Fluorinated compact composite polymer electrolyte, and preparation method and application thereof

Abstract

The application provides a fluorinated compact composite polymer electrolyte, which comprises a first fluorine-containing polymer, a second fluorine-containing polymer, a lithium salt and a solvent, the first fluorine-containing polymer is a polyalkyl acrylate fluorine-containing alkyl ester, the second fluorine-containing polymer is a polyvinylidene fluoride polymer, and the solvent is a fluorine-containing alkyl amide compound. Through the intermolecular interaction between specific components, the application successfully constructs a compact, low-porosity and low-surface roughness composite polymer electrolyte. The structure synergistically regulates the crystallization behavior of the polymer and the solvation structure of Li + , significantly improving the mechanical properties, room temperature ionic conductivity and interface stability with the electrode of the electrolyte. The symmetrical battery and full battery based on the electrolyte exhibit super-long cycle life and excellent rate performance. The application provides a key material solution for developing high-safety, long-life and high-energy-density full solid-state lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of polymer electrolyte technology, and in particular to a fluorinated dense composite polymer electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as the current mainstream electrochemical energy storage technology, are gradually approaching the theoretical limit of energy density based on liquid electrolyte systems. More seriously, the inherent safety hazards of organic liquid electrolytes, such as flammability and leakage, have become a major constraint on the further development of electric vehicles, the low-altitude economy, and large-scale energy storage. Developing all-solid-state batteries using non-flammable solid electrolytes (SSEs) is considered an inevitable technological path to fundamentally improve battery safety and energy density. Among various solid electrolyte systems, solid polymer electrolytes (SPEs), with their excellent flexibility, good processing performance, higher safety, and the advantage of easily forming close contact with the electrode interface, have become a highly promising candidate material for realizing high-energy-density lithium metal batteries.

[0003] However, current solid polymer electrolytes often exhibit porous and spherical structures, resulting in low density. + Issues such as low solvation levels mean that their overall performance still lags significantly behind large-scale practical applications. The main technical bottlenecks are as follows: First, the ionic conductivity of polymer electrolytes at room temperature is generally low, below 5 × 10⁻⁶. -5 S cm -1 It is usually difficult to reach 10 -4 S cm -1 The above issues primarily stem from the limited chain mobility and crystallization tendency of the polymer matrix at room temperature, which severely restricts the rate performance and cycle performance of the battery. Secondly, the mechanical strength of existing polymer electrolytes is generally insufficient, below 0.6 MPa, typically lower than the threshold required to inhibit lithium dendrite growth. During long-term cycling, this strength cannot effectively prevent lithium dendrite penetration, leading to a risk of internal short circuits. Furthermore, the interface stability between the polymer electrolyte and the highly active lithium metal anode is poor. During electrochemical cycling, unstable interfacial side reactions continue to occur, leading to a continuous increase in interfacial impedance and the formation of a non-uniform, mechanically poor solid electrolyte interfacial film. This film cannot guide the uniform deposition and stripping of lithium ions, ultimately causing rapid capacity decay and a sharp shortening of cycle life, resulting in rapid battery degradation.

[0004] Therefore, fundamental innovation and design of solid-state polymer electrolyte systems are urgently needed. Developing a novel composite polymer electrolyte system that can synergistically resolve the aforementioned contradictions—possessing high room-temperature ionic conductivity, sufficient mechanical strength to suppress lithium dendrites, and excellent chemical and electrochemical compatibility with lithium metal anodes—would be crucial for the practical application of safe, long-life, and high-energy-density all-solid-state lithium metal batteries. Summary of the Invention

[0005] This invention addresses the problems of low room-temperature ionic conductivity, insufficient mechanical strength, and poor interfacial compatibility with lithium metal anodes in existing solid-state polymer electrolytes. It provides a fluorinated dense composite polymer electrolyte that simultaneously solves the challenges of mechanical strength, ionic conductivity, and interfacial stability in solid-state lithium batteries. The dense structure endows the electrolyte material with excellent mechanical strength, elongation at break, and adhesion, thereby giving it excellent processing performance and interfacial contact. The fluorinated dense composite polymer electrolyte reduces crystallinity and modulates the Li... + The ion-solventized structure achieves high ionic conductivity and promotes the formation of the LiF-rich solid electrolyte interface, thereby improving electrochemical cycling stability and rate performance. Therefore, the fluorination-assisted densification strategy employed in this invention plays a crucial role in the development of solid-state polymer electrolytes for solid-state batteries.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a fluorinated dense composite polymer electrolyte, the fluorinated dense composite polymer electrolyte comprising a first fluorinated polymer, a second fluorinated polymer, a lithium salt, and a solvent; the first fluorinated polymer is a polyalkyl acrylate with fluorinated alkyl ester, the second fluorinated polymer is a polyvinylidene fluoride polymer, and the solvent is a fluorinated alkyl amide compound; the solvent has a structure as shown in Formula 1, wherein R1 and R2 are each independently selected from C1-C3 alkyl groups or hydrogen atoms, and R3 is selected from fluorinated C1-C3 alkyl groups with ≥3 fluorine atoms; the first fluorinated polymer is obtained by polymerization of a compound as shown in Formula 2, wherein R4 is a fluorinated C1-C3 alkyl group with ≥3 fluorine atoms, and R5 is selected from C1-C3 alkyl groups; the mass percentage of the first fluorinated polymer in the fluorinated dense composite polymer electrolyte is 5-20%, the mass percentage of the second fluorinated polymer in the fluorinated dense composite polymer electrolyte is 20-60%, and the mass percentage of the lithium salt in the fluorinated dense composite polymer electrolyte is 30-60%. .

[0007] In existing technologies, when polyvinylidene fluoride (PVDF) polymers or composite polymer solid electrolytes are used as solid electrolytes, common compounds such as N,N-dimethylformamide (DMF) are used as solvents. This causes the solvent to accumulate around the PVDF crystals, forming an uneven solvent distribution. Phase separation between the solvent and the PVDF results in a naturally porous structure, leading to uneven lithium deposition and rapid lithium dendrite growth. Simultaneously, it reduces the efficiency of lithium deposition. + The degree of solvation at this point is unfavorable for improving ion transport efficiency. In existing technologies, inorganic fillers are commonly used to enhance the performance of polymer solid electrolytes. However, these fillers lead to a decrease in the material's dispersion performance, hindering filler dispersion and interfacial impedance suppression. This invention innovatively proposes using fluorinated alkylamide compounds as solvents to generate intermolecular interactions with the first fluorinated polymer. Simultaneously, the fluorinated alkylamide solvent exhibits good compatibility with the second fluorinated polymer. Through synergistic action with the first fluorinated polymer, the Li... + The solvation structure promotes the formation of large aggregates (AGGs), which in turn modulates the crystallization behavior of the second fluorinated polymer, reducing the crystallinity of the composite polymer electrolyte to below 20% and promoting the formation of the β-phase second fluorinated polymer, with the β-phase content reaching over 50%. Based on this, a stable solid-state electrolyte interface (SEI) layer rich in LiF is formed, significantly improving interfacial ion transport kinetics and suppressing lithium dendrite growth. Furthermore, it significantly improves the electrolyte's density, mechanical strength, and toughness, thereby enhancing the electrolyte's mechanical properties, room-temperature ionic conductivity, and interfacial stability with the electrode. Symmetrical and full cells assembled based on this electrolyte exhibit ultra-long cycle life and excellent rate performance.

[0008] As a further embodiment, the first fluoropolymer R4 contains at least one perfluoromethyl group, and the solvent R3 contains at least one perfluoromethyl group.

[0009] The present invention further preferably includes at least one perfluoromethyl group in the R3 and R4 groups of the first fluorinated polymer and the solvent. In this case, the solvation structure can be further optimized to promote the formation of aggregates (AGG), thereby promoting the formation of lithium-rich SEI and increasing the β phase ratio of the second fluorinated polymer.

[0010] As a further embodiment, the first fluorinated polymer has a mass percentage of 7-15% in the fluorinated dense polymer electrolyte, the second fluorinated polymer has a mass percentage of 30-45% in the fluorinated dense polymer electrolyte, and the lithium salt has a mass percentage of 45-55% in the fluorinated dense polymer electrolyte.

[0011] As a further embodiment, the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte includes a solvent-separated ion pair (SSIP), a contact ion pair (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2); wherein the solvent-separated ion pair (SSIP) is the lithium salt anion that has not reacted with Li. + Direct contact; contact ion pair (CIP) is a lithium salt in which anion directly reacts with Li. + Contact; Aggregate-1 (AGG-1) is an anion in a lithium salt that directly reacts with two Li... + Contact; Aggregate-2 (AGG-2) is a lithium salt in which one anion directly reacts with two or more Li groups. + touch.

[0012] When the lithium salt solvation structure is SSIP, Li + Surrounded by solvent, Li + The interaction force with dissolution is higher than that with anions; when the lithium salt solvation structure is CIP, Li + The inner layer of the solvation shell contains an anion and multiple coordinating solvents.

[0013] As a further embodiment, the contents of solvent-separated ion pairs (SSIP), contact ion pairs (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2) in the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte are obtained by Raman spectral peak fitting.

[0014] As a further preferred embodiment, the solvent-separated ion pairs (SSIP), contact ion pairs (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2) are distinguished according to the beam of the Raman spectrum, wherein the beam of the solvent-separated ion pairs (SSIP) is 715-725 cm⁻¹. -1 The beam of contact ion pair (CIP) is 726-735 cm. -1 The beam of Aggregator-1 (AGG-1) is 740-750 cm. -1 The beam of Aggregator-2 (AGG-2) is 760-770 cm. -1 .

[0015] As a further embodiment, the total content of aggregate-1 (AGG-1) and aggregate-2 (AGG-2) in the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte is ≥85%.

[0016] As a further embodiment, the β-phase content in the second fluorinated polymer of the fluorinated dense composite polymer electrolyte is ≥50%, and the crystallinity of the fluorinated dense composite polymer electrolyte is ≤20%. In this invention, the β-phase content was obtained by Fourier transform infrared spectroscopy, and the crystallinity of the fluorinated dense composite polymer electrolyte was obtained by XRD.

[0017] As a further embodiment, the polyvinylidene fluoride compounds include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), and polyvinylidene fluoride-trifluorochloroethylene copolymer (PVDF-CTFE).

[0018] As a further embodiment, the polyalkyl acrylate fluorinated alkyl ester includes one or more of the following: poly(trifluoroethyl methacrylate), poly(trifluoroethyl methacrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), poly(hexafluorobutyl methacrylate), and poly(hexafluorobutyl methacrylate).

[0019] As a further embodiment, the fluorinated alkylamide compound includes one or more of 2,2,2-trifluoro-N,N-dimethylacetamide and 2,2,2-trifluoroacetamide.

[0020] As a further preferred embodiment, the first fluoropolymer is poly(trifluoroethyl methacrylate) (PTFMA), the second fluoropolymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), the lithium salt is lithium bis(fluorosulfonyl imide) (LiFSI), and the solvent is 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA).

[0021] As a further embodiment, the fluorinated dense composite polymer electrolyte possesses at least one of the following characteristics: (1) The surface roughness R of the fluorinated dense composite polymer electrolyte was measured by atomic force microscopy (AFM). a ≤40 nm; (2) The tensile strength of the fluorinated dense composite polymer electrolyte is >3.8 MPa, the elongation at break is >350%, and the toughness is >15 MJ / m. -3 ; (3) The electrochemical stability window of the fluorinated dense composite polymer electrolyte is >4.7 V; (4) The room temperature ionic conductivity of the fluorinated dense composite polymer electrolyte is >5×10⁻⁶. -3 S cm -1 ; (5) The shear strength of the fluorinated dense composite polymer electrolyte obtained by the overlap shear test is >30 kPa; (6) The Li||Li symmetric battery prepared by the fluorinated dense composite polymer electrolyte exhibits a performance of 0.5 mA / cm² at room temperature. -2 Cycling at current density for 3800 h; (7) The full cell prepared by the fluorinated dense composite polymer electrolyte maintains a capacity retention of ≥78% after 1000 cycles at room temperature and 0.5C. (8) The full cell prepared by the fluorinated dense composite polymer electrolyte maintains a capacity retention of ≥76% after 1000 cycles at room temperature and 2C. (9) The battery Li prepared from the fluorinated dense composite polymer electrolyte + Migration number ≥ 0.45.

[0022] Secondly, the present invention also provides a method for preparing the fluorinated composite polymer electrolyte, comprising the following steps: S1: Under an inert atmosphere, the first fluoropolymer, the second fluoropolymer, and the lithium salt are dissolved in a solvent according to the target stoichiometric ratio; the first fluoropolymer, the second fluoropolymer, and the lithium salt constitute 0.8% to 30% of the solvent mass during the dissolution process. S2: Pour the solution obtained in S1 into a container and dry it at 20~100 °C for 4~24 h. Evaporate the solvent to obtain fluorinated dense composite polymer electrolyte.

[0023] As a further option, the dissolution temperature in S1 is 20~100 °C.

[0024] As a further embodiment, in step S1, the inert atmosphere includes helium, neon, argon, and nitrogen, wherein the water content and oxygen content are both less than 0.1 ppm.

[0025] As a further embodiment, in step S2, the drying temperature is 60 °C and the drying time is 12 h.

[0026] As a further preferred embodiment, the residual solvent content after drying is less than 15% of the mass ratio of the fluorinated dense composite polymer electrolyte.

[0027] Thirdly, the present invention also provides a solid-state battery comprising a positive electrode, a negative electrode, and an electrolyte layer located between the positive electrode and the negative electrode, wherein the electrolyte layer comprises the fluorinated dense composite polymer electrolyte described in the first aspect or the fluorinated dense composite polymer electrolyte prepared by the preparation method described in the second aspect.

[0028] The features and beneficial effects of this invention are as follows: (1) This invention introduces two fluorinated compounds as the first fluorinated polymer and the solvent, respectively. These compounds interact intermolecularly and synergistically with the second fluorinated polymer, achieving a densified design and synergistic structural control of the fluorinated components. This significantly reduces the crystallinity of the composite polymer electrolyte and promotes the formation of the β-phase second fluorinated polymer, which is beneficial for ion transport. Simultaneously, the first fluorinated polymer optimizes the Li... + Its solvated structure results in an aggregate (AGG) content exceeding 85%. This enables the electrolyte to achieve a high content of 6.1 × 10⁻⁶ at room temperature. -3 S cm -1 The ionic conductivity, and Li above 0.45 + The migration number is far superior to that of traditional porous polymer electrolytes, thus ensuring the excellent rate performance of solid-state batteries.

[0029] (2) The fluorinated dense composite polymer electrolyte of the present invention has a dense structure, low porosity, and a surface roughness R a Features such as ≤40nm. This structure endows the electrolyte membrane with excellent comprehensive mechanical properties: tensile strength exceeding 4.8 MPa, elongation at break exceeding 550%, and toughness reaching 20 MJ / m. -3 The puncture resistance reaches over 200 gf. This not only effectively suppresses lithium dendrite puncture during battery cycling, but also ensures the structural integrity and processing performance of the electrolyte during battery assembly and long-term operation.

[0030] (3) This electrolyte exhibits a wide electrochemical stability window of up to 4.92 V. More importantly, its AGG-rich solvation structure can induce the formation of a uniform, stable, and LiF-rich (up to 90%) solid electrolyte interphase (SEI) film on the lithium metal anode surface. This SEI film has high ionic conductivity and mechanical strength, which can effectively reduce interfacial impedance, promote uniform lithium ion deposition / stripping, and suppress side reactions, thereby significantly improving interfacial stability.

[0031] (4) The battery assembled based on the fluorinated dense composite polymer electrolyte (d-FCPE) of the present invention exhibits excellent electrochemical performance: the Li||Li symmetric cell at 0.5 mA cm⁻¹ -2 It can be stably cycled for more than 3800 hours at current density; after 1000 cycles at 0.5C and 2C rates, the full cell matched with NCM523 cathode still retains more than 80% of its capacity, which proves that this electrolyte system has great practical application potential in realizing high-safety and long-life solid-state batteries.

[0032] In summary, the innovative strategies of fluorination and densification employed in this invention have successfully prepared a composite polymer electrolyte that combines high ionic conductivity, excellent mechanical strength, and outstanding interfacial stability, providing a key material solution for the development of next-generation high-energy-density, high-safety all-solid-state lithium metal batteries. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram illustrating the design principle of a fluorinated dense composite polymer electrolyte.

[0035] Figure 2 SEM images of the polymer electrolytes prepared in Comparative Examples 1, 2, and 1 at a scale of 20 μm.

[0036] Figure 2 In Figure a, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1 is shown by SEM at a scale bar of 20 μm. Figure 2 In Figure b, the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2 is shown by SEM at a scale bar of 20 μm. Figure 2 In the image c, the polymer electrolyte (d-FCPE) prepared in Example 1 is shown as a SEM image at a scale of 20 μm.

[0037] Figure 3 The surface smoothness images of the polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown by atomic force microscopy (AFM).

[0038] Figure 3 In Figure a, the surface smoothness of the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1 is shown by atomic force microscopy (AFM). Figure 3 In Figure b, the surface smoothness of the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2 is shown by atomic force microscopy (AFM). Figure 3 In the image c, the surface smoothness of the polymer electrolyte (d-FCPE) prepared in Example 1 is shown by atomic force microscopy (AFM).

[0039] Figure 4The stress-strain curves are shown for the composite polymer electrolyte (d-FCPE) prepared in Example 1, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2.

[0040] Figure 5 The figures show the puncture strength of the composite polymer electrolyte (d-FCPE) prepared in Example 1, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2.

[0041] Figure 6 The figures show the overlap shear test results of the composite polymer electrolyte (d-FCPE) prepared in Example 1 and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2.

[0042] Figure 7 Fourier transform infrared (FT-IR) spectra of the polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0043] Figure 7 In Figure a, the composite polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 have a molecular weight of 1590~155 cm⁻¹. -1 FT-IR; Figure 7 In Figure b, the polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 have a temperature range of 2820–2940 cm⁻¹. -1 FT-IR.

[0044] Figure 8 The X-ray diffraction patterns of the polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2, and the X-ray diffraction pattern of PTEMA are shown.

[0045] Figure 8 In Figure a, the X-ray diffraction pattern of the polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 is shown. Figure 8 In the diagram, b is the X-ray diffraction pattern of PTEMA.

[0046] Figure 9 Fourier transform infrared (FTIR) and Raman spectra of the composite polymer electrolyte (d-FCPE) prepared in Example 1, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2.

[0047] Figure 9In Figure a, the Fourier transform infrared spectra of the composite polymer electrolyte (d-FCPE) prepared in Example 1, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2 are shown. Figure 9 In Figure b, the Raman spectra of the composite polymer electrolyte (d-FCPE) prepared in Example 1, the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, and the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2 are shown.

[0048] Figure 10 To obtain the peak area ratios of SSIP, CIP, AGG-1, and AGG-2 in the electrolyte and Li based on Raman spectral fitting results. + FT-IR spectra of solvated structures in electrolytes.

[0049] Figure 10 In the figure, 'a' represents the peak area ratio of SSIP, CIP, AGG-1, and AGG-2 in the electrolyte, obtained from the Raman spectroscopy fitting results. Figure 10 b is Li + FT-IR spectra of solvated structures in electrolytes.

[0050] Figure 11 Impedance and activation energy diagrams for Example 1, Comparative Example 1, and Comparative Example 2 at 30-65 °C.

[0051] Figure 11 In Figure a, the impedance diagram of Comparative Example 1 is shown at 30-65 °C. Figure 11 In Figure b, the impedance diagram of Comparative Example 2 is shown at 30-65 °C. Figure 11 c is the impedance diagram of Example 1 at 30-65 °C; Figure 11 In the diagram, d represents the activation energy diagrams of Example 1, Comparative Example 1, and Comparative Example 2.

[0052] Figure 12 The current curves (insets showing EIS plots before and after current measurement) of the Li||Li batteries assembled with the composite polymer electrolytes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were used to calculate Li + Number of migrations.

[0053] Figure 12 In Figure a, the current curve of the Li||Li battery assembled from the polymer electrolyte (PVDF-HFP) prepared in Comparative Example 1, measured by potentiostatochronoamperometry (inset shows the EIS plots before and after current measurement), is used to calculate Li.+ Number of migrations; Figure 12 In Figure b, the current curve of the Li||Li battery assembled from the polymer electrolyte (d-PVDF-HFP) prepared in Comparative Example 2, measured by potentiostatochronoamperometry (the inset shows the EIS plots before and after current measurement), is used to calculate Li. + Number of migrations; Figure 12 In Figure c, the current curve of the Li||Li battery assembled with the composite polymer electrolyte (d-FCPE) prepared in Example 1, measured by potentiostat chronoamperometry (the inset shows the EIS plots before and after current measurement), is used to calculate Li. + Number of migrations.

[0054] Figure 13 Example 1, Comparative Example 1, and Comparative Example 2 were performed at a scan rate of 0.1 mV / s. -1 Linear sweep voltammetry (LSV) curves at different times.

[0055] Figure 14 Example 1, Comparative Example 1, and Comparative Example 2 were performed at a scan rate of 0.1 mV / s. -1 Multi-cycle cyclic voltammetry curves (CV) over time.

[0056] Figure 14 In Figure 'a', comparative example 1 is performed at a scan rate of 0.1 mV / s. -1 Multi-cycle cyclic voltammetry curves (CV) at different times; Figure 14 In Figure b, comparative example 2 is performed at a scan rate of 0.1 mV / s. -1 Multi-cycle cyclic voltammetry curves (CV) at different times; Figure 14 In Example 1, c represents the scanning rate at 0.1 mV / s. -1 Multi-cycle cyclic voltammetry curves (CV) over time.

[0057] Figure 15 For 0.2 mA cm -2 Cycling curves of Li||Li symmetric cells in Example 1, Comparative Example 1, and Comparative Example 2 at current density.

[0058] Figure 16 SEM images and photographs of the lithium anodes of the polymer electrolyte batteries prepared in Comparative Examples 1, 2, and 1 after cycling.

[0059] Figure 16 In Figure a, the lithium anode of the polymer electrolyte (PVDF-HFP) battery prepared in Comparative Example 1 is shown as an SEM image and photograph after cycling. Figure 16In Figure b, there are SEM images and photographs of the cycled lithium anode of the polymer electrolyte (d-PVDF-HFP) battery prepared in Comparative Example 2. Figure 16 In Figure c, there is a SEM image and photograph of the lithium anode of the composite polymer electrolyte (d-FCPE) battery prepared in Example 1.

[0060] Figure 17 The F 1s spectra of SEI for Example 1, Comparative Example 1, and Comparative Example 2 at different sputtering times are shown.

[0061] Figure 17 In Figure a, the F 1s spectrum of SEI in Comparative Example 1 is shown at different sputtering times. Figure 17 In Figure b, the F 1s spectrum of the SEI at different sputtering times is shown in Comparative Example 2. Figure 17 c represents the F 1s spectrum of SEI in Example 1 at different sputtering times.

[0062] Figure 18 The C1s spectra of SEI for Example 1, Comparative Example 1, and Comparative Example 2 at different sputtering times are shown.

[0063] Figure 18 In Figure 'a', the C 1s spectrum of the SEI in Comparative Example 1 is shown at different sputtering times. Figure 18 In Figure b, the C 1s spectrum of the SEI at different sputtering times is shown in Comparative Example 2. Figure 18 c represents the C 1s spectrum of SEI in Example 1 at different sputtering times.

[0064] Figure 19 The O 1s spectra of SEI for Example 1, Comparative Example 1, and Comparative Example 2 at different sputtering times are shown.

[0065] Figure 19 In Figure a, the O 1s spectrum of SEI under different sputtering times is shown in Comparative Example 1. Figure 19 In Figure b, the O 1s spectrum of SEI under different sputtering times is shown in Comparative Example 2. Figure 19 c represents the O 1s spectrum of SEI in Example 1 at different sputtering times.

[0066] Figure 20 The relative distribution of lithium-containing materials in the SEI at different depths in the polymer electrolyte batteries prepared in Comparative Examples 1, 2, and 1 is shown.

[0067] Figure 21Rate performance testing of Li||NCM523 batteries prepared for Comparative Example 1, Comparative Example 2, and Example 1.

[0068] Figure 22 The long-cycle performance of the Li||NCM523 batteries prepared in Comparative Example 1, Comparative Example 2, and Example 1 at 0.5C and room temperature is measured.

[0069] Figure 23 The cycling performance of the Li||NCM523 batteries prepared in Comparative Example 1, Comparative Example 2, and Example 1 at 2C and room temperature is shown. Detailed Implementation

[0070] To facilitate understanding of the present invention, a more comprehensive description of the present invention will be given below, and embodiments of the present invention will be provided, but this does not limit the scope of the present invention.

[0071] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0072] The chemical raw materials used in the following examples and comparative examples are all prior art and commercially available. The experimental apparatus and testing equipment used in the following examples and comparative examples are all conventional equipment in the art, and there are no special requirements or limitations.

[0073] As a specific example of the implementation of this invention, detailed cases are provided below: Example 1: Preparation of composite polymer electrolyte (d-FCPE): The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer, 0.08 g of poly(trifluoroethyl methacrylate) (PTFMA), and 0.4 g of LiFSI were dissolved in 10 mL of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding the composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0074] Example 2: Preparation of the composite polymer electrolyte: The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer, 0.04 g of poly(trifluoroethyl methacrylate) (PTFMA), and 0.4 g of LiFSI were dissolved in 10 mL of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding the composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0075] Example 3: Preparation of the composite polymer electrolyte: The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer, 0.12 g of poly(trifluoroethyl methacrylate) (PTFMA), and 0.4 g of LiFSI were dissolved in 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding the composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0076] Example 4: Preparation of the composite polymer electrolyte: The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride copolymer (PVDF), 0.08 g of poly(trifluoroethyl methacrylate) (PTFMA), and 0.4 g of LiFSI were dissolved in 10 mL of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding the composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0077] Example 5: Preparation of the composite polymer electrolyte: The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride copolymer (PVDF), 0.08 g of polypentafluoropropyl methacrylate (PFM), and 0.4 g of LiFSI were dissolved in 10 mL of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding the composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0078] Comparative Example 1: Preparation of Polymer Electrolyte (PVDF-HFP): 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and 0.4 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in N,N-dimethylformamide (DMF). After stirring until completely dissolved, the solution was poured into a glass dish and dried at 60 °C for 12 h, followed by vacuum drying at 60 °C for 12 h to obtain the polymer electrolyte membrane. The electrolyte membrane was cut into 16 mm diameter discs for use in the fabrication of solid-state batteries.

[0079] Comparative Example 2: Preparation of Polymer Electrolyte (d-PVDF-HFP): 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and 0.4 g of lithium bisfluorosulfonylimide (LiFSI) were dissolved in 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish and dried at 60 °C for 12 h to evaporate the FDMA, obtaining a polymer electrolyte membrane. The electrolyte membrane was cut into discs with a diameter of 16 mm for use in the preparation of solid-state batteries.

[0080] Comparative Example 3: Preparation of Polymer Electrolyte: 0.3 g of polyvinylidene fluoride-hexafluoropropylene copolymer, 0.08 g of poly(trifluoroethyl methacrylate) (PTFMA), and 0.4 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in N,N-dimethylformamide (DMF). After stirring until completely dissolved, the solution was poured into a glass dish and dried at 60 °C for 12 h, followed by vacuum drying at 60 °C for 12 h to obtain the polymer electrolyte membrane. The electrolyte membrane was cut into 16 mm diameter discs for use in the fabrication of solid-state batteries.

[0081] Comparative Example 4: Preparation of Polymer Electrolyte: The preparation was carried out in an argon-filled glove box with a water content <0.1 ppm and an oxygen content <0.1 ppm. 0.3 g of polyvinylidene fluoride copolymer, 0.08 g of polyethyl methacrylate (PTFMA), and 0.4 g of LiFSI were dissolved in 10 mL of 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA). After stirring until completely dissolved, the solution was poured into a glass dish. The solution was dried at 60 °C for 12 h to evaporate the FDMA, yielding a composite polymer electrolyte membrane. The composite polymer electrolyte membrane was cut into 16 mm discs for use in the fabrication of solid-state batteries.

[0082] Positive electrode sheets were prepared for Examples 1-5 and Comparative Examples 1-4 according to the following method: Preparation method of NCM523 positive electrode: NCM523, polyvinylidene fluoride (PVDF), and SuperP are dissolved in N-methylpyrrolidone at a mass ratio of 8:1:1 to form a slurry mixture. The slurry mixture is then coated onto carbon-coated aluminum foil and dried at 100 °C. The loading of NCM523 is 2 mg cm⁻¹. -2 .

[0083] The NCM9055 and LFP cathodes were prepared using the same method as the NCM523 cathode, except that the active material NCM523 was replaced with NCM9055 and LFP, respectively, with the same loading of 2 mg cm⁻¹. -2 .

[0084] Following conventional battery fabrication methods in the art, SS|SPE|SS symmetric cells, Li|SPE|Cu cells, Li|SPE|Li symmetric cells, Li|SPE|LFP cells, and Li|SPE|NCM523 cells were fabricated.

[0085] The polymer electrolytes or batteries prepared in Examples 1-5 and Comparative Examples 1-4 were tested according to the following methods: (1) Crystallinity test: The crystallinity of the polymer electrolyte was analyzed by X-ray diffraction. The material scanning range was 10 ° to 60 °, and the scanning speed was 10 ° min. -1 .

[0086] (2) Infrared spectroscopy and Raman spectroscopy: Fourier transform infrared spectrometer and Raman spectroscopy were used to study the functional groups of the material.

[0087] (3) Scanning electron microscopy was used to observe the surface morphology, cross-sectional morphology and elemental distribution of all samples.

[0088] (4) Use an STM material testing machine at 2 mm min -1The strain rate is used to evaluate the mechanical and puncture properties of the material.

[0089] (5) Measurements were performed using atomic force microscopy (AFM) on the Oxford Cypher-ES AFM system at room temperature.

[0090] (6) X-ray photoelectron spectroscopy (XPS) was used to analyze the evolution of the lithium interface through K-Alpha+.

[0091] (7) Electrochemical impedance spectroscopy (EIS) was used to measure the electrochemical impedance spectroscopy (EIS) at 10... -2 Hz to 10 7 Ionic conductivity was evaluated using SS|SPEs|SS symmetric cells within the Hz frequency range.

[0092] (8) The activation energy was determined by EIS test in the temperature range of 30 °C to 60 °C.

[0093] (9) The linear sweep voltammetry (LSV) method was used to assess oxidation resistance using a test voltage range from open circuit voltage to 6V and a scan rate of 0.1 mV s. -1 .

[0094] (10) The stability of the lithium anode electrolyte was evaluated using cyclic voltage (CV). The test voltage range was from open circuit voltage to -0.5 V, and the scan rate was 0.1 mV s. -1 ; Both CV and LSV tests were performed using assembled Li|SPEs|SS cells.

[0095] (11) Assemble Li|SPE|Li at 0.5 mA cm -2 Long-term cycling performance at current density.

[0096] (12) Li|SPE|LFP and Li|SPE|NCM523 batteries were assembled to evaluate the application value of the electrolyte. All charge-discharge and rate performance tests were performed on LAND or Neware battery testing systems.

[0097] Table 1

[0098] Examples 1-3, by adjusting the different composite amounts of the first polymer, show that Example 1 exhibits the best low crystallinity, the highest β-phase PVDF-HFP content, and the best surface smoothness in the composite electrolyte, resulting in superior electrochemical performance. Examples 4-5, by changing the specific types of the first and second polymers, still maintain excellent crystallinity, β-phase PVDF-HFP content, and surface smoothness, demonstrating its general value. A comparison of Examples 1 and 5 shows that the presence of perfluoromethyl groups plays a crucial role in improving the overall performance of the composite polymer electrolyte. Although Comparative Example 3 still shows improvement compared to the single polymer (Comparative Example 1), the use of a non-fluorinated solvent significantly reduces various properties. Comparative Example 4, by replacing the first polymer with a non-fluorinated polymer, still maintains excellent surface smoothness, but the crystallinity and β-phase PVDF-HFP content are significantly reduced. This is due to the improvement of the composite polymer by the strongly polar fluorinated groups. Based on the above comparison of physical properties, the practical value of fluorination densification is also demonstrated in electrochemical performance.

[0099] Depend on Figure 1 As can be seen, the schematic diagrams of the polymer electrolytes in Example 1 and Comparative Example 1 of this invention show the differences in the corresponding SEI formed on the Li metal anode by the polymer electrolyte structure prepared in Comparative Example 1 and the fluorinated dense composite polymer electrolyte structure prepared in Example 1. They also demonstrate the amplified structure of the fluorinated dense composite polymer electrolyte structure prepared in Example 1 and the LiF-enriched SEI composition. The fluorinated composite polymer electrolyte prepared in Example 1 can synergistically optimize mechanical strength, ionic conductivity, and interfacial stability. The d-FCPE of Example 1 significantly improves mechanical strength, toughness, and shear strength, effectively suppressing volume change and dendrite penetration. Furthermore, the lower crystallinity in the d-FCPE of Example 1 and the PVDF-HFP-enriched β phase contribute to improved ion conduction. Simultaneously, the strongly polar fluorinated polymer component modulates the solvation structure to promote the formation of aggregates (AGGs), thereby promoting lithium-rich SEI. This SEI enhances interfacial ion transport kinetics and achieves uniform lithium deposition.

[0100] A comparison of Examples 1-5 and Comparative Examples 1-4 shows that different solvents and polymer electrolyte compositions and ratios will result in polymer electrolytes or composite polymer electrolytes with different degrees of densification. Specifically, the polymer electrolyte prepared in Comparative Example 1 of this invention was prepared from PVDF-HFP using N,N-dimethylformamide (DMF) as the solvent. Figure 2 As can be seen in Figure a, the polymer electrolyte prepared in Comparative Example 1 consists of spherical polymer particles and exhibits a highly porous morphology. This porous structure arises from phase separation during solvent evaporation, which may be due to the strong interaction between PVDF-HFP and DMF. Figure 2As can be seen in Figure b, the polymer electrolyte (d-PVDF-HFP) prepared by Comparative Example 2 using FDMA as a solvent exhibits a compact structure due to the weak interaction between FDMA and PVDF-HFP, but still contains some visible cracks.

[0101] Example 1 of this invention constructed a dense composite polymer electrolyte by introducing a miscible first fluoropolymer: poly(trifluoroethyl methacrylate) (PTFMA). From Figure 2 The scanning electron microscope (SEM) image of c shows that the fluorinated dense composite polymer electrolyte prepared in Example 1 has a dense microstructure.

[0102] In addition, by Figure 3 Atomic force microscopy (AFM) showed that, compared with Comparative Example 2 (surface roughness Ra of 45.1 nm) and Comparative Example 1 (surface roughness Ra of 62.1 nm), the composite polymer electrolyte prepared in Example 1 has a lower surface roughness Ra of only 32.3 nm. The low porosity composite polymer electrolyte prepared in this invention has the effect of improving electrode interface contact.

[0103] This invention employs mechanical strength testing to investigate the relationship between densification degree and mechanical strength. As shown in Figure 4, the tensile test results indicate that, compared to Comparative Example 2 (tensile strength 2.63 MPa, elongation at break 286%) and Comparative Example 1 (tensile strength 0.52 MPa, elongation at break 17%), the polymer solid electrolyte prepared in Example 1 exhibits higher tensile strength (4.87 MPa) and elongation at break (572%). Therefore, the toughness of Example 1 is 21.68 MJ / m². -3 It is approximately 6.23 MJ / m² of Comparative Example 2. -3 It is 3.5 times that of Comparative Example 1 (0.05 MJ m -3 More than 430 times that of ).

[0104] Depend on Figure 5 The puncture resistance test showed that the PVDF-HFP of Comparative Example 1 failed under an external force of 25.06 gf, and the d-PVDF-HFP of Comparative Example 2 failed under an external force of 116.72 gf, which was significantly lower than that of the d-FCPE of Example 1 (227.41 gf).

[0105] Depend on Figure 6 The overlap shear test showed that the shear strength (30.2 kPa) of the d-FCPE prepared in Example 1 was higher than that of the d-PVDF-HFP in Comparative Example 2 (25.5 kPa), while the adhesion of the PVDF-HFP prepared in Comparative Example 1 was negligible.

[0106] To elucidate the structural and chemical evolution of the electrolyte during densification, we tested its physicochemical properties. Figure 7 Fourier transform infrared spectroscopy analysis showed an increased β-phase content (>50%) in d-FCPE, confirming that PTFMA promotes PVDF-HFP structural reconstruction. Furthermore, [the following text appears to be incomplete and requires further context: "by..."] Figure 8 X-ray diffraction (XRD) results showed that the intensity of the crystallization peak of the electrolyte decreased with increasing densification. In particular, the d-FCPE of Example 1 showed almost no crystallinity (10%), indicating that the incorporation of PTFMA increases the amorphous phase fraction, which is beneficial for ion conduction.

[0107] Depend on Figure 9 As can be seen from the Fourier transform infrared spectrum of a, the C=O characteristic peak of FDMA in Example 1 is observed at 1683.07 cm⁻¹. -1 Up to 1692.51 cm -1 The shift indicates the presence of intermolecular interactions between polar PTFMA and FDMA. This dipole-dipole interaction causes more FDMA solvent molecules to transition from a free-moving state to an anchored state, thus establishing a competitive coordination environment and weakening the Li... + - Combination of FDMA.

[0108] Depend on Figure 9 As can be seen from b, the Li was further studied using Raman spectroscopy. + The solvated structure. FSI in Raman spectroscopy. - The SNS dipole vibration modes exhibited four distinct components, corresponding to solvent-separated ion pairs (SSIP), contact ion pairs (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2), respectively. Raman spectroscopy showed that the AGG contents in Comparative Example 1, Comparative Example 2, and Example 1 were 17.59%, 75.56%, and 96.26%, respectively. Figure 10 It can also be seen that the AGG content was the highest in Example 1, which is attributed to the regulation of the coordination environment by PTFMA.

[0109] Based on the improved mechanical strength achieved through densification design and optimized structural chemistry, we conducted electrochemical tests. For example... Figure 11 As shown, compared with the PVDF-HFP (4.3 × 10⁻⁶) prepared in Comparative Example 1, -4 S cm -1 ) and the d-PVDF-HFS (4.8 × 10⁻⁶) prepared in Comparative Example 2 -4 S cm -1Compared to the previous example, the d-FCPE prepared in Example 1 exhibited higher ionic conductivity (6.1 × 10⁻⁶) at room temperature. -3 S cm -1 Furthermore, d-FCPE has a lower activation energy, which is more conducive to ion migration.

[0110] In addition, by Figure 12 It can be seen that the Li in d-FCPE prepared in Example 1 + The migration number was 0.6, which exceeded that of d-PVDF-HFP (0.41) prepared in Comparative Example 2 and PVDF-HFP (0.12) prepared in Comparative Example 1.

[0111] The oxidation and reduction stability of the electrolyte were determined using linear sweep voltammetry (LSV) and multi-cycle cyclic voltammetry (CV). Figure 13 It can be seen that the electrochemical stability window of the dFCPE prepared in Example 1 is expanded to 4.92 V, which is higher than that of Comparative Example 2 (4.58 V) and Comparative Example 1 (4.33 V).

[0112] Depend on Figure 14 As can be seen, the multi-cycle cyclic voltammetry (CV) showed that the reduction peak of d-FCPE in Example 1 weakened and stabilized within two cycles, indicating the formation of a stable SEI. In contrast, the electrolytes of Comparative Examples 1 and 2 exhibited irregular and unstable reduction curves, indicating their poor compatibility with lithium metal.

[0113] To gain a deeper understanding of the stability between the electrolyte and lithium metal, we assembled a lithium-symmetric battery and tested it at different current densities. Thanks to the enhanced mechanical strength and interfacial compatibility of d-FCPE, Depend on Figure 15 It can be seen that at 0.5 mA cm -2 At higher current densities, the Li|PVDF-HFP|Li battery fails almost immediately, the Li|d-PVDF-HFP|Li battery fails after 200 hours, while the Li|d-FCPE|Li prepared in Example 1 remains stable for more than 3800 hours.

[0114] To gain a deeper understanding of the microstructure evolution and SEI formation of Li anodes, we studied the microstructure at 0.2 mA cm⁻¹. -2 The Li anode obtained from the Li||Li cell after 50 cycles was analyzed post-cycle. The Li deposition morphology was studied using SEM. Figure 16 As can be seen in Figure a, the cycled Li anode obtained from the Li|PVDF-HFP|Li battery exhibits obvious black dendritic crystals and significant cracks, indicating severe structural degradation. In contrast, the Li anode obtained from the Li|PVDF-HFP|Li battery... Figure 16 As can be seen in Figure b, the cyclic lithium anode using d-PVDF-HFP in Comparative Example 2 exhibits a relatively flat surface, while trace dendritic particles are still quite noticeable.

[0115] Depend on Figure 16 As can be seen from Figure c, the d-FCPE of Example 1 maintains the compact and smooth morphology of the recycled lithium metal anode, demonstrating reduced internal corrosion and improved interface stability.

[0116] The composition and spatial evolution of the SEI were further analyzed using X-ray photoelectron spectroscopy (XPS).

[0117] Depend on Figure 17 The F 1s spectrum shows that the d-FCPE-derived SEI surface contains the highest LiF content, and the LiF content remains stable with increasing etching depth. This is due to its richer AGG solvation structure. Figure 18 The C 1s spectrum shows that the PVDF-HFP derived SEI has the highest organic content on its surface, which is due to the continuous decomposition and degradation of DMF. Figure 19 The O 1s spectra show that the surface of the d-PVDF-HFP derived SEI contains the highest levels of Li₂CO₃ and Li₂O, which is attributed to the reaction of FDMA with Li. To elucidate the inorganic composition of the SEI, we summarized the relative contents of lithium-containing species at different sputtering depths. Figure 20 As shown, the SEI formed under PVDF-HFP and d-PVDF-HFP exhibits higher signals of Li2CO3 and LiO2 at various etching depths, while LiF dominates (90%) in the SEI of d-FCPE. The dense and abundant LiF interface is beneficial for achieving stable battery cycling.

[0118] To further demonstrate the impact of dense structure and improved interfacial transport dynamics on battery performance, we tested Li|d-FCPE|NCM523 full cells under various operating scenarios.

[0119] Depend on Figure 21 It can be seen that the specific capacities of the Li|d-FCPE|NCM523 battery in Example 1 at 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2 and 3C are 177.7, 173.5, 169.9, 167.6, 164.9, 155.4, 140.6 and 130.1 mAh g, respectively. -1 Due to the high ionic conductivity and enhanced interfacial stability of d-FCPE, the discharge capacity of Li|d-FCPE|NCM523 batteries is higher than that of Li|PVDF-HFP|NCM523 and Li|d-PVDF-HFP|NCM523 batteries.

[0120] Depend on Figure 22 As can be seen, the Li|d-FCPE|NCM523 battery of Example 1 can operate at 0.5C for 1000 cycles, maintaining 83.2% capacity retention and exhibiting a high average coulombic efficiency of 99.83%. In contrast, the Li|PVDF-HFP|NCM523 and Li|d-PVDF-HFP|NCM523 batteries show faster capacity decay and lower CE.

[0121] Depend on Figure 23 It can be seen that at a higher 2C rate, the Li|d-FCPE|NCM523 battery retains 84.5% of its capacity after 1000 cycles, which is superior to d-PVDF-HFP (85% after 500 cycles and 76% after 810 cycles). The lower discharge capacity and CE of Li|PVDF-HFP|NCM523 at 2C are attributed to uncontrollable side reactions.

[0122] In summary, this invention innovatively discovers that the degree of densification of PVDF-HFP is closely related to its physicochemical and electrochemical properties. Non-dense structures result in limited mechanical strength and slow ion transport. We successfully constructed a dense perfluorinated composite electrolyte rich in the PVDF-HFP β phase by introducing polar PTFMA to modulate the solvation structure. The strong intermolecular interactions between PTFMA and PVDF-HFP units enhance mechanical strength and increase the β-phase PVDF-HFP. Furthermore, PTFMA modulates the solvation structure to promote the formation of more aggregates (AGGs), thereby promoting the LiF-rich SEI. Therefore, the d-FCPE of this invention exhibits an ionic conductivity as high as 6.1 × 10⁻⁶ at room temperature. -4 S cm -1 The assembled Li||Li symmetric cell exhibits a cycle life exceeding 3800 h, and the Li||NCM523 full cell retains 80% of its capacity after 1000 cycles at 0.5C. This invention highlights the inherent properties of high-performance SPE densification and fluorination, and provides new opportunities for developing solid-state batteries with long cycle lives.

[0123] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions, and variations to the above embodiments within the scope of the present invention. Furthermore, without contradiction, those skilled in the art can combine and integrate different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

Claims

1. A fluorinated dense composite polymer electrolyte, characterized in that, The fluorinated dense composite polymer electrolyte comprises a first fluorinated polymer, a second fluorinated polymer, a lithium salt, and a solvent; the first fluorinated polymer is a fluorinated alkyl polyalkyl acrylate, the second fluorinated polymer is a polyvinylidene fluoride polymer, and the solvent is a fluorinated alkyl amide compound; the solvent has a structure as shown in Formula 1, wherein R1 and R2 are each independently selected from C1-C3 alkyl groups or hydrogen atoms, and R3 is selected from fluorinated C1-C3 alkyl groups with ≥3 fluorine atoms; the first fluorinated polymer is obtained by polymerization of a compound as shown in Formula 2, wherein R4 is a fluorinated C1-C3 alkyl group with ≥3 fluorine atoms, and R5 is selected from C1-C3 alkyl groups; the mass percentage of the first fluorinated polymer in the fluorinated dense composite polymer electrolyte is 5-20%, the mass percentage of the second fluorinated polymer in the fluorinated dense composite polymer electrolyte is 20-60%, and the mass percentage of the lithium salt in the fluorinated dense composite polymer electrolyte is 30-60%. 。 2. The fluorinated dense composite polymer electrolyte according to claim 1, characterized in that, The first fluoropolymer R4 contains at least one perfluoromethyl group, and the solvent R3 contains at least one perfluoromethyl group; Preferably, the first fluoropolymer has a mass percentage of 7-15% in the fluorinated dense polymer electrolyte, the second fluoropolymer has a mass percentage of 30-45% in the fluorinated dense polymer electrolyte, and the lithium salt has a mass percentage of 45-55% in the fluorinated dense polymer electrolyte.

3. The fluorinated dense composite polymer electrolyte according to claim 1, characterized in that, According to claim 1, the fluorinated dense composite polymer electrolyte is characterized in that the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte comprises a solvent-separated ion pair (SSIP), a contact ion pair (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2); wherein the solvent-separated ion pair (SSIP) is the lithium salt anion that has not reacted with Li. + Direct contact; contact ion pair (CIP) is a lithium salt in which one of the anions directly interacts with Li. + Contact; Aggregate-1 (AGG-1) is an anion in a lithium salt that directly reacts with two Li... + Contact; Aggregate-2 (AGG-2) is a lithium salt in which one anion directly reacts with two or more Li groups. + touch; Preferably, the contents of solvent-separated ion pairs (SSIP), contact ion pairs (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2) in the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte are obtained by Raman spectral peak fitting. More preferably, the solvent-separated ion pairs (SSIP), contact ion pairs (CIP), aggregate-1 (AGG-1), and aggregate-2 (AGG-2) are distinguished according to the beam of the Raman spectrum, wherein the beam of the solvent-separated ion pairs (SSIP) is 715-725 cm⁻¹. -1 The beam of contact ion pair (CIP) is 726-735 cm. -1 The beam of Aggregator-1 (AGG-1) is 740-750 cm. -1 The beam of Aggregator-2 (AGG-2) is 760-770 cm. -1 ; More preferably, the molar percentage of aggregate-1 (AGG-1) and aggregate-2 (AGG-2) in the lithium salt solvation structure of the fluorinated dense composite polymer electrolyte is ≥85%.

4. The fluorinated dense composite polymer electrolyte according to claim 1, characterized in that, The β-phase content in the second fluorinated polymer of the fluorinated dense composite polymer electrolyte obtained by Fourier transform infrared spectroscopy is ≥50%, and the crystallinity of the fluorinated dense composite polymer electrolyte obtained by XRD is ≤20%.

5. The fluorinated dense composite polymer electrolyte according to claim 1, characterized in that, The polyvinylidene fluoride compounds include one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-tetrafluoroethylene copolymer (PVDF-TFE), and polyvinylidene fluoride-trifluorochloroethylene copolymer (PVDF-CTFE); Preferably, the polyalkyl acrylate fluorinated alkyl ester comprises one or more of the following: poly(trifluoroethyl methacrylate), poly(trifluoroethyl methacrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), poly(2,2,3,3-tetrafluoropropyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate), poly(2,2,3,3,3-pentafluoropropyl methacrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), poly(hexafluorobutyl methacrylate), and poly(hexafluorobutyl methacrylate). Preferably, the fluorinated alkylamide compound includes one or more of 2,2,2-trifluoro-N,N-dimethylacetamide and 2,2,2-trifluoroacetamide; More preferably, the first fluoropolymer is poly(trifluoroethyl methacrylate) (PTFMA), the second fluoropolymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), the lithium salt is lithium bisfluorosulfonylimide (LiFSI), and the solvent is 2,2,2-trifluoro-N,N-dimethylacetamide (FDMA).

6. The fluorinated dense composite polymer electrolyte according to claim 1, characterized in that, The fluorinated dense composite polymer electrolyte possesses at least one of the following characteristics: (1) The surface roughness R of the fluorinated dense composite polymer electrolyte was measured by atomic force microscopy (AFM). a ≤40 nm; (2) The tensile strength of the fluorinated dense composite polymer electrolyte is >3.8 MPa, the elongation at break is >350%, and the toughness is >15 MJ / m. -3 ; (3) The electrochemical stability window of the fluorinated dense composite polymer electrolyte is >4.7 V; (4) The room temperature ionic conductivity of the fluorinated dense composite polymer electrolyte is >5×10⁻⁶. -3 S cm -1 ; (5) The shear strength of the fluorinated dense composite polymer electrolyte obtained by the overlap shear test is >30 kPa; (6) The battery Li prepared from the fluorinated dense composite polymer electrolyte + Migration number ≥ 0.

45.

7. A method for preparing the fluorinated composite polymer electrolyte according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Under an inert atmosphere, the first fluoropolymer, the second fluoropolymer, and the lithium salt are dissolved in a solvent according to the target stoichiometric ratio; the first fluoropolymer, the second fluoropolymer, and the lithium salt constitute 0.8% to 30% of the solvent mass during the dissolution process. S2: Pour the solution obtained in S1 into a container and dry it at 20~100 °C for 4~24 h. Evaporate the solvent to obtain fluorinated dense composite polymer electrolyte.

8. The preparation method according to claim 7, characterized in that, The dissolution temperature in S1 is 20~100 °C; Preferably, in step S1, the inert atmosphere includes helium, neon, argon, and nitrogen, wherein the water content and oxygen content are both less than 0.1 ppm.

9. The preparation method according to claim 7, characterized in that, In step S2, the drying temperature is 60 °C and the drying time is 12 h. Preferably, the residual solvent content after drying is less than 15% of the mass ratio of the fluorinated dense composite polymer electrolyte.

10. A solid-state battery, characterized in that, The electrolyte comprises a positive electrode, a negative electrode, and an electrolyte layer located between the positive electrode and the negative electrode, wherein the electrolyte layer comprises the fluorinated dense composite polymer electrolyte according to any one of claims 1-6 or the fluorinated dense composite polymer electrolyte prepared by the preparation method according to any one of claims 7-9.

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