Fluorine-doped latp composite solid electrolyte membrane, and preparation method and application thereof
Fluorine-doped LATP solid electrolytes were prepared by mechanical assistance and segmented sintering, and combined with electrochemically induced curing technology. This solved the problems of uneven LATP preparation and poor interfacial contact, and achieved a composite solid electrolyte membrane with high ionic conductivity and good mechanical properties, which is suitable for solid-state lithium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LUDONG UNIVERSITY
- Filing Date
- 2026-04-03
- Publication Date
- 2026-06-16
AI Technical Summary
Existing LATP preparation methods suffer from uneven mixing and insufficient reaction, resulting in numerous impurities and uneven particle size, which affect ionic conductivity and dispersibility. Furthermore, traditional interface optimization methods are complex, costly, and difficult to achieve good solid-solid contact between the electrolyte membrane and the electrode.
Fluorine-doped LATP solid electrolyte was prepared by mechanical assistance and segmented sintering. The interfacial contact was optimized by electrochemically induced curing technology. Film was formed in air by combining high solid content slurry preparation method. Fluorine-doped LATP was then composited with a framework-supporting polymer to achieve high ionic conductivity and good mechanical flexibility.
It significantly improves the phase purity and particle uniformity of LATP, enhances the ionic conductivity and interfacial stability of the electrolyte membrane, achieves high cycle stability and mechanical flexibility, simplifies the preparation process, reduces costs, and is suitable for solid-state lithium batteries.
Smart Images
Figure CN122224922A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a fluorine-doped LATP composite solid electrolyte membrane, its preparation method and application, belonging to the field of solid electrolyte technology for lithium-ion batteries. Background Technology
[0002] Lithium metal batteries are considered a key direction for next-generation high-energy-density energy storage systems due to their high theoretical energy density (>500 Wh / kg) and low electrode potential (-3.04 V). However, traditional liquid electrolytes pose safety hazards such as leakage and flammability / explosion, severely limiting their application in high-safety-requirement scenarios such as new energy vehicles and energy storage power stations. Solid-state electrolytes, with their high mechanical strength, excellent thermal stability, and chemical stability, are considered a key approach to solving these problems.
[0003] Solid-state electrolytes are mainly divided into two categories: inorganic ceramic electrolytes (ICE) and organic polymer electrolytes (SPE). Examples of ICE include Li1.3Al0.3Ti1.7(PO4)3 (LATP) and Li7La3Zr2O. 12 (LLZO) and others have high room temperature ionic conductivity (10) -4 ~10 - ³ S / cm), but its intrinsic brittleness and poor solid-solid interface contact with the electrode lead to high interfacial impedance and poor cycle stability. SPEs such as polyethylene oxide (PEO) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) have good flexibility and processability, but low room temperature ionic conductivity (<10). -5 (S / cm), and even needs to operate at high temperatures of 50~70℃. Inorganic-polymer composite solid electrolytes (CSPEs) combine the advantages of both and have become a research hotspot in the field of solid electrolytes.
[0004] In terms of inorganic filler selection, LATP is considered one of the most promising fillers due to its high ionic conductivity, wide electrochemical window, and good air stability. However, existing LATP preparation methods have significant drawbacks: traditional solid-phase methods result in uneven mixing and incomplete reaction of raw materials, leading to numerous impurities (such as TiO2 and AlPO4 residues) and uneven particle size, which severely affects ionic conductivity and dispersion uniformity in polymers; while wet chemical methods such as sol-gel methods can improve particle uniformity, they are complex, costly, and have low yields, making large-scale production difficult.
[0005] In terms of interface optimization, achieving good solid-solid contact between the electrolyte membrane and the electrode is the core bottleneck of solid-state batteries. Existing technologies mainly adopt the following strategies: (1) Hot pressing: The electrolyte membrane and the electrode are physically bonded by high temperature and high pressure, but this can easily lead to membrane deformation and rupture, resulting in uneven interface contact; (2) Adding plasticizers: Ionic liquids or carbonate plasticizers are added to the electrolyte membrane to improve interface wettability, but this will reduce mechanical strength and there is a risk of consumption or leakage of plasticizers during long-term cycling; (3) In-situ curing of liquid precursors: Polymerizable monomers and initiators are injected into the battery and cured in-situ by thermal polymerization or photopolymerization. Although good interface contact can be achieved, the precursor injection process is complex and has problems such as monomer residue, uneven polymerization, and poor consistency. In addition, external initiators or special light conditions are required, which increases the complexity and cost of the process. Summary of the Invention
[0006] This invention provides a fluorine-doped LATP composite solid electrolyte membrane, its preparation method, and its application to solve the technical problems existing in the prior art as described above.
[0007] The technical solution provided by this invention is as follows: One of the objectives of this invention is to provide a fluorine-doped LATP composite solid electrolyte membrane, comprising the following components: fluorine-doped LATP solid electrolyte, framework support polymer, and lithium salt; wherein the mass ratio of lithium salt: framework support polymer: fluorine-doped LATP solid electrolyte is (0.15~0.6):1:(0.15~0.6).
[0008] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the skeleton support polymer is polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP); the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), or lithium difluorooxalate borate (LiBOB).
[0009] The second objective of this invention is to provide a method for preparing the fluorine-doped LATP composite solid electrolyte membrane as described above, comprising the following steps: (1) Preparation of fluorine-doped LATP solid electrolyte: Fluorine-doped LATP solid electrolyte was prepared by mechanical assistance and segmented sintering method; (2) Preparation of high solid content slurry: Fluorine-doped LATP solid electrolyte, framework-supporting polymer and lithium salt are added to organic solvent and stirred at room temperature for 2-4 hours to form an electrolyte slurry with a solid content of 15-60 wt%. (3) Casting film in air environment: In an air environment, the electrolyte slurry obtained in step (2) is injected into the mold and dried at 40~80℃ for 1~4h to obtain a fluorine-doped LATP composite solid electrolyte film.
[0010] Furthermore, the organic solvent in step (2) is N-methylpyrrolidone (NMP).
[0011] Furthermore, the preparation of the fluorine-doped LATP solid electrolyte in step (1) specifically includes the following steps: S1: First mechanically assisted grinding: Lithium source, aluminum source, titanium source and phosphorus source are mixed in a molar ratio of (1.3~1.8):0.3:1.7:3 and subjected to the first mechanical grinding under energy-assisted conditions to obtain LATP precursor powder; S2: First segment sintering: The LATP precursor powder obtained in step S1 is pre-sintered at 300~500℃ for 1~4h to obtain the pre-sintered product. S3: Second mechanically assisted grinding: The pre-calcined product obtained in step S2 is mechanically ground again under energy-assisted conditions to obtain homogenized pre-calcined powder; S4: Second-stage sintering: The homogenized pre-calcined powder obtained in step S3 is subjected to a second sintering treatment at 600~900℃ for 6~9h, and then naturally cooled to room temperature to obtain LATP solid electrolyte with a particle size distribution of 0.3~0.8μm; S5: Fluorine doping modification: The LATP solid electrolyte obtained in step S4 is mixed with fluoride and subjected to a third mechanical grinding under energy-assisted conditions to obtain fluorine-doped LATP precursor powder. The precursor powder is then subjected to a third sintering treatment at 200~700℃ for 2~6h, naturally cooled to room temperature, and ground to obtain fluorine-doped LATP solid electrolyte.
[0012] Furthermore, in step S5, the mass ratio of LATP solid electrolyte to fluoride is 9:1, and the fluoride is lithium fluoride.
[0013] Furthermore, the energy assistance is infrared light heating; the grinding is at least one of manual grinding, ball milling, and sand milling.
[0014] The third objective of this invention is to provide an electrochemically induced curing lithium battery, comprising the fluorine-doped LATP composite solid electrolyte membrane as described above or the fluorine-doped LATP composite solid electrolyte membrane prepared by the preparation method described above.
[0015] The fourth objective of this invention is to provide a method for preparing an electrochemically induced curing lithium battery as described above, comprising the following steps: U1: Battery assembly: The fluorine-doped LATP composite solid electrolyte membrane is left to stand, allowing the ionic liquid inside the membrane to seep out and the membrane surface to change from a dry state to an oil film state. Then, in a glove box filled with argon, it is placed between the positive and negative electrode plates to assemble a lithium battery. U2: Thermal aging treatment: The assembled lithium battery is left to stand at 25~60℃ for 10~24h, and then cooled to room temperature; U3: Electrochemical induced curing: The lithium battery after thermal aging is activated by charge-discharge cycles and the composite film is cured in situ. The voltage of the charge-discharge cycle activation is 2.5~4.1 V.
[0016] Furthermore, the oxygen level in the glove box is <0.01ppm.
[0017] Furthermore, the positive electrode is a lithium iron phosphate positive electrode; the negative electrode is a lithium metal sheet.
[0018] The technical solution provided by this invention has the following advantages compared with the prior art: (1) Preparation of high-purity and high-uniformity LATP by mechanically assisted segmented sintering process: Through the synergistic process design of “first mechanically assisted grinding → first segmented sintering → second mechanically assisted grinding → second segmented sintering”, the phase purity of LATP is significantly improved, the generation of impurity phases such as TiO2 and AlPO4 is effectively reduced, and the particle size of LATP particles is precisely controlled at 0.3~0.8μm and uniformly distributed. The particle surface has abundant Lewis acidic active sites, which provides an ideal filler basis for the preparation of high solid content composite films and electrochemically induced curing.
[0019] (2) Fluorine doping simultaneously improves ionic conductivity and interfacial stability: Fluorine doping not only improves the intrinsic ionic conductivity of LATP, but also promotes the formation of a LiF-rich stable layer at the interface during electrochemically induced solidification, inhibiting lithium dendrite growth and enabling the solid-state battery to operate stably for long cycles; according to the test, the reversible capacity of the solid-state battery after 1000 cycles at room temperature at a current rate of 0.5 C is 107 mAh g. -1 The above represents a capacity retention rate of 93.04%.
[0020] (3) Electrochemical induced curing technology optimizes interface contact: This invention is the first to apply electrochemical induced curing technology to composite solid electrolyte membrane system, realizes in-situ curing and stabilization of electrode-electrolyte interface, and effectively solves the industry problem of poor solid-solid interface contact between traditional solid electrolyte and electrode.
[0021] (4) Synergistic innovation of energy-assisted method and electrochemically induced curing: Fluorine-doped LATP prepared by energy-assisted method has the characteristics of uniform particle size and high surface activity, providing ideal reaction sites for electrochemically induced curing; electrochemically induced curing further optimizes the interfacial bonding of fluorine-doped LATP, polymer matrix and electrode. The synergistic effect of the two makes the composite film have both high ionic conductivity and good cycling stability, with a room temperature ionic conductivity as high as 2.49×10 -4S / cm, with significant synergistic gain.
[0022] (5) Stable preparation of high solid content composite membrane in air environment: This invention utilizes fluorine-doped LATP with uniform particle size to achieve the preparation of composite solid electrolyte membrane with solid content of 15~60wt% in air environment without the need for inert atmosphere protection, breaking through the technical bottleneck of traditional composite electrolytes being sensitive to water and oxygen, greatly simplifying the process and reducing the preparation cost.
[0023] (6) The composite membrane has both high ionic conductivity and good mechanical flexibility: By combining high solid content fluorine-doped LATP with the backbone support polymer, the electrolyte membrane has high ionic conductivity, good tensile strength and fracture strain at room temperature, which improves the overall performance of the composite electrolyte membrane and can meet the assembly requirements of solid-state batteries.
[0024] (7) It can directly replace commercial separators and has broad industrialization prospects: The composite membrane prepared by this invention can be directly applied to solid-state lithium batteries without the addition of liquid electrolyte. After electrochemical induction curing, it has excellent cycle stability and can directly replace traditional commercial separators. It has broad application prospects in new energy vehicles, drones, and androids and has strong industrialization potential. Attached Figure Description
[0025] Figure 1 This is a morphology diagram of the LATP solid electrolyte powder prepared in step S4 of Example 1 of the present invention; Figure 2 This is a morphology diagram of the fluorine-doped LATP solid electrolyte powder prepared in step S5 of Example 1 of the present invention; Figure 3 SEM image of the LATP solid electrolyte prepared in step S4 of Example 1 of the present invention; Figure 4 This is a particle size distribution diagram of the LATP solid electrolyte prepared in step S4 of Example 1 of the present invention; Figure 5 This is an SEM image of the fluorine-doped LATP solid electrolyte prepared in step S5 of Example 1 of the present invention. Figure 6 Figure 1 shows a SEM-EDS image of the fluorine-doped LATP solid electrolyte prepared in step S5 of Example 1 of the present invention; wherein, Figure 1a is an elemental mapping diagram of the fluorine-doped LATP solid electrolyte prepared in step S5 of Example 1, and Figures 1b-1f are the elemental distribution diagrams of Li, Al, P, O and F, respectively. Figure 7 The XRD patterns of the LATP solid electrolytes prepared in Examples 1 and 9-12 of this invention are shown. Figure 8The XRD patterns of the fluorine-doped LATP solid electrolytes prepared in Examples 1 and 13-17 of this invention are shown. Figure 9 The stress-strain curves of the fluorine-doped LATP composite solid electrolyte membranes prepared in Examples 2-5 of this invention are shown. Figure 10 The stress-strain curves are shown for the composite solid electrolyte membranes prepared in Comparative Examples 2-5 of this invention. Figure 11 This is a charge-discharge cycle activation test diagram of the electrochemically induced curing lithium battery of Example 20 of the present invention; Figure 12 This is a charge-discharge cycle activation test diagram of the electrochemically induced curing lithium battery of Comparative Example 7 of the present invention. Figure 13 These are comparative images of the fluorine-doped LATP composite solid electrolyte membrane prepared in Example 2 of this invention in its dry state, oil film state, and after electrochemically induced curing. Figure 14 The IT curve of the fluorine-doped LATP composite solid electrolyte membrane prepared in Example 2 of this invention is shown. Figure 15 The IT curve of the fluorine-doped LATP composite solid electrolyte membrane prepared in Example 4 of this invention is shown. Figure 16 This is a SEM image of the LATP solid electrolyte prepared in step S4 of Comparative Example 1 of the present invention. Detailed Implementation
[0026] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.
[0027] Example 1 A method for preparing fluorine-doped LATP solid electrolyte specifically includes the following steps: S1: First grinding: 1.1730g of lithium nitrate, 1.1252g of aluminum nitrate, 5.7800g of tetrabutyl titanate and 3.4506g of ammonium dihydrogen phosphate (the molar ratio of lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate is 1.7:0.3:1.7:3) were added to an agate mortar containing 20 mL of deionized water and manually ground under the condition of a tungsten filament infrared lamp to obtain white LATP precursor powder; S2: First sintering: The LATP precursor powder obtained in step S1 is pre-sintered at 400℃ for 2 hours to obtain the pre-sintered product; S3: Second grinding: The pre-calcined product obtained in step S2 is manually ground again under the condition of tungsten filament infrared lamp to obtain homogenized pre-calcined powder; S4: Second sintering: The homogenized pre-calcined powder obtained in step S3 is subjected to a second sintering treatment at 800℃ for 8 hours, and then naturally cooled to room temperature to obtain LATP solid electrolyte. S5: Fluorine doping modification: The LATP solid electrolyte obtained in step S4 was placed in an agate mortar and lithium fluoride was added (the mass ratio of LATP solid electrolyte to lithium fluoride was 9:1). The mixture was manually ground under the irradiation of a tungsten filament infrared lamp to obtain fluorine-doped LATP precursor powder. Then, it was sintered at 400℃ for 4 hours, naturally cooled to room temperature, and ball-milled to obtain fluorine-doped LATP solid electrolyte.
[0028] like Figure 1 As shown, the LATP solid electrolyte powder prepared in step S4 of Example 1 is pure white and has no obvious lumps; Figure 2 As shown, the fluorine-doped LATP solid electrolyte powder prepared in step S5 of this embodiment is light beige and has no obvious lumps.
[0029] Example 2 A method for preparing a fluorine-doped LATP composite solid electrolyte membrane includes the following steps: (1) Preparation of high solid content slurry: Weigh 1.0g of PVDF-HFP and add it to a crucible containing 8mL of NMP. Stir until it is completely colorless and transparent. Weigh 0.45g of fluorine-doped LATP solid electrolyte and 0.3g of LiTFSI obtained in Example 1 and add them to the above crucible. Stir continuously at room temperature for 3h to form a milky white turbid slurry. Then place it in a cool and dry place to stand and remove air bubbles to obtain electrolyte slurry. (2) Casting film in air environment: In an air environment, 0.2 mL of electrolyte slurry was extracted using a glass syringe and poured into a mold with a diameter of 20.0 mm and a depth of 3.2 mm. The film was dried at 80°C for 2 h to obtain a fluorine-doped LATP composite solid electrolyte membrane.
[0030] Example 3 The difference from Example 2 is that the amount of LiTFSI used is 0.15g.
[0031] Example 4 The difference from Example 2 is that the amount of LiTFSI used is 0.45g.
[0032] Example 5 The difference from Example 2 is that the amount of LiTFSI used is 0.6g.
[0033] Example 6 The difference from Example 2 is that the amount of fluorine-doped LATP solid electrolyte used is 0.15g.
[0034] Example 7 The difference from Example 2 is that the amount of fluorine-doped LATP solid electrolyte used is 0.3g.
[0035] Example 8 The difference from Example 2 is that the amount of fluorine-doped LATP solid electrolyte used is 0.6g.
[0036] Example 9 The difference from Example 1 is that the molar ratio of lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate is 1.3:0.3:1.7:3.
[0037] Example 10 The difference from Example 1 is that the molar ratio of lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate is 1.4:0.3:1.7:3.
[0038] Example 11 The difference from Example 1 is that the molar ratio of lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate is 1.6:0.3:1.7:3.
[0039] Example 12 The difference from Example 1 is that the molar ratio of lithium nitrate, aluminum nitrate, tetrabutyl titanate and ammonium dihydrogen phosphate is 1.8:0.3:1.7:3.
[0040] Example 13 The difference from Example 1 is that in step (5), the sintering temperature is 200°C.
[0041] Example 14 The difference from Example 1 is that in step (5), the sintering temperature is 300°C.
[0042] Example 15 The difference from Example 1 is that in step (5), the sintering temperature is 500°C.
[0043] Example 16 The difference from Example 1 is that in step (5), the sintering temperature is 600°C.
[0044] Example 17 The difference from Example 1 is that in step (5), the sintering temperature is 700°C.
[0045] Example 18 The difference from Example 2 is that the lithium salt LiTFSI is replaced with LiBOB.
[0046] Example 19 The difference from Example 2 is that the lithium salt LiTFSI is replaced with LiFSI.
[0047] Example 20 A method for preparing an electrochemically induced curing lithium battery includes the following steps: U1: The fluorine-doped LATP composite solid electrolyte membrane prepared in Example 2 was left to stand, allowing the ionic liquid inside the membrane to seep out and the membrane surface to change from a dry state to an oil film state. Then, in a glove box filled with argon (water oxygen value < 0.01 ppm), it was placed between the lithium iron phosphate positive electrode and the lithium metal negative electrode to assemble a solid lithium battery. U2: Thermal aging treatment: The assembled lithium battery is left to stand at 60°C for 12 hours, and then cooled to room temperature; U3: Electrochemically induced curing: Under the conditions of voltage of 2.5~4.1V and temperature of 25℃, the thermally aged lithium battery was first subjected to charge-discharge cycle activation and in-situ curing test of composite film three times at a current rate of 0.2C, and then subjected to charge-discharge cycle test at a current rate of 0.5C to obtain the electrochemically induced cured lithium battery.
[0048] Comparative Example 1 The difference from Example 1 is that neither of the manual grinding operations was performed under tungsten filament infrared lamp conditions.
[0049] SEM images of the LATP solid electrolyte prepared in step S4 of Comparative Example 1 are shown below. Figure 16 As shown, SEM characterization revealed that the particle size distribution was 0.5~2μm, with larger particle size, irregular morphology, and poor dispersibility, which could not meet the requirements of fillers for high-performance composite solid electrolytes.
[0050] Comparative Example 2 The difference from Example 2 is that no fluorine-doped LATP solid electrolyte is added.
[0051] Comparative Example 3 The difference from Example 3 is that no fluorine-doped LATP solid electrolyte is added.
[0052] Comparative Example 4 The difference from Example 4 is that no fluorine-doped LATP solid electrolyte is added.
[0053] Comparative Example 5 The difference from Example 5 is that no fluorine-doped LATP solid electrolyte is added.
[0054] Comparative Example 6 The difference from Example 2 is that the fluorine-doped LATP solid electrolyte is replaced with the LATP solid electrolyte prepared in step (4) of Example 1.
[0055] Comparative Example 7 The difference from Example 20 is that no heat aging treatment was performed.
[0056] Comparative Example 8 The difference from Example 20 is that the lithium iron phosphate cathode is replaced with a ternary material cathode.
[0057] like Figure 3 and Figure 4 As shown, the SEM image and particle size distribution characterization of the LATP solid electrolyte prepared in step S4 of Example 1 show that its average particle size is 0.3~0.8μm, the morphology is mainly brick-shaped, the particle shape is regular and the particle size distribution is uniform, which provides a high-quality matrix material for subsequent fluorine doping modification.
[0058] like Figure 5 and Figure 6 As shown, the SEM image, SEM-EDS image and elemental mapping image of the fluorine-doped LATP solid electrolyte prepared in step S5 of Example 1 indicate that the five elements Li, Al, P, O and F are uniformly distributed in the matrix, proving that the fluorine element has been successfully doped and modified.
[0059] like Figure 7 As shown, the XRD patterns of the LATP solid electrolytes prepared in Examples 1 and 9-12 all correspond to the diffraction peaks on PDF card #35-0754, indicating that pure-phase LATP solid electrolytes were successfully synthesized.
[0060] like Figure 8 As shown, the diffraction peaks detected by the XRD patterns of the LATP solid electrolytes prepared in Examples 1 and 13-17 all correspond to PDF card #35-0754, indicating that pure-phase LATP solid electrolytes were successfully synthesized, and no TiO2 or AlPO4 impurities were found, indicating high purity; in addition, the LiF characteristic peaks are clear and obvious, and no obvious impurity phases are generated.
[0061] like Figure 11 and Figure 12 As shown, Example 2 and Comparative Example 7 underwent long-cycle testing of solid-state batteries at room temperature and a current rate of 0.5 C. Compared to Comparative Example 7, which did not undergo thermal aging, Example 2 exhibited a reversible specific capacity of 107 mAh g⁻¹ after 1000 cycles at a current rate of 0.5 C. -1 The above (Comparative Example 7) showed a reversible specific capacity of less than 40 mAh g after 150 cycles. -1 The capacity retention rate is as high as 93.04% (at a current rate of 0.5 C, the first discharge specific capacity is 115.1 mAhg). -1 The discharge specific capacity after 1000 cycles is 107.1 mAh g.-1 Capacity retention rate = (Specific capacity of the last charge / discharge cycle / Specific capacity of the first charge / discharge cycle).
[0062] like Figure 13 As shown, when the composite solid electrolyte membrane is first prepared, the membrane is in a dry state. After standing for a period of time, the components in the air, such as water molecules, interact with the lithium salt and other ionic liquid inside the composite solid electrolyte membrane, causing the membrane surface to change from a dry state to an oil film state. The ionic liquid on the surface of the composite solid electrolyte membrane can promote the interfacial compatibility between the electrolyte membrane and the electrode. After electrochemically induced curing, the composite solid electrolyte membrane completes the in-situ curing process in the solid battery.
[0063] like Figure 14 and Figure 15 The figures show the IT curves of Examples 2 and 4 tested at room temperature. Compared with Comparative Examples 2 and 4, the addition of fluorine-doped LATP solid electrolyte in Examples 2 and 4 effectively improved the lithium-ion transference number of the composite solid electrolyte membrane at room temperature (0.647 for Example 2 and 0.494 for Example 4) and reduced its polarization.
[0064] Testing of fluorine-doped LATP solid electrolyte membranes: 1. Electrochemical impedance spectroscopy and ionic conductivity testing A stainless steel sheet | solid electrolyte membrane | stainless steel sheet button cell was assembled in air, and its electrochemical impedance was measured at 25°C. This invention utilizes a ChI660e electrochemical workstation with a frequency range of 0.1~10. 6 The voltage amplitude was 10 mV and the frequency was Hz. Ionic conductivity was calculated using the formula σ = L / (R·S), where σ is the ionic conductivity, L is the electrolyte thickness, R is the electrolyte impedance, and S is the effective contact area between the solid electrolyte and the stainless steel sheet. The test results are shown in Table 1.
[0065] Table 1 Electrochemical impedance spectroscopy and ionic conductivity test data
[0066] As shown in Table 1, compared with Comparative Examples 2-5, the addition of fluorine-doped LATP in Examples 2-8 effectively improved the ionic conductivity of the solid electrolyte membrane itself, reaching a maximum of 2.49 × 10⁻⁶. -4 S / cm; Compared with Comparative Example 6, the composite solid electrolyte membrane prepared by fluorine-doped LATP in Example 2 has an ionic conductivity of (2.49 × 10⁻⁶) / cm. -4 The S / cm ratio is much higher than that of the undoped LATP composite solid electrolyte (5.20 x 10). -5 S / cm).
[0067] 2. Assemble lithium metal sheet / solid electrolyte membrane / lithium metal sheet button cell in a vacuum glove box and measure the IT curve at 25°C. This invention uses a UNIVERSAL model glove box filled with argon gas, where the water and oxygen levels are both less than 0.01 ppm. This invention uses a ChI660e model electrochemical workstation with a voltage amplitude of 10 mV. The IT curve is obtained using formula t. Li+ =I ss (△V-I0R0) / I0(△VI) ss R ss Calculate the ion transport number, where t Li+ Here, R0 and R are the ion transport number, ΔV is the bias potential in V, and R0 is the bias voltage. SS These are the resistances before and after polarization, respectively, in Ω, I0 and I. SS Let be the initial current and the steady-state current, respectively, in A. The results are shown in Table 2.
[0068] Table 2 Ion transport number test data
[0069] As can be seen from Table 2, by comparing Examples 2 and 4 with Comparative Examples 2 and 4, the addition of fluorine-doped LATP can effectively improve the ion transference number of the composite solid electrolyte membrane at room temperature (the ion transference number of Example 2 is 0.647 and the ion transference number of Example 4 is 0.494), while Comparative Examples 2 and 4, which do not contain fluorine-doped LATP, exhibit severe polarization at room temperature and cannot be used normally.
[0070] 3. Tensile strength and fracture strain performance testing The tests were conducted using a WDW-30 microcomputer-controlled dual-column electronic universal testing machine, referring to GB / T 1040.2-2006. The test results are as follows: Figure 9 and Figure 10 And as shown in Table 3.
[0071] Table 3 Tensile strength and fracture strain rate test data
[0072] From Table 3 and Figure 9 and Figure 10 As can be seen from the table, the addition of fluorine-doped LATP in Examples 2-5 effectively improves the tensile strength and fracture strain of the composite electrolyte membrane, thus enhancing its mechanical properties. Furthermore, considering the conductivity of Examples 2-5 and Comparative Examples 2-5 in Table 1, the composite electrolyte membrane prepared by the method of this invention exhibits significantly better overall performance than the comparative examples, demonstrating that the addition of fluorine-doped LATP effectively improves the overall performance of the composite electrolyte membrane and has broader application prospects.
[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A fluorine-doped LATP composite solid electrolyte membrane, characterized in that, It comprises the following components: fluorine-doped LATP solid electrolyte, framework-supporting polymer and lithium salt; wherein the mass ratio of lithium salt: framework-supporting polymer: fluorine-doped LATP solid electrolyte is (0.15~0.6):1:(0.15~0.6).
2. The fluorine-doped LATP composite solid electrolyte membrane according to claim 1, characterized in that, The skeletal support polymer is polyvinylidene fluoride-hexafluoropropylene copolymer; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, or lithium difluorooxalate borate.
3. A method for preparing a fluorine-doped LATP composite solid electrolyte membrane as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of fluorine-doped LATP solid electrolyte: Fluorine-doped LATP solid electrolyte was prepared by mechanical assistance and segmented sintering method; (2) Preparation of high solid content slurry: Fluorine-doped LATP solid electrolyte, framework-supporting polymer and lithium salt are added to organic solvent and stirred at room temperature for 2-4 hours to form an electrolyte slurry with a solid content of 15-60 wt%. (3) Casting film in air environment: In an air environment, the electrolyte slurry obtained in step (2) is injected into the mold and dried at 40~80℃ for 1~4h to obtain a fluorine-doped LATP composite solid electrolyte film.
4. The method for preparing the fluorine-doped LATP composite solid electrolyte membrane according to claim 3, characterized in that, The preparation of fluorine-doped LATP solid electrolyte in step (1) specifically includes the following steps: S1: First mechanically assisted grinding: Lithium source, aluminum source, titanium source and phosphorus source are mixed in a molar ratio of (1.3~1.8):0.3:1.7:3 and subjected to the first mechanical grinding under energy-assisted conditions to obtain LATP precursor powder; S2: First segment sintering: The LATP precursor powder obtained in step S1 is pre-sintered at 300~500℃ for 1~4h to obtain the pre-sintered product. S3: Second mechanically assisted grinding: The pre-calcined product obtained in step S2 is mechanically ground again under energy-assisted conditions to obtain homogenized pre-calcined powder; S4: Second-stage sintering: The homogenized pre-calcined powder obtained in step S3 is subjected to a second sintering treatment at 600~900℃ for 6~9h, and then naturally cooled to room temperature to obtain LATP solid electrolyte with a particle size distribution of 0.3~0.8μm; S5: Fluorine doping modification: The LATP solid electrolyte obtained in step S4 is mixed with fluoride and subjected to a third mechanical grinding under energy-assisted conditions to obtain fluorine-doped LATP precursor powder. The precursor powder is then subjected to a third sintering treatment at 200~700℃ for 2~6h, naturally cooled to room temperature, and ground to obtain fluorine-doped LATP solid electrolyte.
5. The method for preparing a fluorine-doped LATP composite solid electrolyte membrane according to claim 3, characterized in that, The organic solvent in step (2) is N-methylpyrrolidone.
6. The method for preparing the fluorine-doped LATP composite solid electrolyte membrane according to claim 4, characterized in that, The energy assistance is infrared light heating; the grinding is at least one of manual grinding, ball milling and sand milling; in step S5, the mass ratio of LATP solid electrolyte to fluoride is 9:1, and the fluoride is lithium fluoride.
7. An electrochemically induced curing lithium battery, characterized in that, This includes the fluorine-doped LATP composite solid electrolyte membrane as described in claim 1 or 2, or the fluorine-doped LATP composite solid electrolyte membrane prepared by the preparation method described in any one of claims 3-6.
8. A method for preparing an electrochemically induced curing lithium battery as described in claim 7, characterized in that, Includes the following steps: U1: Battery assembly: The fluorine-doped LATP composite solid electrolyte membrane is left to stand, allowing the ionic liquid inside the membrane to seep out and the membrane surface to change from a dry state to an oil film state. Then, in a glove box filled with argon, it is placed between the positive and negative electrode plates to assemble a lithium battery. U2: Thermal aging treatment: The assembled lithium battery is left to stand at 25~60℃ for 10~24h, and then cooled to room temperature; U3: Electrochemical induced curing: The lithium battery after thermal aging is activated by charge-discharge cycles and the composite film is cured in situ. The voltage of the charge-discharge cycle activation is 2.5~4.1 V.
9. The method for preparing an electrochemically induced curing lithium battery according to claim 8, characterized in that, The oxygen level in the glove box is <0.01ppm.
10. The method for preparing an electrochemically induced curing lithium battery according to claim 8, characterized in that, The positive electrode is a lithium iron phosphate positive electrode; the negative electrode is a lithium metal sheet.