fluoride cathode. All-solid-state lithium / iron fluoride batteries can achieve reversible capacity of up to ~600 mAh / g and enable larger pouch cell configurations based on a thin electrolyte membrane (45 μm).

[0075] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0076] Example 1

[0077] 1) Preparation of high specific surface area nanoporous aluminum fluoride

[0078] This example demonstrates the synthesis of HS-AlF3 via the sol-gel method. Typically, 18.76 g of aluminum nitrate nonahydrate (Al(NO)3·9H2O) is first added to 50 mL of ethylene glycol, and the Al... 3+The concentration was controlled at 1 mol / L. The mixture was stirred at 50°C until it became a transparent and homogeneous solution. Then, 6.7 mL of hydrofluoric acid (40% by mass) was added to the solution, and stirring was continued for another 6 hours. Next, the transparent solution was aged at 90°C for 24 hours, and then at 120°C for 24 hours. After thorough drying, the wet aluminum fluoride gel transformed into a light yellow dry gel. Finally, the dry gel was placed in an open ceramic crucible and calcined in a muffle furnace at 400°C for 4 hours at a heating rate of 2°C / min. The final aluminum fluoride sample was a light brown, fluffy powder with abundant organic components containing carbon, nitrogen, and oxygen on the particle surface. The XRD pattern of the obtained aluminum fluoride is shown below. Figure 1 As shown, this fluorinated sol-gel synthesis route leads to preferential orientation and crystallization of aluminum fluoride particles along the (012) / (024) crystal plane. Due to the gradual loss of the thick organic layer in the AlF3 dry gel during air sintering, the growth of AlF3 nanocrystals is limited, while more effective Lewis acid sites in the solid acid are exposed, which facilitates better interaction with the PEO-based electrolyte components. SEM shows that the aluminum fluoride powder has a mesoporous morphology (mesoporous pores are approximately 4-26 nm, with a particle size of 50-80 nm) due to the ordered aggregation of fine nanorods. Figure 2 As shown. The specific surface area of ​​the obtained aluminum fluoride powder is 188 m². 2 / g.

[0079] 2) Preparation of fluorinated reinforced composite polymer solid electrolyte

[0080] Fluorinated reinforced composite solid polymer films were prepared via a solution casting process. First, 360 mg of LiTFSI and 880 mg of PEO powder (where [EO]:Li) were added. + The ratio of AlF3 to AlF3 was 16:1, and the solution was then added to 20 mL of acetonitrile. High specific surface area AlF3 powder with different weight ratios (in this example, 5% (completely soluble), 10% (completely soluble), 20% (not completely soluble), and 30% (not completely soluble), corresponding to 65 mg, 138 mg, 310 mg, and 531 mg respectively) was added to the solution. The mixture was stirred at room temperature for at least 12 hours to obtain a reddish-brown slurry solution (see...). Figure 3 (This corresponds to an amount of 20% AlF3, at which point the AlF3 is not completely dissolved). The solution is then cast onto a PTFE plate and evaporated at room temperature. Finally, the electrolyte membrane is peeled off from the PTFE mold and vacuum-dried at 60°C for 12 hours before use. In the polymer system, the porous fluoride can dissolve in most of its components (corresponding to an amount of 20% AlF3, at which point the AlF3 is not completely dissolved). Due to the strong interaction between the fluoride and the polymer, the composite polymer can be easily manufactured in ultra-thin layers (25–45 micrometers thick), such as... Figure 3 As shown, the surface of the high specific surface area AlF3-enhanced electrolyte exhibits a unique corrugated morphology with uniformly distributed wrinkled protrusions, the thickness of which is less than 50 nm. This unique surface texture (as shown) Figure 4 The results (shown) can be attributed to the dissolution of AlF3 in the polymer system, as well as the sufficient contact and strong cross-linking effect between it and LiTFSI-PEO.

[0081] 3) Testing the conductivity of fluorinated polymers

[0082] The ionic conductivity of a fluorinated reinforced composite polymer solid electrolyte was tested using a Solartron frequency analyzer (1296-1260) with a Swagelok battery (SS|LiTSFI-PEO-AlF3|SS, where SS is stainless steel) with a dual-electrode structure. In open-circuit constant potential mode, a 10mV AC voltage perturbation was used, with a test frequency range of 10MHz to 0.1Hz, and 10 data points were collected every 10 octaves. A 10mm diameter sheet of solid polymer film was fabricated, and two stainless steel sheets were placed on either side of the electrolyte film as ion-blocking electrodes. Variable-temperature lithium-ion conductivity testing was conducted at 70-30℃, with the battery placed in an oven and the temperature controlled in 10℃ increments. The battery was held at each temperature for 1 hour to allow it to reach a stable state. The conductivity (ρ) of the solid polymer electrolyte was calculated using the following formula:

[0083]

[0084] Where R is the resistance value, L is the film thickness, and S is the contact area of ​​the electrode. Figure 5 The AlF3-enhanced composite electrolyte LiTFSI-PEO-0.2AlF3 with a content of 20% showed the highest conductivity, which was 4.63 × 10⁻⁶ at 30 °C. -5 S / cm increased to 2.78 × 10⁻⁶ at 60 °C. -4 S / cm. The high proportion of exposed crosslinkable sites in this high specific surface area AlF3 fluorinated filler delays the saturation of the fluorinated interface and PEO amorphous domains, which is the reason for this high content and optimal filling fluorination.

[0085] 4) Assembly and testing of solid-state lithium metal symmetric batteries

[0086] The 2025 button cell assembly was conducted in an argon-filled glove box with water and oxygen levels below 0.1 ppm. Specifically, 10 mm diameter lithium metal sheets were laid on both sides of a 16 mm diameter fluorinated composite solid electrolyte to assemble a button cell. For comparison, a similar symmetrical cell based on a pure polymer electrolyte was assembled. AC impedance testing of the symmetrical cell was performed at room temperature, with a bias voltage of 100 mV and a frequency range of 10 MHz to 0.1 Hz, collecting 10 data points every 10 harmonics. To test the evolution of the interfacial impedance between lithium metal and the fluorinated polymer solid electrolyte over time, tests were performed every 24 hours until the impedance value showed no significant fluctuation. Figure 6 The change in interfacial impedance between lithium metal and the fluorinated solid electrolyte over time is shown. It can be seen that the interfacial impedance value on the first day is 10 Ωcm. 2 Due to the stability of the interface, this impedance value can be maintained stably for at least 20 days. In contrast, the interfacial impedance of the corresponding pure electrolyte (LiTFSI-PEO) membrane in contact with lithium metal decreases from 10.5 Ω·cm within 14 days. 2 Increased to 22.5 Ω·cm 2 ,like Figure 7 As shown.

[0087] The assembled 2025 coin cell symmetric battery was charged and discharged on a LAND electrochemical workstation at 0.1 mA / cm². 2 At a given current density, the lithium metal is first charged at a constant current for 1 hour (or 0.5 hours), and then discharged at a constant current for 1 hour (or 0.5 hours). The voltage polarization difference of lithium metal during deposition / stripping is detected, and this cycle is repeated. Figure 8 For solid-state lithium metal symmetric cells based on LiTFSI-PEO-0.2AlF3 fluorinated solid electrolyte at 0.1 mA / cm 2 The figure shows the cycling curves of the lithium metal deposition / stripping process at a given current density. As can be seen from the figure, at this current density, a stable deposition / stripping process can last for at least 1200 hours, with a single-sided overpotential as low as 25 mV, which is only half that of most traditional filler-reinforced polymer systems. Figure 9 This image shows a comparison of cycling curves for lithium metal deposition / stripping processes at different current densities in symmetric batteries based on fluorinated solid electrolytes and pure electrolyte systems. (At 0.4 mA / cm²) 2 At higher current densities, the voltage polarization of the symmetric cell based on the fluorinated solid electrolyte LiTFSI-PEO-0.2AlF3 is only half that of the pure electrolyte LiTFSI-PEO system. At even higher current densities (1.2 mA / cm²), the voltage polarization is significantly higher. 2Under these conditions, the fluorinated modified battery could still operate stably for more than 100 hours with an overpotential of less than 300mV, while the LiTFSI-PEO-based battery could not operate and experienced a severe short circuit. After a certain number of cycles, the symmetrical battery was disassembled in an argon-filled glove box, the lithium metal sheet was removed, and its morphology was observed under argon protection using a scanning electron microscope. Figure 10 0.1 mA / cm 2 The morphology of the lithium metal surface of the fluorinated solid-state symmetric battery after 300 hours of cycling at the current density is shown in the figure. As can be seen from the figure, even after long-term cycling, the surface of the negative electrode is still generally dense and smooth. Although some granular lithium regions appear, these lithium particles are densely deposited and do not produce porous structures or lithium dendrites.

[0088] 5) Preparation and testing of lithium metal batteries based on fluorinated reinforced composite polymer electrolytes:

[0089] 5)a) Preparation of solid-state cathode:

[0090] To prepare the positive electrode for all-solid-state batteries, LiTFSI-PEO was introduced as an ion-conducting conductor. In this work, the positive electrode for coin cells can include LiFePO4, fluoride positive electrodes, nickel-rich ternary systems, etc. In this example, FeF3 positive electrode is described as a preferred candidate. The FeF3 sample was synthesized based on our previously developed ionic liquid thermal fluorination method. In the preparation of the positive electrode, the active material was mixed with conductive carbon black (Super P), polyethylene oxide (PEO), and LiTFSI salt in a weight ratio of 60:12:20:8, and then 12 mL of acetonitrile was added to form a homogeneous mixture. The mixture was stirred at room temperature for 12 hours and then cast onto carbon-coated aluminum foil. The FeF3 loading was 1–4.2 mg / cm³. 2 .

[0091] 5)b) Assembly and testing of solid-state lithium / iron fluoride batteries based on fluorinated reinforced composite polymer electrolytes:

[0092] The 2032 button cell was assembled in an argon-filled glove box with a water and oxygen concentration of less than 0.1 ppm. Specifically, a 10 mm diameter lithium metal sheet and a positive electrode containing active material were attached to both sides of a 16 mm diameter polymer film to assemble the lithium metal battery. The battery's electrochemical cycle performance was then tested at 60°C and different current densities using a LAND electrochemical workstation. The Li||FeF3 battery was tested in the voltage range of 1.2–3.9 V and at a current density of 700 mA / g (~1 C; the theoretical specific capacity of the FeF3 positive electrode based on the three-electron transfer reaction is 712 mAh / g). Figure 11The image shows a typical charge-discharge curve for the Li||FeF3 battery during the first 300 cycles, with an initial discharge capacity as high as 575 mA / g. The discharge curve exhibits typical two-stage characteristics, fully showcasing the plateau feature of the FeF3 discharge curve in the early stages of cycling. However, the two electrochemical stages of insertion and conversion reactions gradually merge as the conversion products and their domain distribution evolve, resulting in a curve profile similar to a solid solution reaction after long-term cycling. Because the fluorinated polymer electrolyte can suppress lithium dendrite formation on the negative electrode side and optimize the reversibility of the conversion reaction at the positive electrode interface, this solid-state lithium / iron fluoride battery can achieve more than 900 electrochemical cycles.

[0093] 6) Preparation and testing of pouch-type lithium / iron fluoride batteries based on fluorine-enhanced composite polymer electrolytes:

[0094] The preparation and testing of solid-state Li||FeF3 pouch cells are as follows: The prepared FeF3 positive electrode film was cut into 6×4cm pieces. 2 The flakes are approximately 1 mg / cm² in size, with an active material loading of approximately 1 mg / cm². 2 The 45-micrometer-thick lithium strip was cut into slightly larger pieces measuring 6.2 × 4.2 cm. 2 The fluorinated composite polymer electrolyte membrane LiTFSI-PEO-0.2AlF3 was cut into square pieces, each measuring 6.5 × 4.5 cm. 2 Larger, square-shaped sheets are used to separate the positive and lithium metal negative electrodes. These sheets are stacked in a lithium negative electrode-polymer electrolyte membrane-positive electrode configuration to assemble a pouch cell. The pouch cell was subjected to electrochemical testing in a 60°C oven. The pouch cell demonstrated an initial discharge capacity of up to 520 mAh / g at a current density of 110 mA / g, and maintained a capacity of 450-550 mAh / g over 100 cycles. Figure 12 As shown in the illustration, the corresponding charge and discharge curves exhibit highly repeatable shapes, and the discharge curve displays a clearly identifiable two-stage discharge plateau: an insertion phase near 3V and a transition phase near 2V.

[0095] 7) Preparation and Testing of Integrated Solid-State Lithium / Iron Fluoride Pouch Battery Based on Fluorine-Enhanced Composite Polymer Electrolyte: To further enhance the conductivity of the "ion conductors" inside the positive electrode and compensate for interfacial F loss during cycling, a small amount (8wt%) of high specific surface area AlF3 was introduced into the FeF3 positive electrode. Using PEO-LiTFSI-AlF3 as the ion conductor and carbon additives as the electron conductor, an integrated pouch solid-state fluorine-based lithium metal battery was constructed. The pouch battery was placed in a 60℃ oven for electrochemical testing at a current density of 153 mA / g. This enhanced pouch battery showed a dual upgrade in reversible capacity and cycle stability. After 20 cycles, the battery capacity reached its maximum of 589 mAh / g, and the reversible capacity remained at 425 mAh / g thereafter, maintaining this capacity for at least 200 cycles. Figure 13 As shown.

[0096] Example 2

[0097] 1) Preparation of high specific surface area nanoporous magnesium fluoride

[0098] 6.41g of magnesium nitrate hexahydrate Mg(NO3)2 . 6H₂O and 5.56 g of polyethylene glycol (PEG) were added to 50 mL of ethylene glycol and stirred at 60 °C to dissolve. Then, 4.5 mL of HF (40%) was added dropwise over 6 hours to achieve a Mg / F molar ratio of 1:4. The solution was then transferred to a 90 °C oven and aged for 24 hours to obtain a transparent wet gel. After drying at 150 °C for 8 hours, a white MgF₂ dry gel powder was obtained. This powder was transferred to a crucible and sintered in a muffle furnace at 400 °C for 4 hours to obtain a brown, fluffy MgF₂ powder. The obtained MgF₂ powder had a particle size between 10-20 nm and a specific surface area of ​​111 m². 2 / g, with a mesoporous structure (mesoporous pores of 10-24 nm).

[0099] 2) Preparation of nanoporous magnesium fluoride-reinforced composite polymer electrolyte

[0100] Fluorinated composite membranes were prepared by solution casting. First, 360 mg of LiTFSI and 880 mg of PEO powder (where [EO]:Li) were added. + A 16:1 ratio of MgF2 to acetonitrile was added to 20 mL of acetonitrile. Then, high specific surface area MgF2 powders with different weight ratios (5%, 10%, 20%, and 30%) were added to the solution. The mixture was stirred at room temperature for at least 12 hours to obtain a reddish-brown slurry solution. The solution was then cast onto a PTFE plate and evaporated at room temperature. Finally, the electrolyte membrane was peeled off from the PTFE mold and vacuum dried at 60°C for 12 hours before use.

[0101] 3) Assembly and testing of lithium metal symmetric cells based on MgF2 fluorination enhancement

[0102] The 2025 coin cell was assembled in an argon glove box with a water and oxygen level of less than 0.1 ppm. Specifically, 10 mm diameter lithium metal sheets were laid on both sides of a 16 mm diameter magnesium fluoride-fluorinated composite solid electrolyte to assemble a coin cell. The assembled 2025 coin cell symmetric battery was charged and discharged on a LAND electrochemical workstation at 0.1 mA / cm². 2 At a current density, the lithium metal was first charged at a constant current for 1 hour, and then discharged at a constant current for 1 hour. The voltage polarization difference during the deposition / stripping process was detected, and the cycle was carried out in this manner. Figure 14 For solid-state lithium metal symmetric batteries based on LiTFSI-PEO-0.2MgF2 fluorinated solid electrolyte at 0.1 mA / cm 2 The cycling curve of lithium metal deposition / stripping process at a certain current density is shown in the figure. It can be seen from the figure that at this current density, a stable deposition / stripping process can last for at least 2800 hours, and the single-sided overpotential is about 50mV.

[0103] 4) Assembly and Testing of Lithium / Iron Fluoride Batteries Based on Fluorine-Enhanced Composite Polymer Electrolytes: 2032 button cells were assembled in an argon glove box with water and oxygen levels less than 0.1 ppm. Specifically, a 10 mm diameter lithium metal sheet and a positive electrode containing active material were attached to both sides of a 16 mm diameter polymer film to assemble the lithium metal battery. The battery's electrochemical cycle performance was then tested at 60°C and different current densities using a LAND electrochemical workstation. Figure 15 The typical charge-discharge curves of the Li||FeF3 battery during the first 200 cycles are shown, with a voltage range of 1.2-3.9V and a current density of 525 mA / g. The battery's initial discharge capacity reaches 625 mA / g, enabling it to achieve more than 1000 electrochemical cycles. The discharge curves exhibit typical two-stage characteristics, fully demonstrating the plateau characteristics of the FeF3 discharge curve in the early stages of cycling, such as... Figure 15 As shown.

[0104] Comparative Example 1

[0105] 1) Preparation of commercial aluminum fluoride-filled composite polymer electrolytes:

[0106] Composite electrolyte membranes were prepared using a solution casting process. First, 360 mg of LiTFSI and 880 mg of PEO powder (with an [EO]:Li+ ratio of 16:1) were added to 20 mL of acetonitrile. Then, commercial aluminum fluoride powder (solid, non-mesoporous, with a particle size of 10-15 μm) at different weight ratios (5%, 10%, 20%, and 30%) was added to the solution. The mixture was stirred at room temperature for at least 12 hours to obtain a milky white slurry solution (i.e., the commercial aluminum fluoride powder was essentially insoluble). The solution was then cast onto a polytetrafluoroethylene (PTFE) plate and evaporated at room temperature. Finally, the electrolyte membrane was peeled off from the PTFE mold and vacuum dried at 60 °C for 12 hours before use.

[0107] 2) Assembly and Testing of Lithium / Iron Fluoride Batteries Based on Fluorine-Enhanced Composite Polymer Electrolytes: 2032 button cells were assembled in an argon glove box with water and oxygen levels less than 0.1 ppm. Specifically, a 10 mm diameter lithium metal sheet and a positive electrode containing active material were attached to both sides of a 16 mm diameter polymer film to assemble the lithium metal battery. The battery's electrochemical cycle performance was then tested at 60°C and different current densities using a LAND electrochemical workstation. Figure 16 This chart compares the discharge capacity of Li||FeF3 batteries based on a 20wt% nanoporous AlF3 fluorinated reinforced composite polymer electrolyte and a 20wt% commercial AlF3-filled composite polymer electrolyte after the first 300 cycles. The voltage range is 1.2–3.9 V, and the current density is 358 mA / g for the former and 200 mA / g for the latter. The nanoporous AlF3-enhanced Li||FeF3 battery maintains a higher discharge capacity advantage, exceeding the commercial AlF3-filled composite electrolyte system by approximately 120 mAh / g in the subsequent 200+ cycles. Figure 17 The figures show the charge-discharge curves for the two corresponding batteries at cycle 2 and cycle 100. The discharge curves exhibit typical two-stage characteristics, fully demonstrating the plateau characteristics of the FeF3 discharge curve in the early stages of cycling.

[0108] Finally, it is necessary to state that the above embodiments are only used to further illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A fluorinated reinforced composite polymer solid electrolyte, characterized in that, include: An organic polymer matrix, and lithium salts and fluorinated fillers dispersed in the organic polymer matrix; The fluorinated filler comprises a metal fluoride dissolved in an organic polymer matrix; the metal fluoride dissolved in the organic polymer matrix is ​​obtained by dissolving porous metal fluoride nanoparticles; the porous metal fluoride nanoparticles have a mesoporous structure with a pore size of 4–60 nm; the particle size of the porous metal fluoride nanoparticles is 10–100 nm, and the specific surface area is 45–300 m². 2 / g.

2. The fluorinated reinforced composite polymer solid electrolyte according to claim 1, characterized in that, The fluorinated filler comprises porous metal fluoride nanoparticles and metal fluorides dissolved in an organic polymer matrix.

3. The fluorinated reinforced composite polymer solid electrolyte according to claim 1, characterized in that, The organic polymer includes at least one of polyethylene oxide (PEO), polyacrylonitrile (PAN), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-co-hexafluoropropylene) PVDF-HFP. The lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiFSI), lithium hexafluorophosphate (LiPF6), and lithium perchlorate (LiClO4).

4. The fluorinated reinforced composite polymer solid electrolyte according to claim 1, characterized in that, The fluorinated filler in the fluorinated reinforced composite polymer solid electrolyte has a mass percentage of 5 wt% to 30 wt%.

5. The fluorinated reinforced composite polymer solid electrolyte according to claim 2, characterized in that, The mass percentage of fluorinated filler in the fluorinated reinforced composite polymer solid electrolyte is 5 wt% to 30 wt%; and the mass of porous metal fluoride nanoparticles does not exceed 50 wt% of the total mass of metal fluoride and porous metal fluoride nanoparticles dissolved in the organic polymer matrix.

6. The fluorinated reinforced composite polymer solid electrolyte according to claim 5, characterized in that, The mass of the porous metal fluoride nanoparticles does not exceed 20 wt% of the total mass of the metal fluoride dissolved in the organic polymer matrix and the porous metal fluoride nanoparticles.

7. The fluorinated reinforced composite polymer solid electrolyte according to claim 1, characterized in that, The porous metal fluoride nanoparticles include at least one of nanoporous aluminum fluoride AlF3, nanoporous magnesium fluoride MgF2, nanoporous cerium fluoride CeF3, and nanoporous oxygen-doped zirconium fluoride O-ZrF4; the metal fluoride is at least one of AlF3, MgF2, CeF3, and O-ZrF4.

8. The fluorination-enhanced composite solid electrolyte according to any one of claims 1-7, characterized in that, The molar mass of the organic polymer is calculated based on the molar mass of the polymeric monomers used to form the organic polymer, and the molar ratio of the organic polymer to the lithium salt is (10-20):

1.

9. The fluorination-enhanced composite solid electrolyte according to any one of claims 1-7, characterized in that, The thickness of the fluorinated reinforced composite solid electrolyte is 25–200 μm.

10. A method for preparing the fluorinated reinforced composite polymer electrolyte according to any one of claims 1-9, characterized in that, include: (1) Organic polymer, lithium salt and porous metal fluoride nanoparticles are added to an organic solvent and mixed to obtain a mixed slurry; (2) The obtained mixed slurry is cast onto a substrate to form a composite polymer film precursor; (3) The substrate coated with the composite polymer film precursor is heated to 40-80°C under vacuum and kept at that temperature for at least 24 hours, and then air-cooled to room temperature to obtain the fluorinated reinforced composite polymer electrolyte.

11. The preparation method according to claim 10, characterized in that, The method for synthesizing the porous metal fluoride nanoparticles includes: (1) Add the hydrated nitrate of the metal corresponding to the metal element in the porous metal fluoride and polyethylene glycol (PEG) to the ethylene glycol solution and stir at 40-60°C for 4-8 hours to obtain a transparent solution; (2) Then add hydrofluoric acid aqueous solution to the transparent solution to obtain fluoride wet sol; (3) age the fluoride wet sol at 25-90℃ for 12-24 hours to obtain fluoride wet gel; (4) The wet gel of fluoride is aged at 120-150°C for 12-24 hours to obtain dry gel powder of metal fluoride; (5) The obtained dry gel powder of metal fluoride is calcined in air at 350-450°C for 3-5 hours to obtain the porous metal fluoride nanoparticles.

12. The preparation method according to claim 10, characterized in that, In step (1), the organic solvent is one of acetonitrile (CAN), dimethylformamide (DMF), and N-methylpyrrolidone (NMP); the mixing method is stirring, which is stirring at room temperature to 60°C for 4 to 8 hours; the porous metal fluoride nanoparticles account for 5 wt% to 30 wt% of the total mass of the organic polymer, lithium salt, and porous metal fluoride nanoparticles.

13. The preparation method according to any one of claims 10-12, characterized in that, In step (2), the substrate is a polytetrafluoroethylene plastic sheet.

14. A lithium metal symmetric battery system based on a solid-state electrolyte, characterized in that, The lithium metal symmetric battery system includes the fluorinated reinforced composite polymer solid electrolyte as described in any one of claims 1-9, and lithium metal sheets located on both sides of the fluorinated reinforced composite polymer solid electrolyte.

15. A lithium metal battery based on a fluorine-enhanced composite polymer solid electrolyte, characterized in that, A solid-state lithium metal battery includes a positive electrode, a negative electrode, and a fluorinated reinforced composite polymer solid electrolyte of any one of claims 1-9 located between the positive and negative electrodes; The negative electrode is a lithium metal sheet; The positive electrode is at least one of FeF3, FeF2, iron-oxygen-fluorine compounds, CuF2, CuOHF, carbon-sulfur complexes, FeS2, LiMn2O4, LiFePO4, LiCoO2, nickel-rich ternary systems, and lithium-rich manganese-based solid solutions.

16. A solid-state lithium / fluoride battery with a pouch configuration based on a fluoride-enhanced composite polymer solid-state electrolyte, characterized in that, The pouch cell includes a positive electrode, a negative electrode, and a fluorinated reinforced composite polymer solid electrolyte of any one of claims 1-9 located between the positive and negative electrodes; The negative electrode is a thin-layer metallic lithium, and the positive electrode is at least one of FeF3, FeF2, ferrofluorine compound, CuF2, and CuOHF.

17. The solid-state lithium / fluoride battery according to claim 16, characterized in that, The positive electrode contains 3-15 wt% of a metal fluoride; the metal fluoride is at least one of AlF3, MgF2, CeF3, and O-ZrF4.

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