Surface chemical modified non-woven fabric and preparation method thereof, solid electrolyte composite membrane and solid battery

Abstract

The invention relates to a surface chemical modified non-woven fabric and a preparation method thereof, a solid electrolyte composite membrane and a solid-state battery. The surface chemical modified non-woven fabric comprises a non-woven fabric substrate and a sulfur-containing functional group grafted on the surface of the non-woven fabric substrate, the sulfur-containing functional group comprises a thiol group. A specific functional group-thiol group (-SH) capable of forming a strong chemical bond with sulfide electrolyte is grafted on the surface of the inert non-woven fabric support body, a firm covalent bond (disulfide bond with bond energy of-240 kJ / mol) is formed at an interface on the premise of not additionally introducing a binder, and the strength of the solid covalent bond is far higher than that of physical Van der Waals force (bond energy lt; the surface-modified non-woven fabric prepared by the preparation method has the advantages that the surface-modified non-woven fabric is high in surface strength (50 kJ / mol), higher in interface bonding force and free of powder falling after being bent for a long time, the interface bonding force between the surface-modified non-woven fabric and the sulfide solid electrolyte is improved, the interface impedance is reduced, and meanwhile, the long-cycle stability of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, and particularly relates to a surface-chemically modified non-woven fabric, a preparation method thereof, a solid-state electrolyte composite film and a solid-state battery. BACKGROUND

[0002] The prior art solution comprises a non-woven fabric substrate and a sulfide electrolyte layer. The non-woven fabric is composed of inert polymer fibers such as polyethylene terephthalate (PET) or polypropylene (PP). The sulfide electrolyte slurry is coated on the non-woven fabric and dried to form a solid-state electrolyte layer. The combination between the two is only dependent on physical adhesion, that is, a simple mechanical anchoring is achieved through the van der Waals force of the adhesive, and there is a lack of strong chemical bonding.

[0003] CN109786817A discloses a solid-state lithium battery and its application and a method for preparing a non-woven fabric-reinforced solid-state electrolyte film. The solid-state lithium battery comprises a non-woven fabric-reinforced solid-state electrolyte film, a positive electrode, a negative electrode and a buffer layer. The non-woven fabric-reinforced solid-state electrolyte film comprises a first solid-state sulfide electrolyte, a non-woven fabric and a first adhesive. The non-woven fabric-reinforced solid-state electrolyte film has high mechanical strength and thermal stability, and no positive and negative electrode short circuit occurs during the assembly and use of the solid-state battery, has a very high preparation success rate, and the phenomenon of dendrite penetration into the electrode is significantly reduced during the use of the battery. However, the electrolyte film prepared by the method is combined by additional addition of an adhesive, which not only has weak bonding force, but also reduces the energy density of the battery.

[0004] The simple coating process commonly used in the prior art has various defects, such as weak interfacial bonding force and physical adhesion (van der Waals force) with a strength far lower than that of chemical bonds. During the subsequent hot-pressing or long-term charge-discharge cycling of the battery, the electrolyte layer is prone to peeling and delamination from the non-woven fabric due to volume changes and stress effects, resulting in internal contact failure of the battery and shortening of the cycle life. In addition, the interface has high impedance, the physical contact is point-to-point contact, the effective contact area is small, and there may be micro voids at the interface, which seriously hinder the transmission of lithium ions at the interface between the electrolyte layer and the support, causing a large interface impedance and reducing the rate performance of the battery. In addition, there are potential chemical compatibility problems. The surface of the traditional polyester (PET) and polypropylene (PP) non-woven fabric may contain oxygen-containing functional groups such as ester groups and carboxyl groups. When these groups come into contact with the water and oxygen-sensitive sulfide electrolyte (such as Li6PS5Cl), a slow chemical side reaction may occur to generate insulating layers such as Li2SO4 and Li2CO3, further deteriorating the interface ion transport performance. The root cause of the above defects lies in the fact that the interfacial interaction is weak and unstable physical adhesion rather than strong and stable chemical bonding.

[0005] Therefore, how to fundamentally solve the problems of weak bonding force, high resistance and poor chemical compatibility between the solid-state electrolyte and the non-woven fabric, and provide a non-woven fabric with more closely contacted interface, a preparation method thereof, a solid-state electrolyte composite film and a solid-state battery have become the problems to be solved at present. SUMMARY

[0006] To solve the above technical problems, the present application aims to provide a surface chemically modified non-woven fabric and a preparation method thereof, a solid-state electrolyte composite film and a solid-state battery. The surface chemically modified non-woven fabric of the present application is in close contact with the solid-state electrolyte through strong chemical bonds, without the need for additional adhesives, and the preparation process is simple and further improves the energy density of the solid-state battery.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a surface chemically modified non-woven fabric, which comprises a non-woven fabric substrate and a sulfur-containing functional group grafted on the surface of the non-woven fabric substrate; the sulfur-containing functional group comprises a thiol group.

[0009] The present application grafts a specific functional group, thiol group (-SH), which can form a strong chemical bond with sulfide electrolyte, on the surface of inert non-woven fabric support, so that the interface bonding mode between non-woven fabric and solid-state electrolyte is innovated from physical adhesion to chemical bonding, which improves the interface bonding force and reduces the interface impedance.

[0010] The following is a preferred technical solution of the present application, but not as a limitation of the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0011] Preferably, the non-woven fabric substrate comprises any one or a combination of at least two of polyphenylene sulfide (PPS), polysulfone (PSF) or polyether sulfone (PES), and a typical but non-limiting combination includes a combination of polyphenylene sulfide (PPS) and polysulfone (PSF), a combination of polysulfone (PSF) and polyether sulfone (PES), a combination of polyphenylene sulfide (PPS) and polyether sulfone (PES), a combination of polyphenylene sulfide (PPS), polysulfone (PSF) and polyether sulfone (PES), and preferably PPS.

[0012] The selected non-woven fabric substrate of the present application does not contain oxygen elements which are easy to react with sulfides, thereby avoiding the possible slow chemical side reactions when in contact with water and oxygen sensitive sulfide electrolyte (such as Li6PS5Cl).

[0013] In a second aspect, the present application provides a preparation method of the surface chemically modified non-woven fabric according to the first aspect, which comprises the following steps:

[0014] (1) immersing the non-woven fabric substrate into an oxidizing acid, and performing a first reaction to obtain a non-woven fabric containing carboxyl groups;

[0015] (2) immersing the non-woven fabric containing carboxyl groups obtained in step (1) into a thionyl chloride solution, and performing a second reaction to obtain a non-woven fabric modified by acyl chloride groups;

[0016] (3) immersing the non-woven fabric modified by acyl chloride groups obtained in step (2) into an amino-containing alkane solution, and performing a third reaction to obtain a non-woven fabric modified by amide groups;

[0017] (4) immersing the non-woven fabric modified by amide groups obtained in step (3) into a 2-iminothiolane solution, and performing a fourth reaction to obtain a non-woven fabric chemically modified on the surface.

[0018] The present application provides a specific and feasible chemical synthesis path for preparing the functionalized non-woven fabric, i.e. a four-step reaction method of "oxidation -> acyl chloride -> amide -> thiolation". The first step aims to introduce carboxyl (-COOH) functional groups on the surface of the non-woven fabric fibers, and then the carboxyl (-COOH) is converted into a highly reactive acyl chloride group (-COCl). In the third step, an aminoalkane containing at least two amino groups is used, one of which reacts with the acyl chloride group to form a stable amide bond (-CO-NH-), thereby grafting a molecular chain with a free amino group (-NH2) on the surface of the non-woven fabric fibers. In the fourth step, the free amino group is converted into a thiol group (-SH) by using a 2-iminothiolane reagent which specifically reacts with primary amines.

[0019] Preferably, the oxidizing acid in step (1) comprises nitric acid.

[0020] The present application preferably uses nitric acid, which has moderate oxidizing strength and is easy to control, and is a commonly used reagent for introducing oxygen-containing functional groups on the surface of polymer materials. If a mixed acid of sulfuric acid and nitric acid is used, the oxidizing strength is stronger, which is suitable for more difficult to oxidize polymers, but may cause the strength of the fibers to decrease due to excessive oxidation. Hydrogen peroxide (H2O2) oxidizing agent can be used in the presence of a specific catalyst (such as Fe 2+ ), which is a relatively environmentally friendly solution, but the reaction efficiency and grafting density may not be as good as nitric acid. The solution of potassium permanganate (KMnO4) oxidizing agent under acidic conditions has extremely strong oxidizing strength, but the post-treatment is complex and may leave manganese ions.

[0021] Preferably, the mass concentration of the nitric acid is 60%-68%, for example, it can be 60%, 62%, 65% or 68%, but is not limited to the listed values, and other unlisted values within the value range are also applicable.

[0022] Preferably, after the first reaction in step (1), before obtaining the non-woven fabric containing carboxyl groups, it further includes cleaning and drying.

[0023] Preferably, the temperature of the first reaction in step (1) is 50-70°C, for example, it can be 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C or 70°C, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0024] The present application further controls the temperature of the first reaction to be 50-70°C, and the temperature of the first reaction affects the reaction kinetics and the grafting density of the carboxyl group; if the temperature of the first reaction is too high, the oxidation reaction is too violent, not only introducing -COOH, but also producing a large amount of other oxygen-containing groups, and possibly severely etching the surface of the PPS fiber, resulting in the fiber becoming thin and brittle, and the mechanical strength (tensile strength, flexibility) of the non-woven fabric significantly decreasing, and even possibly breaking during processing; if the temperature of the first reaction is too low, the reaction kinetics is slow, and the grafting density of the carboxyl group (-COOH) is insufficient, resulting in insufficient "substrate" for subsequent reactions, and finally low density of thiol groups (-SH), affecting the interface bonding effect.

[0025] Preferably, the time of the first reaction is 20-40 min, for example, it can be 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 38 min or 40 min, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0026] Preferably, the temperature of the second reaction in step (2) is 65-75°C, for example, it can be 65°C, 68°C, 70°C, 72°C or 75°C, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0027] Preferably, the time of the second reaction is 1-3 h, for example, it can be 1 h, 1.5 h, 2 h, 2.5 h or 3 h, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0028] Preferably, the concentration of the amino-containing alkane solution in step (3) is 1-3 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but is not limited to the listed values, and other values not listed within the value range are also applicable.

[0029] Preferably, the amino-containing alkane includes any one or a combination of at least two of ethylenediamine, hexamethylenediamine or diethylenetriamine, typical but non-limiting combinations include a combination of ethylenediamine and hexamethylenediamine, a combination of hexamethylenediamine and diethylenetriamine, a combination of ethylenediamine and diethylenetriamine, a combination of ethylenediamine, hexamethylenediamine and diethylenetriamine, and preferably ethylenediamine.

[0030] Preferably, the temperature of the third reaction in step (3) is 40-60℃, for example, it can be 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃ or 60℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] Preferably, the time of the third reaction is 4-8h, for example, it can be 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h or 8h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the concentration of the 2-iminothiolane solution in step (4) is 10-50mmol / L, for example, it can be 10mmol / L, 15mmol / L, 20mmol / L, 25mmol / L, 30mmol / L, 35mmol / L, 40mmol / L, 45mmol / L or 50mmol / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] By further controlling the concentration of the 2-iminothiolane solution to be 10-50mmol / L, the concentration of the 2-iminothiolane solution affects the effect of the thiolation reaction; if the concentration of the 2-iminothiolane solution is too high, the molecules in the solution may undergo self-reaction or dimerization, consuming effective reaction components, which not only causes waste of reagents, but more importantly, the self-reaction product may be physically adsorbed on the surface of the non-woven fabric, forming an irregular, non-covalently bound impurity layer. This layer of impurities may hinder the effective contact of the thiol group with the electrolyte, and even introduce new interface impedance. In addition, too high a concentration may also cause unnecessary side reactions on the amide bonds on the surface of the fiber; if the concentration of the 2-iminothiolane solution is too low, the reactant molecules are insufficient, the reaction rate with the amine group is slow and incomplete. Finally, the density of the thiol group (-SH) on the surface of the non-woven fabric is low. When combined with the sulfide electrolyte later, the number of disulfide bonds (-S-S-) that can be formed is small, resulting in insufficient interface chemical bonding strength, greatly reducing the effect of improving the interface impedance and bonding force. The performance may not differ much from the unmodified sample.

[0034] Preferably, the pH of the 2-iminothiolane solution in step (4) is 8-9, for example, it can be 8, 8.5 or 9, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0035] Preferably, the temperature of the fourth reaction in step (4) is 40-60℃, for example, it can be 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃ or 60℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0036] Preferably, the time of the fourth reaction is 0.5-2h, for example, it can be 0.5h, 1h, 1.5h or 2h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] In a third aspect, the present application provides a solid-state electrolyte composite film, which comprises the surface-chemically modified non-woven fabric of the first aspect and a sulfide electrolyte layer coated on the surface of the surface-chemically modified non-woven fabric.

[0038] In the solid-state electrolyte composite film provided by the present application, the surface-modified non-woven fabric and the sulfide solid-state electrolyte are chemically bonded, forming a firm covalent bond (disulfide bond, bond energy ~240 kJ / mol) at the interface, which is much stronger than the physical van der Waals force (bond energy <50 kJ / mol), and the interface bonding force is stronger, and there is no powder falling phenomenon after long-time bending; and the strong chemical bonding ensures the "molecular level" close contact between the electrolyte and the non-woven fabric, significantly increases the effective contact area, provides a high-efficiency and continuous transmission channel for lithium ions, and has smaller interface resistance; in addition, the interface is connected through S-S bond, and the chemical environment is highly compatible with the bulk of the sulfide electrolyte, avoiding the occurrence of heterogeneous interface side reactions, and having higher chemical stability.

[0039] In a fourth aspect, the present application provides a preparation method of the solid-state electrolyte composite film of the third aspect, which comprises:

[0040] Coating a sulfide electrolyte slurry on the surface of the surface-chemically modified non-woven fabric of the first aspect, and drying to obtain the solid-state electrolyte composite film.

[0041] When the sulfide electrolyte slurry is coated on the functionalized non-woven fabric, the thiol groups (-SH) on the surface thereof react with the sulfur ions (S 2- ) or [S-P-S] 4- structures in the sulfide electrolyte during subsequent drying or heat treatment, forming firm disulfide bonds (-S-S-), and realizing chemical bonding at the interface.

[0042] Preferably, the thickness of the surface-chemically modified non-woven fabric in the solid-state electrolyte composite film is 5-50μm, and the thickness of the sulfide electrolyte layer is 5-50μm.

[0043] Preferably, the sulfide electrolyte slurry comprises Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li6PS5I, Li6PS5ClBr, Li 10 SnP2S 12 , Li7GePS8, 70Li2S-30P2S5, Li2S-SiS2, 80Li2S-20P2S5, or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , or a combination of at least two of them.

[0044] Preferably, the sulfide electrolyte slurry further comprises a solvent and a binder.

[0045] Preferably, the solvent has a dielectric constant of no more than 15 at 25℃, and is an aprotic solvent. The solvent comprises one or more of toluene, xylene, mesitylene, n-heptane, cyclohexane, hexane, or petroleum ether.

[0046] Preferably, the binder is a polymer that is soluble or swellable in the solvent. The binder comprises any one or a combination of at least two of styrene butadiene rubber, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, polyisoprene, polyisobutylene, hydrogenated polybutadiene, ethylene-propylene-diene terpolymer, or polyurethane.

[0047] In a fifth aspect, the present application provides a solid-state battery, comprising the solid-state electrolyte composite film of the third aspect.

[0048] The solid-state battery provided by the present application has extremely strong interface bonding force, extremely low interface impedance, and excellent chemical stability. After the standard 90° bending resistance test, the bonding force between the surface modified non-woven fabric and the sulfide electrolyte layer is stronger, and there is no powder falling phenomenon after long-time bending, which fundamentally solves the interface delamination problem in the battery cycle process, greatly improves the cycle life and reliability of the battery; its impedance can be reduced from the traditional physical bonding of more than 100Ω·cm 2 to 20Ω·cm 2 The following significantly reduces the polarization of the battery; the assembled full battery is subjected to charge-discharge cycle test, and the capacity retention rate of the surface modified non-woven fabric is >80% after 800 cycles, while the capacity retention rate of the unmodified non-woven fabric is <80% after 200 cycles.

[0049] The numerical ranges recited herein include all values from and including the lower and upper values. This is true even if the values included in the lower or upper range are outside of the recited range. The ranges are presented essentially to reflect that a particular set of examples will have, e.g., a lower and upper value. However, unless the context clearly indicates otherwise, it is contemplated that this is not to be a limitation on the scope of valid scope of the disclosure. Nor is the presentation of a range intended to be a limitation on the scope of valid scope of the disclosure. To that end, all numerical ranges are to be understood as being inclusive of their endpoints and all intervening values. Unless otherwise indicated, all ranges are inclusive of the recited range cap and floor values.

[0050] Compared with the prior art, the present application has at least the following beneficial effects:

[0051] (1) The present application grafts a specific functional group-sulfhydryl (-SH) which can form a strong chemical bond with sulfide electrolyte on the surface of inert non-woven fabric support, so that the interface bonding mode between non-woven fabric and solid-state electrolyte is innovated from physical adhesion to chemical bonding, the interface bonding force is improved, and the interface impedance is reduced.

[0052] (2) In the solid-state electrolyte composite film provided by the present application, the surface modified non-woven fabric and the sulfide solid-state electrolyte are connected by chemical bonding at the interface, forming a firm covalent bond (disulfide bond, bond energy ~240 kJ / mol), which is much stronger than the physical van der Waals force (bond energy <50 kJ / mol), and the interface bonding force is stronger, and there is no powder falling phenomenon after long-time bending; and the strong chemical bonding ensures the "molecular level" close contact between the electrolyte and the non-woven fabric, significantly increases the effective contact area, provides a high-efficiency and continuous transmission channel for lithium ions, and has smaller interface resistance; in addition, the interface is connected through S-S bond, and the chemical environment is highly compatible with the bulk of sulfide electrolyte, avoiding the occurrence of heterogeneous interface side reaction, and having higher chemical stability.

[0053] (3) The solid-state battery provided by the present application has extremely strong interface bonding force, extremely low interface impedance and excellent chemical stability, the bonding force between the surface modified non-woven fabric and the sulfide electrolyte layer is stronger after the standard 90° bending resistance test, and there is no powder falling phenomenon after long-time bending, which fundamentally solves the interface delamination problem in the battery cycle process, greatly improves the cycle life and reliability of the battery; the impedance can be reduced from more than 100Ω·cm 2 to 20Ω·cm 2 which significantly reduces the polarization of the battery; the assembled full battery is subjected to charge-discharge cycle test, the capacity retention rate of the surface modified non-woven fabric is >80% after 800 cycles, and the capacity retention rate of the unmodified non-woven fabric is <80% after 200 cycles. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is the electrochemical impedance spectrum of the solid-state battery assembled by the present application example 1 and the comparative example 1;

[0055] Figure 2 is the capacity retention rate diagram of the solid-state battery assembled by the present application example 1 and the comparative example 1 after 800 cycles. DETAILED DESCRIPTION

[0056] The technical solutions of the present application will be further illustrated by the following embodiments. It should be understood by those skilled in the art that the embodiments are only used to help understand the present application, and should not be regarded as specific limitations to the present application.

[0057] In the present application, the terms "first", "second", "third", "fourth" and the like in "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only used for description purposes, and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implying the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0058] In the following examples and comparative examples, all reagents and consumables are purchased from conventional reagent manufacturers in the art, unless otherwise specified. The experimental methods and technical means used are conventional methods and means in the art, unless otherwise specified.

[0059] Example 1

[0060] The present embodiment provides a surface chemically modified non-woven fabric, which comprises a polyphenylene sulfide non-woven fabric substrate and a thiol group grafted on the surface of the non-woven fabric substrate;

[0061] The preparation method of the surface chemically modified non-woven fabric provided by the present embodiment comprises the following steps:

[0062] (1) The polyphenylene sulfide non-woven fabric substrate is immersed in 68% nitric acid, and the first reaction is carried out at 60°C for 30 min, and then washed and dried to obtain a carboxyl-containing non-woven fabric;

[0063] (2) The carboxyl-containing non-woven fabric obtained in step (1) is immersed in thionyl chloride, and the second reaction is carried out at 70°C for 2 h to obtain an acyl chloride group modified non-woven fabric;

[0064] (3) The acyl chloride group modified non-woven fabric obtained in step (2) is immersed in an amino-containing alkane solution with a concentration of 2 mol / L, and the third reaction is carried out at 50°C for 6 h to obtain an amide group modified non-woven fabric;

[0065] (4) The amide group modified non-woven fabric obtained in step (3) is immersed in a 2-iminothiol solution with a concentration of 30 mmol / L and a pH of 8.5, and the fourth reaction is carried out at 50°C for 1 h to obtain a surface chemically modified non-woven fabric.

[0066] Example 2

[0067] The present embodiment provides a surface-chemically modified nonwoven fabric, which comprises a polysulfone (PSF) nonwoven fabric substrate and thiol groups grafted on the surface of the nonwoven fabric substrate;

[0068] The present embodiment provides a method for preparing the surface-chemically modified nonwoven fabric, which comprises the following steps:

[0069] (1) immerse a polysulfone (PSF) nonwoven fabric substrate in nitric acid with a mass concentration of 60%, and react at 70°C for 35 min in the first reaction, and then clean and dry to obtain a nonwoven fabric containing carboxyl groups;

[0070] (2) immerse the nonwoven fabric containing carboxyl groups obtained in step (1) in thionyl chloride, and react at 65°C for 3 h in the second reaction to obtain a nonwoven fabric modified by acyl chloride groups;

[0071] (3) immerse the nonwoven fabric modified by acyl chloride groups obtained in step (2) in an alkane solution containing amino groups with a concentration of 1 mol / L, and react at 40°C for 8 h in the third reaction to obtain a nonwoven fabric modified by amide groups;

[0072] (4) immerse the nonwoven fabric modified by amide groups obtained in step (3) in a 2-iminothiol solution with a concentration of 10 mmol / L and a pH of 8, and react at 40°C for 2 h in the fourth reaction to obtain a surface-chemically modified nonwoven fabric.

[0073] Embodiment 3

[0074] The present embodiment provides a surface-chemically modified nonwoven fabric, which comprises a polyethersulfone (PES) nonwoven fabric substrate and thiol groups grafted on the surface of the nonwoven fabric substrate;

[0075] The present embodiment provides a method for preparing the surface-chemically modified nonwoven fabric, which comprises the following steps:

[0076] (1) immerse a polyethersulfone (PES) nonwoven fabric substrate in nitric acid with a mass concentration of 68%, and react at 50°C for 40 min in the first reaction, and then clean and dry to obtain a nonwoven fabric containing carboxyl groups;

[0077] (2) immerse the nonwoven fabric containing carboxyl groups obtained in step (1) in thionyl chloride, and react at 75°C for 1 h in the second reaction to obtain a nonwoven fabric modified by acyl chloride groups;

[0078] (3) immerse the nonwoven fabric modified by acyl chloride groups obtained in step (2) in an alkane solution containing amino groups with a concentration of 3 mol / L, and react at 60°C for 4 h in the third reaction to obtain a nonwoven fabric modified by amide groups;

[0079] (4) The amide group modified non-woven fabric obtained in step (3) is immersed in a 2-iminothiolane solution with a concentration of 50 mmol / L and a pH of 9, and a fourth reaction is carried out at 60°C for 0.5 h to obtain a surface chemically modified non-woven fabric.

[0080] Example 4

[0081] This example provides a surface chemically modified non-woven fabric, which is different from example 1 only in that when preparing the surface chemically modified non-woven fabric, the temperature of the first reaction in step (1) is replaced from 60°C to 40°C.

[0082] Example 5

[0083] This example provides a surface chemically modified non-woven fabric, which is different from example 1 only in that when preparing the surface chemically modified non-woven fabric, the temperature of the first reaction in step (1) is replaced from 60°C to 80°C.

[0084] Example 6

[0085] This example provides a surface chemically modified non-woven fabric, which is different from example 1 only in that when preparing the surface chemically modified non-woven fabric, the concentration of the 2-iminothiolane solution in step (4) is replaced from 30 mmol / L to 5 mmol / L.

[0086] Example 7

[0087] This example provides a surface chemically modified non-woven fabric, which is different from example 1 only in that when preparing the surface chemically modified non-woven fabric, the concentration of the 2-iminothiolane solution in step (4) is replaced from 30 mmol / L to 60 mmol / L.

[0088] Comparative Example 1

[0089] This comparative example provides a non-woven fabric, which is polyphenylene sulfide (PPS) and has not been modified.

[0090] Application Example 1

[0091] This application example provides a solid-state electrolyte composite film, which comprises the surface chemically modified non-woven fabric of example 1 and a Li6PS5Cl sulfide electrolyte with a thickness of 25 μm coated on the surface;

[0092] The solid-state electrolyte composite film is prepared by the following preparation method:

[0093] A Li6PS5Cl sulfide electrolyte slurry is coated on the surface of the surface chemically modified non-woven fabric obtained in example 1, and dried to obtain the solid-state electrolyte composite film.

[0094] Application Examples 2-7

[0095] Application Examples 2-7 each provide a solid-state electrolyte composite film, which is different from that of Application Example 1 in that the surface-chemically modified non-woven fabric of Example 1 is replaced by the surface-chemically modified non-woven fabric of Example 2-7, respectively, and the rest of the preparation method remains unchanged.

[0096] Comparative Application Example 1

[0097] Comparative Application Example 1 provides a solid-state electrolyte composite film, which is different from that of Application Example 1 in that the surface-chemically modified non-woven fabric of Example 1 is replaced by the non-woven fabric of Comparative Example 1, and the rest of the preparation method remains unchanged.

[0098] Comparative Application Example 2

[0099] Comparative Application Example 2 provides a solid-state electrolyte composite film, which is prepared by a conventional physical bonding method, and the specific preparation method is as follows:

[0100] The Li6PS5Cl electrolyte and SEBS are added to dimethylbenzene in a mass ratio of 98:2, stirred for 10 h for dissolution, to obtain an electrolyte slurry.

[0101] The slurry obtained in the above step is coated on the unmodified non-woven fabric, the coating thickness is controlled to be 50 μm, and drying is performed under an inert atmosphere to obtain an electrolyte layer.

[0102] Test:

[0103] The solid-state electrolyte composite films prepared in the application examples and comparative application examples, and the solid-state batteries assembled with the composite positive electrode material and the composite negative electrode material, are tested. The test results are shown in Table 1, Figure 1 and Figure 2 .

[0104] The composite positive electrode comprises: a high-nickel ternary positive electrode material, a VGCF conductive agent, and a solid-state electrolyte powder.

[0105] The composite negative electrode is a lithium-indium alloy material.

[0106] Bending test method: the electrolyte composite film is cut into a 50 mm x 10 mm sample, and in an inert atmosphere, it is bent around a 3 mm radius shaft for 90° reciprocating bending at a speed of 1 time / second. By observation, the bending cycle number when the electrolyte layer cracks or peels off from the non-woven fabric is recorded. The test results are shown in Table 1.

[0107] Interface impedance test method: the assembled battery is connected to the electrochemical workstation, the frequency is 0.1 Hz-3000000 Hz, the amplitude is 5 mV, and EIS test is carried out. The test results are shown in Table 1.

[0108] Battery test method: charge and discharge cycle at 0.1C current density, record the capacity data after cycle, and compare with the capacity of the first cycle. The test results are shown in Table 1.

[0109] Electrolyte membrane impedance test: the prepared electrolyte membrane is cut into 10 mm round pieces, and stainless steel blocking electrodes are used on both sides to test EIS at 350 MPa, and the test conditions are consistent with the interface impedance test method. The test results are shown in Figure 1 .

[0110] The electrochemical impedance spectrum of the electrolyte membrane prepared in Example 1 and Comparative Example 1 is shown in Figure 1 , from the figure, it can be seen that the impedance value of Example 1 is much lower than that of Comparative Example 1, which is mainly because the addition of adhesive component is reduced, and the influence on lithium ion diffusion channel is minimized;

[0111] The long cycle diagram of the solid-state battery assembled by Example 1 and Comparative Example 1 is shown in Figure 2 , from the figure, it can be seen that the modified non-woven fabric electrolyte membrane has stronger interface stability, tighter cycle interface contact, and higher cycle capacity retention rate compared with the unmodified one.

[0112] Table 1

[0113]

[0114] From the test results, it can be seen that:

[0115] (1) From Application Example 1-Application Example 3, it can be seen that the present application grafts a specific functional group-sulfhydryl group (-SH) which can form strong chemical bond with sulfide electrolyte on the surface of inert non-woven fabric support, so that the interface bonding mode between non-woven fabric and solid-state electrolyte is innovated from physical adhesion to chemical bonding. The surface modified non-woven fabric and sulfide solid-state electrolyte are bonded by chemical bonding, forming a firm covalent bond (disulfide bond, bond energy ~240 kJ / mol) at the interface, which is much stronger than physical van der Waals force (bond energy <50 kJ / mol), and the interface bonding force is stronger, and there is no powder falling phenomenon after long time bending. Its impedance can be reduced from more than 100Ω·cm 2 to 20Ω·cm 2 , which significantly reduces the polarization of the battery; the assembled full battery is tested by charge and discharge cycle, the capacity retention rate of the surface modified non-woven fabric is >80% after 800 cycles, while the capacity retention rate of the unmodified non-woven fabric is <80% after 200 cycles.

[0116] (2) By comparing application example 1 with application examples 4-5, it can be seen that, by further controlling the temperature of the first reaction to be 50-70℃, the temperature of the first reaction affects the reaction kinetics and the grafting density of the carboxyl group; if the temperature of the first reaction is too high, the oxidation reaction is too violent, not only introducing -COOH, but also producing a large amount of other oxygen-containing groups, and possibly seriously etching the surface of the PPS fiber, resulting in the fiber becoming thin and brittle, and the mechanical strength (tensile strength, flexibility) of the non-woven fabric significantly decreasing, and even possibly breaking during processing; if the temperature of the first reaction is too low, the reaction kinetics is slow, and the grafting density of the carboxyl group (-COOH) is insufficient, resulting in insufficient "substrate" for subsequent reactions, and finally low density of thiol groups (-SH), affecting the interface bonding effect.

[0117] (3) By comparing application example 1 with application examples 6-7, it can be seen that, by further controlling the concentration of the 2-imino sulfane solution to be 10-50 mmol / L, the concentration of the 2-imino sulfane solution affects the thiolation reaction effect; if the concentration of the 2-imino sulfane solution is too high, the molecules in the solution may undergo self-reaction or dimerization, consuming effective reaction components, which not only causes reagent waste, but more importantly, the self-reaction products may be physically adsorbed on the surface of the non-woven fabric, forming an irregular, non-covalently bonded impurity layer. This impurity layer may hinder the effective contact of the thiol groups with the electrolyte, and even introduce new interface impedance. In addition, too high a concentration may also cause unnecessary side reactions to the amide bonds on the surface of the fiber; if the concentration of the 2-imino sulfane solution is too low, the reactant molecules are insufficient, and the reaction rate with the amine group is slow and incomplete. Finally, the density of the thiol groups (-SH) on the surface of the non-woven fabric is low. When combined with the sulfide electrolyte in the subsequent step, the number of disulfide bonds (-S-S-) formed is small, resulting in insufficient interface chemical bonding strength, and the effect of improving the interface impedance and bonding force is greatly reduced. The performance may not differ much from the unmodified sample.

[0118] (4) By comparing application example 1 with comparative application examples 1-2, it can be seen that, by grafting a specific functional group - thiol group (-SH) on the surface of the inert non-woven fabric support, which can form a strong chemical bond with the sulfide electrolyte, without the need for additional introduction of a binder, the interface bonding force between the surface-modified non-woven fabric and the sulfide solid-state electrolyte is improved, the interface impedance is reduced, and the long-cycle stability performance of the battery is improved.

[0119] In summary, the present application grafts a specific functional group - thiol group (-SH) on the surface of inert non-woven fabric support, which can form strong chemical bonds with sulfide electrolyte, so that the interface bonding mode between non-woven fabric and solid electrolyte is innovated from physical adhesion to chemical bonding. Through the action of chemical bonding between the surface modified non-woven fabric and the sulfide solid electrolyte, a firm covalent bond (disulfide bond, bond energy ~ 240 kJ / mol) is formed at the interface, which is much stronger than the physical van der Waals force (bond energy < 50 kJ / mol), and the interface bonding force is stronger, and there is no powder falling phenomenon after long time bending. Its impedance can be reduced from more than 100Ω·cm 2 to 20Ω·cm 2 The following significantly reduces the polarization of the battery; the assembled full cell is tested for charge and discharge cycle, the capacity retention rate of the surface modified non-woven fabric is >80% after 800 cycles, while the capacity retention rate of the unmodified non-woven fabric is <80% after 200 cycles.

[0120] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A surface-chemically modified nonwoven fabric, characterized in that, The surface chemically modified nonwoven fabric includes a nonwoven fabric substrate and sulfur-containing functional groups grafted onto the surface of the nonwoven fabric substrate. The sulfur-containing functional groups include thiols.

2. The surface-chemically modified nonwoven fabric according to claim 1, characterized in that, The nonwoven substrate includes any one or a combination of at least two of polyphenylene sulfide, polysulfone, or polyethersulfone.

3. A method for preparing a surface-chemically modified nonwoven fabric as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) The nonwoven fabric substrate is immersed in an oxidizing acid, and after the first reaction, a nonwoven fabric containing carboxyl groups is obtained; (2) The nonwoven fabric containing carboxyl groups obtained in step (1) is immersed in thionyl chloride and subjected to a second reaction to obtain nonwoven fabric modified with acyl chloride groups; (3) The acyl chloride-modified nonwoven fabric obtained in step (2) is immersed in an amino-containing alkane solution, and after a third reaction, an amide-modified nonwoven fabric is obtained; (4) The amide-modified nonwoven fabric obtained in step (3) is immersed in a 2-iminothion solution and subjected to a fourth reaction to obtain a surface chemically modified nonwoven fabric.

4. The preparation method according to claim 3, characterized in that, The oxidizing acid in step (1) includes nitric acid; Preferably, the mass concentration of the nitric acid is 60%-68%; Preferably, in step (1), after the first reaction and before obtaining the carboxyl-containing nonwoven fabric, the process further includes cleaning and drying; Preferably, the temperature of the first reaction in step (1) is 50℃-70℃; Preferably, the reaction time for the first reaction is 20 min to 40 min; Preferably, the temperature of the second reaction in step (2) is 65℃-75℃; Preferably, the second reaction takes 1-3 hours.

5. The preparation method according to claim 3 or 4, characterized in that, The concentration of the amino-containing alkane solution in step (3) is 1 mol / L-3 mol / L; Preferably, the amino-containing alkane includes any one or a combination of at least two of ethylenediamine, hexamethylenediamine, or diethylenetriamine; Preferably, the temperature of the third reaction in step (3) is 40℃-60℃; Preferably, the third reaction takes 4-8 hours.

6. The preparation method according to any one of claims 3-5, characterized in that, The concentration of the 2-iminothione solution in step (4) is 10 mmol / L-50 mmol / L; Preferably, the pH of the 2-iminothione solution in step (4) is 8-9; Preferably, the temperature of the fourth reaction in step (4) is 40℃-60℃; Preferably, the fourth reaction takes 0.5h-2h.

7. A solid electrolyte composite membrane, characterized in that, The solid electrolyte composite membrane comprises the surface chemically modified nonwoven fabric as described in claim 1 or 2 and a sulfide electrolyte layer coated on the surface of the surface chemically modified nonwoven fabric.

8. A method for preparing a solid electrolyte composite membrane as described in claim 7, characterized in that, The preparation method includes: The sulfide electrolyte slurry is coated onto the surface of the surface chemically modified nonwoven fabric as described in claim 1 or 2, and then dried to obtain the solid electrolyte composite membrane.

9. The method for preparing a solid electrolyte composite membrane according to claim 8, characterized in that, The thickness of the surface chemically modified nonwoven fabric in the solid electrolyte composite membrane is 5μm-50μm, and the sulfide electrolyte layer contains a nonwoven fabric structure with a thickness of 5μm-50μm; Preferably, the sulfide electrolyte slurry comprises Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 , Li6PS5Cl, Li6PS5Br, Li6PS5I, Li6PS5ClBr, Li 10 SnP2S 12 Li7GePS8, 70Li2S-30P2S5, Li2S-SiS2, 80Li2S-20P2S5 or Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Any one or at least two of them.

10. A solid-state battery, characterized in that, The solid-state battery includes the solid electrolyte composite membrane as described in claim 8 or 9.

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