Composite solid electrolyte membrane based on glass fibers and preparation method and application thereof

Abstract

The invention discloses a composite solid electrolyte membrane based on glass fibers and a preparation method and application thereof. The electrolyte is prepared by taking an NASICON type ceramic electrolyte Li1. 3Al0. 3Ti1. 7 (PO4) 3 (LATP) and a copolymer polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) as a composite matrix, taking a lithium salt (LiTFSI) as a constructed ion transmission channel to regulate and control the chemical and mechanical properties of an interface, and combining with a commercial glass fiber (GF / F) supporting framework. By constructing a stable porous skeleton on the positive electrode and designing a high-ionic-conductivity coating layer, a solid electrolyte precursor is introduced into the positive electrode, and the glass fiber-based composite solid electrolyte is combined and designed, so that the reaction mass transfer process of the positive electrode and the glass fiber composite solid electrolyte can be accelerated; and a high-speed ion transmission channel is constructed in the positive electrode and the solid electrolyte, so that electrochemical reaction active sites are greatly expanded, and a low-impedance and high-stability positive electrode-electrolyte interface is finally realized.

Description

Technical Field

[0001] The present invention belongs to the field of new energy materials, and specifically relates to a composite solid electrolyte based on a three-dimensional glass fiber network structure, and its composite positive electrode structure design, including its microstructure design, preparation process optimization, and electrochemical performance improvement plan, and expands its application in lithium metal batteries, solid-state sodium batteries and flexible energy storage devices. Background Art

[0002] Traditional lithium-ion batteries rely on liquid electrolyte systems and face long-term safety hazards such as leakage risk, flammability and insufficient thermal stability. In particular, irregular protrusions of lithium dendrites are easily formed on the surface of lithium metal negative electrodes. From an engineering perspective, mechanical inhibition is a direct strategy to control their growth. Based on the high shear modulus theory, the use of solid electrolytes to replace liquid electrolytes and diaphragms has become a recognized effective solution to inhibit dendrite growth. Solid electrolytes mainly include three categories: polymer type (such as PEO-based), inorganic type (such as oxide LLZO, sulfide LGPS) and organic / inorganic composite type. They need to meet the requirements of high ionic conductivity (>10 -4 S / cm), low electronic conductivity, and a wide electrochemical window (low reduction / high oxidation potential). Although solid-state electrolytes have become a research focus due to their high safety and theoretical energy density, existing systems still have significant defects: the interface impedance of sulfide electrolytes is high (>200 Ω·cm 2 ), oxide electrolytes are brittle (flexural strength <50 MPa), and the room temperature ionic conductivity of pure PEO-based electrolytes is as low as 10 -5 S / cm and insufficient mechanical properties (tensile strength <5 MPa). Even with the strategy of filling LLZO ceramics with glass fibers, the performance improvement is limited due to poor interfacial compatibility.

[0003] Glass fiber, with its high strength (tensile strength > 1 GPa), high temperature resistance (> 500°C) and porous structure, can be used as an ideal skeleton material to enhance the mechanical properties of the electrolyte and optimize the ion transport channel. However, its composite process with solid electrolytes is still immature, and insufficient interfacial compatibility restricts the electrochemical performance. Although polymer electrolytes have good interfacial contact properties, they are limited by their intrinsic low ionic conductivity (10 -6 ~10 -5 S / cm) and thermal stability defects (glass transition temperature <60°C). The above problems make it difficult for a single inorganic or polymer electrolyte to meet the actual needs of all-solid-state lithium metal batteries.

[0004] Composite electrolytes can cooperate with inorganic materials to achieve high ion conductivity (such as LATP up to 10 -3S / cm) and the flexible interface characteristics of the polymer, with the advantages of high lithium ion transference number (>0.5) and low-cost processing, become a compromise solution. However, the existing composite system still has the problem of insufficient ion conductivity / stability (<10 -4 The development of new electrolytes has been slow due to bottlenecks such as low electrolyte density (<200 cycles) and poor compatibility (e.g., lithium-oxygen batteries must withstand high-pressure oxygen environments). Therefore, there is an urgent need for a new electrolyte with good interfacial compatibility and high ionic conductivity. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides a glass fiber composite solid electrolyte with good interface compatibility, high ionic conductivity and excellent mechanical strength, which solves the problems of high interface impedance and easy brittle cracking of existing solid electrolytes. At the same time, compared with the layered structure in traditional batteries, the glass fiber has a stable porous structure and high ionic conductivity, and the excellent composite solid positive electrode and glass fiber composite solid electrolyte structure design is expected to fully replace the liquid electrolyte, so that the composite solid positive electrode and the composite solid electrolyte have good interface contact, and the mass transfer process required for the three-phase reaction can be quickly realized. A stable and high-speed ion transmission channel is formed inside the composite solid positive electrode and the glass fiber composite solid electrolyte, which greatly expands the reaction site and realizes a low-impedance composite solid positive electrode and composite solid electrolyte contact interface, thereby improving battery safety performance and reducing the risk of thermal runaway.

[0006] The technical solutions provided by the present invention are as follows:

[0007] A method for preparing a glass fiber-based composite solid electrolyte membrane comprises immersing the glass fiber in a solid electrolyte precursor solution comprising a lithium salt, a polymer matrix and an inorganic filler, and vacuum drying the solution to obtain a glass fiber-based composite solid electrolyte membrane.

[0008] Furthermore, the glass fiber is immersed in the solid electrolyte precursor solution for 20 to 28 hours, and the loading amount of the solid electrolyte precursor solution in the glass fiber is 4 to 6 mg / cm 2 .

[0009] Furthermore, the polymer substrate is one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and polymethyl acrylate; the inorganic filler is Li 1.3 Al 0.3 Ti 1.7 (PO4)3,Li7La3Zr2O 12 , Li3PO4; the lithium salt is LiTFSI or Li6PS5Cl.

[0010] Furthermore, the preparation method of the solid electrolyte precursor solution includes: dissolving the polymer matrix and lithium salt in DMF as solution A; dispersing the inorganic filler in acetone as solution B; transferring solution B into solution A, and continuously stirring at room temperature to obtain a solid electrolyte precursor solution.

[0011] The present invention also provides a glass fiber-based composite solid electrolyte membrane, which is prepared using the above-mentioned preparation method.

[0012] The present invention also provides application of the above-mentioned glass fiber-based composite solid electrolyte membrane in a solid-state lithium battery.

[0013] Furthermore, the solid-state lithium battery includes a composite solid-state positive electrode layer, the above-mentioned glass fiber-based composite solid-state electrolyte separator layer and a lithium metal negative electrode layer.

[0014] Furthermore, the composite solid-state positive electrode layer includes a positive electrode substrate and a positive electrode slurry coated on the positive electrode substrate; the positive electrode substrate is carbon paper or carbon cloth; the positive electrode slurry includes a positive electrode active material, an inorganic filler, a lithium salt and a polymer binder.

[0015] Furthermore, the positive electrode active material is one of carbon nanotubes, conductive carbon black, Ketjen black, Ru@CNTs, Ru / TiO2 / CNTs, TEMPO-COF, and FePc catalytic materials; and the polymer binder is PVDF, PTFE, or its derivatives or blended polymers.

[0016] Furthermore, the preparation method of the positive electrode slurry includes: mixing the positive electrode active material, the inorganic filler, the lithium salt and the polymer binder in an organic solvent, wherein the organic solvent is N-methylpyrrolidone.

[0017] (1) The solid-state lithium battery comprises:

[0018] Positive electrode active materials: carbon materials (CNTs, KB, etc.), carbon-based materials doped with transition metal catalysts (Ru@CNTs, NiFeOx@CNTs, etc.), lithium iron phosphate (LiFePO4), high voltage ternary materials.

[0019] Positive electrode substrate: carbon paper, carbon cloth, etc.;

[0020] Glass fiber (pore size 0.7 μm, porosity 60%~80%, thickness 420 μm, basis weight 75 g m -2 , air velocity 3.7 Gurley (s));

[0021] Composite electrolyte precursor materials include: lithium salt, polymer matrix, and inorganic filler.

[0022] Lithium salts (LiTFSI, Li6PS5Cl, etc.)

[0023] Polymer matrix (PVDF-HFP, PMMA, PEO, etc.)

[0024] Inorganic filler (Li 1.3 Al 0.3 Ti 1.7 (PO4)3,Li7La3Zr2O 12 , Li3PO4, etc.).

[0025] Polymer binder i.e. conductive additive (PVDF, PTFE, etc.)

[0026] (2) Preparation method:

[0027] ① First, weigh and mix chemical reagents such as Li2CO3, TiO2, Al2O3 and NH4H2(PO4) according to the stoichiometric ratio. Then, place them in a ball mill and grind them at a speed of 400 rpm for 2 hours. Place the evenly ground powder in an alumina crucible and heat it in an oven at 450°C under air atmosphere for 2 hours to remove the ammonia produced by the decomposition of the ammonium phosphate component. Then, calcine the mixture at 850°C for 5 hours. The calcined powder is placed in a ball mill again and ground at a speed of 400 rpm for 5 hours to obtain a white powder inorganic filler LATP (lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3), other types of inorganic fillers (NaSCION type materials) can be synthesized by solid phase sintering method;

[0028] ② Dissolve 0.4 g of polymer matrix (PVDF-HFP) and 0.1 g of lithium salt (LiTFSI) in 2 mL of DMF as solution A;

[0029] ③ 0.4gLATP(Li 1.3 Al 0.3 Ti 1.7 (PO4)3) was dispersed in 1 mL of acetone as solution B;

[0030] ④ Use a pipette to transfer solution B into solution A and continue stirring at room temperature to obtain a precursor solution;

[0031] ⑤ Preparation of glass fiber-based composite solid electrolyte: We soaked the commercially purchased glass fiber GF / F in the precursor solution for 24 hours. The loading amount of the solid electrolyte precursor solution in the glass fiber was 4-6 mg / cm 2 between;

[0032] ⑥ After the precursor solution is fully wetted with the glass fiber, it is taken out and placed in a 120°C environment, and vacuum dried to obtain a composite solid electrolyte membrane based on glass fiber.

[0033] The porous structure of glass fiber provides continuous ion transmission channels, and the ion conductivity reaches 1.2×10 -3 S / cm (25℃);

[0034] The hot pressing process enhances the interfacial bonding strength and reduces the interfacial impedance to 50 Ω·cm²;

[0035] The compressive strength is increased to 65 MPa, which can inhibit the growth of lithium dendrites;

[0036] Wide electrochemical window (0~5 V vs. Li + / Li), with an electrochemical window much larger than the open-circuit voltage of lithium batteries and electrochemical stability under high voltage.

[0037] The purpose of the present invention is to provide a structural design for regulating the chemical activity of the glass fiber surface, combined with a simple soaking process to achieve uniform distribution of lithium salts / polymer matrix / inorganic fillers in the fiber pores, forming a "rigid and flexible" ion transport network, which is deployed in solid-state batteries and no longer requires electronic insulation or (electro)chemical stability. With our solid electrolyte design, a wide range of positive electrode material ion conductors have been applied to solid-state lithium-oxygen batteries with superior cycle performance. The above-mentioned preparation method of the glass fiber-based composite solid electrolyte membrane is applied to solid-state lithium-oxygen batteries. The present invention provides a solid-state lithium battery, comprising a composite solid-state positive electrode layer, a glass fiber-based composite solid-state electrolyte separator layer and a lithium metal negative electrode layer.

[0038] The method for preparing the composite solid-state positive electrode layer comprises: using carbon paper or carbon cloth as a positive electrode substrate to prepare a positive electrode slurry.

[0039] It is further defined that the positive electrode slurry in the composite solid-state positive electrode layer is composed of a positive electrode active material, an inorganic filler, a lithium salt and a polymer binder. The positive electrode active material is a lithium battery conductive active material that can undergo a lithium insertion process. This type of material has a large specific surface area and porosity, providing sufficient reaction sites. The positive electrode active material has a certain lithium ion conduction and electron conduction ability, and reversible lithium ion insertion and extraction occurs within a certain potential range. Such materials include but are not limited to: carbon-based materials, such as carbon nanotubes, conductive carbon black, Ketjen black, etc. Metal-based catalyst materials such as Ru@CNTs, Ru / TiO2 / CNTs, etc. and some redox mediators, such as TEMPO-COF, FePc catalytic materials. The mass ratio of the positive electrode active material in the positive electrode slurry is 30%~70%, preferably 50%.

[0040] Further defined, the inorganic filler is to allow lithium ions to pass quickly to form the charge and discharge path of the battery and effectively expand the ion-electron-oxygen three-phase reaction interface. It has excellent chemical and electrochemical stability, high ionic conductivity and selective ion transport, and effectively blocks other ions or gas molecules. It fully inhibits dendrite growth and achieves interface optimization. Inorganic fillers include but are not limited to NASICON type ion conductors Li 1.3 Al 0.3 Ti 1.7 (PO4)3、LLZTO(Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ), LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO4)3), LLZO (Li7La3Zr2O 12 ), etc., the mass ratio of the inorganic filler in the positive electrode slurry is 10% to 30%, preferably 25%.

[0041] Furthermore, lithium salts, through their molecular structure, form a stable anion network within the electrolyte, significantly reducing the solution's viscosity and significantly increasing the shuttle rate of lithium ions. This translates into high efficiency during battery charge and discharge. Lithium salts include, but are not limited to, LITFSI and Li6PS5Cl. The mass ratio of lithium salts in the positive electrode slurry is 10% to 20%, preferably 12.5%.

[0042] It is further defined that in the preparation of the positive electrode slurry, the positive electrode active material and the polymer binder, i.e., the conductive additive, are mixed to form a slurry. The polymer binder can firmly adhere the positive electrode active material to the positive electrode and the contact interface with the electrolyte, preventing the active material from falling off or aggregating during the charge and discharge cycle, thereby maintaining the stability of the electrode structure and improving the overall performance of the battery. At the same time, it can also promote the wettability of the electrolyte inside the electrode, which is beneficial to the transmission of lithium ions between the active materials, and improve the rate performance and cycle life of the battery. Polymer binders include but are not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and their derivatives and blended polymers. The mass ratio of the added binder is 10% to 20%, preferably 12.5%.

[0043] Furthermore, during the preparation of the positive electrode slurry, the inorganic filler, lithium salt, and polymer binder are further mixed in a solvent. Mixing methods include ultrasonic dispersion and mechanical stirring. Conventional organic solvents are used to dissolve the polymer without corroding the inorganic particles, and N-methylpyrrolidone (NMP) is used as the positive electrode solvent.

[0044] The cathode preparation process further defines the process as comprising coating and drying. A cathode slurry containing a uniform dispersion of active material is applied to the cathode substrate, with the loading of the active material on the substrate controlled between 0.6 and 0.8 mg. The slurry is then thoroughly dried overnight in a vacuum environment at 120°C. Finally, the carbon paper is cut into 12 mm diameter discs and stored in a glove box for later use.

[0045] The preparation method of the glass fiber-based composite solid electrolyte membrane includes: pre-dispersing the inorganic filler; using acetone as the dispersant to facilitate subsequent mixing with the polymer gel and prevent agglomeration. The ratio of the inorganic filler to the dispersant is determined during the pre-mixing process, and the mixing method is preferably mechanical stirring followed by a stirrer.

[0046] It is further defined that the inorganic filler is the same as the composite solid positive electrode component. The inorganic filler includes but is not limited to NASICON type ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3、LLZTO(Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ), LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO4)3), LLZO (Li7La3Zr2O 12 ), etc., and the mass ratio of the inorganic filler added is 10% to 50%, preferably 45%.

[0047] Furthermore, the lithium salt used is the same as that used in the composite solid-state positive electrode. The lithium salt includes, but is not limited to, LITFSI, Li6PS5Cl, etc. The weight ratio of the added lithium salt is 10% to 20%, preferably 10%.

[0048] It is further defined that lithium batteries incorporating an organic polymer matrix have advantages such as good safety, easy processing and forming, easy morphology control, and good interface contact with electrode materials. This improves the mechanical properties and resistance to physical damage of the battery, reducing the risk of thermal runaway. It also facilitates the construction of continuous lithium-ion channels within the glass fiber. The polymer matrix includes, but is not limited to, one of PVDF-HFP, PVDF, PMMA, PEO, PAN, and the like. The mass ratio of the added polymer matrix is 10% to 50%, preferably 45%.

[0049] It is further defined that the lithium salt and the polymer matrix are dissolved in an organic solvent and stirred in an oil bath until a gel-like viscous slurry is obtained.

[0050] It is further defined that the organic solvent used in the preparation process of the composite electrolyte precursor material should have the ability to dissolve the polymer without corroding the inorganic particles. Commonly used organic solvents include but are not limited to N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), tetrahydrofuran (THF), acetonitrile and their mixtures.

[0051] It is further defined that the obtained gel-like viscous slurry is further fully mixed with the premixed inorganic filler to form a homogeneous slurry to obtain a composite electrolyte precursor material.

[0052] Further, due to the thermal stability, high mechanical strength and matching electrochemical properties of glass fiber, it can be successfully used in lithium-ion batteries with high safety performance. The types of glass fiber are not limited to GF / F, GF / D, etc. The glass fiber is fully dried before use. The composite electrolyte precursor material is filled into the glass fiber using a diaphragm infiltration method, and the composite electrolyte precursor material loading is 4-6 mg cm -2 The drying process is carried out at 120°C, and a composite solid electrolyte membrane based on glass fiber is obtained after drying.

[0053] Application of negative electrode in solid-state lithium oxygen battery.

[0054] Furthermore, the negative electrode used in the present invention is a lithium metal negative electrode, which can be polished to make the surface of the lithium metal flat and smooth before use. Negative electrodes include but are not limited to lithium metal negative electrodes, lithium-intercalated negative electrodes, and alloys.

[0055] Beneficial effects

[0056] The present invention provides a composite solid electrolyte membrane based on glass fiber, which adopts a sandwich structure design and is based on a NASICON ceramic electrolyte Li 1.3 Al 0.3 Ti 1.7This composite matrix is made of (PO₄)₃ (LATP) and a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVDF-HFP), bonded to a commercial glass fiber (GF / F) support framework. Its cathode side is compatible with a variety of active materials, including carbon nanotubes, conductive carbon black, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, sulfur, and oxygen cathodes. Its anode side is compatible with conventional anode systems, including graphite, lithium metal, silicon-based materials, and alloys. The LATP inorganic layer optimizes electrochemical stability by improving ionic conductivity and suppressing lithium dendrite growth. The PVDF-HFP polymer layer enhances interfacial compatibility, reducing the stringent constraints on the solid electrolyte's electronic insulation and chemical / electrochemical stability. The introduction of LiTFSI lithium salt significantly improves lithium ion transport efficiency, partially replacing the functions of traditional liquid electrolytes. In practical applications, such as solid-state lithium-oxygen batteries, a composite solid-state cathode is often constructed, paired with a glass fiber-based composite solid electrolyte membrane, and assembled into a battery. Compared to the non-integrated layered structure of traditional quasi-solid-state batteries, this invention introduces a solid electrolyte precursor into the cathode by constructing a stable porous skeleton and a high-ionic conductivity coating layer at the cathode, potentially replacing the liquid electrolyte. Combined with the design of a glass fiber-based composite solid electrolyte, this accelerates the reaction and mass transfer between the cathode and the glass fiber composite solid electrolyte, constructs high-speed ion transport channels within the cathode and solid electrolyte, significantly expands the electrochemical reaction active sites, and ultimately achieves a low-impedance, highly stable cathode-electrolyte interface. This can effectively improve battery safety and reduce the risk of thermal runaway.

[0057] The three components of the glass fiber-based composite solid electrolyte of the present invention, LATP, LITFSI, and PVDF-HFP, are indispensable and work synergistically with each other. PVDF-HFP serves as a polymer matrix to ensure interfacial compatibility, provide tough mechanical strength, and provide lithium ion conduction channels. LATP has an orthorhombic crystal structure, high ionic conductivity and thermal stability, and maintains good electrochemical performance under high temperature and high pressure. The role of LITFSI lithium salt is to replace the liquid electrolyte, construct ion pathways, and activate reaction sites.

[0058] When solid electrolyte precursor components are applied using a coating machine using other ratios, film formation after drying cannot be guaranteed. Subsequent impregnation of glass fibers with glass fiber-based composite solid electrolyte separators cannot guarantee adequate wetting of the glass fibers or maintain uniformity of the solid electrolyte precursor slurry. The ratio of the three components described above was determined after multiple experimental adjustments and is highly innovative.

[0059] This paper proposes a glass fiber-based composite solid-state electrolyte membrane and its preparation method. This innovative process utilizes a hydrofluoric acid / dilute hydrochloric acid etching process to control the chemical activity of the fiber surface. Combined with gradient hot pressing, this process achieves a three-dimensional uniform distribution of lithium salt / polymer / ceramic fillers within the fiber pores, thereby constructing a "rigid-flexible" collaborative ion transport network. This design overcomes key bottlenecks of conventional composite electrolytes, including high interfacial impedance (reduced by 60% to <80 Ω·cm²), insufficient mechanical strength (increased to >20 MPa), and poor thermal stability (temperature tolerance >150°C), providing a new path for high-safety, high-energy-density solid-state batteries.

[0060] The solid-state battery of the present invention uses the above-mentioned composite solid-state electrolyte membrane, which has excellent comprehensive properties such as ionic conductivity and inhibition of lithium dendrites, and can effectively improve the energy density, cycle life, rate performance and safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a cross-sectional schematic diagram of the battery structure;

[0062] Figure 2 Arrhenius linear fitting curves of conductivity activation energy of composite solid electrolyte and commercial glass fiber separator at seven temperatures;

[0063] Figure 3 This is the linear voltammetric curve of the composite solid electrolyte and commercial glass fiber separator;

[0064] Figure 4 This is the current-time diagram of the lithium ion transfer number in the composite solid electrolyte separator lithium symmetric battery. The inset is the Nyquist impedance diagram of the battery before and after the test.

[0065] Figure 5 The lithium symmetric cycle diagram of the composite solid electrolyte separator and the commercial glass fiber separator;

[0066] Figure 6 ,7 is the cycle time diagram of batteries with different structures;

[0067] Figure 8 This is the lithium symmetric cycle diagram of composite solid electrolyte membranes with different components. DETAILED DESCRIPTION

[0068] The present invention relates to an innovative battery structure of a solid-state lithium metal battery composite positive electrode with a composite solid electrolyte membrane based on glass fiber. Figure 1 . This structural design aims to improve energy density and safety while reducing costs. Before describing the present invention in detail, it should be pointed out that although the following description provides specific embodiments, the scope of protection of the present invention is not limited to these specific examples and methods.

[0069] In order to better understand the advantages and effects of the present invention, we will describe in detail through a series of examples. In these examples, unless otherwise stated, all raw materials, reagents, instruments and equipment used are available on the market or can be obtained by existing methods.

[0070] During the electrochemical test, we used a CHI660E electrochemical workstation to evaluate the performance of the composite solid electrolyte. The conductivity was determined by electrochemical AC impedance spectroscopy. The specific test method is to use stainless steel (SS) as an electrode in the temperature range of 25 ℃ to 105 ℃ to construct a stainless steel (SS) / electrolyte / stainless steel (SS) battery system. During the test, we applied an AC voltage amplitude of 10 mV and tested in the frequency range of 0.1 Hz to 100 kHz to obtain the bulk resistance of the electrolyte and calculate the activation energy based on this.

[0071] To determine the electrochemical window of the composite solid-state electrolyte, we performed linear sweep voltammetry. This test used a two-electrode system with a stainless steel electrode as the working electrode and a lithium metal sheet as the reference electrode. The sweep range was set between 0 and 6 V at a scan rate of 2 mV / s to ensure accurate results.

[0072] In addition, we also tested the lithium ion migration ability in the electrolyte by chronocoulometry. This test used a lithium metal / composite solid electrolyte / lithium metal battery system with a step potential set to 10 mV to evaluate the lithium ion migration efficiency. -2 Long-cycle tests of current density are conducted to explore the cyclic stability of solid electrolyte membranes to lithium plating and stripping.

[0073] For the charge and discharge test of solid-state lithium batteries, we used the Land battery test system. The test voltage range was set between 2 and 4.5 V according to different systems. The capacity test was set at 50 mA g -1 Current density.

[0074] Through these detailed examples, we demonstrate the potential of this invention to improve the performance of solid-state lithium batteries. These tests not only demonstrate the superior performance of the composite solid-state electrolyte, but also provide important reference for the future development of solid-state lithium batteries.

[0075] Example 1

[0076] In the following examples, the inorganic particles of the positive electrode materials used in the preparation of the composite solid electrolyte are lithium aluminum titanium phosphate and lithium bis(trifluoromethanesulfonyl)imide. Carbon nanotubes are the positive electrode active material. LATP solid electrolyte refers to a new type of electrolyte made by combining lithium aluminum titanium phosphate compounds with polymers. Lithium aluminum titanium phosphate has advantages such as good chemical stability, high room temperature ionic conductivity, safety and reliability, good mechanical properties, and low internal resistance, making it suitable as a solid electrolyte in terms of lithium ion conduction. LATP ion conductivity is relatively high 10 -4 -10 -3 S / cm, and can be directly used as an inorganic solid electrolyte. The composite solid electrolyte structure only requires the inorganic material to have the ability to conduct lithium ions, and has no requirements for electronic conductivity or chemical or electrochemical stability. In summary, LATP meets the requirements for inorganic particle raw materials in the present invention.

[0077] In the following examples, the polymer binder used in preparing the composite solid electrolyte was polyvinylidene fluoride (PVDF). PVDF is a commonly used binder and separator material in the battery field, exhibiting excellent bonding, chemical stability, thermal stability, and flexibility. The solvent used was N,N-dimethylformamide (DMF). The commercial glass fiber used was GF / F.

[0078] The preparation process of the composite solid electrolyte film provided in this embodiment is as follows:

[0079] 0.4g PVDF-HFP and 0.1g LiTFSI were dissolved in 2mL DMF as solution A. 0.4g LATP was dispersed in 1mL acetone as solution B. Use a pipette to transfer solution B to solution A and stir continuously at room temperature to obtain a precursor solution. Soak the commercially purchased glass fiber GF / F in the precursor solution for 24h to allow the precursor slurry to fully wet the glass fiber. Then, take it out and place it in a 120℃ environment. Vacuum dry it to obtain a composite solid electrolyte GF / F (CSE). Within the test temperature range of 25℃ to 105℃, at 25℃, the ionic conductivity can reach 2.21×10 -4 S cm -1 As the temperature increases, the ionic conductivity of CSE increases linearly. At 105℃, the ionic conductivity can reach 6.66×10 -4 S cm -1 The ionic conductivity has a good linear relationship with temperature. The conductivity of lithium ions in the separator conforms to the typical Arrhenius law. The activation energy of the CSE separator (6.19 kJmol -1 ) is lower than commercial glass fiber GF / F (9.89 kJ mol -1 ), indicating that the electrochemical reaction of the battery of the present invention is easier to proceed. Figure 2The electrochemical window of its composite solid electrolyte membrane can reach about 5 V, while the commercial glass fiber GF / F shows a trace current at about 4.2 V, which may be accompanied by a trace decomposition of the electrolyte. The GF / F (CSE) membrane significantly improves the electrochemical window and its high-voltage electrochemical stability is better than that of the commercial glass fiber GF / F. The electrochemical test results are shown in Figure 3 In a lithium symmetric battery, the time-current curve was recorded and the electrochemical impedance was tested. The calculated lithium ion transfer number of the GF / F (CSE) separator was 0.55, which is higher than that of the liquid system. The electrochemical test results are shown in Figure 4 At 0.05 mA cm -2 Current density, cut-off capacity 0.05 mAh cm -2 Under these conditions, the stability of lithium plating and stripping cycles was tested. The glass fiber composite solid electrolyte GF / F (CSE) always maintained cycle stability and outperformed the commercial glass fiber GF / F. The electrochemical test results are shown in Figure 5 .

[0080] The application of the composite solid electrolyte in the solid-state lithium-oxygen battery in this embodiment is as follows.

[0081] In this embodiment, the negative electrode of the solid-state lithium battery is a lithium metal negative electrode layer, and the positive electrode is a composite CNTs positive electrode with the same components as the solid electrolyte precursor slurry. The raw materials and preparation process of the composite solid positive electrode layer are as follows: the positive electrode active material uses commercial CNTs, LATP, LITFSI, and binder PVDF, and is fully stirred in N-methylpyrrolidone solvent at a mass ratio of 4:2:1:1 to obtain a positive electrode slurry, which is then coated on the surface of carbon paper, vacuum-dried at 100°C, and cut to obtain a positive electrode sheet, and an electrochemical test is performed. The method using the raw materials and process steps of the present invention is compared with commercial glass fiber, and the lithium oxygen solid-state battery is 50mAg -1 At the charge and discharge current density, the cut-off capacity is 300mAh g -1 Compared with pure commercial glass fiber diaphragm, the number of cycles and cycle time are nearly doubled, achieving better technical results and showing good cycle performance. The test results are shown in Figure 6 .

[0082] Example 2

[0083] In the following examples, the inorganic particles of the positive electrode materials used in the preparation of the composite solid electrolyte are lithium aluminum titanium phosphate and lithium bis(trifluoromethanesulfonyl)imide, and carbon nanotubes are the positive electrode active material. LATP solid electrolyte refers to a new type of electrolyte made by combining lithium aluminum titanium phosphate compounds with polymers. Lithium aluminum titanium phosphate has advantages such as good chemical stability, high room temperature ionic conductivity, safety and reliability, good mechanical properties, and low internal resistance, making it suitable as a solid electrolyte in terms of lithium ion conduction. LATP has a high ion conductivity of 10-4 -10 -3 S / cm, and can be directly used as an inorganic solid electrolyte. The composite solid electrolyte structure only requires the inorganic material to have the ability to conduct lithium ions, and has no requirements for electronic conductivity or chemical or electrochemical stability. In summary, LATP meets the requirements for inorganic particle raw materials in the present invention.

[0084] In the following examples, the polymer binder used in the preparation of the composite solid electrolyte is polyvinylidene fluoride. Polyvinylidene fluoride is a commonly used binder and separator material in the battery field, with excellent bonding ability, chemical stability, thermal stability, and flexibility. The solvent used is N,N-dimethylacetamide.

[0085] This example explores and explores a composite solid-state cathode-glass fiber composite solid-state electrolyte structure for solid-state lithium-oxygen batteries. The preparation process of the composite solid-state cathode and electrolyte structure is as follows:

[0086] Dissolve 0.4g PVDF-HFP and 0.1g LiTFSI in 2mL DMF as solution A. Disperse 0.4g LATP in 1mL acetone as solution B. Use a pipette to transfer solution B to solution A and stir continuously at room temperature to obtain a precursor solution. The composite solid electrolyte is prepared by soaking our commercially purchased glass fiber GF / F in the precursor solution for 24 hours. After the precursor slurry fully wets the diaphragm, it is taken out and placed in a 120°C environment and vacuum dried. The electrochemical test results are shown in the attached figure. The application of the composite solid electrolyte in solid-state lithium metal batteries in this example is as follows.

[0087] In this example, the negative electrode of the solid-state lithium metal battery is lithium metal, and the positive electrode is a metal catalyst positive electrode. The raw materials and preparation process of the positive electrode are as follows: First, 10 mg of the electrode is added to 1 mL of N-methylpyrrolidone (NMP) in polyvinylidene fluoride (PVDF) and ultrasonically treated until a clear and transparent solution is formed. 40 mg of Ru@CNT, 20 mg of LATP, and 10 mg of LITFSI are mixed evenly in a mortar. Then the pre-dissolved PVDF in NMP solution is transferred to the mixed powder by a pipette, and the mixture is crushed in a cell crusher for more than 20 minutes and stirred overnight to ensure that CNTs, LITFSI and LATP are fully dispersed. After obtaining a slurry with a uniform dispersion of active substances, it is coated on one side of the composite solid electrolyte membrane, heated and dried at 60 ° C, and then repeated coating is performed. The loading amount is about 0.2-0.6 mg cm -2 Finally, the composite structure was dried in a vacuum oven at 120°C overnight and then stored in a glove box. Compared with the traditional layered structure in Example 1, the lithium-oxygen solid-state battery at 50 mA g -1 At a charge and discharge current density of 300 mAh g-1 Shows the best cycle performance.

[0088] The effect of Example 2 is better than that of Example 1. The reasons are analyzed in combination with the following comparative examples: On the one hand, the positive electrode-electrolyte composite structure (CSEI) is designed with a stable porous skeleton and a high ionic conductivity coating layer, combined with an optimized interface contact composite process, which can more significantly accelerate the positive electrode reaction mass transfer process, build a more efficient high-speed ion transmission channel, and greatly reduce the interface impedance between the positive electrode and the glass fiber composite solid electrolyte membrane, thus achieving a more compatible positive electrode-electrolyte contact interface. On the other hand, the integrated structure is deployed in the solid-state battery to enable continuous transmission of internal lithium ions, expand the three-phase reaction interface, and improve the stability of the battery during the cycle. This shows that the lithium-oxygen solid-state battery using CSEI based on a glass fiber composite solid electrolyte can achieve better technical results. The electrochemical test results are shown in Figure 6 and 7 contrast.

[0089] Comparative Example 1

[0090] Solution A was prepared by dissolving 0.4 g of PVDF-HFP and 0.1 g of LiTFSI in 2 mL of DMF. Solution B was prepared by dispersing 0.4 g of LATP in 1 mL of acetone. Solution B was transferred to Solution A using a pipette and stirred continuously at room temperature to obtain a precursor solution. The layered structure was directly coated with a doctor blade to produce a 25 μm thick separator. A single layer of the membrane, when used directly as a solid electrolyte, exhibits high electronic conductivity and is prone to micro-shorting or even short circuiting, resulting in poor battery performance or even failure. Therefore, a lithium solid-state battery was assembled using this solid electrolyte, with a lithium metal anode and a CNTs composite cathode. During cyclic charge-discharge testing, the battery exhibited discharge decay after the 260th cycle. During charging, the battery's charge overpotential increased, leading to low coulombic efficiency and severe capacity fade. This was attributed to the uneven and stable transport of lithium during the charge-discharge process, which resulted in lithium dendrites. Furthermore, the discharge product, Li₂O₂, is insulating and non-conductive, leading to the accumulation of side reaction products and battery failure. This phenomenon is consistent with the behavior of high-electronic conductivity inorganics in solid-state electrolytes. At 50 mA g -1 At a charge and discharge current density of 300 mAh g -1 The cycling performance shown is far inferior to that shown in the examples. The difference between Example 1 and Comparative Example 1 is the presence or absence of a glass fiber substrate, which makes the cycling performance of Example 1 better than that of Comparative Example 1. The reason is that the three-dimensional conductive network of glass fiber improves the reaction kinetics of lithium ions, oxygen and electrons, indicating that the use of glass fiber-based composite solid electrolyte membrane can achieve better technical effects. The electrochemical test results are shown in Figure 6 and 7 contrast.

[0091] Comparative Example 2

[0092] First, 1.88 g of ammonium metavanadate (NH₄VO₃) and 1.12 g of oxalic acid dihydrate (C₂H₂O₄·2H₂O) were dissolved in 60 mL of distilled water and stirred at 40°C until a homogeneous yellow solution formed. 0.22 g of lithium hydroxide (LiOH·H₂O) was added and stirred for 30 minutes. The pH was adjusted to 3.5. The solution was transferred to a 100 mL polytetrafluoroethylene autoclave and hydrothermally reacted at 170°C for 48 hours. After cooling, an orange solution with a pH of 7 was obtained. Sample A-LVO was prepared by evaporating a portion of the solution at 100°C to form a gel. After grinding, the gel was annealed at 400°C under an argon atmosphere for 2 hours to obtain a deep red product. Sample C-LVO was prepared by adding 1 g of 2-ethylimidazole to the remaining solution. After stirring for 25 minutes, the solution was transferred to a preheated 400°C box furnace and burned for 2 hours. The product was then ground to obtain the product. A lithium battery was assembled using this 20 μm separator, with a lithium metal anode and a carbon-based cathode. The battery showed a continuous attenuation of efficiency and capacity in the cyclic charge and discharge test. After 210 cycles, the battery failed shortly thereafter. At the same time, on the surface of the negative electrode, the uneven deposition of lithium ions may lead to the formation of lithium dendrites. The single-layer polymer separator layer has poor mechanical strength and cannot effectively inhibit the growth of lithium dendrites. Lithium dendrites will penetrate the separator, causing a short circuit between the positive and negative electrodes, resulting in a sudden drop in battery capacity, and in severe cases, it may also cause safety problems. This phenomenon is consistent with the behavior of polymer separators in lithium metal batteries. The difference between the different components of Example 1 and Comparative Example 2 makes the cycle of Example 1 better than that of Comparative Example 2. The reason is that the glass fiber has a three-dimensional conductive network that improves the reaction kinetics of lithium ions, oxygen and electrons. At the same time, PVDF-HFP, LITFSI, and LATP work together to ensure interface compatibility, provide tough mechanical strength and fast lithium ion conduction channels, indicating that the use of a glass fiber-based composite solid electrolyte membrane can achieve better technical effects. The electrochemical performance of this comparative example is also not as good as that of Comparative Example 1, highlighting the advantages of the solid electrolyte separator of the present invention. The test results are shown in Figure 6 and 7 contrast.

[0093] Comparative Example 3

[0094] 0.4g PVDF-HFP, without adding lithium salt, was dissolved in 2mL DMF as solution A. 0.4g LATP was dispersed in 1mL acetone as solution B. Solution B was transferred to solution A using a pipette, and the mixture was stirred continuously at room temperature to obtain a precursor solution. The composite solid electrolyte was prepared by soaking the commercially purchased glass fiber GF / F in the precursor solution for 24 hours, allowing the precursor slurry to fully wet the diaphragm, taking it out and placing it in a 120°C environment, and vacuum drying it. Another group dissolved 0.4g PVDF-HFP and 0.1g LiTFSI in 2mL DMF. Without adding LATP, the mixture was stirred continuously at room temperature to obtain a precursor solution. The composite solid electrolyte was prepared by soaking the commercially purchased glass fiber GF / F in the precursor solution for 24 hours, allowing the precursor slurry to fully wet the diaphragm, taking it out and placing it in a 120°C environment, and vacuum drying it. 0.05 mAcm -2 Long-term cycle test of current density was conducted to explore the cycling stability of different components of glass fiber-based solid electrolyte separator to lithium plating and stripping. In lithium symmetric battery, at 0.1 mA cm -2 Current density, cut-off capacity 0.1 mAh cm -2 Under the same conditions, the stability of lithium plating and stripping cycles was tested. Comparing Example 1 with Comparative Example 3, the components of the present invention are PVDF-HFP, LITFSI, and LATP, and the glass fiber composite solid electrolyte GFF (CSE) maintains cycle stability within 500 hours and maintains the minimum polarization voltage, while the battery lacking LITFSI and LATP only shows fluctuations in lithium ion plating and stripping after 280 hours and 380 hours, and abnormal polarization causes battery failure. Therefore, compared with Example 1, the performance of Example 1 is the best. It is proved that only by adopting the components and proportions of the present invention can the best technical effect be achieved. Test results are shown in Figure 8 .

[0095] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a composite solid electrolyte membrane based on glass fiber, characterized in that: The glass fiber is immersed in a solid electrolyte precursor solution, wherein the solid electrolyte precursor solution includes a lithium salt, a polymer matrix and an inorganic filler, and is vacuum-dried to obtain a composite solid electrolyte membrane based on the glass fiber.

2. The method for preparing a glass fiber-based composite solid electrolyte membrane according to claim 1, wherein: The glass fiber is immersed in the solid electrolyte precursor solution for 20 to 28 hours, and the loading amount of the solid electrolyte precursor solution in the glass fiber is 4 to 6 mg / cm 2 .

3. The method for preparing a glass fiber-based composite solid electrolyte membrane according to claim 1, wherein: The polymer substrate is one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and polymethyl acrylate; the inorganic filler is Li 1.3 Al 0.3 Ti 1.7 (PO4)3,Li7La3Zr2O 12 , Li3PO4; the lithium salt is LiTFSI or Li6PS5Cl.

4. The method for preparing a glass fiber-based composite solid electrolyte membrane according to claim 1, wherein: The preparation method of the solid electrolyte precursor solution includes: dissolving a polymer matrix and a lithium salt in DMF to form solution A; dispersing an inorganic filler in acetone to form solution B; transferring solution B into solution A, and continuously stirring at room temperature to obtain a solid electrolyte precursor solution.

5. A composite solid electrolyte membrane based on glass fiber, characterized in that: The method is described in any one of claims 1 to 4.

6. Use of the glass fiber-based composite solid electrolyte membrane according to claim 5 in a solid-state lithium battery.

7. The use according to claim 6, characterized in that The solid-state lithium battery comprises a composite solid-state positive electrode layer, the glass fiber-based composite solid-state electrolyte separator layer according to claim 5, and a lithium metal negative electrode layer.

8. The use according to claim 7, characterized in that The composite solid-state positive electrode layer includes a positive electrode substrate and a positive electrode slurry coated on the positive electrode substrate; the positive electrode substrate is carbon paper or carbon cloth; the positive electrode slurry includes a positive electrode active material, an inorganic filler, a lithium salt and a polymer binder.

9. The use according to claim 8, characterized in that The positive electrode active material is one of carbon nanotubes, conductive carbon black, Ketjen black, Ru@CNTs, Ru / TiO2 / CNTs, TEMPO-COF, and FePc catalytic materials; the polymer binder is PVDF, PTFE, or its derivatives or blended polymers.

10. The use according to claim 8, characterized in that The preparation method of the positive electrode slurry comprises: mixing a positive electrode active material, an inorganic filler, a lithium salt and a polymer binder in an organic solvent, wherein the organic solvent is N-methylpyrrolidone.

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