A multilayer composite solid-state electrolyte

Abstract

The application discloses a multilayer composite solid electrolyte, and belongs to the technical field of solid electrolytes. The multilayer composite solid electrolyte is formed by sequentially stacking a positive electrode side functional layer, an intermediate support layer and a negative electrode side functional layer, wherein the positive electrode side functional layer comprises an inorganic solid electrolyte and a fluorine-containing polymer; the intermediate support layer comprises a polymer matrix, a porous material modified with an anion group on the surface and a lithium salt; and the negative electrode side functional layer comprises a polymer with a strong coordination group and a lithium salt. The application allocates different functions to the functional layers with different compositions and structures through gradient functional design of the solid electrolyte, and comprehensively realizes performance balance and balance of ion conductivity, mechanical strength and interface stability by utilizing the synergistic effect.

Description

Technical Field

[0001] This application belongs to the field of solid electrolyte technology, specifically relating to a multilayer composite solid electrolyte. Background Technology

[0002] In traditional lithium-ion batteries, liquid electrolytes pose serious safety hazards, making solid electrolyte materials a key research area.

[0003] However, a single solid electrolyte material cannot simultaneously achieve multiple performance characteristics: inorganic solid electrolytes (such as sulfides) have high room temperature ionic conductivity but poor flexibility, poor interfacial contact, and are sensitive to air; polymer solid electrolytes (such as polyethylene oxide (PEO)) have good processability but low room temperature ionic conductivity (typically <10). -4 (S / cm). A single homogeneous electrolyte structure cannot simultaneously meet the multiple requirements of high ionic conductivity, high mechanical strength, and a stable electrode / electrolyte interface, which severely restricts the performance of all-solid-state batteries. At the same time, the high interfacial impedance between the electrode and the solid electrolyte, the numerous side reactions, and the volume changes of the electrode during charging and discharging require the electrolyte to have both flexibility and strength.

[0004] Therefore, there is an urgent need to develop a new type of solid electrolyte that can systematically solve the problem of synergistic cooperation between multi-scale ion transport and mechanical support. Summary of the Invention

[0005] In view of this, the primary objective of this application is to overcome the aforementioned deficiencies of the prior art and provide a multilayer composite solid electrolyte. Existing homogeneous or simple bilayer electrolytes struggle to resolve the contradiction between ionic conductivity, mechanical strength, and interfacial stability. The improvement of this application lies in providing a functionally graded multilayer composite structure. By assigning different functions to functional layers with varying compositions and structures, and utilizing their synergistic effects, the aforementioned problems are systematically solved.

[0006] To achieve the above objectives, this application adopts the following technical solution: One aspect of this application discloses a multilayer composite solid electrolyte, which is formed by sequentially stacking a positive electrode side functional layer, an intermediate support layer, and a negative electrode side functional layer, wherein: The positive electrode side functional layer includes an inorganic solid electrolyte and a fluoropolymer. The intermediate support layer comprises a polymer matrix, a porous material with surface-modified anionic groups, and a lithium salt; The negative electrode side functional layer comprises a polymer with strong coordinating groups and a lithium salt.

[0007] Another aspect of this application discloses a solid-state battery comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte is the multilayer composite solid electrolyte described in this application.

[0008] The beneficial effects of this application are: This application overcomes the performance limitations of homogeneous electrolytes through a functionally graded design. Specifically: (1) The positive electrode side functional layer utilizes the voltage stability of fluoropolymers and the high ionic conductivity of inorganic solid electrolytes to synergistically broaden the electrochemical window and improve high voltage withstand capability.

[0009] (2) The intermediate support layer utilizes the regular channels and surface anionic groups of the porous material to confine and enrich lithium ions, thereby synergistically improving ionic conductivity and lithium ion transference number (tLi). + >0.5), while also providing mechanical support.

[0010] (3) The functional layer on the negative electrode side uses strong coordinating groups (such as -CN) to complex transition metal ions and stabilize the lithium interface, effectively suppressing side reactions.

[0011] This partitioned synergistic design enables the electrolyte to exhibit high room-temperature ionic conductivity (>10⁻⁶) on a macroscopic scale. -3 S / cm), wide electrochemical window (>4.8V) vs. Li + The high mechanical strength and high Li-N2 content significantly improve the cycle life and safety of the battery. Detailed Implementation

[0012] The embodiments of this application will be clearly and completely described below. The technical solutions in the embodiments described below are exemplary and only possible technical implementations of this application, not all possible implementations. Those skilled in the art can combine the embodiments of this application to obtain other embodiments without creative effort, and these embodiments are also within the protection scope of this application.

[0013] The first aspect of this application discloses a multilayer composite solid electrolyte, which is formed by sequentially stacking a positive electrode side functional layer, an intermediate support layer, and a negative electrode side functional layer, wherein: The positive electrode side functional layer includes an inorganic solid electrolyte and a fluoropolymer. The intermediate support layer comprises a polymer matrix, a porous filler with surface anionic groups, and a lithium salt; The negative electrode side functional layer comprises a polymer with strong coordinating groups and a lithium salt.

[0014] (a) Positive electrode side functional layer The positive electrode side functional layer in this application includes an inorganic solid electrolyte and a fluoropolymer.

[0015] As stated in this application, inorganic solid electrolyte is a common term in the art. This application does not specifically limit the type of inorganic solid electrolyte; any known or independently developed inorganic solid electrolyte in the art can be used in this application. The inorganic solid electrolyte is selected from at least one of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, or nitride solid electrolytes. Its function is to provide high bulk ionic conductivity and compensate for the shortcomings of polymer solid electrolytes. As a specific example, the sulfide solid electrolyte can be Li... 10 GeP2S 12 Li6PS5Cl, Li7P3S 11 The solid electrolyte may be at least one of the following: the halide solid electrolyte may be at least one of Li3YCl6 and Li3YBr6; the oxide solid electrolyte may be at least one of LLZO and LATP; the nitride solid electrolyte may be at least one of Li3N and Li3BN2, but is not limited thereto.

[0016] In this application, a fluoropolymer is introduced into the functional layer on the positive electrode side to improve the high-voltage stability of the interface. In a preferred embodiment, the fluoropolymer is a fluoropolymer co-coordinated with oxygen composed of repeating units -AOBO-, where A is -(CH2)2- and B is -(CF2)3-. As a preferred example, the general formula of the fluoropolymer co-coordinated with oxygen is as follows: [—(CH2)2—O—(CF2)3—O—] n ; The number of repetitions, n, is any integer between 30 and 350, preferably between 50 and 200. The number-average molecular weight (Mn) is preferably 3000-10000, more preferably 5000-8000. It is understood that molecular weight directly affects the polymer's chain mobility and the mechanical properties after film formation. Therefore, to ensure the polymer possesses good film-forming properties, moderate mechanical strength, and excellent chain mobility, the number of repetitions and the number-average molecular weight can be appropriately adjusted, thereby facilitating the formation of a dense, robust, and ion-transporting functional layer on the positive electrode side.

[0017] This application utilizes a blend of fluoropolymers and inorganic solid electrolytes to enhance the ionic conductivity of the positive electrode side functional layer. This is primarily due to the unique structure of the fluoropolymer, which possesses excellent ion conduction properties, while the inorganic solid electrolyte further improves the overall ionic conductivity, providing an efficient channel for ion transport during battery charging and discharging.

[0018] To further improve film formation and mechanical integrity, an appropriate amount of polymer binder can be added to the functional layer on the positive electrode side. The polymer binder can be of a type well-known in the art, and specific examples include, but are not limited to, at least one of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN).

[0019] There are no particular restrictions on the proportions of the components; those skilled in the art can determine them based on performance requirements or through experimental methods. In some specific examples, the proportions of each component in the positive electrode side functional layer are as follows: inorganic solid electrolyte 5wt%-30wt%, fluorinated oxygen polymer 60wt%-90wt%, and polymer binder 5wt%-15wt%.

[0020] For the preparation of the positive electrode side functional layer, well-known thin film preparation methods in the art can be used, and those skilled in the art can make specific selections based on the components and raw materials. As an example, the positive electrode side functional layer is prepared by casting in this application, with a film thickness of 10-50 μm. Specific film formation parameters can be selected as needed and are not particularly limited.

[0021] In some specific examples, the inorganic solid electrolyte, fluorinated oxidizing polymer, and polymer binder are added to an organic solvent (such as NMP) according to a specified ratio. Under nitrogen or rare gas protection, the mixture is dispersed at 3000-5000 rpm for 2-3 minutes to ensure uniform dispersion of all components and form a stable slurry. Subsequently, the slurry is cast onto a polymer-based film; for example, the casting speed is controlled at 0.5-1 m / min. After casting, the film is vacuum-dried at 60-80℃ for 8-12 hours, and finally the solvent is completely removed to obtain the functional layer on the positive electrode side.

[0022] The polymer base film used for casting can be PET, PP, PE or PI film with a thickness of 50-100μm, which are commonly used in this field.

[0023] (b) Intermediate support layer The intermediate support layer in this application includes a polymer matrix, a porous material with surface-modified anionic groups, and a lithium salt.

[0024] The polymer matrix is ​​used to provide a continuous mechanical support framework and dissolve lithium salts, and is preferably a polyether polymer, such as polyethylene oxide (PEO), polypropylene oxide (PPO), or a block copolymer containing them.

[0025] In some specific examples, the polymer matrix is ​​preferably a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (PEO-PPO-PEO). More preferably, its number average molecular weight is 5,000-15,000, and the mass percentage of poly(ethylene oxide) segments is 70%-80%, for example, the brand Pluronic F127 (Mn≈12,600, PEO content approximately 70%).

[0026] The porous material with surface-modified anionic groups is used to construct fast lithium-ion transport channels and improve lithium-ion transference number. Preferably, the porous material is a lithium sulfonate-modified covalent organic framework (COF-SO3Li) or a metal-organic framework (MOF-SO3Li).

[0027] In some specific examples, the pore size of the porous material is preferably 1-10 nm, more preferably 2-5 nm. A suitable pore size ensures the rapid passage of lithium ions and their solvation shell, while maintaining the confinement effect and sieving function of the pores, and simultaneously giving the material a suitable specific surface area and mechanical strength. As a preferred example, the grafting amount of lithium sulfonate groups is preferably 0.2-3.0 mmol / g, more preferably 0.5-2.0 mmol / g. Choosing an appropriate grafting amount achieves a suitable balance between providing sufficient lithium source and maintaining unobstructed pores, ensuring sufficient lithium ion transport sites while avoiding pore blockage and hindering ion transport. Furthermore, the porous materials and lithium sulfonate-modified porous materials in this application can be prepared using methods commonly used in the art. As an example, taking COF materials as an example, terephthalaldehyde is condensed with 1,3,5-tris(4-aminophenyl)benzene to form an imine-linked COF framework, and then lithium sulfonate groups are grafted onto the framework via a post-synthetic modification method involving concentrated sulfuric acid sulfonation and lithium hydroxide neutralization.

[0028] As described in this application, the lithium salt is a conventional electrolyte salt in the art, and any common lithium salt in the art can be used. As a preferred example, the lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB).

[0029] There are no particular restrictions on the proportions of the components; those skilled in the art can determine them based on performance requirements or through experimental methods. In some specific examples, the proportions of the components in the intermediate support layer are as follows: polymer matrix 60-85 wt%, porous material 10-30 wt%, and lithium salt 3-10 wt%.

[0030] In this application, the intermediate support layer can be prepared by hot pressing. As a specific example, the polymer matrix, porous material, and lithium salt are mixed in proportion, and an appropriate amount of anhydrous ethanol is added as a dispersant. The mixture is ball-milled at 200-300 rpm for 4-6 hours to ensure that the components are fully mixed and homogeneous, forming a mixed powder. The mixed powder is placed in a mold and hot-pressed to fully melt the powder and form a dense film (hot-pressing temperature: 100-120℃, pressure: 5-8 MPa, time: 30-60 min). After cooling, the film is removed to obtain the intermediate support layer.

[0031] (c) Negative electrode side functional layer In this application, the bottom layer on the negative electrode side comprises a polymer with strong coordinating groups and a lithium salt. Preferably, a cyano-modified polyether polymer, such as cyanoethyl-modified polyethylene oxide (PEO), is used. The gel layer formed by the cyano-modified PEO and the lithium salt suppresses the dissolution of the positive electrode by complexing transition metal ions with the cyano groups. At the same time, the good flexibility and ionic conductivity of the gel layer, as well as the ability of the cyano groups to complex with the transition metal ions dissolved from the positive electrode material, reduce the negative impact of transition metal ions on the battery.

[0032] In this context, cyano-modified PEO refers to a derivative obtained by substituting the hydrogen atom on the hydroxyl group (-OH) of the PEO molecule with cyanoethyl. As a preferred example, the degree of substitution of the cyanoethyl is 10%-35%. A suitable degree of substitution can balance complexation function with good mechanical properties, thereby effectively suppressing side reactions caused by the dissolution of metal ions at the positive electrode and maintaining excellent flexibility to achieve good interfacial contact with the negative electrode. In some specific examples of this application, cyano-modified PEO is prepared by reacting PEO with acrylonitrile in the presence of an alkaline catalyst via a cyanoethylation reaction. Specific details can be found in existing technologies and will not be elaborated here.

[0033] The lithium salt for this functional layer can also be of a type well known in the art. As a preferred example, the lithium salt is at least one of lithium trifluoromethanesulfonylimide and lithium hexafluorophosphate.

[0034] In a specific example in this application, preferably, the cyano-modified PEO and lithium salt are configured with a molar ratio of ether oxygen unit (EO) to Li of 8:1 to 18:1.

[0035] This layer can be prepared using a coating method. For example, after sampling the molar ratio of cyano-modified PEO to lithium salt, it is added to anhydrous acetonitrile solvent and stirred at 70-80℃ for 2-3 hours until completely dissolved to form a homogeneous solution. The solution is then uniformly coated onto one side of the intermediate support layer at a coating speed of 0.3-0.5 m / min. After coating, it is vacuum dried at 50-60℃ for 6-8 hours to remove the solvent, yielding the functional layer on the negative electrode side.

[0036] It is understood that the thickness of each layer in a multilayer composite solid electrolyte can be optimized or adjusted according to actual conditions, without any particular limitation. In some specific examples of this application, the thickness of the positive electrode side functional layer is 10-50 μm; and / or, the thickness of the intermediate support layer is 10-30 μm; and / or, the thickness of the negative electrode side functional layer is 5-20 μm.

[0037] The multilayer composite solid electrolyte is formed using a well-known hot-pressing method. Specifically, the positive electrode functional layer and the intermediate support layer containing the negative electrode functional layer are sequentially stacked and then hot-pressed at 100-120℃ and 5-8MPa for 20-30 minutes to ensure tight bonding of the three layers and form a multilayer composite solid electrolyte. It is important to note that during the hot-pressing process, temperature and pressure need to be precisely controlled to ensure no air bubbles or delamination between the layers, and a tight interfacial bond, thus guaranteeing the overall performance of the composite solid electrolyte.

[0038] The second aspect of this application discloses a solid-state battery comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte is the multilayer composite solid electrolyte described in the first aspect of this application. Thanks to the synergistic cooperation of the functional layers in each region, the room-temperature ionic conductivity, lithium-ion transference number, mechanical strength, and cycle stability under high voltage of the solid-state battery can be significantly improved.

[0039] In a specific example in this application, the positive electrode is formed by coating a positive electrode slurry onto a positive electrode current collector. The positive electrode slurry includes a positive electrode active material, a binder, and a conductive agent, with a mass ratio of (90-98):(1-5):(1-5). All of these materials can be common types in the art and there are no particular limitations.

[0040] Examples of positive electrode active materials include, but are not limited to, lithium cobalt oxide, lithium manganese oxide, and layered oxides such as lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. Conductive agents may include carbon nanotubes.

[0041] In some preferred examples, the adhesive is preferably a dual-network adhesive, which is compounded from silicone-modified polyimide and phenylene ring-containing nitrile rubber in a mass ratio of 3:1. The silicone-modified polyimide has a number average molecular weight of 5000-1000 and a silicon oxide segment content of 30-50%; and / or, the phenylene ring-containing nitrile rubber contains 30-80% acrylonitrile.

[0042] Excellent adhesion, flexibility, and peel strength are achieved through a dual-network binder. Specifically, silicone-modified polyimide has good thermal stability and mechanical properties. The introduction of siloxane segments enhances the flexibility of the binder and its adhesion to the electrode material. Meanwhile, nitrile rubber containing benzene rings can provide additional adhesion and flexibility. When compounded with the main binder, it can effectively adapt to the volume changes of the positive and negative electrodes. When the electrode expands, the flexible network can reversibly deform to absorb stress, and when it shrinks, the rigid network maintains the integrity of the electrode structure and prevents the material from falling off.

[0043] More preferably, the positive electrode further includes an in-situ polymerized polyionic liquid layer containing lithium salt LiTFSI, with a thickness of 50-200 nm. Introducing this polyionic liquid layer can improve the interfacial contact between the positive electrode and the electrolyte, reduce interfacial impedance, and help improve ion conduction efficiency.

[0044] The polyionic liquid layer is formed by in-situ polymerization of a lithium-containing polymerizable ionic liquid monomer. The lithium salt is a conventional type in the art, such as at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium bis(fluorosulfonyl)imide (LiFSI). The polymerizable ionic liquid monomer is any one of imidazolium, pyrrolidineonium, or quaternary ammonium salt ionic liquid monomers containing a polymerizable group. The polymerizable group can be, for example, at least one of vinyl or acryloyloxy groups, but is not limited to these. Specific examples include, but are not limited to, 1-vinyl-3-ethylimidazolium salt. The in-situ polymerization method varies depending on the specific monomer type and initiation method; for example, it can be thermally initiated or photoinitiated. These specific polymerization methods can be carried out using any known methods in the art.

[0045] As an example, a 1-vinyl-3-ethylimidazolium salt ionic liquid monomer containing 0.5M-1.5M LiTFSI was mixed with 0.5wt% photoinitiator (Irgacure 1173) and coated onto the surface of the above-mentioned positive electrode. The mixture was then irradiated with ultraviolet light (wavelength 365nm, intensity 10mW / cm²) for 30 seconds under a nitrogen atmosphere to form a polyionic liquid layer through in-situ polymerization.

[0046] In some specific examples, during the preparation of the positive electrode, the positive electrode active material, binder, and conductive agent are first added to a solvent and dispersed for 2-3 hours under nitrogen protection using a high-speed disperser (3000-5000 r / min) to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of aluminum foil using a precision coating machine at a speed of 1-1.5 m / min. After coating, it is first dried with hot air at 80-100℃ for 1-2 hours, then vacuum dried at 120-140℃ for 4-6 hours. Finally, it undergoes ultraviolet curing (wavelength 254-365 nm, time 10-20 min) and roller pressing to control the compaction density to 3.4-3.5 g / cm³. 3 This yields the positive electrode sheet.

[0047] In a specific example of this application, the negative electrode is formed by coating a negative electrode slurry onto a negative electrode current collector. The negative electrode slurry includes a negative electrode active material, a binder, and a conductive agent in a mass ratio of (90-98):(1-5):(1-5). All of these can be common types in the art and are not particularly limited. Furthermore, the negative electrode active material, binder, and conductive agent can all be well-known or independently developed types in the art without any particular limitation.

[0048] In some preferred embodiments, a porous polyacrylonitrile-alumina composite layer is formed on the surface of the negative electrode, wherein the porous polyacrylonitrile-alumina composite layer is formed by chemical vapor deposition; the thickness of the porous polyacrylonitrile-alumina composite layer is 100-200 nm, and the porosity is 50-80%; in the porous polyacrylonitrile-alumina composite layer, the mass ratio of polyacrylonitrile to alumina is (1:1) to (4:1). This porous composite layer increases the contact area between the negative electrode and the electrolyte, thereby further facilitating ion transport, and the polyacrylonitrile-alumina composite layer can buffer the volume change of the negative electrode, further improving the cycle stability of the battery.

[0049] In some specific examples, the negative electrode in this application is prepared by adding the negative electrode, binder, and conductive agent to a solvent and dispersing them using a planetary ball mill (200-300 r / min) for 3-4 hours to form a negative electrode slurry. The negative electrode slurry is then coated onto a copper foil surface at a coating speed of 0.8-1.2 m / min. After coating, it is first dried with hot air at 80-90℃ for 2-3 hours, and then vacuum dried at 120-130℃ for 5-7 hours. Subsequently, a porous polyacrylonitrile-alumina composite layer is deposited on the negative electrode surface using chemical vapor deposition (CVD) technology at a deposition temperature of 200-250℃, a deposition pressure of 1-5 Pa, and a deposition time of 1-2 hours. The composite layer thickness is controlled at 100-200 nm, and the porosity at 50-80%, resulting in the negative electrode sheet.

[0050] The present application will be further illustrated below with reference to specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present application in any way.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0052] In addition, unless otherwise specified, methods without detailed conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0053] (i) Preparation of lithium sulfonate COF (COF-SO3Li) COF synthesis: In a pressure-resistant tube, 60 mg of terephthalaldehyde and 87 mg of 1,3,5-tris(4-aminophenyl)benzene were dissolved in a mixed solvent of mesitylene / dioxane (1 / 1 v / v, 3 mL), and 0.5 mL of 3M acetic acid aqueous solution was added. The tube was then subjected to a three-cycle process of freezing with liquid nitrogen, evacuating, and thawing before being sealed and placed in a 120°C oven for 72 hours.

[0054] Post-processing: After the reaction was completed, the yellow precipitate was collected by filtration and extracted with anhydrous tetrahydrofuran and acetone by Soxhlet extraction for 24 hours in sequence. Finally, it was vacuum dried at 120°C for 12 hours to obtain yellow imine COF powder.

[0055] Sulfonation and Lithification: 500 mg of the above COF powder was dispersed in 20 mL of concentrated sulfuric acid and stirred at 80°C for 12 hours. The reaction mixture was poured into 200 mL of ice water to precipitate, filtered, and washed with deionized water until the filtrate was neutral. The resulting solid (COF-SO3H) was dispersed in 100 mL of 1.0 M LiOH aqueous solution and stirred at room temperature for 6 hours for lithiation. The mixture was filtered, washed with water and ethanol, and dried under vacuum at 100°C to obtain the final product COF-SO3Li.

[0056] (ii) Preparation of cyano-modified PEO (cyanoethyl substitution degree 20%) 20 g of PEO with a number average molecular weight of approximately 200,000 was vacuum dried overnight at 60 °C. It was then dissolved in 150 mL of anhydrous DMSO. 0.5 g of KOH was added to the solution, and the mixture was stirred and activated for 1 hour at 70 °C under nitrogen protection. Acrylonitrile (10 mL) was slowly added dropwise, and the reaction was continued at 70 °C for 8 hours. After the reaction was complete, the solution was cooled to room temperature and precipitated in a large amount of diethyl ether (1.5 L). The fibrous solid was collected by filtration. The solid was redissolved in acetone (100 mL) and precipitated again in diethyl ether (1 L). This purification process was repeated twice. The final product was vacuum dried at 45 °C for 24 hours to obtain cyano-modified PEO.

[0057] (iii) The dual-network adhesive is compounded by organosilicon-modified polyimide and phenyl cyclohexane-containing nitrile rubber in a mass ratio of 3:1. The organosilicon-modified polyimide has a number average molecular weight of 7000 and a silicon-oxygen segment ratio of 40%. The phenyl cyclohexane-containing nitrile rubber contains 50% acrylonitrile.

[0058] Example 1: Multilayer Composite Solid Electrolyte This embodiment discloses a multilayer composite solid electrolyte, the specific composition and preparation of which are as follows: (a) Preparation of the positive electrode side functional layer: Li 10 GeP2S 12 1.0 g (10 wt%) of a fluorinated oxygen co-coordination polymer (n=100, Mn≈6000, 8.0 g, 80 wt%) and PVDF-HFP (1.0 g, 10 wt%) were added to 90 mL of NMP and dispersed at 4000 rpm for 2.5 hours under nitrogen protection to form a homogeneous slurry. The slurry was cast onto a clean PET carrier film with a thickness of 75 μm at a casting speed controlled at 0.8 m / min. Subsequently, it was vacuum dried at 70 °C for 10 hours, and after peeling, a functional layer film with a thickness of approximately 30 μm on the positive electrode side was obtained.

[0059] (b) Preparation of the intermediate support layer: The polymer matrix Pluronic F127 (7.5 g, 75 wt%), lithium sulfonate modified COFs material (grafting amount 1.0 mmol / g, 2.0 g, 20 wt%), and LiTFSI (0.5 g, 5 wt%) were mixed in proportion, and an appropriate amount of anhydrous ethanol was added as a dispersant. The mixture was ball-milled using a planetary ball mill at a speed of 250 r / min for 5 h to ensure thorough and uniform mixing of the components and form a mixed powder. The mixed powder was placed in a mold and hot-pressed at 110 °C and 6 MPa for 45 minutes. After cooling, the powder was removed to obtain an intermediate support layer film with a thickness of approximately 20 μm.

[0060] (c) Preparation of the negative electrode side functional layer: Cyano-modified PEO (cyanoethyl substitution degree 20%) and LiTFSI were weighed at a molar ratio of EO:Li = 15:1, dissolved in anhydrous acetonitrile, and stirred at 75°C until completely dissolved to form a homogeneous solution. This solution was uniformly coated on one side of the intermediate support layer, and the wet film thickness was controlled. The film was then vacuum dried at 55°C for 7 hours to form a negative electrode side bottom film with a thickness of approximately 10 μm.

[0061] (d) Composite solid electrolyte molding: The three layers are stacked in sequence and hot-pressed at 120℃ and 5MPa for 25min to make the three layers tightly bonded, resulting in a sandwich composite solid electrolyte with a total thickness of 60μm.

[0062] Example 2 Multilayer Composite Solid Electrolyte This embodiment discloses another multilayer composite solid electrolyte, which adopts the same implementation method as in Embodiment 1, except that: in this embodiment, the number of repeating units n=50 (Mn≈3000) of the fluorine-oxygen co-coordination polymer in the positive electrode side functional layer is adjusted to 8.5g (85wt%), and the amount of Li is correspondingly increased. 10 GeP2S 12 The dosage was adjusted to 0.5g (5wt%).

[0063] All other process steps and condition parameters are the same as in Example 1.

[0064] Example 3 Multilayer Composite Solid Electrolyte This embodiment discloses another multilayer composite solid electrolyte, which adopts the same implementation method as in Embodiment 1, except that: in this embodiment, in the intermediate support layer, COF-SO3Li material with a lithium sulfonate grafting amount of 0.5 mmol / g is used, with an amount of 2.5g (25wt%), and the amount of Pluronic F127 is adjusted to 7.0g (70wt%) accordingly.

[0065] All other process steps and parameter conditions are the same as in Example 1.

[0066] Example 4 Multilayer Composite Solid Electrolyte This embodiment discloses another multilayer composite solid electrolyte, which adopts the same implementation method as in Embodiment 1, except that: in this embodiment, cyano-modified PEO with a cyanoethyl substitution degree of 35% is used in the functional layer on the negative electrode side.

[0067] All other process steps and parameter conditions are the same as in Example 1.

[0068] Example 5: Multilayer Composite Solid Electrolyte This embodiment discloses another multilayer composite solid electrolyte, which adopts the same implementation method as in Embodiment 1, except that in this embodiment, Li is used in the positive electrode side functional layer. 10 GeP2S 12 Replace with an equal mass of the halide solid electrolyte Li3YCl6.

[0069] All other process steps and parameter conditions are the same as in Example 1.

[0070] Example 6 Multilayer Composite Solid Electrolyte This embodiment discloses another multilayer composite solid electrolyte, which adopts the same implementation method as in Embodiment 1, except that: in the functional layer on the negative electrode side, LiTFSI is replaced with LiPF6, while maintaining the molar ratio of EO:Li = 15:1.

[0071] All other process steps and parameter conditions are the same as in Example 1.

[0072] Comparative Example 1 This comparative example discloses a single PEO solid electrolyte film, which is prepared as follows: PEO (Mn≈600000) and LiTFSI were dissolved in acetonitrile at a ratio of EO:Li=15:1, cast into a film, and dried under vacuum at 50℃ to prepare a single PEO solid electrolyte film with a thickness of about 100μm.

[0073] Comparative Example 2 This comparative example discloses a bilayer composite solid electrolyte, which consists of a positive electrode side functional layer and a negative electrode side functional layer. Specifically, the positive electrode side functional layer in Example 1 is directly hot-pressed together with a gel layer (about 30 μm thick) composed of cyano-modified PEO (20% substitution degree) and LiTFSI (EO:Li=15:1), with a total thickness of about 60 μm.

[0074] Comparative Example 3 This comparative example discloses another multilayer composite solid electrolyte, which adopts the same implementation method as Example 1, except that: COF-SO3Li material is not added to the intermediate support layer, but the content of Pluronic® F127 is increased to 95wt%, while the content of LiTFSI remains at 5wt%. Other process steps and condition parameters are the same as in Example 1.

[0075] Comparative Example 4 This comparative example discloses another multilayer composite solid electrolyte, which adopts the same implementation method as Example 1, except that: no fluorinated oxygen co-coordination polymer is added to the functional layer on the positive electrode side, and its amount is replaced with an equal amount of PVDF-HFP binder (i.e., the total amount of PVDF-HFP is 9.0 g, 90 wt%). 10 GeP2S 12 The dosage remained unchanged (1.0 g, 10 wt%). All other process steps and conditions were the same as in Example 1.

[0076] Comparative Example 5 This comparative example discloses another multilayer composite solid electrolyte, which adopts the same implementation method as Example 1, except that: in the bottom layer on the negative electrode side, cyano-modified polyethylene oxide is replaced with an equal amount of unmodified PEO, and other process steps and condition parameters are the same as in Example 1.

[0077] Example 7 Solid-state battery This embodiment provides a method for fabricating a solid-state battery, the process of which is as follows: In an argon glove box (water and oxygen <0.1ppm), the electrodes were stacked in the order of "positive electrode / multilayer composite electrolyte / negative electrode" and injected with a carbonate electrolyte containing 1wt% AIBN (EC:DMC:EMC=1:1:1 v / v, injection volume 5μL / cm²). The electrodes were then hot-pressed at 80℃ and 5MPa for 2h to assemble them into batteries. The formation process was as follows: constant current charging at 0.1C to 4.2V, then constant voltage charging until the current ≤0.05C.

[0078] The preparation processes for the positive and negative electrodes are as follows: Cathode preparation: LiNi 0.8 Co 0.1 Mn 0.1 O2 (95wt%), PVDF binder (3wt%), and carbon nanotubes (2wt%) were added to an NMP / ethanol mixed solvent (7:3 v / v) and dispersed at 4000 rpm for 2.5 hours under nitrogen protection. The slurry was coated onto aluminum foil at a coating speed of 1.2 m / min, and then dried successively at 90℃ hot air for 1.5 hours and 130℃ vacuum for 5 hours. After rolling, the positive electrode sheet was obtained.

[0079] Anode preparation: SiO x / C (92wt%), polyacrylonitrile binder (5wt%), and graphene (3wt%) were added to NMP solvent and dispersed by ball milling (250 rpm, 3.5 hours). The slurry was coated onto copper foil at a coating speed of 1.0 m / min, and then dried successively at 85℃ hot air for 2.5 hours and 125℃ vacuum for 6 hours. After rolling, the negative electrode sheet was obtained.

[0080] The batteries prepared with solid electrolytes in Examples 1-6 and Comparative Examples 1-5 are referred to as batteries 1-11, respectively.

[0081] Example 8 Solid-state battery This embodiment discloses another solid-state battery fabrication process, referring to Embodiment 7, except that the positive and negative electrodes are different. In this embodiment, the fabrication processes for the positive and negative electrodes are as follows: Cathode preparation: LiNi 0.8 Co 0.1 Mn 0.1 O2 (95wt%), a dual-network binder (organosilicon-modified polyimide: phenylene ring butadiene nitrile rubber = 3:1, total amount 3wt%), and carbon nanotubes (2wt%) were prepared, coated, and dried according to the method of Example 7; 1-vinyl-3-ethylimidazolium salt ionic liquid monomer containing 1M LiTFSI was mixed with 0.5wt% photoinitiator (Irgacure 1173) and coated onto the surface of the above positive electrode. Under a nitrogen atmosphere, the mixture was irradiated with ultraviolet light (wavelength 365 nm, intensity 10 mW / cm²) for 30 seconds to form a polyionic liquid layer with a thickness of about 100 nm through in-situ polymerization.

[0082] Negative electrode preparation: SiO was prepared according to the method in Example 7. x Following the negative electrode sheet (C), a porous polyacrylonitrile-alumina composite layer was deposited on its surface using chemical vapor deposition (CVD). Deposition conditions: temperature 220℃, pressure 2 Pa, time 1.5 hours; composite layer thickness controlled at 200 nm, porosity 70%, and polyacrylonitrile to alumina mass ratio of 3:1.

[0083] The solid electrolyte is the multilayer composite solid electrolyte of Example 1. The resulting battery is designated as Battery 12.

[0084] Example 9 Solid-state battery This embodiment discloses another solid-state battery, referred to as battery 13, which adopts the same battery preparation process as in embodiment 8, except that: no polyionic liquid layer is introduced in the positive electrode.

[0085] Example 10 Solid-state battery This embodiment discloses another solid-state battery, referred to as battery 14, which adopts the same battery preparation process as in embodiment 8, except that: PVDF binder (3wt%) is used instead of double network binder in the preparation of the positive electrode.

[0086] Example 11 Solid-state battery This embodiment discloses another solid-state battery, referred to as battery 15, which adopts the same battery preparation process as in embodiment 8, except that: no polyacrylonitrile-alumina composite layer is deposited on the negative electrode surface.

[0087] Performance testing The batteries 1-15 prepared in the examples and comparative examples were subjected to relevant performance tests under the following conditions: Room temperature ionic conductivity: determined by electrochemical impedance spectroscopy, with a test frequency range of 0.1 Hz to 1 MHz and a test temperature of 25 ℃.

[0088] Tensile strength: The electrolyte membrane was tested at 25℃ using a universal testing machine, in accordance with the national standard GB / T 1040.3.

[0089] Lithium-ion transport number: determined by DC polarization method combined with impedance spectroscopy.

[0090] Electrochemical window: determined by linear scanning voltammetry at a scan rate of 1.0 mV / s and a cutoff current density of 0.1 mA / cm².

[0091] Cycling performance: Charge and discharge tests were conducted at a constant current of 0.5C within a voltage range of 2.8V to 4.3V at 25℃, and the capacity retention rate after 500 cycles was calculated based on the capacity after the 5th cycle.

[0092] Table 1

[0093] As can be seen from the test results in Table 1, the multilayer composite electrolyte prepared in this application exhibits superior overall performance, with high ionic conductivity, high mechanical strength, and high lithium-ion transference number, as well as a wide electrochemical window and excellent cycling performance.

[0094] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A multilayer composite solid electrolyte, characterized in that, It is formed by sequentially stacking a positive electrode side functional layer, an intermediate support layer, and a negative electrode side functional layer, wherein: The positive electrode side functional layer includes an inorganic solid electrolyte and a fluoropolymer. The intermediate support layer comprises a polymer matrix, a porous material with anionic groups modified on its surface, and a lithium salt; The negative electrode side functional layer comprises a polymer with strong coordinating groups and a lithium salt.

2. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The inorganic solid electrolyte is selected from at least one of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes; Preferably, the sulfide solid electrolyte comprises Li 10 GeP2S 12 Li6PS5Cl, Li7P3S 11 At least one of the following: and / or, the halide solid electrolyte includes at least one of Li3YCl6 and Li3YBr6; and / or, the oxide solid electrolyte includes at least one of LLZO and LATP; and / or, the nitride solid electrolyte can be at least one of Li3N and Li3BN2.

3. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The fluoropolymer is a fluorinated oxygen co-coordinated polymer composed of repeating units -AOBO-, with a number-average molecular weight of 3000-10000; wherein A is -(CH2)2-, B is -(CF2)3-, and the number of repeats n is an integer between 30 and 350.

4. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The polymer matrix is ​​a polyether polymer; Preferably, the polyether polymer is selected from at least one of polyethylene oxide, polypropylene oxide, or block copolymers containing the same. More preferably, the polyether polymer is a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. More preferably, the number average molecular weight of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is 5,000-15,000, wherein the mass percentage of the polyethylene oxide segments is 70%-80%.

5. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The porous material is a covalent organic framework material or a metal-organic framework material, and the anionic groups modified on its surface are lithium sulfonate. Preferably, the porous material has a pore size of 1-10 nm and the amount of lithium sulfonate groups grafted onto its surface is 0.2-3.0 mmol / g.

6. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The polymer with strong coordinating groups is a cyano-modified polyether polymer; Preferably, in the cyano-modified polyether polymer, the degree of cyano substitution is 5%-40%.

7. The multilayer composite solid electrolyte as described in claim 1, characterized in that, The thickness of the positive electrode side functional layer is 10-50 μm; the thickness of the intermediate support layer is 10-30 μm; and the thickness of the negative electrode side functional layer is 5-20 μm.

8. A solid-state battery, characterized in that, It comprises a positive electrode, a solid electrolyte, and a negative electrode, characterized in that the solid electrolyte is a multilayer composite solid electrolyte as described in any one of claims 1-7.

9. The solid-state battery as described in claim 8, characterized in that, The positive electrode includes a positive electrode active material, a binder, and a conductive agent. The binder is a dual-network binder, which is composed of organosilicon-modified polyimide and phenylene ring-containing nitrile rubber in a mass ratio of 3:

1. Preferably, the organosilicon-modified polyimide has a number average molecular weight of 5000-1000 and a silicon-oxygen segment ratio of 30-50%; and / or, the acrylonitrile content in the phenylene ring-containing nitrile rubber is 30-80%. Preferably, the surface of the positive electrode further includes a polyionic liquid layer formed by in-situ polymerization, the thickness of which is 50-200 nm.

10. The solid-state battery as described in claim 8, characterized in that, A porous polyacrylonitrile-alumina composite layer is formed on the surface of the negative electrode; Preferably, the composite layer has a thickness of 100-200 nm and a porosity of 50-80%; in the composite layer, the mass ratio of polyacrylonitrile to alumina is (1:1) to (4:1).

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