Modified all-solid-state battery cell and preparation method therefor, modified all-solid-state battery

Abstract

The application relates to a modified full-solid-state battery cell and a preparation method thereof, and a modified full-solid-state battery. The modified full-solid-state battery cell comprises a negative electrode sheet, a solid-state electrolyte layer, a cross-linked interface layer and a positive electrode sheet which are sequentially stacked; the raw material of the cross-linked interface layer comprises a silane coupling agent, and the structural formula of the silane coupling agent comprises an alkenyl functional group and a fluorine-based functional group. The application introduces the cross-linked interface layer on the surface of the solid-state electrolyte layer, and limits the structural formula of the raw material silane coupling agent of the cross-linked interface layer to comprise the alkenyl functional group and the fluorine-based functional group, so that the alkenyl functional group and the fluorine-based functional group are matched, the interface compatibility of the solid-state electrolyte layer and the positive electrode active material layer of the full-solid-state battery cell is overall optimized, and the structural stability and the electrochemical performance of the full-solid-state battery cell are improved.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, and in particular to a modified all-solid-state battery cell and its preparation method, as well as a modified all-solid-state battery. Background Technology

[0002] In existing conventional all-solid-state battery cell structures, no interface modification layer, buffer coating layer, or transition modification layer is set between the solid electrolyte and the positive electrode active layer. The two rely solely on cold pressing to achieve simple direct physical bonding contact, without any chemical bonding. Taking sulfide solid electrolyte as an example, when the all-solid-state battery cell completes charge-discharge cycles in the high-voltage range, the sulfide solid electrolyte itself has a narrow electrochemical stability window. Under the high oxidation potential environment on the positive electrode side, it is prone to irreversible oxidation decomposition reaction, continuously consuming lithium ions and generating high-resistivity impurity phase products, directly causing rapid capacity decay of the battery cell. At the same time, the solid electrolyte layer and the positive electrode active material layer are only physically bonded by pressure. The thermal expansion coefficient and mechanical deformation characteristics of the two are significantly different. Under the repeated charge-discharge lithium insertion and extraction volume stress cycle, the interface is prone to problems such as delamination, local void debonding, and large-area contact failure. The effective contact area between the two phases continues to shrink, and the interfacial charge transfer impedance continues to rise and shows an irreversible growth trend. The aforementioned two types of problems, interface oxidation degradation and interface contact failure, synergistically worsen the electrochemical performance of the cell, significantly limiting the structural stability and electrochemical performance of all-solid-state cells.

[0003] Furthermore, the conventional process for transferring the solid electrolyte layer to the negative electrode layer in all-solid-state battery electrode fabrication involves an unmodified substrate transfer process. This process uses pure PET, PI, or other polymer films as the substrate for the solid electrolyte layer. After directly coating the solid electrolyte slurry to form a film, it is then cold-pressed onto the negative electrode to transfer the electrolyte to the negative electrode. However, due to the strong polarity and high surface energy of conventional PET, PI, and other substrates, the solid electrolyte layer has a strong bond with the substrate, resulting in excessive interfacial adhesion. This makes it difficult to peel the solid electrolyte layer from the substrate, and the peeling process is prone to breakage and damage, thus preventing complete transfer and failing to meet the continuity requirements of the solid electrolyte in all-solid-state batteries.

[0004] Therefore, how to provide a modified all-solid-state battery cell and its preparation method, optimize the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state battery cell, and improve the structural stability and electrochemical performance of the all-solid-state battery cell are technical problems that urgently need to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a modified all-solid-state battery cell, its preparation method, and a modified all-solid-state battery. This invention introduces a cross-linked interface layer onto the surface of the solid electrolyte layer, and specifies that the structure of the silane coupling agent used as the raw material for the cross-linked interface layer includes alkenyl and fluorine functional groups. By utilizing the combination of alkenyl and fluorine functional groups, the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state battery cell is optimized, thereby improving the structural stability and electrochemical performance of the all-solid-state battery cell.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a modified all-solid-state battery cell, the modified all-solid-state battery cell comprising a negative electrode sheet, a solid electrolyte layer, a cross-linking interface layer and a positive electrode sheet stacked sequentially; The raw materials used in the cross-linked interface layer include silane coupling agents, and the structural formula of the silane coupling agents includes alkenyl functional groups and fluorine functional groups.

[0007] This invention introduces a cross-linked interface layer on the surface of the solid electrolyte layer, and defines the structure of the silane coupling agent used in the cross-linked interface layer to include alkenyl and fluorine functional groups. The cross-linked interface layer is placed between the solid electrolyte layer and the positive electrode active material layer. The fluorine functional group can form a lithium fluoride (LiF) interface film under high voltage, effectively suppressing the interfacial side reactions caused by the oxidation of the solid electrolyte layer on the positive electrode side, reducing interfacial impedance, and improving the high voltage resistance and cycle stability of the cell. The carbon-carbon double bonds of the alkenyl functional group trigger an addition reaction after high temperature, forming a covalent bond network with both the surface of the positive electrode active material layer and the surface of the solid electrolyte layer, strengthening the interfacial bonding force, and preventing interfacial delamination during cycling. At the same time, the fluorine functional group remains chemically inert after high temperature and remains stably present at the interface between the solid electrolyte layer and the positive electrode active material layer. This optimizes the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state cell, and improves the structural stability and electrochemical performance of the all-solid-state cell.

[0008] As a preferred technical solution of the present invention, the silane coupling agent includes a bifunctional coupling agent containing alkenyl and fluorine groups or a mixture of alkenyl silane coupling agent and fluorine silane coupling agent.

[0009] As a preferred embodiment of the present invention, the bifunctional coupling agent containing alkenyl and fluorine groups includes at least one of vinyltrifluoropropyldimethoxysilane, allyltrifluoropropyldiethoxysilane, methacryloyloxypropyltrifluoropropyldimethoxysilane, 1H,1H,2H,2H-perfluorooctylvinyldimethoxysilane, perfluorodecylallyldiethoxysilane, or p-trifluoromethylstyryltrimethoxysilane.

[0010] As a preferred embodiment of the present invention, the alkenyl silane coupling agent-fluorosilane coupling agent mixture includes at least one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, allyltrimethoxysilane, undecenyltrimethoxysilane, or 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane.

[0011] Preferably, in the alkenylsilane coupling agent-fluorosilane coupling agent mixture, the fluorosilane coupling agent includes at least one of 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, or heptadecafluorodecyltriethoxysilane.

[0012] Preferably, the mass ratio of the alkenylsilane coupling agent to the fluorosilane coupling agent is (1-2):1, for example, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc.

[0013] This invention utilizes fluorosilane coupling agents to construct a low surface energy release layer, generate an in-situ LiF passivation film at the cathode interface, and suppress high-pressure oxidation side reactions. Alkenylsilane coupling agents provide carbon-carbon double bond active sites, which undergo addition cross-linking at the interface between the solid electrolyte layer and the cathode active material layer after hot pressing, strengthening the interfacial mechanical bonding. By controlling the mass ratio of alkenylsilane coupling agent to fluorosilane coupling agent to (1-2):1, sufficient double bond sites are ensured, avoiding the influence of inert fluoroalkyl groups encapsulating the double bonds on cross-linking. Simultaneously, a thin LiF passivation layer is formed to stabilize the interface, preventing impedance spikes due to excessive fluorine, thus achieving both mechanical bonding and electrochemical stability. If the mass ratio is too low, the interfacial cross-linking effect will be weakened, resulting in poor interfacial contact and increased ion transport resistance; if the mass ratio is too high, insufficient fluorine functional groups at the interface will lead to more interfacial side reactions, making it difficult to form a complete LiF passivation film under high pressure and exacerbating electrolyte oxidation side reactions. Both of these will result in low first-cycle coulombic efficiency and capacity retention of the battery.

[0014] As a preferred embodiment of the present invention, the solid electrolyte layer comprises a sulfide solid electrolyte layer.

[0015] It should be noted that the present invention does not impose specific requirements or limitations on the specific sulfide solid electrolyte material of the sulfide solid electrolyte layer; all such materials are suitable for the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0016] Preferably, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector.

[0017] It should be noted that the present invention does not impose specific requirements or special limitations on the composition and content of the negative electrode active material layer. The composition and content of the negative electrode active material layer commonly used in the field for all-solid-state batteries are all suitable for the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0018] Preferably, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector.

[0019] It should be noted that the present invention does not impose specific requirements or special limitations on the composition and content of the positive electrode active material layer. The composition and content of the positive electrode active material layer commonly used in the field for all-solid-state batteries are all suitable for the present invention. Those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0020] As a preferred technical solution of the present invention, the thickness of the cross-linked interface layer is 0.5μm-5μm, such as 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm.

[0021] This invention regulates the thickness of the crosslinked interface layer to 0.5μm-5μm, ensuring the formation of a continuous and complete bonded hydrophobic release layer on the substrate surface while precisely controlling the amount of free silane precipitation. If the crosslinked interface layer is too thin, there will be too little free silane, resulting in no interface modification effect; if the crosslinked interface layer is too thick, there will be too much free silane, leading to high interface impedance. Both of these will result in low first-cycle coulombic efficiency and capacity retention of the battery.

[0022] In a second aspect, the present invention also provides a method for preparing a modified all-solid-state battery cell according to the first aspect, the method comprising the following steps: (1) Mix the silane coupling agent and the hydrolysis medium solution evenly to obtain the modified coupling agent coating solution; The silane coupling agent includes an alkenyl functional group and a fluoro functional group in its structural formula. (2) The modified coupling agent coating liquid is coated on the surface of the substrate to form a modified film layer on the surface of the substrate; (3) A solid electrolyte layer is prepared on the surface of the modified film layer, and then the negative electrode active material layer and the solid electrolyte layer in the negative electrode sheet are pressed into shape, and the substrate is peeled off; (4) The positive electrode active material layer in the positive electrode sheet and the modified film layer are bonded together and hot-pressed to obtain a modified all-solid-state battery cell.

[0023] This invention introduces a cross-linked interface layer on the surface of the solid electrolyte layer, and limits the raw material of the cross-linked interface layer, silane coupling agent, to include bifunctional coupling agents containing alkenyl and fluorine groups. It also achieves non-destructive peeling between the solid electrolyte layer and the substrate during the preparation process. Both alkenyl and fluorine functional groups have strong hydrophobicity and low surface energy characteristics, which will synergistically weaken the interfacial adhesion between the solid electrolyte layer and the substrate. After pressing and molding, the substrate will automatically peel off without damage to the solid electrolyte layer, achieving complete transfer and meeting the continuity requirements of solid electrolyte in all-solid-state batteries.

[0024] Hot pressing can trigger the carbon-carbon double bond addition reaction of alkenyl functional groups, forming a covalent bond network with both the surface of the positive electrode active material layer and the surface of the solid electrolyte layer, strengthening the interfacial bonding force and preventing interfacial delamination during cycling.

[0025] As a preferred technical solution of the present invention, the hydrolysis medium solution in step (1) includes anhydrous ethanol-deionized water mixed solvent.

[0026] Preferably, in the anhydrous ethanol-deionized water mixed solvent, the volume ratio of anhydrous ethanol to deionized water is x:y, where x+y=100, 90≤x≤95, for example 90, 91, 92, 93, 94 or 95, etc.

[0027] Preferably, the mass concentration of the modified coupling agent coating solution in step (1) is 0.5wt%-6wt%, for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt%.

[0028] This invention regulates the mass concentration of the modified coupling agent coating solution to 0.5wt%-6wt%, achieving the formation of a continuous and complete bonded hydrophobic release layer on the substrate surface while precisely controlling the amount of free silane precipitation. This ensures effective release while limiting the total amount of fluorosilane and alkenylsilane transferred to the cathode interface along with the solid electrolyte layer, thus balancing release performance, LiF passivation protection at the cathode interface, and alkenyl crosslinking effect. It avoids the dual defects of insufficient free silane leading to no interface modification and excessive free silane causing high interfacial impedance. If the mass concentration of the modified coupling agent coating solution is too low, the substrate release effect is poor, and the cathode interface modification components are insufficient, failing to achieve both non-destructive transfer and interface stability. If the mass concentration of the modified coupling agent coating solution is too high, it will cause excessive free silane at the cathode interface, leading to increased interfacial impedance, decreased crosslinking efficiency, and increased side reactions.

[0029] Preferably, the mixing method in step (1) includes stirring and dissolving.

[0030] Preferably, the mixing time in step (1) is 30 min to 60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0031] Preferably, after mixing in step (1), the mixture is further subjected to static degassing.

[0032] Preferably, after the coating process in step (2) is completed, the process further includes curing and molding.

[0033] Preferably, the curing temperature is 50℃-90℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, 72℃, 75℃, 78℃, 80℃, 82℃, 85℃, 88℃ or 90℃.

[0034] Preferably, the curing time is 1-3 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0035] Preferably, the curing process is carried out under vacuum conditions.

[0036] Preferably, the substrate in step (2) includes a PET flexible polymer film and / or a PI flexible polymer film.

[0037] As a preferred technical solution of the present invention, the pressing pressure in step (3) is 100MPa-400MPa, such as 100MPa, 150MPa, 200MPa, 250MPa, 300MPa, 350MPa or 400MPa.

[0038] Preferably, the pressing time in step (3) is 5 min to 15 min, such as 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min or 15 min.

[0039] The pressing and molding process described in step (3) of this invention is carried out at room temperature (25℃±5℃).

[0040] Preferably, the heat preservation temperature of the hot pressing treatment in step (4) is 120℃-160℃, such as 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃ or 160℃.

[0041] Preferably, the pressure of the hot pressing process in step (4) is 20MPa-200MPa, such as 20MPa, 50MPa, 80MPa, 100MPa, 120MPa, 150MPa, 180MPa or 200MPa.

[0042] Preferably, the heat preservation and pressure holding time of the hot pressing treatment in step (4) is 0.3h-1h, for example 0.3h, 0.5h, 0.8h or 1h.

[0043] Preferably, after the hot pressing process described in step (4) is completed, the pressure is released and the temperature is allowed to drop naturally to room temperature.

[0044] The natural cooling process to room temperature in this invention can promote stable interface formation.

[0045] Thirdly, the present invention also provides a modified all-solid-state battery, the modified all-solid-state battery comprising the modified all-solid-state cell as described in the first aspect, or the modified all-solid-state cell prepared by the preparation method described in the second aspect.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects: This invention introduces a cross-linked interface layer on the surface of the solid electrolyte layer, and defines the structure of the silane coupling agent used in the cross-linked interface layer to include alkenyl and fluorine functional groups. The cross-linked interface layer is positioned between the solid electrolyte layer and the positive electrode active material layer. The fluorine functional group can form a lithium fluoride interface film under high voltage, effectively suppressing the interfacial side reactions caused by the oxidation of the solid electrolyte layer on the positive electrode side, reducing interfacial impedance, and improving the high voltage resistance and cycle stability of the cell. The carbon-carbon double bonds of the alkenyl functional group trigger an addition reaction after high temperature, forming a covalent bond network with both the surface of the positive electrode active material layer and the surface of the solid electrolyte layer, strengthening the interfacial bonding force and preventing interfacial delamination during cycling. At the same time, the fluorine functional group remains chemically inert after high temperature and remains stably present at the interface between the solid electrolyte layer and the positive electrode active material layer. This optimizes the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state cell, improving the structural stability and electrochemical performance of the all-solid-state cell. Attached Figure Description

[0047] Figure 1 This is a modified all-solid-state battery cell structure and its fabrication process provided in Embodiment 1 of the present invention.

[0048] Among them, 1-PI flexible polymer film; 2-modified film layer; 3-Li6PS5Cl solid electrolyte layer; 4-copper foil; 5-negative electrode active material layer; 6-aluminum foil; 7-positive electrode active material layer; 8-crosslinking interface layer. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0050] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0051] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0052] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0053] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0054] Example 1 This embodiment provides a modified all-solid-state battery cell. Figure 1The modified all-solid-state battery cell structure and its preparation flowchart provided in Embodiment 1 of the present invention are shown. The modified all-solid-state battery cell includes a graphite negative electrode sheet (copper foil 4 and a negative electrode active material layer 5 located on one side of the copper foil 4, which consists of 85wt% graphite, 1wt% conductive carbon black, 10wt% Li6PS5Cl and 4wt% styrene-butadiene rubber SBR), a Li6PS5Cl solid electrolyte layer 3, a crosslinking interface layer 8, and an NCM811 positive electrode sheet (aluminum foil 6 and a positive electrode active material layer 7 located on one side of the aluminum foil 6, which consists of 80wt% NCM811, 2wt% conductive carbon black, 16wt% Li6PS5Cl and 2wt% polyisobutylene PIB). The raw material silane coupling agent used in the crosslinking interface layer 8 is vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane, and the thickness of the crosslinking interface layer 8 is 3 μm.

[0055] The preparation method of modified all-solid-state battery cells includes the following steps: (1) Mix vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane at a mass ratio of 1:1, add anhydrous ethanol-deionized water mixed solution (volume ratio of 95:5), stir for 45 min until the mixture is completely dissolved, and let stand to remove bubbles to obtain a modified coupling agent coating solution with a mass concentration of 5wt%. (2) The modified coupling agent coating liquid is scraped onto the surface of the PI flexible polymer film 1, and dried in a vacuum environment at 80°C for 2 hours to solidify and form a modified film layer 2 on the surface of the PI flexible polymer film 1. (3) A solid electrolyte slurry with a solid content of 50% Li6PS5Cl was coated on the surface of the modified film layer 2. After coating, it was placed in a vacuum drying oven at 100℃ and dried for 3 hours to completely remove the organic solvent p-xylene. A solid electrolyte layer 3 Li6PS5Cl was formed on the surface of the modified film layer 2. The negative electrode active material layer 5 in the negative electrode sheet and the solid electrolyte layer 3 Li6PS5Cl were attached together and placed in a cold press. The press was pressed for 8 minutes under a pressure of 300MPa. The PI flexible polymer film substrate 1 was peeled off (automatic peeling after cold pressing). (4) The positive electrode active material layer 7 and the modified film layer 2 in the positive electrode sheet are completely bonded together to obtain the battery cell to be treated. The cell is placed in a hot press and heated to 150°C under a pressure of 80MPa. The temperature is maintained for 1 hour, the pressure is removed, and the cell is allowed to cool down naturally to room temperature to obtain the modified all-solid-state battery cell.

[0056] Example 2 This embodiment provides a modified all-solid-state battery cell, which includes a graphite negative electrode sheet (copper foil and a negative electrode active material layer located on one side of the copper foil, consisting of 85wt% graphite, 1wt% conductive carbon black, 10wt% Li6PS5Cl and 4wt% SBR), a Li6PS5Cl solid electrolyte layer, a cross-linking interface layer, and an NCM811 positive electrode sheet (aluminum foil and a positive electrode active material layer located on one side of the aluminum foil, consisting of 80wt% NCM811, 2wt% conductive carbon black, 16wt% Li6PS5Cl and 2wt% PIB). The raw material silane coupling agent used in the crosslinking interface layer is allyltrifluoropropyldiethoxysilane, and the thickness of the crosslinking interface layer is 1 μm.

[0057] The preparation method of modified all-solid-state battery cells includes the following steps: (1) Add allyltrifluoropropyldiethoxysilane to anhydrous ethanol-deionized water mixed solution (volume ratio of 90:10) and stir for 45 min until it is completely dissolved. After standing to remove bubbles, a modified coupling agent coating solution with a mass concentration of 1wt% is obtained. (2) The modified coupling agent coating liquid is scraped onto the surface of the PI flexible polymer film, dried in a vacuum environment at 80°C for 2 hours, and cured to form a modified film layer on the surface of the PI flexible polymer film. (3) A solid electrolyte slurry with a solid content of 55% Li6PS5Cl was coated on the surface of the modified film. After coating, it was placed in a vacuum drying oven at 100℃ and dried for 3 hours to completely remove the organic solvent toluene. A solid electrolyte layer of Li6PS5Cl was formed on the surface of the modified film. The negative electrode active material layer and the solid electrolyte layer of Li6PS5Cl in the negative electrode sheet were attached together and placed in a cold press. The press was pressed for 10 minutes under a pressure of 200MPa. The PI flexible polymer film substrate was peeled off (automatic peeling after cold pressing). (4) The positive electrode active material layer and the modified film layer in the positive electrode sheet are completely bonded together to obtain the cell to be treated. The cell is placed in a hot press and heated to 140°C under a pressure of 100MPa. The temperature is maintained for 0.5h, the pressure is removed, and the cell is allowed to cool naturally to room temperature to obtain the modified all-solid-state cell.

[0058] Example 3 This embodiment provides a modified all-solid-state battery cell, which includes a graphite negative electrode sheet (copper foil and a negative electrode active material layer located on one side of the copper foil, consisting of 85wt% graphite, 1wt% conductive carbon black, 10wt% Li6PS5Cl and 4wt% SBR), a Li6PS5Cl solid electrolyte layer, a cross-linking interface layer, and an NCM811 positive electrode sheet (aluminum foil and a positive electrode active material layer located on one side of the aluminum foil, consisting of 80wt% NCM811, 2wt% conductive carbon black, 16wt% Li6PS5Cl and 2wt% PIB). The raw material silane coupling agents used in the crosslinking interface layer are 3-acryloyloxypropyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and the thickness of the crosslinking interface layer is 5 μm.

[0059] The preparation method of modified all-solid-state battery cells includes the following steps: (1) 3-Acryloyloxypropyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltrimethoxysilane were mixed at a mass ratio of 2:1, and anhydrous ethanol-deionized water mixed solution (volume ratio of 92:8) was added and stirred for 45 min until the mixture was completely dissolved. After standing to remove bubbles, a modified coupling agent coating solution with a mass concentration of 6wt% was obtained. (2) The modified coupling agent coating liquid is applied to the surface of the PET flexible polymer film, dried in a vacuum environment at 80°C for 2 hours, and cured to form a modified film layer on the surface of the PET flexible polymer film. (3) A solid electrolyte slurry with a solid content of 60% Li6PS5Cl was coated on the surface of the modified film. After coating, it was placed in a vacuum drying oven at 100℃ and dried for 3 hours to completely remove the organic solvent anisole. A solid electrolyte layer of Li6PS5Cl was formed on the surface of the modified film. The negative electrode active material layer and the solid electrolyte layer of Li6PS5Cl in the negative electrode sheet were attached together and placed in a cold press. The press was pressed for 5 minutes under a pressure of 400MPa. The PET flexible polymer film substrate was peeled off (automatic peeling after cold pressing). (4) The positive electrode active material layer and the modified film layer in the positive electrode sheet are completely bonded together to obtain the cell to be treated. The cell is placed in a hot press and heated to 150°C under a pressure of 60MPa. The temperature is maintained for 0.7h, the pressure is removed, and the cell is allowed to cool naturally to room temperature to obtain the modified all-solid-state cell.

[0060] Example 4 This embodiment provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and that of Example 1 is that vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane are mixed at a mass ratio of 0.5:1, while the remaining preparation methods and parameters are the same as those of Example 1.

[0061] Example 5 This embodiment provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and that of Example 1 is that vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane are mixed at a mass ratio of 2.5:1, while the remaining preparation methods and parameters are the same as those of Example 1.

[0062] Example 6 This embodiment provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and that in Example 1 is that the mass concentration of the modified coupling agent coating solution in step (1) is 6.5 wt%, while the rest of the preparation methods and parameters are the same as in Example 1.

[0063] Example 7 This embodiment provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and that in Example 1 is that the coating thickness of the modified coupling agent coating liquid is adjusted so that the thickness of the cross-linked interface layer in the modified all-solid-state battery cell is 5.5 μm. The rest of the preparation method and parameters are the same as in Example 1.

[0064] Comparative Example 1 This comparative example provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and Example 1 is that vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane are replaced with equal masses of vinyltriethoxysilane, and 3,3,3-trifluoropropyltrimethoxysilane is omitted. The rest of the preparation method and parameters are the same as in Example 1.

[0065] Comparative Example 2 This comparative example provides a modified all-solid-state battery cell and its preparation method. The difference between the preparation method and Example 1 is that vinyltriethoxysilane and 3,3,3-trifluoropropyltrimethoxysilane are replaced with an equal mass of 3,3,3-trifluoropropyltrimethoxysilane, and vinyltriethoxysilane is omitted. The remaining preparation methods and parameters are consistent with those of Example 1.

[0066] Comparative Example 3 This comparative example provides an all-solid-state battery cell and its preparation method. The difference between the preparation method and Example 1 is that a Li6PS5Cl solid electrolyte slurry with a solid content of 50% is directly coated onto the surface of a PI flexible polymer film. After coating, it is placed in a vacuum drying oven at 100°C and dried for 3 hours to completely remove the organic solvent p-xylene. A Li6PS5Cl solid electrolyte layer is formed on the surface of the PI flexible polymer film. The PI flexible polymer film and the Li6PS5Cl solid electrolyte layer are peeled off by manual bending. The remaining preparation methods and parameters are consistent with those of Example 1.

[0067] Application Example 1-7 and Comparative Application Example 1-3 The modified all-solid-state cells prepared in Examples 1-7 and Comparative Examples 1-2 were assembled into pouch modified all-solid-state batteries, and the all-solid-state cells prepared in Comparative Example 3 were assembled into pouch all-solid-state batteries, corresponding to Application Examples 1-7 and Comparative Application Examples 1-3, respectively.

[0068] The batteries provided in Application Examples 1-7 and Comparative Application Examples 1-3 were tested at 45°C and 10MPa, with a voltage range of 2V-4.2V. The coulombic efficiency for the first cycle was tested at 0.1C, and the capacity retention rate for 100 cycles was tested at 0.5C. The specific test results are shown in Table 1.

[0069] Table 1 The test results show that: (1) As can be seen from Application Examples 1-3, this invention introduces a cross-linked interface layer on the surface of the solid electrolyte layer and limits the structural formula of the raw material silane coupling agent of the cross-linked interface layer to include alkenyl and fluorine functional groups. By combining alkenyl and fluorine functional groups, the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state battery cell is optimized, thereby improving the structural stability and electrochemical performance of the all-solid-state battery cell. Specifically, the first-cycle coulombic efficiency of the pouch-modified all-solid-state battery can reach 90%-92%, and the capacity retention rate after 100 cycles can reach 97%-98%.

[0070] (2) As can be seen from Application Example 1 and Application Examples 4-5, the present invention regulates the mass ratio of alkenyl silane coupling agent and fluorosilane coupling agent to (1-2):1, ensuring sufficient double bond sites and avoiding the influence of inert fluoroalkyl groups on the crosslinking of double bonds; at the same time, a thin LiF passivation layer is formed to stabilize the interface, and the impedance will not spike due to excessive fluorine, thus achieving a dual synergy of mechanical bonding and electrochemical stability.

[0071] (3) As can be seen from Application Example 1 and Application Example 6, the present invention controls the mass concentration of the modified coupling agent coating liquid to 0.5wt%-6wt%, thereby achieving the formation of a continuous and complete bonded hydrophobic release layer on the substrate surface, while precisely controlling the amount of free silane precipitation; it ensures the release effect and limits the total amount of fluorosilane and alkenylsilane that are transferred to the positive electrode interface along with the solid electrolyte layer, thus taking into account the release performance, the LiF passivation protection of the positive electrode interface and the alkenyl crosslinking effect, and avoiding the dual defects of insufficient free silane resulting in no interface modification and excessive free silane causing high interface impedance.

[0072] (4) As can be seen from Application Example 1 and Application Example 7, the present invention controls the thickness of the cross-linked interface layer to 0.5μm-5μm, which can ensure the formation of a continuous and complete bonded hydrophobic release layer on the substrate surface, while precisely controlling the amount of free silane precipitation.

[0073] (5) As can be seen from Application Example 1 and Comparative Application Example 1-Comparative Application Example 2, if the alkenyl functional group or fluorine functional group is omitted in the present invention, and only a single functional group is used in the structure, the interface compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid cell cannot be optimized, and the overall performance of the all-solid battery cannot be improved.

[0074] (6) As can be seen from Application Example 1 and Comparative Application Example 3, if the cross-linking interface layer is not introduced, that is, if the conventional transfer method is used to peel off the PI flexible polymer film and the Li6PS5Cl solid electrolyte layer by manually bending, not only will the integrity of the solid electrolyte layer be destroyed, but the electrochemical performance of the all-solid-state battery will also be greatly reduced.

[0075] In summary, this invention introduces a cross-linked interface layer on the surface of the solid electrolyte layer and limits the structure of the raw material silane coupling agent of the cross-linked interface layer to include alkenyl and fluorine functional groups. By combining alkenyl and fluorine functional groups, the interfacial compatibility between the solid electrolyte layer and the positive electrode active material layer of the all-solid-state battery cell is optimized, thereby improving the structural stability and electrochemical performance of the all-solid-state battery cell.

[0076] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A modified all-solid-state battery cell, characterized in that, The modified all-solid-state battery cell includes a negative electrode, a solid electrolyte layer, a cross-linked interface layer, and a positive electrode layer stacked sequentially. The raw materials used in the cross-linked interface layer include silane coupling agents, and the structural formula of the silane coupling agents includes alkenyl functional groups and fluorine functional groups.

2. The modified all-solid-state battery cell according to claim 1, characterized in that, The silane coupling agent includes bifunctional coupling agents containing alkenyl and fluorine groups, or a mixture of alkenyl silane coupling agent and fluorine silane coupling agent.

3. The modified all-solid-state battery cell according to claim 2, characterized in that, The bifunctional coupling agent containing alkenyl and fluorine groups includes at least one of vinyltrifluoropropyldimethoxysilane, allyltrifluoropropyldiethoxysilane, methacryloyloxypropyltrifluoropropyldimethoxysilane, 1H,1H,2H,2H-perfluorooctylvinyldimethoxysilane, perfluorodecylallyldiethoxysilane, or p-trifluoromethylstyryltrimethoxysilane.

4. The modified all-solid-state battery cell according to claim 2, characterized in that, In the alkenyl silane coupling agent-fluorosilane coupling agent mixture, the alkenyl silane coupling agent includes at least one of vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, allyltrimethoxysilane, undecenyltrimethoxysilane, or 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane; Preferably, in the alkenylsilane coupling agent-fluorosilane coupling agent mixture, the fluorosilane coupling agent includes at least one of 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, or heptadecafluorodecyltriethoxysilane. Preferably, the mass ratio of the alkenylsilane coupling agent to the fluorosilane coupling agent is (1-2):

1.

5. The modified all-solid-state battery cell according to any one of claims 1-4, characterized in that, The solid electrolyte layer includes a sulfide solid electrolyte layer.

6. The modified all-solid-state battery cell according to any one of claims 1-5, characterized in that, The thickness of the cross-linked interface layer is 0.5μm-5μm.

7. A method for preparing a modified all-solid-state battery cell according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Mix the silane coupling agent and the hydrolysis medium solution evenly to obtain the modified coupling agent coating solution; The silane coupling agent includes an alkenyl functional group and a fluoro functional group in its structural formula. (2) The modified coupling agent coating liquid is coated on the surface of the substrate to form a modified film layer on the surface of the substrate; (3) A solid electrolyte layer is prepared on the surface of the modified film layer, and then the negative electrode active material layer and the solid electrolyte layer in the negative electrode sheet are pressed into shape, and the substrate is peeled off; (4) The positive electrode active material layer in the positive electrode sheet and the modified film layer are bonded together and hot-pressed to obtain a modified all-solid-state battery cell.

8. The preparation method according to claim 7, characterized in that, The mass concentration of the modified coupling agent coating solution in step (1) is 0.5wt%-6wt%; Preferably, the pressing pressure in step (3) is 100MPa-400MPa; Preferably, the pressing time in step (3) is 5 min to 15 min.

9. The preparation method according to claim 7 or 8, characterized in that, The heat preservation temperature for the hot pressing treatment in step (4) is 120℃-160℃; Preferably, the pressure of the hot pressing process in step (4) is 20MPa-200MPa; Preferably, the heat preservation and pressure holding time for the hot pressing treatment in step (4) is 0.3h-1h; Preferably, after the hot pressing process described in step (4) is completed, the pressure is released and the temperature is allowed to drop naturally to room temperature.

10. A modified all-solid-state battery, characterized in that, The modified all-solid-state battery includes the modified all-solid-state cell as described in any one of claims 1-6, or the modified all-solid-state cell prepared by the preparation method described in any one of claims 7-9.

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