A high ionic conductivity solid-state electrolyte separator and a preparation method and application thereof

Abstract

The application discloses a high-ionic-conductivity solid-state electrolyte diaphragm and a preparation method and application thereof, and relates to the technical field of batteries. The preparation method of the high-ionic-conductivity solid-state electrolyte diaphragm comprises the following steps: dissolving a polyimide precursor in a solvent 1 to obtain a spinning solution, performing electrostatic spinning, and then solidifying to obtain a polyimide-based film; dispersing electrolyte particles in a solvent 2 to obtain a suspension, immersing the polyimide-based film in the suspension, and then drying to obtain a polyimide-based film filled with the electrolyte particles; mixing monomers, a lithium salt, an initiator and a solvent 3 to prepare a prepolymer solution, coating the prepolymer solution on the polyimide-based film filled with the electrolyte particles, and then performing thermal polymerization treatment to obtain the solid-state electrolyte diaphragm. The application solves the problem that mechanical performance, processability and high ionic conductivity cannot be simultaneously considered.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a solid electrolyte separator with high ionic conductivity, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for efficient and safe energy storage devices, lithium-ion batteries, as the current mainstream energy storage technology, are continuously developing towards higher energy density and higher safety performance. In this development trend, all-solid-state lithium batteries, with their superior thermal stability and potential high energy density, are considered a key research direction for next-generation energy storage systems. Compared to traditional liquid electrolyte systems, all-solid-state lithium batteries have significant advantages in safety, effectively avoiding battery accidents caused by safety hazards such as electrolyte flammability and leakage.

[0003] However, despite the numerous advantages of all-solid-state lithium batteries, the practical application of their solid-state electrolyte materials faces many challenges. Firstly, some inorganic solid-state electrolytes, such as Li... 10 GeP2S 12 Sulfides, due to their brittle and hard texture and poor processing properties, are difficult to integrate effectively with existing battery manufacturing processes. This not only increases production difficulty but also limits the widespread application of solid-state electrolytes in battery manufacturing.

[0004] Secondly, the insufficient mechanical properties of solid electrolyte membranes are also a key factor restricting their development. Due to the poor flexibility of solid electrolyte membranes, they are difficult to meet the requirements of high-precision coating, pressing, and other manufacturing processes, which further limits the application of solid-state lithium batteries in high-performance and high-precision fields.

[0005] Furthermore, poor contact between the solid electrolyte and electrode interface is also a current research challenge. Poor interfacial contact can lead to a decline in electrochemical performance, affecting the overall performance and stability of the battery.

[0006] Finally, cost is also a significant factor restricting the large-scale application of solid-state electrolytes. Existing preparation processes are complex and costly, posing a considerable challenge to the commercialization of solid-state electrolytes.

[0007] To address the aforementioned issues, existing research has attempted to improve the performance of solid-state electrolyte membranes through fiber reinforcement, electrolyte particle filling, or polymer modification. For example, Chinese patent application CN111234567A discloses a method for modifying sulfide solid-state electrolytes using composites. However, while this method improves the performance of solid-state electrolytes to some extent, the preparation process remains relatively complex, and the mechanical properties still need improvement. Traditional polymer electrolyte membranes, although offering good flexibility, suffer from low ionic conductivity, making it difficult to meet the high requirements of high-rate batteries for electrolyte materials.

[0008] In summary, there is an urgent need for a new type of solid electrolyte membrane that can improve mechanical properties and processability while also possessing high ionic conductivity, in order to meet the development needs of high-energy-density and high-safety batteries. Summary of the Invention

[0009] The technical problem to be solved by the present invention is that existing solid electrolyte membranes cannot simultaneously achieve mechanical properties, processability, and high ionic conductivity. The purpose is to provide a solid electrolyte membrane with high ionic conductivity, its preparation method, and its application, thereby solving the problem of not being able to simultaneously achieve mechanical properties, processability, and high ionic conductivity.

[0010] This invention is achieved through the following technical solution:

[0011] In a first aspect, the present invention provides a method for preparing a solid electrolyte membrane with high ionic conductivity, comprising the following steps:

[0012] Amino compounds and acid anhydride compounds are dissolved in solvent 1 to obtain a polyimide precursor spinning solution, which is then electrospun and cured to obtain a polyimide-based film.

[0013] Electrolyte particles are dispersed in solvent 2 to obtain a suspension. The polyimide-based membrane is then immersed in the suspension and dried to obtain a polyimide-based membrane filled with electrolyte particles.

[0014] The monomer, lithium salt, initiator and solvent 3 are mixed to prepare a prepolymer solution. The prepolymer solution is coated onto a polyimide-based membrane filled with electrolyte particles. After thermal polymerization, a solid electrolyte membrane is obtained.

[0015] As one possible design, the preparation of the polyimide-based film includes the following steps:

[0016] Weigh out the amino compound and the acid anhydride compound, dissolve the amino compound and the acid anhydride compound in solvent 1, stir, and prepare a polyimide precursor spinning solution;

[0017] Electrospinning was performed under conditions of 10–20 kV voltage, 0.3–1.0 mL / h feed rate, and 15–25 cm receiving distance to form a porous fiber-based membrane;

[0018] A porous fiber-based membrane was subjected to gradient heating, with a total heating temperature of 80–350℃, to obtain a polyimide-based membrane. The gradient heating process included three stages.

[0019] The first stage temperature is 80-150℃, and the time is 30 minutes to 2 hours;

[0020] The second stage involves a temperature of 150–250℃ and a duration of 30 minutes to 2 hours.

[0021] The third stage involves a temperature of 250–350℃ and a duration of 1–3 hours.

[0022] As one possible design, the aforementioned amino compound includes one or more of diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), 4,4'-diaminodiphenyl sulfone (DDS), 3,4'-diaminodiphenyl ether (3,4'-ODA), hexamethylenediamine (HDA), ethylenediamine (EDA), 4,4'-diaminotriphenylmethane (DAM), and fluorodiamines (such as 6FDA derivatives);

[0023] The acid anhydride compounds include one or more of pyromellitic anhydride (PMDA), dianhydride (BTDA), 6FDA (difluorinated dianhydride), and maleic anhydride (MA);

[0024] The total solids content of the polyimide precursor spinning solution is 15–25 wt.%.

[0025] As one possible design, solvent 1 is N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP).

[0026] As one possible design, the above-mentioned electrolyte particles have a particle size of 10–500 nm;

[0027] The electrolyte particles include Li 10 GeP2S 12 Li 9.5 Al 0.5 GeP2S 12 Li7P3S 11 , Li3PS4, Li6PS5Cl, Li7La3Zr2O 12 Li4Ti5O 12 One or more of the following: LiAlO2, Li3PO4, LiLaTiO3, Li3N, LiSi2N3, Li6N3Br, LiAlN2, Li2SiO3, Li4SiC, Li2Ti3C2, LiFePO4, Li3BO3, and LiAlBO;

[0028] The concentration of the suspension is 10–30 mg / mL.

[0029] As one possible design, the monomers mentioned above include one or more of polyethylene glycol dimethacrylate, polymethyl acrylate, polyvinyl alcohol, polyvinylidene fluoride hexafluoropropylene, and polymethacrylamide;

[0030] The lithium salt includes one or more of LiTFSI, LiClO4, LiPF6, LiFSI, and LiBF4;

[0031] The initiator includes one or more of benzoyl peroxide, azobisisobutyronitrile, di-tert-butyl peroxide, hydrogen peroxide, and diethyldimethyl oxynitride.

[0032] The solvent 3 includes one or more of acetonitrile, N,N-dimethylformamide and acetone.

[0033] As one possible design, the thickness of the prepolymer liquid coated onto the polyimide-based film filled with electrolyte particles is 5–20 μm.

[0034] As one possible design, the above-mentioned thermal polymerization treatment temperature is 60-100℃ and the time is 2-6h.

[0035] As one possible design, the aforementioned solid electrolyte membrane is further subjected to post-processing, which includes high-temperature vacuum drying and hot pressing of the solid electrolyte membrane.

[0036] As one possible design, the above-mentioned high-temperature vacuum drying process is specifically carried out at 60–120°C for 8–24 hours;

[0037] The hot pressing treatment is specifically carried out at 80–120°C and 5–15 MPa for 10–60 minutes.

[0038] Secondly, the present invention provides a solid electrolyte membrane with high ionic conductivity, which is prepared by the above-described preparation method.

[0039] Thirdly, the present invention provides the application of a high ionic conductivity solid electrolyte membrane prepared by the above-mentioned preparation method in the preparation of lithium-ion batteries.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] This invention obtains a flexible, high-strength solid electrolyte membrane with high ionic conductivity by filling the pores of a polyimide-based membrane with solid electrolyte particles of high ionic conductivity and using an in-situ polymerized solid electrolyte as a binder.

[0042] The modified separator of this invention significantly improves flexibility and strength, meeting the requirements of high-precision coating and winding processes. Thanks to the synergistic effect of inorganic particles and polymer electrolyte, the separator achieves an ionic conductivity of over 10⁻³ S / cm at room temperature. Through in-situ polymerization of the binder, the modified separator bonds tightly to the electrode interface, significantly reducing the battery's internal resistance. The separator is non-flammable and has high thermal stability, significantly improving battery safety. The electrospinning and in-situ polymerization processes facilitate large-scale production. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for explanation only and are not intended to limit the invention. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0044] Existing solid electrolyte membranes suffer from the problem of not being able to simultaneously achieve excellent mechanical properties, processability, and high ionic conductivity. This invention addresses this issue by preparing a polyimide porous base membrane through electrospinning, followed by functionalization through the filling of high-ionic-conductivity solid electrolyte particles and in-situ thermally initiated polymerization. The result is a solid electrolyte membrane that possesses excellent flexibility, mechanical properties, and ionic conductivity.

[0045] A method for preparing a solid electrolyte membrane with high ionic conductivity includes the following steps:

[0046] S1. Dissolve the amino compound and the acid anhydride compound in solvent 1 to obtain a polyimide precursor spinning solution, perform electrospinning, and then cure to obtain a polyimide-based film.

[0047] Polyimide-based films prepared by electrospinning have a three-dimensional network structure, which facilitates subsequent particle filling and has excellent flexibility and mechanical strength, meeting the requirements of high-precision coating and winding processes.

[0048] In some embodiments of the present invention, the preparation of the above-mentioned polyimide-based film includes the following steps:

[0049] S11. Weigh out the amino compound and the acid anhydride compound, dissolve the amino compound and the acid anhydride compound in solvent 1, and stir to obtain a polyimide precursor spinning solution.

[0050] Preferably, dissolving the amino compound and the acid anhydride compound in solvent 1 specifically involves: dissolving the amino compound in solvent 1, stirring for 0.5 to 5 hours under ice-water bath conditions at -5 to 20°C, adding the acid anhydride compound, and stirring for 2 to 10 hours to allow the amidation reaction to occur until the reaction is complete, thereby obtaining a polyimide precursor spinning solution.

[0051] Preferably, the molar ratio of the amino compound to the acid anhydride compound is (0.9–1.1):1.

[0052] In some embodiments of the present invention, the imide precursor content in the above spinning solution is 10-15 wt.%.

[0053] In some embodiments of the present invention, the above-mentioned amino compounds include one or more of the following: diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), 4,4'-diaminodiphenyl sulfone (DDS), 3,4'-diaminodiphenyl ether (3,4'-ODA), hexamethylenediamine (HDA), ethylenediamine (EDA), 4,4'-diaminotriphenylmethane (DAM), diaminopyridine compounds, fluorodiamines (such as 6FDA derivatives), siloxane-containing diamines, and carboxyl or hydroxyl-containing diamines.

[0054] In some embodiments of the present invention, the above-mentioned anhydride compounds include one or more of pyromellitic anhydride (PMDA), dianhydride (BTDA), 6FDA (difluorinated dianhydride), biphenyl tetracarboxylic anhydride (BPDA), cyclohexanetetracarboxylic anhydride (CHDA), maleic anhydride (MA), and phenylene tetracarboxylic anhydride (s-BPDA).

[0055] Preferably, the solvent 1 mentioned above includes N,N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP).

[0056] S12. Electrospinning is performed under the conditions of voltage 10-20kV, feed speed 0.3-1.0mL / h, and receiving distance 15-25cm to form a porous fiber base membrane.

[0057] The aforementioned fiber-based membrane has a three-dimensional network structure, which is beneficial for the subsequent filling process.

[0058] Preferably, the pore size of the fiber-based membrane is 0.1 to 5 μm.

[0059] S13. The porous fiber-based membrane is subjected to gradient heating, with a total heating temperature of 80–350℃, to obtain a polyimide-based membrane. The gradient heating includes three stages.

[0060] The first stage temperature is 80-150℃, and the time is 30 minutes to 2 hours;

[0061] The second stage involves a temperature of 150–250℃ and a duration of 30 minutes to 2 hours.

[0062] The third stage involves a temperature of 250–350°C and a duration of 1–3 hours. Gradual temperature increases can facilitate the thermal amidation reaction.

[0063] Preferably, the heating described above is gradient heating. The total heating temperature is 80–350°C.

[0064] Preferably, the thickness of the polyimide-based film is 10–30 μm.

[0065] Preferably, the curing process involves gradual temperature increases: the first stage (low-temperature desolventizing and preliminary cyclization) has a temperature of 80℃ to 150℃ and a time of 30 minutes to 2 hours; the second stage (medium-temperature dehydration and cyclization) has a temperature of 150℃ to 250℃ and a time of 30 minutes to 2 hours; and the third stage (high-temperature complete imidization) has a temperature of 250℃ to 350℃ and a time of 1 hour to 3 hours. Heating causes the polyamic acid to dehydrate and cyclize, forming a thermally stable polyimide, thereby reducing internal stress and improving the mechanical strength of the film, ultimately resulting in a porous polyimide-based film.

[0066] S2. Disperse the electrolyte particles in solvent 2 to obtain a suspension. Immerse the polyimide-based membrane in the suspension and then dry it to obtain a polyimide-based membrane filled with electrolyte particles.

[0067] In some embodiments of the present invention, the particle size of the electrolyte particles is 10 to 500 nm.

[0068] In some embodiments of the present invention, the electrolyte particles include Li 10 GeP2S 12 (LGPS), Li 9.5 Al 0.5 GeP2S 12 Li7P3S 11 , Li3PS4, Li6PS5Cl(LPSC), Li7La3Zr2O 12 (LLZO), Li4Ti5O 12 One or more of the following electrolyte particles are selected: LiAlO2, Li3PO4, LiLaTiO3 (LLTO), Li3N, LiSi2N3, Li6N3Br, LiAlN2, Li2SiO3, Li4SiC, Li2Ti3C2, LiFePO4 (LFP), Li3BO3, and LiAlBO. These electrolyte particles are high-ionic-conductivity solid electrolyte particles, and selecting these particles for filling can increase the ionic conductivity of the membrane.

[0069] Preferably, after dispersing the above-mentioned electrolyte particles in solvent 2, ultrasonic treatment is performed to obtain a suspension in which the particles are uniformly dispersed.

[0070] Preferably, solvent 2 includes anhydrous ethanol and / or acetone.

[0071] In some embodiments of the present invention, the concentration of the suspension is 10-30 mg / mL.

[0072] The above-mentioned ultrasonic treatment specifically involves ultrasonication at a frequency of 40–60 kHz for 10–30 minutes.

[0073] The polyimide-based film is immersed in the suspension for 5–15 minutes, then removed and dried at 50–70°C for 1–3 hours.

[0074] Preferably, the above soaking and removal process is repeated 2 to 5 times. This treatment ensures that the particles are evenly filled.

[0075] S3. Mix monomer, lithium salt, initiator and solvent 3 to prepare prepolymer solution. Coat the prepolymer solution onto polyimide-based membrane filled with electrolyte particles. After thermal polymerization treatment, obtain solid electrolyte membrane.

[0076] In-situ thermal polymerization is used to polymerize high ionic conductivity polymer electrolytes on the base film, which can improve the ionic conductivity while ensuring a tight bond between the base film and the electrode interface.

[0077] Preferably, the molar ratio of the monomer to the lithium salt is 15 to 25:1.

[0078] Preferably, the amount of the initiator used is 0.5 to 1.5 wt.% of the monomer mass.

[0079] In some embodiments of the present invention, the monomers mentioned above include one or more of polyethylene glycol dimethacrylate (PEGDA), polymethyl acrylate (PMMA), polyvinyl alcohol (PVA), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), and polymethacrylamide (PMA).

[0080] In some embodiments of the present invention, the lithium salts mentioned above include one or more of LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiClO4 (lithium perchlorate), LiPF6 (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), and LiBF4 (lithium tetrafluoroborate).

[0081] In some embodiments of the present invention, the initiator includes one or more of benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN), di-tert-butyl peroxide (DTBP), hydrogen peroxide (H2O2), and diethyldimethyl nitride (DEDM).

[0082] In some embodiments of the present invention, the solvent 3 mentioned above includes one or more of acetonitrile, N,N-dimethylformamide and acetone.

[0083] In some embodiments of the present invention, the thickness of the prepolymer liquid coated onto the polyimide-based film filled with electrolyte particles is 5–20 μm. If it is too thin, the mechanical strength is too low, making it impossible to complete the lithium battery processing and manufacturing; if it is too thick, it will increase the separator impedance and reduce the charge and discharge performance of the lithium battery. Therefore, a thickness of 5–20 μm is optimal.

[0084] In some embodiments of the present invention, the above-mentioned thermal polymerization treatment temperature is 60-100°C and the time is 2-6 hours.

[0085] In some embodiments of the present invention, the above-mentioned solid electrolyte membrane is further subjected to post-processing, which includes high-temperature vacuum drying and hot pressing of the solid electrolyte membrane.

[0086] In some embodiments of the present invention, the above-mentioned high-temperature vacuum drying treatment is specifically carried out at 60–120°C for 8–24 hours. Treatment under these conditions can remove residual solvents and unreacted substances.

[0087] In some embodiments of the present invention, the hot pressing treatment is specifically performed at 80–120°C and 5–15 MPa for 10–60 minutes. Hot pressing under these conditions can improve the mechanical properties and interfacial bonding strength of the diaphragm.

[0088] The present invention also provides a solid electrolyte membrane with high ionic conductivity prepared by the above preparation method.

[0089] The present invention also provides the application of a high ionic conductivity solid electrolyte separator prepared by the above preparation method in the preparation of lithium-ion batteries.

[0090] Example 1

[0091] A method for preparing a solid electrolyte membrane with high ionic conductivity includes the following steps:

[0092] S1. Preparation of polyimide-based film

[0093] Preparation of polyimide precursor spinning solution: Amino compound ODA (4,4'-diaminodiphenyl ether) and anhydride compound BPDA (biphenyl tetracarboxylic anhydride) were weighed at a molar ratio of 1:1 and added to solvent 1 (NMP, N-methylpyrrolidone). The mixture was mechanically stirred for 4 hours in an ice-water bath (10℃) to ensure complete reaction and generate a polyamic acid precursor solution with a solid content of 20 wt.%. Electrospinning: The above polyimide precursor spinning solution was electrospinned at a voltage of 15 kV, a feed speed of 0.5 mL / h, and a receiving distance of 20 cm to form a porous fiber-based membrane with a pore size range of 0.5–2 μm. Heat treatment curing: The porous fiber-based membrane was subjected to a gradient temperature treatment: First stage: curing at 100℃ for 1 h; Second stage: curing at 200℃ for 2 h; Third stage: curing at 350℃ for 3 h. A polyimide-based membrane with a thickness of 15 μm was finally obtained.

[0094] S2, Electrolyte Particle Filling

[0095] Suspension preparation: Electrolyte particles (Li) 10 GeP2S 12 The polyimide membrane (with a particle size of 50–100 nm and an ionic conductivity of 10⁻³ S / cm) was dispersed in solvent 2 (anhydrous ethanol) and sonicated at 50 kHz for 20 min to obtain a homogeneous suspension with a concentration of 20 mg / mL. Filling treatment: The polyimide membrane was immersed in the suspension for 10 min, then dried at 60 °C for 2 h. This immersion and drying process was repeated three times to obtain a polyimide membrane uniformly filled with electrolyte particles.

[0096] S3. Preparation of solid electrolyte membrane

[0097] Prepolymer preparation and coating: A prepolymer was prepared by mixing monomer (PEGDA), lithium salt (LiTFSI, monomer to lithium salt molar ratio of 20:1), initiator (IBN, amounted to 1 wt.% of monomer mass), and solvent 3 (anhydrous acetonitrile). The prepolymer was uniformly coated onto a polyimide-based membrane filled with electrolyte particles to a thickness of 10 μm. Thermal polymerization: Thermal polymerization was performed at 80 °C for 4 h to obtain a solid electrolyte membrane.

[0098] S4, Post-processing

[0099] High-temperature vacuum drying: The solid electrolyte membrane is vacuum dried at 80℃ for 12 hours to remove residual solvents and unreacted substances. Hot pressing treatment: The membrane is hot-pressed at 100℃ and 10MPa for 30 minutes to improve its mechanical properties and interfacial bonding strength, resulting in the finished solid electrolyte membrane.

[0100] Example 2

[0101] A method for preparing a solid electrolyte membrane with high ionic conductivity includes the following steps:

[0102] S1. Preparation of polyimide-based film

[0103] Preparation of polyimide precursor spinning solution: Amino compound ODA (4,4'-diaminodiphenyl ether) and acid anhydride compound PMDA (pyromellitic tetracarboxylic anhydride) were weighed at a molar ratio of 1:1 and added to solvent 1 (DMAc, N,N-dimethylacetamide). The mixture was mechanically stirred for 5 hours in an ice-water bath (5°C) to allow for complete reaction and generate a polyamic acid precursor solution with a solid content of 20 wt.%. Electrospinning: The above polyimide precursor spinning solution was electrospinned at a voltage of 18 kV, a feed speed of 0.4 mL / h, and a receiving distance of 22 cm to form a porous fiber-based membrane with a pore size range of 1–3 μm. Heat treatment curing: The porous fiber-based membrane was subjected to a gradient temperature treatment: First stage: curing at 80°C for 1 h; Second stage: curing at 150°C for 1.5 h; Third stage: curing at 350°C for 2 h. A polyimide-based membrane with a thickness of 20 μm was finally obtained.

[0104] S2, Electrolyte Particle Filling

[0105] Suspension preparation: Electrolyte particles (Li7La3Zr2O) 12 The particles (100–200 nm in diameter, ionic conductivity 10⁻³ S / cm) were dispersed in solvent 2 (acetone) and sonicated at 55 kHz for 25 minutes to obtain a uniform suspension with a concentration of 15 mg / mL. Filling treatment: The polyimide-based membrane was immersed in the suspension for 8 minutes, then dried at 70 °C for 3 hours. This immersion and drying process was repeated four times to obtain a polyimide-based membrane uniformly filled with electrolyte particles.

[0106] S3. Preparation of solid electrolyte membrane

[0107] Prepolymer preparation and coating: A prepolymer was prepared by mixing monomers (PVDF-HFP), lithium salt (LiPF6, monomer to lithium salt molar ratio of 15:1), initiator (BPO, amounted to 0.8 wt.% of monomer mass), and solvent 3 (DMAc). The prepolymer was uniformly coated onto a polyimide-based membrane filled with electrolyte particles to a thickness of 15 μm. Thermal polymerization: Thermal polymerization was performed at 70 °C for 3 h to obtain a solid electrolyte membrane.

[0108] S4, Post-processing

[0109] High-temperature vacuum drying: The solid electrolyte membrane is vacuum dried at 100℃ for 16 hours to remove residual solvent and unreacted substances. Hot pressing treatment: The membrane is hot-pressed at 110℃ and 12MPa for 40 minutes to improve its mechanical properties and interfacial bonding strength, resulting in the finished solid electrolyte membrane.

[0110] Example 3

[0111] A method for preparing a solid electrolyte membrane with high ionic conductivity includes the following steps:

[0112] S1. Preparation of polyimide-based film

[0113] Preparation of polyimide precursor spinning solution: Amino compound ODA (4,4'-diaminodiphenyl ether) and anhydride compound BPDA (biphenyl tetracarboxylic anhydride) were weighed at a molar ratio of 1:1 and added to solvent 1 (DMAc, N,N-dimethylacetamide). The mixture was mechanically stirred for 2 hours in an ice-water bath (10°C). Subsequently, mechanical stirring was continued for 6 hours under the same conditions to ensure complete reaction and generate a polyimide precursor spinning solution with a solid content of 20 wt.%. Electrospinning: The above spinning solution was electrospinned under conditions of 12 kV voltage, a feed speed of 0.6 mL / h, and a receiving distance of 18 cm to form a porous three-dimensional network fiber matrix membrane with fiber pore sizes of 1–3 μm. Heat treatment curing: The porous fiber matrix membrane was subjected to gradient temperature treatment: First stage: curing at 80–120°C for 1 h; Second stage: curing at 150°C for 2 h; Third stage: curing at 350°C for 3 h. The final result was a polyimide-based film with a thickness of 12 μm.

[0114] S2, Electrolyte Particle Filling

[0115] Suspension preparation: Electrolyte particles (Li6PS5Cl, particle size 20–50 nm, ionic conductivity 10⁻³ S / cm) were dispersed in solvent 2 (acetonitrile) and sonicated at 60 kHz for 30 minutes to obtain a suspension with a concentration of 25 mg / mL. Filling treatment: The polyimide-based membrane was immersed in the suspension for 12 minutes, followed by drying at 65 °C for 2.5 hours. This immersion and drying process was repeated 5 times to obtain a polyimide-based membrane uniformly filled with electrolyte particles.

[0116] S3. Preparation of solid electrolyte membrane

[0117] Prepolymer preparation and coating: A prepolymer was prepared by mixing monomer (PVA), polymethacrylamide (PMA), lithium salt (LiFSI, monomer to lithium salt molar ratio of 20:1), initiator (DTBP, initiator amount of 1 wt.% of monomer mass), and solvent 3 (anhydrous acetone). The prepolymer was uniformly coated onto a polyimide-based membrane filled with electrolyte particles to a thickness of 12 μm. Thermal polymerization: Thermal polymerization was performed at 75 °C for 3 hours to obtain a solid electrolyte membrane.

[0118] S4, Post-processing

[0119] High-temperature vacuum drying: The solid electrolyte membrane is dried at 70°C under high-temperature vacuum for 10 hours to remove residual solvent and unreacted substances.

[0120] Hot pressing treatment: The dried solid electrolyte membrane is hot-pressed at 90℃ and 8MPa for 20 minutes to further improve the mechanical properties and interfacial bonding strength of the membrane, and finally obtain the finished solid electrolyte membrane.

[0121] Comparative Example 1

[0122] This comparative example is basically the same as Example 1, except that step S2 is omitted.

[0123] Comparative Example 2

[0124] This comparative example is basically the same as Example 1, except that step S3 is omitted.

[0125] Comparative Example 3

[0126] This comparative example is basically the same as Example 1, except that step S4 is omitted.

[0127] Comparative Example 4

[0128] This comparative example is basically the same as Example 1, except that hot pressing is not performed in step S4.

[0129] Experimental Example

[0130] The ionic conductivity of the samples from Examples 1-3 and Comparative Examples 1-4 was tested in an electrolyte, with PP and PE membranes respectively attached.

[0131] The method for testing ionic conductivity is as follows:

[0132] The ionic conductivity testing procedure for a membrane typically includes the following steps:

[0133] 1. Pretreatment of the diaphragm

[0134] Cut the PP or PE diaphragm into sizes suitable for testing (usually small pieces with a diameter of 10 to 20 mm).

[0135] Clean the membrane surface with deionized water and anhydrous ethanol to remove any possible surface impurities.

[0136] The diaphragm is dried in a vacuum drying oven at a temperature typically set at 60°C for 4–6 hours to remove adsorbed moisture or solvent from its surface.

[0137] 2. Electrolyte impregnation

[0138] Prepare a suitable electrolyte (such as a lithium salt solution, for example, 1M LiPF6 dissolved in EC / DMC solvent).

[0139] The diaphragm is completely immersed in the electrolyte for 12 to 24 hours to ensure that the inside of the diaphragm is fully wetted.

[0140] 3. Assemble and test the battery

[0141] A stainless steel-stainless steel symmetrical structure (SS|diaphragm|SS) was used as the test unit.

[0142] In the battery clamp, a separator soaked in electrolyte is sandwiched between two stainless steel electrodes.

[0143] Ensure good contact between the electrodes and the diaphragm in the fixture, and prevent leakage or diaphragm wrinkles.

[0144] 4. Test Environment Preparation

[0145] Place the test unit in a constant temperature chamber and control the temperature (e.g., 25℃).

[0146] Let it stand for a period of time (usually 30 minutes to 1 hour) to ensure that the electrolyte and diaphragm are stable.

[0147] 5. Testing Instruments and Parameter Settings

[0148] Measurements were performed using an electrochemical impedance spectroscopy (EIS) instrument.

[0149] Frequency range: typically 1MHz to 1Hz.

[0150] AC amplitude: 5-10mV.

[0151] 6. Data Acquisition and Calculation

[0152] The resistance (R) is measured, and the impedance value of the diaphragm is obtained through the real axis intercept at the high-frequency end of the Nyquist plot.

[0153] Calculate the ionic conductivity using the formula:

[0154] σ: Ionic conductivity (S / cm)

[0155] L: Diaphragm thickness (cm)

[0156] R: Measured resistance value (Ω)

[0157] A: Effective area of ​​the diaphragm (cm²) 2 ).

[0158] 7. Data Analysis

[0159] The ionic conductivity was analyzed based on the test results to compare the performance of different diaphragms.

[0160] The above steps can accurately determine the ionic conductivity of PP and PE membranes and provide a basis for evaluating their electrochemical performance.

[0161] The results are shown in Table 1.

[0162] Table 1

[0163]

[0164] Based on Table 1, it can be inferred that the ionic conductivity of the comparative sample will decrease significantly due to the omission of key steps.

[0165] Compared to Example 1, Comparative Example 1 omits step S2. The main function of step S2 is to fill the polyimide-based membrane with high-conductivity electrolyte particles. This step plays a crucial role in improving ionic conductivity. If this step is omitted, the polyimide-based membrane will lack electrolyte particles, obstructing ion conduction pathways and resulting in a significant decrease in conductivity.

[0166] Compared to Example 1, Comparative Example 2 omits step S3 in Comparative Example 1. Step S3 aims to further optimize the ion conduction path by forming a continuous solid electrolyte layer through coating with a prepolymer and thermal polymerization. If this step is omitted, the electrolyte membrane surface lacks an effective ion-conducting layer structure, and the ion conductivity will significantly decrease.

[0167] Compared to Comparative Example 1, Comparative Example 3 omits step S4 in Comparative Example 1. The high-temperature vacuum drying and hot-pressing treatment in step S4 primarily improves the mechanical properties and interfacial bonding strength of the membrane, indirectly affecting its conductivity. If this step is omitted, the interfacial properties of the membrane are poor, which may affect the stability of some ion conduction pathways, but the impact is relatively small.

[0168] Compared to Example 1, Comparative Example 3 does not perform hot-pressing treatment in step S4. Hot-pressing treatment improves the interfacial bonding strength and mechanical properties of the membrane, and plays an auxiliary role in the stability of the ion conduction path. Without hot-pressing treatment, the conductivity may decrease slightly, but it will still be close to the level of the example.

[0169] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a solid electrolyte membrane with high ionic conductivity, characterized in that, Includes the following steps: Amino compounds and acid anhydride compounds are dissolved in solvent 1 to obtain a polyimide precursor spinning solution, which is then electrospun and cured to obtain a polyimide-based film. Electrolyte particles are dispersed in solvent 2 to obtain a suspension. The polyimide-based membrane is then immersed in the suspension and dried to obtain a polyimide-based membrane filled with electrolyte particles. The monomer, lithium salt, initiator and solvent 3 are mixed to prepare a prepolymer solution. The prepolymer solution is coated onto a polyimide-based membrane filled with electrolyte particles. After thermal polymerization, a solid electrolyte membrane is obtained. The electrolyte particles have a particle size of 10–500 nm; The electrolyte particles include Li 10 GeP2S 12 Li 9.5 Al 0.5 GeP2S 12 Li7P3S 11 , Li3PS4, Li6PS5Cl, Li7La3Zr2O 12 Li4Ti5O 12 One or more of the following: LiAlO2, Li3PO4, LiLaTiO3, Li3N, LiSi2N3, Li6N3Br, LiAlN2, Li2SiO3, Li4SiC, Li2Ti3C2, LiFePO4, Li3BO3, and LiAlBO; The concentration of the suspension is 10–30 mg / mL.

2. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The preparation of the polyimide-based film includes the following steps: Weigh out the amino compound and the acid anhydride compound, dissolve the amino compound and the acid anhydride compound in solvent 1, stir, and prepare a polyimide precursor spinning solution; Electrospinning was performed under conditions of 10–20 kV voltage, 0.3–1.0 mL / h feed rate, and 15–25 cm receiving distance to form a porous fiber-based membrane; A porous fiber-based membrane was subjected to gradient heating, with a total heating temperature of 80–350℃, to obtain a polyimide-based membrane. The gradient heating process included three stages. The first stage temperature is 80-150℃, and the time is 30 minutes to 2 hours; The second stage involves a temperature of 150–250℃ and a duration of 30 minutes to 2 hours. The third stage involves a temperature of 250–350℃ and a duration of 1–3 hours.

3. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The amino compound includes one or more of the following: diaminodiphenyl ether, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl ether, hexamethylenediamine, ethylenediamine, 4,4'-diaminotriphenylmethane, and fluorodiamine. The anhydride compounds include one or more of pyromellitic anhydride, dianhydride, 6FDA and maleic anhydride; The total solids content of the polyimide precursor spinning solution is 15–25 wt.

4. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, Solvent 1 is N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

5. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The monomers include one or more of polyethylene glycol dimethacrylate, polymethyl acrylate, polyvinyl alcohol, polyvinylidene fluoride hexafluoropropylene, and polymethacrylamide; The lithium salt includes one or more of LiTFSI, LiClO4, LiPF6, LiFSI, and LiBF4; The initiator includes one or more of benzoyl peroxide, azobisisobutyronitrile, di-tert-butyl peroxide, hydrogen peroxide, and diethyldimethyl oxynitride. The solvent 3 includes one or more of acetonitrile, N,N-dimethylformamide and acetone.

6. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The thickness of the prepolymer liquid coated onto the polyimide-based film filled with electrolyte particles is 5–20 μm.

7. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The thermal polymerization treatment temperature is 60–100℃, and the time is 2–6 hours.

8. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 1, characterized in that, The solid electrolyte membrane is further subjected to post-processing, which includes high-temperature vacuum drying and hot pressing of the solid electrolyte membrane.

9. The method for preparing a high ionic conductivity solid electrolyte membrane according to claim 8, characterized in that, The high-temperature vacuum drying process is specifically carried out at 60–120°C for 8–24 hours. The hot pressing treatment is specifically carried out at 80–120°C and 5–15 MPa for 10–60 minutes.

10. A solid electrolyte membrane with high ionic conductivity, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

11. The application of a high ionic conductivity solid electrolyte separator prepared by the preparation method according to any one of claims 1 to 9 in the preparation of lithium-ion batteries.

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