Solid electrolyte membrane and preparation method and application thereof

Abstract

The invention discloses a solid electrolyte membrane as well as a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The preparation method of the solid electrolyte membrane comprises the following steps: uniformly mixing a two-dimensional ion conductor, a lithium salt, a binder, a film-forming agent and short fibers to obtain a mixture; adding an organic dispersing agent into the mixture, and uniformly mixing to obtain slurry; coating a base material with the slurry, drying and rolling to obtain a solid electrolyte membrane; wherein the two-dimensional ion conductor is a compound of a triazine nitrogen-containing heterocyclic compound and a monocyclic aromatic compound, the triazine nitrogen-containing heterocyclic compound comprises at least one of melamine, 2, 4, 6-tris (trifluoromethyl)-1, 3, 5-triazine, 1, 3, 5-triacryloyl hexahydro-1, 3, 5-triazine and cyanuric chloride, and the monocyclic aromatic compound comprises at least one of triazine, 2, 4, 6-tris (trifluoromethyl)-1, 3, 5-triazine, 1, 3, 5-triacryloyl hexahydro-1, 3, 5-triazine and cyanuric chloride. The monocyclic aromatic compound comprises at least one of mesitylene sulfonic acid, trimesic acid, phloroglucinol and terephthalamide. The obtained solid electrolyte membrane is high in ionic conductivity and good in membrane forming performance.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a solid electrolyte membrane, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in the battery field due to their high energy density, low self-discharge rate, long cycle life, and light weight. Liquid lithium-ion batteries are prone to electrolyte leakage, posing safety hazards. Therefore, all-solid-state lithium-ion battery technology, which uses solid-state electrolytes, is rapidly developing as the most promising next-generation battery technology.

[0003] Currently, solid-state electrolytes are mainly divided into inorganic solid-state electrolytes and polymer solid-state electrolytes. Sulfide and halide solid-state electrolytes, among other inorganic solid-state electrolytes, not only have low ionic conductivity and are unstable in air, potentially releasing toxic and harmful gases, but also face challenges in film formation, high material costs, and instability with high-voltage materials. Oxide solid-state electrolytes have low ionic conductivity, and their rigid structure creates significant impedance at the electrolyte membrane-electrode interface, easily leading to dendrite formation and hindering the development of long-life, high-stability solid-state batteries. Polymer solid-state electrolytes have low ionic conductivity at room temperature and generally suffer from narrow voltage windows and difficulties in continuous film formation. Therefore, both inorganic and polymer solid-state electrolytes currently available suffer from low ionic conductivity and significant challenges in film formation. Summary of the Invention

[0004] The main objective of this invention is to propose a solid electrolyte membrane, its preparation method, and its application, aiming to solve the problems of low ionic conductivity and difficulty in film formation of current solid electrolytes.

[0005] To achieve the above objectives, the present invention provides a method for preparing a solid electrolyte membrane, comprising the following steps:

[0006] Step S10: Mix the two-dimensional ionic conductor, lithium salt, binder, film-forming agent and short fibers to obtain a mixture;

[0007] Step S20: Add an organic dispersant to the mixture and mix well to obtain a slurry;

[0008] Step S30: The slurry is applied to the substrate, dried, and rolled to obtain the solid electrolyte membrane;

[0009] The two-dimensional ionic conductor is a complex of a triazine nitrogen-containing heterocyclic compound and a monocyclic aromatic compound. The triazine nitrogen-containing heterocyclic compound includes at least one of melamine, 2,4,6-tris(trifluoromethyl)-1,3,5-triazine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and cyanuric chloride. The monocyclic aromatic compound includes at least one of mesitylenesulfonic acid, pyromellitic acid, phloroglucinol, and terephthalamide.

[0010] In one embodiment, the mass ratio of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fiber is 40–48:40–48:1.5–8:1.5–8:1–4.

[0011] In one embodiment, the solid content of the slurry is 40%-60%; and / or, the viscosity of the slurry is 2000-10000 mPa·s.

[0012] In one embodiment, step S30 includes:

[0013] The slurry is applied to a substrate and dried in an oven to obtain a dried roll.

[0014] The solid electrolyte membrane is then obtained by rolling with a roller press and subsequently wound up by a winding machine.

[0015] In one embodiment, the coating thickness of the slurry on the substrate is 100–800 μm; and / or, the temperature of the oven is 40–130 °C; and / or, the pressure of the roller mill is 2–25 t; and / or, the winding speed of the winding machine is 0.01–0.20 m / min.

[0016] In one embodiment, the mixing is performed using at least one of a planetary ball mill, a drum mixer, and a grinding mixer.

[0017] In one embodiment, in step S10, the lithium salt includes at least one of lithium chloride, lithium bromide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide; and / or, the binder includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, polyethylene oxide, sodium carboxymethyl cellulose, and alginate; and / or, the film-forming agent includes at least one of polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyetheretherketone, polyacrylonitrile, polymethyl methacrylate, polyvinyl butyral, polydopamine, and polystyrene-acrylate; and / or, the short fiber includes at least one of cellulose short fiber, nylon short fiber, Kevlar short fiber, and alumina short fiber.

[0018] In one embodiment, in step S20, the organic dispersant includes at least one of N-methylpyrrolidone, dimethyl carbonate, diethyl carbonate, and N,N-dimethylformamide; and / or, in step S30, the substrate includes one of aluminum foil, copper foil, acrylic sheet, glass plate, and acid-free paper.

[0019] The present invention also provides a solid electrolyte membrane, which is prepared by the solid electrolyte membrane preparation method described above.

[0020] The present invention also provides a lithium-ion solid-state battery, comprising the solid electrolyte membrane described above.

[0021] The technical solution of this invention involves first uniformly mixing a two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fibers. Then, an organic dispersant is added to the mixture to ensure more uniform dispersion of the different materials, forming a homogeneous and stable slurry. This provides favorable conditions for the wet process preparation of solid electrolyte membranes. In the slurry, the triazine nitrogen-containing heterocyclic compounds and monocyclic aromatic compounds in the two-dimensional ionic conductor alternately arrange to form a stable two-dimensional layered structure. The pores between different layers are composed of Li... + Conductivity provides a transport channel, while the structurally stable two-dimensional ionic conductor can better interact with other materials, thereby improving film-forming performance. The binder connects the materials into a continuous whole, thus improving the mechanical strength of the solid electrolyte membrane. The film-forming agent can regulate the rheology of the slurry, and short fibers combine with different materials through molecular chains to form a reinforcing network, enhancing the toughness of the solid electrolyte membrane and facilitating successful film formation. Next, the slurry is uniformly coated onto the substrate, allowing the solid electrolyte membrane to initially form. Rolling is then used to densify the membrane, while fine-tuning the bonding between different materials to make the structure of each material more compact, ultimately resulting in a solid electrolyte membrane with high ionic conductivity, high mechanical properties, and high toughness. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a schematic flowchart of one embodiment of the method for preparing a solid electrolyte membrane according to the present invention;

[0024] Figure 2 Voltage-specific capacity curves of a solid lithium-ion battery assembled from a solid electrolyte membrane prepared in Example 1 of the present invention during charge and discharge at different rates.

[0025] Figure 3 A photograph of the solid electrolyte membrane prepared in Example 1;

[0026] Figure 4 This is a photograph of the solid electrolyte membrane prepared in Example 3.

[0027] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Furthermore, the use of "and / or" or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies both A and B. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0030] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the reagents and materials used in the following embodiments are commercially available.

[0031] Lithium-ion batteries are widely used in the battery field due to their high energy density, low self-discharge rate, long cycle life, and light weight. Compared to liquid lithium-ion batteries, which are prone to electrolyte leakage, all-solid-state lithium-ion batteries made with solid-state electrolytes have become the most promising next-generation batteries. Currently, solid-state electrolytes are mainly divided into inorganic solid-state electrolytes and polymer solid-state electrolytes. Both existing inorganic solid-state electrolytes and polymer solid-state electrolytes suffer from low ionic conductivity and difficulty in film formation.

[0032] like Figure 1 As shown, this invention proposes a method for preparing a solid electrolyte membrane, comprising the following steps:

[0033] Step S10: Mix the two-dimensional ionic conductor, lithium salt, binder, film-forming agent and short fibers to obtain a mixture;

[0034] Step S20: Add an organic dispersant to the mixture, mix well, and obtain a slurry;

[0035] Step S30: Apply the slurry to the substrate, dry it, and roll it to obtain a solid electrolyte membrane;

[0036] The two-dimensional ionic conductor is a complex of a triazine nitrogen-containing heterocyclic compound and a monocyclic aromatic compound. The triazine nitrogen-containing heterocyclic compound includes at least one of melamine, 2,4,6-tris(trifluoromethyl)-1,3,5-triazine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and cyanuric chloride. The monocyclic aromatic compound includes at least one of tris(toluenesulfonic acid), pyromellitic acid, phloroglucinol, and terephthalamide.

[0037] The technical solution of this invention first involves uniformly mixing a two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fibers to obtain a mixture. Based on the uniform dispersion of different materials in the mixture, an organic dispersant is then added to the mixture to further uniformly disperse the different materials within the organic dispersant, forming a homogeneous and stable slurry. This significantly improves the dispersion uniformity of each material in the solid electrolyte membrane, providing favorable conditions for the wet process preparation of solid electrolyte membranes. Specifically, the two-dimensional ionic conductor in the slurry forms a solid electrolyte with the lithium salt. The two-dimensional ionic conductor is composed of a triazine-based nitrogen-containing heterocyclic compound and a monocyclic aromatic compound. The nitrogen atoms of the triazine-based nitrogen-containing heterocyclic compound are bonded to the carboxyl, hydroxyl, and sulfonic acid groups in the monocyclic aromatic compound through intermolecular hydrogen bonds. Simultaneously, the planar ring structures in the triazine-based nitrogen-containing heterocyclic compound and the monocyclic aromatic compound form π-π stacking, resulting in an alternating arrangement of the triazine-based nitrogen-containing heterocyclic compound and the monocyclic aromatic compound, forming a stable two-dimensional layered structure. The pore size (0.2–1 nm) between different layers is Li + Conductivity provides the transport channel; during ion transport, lithium salt dissociates through interaction with the polar sites of the two-dimensional ion conductor, releasing Li₂. + This makes Li +Rapid transport within the layered channels of the two-dimensional ionic conductor significantly improves the ionic conductivity of the resulting solid electrolyte membrane. The binder bonds the two-dimensional ionic conductor, lithium salt, film-forming agent, and short fibers together through intermolecular forces, connecting the materials into a continuous whole and increasing the interaction forces between different materials, thereby enhancing the mechanical strength of the solid electrolyte membrane. The film-forming agent regulates the rheology of the slurry, enabling it to spread uniformly on the substrate. The short fibers, through molecular chains, combine with different materials to form a reinforcing network, improving the toughness of the solid electrolyte membrane and facilitating successful film formation. In other words, the film-forming agent, short fibers, and two-dimensional ionic conductor synergistically enhance the film-forming stability, mechanical strength, and toughness of the solid electrolyte membrane. The binder, film-forming agent, and short fibers play an auxiliary role in the solid electrolyte, improving the film-forming performance and tensile strength of the electrolyte. Next, the slurry is evenly coated onto the substrate, forming a uniform and stable slurry layer. Drying removes the organic dispersant from the slurry, allowing the solid electrolyte membrane to initially take shape while retaining its layered structure as a two-dimensional ionic conductor. Rolling is then used to densify the membrane, and the bonding between different materials is fine-tuned to make the structure of each material more compact, ultimately yielding a solid electrolyte membrane with high ionic conductivity, high mechanical properties, and high toughness. Based on the high mechanical properties and high toughness of the solid electrolyte membrane, it is successfully separated from the substrate and wound up for later use, enabling mass production and continuous manufacturing of solid electrolyte membranes. The solid electrolyte membrane preparation method of this application is low-cost and technically simple. The resulting solid electrolyte membrane not only has high ionic conductivity but also exhibits good interfacial contact with the solid electrode, reducing interfacial impedance.

[0038] In embodiments of the present invention, the mass ratio of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fiber is 40–48:40–48:1.5–8:1.5–8:1–4. Preferably, the mass ratio of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fiber is 48:48:1.5:1.5:2.

[0039] The technical solution of this invention achieves this by rationally setting the proportions of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fibers, thereby controlling the amount of the two-dimensional ionic conductor and lithium salt to be relatively high, and ensuring that the lithium salt provides sufficient Li... + Meanwhile, the two-dimensional ionic conductor is Li + The transport provides sufficient ion transport channels, facilitating the transport of Li + Rapid conduction; controlling the ratio of the two-dimensional ionic conductor to lithium salt to be close to or 1:1 to achieve Li + Matching with ion transport channels to avoid Li +Problems such as lithium salt agglomeration and low ionic conductivity can occur due to excessive or insufficient binder, or too many or too few ion transport channels. Properly setting the amount of binder ensures uniform and tight bonding of all materials. Insufficient binder weakens the bond strength between materials, affecting the mechanical properties of the solid electrolyte membrane; excessive binder leads to over-adhesion, blocking the ion transport channels formed by the two-dimensional ion conductors and reducing the ionic conductivity of the solid electrolyte membrane. Properly setting the amount of film-forming agent ensures smooth and complete coating of the slurry onto the substrate. Properly setting the amount of short fibers ensures sufficient bonding with different materials, improving the toughness of the solid electrolyte membrane, while avoiding excessive fiber usage that could block the ion transport channels of the two-dimensional ion conductors.

[0040] In embodiments of the present invention, the solid content of the slurry is 40%-60%, preferably 55%; and / or, the viscosity of the slurry is 2000-10000 mPa·s. Specifically, the viscosity of the slurry can be 2000 Pa·s, 3000 Pa·s, 4000 Pa·s, 5000 Pa·s, 6000 Pa·s, 7000 Pa·s, 8000 Pa·s, 9000 Pa·s, 10000 Pa·s, or any range of the above values.

[0041] The technical solution of this invention achieves a certain fluidity by reasonably controlling the solid content and viscosity of the slurry, thereby enabling it to be uniformly coated onto the substrate. If the solid content or viscosity of the slurry is too low, it will be too thin, affecting the density of the resulting solid electrolyte membrane. If the solid content or viscosity of the slurry is too high, it will affect the uniform coating of the slurry onto the substrate, easily leading to material agglomeration, which in turn affects the performance of the solid electrolyte membrane.

[0042] In an embodiment of the present invention, step S30 includes: applying a slurry onto a substrate, drying it in an oven to obtain a dried roll; then rolling it with a roller press to obtain a solid electrolyte membrane, and subsequently winding it up with a winding machine. Figure 1 As shown, in order to achieve continuous production of solid electrolyte membranes, an oven, a roller mill, and a winding machine are arranged sequentially along the forward direction of the solid electrolyte membrane. A conveyor belt is set between the rollers of the oven and the roller mill. The substrate is placed on the conveyor belt. During the production process, a doctor blade continuously coats the substrate with slurry. The conveyor belt is started, and the conveyor belt carries the substrate through the bottom of the oven. The heating components in the oven dry the slurry to obtain a dried roll. The dried roll is further passed between the rollers of the roller mill and pressed by the rollers to obtain a solid electrolyte film. Then, the electrolyte film is wound up by the winding machine to separate it from the substrate.

[0043] The technical solution of this invention forms a film using a wet process. First, a slurry is uniformly coated onto a substrate, which provides a supporting matrix for the slurry, forming a uniform and stable slurry layer on the substrate. Then, the slurry is dried in an oven to remove the organic dispersant, allowing the effective components in the solid electrolyte membrane to initially solidify and form a dried roll. Next, the dried roll is rolled by a roller press to densify the initially formed solidified film, making the structure of each material more compact. At the same time, the bonding state between different materials is finely adjusted to obtain a solid electrolyte membrane with excellent microstructure.

[0044] In embodiments of the present invention, the coating thickness of the slurry on the substrate is 100-800 μm, preferably 400 μm; and / or, the temperature of the oven is 40-130°C, preferably 80°C; and / or, the pressure of the roller mill is 2-25t, preferably 3t; and / or, the winding speed of the winding machine is 0.01-0.20 m / min.

[0045] The technical solution of this invention achieves a suitable thickness for the solid electrolyte membrane by rationally setting the coating thickness of the slurry on the substrate. This ensures uniform coating while avoiding an excessively thin membrane that could affect its mechanical properties, and conversely, an excessively thick membrane that could negatively impact the electrochemical performance of the final assembled solid-state battery. By rationally setting the oven temperature, the organic dispersant is ensured to evaporate sufficiently at an appropriate rate, preventing residue from low temperatures and avoiding excessively high temperatures and rapid evaporation rates that could negatively impact the structure and performance of the solid electrolyte membrane. By rationally setting the pressure of the roller mill, the initially formed cured film is ensured to be sufficiently densified while avoiding damage to the microstructure of the solid electrolyte membrane caused by high pressure. By rationally setting the winding speed of the winding machine, the risk of the solid electrolyte membrane breaking due to excessively fast winding speed is avoided, while excessively slow winding speed can lead to membrane stacking.

[0046] In embodiments of the present invention, the mixing is performed using at least one of a planetary ball mill, a drum mixer, and a grinding mixer.

[0047] In the technical solution of the present invention, the uniform mixing of two-dimensional ionic conductors, lithium salts, binders, film-forming agents and short fibers can be achieved by using different types of mixers, thereby improving the applicability.

[0048] In embodiments of the present invention, in step S10, the lithium salt includes at least one of lithium chloride, lithium bromide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide; and / or, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), polyethylene oxide (PEO), sodium carboxymethyl cellulose (CMC), and alginate, preferably polytetrafluoroethylene; and / or, the film-forming agent includes at least one of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene oxide (PEO), polyetheretherketone (PEEK), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinyl butyral (PVB), polydopamine (PDA), and polystyrene-acrylate; and / or, the short fiber includes at least one of cellulose short fiber, nylon short fiber, Kevlar short fiber, and alumina short fiber, preferably cellulose short fiber.

[0049] The technical solution of this invention, by rationally setting the types of lithium salts and selecting lithium salts with high dissociation degrees, ensures that the lithium salts can fully dissociate after interacting with the two-dimensional ionic conductor, thereby providing sufficient Li... + (The degree of dissociation of different lithium salts in two-dimensional ionic conductors has a certain influence on their ionic conductivity); by rationally setting the type of binder, selecting chemically inert binders with strong interfacial bonding, it is possible to ensure that the binder can connect different materials into a whole while avoiding the binder reacting with lithium salts and two-dimensional ionic conductors and damaging the structure of the solid electrolyte membrane; by rationally setting the type of film-forming agent, the film-forming agent can be better compatible with the binder, improving the mixing uniformity and film-forming properties of the slurry; by rationally setting the type of short fiber, the short fiber can be better bonded to the binder, film-forming agent, and two-dimensional ionic conductor, improving the toughness and mechanical strength of the solid electrolyte membrane.

[0050] In an embodiment of the present invention, in step S20, the organic dispersant includes any one or more combinations of N-methylpyrrolidone (NMP), dimethyl carbonate (DMC), diethyl carbonate (DEC), and N,N-dimethylformamide (DMF), preferably N-methylpyrrolidone; and / or, in step S30, the substrate includes one of aluminum foil, copper foil, acrylic sheet, glass plate, and acid-free paper.

[0051] The technical solution of this invention, by reasonably setting the type of organic dispersant, ensures that the organic dispersant can fully wet different materials so as to achieve uniform dispersion of the materials, while also ensuring that the organic dispersant can be fully removed in the subsequent preparation process; by reasonably setting the type of substrate, the slurry can be uniformly coated, and the formed solid electrolyte membrane can be smoothly separated from it during the winding process.

[0052] The present invention also provides a solid electrolyte membrane, which is prepared by the above-described method for preparing solid electrolyte membranes.

[0053] The technical solution of this invention uses the above-mentioned specific preparation process to prepare a solid electrolyte membrane, and the layered structure of the two-dimensional ion conductor is Li. + The rapid transport in the layered channels of the two-dimensional ion conductor provides the conditions for the high ionic conductivity of the resulting solid electrolyte membrane; at the same time, the film-forming agent, short fibers and two-dimensional ion conductors synergistically enhance the film-forming stability, mechanical strength and toughness of the solid electrolyte membrane.

[0054] The present invention also provides a lithium-ion solid-state battery, comprising the above-described solid electrolyte membrane.

[0055] The technical solution of the present invention is to assemble a solid electrolyte membrane with high ionic conductivity into a lithium-ion solid battery, and there is good interfacial contact between the solid electrolyte membrane and the solid electrode, thereby obtaining a lithium-ion solid battery with high electrochemical performance.

[0056] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the reagents and materials used in the following embodiments are commercially available.

[0057] Example 1

[0058] A method for preparing a solid electrolyte membrane includes the following steps:

[0059] Step S10: The two-dimensional ionic conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers are mixed in a mass ratio of 45:45:4:4:2. The mixture is then stirred and dispersed using a planetary ball mill at 200 rpm for 20 minutes to obtain the final mixture. The two-dimensional ionic conductor is composed of melamine (a triazine-based nitrogen-containing heterocyclic compound) and tris(benzenesulfonic acid) (a monocyclic aromatic compound) in a mass ratio of 1:1.

[0060] Step S20: Place the obtained mixture in a mixing tank, add NMP to the mixture, and mix under vacuum for 2 hours. After mixing, a slurry is obtained. The solid content of the slurry is 40% (i.e., the ratio of the total mass of the two-dimensional ionic conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP and cellulose short fibers to the mass of NMP is 40%), and the viscosity of the slurry is 5000 mPa·s.

[0061] Step S30: Using clean aluminum foil as the substrate, the coating thickness of the slurry is adjusted to 400μm with a scraper, and the slurry is evenly applied to the aluminum foil. The slurry is then applied to the substrate, and the aluminum foil coated with the slurry is transferred to an oven at 80°C to dry for 60 minutes to achieve preliminary curing. Then, a roller press with a roller pressure of 3t is used to roll the solid electrolyte membrane, and the solid electrolyte membrane is wound up. The solid electrolyte membrane is separated from the aluminum foil, and the solid electrolyte membrane is wound up with a winding machine at a winding speed of 0.10m / min.

[0062] like Figure 3 As shown, during the preparation of solid electrolyte membranes, it was found that film formation is easier during the drying and rolling processes.

[0063] The solid electrolyte membrane prepared in Example 1 was assembled into a solid-state lithium-ion battery, and its electrochemical performance was tested. The results are as follows: Figure 2 As shown. Specifically, a lithium iron phosphate positive electrode (2.9cm*3.9cm) and a lithium metal negative electrode (2.9cm*3.9cm) were obtained. The solid electrolyte membrane prepared in Example 1 was cut into a 3cm*4cm rectangle and placed between the positive and negative electrodes to assemble a pouch battery.

[0064] Depend on Figure 2 It can be seen that at a 0.1C rate, the battery's initial charge specific capacity is 147.13 mAh·g. -1 The initial discharge specific capacity was 122.36 mAh·g. -1 The initial Coulomb efficiency was 83.17%; simultaneously from Figure 2 It can be seen that the charge and discharge process at 0.1C rate is more stable than that at 0.2C rate.

[0065] Example 2

[0066] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and cellulose short fibers in step S10 is 40:40:8:8:4. The other steps are largely the same as in Example 1 and will not be repeated here.

[0067] Example 3

[0068] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers in step S10 is 48:48:1.5:1.5:1. The rest is roughly the same as in Example 1 and will not be repeated here.

[0069] Example 4

[0070] A method for preparing a solid electrolyte membrane, which differs from Example 1 only in that the solid content of the slurry in step S20 is 60%, while the rest is roughly the same as in Example 1, and will not be repeated here.

[0071] Example 5

[0072] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the coating thickness of the slurry on the aluminum foil in step S30 is 100 μm. The rest is roughly the same as in Example 1 and will not be repeated here.

[0073] Example 6

[0074] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the coating thickness of the slurry on the aluminum foil in step S30 is 800 μm. The rest is roughly the same as in Example 1 and will not be repeated here.

[0075] Example 7

[0076] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the coating thickness of the slurry on the aluminum foil in step S30 is 1000 μm. The rest is roughly the same as in Example 1 and will not be repeated here.

[0077] Example 8

[0078] A method for preparing a solid electrolyte membrane, which differs from Example 1 only in that the lithium salt in step S10 is lithium bis(trifluoromethanesulfonyl)imide. The rest is roughly the same as in Example 1 and will not be repeated here.

[0079] Comparative Example 1

[0080] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers in step S10 is 0:90:4:4:2, i.e., no two-dimensional ion conductor is added. The rest is roughly the same as in Example 1 and will not be described again here.

[0081] Comparative Example 2

[0082] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers in step S10 is 45:45:8:0:2, i.e., no film-forming agent PVDF-HFP is added. The rest is roughly the same as in Example 1 and will not be described again here.

[0083] Comparative Example 3

[0084] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers in step S10 is 45:45:6:4:0, i.e., no short cellulose fibers are added. The rest is roughly the same as in Example 1 and will not be described again here.

[0085] Comparative Example 4

[0086] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the mass ratio of the two-dimensional ion conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and cellulose short fibers in step S10 is 45:45:10:0:0, meaning that the film-forming agent PVDF-HFP and cellulose short fibers are not added simultaneously. The rest is roughly the same as in Example 1 and will not be repeated here.

[0087] Comparative Example 5

[0088] A method for preparing a solid electrolyte membrane includes the following steps:

[0089] Step S10: The two-dimensional ionic conductor, lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers are mixed in a mass ratio of 45:45:4:4:2. The mixture is then stirred and dispersed using a planetary ball mill at 200 rpm for 20 minutes to obtain the final mixture. The two-dimensional ionic conductor is composed of melamine (a triazine-based nitrogen-containing heterocyclic compound) and tris(benzenesulfonic acid) (a monocyclic aromatic compound) in a mass ratio of 1:1.

[0090] Step S20: Using clean aluminum foil as the substrate, the mixture is evenly spread on the aluminum foil and rolled using a roller press with a roller pressure of 3t to separate the solid electrolyte membrane from the aluminum foil. The solid electrolyte membrane is then wound up using a winding machine with a winding speed of 0.10m / min. This is the dry process used in Comparative Example 5 to prepare the solid electrolyte membrane.

[0091] Comparative Example 6

[0092] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the two-dimensional ion conductor in step S10 is only melamine, a nitrogen-containing heterocyclic triazine compound. The mass ratio of the two-dimensional ion conductor to lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP, and short cellulose fibers is roughly the same as in Example 1, and will not be repeated here.

[0093] Comparative Example 7

[0094] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the two-dimensional ion conductor in step S10 is only the monocyclic aromatic compound tris(benzenesulfonic acid). The mass ratio of the two-dimensional ion conductor to lithium bis(fluorosulfonyl)imide, PTFE, PVDF-HFP and short cellulose fibers is mixed in the same way as in Example 1, and will not be repeated here.

[0095] Comparative Example 8

[0096] A method for preparing a solid electrolyte membrane differs from Example 1 only in that the two-dimensional ion conductor is replaced with polymethyl methacrylate (PMMA) in step S10 to obtain a polymer solid electrolyte. The rest is largely the same as in Example 1 and will not be described again here.

[0097] The solid electrolyte membranes prepared in Examples 1-8 and Comparative Examples 1-8 were cut into circular pieces with a diameter of 16 mm, placed in a 2032 battery case, and the ionic conductivity at room temperature was measured. The results are shown in Tables 1 and 2.

[0098] Film-forming ability: Good > Average > Poor > Very poor.

[0099] Table 1 Performance test results of Examples 1-8 and Comparative Examples 1-5

[0100]

[0101]

[0102] As shown in Table 1, for Examples 1-3, when the mass ratio of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fiber is within the range of 40-48:1.5-8:1.5-8:1-4, the resulting solid electrolyte membrane exhibits relatively high ionic conductivity at room temperature. During the preparation process, it was found that the solid electrolyte membranes of Examples 1-2 were easily formed during drying and rolling, and the resulting membranes had uniform thickness and a smooth surface. The membrane obtained in Example 1 is as follows... Figure 3 As shown; with the reduction of the amount of binder, film-forming agent, and fiber, the resulting solid electrolyte membrane becomes brittle and difficult to peel off from the substrate. The membrane obtained in Example 3 is as follows. Figure 4 As shown in the figure. Meanwhile, data from Comparative Examples 1-4 show that when one or two of the following materials—two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fibers—are missing, the ionic conductivity of the resulting solid electrolyte membrane decreases significantly. Especially when the two-dimensional ionic conductor is absent, the ionic conductivity of the solid electrolyte membrane is only 0.07 mS / cm. This may be because without the addition of the two-dimensional ionic conductor, it is impossible to provide lithium with the desired ionic conductivity. +It provides an effective transport channel, thereby affecting the ionic conductivity of the solid electrolyte membrane. Meanwhile, during the preparation process, it was found that the films formed in Comparative Examples 1-4 were more difficult to form, with a higher defect rate, indicating that the synergistic effect of various substances can not only improve ionic conductivity but also enhance film-forming performance.

[0103] Data from Examples 1 and 4 show that the ionic conductivity of the resulting solid electrolyte membrane changes with the solid content of the slurry. This may be because changes in slurry concentration affect the bonding structure of the materials in the slurry, thereby influencing the microstructure and performance of the resulting solid electrolyte membrane. The solid electrolyte membrane in Example 4 was easily formed during preparation.

[0104] As can be seen from the data of Examples 1 and 5-7, the ionic conductivity of the obtained solid electrolyte membrane decreases with the increase of slurry thickness. When the slurry thickness exceeds 800 μm, the ionic conductivity of the solid electrolyte membrane decreases significantly. This may be because as the slurry thickness increases, the interlayer pores of the two-dimensional ion conductor are blocked, the ion transport path becomes longer, and the transport of lithium ions is reduced accordingly, resulting in a decrease in the ionic conductivity of the obtained solid electrolyte membrane.

[0105] As can be seen from the data in Example 8, when the type of lithium salt is changed, the ionic conductivity of the resulting solid electrolyte membrane at room temperature is still relatively high, indicating the universality of different types of lithium salts.

[0106] As can be seen from the data in Comparative Example 5, the ionic conductivity of the solid electrolyte membrane prepared by the dry process is only 0.6, which is significantly low. This may be because the dry process lacks the dispersion effect of solvents, and the distribution of binders, film-forming agents, etc. is poor, resulting in poor structure and performance of the obtained solid electrolyte membrane.

[0107] Table 2 Performance test results of Comparative Examples 6-8

[0108]

[0109] As shown in Table 2, for Comparative Examples 6 and 7, when the two-dimensional ionic conductor is only one of a triazine-based nitrogen-containing heterocyclic compound or a monocyclic aromatic compound, the conductivity of the resulting polymer solid electrolyte film decreases sharply. This further illustrates that the synergistic effect of the triazine-based nitrogen-containing heterocyclic compound and the monocyclic aromatic compound provides sufficient transport channels for Li+ conduction. Meanwhile, it was found that the film formation difficulty in Comparative Examples 6 and 7 was increased compared to Example 1, indicating that the two-dimensional ionic conductor formed by the triazine-based nitrogen-containing heterocyclic compound and the monocyclic aromatic compound plays a crucial role in electrolyte film formation.

[0110] As can be seen from the data in Comparative Example 8, when the two-dimensional ionic conductor is replaced with a polymer, the ionic conductivity of the resulting polymer solid electrolyte is only 0.001, which is significantly low. This further illustrates that the two-dimensional ionic conductor used in this application can significantly improve the ionic conductivity of the solid electrolyte membrane.

[0111] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing a solid electrolyte membrane, characterized in that, Includes the following steps: Step S10: Mix the two-dimensional ionic conductor, lithium salt, binder, film-forming agent and short fibers to obtain a mixture; Step S20: Add an organic dispersant to the mixture and mix well to obtain a slurry; Step S30: The slurry is applied to the substrate, dried, and rolled to obtain the solid electrolyte membrane; The two-dimensional ionic conductor is a complex of a triazine nitrogen-containing heterocyclic compound and a monocyclic aromatic compound. The triazine nitrogen-containing heterocyclic compound includes at least one of melamine, 2,4,6-tris(trifluoromethyl)-1,3,5-triazine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and cyanuric chloride. The monocyclic aromatic compound includes at least one of mesitylenesulfonic acid, pyromellitic acid, phloroglucinol, and terephthalamide.

2. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, In step S10, the mass ratio of the two-dimensional ionic conductor, lithium salt, binder, film-forming agent, and short fiber is 40-48:40-48:1.5-8:1.5-8:1-4.

3. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, In step S20, the solid content of the slurry is 40%-60%; and / or, The viscosity of the slurry is 2000–10000 mPa·s.

4. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, Step S30 includes: The slurry is applied to a substrate and dried in an oven to obtain a dried roll. The solid electrolyte membrane is then obtained by rolling with a roller press and subsequently wound up by a winding machine.

5. The method for preparing a solid electrolyte membrane as described in claim 4, characterized in that, The slurry is coated on the substrate to a thickness of 100–800 μm; and / or, The temperature of the oven is 40–130°C; and / or, The pressure of the roller mill is 2–25 t; and / or, The winding speed of the winding machine is 0.01 to 0.20 m / min.

6. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, In step S10, the mixing is performed using at least one of a planetary ball mill, a drum mixer, and a grinding mixer.

7. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, In step S10, the lithium salt includes at least one of lithium chloride, lithium bromide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide; and / or, The adhesive comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, styrene-butadiene rubber, polyethylene oxide, sodium carboxymethyl cellulose, and alginate; and / or, The film-forming agent includes at least one of polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, polyetheretherketone, polyacrylonitrile, polymethyl methacrylate, polyvinyl butyral, polydopamine, and polystyrene-acrylate; and / or, The short fibers include at least one of cellulose short fibers, nylon short fibers, Kevlar short fibers, and alumina short fibers.

8. The method for preparing a solid electrolyte membrane as described in claim 1, characterized in that, In step S20, the organic dispersant includes at least one selected from N-methylpyrrolidone, dimethyl carbonate, diethyl carbonate, and N,N-dimethylformamide; and / or, In step S30, the substrate includes one of aluminum foil, copper foil, acrylic sheet, glass sheet, and acid-free paper.

9. A solid electrolyte membrane, characterized in that, It is prepared by the method of any one of claims 1 to 8.

10. A lithium-ion solid-state battery, characterized in that, This includes solid electrolyte membranes prepared by the method for preparing solid electrolyte membranes according to any one of claims 1 to 8, or solid electrolyte membranes according to claim 9.

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