Binder for solid-state battery, preparation method of binder, electrolyte membrane, preparation method of electrolyte membrane and solid-state battery

Abstract

The invention provides a binder for a solid-state battery, a preparation method of the binder, an electrolyte membrane, a preparation method of the electrolyte membrane and the solid-state battery, and relates to the field of secondary batteries. The binder for the solid-state battery comprises a first repetitive unit, and the structural formula of the first repetitive unit is shown as a formula I: # imgabs0 #, wherein R1 comprises alkyl; r2 comprises one of a carboxyl group, a siloxy epoxy group, a siloxy group, an epoxy group, fluorine and an alkyl group; r3 comprises a chemical bond, alkyl or phenyl; r'comprises alkyl. The binder provided by the invention has hydrophobicity, can effectively prevent water from entering the battery, reduces short circuit and corrosion risks caused by water, and is helpful for improving the safety and stability of the battery.

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and particularly to a binder for a solid-state battery, a preparation method thereof, an electrolyte membrane thereof, a preparation method thereof, and a solid-state battery. Background Art

[0002] With the increasing demand for battery safety and energy density in the field of new energy power batteries, the traditional lithium-ion liquid batteries using liquid electrolytes can no longer meet the needs of the world's development for high-safety and high-energy-density batteries. Therefore, solid-state batteries using solid electrolytes have received extensive attention due to their high safety and energy density.

[0003] In a solid-state battery, the electrolyte membrane replaces the electrolyte solution and separator of a traditional liquid battery, isolates the positive and negative electrodes, and plays a role in transferring lithium ions at the same time. Therefore, the electrolyte membrane requires high ionic conductivity. There are mainly three types of solid electrolytes in existing solid-state batteries: polymer solid electrolytes, sulfide solid electrolytes, and oxide solid electrolytes. Among them, sulfide solid electrolytes have both high ionic conductivity, a wide electrochemical window, and good mechanical strength. Therefore, they are considered to be solid electrolyte materials with good application prospects. However, sulfide electrolytes themselves are prone to react with water in the air, which directly affects the ionic conductivity, making the preparation process and use process of sulfide electrolyte membranes require an anhydrous and anaerobic environment. The high requirements for the environment have hindered the large-scale production and use of sulfide electrolyte membranes.

[0004] The hydrophobic effect of existing binders for solid-state batteries is poor, which not only affects their performance and safety in practical applications, but also limits their application scope. Summary of the Invention

[0005] The purpose of the present application is to provide a binder for a solid-state battery, a preparation method thereof, an electrolyte membrane thereof, a preparation method thereof, and a solid-state battery to solve the above problems.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] A binder for a solid-state battery, the binder for a solid-state battery includes a first repeating unit, and the structural formula of the first repeating unit is shown in Formula I:

[0008]

[0009] Wherein, R 1 includes a hydrocarbon group;

[0010] R 2 includes one of a carboxyl group, a siloxane epoxy group, a siloxy group, fluorine, and an alkyl group;

[0011] R 3Comprising a chemical bond, a hydrocarbon group or a phenyl group;

[0012] R' comprises an alkyl group.

[0013] According to an embodiment of the present application, the structural formula of the first repeating unit comprises any one of the following structural formulas:

[0014]

[0015]

[0016] The present application also provides a method for preparing the binder for a solid-state battery as described above, comprising:

[0017] Reacting a resin with a halogenated alkane to obtain a binder for a solid-state battery, wherein the resin comprises a second repeating unit, the structural formula of the second repeating unit is as shown in Formula II, the structural formula of the halogenated alkane is as shown in Formula III, and X comprises chlorine or bromine;

[0018]

[0019] According to an embodiment of the present application, the reaction is carried out in the presence of a catalyst, and the catalyst comprises sodium hydroxide, potassium hydroxide or concentrated sulfuric acid;

[0020] And / or, the reaction is carried out in the presence of an organic solvent, and the organic solvent comprises any one of dimethylformamide and dimethyl sulfoxide;

[0021] And / or, the molecular weight of the resin is 80,000 - 5,000,000;

[0022] And / or, the mass ratio of the resin to the compound of Formula III is (70 - 99):(1 - 30), the catalyst accounts for 1 - 5 wt% of the resin, and the solid content of the reaction system before the reaction is 10 - 30%;

[0023] And / or, the temperature of the reaction is 40 - 80 °C, and the time of the reaction is 24 - 72 h.

[0024] The present application also provides an electrolyte membrane, and the raw material of the electrolyte membrane comprises the binder for a solid-state battery as described above or the binder for a solid-state battery prepared by the method as described above.

[0025] The present application also provides a method for preparing a sulfide electrolyte membrane, comprising:

[0026] Mixing a binder with a first solvent to obtain a coating solution, coating the coating solution on a base film, and performing a first drying treatment to form a protective layer on the base film;

[0027] Mix the binder with a second solvent, a sulfide electrolyte, and a lithium salt to obtain a slurry. Coat the slurry on the surface of the protective layer away from the base film, and perform a second drying treatment to form an electrolyte film on the base film;

[0028] Among them, the binder includes the binder for solid-state batteries described above or the binder for solid-state batteries prepared by the method described above.

[0029] According to an embodiment of the present application, in the coating liquid, the mass ratio of the binder to the first solvent is (1-5):(95-99);

[0030] And / or, after mixing the binder with the first solvent, the method further includes: stirring at a temperature of 50-100°C for 12-24 h to obtain a coating liquid;

[0031] And / or, the first solvent includes at least one of dimethyl succinate, dimethyl glutarate, and dimethyl adipate;

[0032] And / or, the temperature of the first drying treatment is 60-200°C;

[0033] And / or, the time of the first drying treatment is 6-12 h.

[0034] According to an embodiment of the present application, the coating amount of the coating liquid on the base film is 0.01-3 mg / cm 2 .

[0035] According to an embodiment of the present application, in the slurry, the mass ratio of the binder to the sulfide electrolyte is (10-30):(70-90), the mass of the lithium salt is 40-70% of the mass of the binder, and the solid content of the slurry is 50-80%;

[0036] And / or, the sulfide electrolyte includes Li 3 PS 4 , Li 7 P 3 S 11 , 80Li 2 S-20P 2 S 5 , Li 7-x PS 6-x Y x at least one of them, where Y is Cl, Br or I, and x = 0-1.6;

[0037] And / or, the lithium salt includes at least one of LiTFSI, LiFSI, LiPF 6 , LiDFOB, LiBOB;

[0038] And / or, the second solvent includes at least one of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0039] According to an embodiment of the present application, the second drying treatment includes: standing at room temperature for 0.4 - 0.6 h, and then drying at a temperature of 40 - 50 °C for 22 - 26 h.

[0040] According to an embodiment of the present application, the thickness of the electrolyte membrane is 40 - 100 μm.

[0041] The present application also provides a solid-state battery, which includes the electrolyte membrane described above or an electrolyte membrane prepared by the preparation method described above.

[0042] Compared with the prior art, the beneficial effects of the present application include:

[0043] The hydroxyl groups in the binder of the present application generate ether bonds through an etherification reaction, which can improve the hydrophobic property of the binder and also improve the compatibility between the binder and the sulfide electrolyte, contributing to improving the safety and stability of the battery.

[0044] In the present application, the base film is first coated with a coating solution, which can form a dense protective layer on the base film. When the electrolyte membrane is used, the electrolyte membrane needs to be separated from the base film. At this time, the dense protective layer can separate moisture from the sulfide electrolyte and effectively protect the sulfide electrolyte. In addition, the complexing ability of the ether bond with lithium ions is beneficial to the efficient transport of lithium ions. In the dynamic process of the formation and dissociation of this complex, the rapid transfer of lithium ions in the sulfide electrolyte membrane is promoted, laying a solid foundation for maintaining excellent lithium-ion conductivity in an electrolyte membrane system with a high binder content. Specifically, the complexing effect of the ether bond with lithium ions not only accelerates the migration speed of lithium ions but also balances the adverse effects brought by the high binder content, making the electrolyte membrane have excellent hydrophobicity and high ionic conductivity. This strategy, while ensuring the high stability of the electrolyte membrane, greatly promotes the performance of the battery's electrical properties and opens up a new way for realizing a more efficient and stable battery system.

[0045] Generally speaking, by adopting the solution of the present application, a dense hydrophobic film protects the sulfide electrolyte during both the preparation and use of the electrolyte membrane, avoiding direct contact between moisture and the sulfide electrolyte, and enabling the stable coating and use of the sulfide electrolyte membrane in the air. The present application can reduce the environmental requirements for the electrolyte membrane during preparation, storage, and use to meet the actual wide application in the large-scale production of sulfide electrolyte membranes. Detailed Embodiments

[0046] As used herein, the terms:

[0047] "Prepared from" is synonymous with "comprising". As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus comprising the listed elements need not be limited to those elements alone, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0048] The conjunctive "consisting of" excludes any unrecited element, step or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the claim body rather than immediately following the subject, it only limits the elements described in that clause; other elements are not excluded from the claim as a whole.

[0049] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, whether or not the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0050] In these examples, unless otherwise specified, the parts and percentages are by mass.

[0051] "Parts by mass" refers to the basic measurement unit representing the mass ratio relationship of multiple components. 1 part can represent any unit mass, such as 1 g or 2.689 g, etc. Suppose we say that the mass part of component A is a parts and the mass part of component B is b parts, then it represents the mass ratio of component A to component B as a:b. Or, it represents that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiple factor). It should not be misunderstood that, different from the number of mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0052] "And / or" is used to indicate that one or both of the stated circumstances may occur. For example, A and / or B includes (A and B) and (A or B).

[0053] To better illustrate the technical solutions provided in this application, before the examples, a general statement of the technical solutions is given as follows:

[0054] A binder for a solid-state battery, the binder for the solid-state battery comprising a first repeating unit, and the structural formula of the first repeating unit is as shown in Formula I:

[0055]

[0056] Wherein, R 1 comprises a hydrocarbon group; the hydrocarbon group in R 1 comprises an alkylene group, for example, it may be -CH 2 -;

[0057] R 2 comprises one of a carboxyl group, a siloxane epoxy group, a siloxy group, fluorine, and an alkyl group; the alkyl group in R 2 may be a C 1-6 alkyl group, for example, it may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl;

[0058] R 3 comprises a chemical bond, a hydrocarbon group or a phenyl group; the hydrocarbon group in R 3 comprises an alkylene group, for example, it may be -CH 2 -;

[0059] R' comprises an alkyl group, and the alkyl group in R' may be a C 1-6 alkyl group, for example, it may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, isohexyl, sec-hexyl, tert-hexyl.

[0060] The binder of the present application has hydrophobicity, can effectively prevent moisture from entering the battery interior, reduce the risk of short circuit and corrosion caused by moisture, and helps to improve the safety and stability of the battery.

[0061] According to an embodiment of the present application, the structural formula of the first repeating unit includes any one of the following structural formulas:

[0062] The present application also provides a method for preparing the binder for a solid-state battery as described above, comprising:

[0063] Reacting a resin with a halogenated alkane to obtain a binder for a solid-state battery, wherein the resin comprises a second repeating unit, the structural formula of the second repeating unit is as shown in Formula II, the structural formula of the halogenated alkane is as shown in Formula III, and X comprises chlorine or bromine;

[0064]

[0065] According to an embodiment of the present application, the reaction is carried out in the presence of a catalyst, and the catalyst includes sodium hydroxide, potassium hydroxide or concentrated sulfuric acid;

[0066] And / or, the reaction is carried out in the presence of an organic solvent, and the organic solvent includes any one of dimethylformamide and dimethyl sulfoxide; dimethylformamide is a high-boiling polar (hydrophilic) aprotic solvent that can promote the SN2 reaction; dimethyl sulfoxide has strong oxidizing properties. As an electrophilic reagent of the activating reagent, it first attacks the oxygen atom, which can reduce the activation energy required in the reaction process.

[0067] And / or, the molecular weight of the resin is 80,000 - 5,000,000;

[0068] For example, the molecular weight of the resin can be 80,000, 90,000, 100,000, 500,000, 1,000,000, 1,500,000, 2,000,000, 2,500,000, 3,000,000, 3,500,000, 4,000,000, 4,500,000, 5,000,000 or any value between 80,000 - 5,000,000.

[0069] And / or, the mass ratio of the resin to the compound of formula III is (70 - 99):(1 - 30), the catalyst accounts for 1 - 5 wt% of the resin, and the solid content of the reaction system before the reaction is 10 - 30%;

[0070] For example, the mass ratio of the resin to the compound of formula III can be 70:1, 70:30, 99:1, 99:30 or any value between (70 - 99):(1 - 30).

[0071] For example, the catalyst can account for 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or any value between 1 - 5 wt% of the resin.

[0072] For example, the solid content of the reaction system before the reaction can be 10%, 15%, 20%, 25%, 30% or any value between 10 - 30%.

[0073] And / or, the temperature of the reaction is 40 - 80 °C, and the time of the reaction is 24 - 72 h.

[0074] For example, the temperature of the reaction can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C or any value between 40 - 80 °C.

[0075] The time of the reaction can be 24 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, 72 h or any value between 24 - 72 h.

[0076] The present application also provides an electrolyte membrane, and the raw materials of the electrolyte membrane include the binder for solid-state batteries described above or the binder for solid-state batteries prepared by the method described above.

[0077] The present application also provides a method for preparing an electrolyte membrane, including:

[0078] Mixing the binder with a first solvent to obtain a coating solution, coating the coating solution on a base film, and performing a first drying treatment to form a protective layer on the base film;

[0079] Mixing the binder with a second solvent, a sulfide electrolyte, and a lithium salt to obtain a slurry, coating the slurry on one surface of the protective layer away from the base film, and performing a second drying treatment to form an electrolyte membrane on the base film;

[0080] Wherein, the binder includes the binder for solid-state batteries described above or the binder for solid-state batteries prepared by the method described above.

[0081] According to an embodiment of the present application, in the coating solution, the mass ratio of the binder to the first solvent is (1-5):(95-99);

[0082] For example, in the coating solution, the mass ratio of the binder to the first solvent can be 1:95, 1:99, 5:95, 5:99 or any value between (1-5):(95-99).

[0083] And / or, after mixing the binder with the first solvent, the method further includes: stirring at a temperature of 50-100°C for 12-24 h to obtain a coating solution; for example, the temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C or any value between 50-100°C, and the time can be 12 h, 15 h, 20 h, 24 h or any value between 12-24 h.

[0084] Furthermore, the stirring rate can be 300-1000 rpm. For example, the stirring rate can be 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, 1000 rpm or any value between 300-1000 rpm.

[0085] And / or, the first solvent includes at least one of dimethyl succinate, dimethyl glutarate, and dimethyl adipate;

[0086] And / or, the temperature of the first drying treatment is 60-200°C; for example, the temperature of the first drying treatment can be 60°C, 100°C, 150°C, 200°C or any value between 60-200°C.

[0087] And / or, the time of the first drying treatment is 6 - 12 h; for example, the time of the first drying treatment can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, or any value between 6 - 12 h.

[0088] After the first drying treatment, the first solvent in the coating solution can be removed, and a dense protective layer is formed on the base film.

[0089] During the application process of the electrolyte membrane, especially when the electrolyte membrane is transferred to the positive and negative electrode plates, the dense protective layer will be detached from the base film together with the electrolyte membrane. In this way, the surface that originally contacted the base film can have a dense protective layer to protect the sulfide electrolyte, playing a role in isolating moisture.

[0090] According to an embodiment of the present application, the coating amount of the coating solution on the base film is 0.01 - 3 mg / cm 2 .

[0091] For example, the coating amount of the coating solution on the base film can be 0.01 mg / cm 2 , 0.5 mg / cm 2 , 1 mg / cm 2 , 1.5 mg / cm 2 , 2 mg / cm 2 , 2.5 mg / cm 2 , 3 mg / cm 2 or any value between 0.01 - 3 mg / cm 2 .

[0092] According to an embodiment of the present application, in the slurry, the mass ratio of the binder to the sulfide electrolyte is (10 - 30):(70 - 90), the mass of the lithium salt is 40 - 70% of the mass of the binder, and the solid content of the slurry is 50 - 80%;

[0093] For example, in the slurry, the mass ratio of the binder to the sulfide electrolyte can be 10:70, 10:90, 30:70, 30:90, or any value between (10 - 30):(70 - 90).

[0094] For example, in the slurry, the mass of the lithium salt can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any value between 40 - 70% of the mass of the binder.

[0095] For example, the solid content of the slurry can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value between 50 - 80%.

[0096] And / or, the sulfide electrolyte includes Li 3PS 4 、Li 7 P 3 S 11 、80Li 2 S-20P 2 S 5 、Li 7-x PS 6-x Y x at least one of, wherein Y is Cl, Br or I, and x = 0 - 1.6;

[0097] and / or, the lithium salt includes at least one of LiTFSI, LiFSI, LiPF 6 、LiDFOB, LiBOB;

[0098] and / or, the second solvent includes at least one of acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[0099] Further, after mixing the binder with the second solvent, the sulfide electrolyte, and the lithium salt, the method further includes: stirring the mixed material at a rotation speed of 1000 - 2000 rpm for 4 - 6 h to obtain a slurry.

[0100] According to an embodiment of the present application, the second drying treatment includes: standing at room temperature for 0.4 - 0.6 h, and then drying at a temperature of 40 - 50 °C for 22 - 26 h.

[0101] Specifically, the second drying treatment can be: standing at room temperature for 0.5 h, and then drying at a temperature of 45 °C for 24 h.

[0102] After the second drying treatment, the second solvent in the slurry can be removed, and a layered structure is formed on the side of the protective layer away from the base film. This layered structure and the protective layer constitute the sulfide electrolyte membrane.

[0103] During the second drying treatment, due to the large mass and density of the electrolyte, the second solvent cannot drive the electrolyte to move. When the second solvent evaporates by heating, it can drive the binder to move away from the base film side. The binder that moves to the surface can protect the internal sulfide electrolyte, achieving the effect of isolating moisture from the sulfide electrolyte.

[0104] According to an embodiment of the present application, the thickness of the electrolyte membrane is 40 - 100 μm.

[0105] For example, the thickness of the electrolyte membrane can be 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any value between 40 - 100 μm.

[0106] The present application also provides a coating composition, which comprises the binder described above and the first solvent described above. Further, the mass ratio of the binder to the first solvent is (1 - 5):(95 - 99).

[0107] The present application also provides a protective layer, which comprises the binder described above.

[0108] The present application also provides a method for preparing a protective layer. Specifically, the method for preparing the protective layer includes: mixing the binder with the first solvent to obtain a coating solution, coating the coating solution on a base film, and performing a first drying treatment to form a protective layer on the base film.

[0109] The present application also provides a slurry, which comprises the binder described above, a second solvent, a sulfide electrolyte, and a lithium salt.

[0110] The present application also provides a solid-state battery, which comprises the electrolyte membrane described above or an electrolyte membrane prepared by the preparation method described above.

[0111] The embodiments of the present application will be described in detail below in conjunction with specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be construed as limiting the scope of the present application. For those conditions not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0112] The hydroxyl acrylic resin in Example 1 was purchased from Hanpin Paint Industry Shandong Co., Ltd., with a solid content of 65%, a viscosity of 9 - 10 s, a thermoplastic type, and a model of AH.

[0113] The hydroxyl fluorocarbon resin in Example 2 was purchased from Shanghai Zhuoyu Technology Co., Ltd., with a model of F828, a viscosity of 1000 s, a hydroxyl content of 2.2% (based on the solid content), and a fluorine content of ≥10% (based on the solid content).

[0114] I. Preparation of sulfide electrolyte membrane

[0115] Example 1

[0116] Example 1 provides a method for preparing a sulfide electrolyte membrane, which includes:

[0117] (1) Preparation of binder.

[0118]

[0119] Weigh 5 g of hydroxy acrylic resin with a molecular weight of 80,000, 0.0506 g of bromoethane, and 44.8994 g of dimethyl sulfoxide in a sealed flask. Then add 0.05 g of concentrated sulfuric acid and heat it at a constant temperature of 80 °C in an oil bath for 72 h. After separation and purification, a binder is obtained.

[0120] (2) Weigh 0.3 g of the binder and 9.7 g of dimethyl succinate, mix them at a speed of 1000 rpm for 6 h to obtain a coating solution. Spray the coating solution evenly on the base film, and the coating amount of the coating solution on the base film is 2 mg / cm 2 , dry it at 100 °C for 12 h to form a protective layer on the base film.

[0121] (3) According to the mass ratio of binder: sulfide electrolyte Li 6 PS 5 Cl is 20:80, and lithium salt LiFSI is 50 wt% of the binder content, with a solid content of 56 wt%. Weigh the binder prepared in step (1), the second solvent (methyl ethyl ketone), the sulfide electrolyte (Li 6 PS 5 Cl), and the lithium salt (LiFSI), where the mass of the sulfide electrolyte Li 6 PS 5 Cl is 5 g, and the other components are weighed according to the ratio. Then homogenize it at a speed of 1000 rpm for 5 h to obtain a slurry. Then coat the slurry on the surface of the protective layer away from the base film in an air atmosphere, air dry it for 0.5 h, and then dry it at 45 °C for 24 h to obtain an electrolyte membrane with a thickness of 70 μm.

[0122] Example 2

[0123] Refer to the method of Example 1 to prepare the electrolyte membrane. Other steps are the same as those in Example 1, except that: in Example 2, the hydroxy acrylic resin in Example 1 is replaced with hydroxy fluorocarbon resin. The hydroxy fluorocarbon resin used in Example 2 contains a second repeating unit, and the structural formula of the second repeating unit is The molecular weight of the hydroxy fluorocarbon resin is 1 million. In Example 2, the binder contains a first repeating unit, and the structural formula of the first repeating unit is

[0124] Example 3

[0125] Refer to the method of Example 1 to prepare the electrolyte membrane. Other steps are the same as those in Example 1, except that: in step (1) of Example 3, the mass of bromoethane is 0.5 g.

[0126] Example 4

[0127] Prepare the electrolyte membrane according to the method of Example 1, and the other steps are the same as those of Example 1, except that: in step (3) of Example 4, the mass ratio of the binder to the sulfide electrolyte Li 6 PS 5 and Cl is 30:80.

[0128] Example 5

[0129] Prepare the electrolyte membrane according to the method of Example 3, and the other steps are the same as those of Example 3, except that: in step (2) of Example 5, the coating amount of the coating solution on the base film is 3 mg / cm 2 .

[0130] Example 6

[0131] Prepare the electrolyte membrane according to the method of Example 1, and the other steps are the same as those of Example 1, except that: in step (3) of Example 6, the lithium salt LiFSI is 70 wt% of the binder content.

[0132] Comparative Example 1

[0133] Comparative Example 1 omitted step (1), and directly used hydroxy acrylic resin as the binder in Comparative Example 1, and the other steps were the same as those of Example 1.

[0134] Comparative Example 2

[0135] Comparative Example 2 omitted step (2), and did not treat the base film in Comparative Example 2, and the other steps were the same as those of Example 1.

[0136] II. Performance Test

[0137] Perform performance tests on the electrolyte membranes prepared in the examples and comparative examples, and the specific test methods are as follows.

[0138] Test for the moisture of the electrolyte membrane: Place the electrolyte membranes prepared in the examples and comparative examples in an experimental environment with a dew point of -45 °C, and test their moisture after standing for 0 h, 6 h, 12 h, and 24 h respectively to obtain the moisture values H1, H2, H3, and H4.

[0139] Test for the ionic conductivity of the electrolyte membrane: Cut the obtained sulfide electrolyte membrane into small round pieces with a diameter of 10 mm, put them into a solid-state battery mold with a diameter of 10 mm, press them under a pressure of 500 MPa for 5 min, and then tighten them with a torque wrench of 20 N·m. Perform EIS test using an electrochemistry workstation of Metrohm, with an amplitude of 5 mV and a frequency of 0.01 - 10 7 Hz. Obtain the R value according to the test results, measure the thickness of the electrolyte membrane to obtain the L value, and calculate the S value by calculating the area of the small round piece. Calculate the ionic conductivity of the electrolyte membrane according to the formula, where the formula for the ionic conductivity is б = L / (RS).

[0140] Evaluation of the influence of the electrolyte membrane on electrical properties:

[0141] Mold assembly and electrical property testing: The obtained electrolyte membrane was cut into small round pieces with a diameter of 10 mm and placed into a 10 mm diameter all-solid-state battery mold. Then, a positive electrode sheet was added at one end, and it was pressed twice under 2.5 T. Then, an In sheet with a diameter of 10 mm and a lithium sheet with a diameter of 10 mm were added and sealed. Then, a mold holder was tightened with a 3.5 N torque wrench. The positive electrode is NCM811:Li 6 PS 5 Cl:PVDF:VGCF = 75:20:2:3 was prepared by a wet process, and the active surface loading was 21 mg / cm 2 .

[0142] The assembled mold battery was placed in a 45 °C constant temperature oven and left standing for 12 h. Then, the positive electrode was subjected to a 0.05 C charge-discharge test in the voltage range of 2.1 - 3.7 V, and the theoretical specific capacity is 190 mAh.g -1 .

[0143] The test results are shown in Tables 1 and 2 below.

[0144] Table 1 Water content of the samples at different storage times under -45 °C

[0145] Sample H1 (ppm) H2 (ppm) H3 (ppm) H4 (ppm) Example 1 109 118 131 146 Example 2 503 749 1305 2473 Example 3 30 45 51 56 Example 4 60 68 81 86 Example 5 63 71 73 80 Example 6 116 134 147 164 Comparative Example 1 33689 40981 60082 85927 Comparative Example 2 5009 6023 8065 10735

[0146] From the comparison between Examples 1 - 6 and Comparative Examples 1 - 2 in Table 1, it can be seen that the hydrophobic ability of the electrolyte membranes in Examples 1 - 6 is significantly better than that in Comparative Examples 1 - 2. By using the binder combination base film treatment process prepared in this application, the hydrophobic ability of the electrolyte membrane can be significantly enhanced. Whether it is the electrolyte membrane directly coated in the air or the obtained electrolyte membrane placed in a water-containing atmosphere, the electrolyte membranes in the examples all show excellent hydrophobic ability. This is mainly because in the examples, the hydrophilic hydroxyl groups in the original binder are reacted into hydrophobic ether bonds through an etherification reaction, and the combination of the process treatment enables a dense hydrophobic layer on the exposed surface of the electrolyte membrane, thus isolating water from contacting with the sulfide electrolyte. By comparing Example 1 and Comparative Example 1, it can be seen that the binder prepared in this application has hydrophobicity and can improve the hydrophobic effect of the electrolyte membrane. By comparing Example 1 and Comparative Example 2, it can be seen that the treatment of the base film can ensure the hydrophobic ability during the use of the electrolyte membrane.

[0147] Table 2 Ion conductivity and electrical property table of the sulfide electrolyte membrane

[0148]

[0149]

[0150] In order to endow the electrolyte membrane with a sufficiently strong hydrophobic ability, an excessive amount of binder compared to the normal situation is used in the process of preparing the electrolyte membrane. As can be seen from Table 2, the electrolyte membranes prepared in Examples 1-6 still have a relatively high ionic conductivity, which is sufficient to support the active material for high-rate charge and discharge. This is mainly because the binder prepared in this application combines with the lithium salt, and the complexation and dissociation of the ether bond with lithium ions can achieve the transport of lithium ions, which is significantly better than the conventional binder. From the performance of the electrolyte membrane in the positive half-cell, it can also be seen that the electrolyte membranes prepared in Examples 1-6 can all perform normal charge and discharge, and Examples 1, 3, and 6 exhibit better rate performance. In Comparative Example 1, since the binder contains a large number of hydrophilic functional groups - hydroxyl groups, the absorbed moisture will affect the sulfide electrolyte and cause its structure to decompose, and finally it cannot perform normal charge and discharge when applied in the battery.

[0151] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0152] In addition, those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the claims above, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present application, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art.

Claims

1. A binder for solid-state batteries, characterized in that: The binder for solid-state batteries comprises a first repeating unit, and the structural formula of the first repeating unit is shown in Formula I: Wherein, R1 comprises a hydrocarbon group; R2 includes one of carboxyl, siloxy epoxy, siloxy, epoxy, fluorine, and alkyl; R3 includes a chemical bond, a hydrocarbon group or a phenyl group; R' includes an alkyl group.

2. The binder for solid-state batteries according to claim 1, characterized in that: The structural formula of the first repeating unit includes any one of the following structural formulas:

3. A method for preparing a binder for solid-state batteries as claimed in claim 1 or 2, characterized in that: include: Resin is reacted with halogenated alkanes to obtain a binder for solid-state batteries; Wherein, the resin comprises a second repeating unit, the structural formula of the second repeating unit is shown in Formula II, the structural formula of the halogenated alkane is shown in Formula III, and X comprises chlorine or bromine; 4. The method according to claim 3, characterized in that The reaction is carried out in the presence of a catalyst, which includes sodium hydroxide, potassium hydroxide or concentrated sulfuric acid; And / or, the reaction is carried out in the presence of an organic solvent, wherein the organic solvent comprises any one of dimethylformamide and dimethyl sulfoxide; And / or, the molecular weight of the resin is 80,000-5,000,000; And / or, the mass ratio of the resin to the compound of formula III is (70-99): (1-30), the catalyst accounts for 1-5wt% of the resin, and the solid content of the reaction system before the reaction is 10-30%; And / or, the reaction temperature is 40-80° C., and the reaction time is 24-72 h.

5. An electrolyte membrane, characterized in that: The raw material of the electrolyte membrane includes the binder for solid-state batteries according to claim 1 or 2, or includes the binder for solid-state batteries prepared by the method according to claim 3 or 4.

6. A method for preparing an electrolyte membrane, characterized in that: include: Mixing a binder with a first solvent to obtain a coating liquid, coating the coating liquid on a base film, and performing a first drying process to form a protective layer on the base film; Mixing a binder with a second solvent, a sulfide electrolyte, and a lithium salt to obtain a slurry, coating the slurry on a surface of the protective layer away from the base film, and performing a second drying process to form an electrolyte membrane on the base film; Wherein, the binder includes the binder for solid-state batteries described in claim 1 or 2, or includes the binder for solid-state batteries prepared by the method described in claim 3 or 4.

7. The method for preparing an electrolyte membrane according to claim 6, characterized in that: In the coating liquid, the mass ratio of the binder to the first solvent is (1-5): (95-99); And / or, after mixing the binder with the first solvent, the method further comprises: stirring at a temperature of 50-100° C. for 12-24 hours to obtain a coating solution; And / or, the first solvent includes at least one of dimethyl succinate, dimethyl glutarate, and dimethyl adipate; And / or, the temperature of the first drying treatment is 60-200°C; And / or, the first drying treatment time is 6-12h; And / or, the coating amount of the coating liquid on the base film is 0.01-3 mg / cm 2 .

8. The preparation method according to claim 6, characterized in that: In the slurry, the mass ratio of the binder to the sulfide electrolyte is (10-30): (70-90), the mass of the lithium salt is 40-70% of the mass of the binder, and the solid content of the slurry is 50-80%; And / or, the sulfide electrolyte includes Li3PS4, Li7P3S 11 、80Li2S-20P2S5、Li 7-x PS 6-x Y x At least one of the following, wherein Y is Cl, Br or I, and x=0-1.6; And / or, the lithium salt includes at least one of LiTFSI, LiFSI, LiPF6, LiDFOB, and LiBOB; And / or, the second solvent includes at least one of acetone, methyl ethyl ketone, and methyl isobutyl ketone; And / or, the second drying treatment includes: standing at room temperature for 0.4 to 0.6 hours, and then drying at a temperature of 40 to 50° C. for 22 to 26 hours.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The thickness of the electrolyte membrane is 40-100 μm.

10. A solid-state battery, characterized in that: The solid-state battery comprises the electrolyte membrane according to claim 5 or the electrolyte membrane prepared by the preparation method according to any one of claims 6 to 9.

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