Terpolymers, processes for their preparation and use

Abstract

The application provides a terpolymer and a preparation method and application thereof, and particularly relates to the technical field of lithium batteries. The terpolymer is mainly formed by copolymerization of a diene and an unsaturated alkoxysilane to form a main chain, and then formed by introducing a mercapto group through a dithiol compound click reaction; wherein the unsaturated alkoxysilane contains a carbon-carbon double bond and a siloxyl group. The molecular main chain of the terpolymer is composed of flexible diene units, which endows the copolymer with a good elastic skeleton structure. In the polymerization process, the unsaturated alkoxysilane is introduced as a functional monomer, so that a siloxyl group is formed on the side chain of the copolymer. Subsequently, the dithiol compound is used to further introduce a mercapto group (-SH) by undergoing an addition reaction with the carbon-carbon double bond in the main chain. The finally obtained terpolymer has a flexible main chain structure, and the side chain contains a siloxyl group and a mercapto group at the same time, and has good elasticity and functional characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a terpolymer and a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand for high energy density and high safety batteries in new energy vehicles and energy storage systems, all-solid-state lithium batteries have shown significant advantages in improving battery safety and energy density due to the use of non-flammable solid electrolytes, and have become an important development direction of next-generation battery technology.

[0003] Silicon has a theoretical specific capacity of about 4200 mAh / g, about 10 times that of graphite negative electrode, which can significantly improve the energy density of the battery, and becomes an ideal negative electrode candidate material in sulfide all-solid-state batteries. However, there are two main challenges in the practical application of silicon negative electrode:

[0004] Poor structural stability: Silicon will undergo severe volume expansion (>300%) during charging and discharging, leading to particle cracking and pulverization, and thus destroying the structural integrity of the electrode;

[0005] Interface contact failure: Sulfide electrolyte is a rigid particle, and silicon volume expansion is easy to form micron-level gaps at the electrode / electrolyte interface, blocking the lithium ion transport channel and significantly increasing the interface impedance.

[0006] In addition, traditional binders such as PVDF or CMC and SBR system usually rely on polar solvents (such as NMP or water) for dissolution and coating, and these polar solvents are easy to react with sulfide electrolyte, leading to electrolyte degradation, which limits its application in sulfide all-solid-state batteries.

[0007] Therefore, developing a new type of binder material suitable for sulfide solid-state battery system to improve the structural stability and interface compatibility of silicon negative electrode has become one of the key directions of current research.

[0008] Therefore, the present application is proposed. SUMMARY

[0009] The present application aims to provide a terpolymer and a preparation method and application thereof, which aims to solve at least one of the above technical problems in the prior art.

[0010] In order to achieve the above purpose of the present application, the following technical solutions are adopted:

[0011] The first aspect of the present application provides a terpolymer mainly formed by copolymerizing diene and unsaturated alkoxysilane to form a main chain, and then introducing thiol groups through click reaction of dithiol compound.

[0012] The unsaturated alkoxysilane contains carbon-carbon double bonds and siloxy groups.

[0013] Furthermore, the diene contains 3 to 8 carbon atoms.

[0014] Preferably, the diene includes at least one selected from propadiene, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene.

[0015] Furthermore, the dithiol compound includes at least one of 1,2-ethanedithiol, 1,6-hexanedithiol, polyethylene glycol dithiol, or 1,4-butanedithiol.

[0016] Preferably, the unsaturated alkoxysilane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane.

[0017] Furthermore, the molar ratio of the diene to the unsaturated alkoxysilane is (28~32):(1.1~2).

[0018] A second aspect of the present invention provides a method for preparing the aforementioned terpolymer, comprising the following steps:

[0019] A. Add unsaturated alkoxysilane, deionized water and emulsifier to the reactor and stir until homogeneous. Under inert gas protection, add diene and initiator to carry out the first polymerization reaction.

[0020] B. After the first polymerization reaction is completed, an acid solution is added to the system to break the emulsion, filter, wash, and perform a first drying to obtain the first polymer;

[0021] C. The first polymer, photoinitiator, and dithiol compound are added to an organic solvent to carry out a second polymerization reaction to obtain the terpolymer.

[0022] Furthermore, the emulsifier includes sodium dodecyl sulfate and / or sodium dodecylbenzene sulfonate.

[0023] Preferably, the amount of emulsifier added is 0.05 to 0.15 times the mass of the unsaturated alkoxysilane.

[0024] Preferably, the amount of deionized water used is 10 to 20 times the mass of the unsaturated alkoxysilane.

[0025] Preferably, the initiator is a sulfate initiator.

[0026] Preferably, the sulfate initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0027] Preferably, the amount of the initiator added is 0.04 to 0.06 times the mass of the unsaturated alkoxysilane.

[0028] Preferably, the photoinitiator comprises benzophenone and / or 2,4-dihydroxybenzophenone.

[0029] Preferably, the amount of photoinitiator is 0.05 to 0.12 times the mass of the first polymer.

[0030] Preferably, the amount of the dithiol compound is 0.5 to 1.5 times the mass of the first polymer.

[0031] Preferably, in step C, the organic solvent includes at least one of toluene, p-xylene, dichloromethane, and dibromomethane.

[0032] Furthermore, the temperature of the first polymerization reaction is 40~60℃.

[0033] Preferably, in step B, the acid solution is a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution.

[0034] Preferably, in step B, the concentration of the acid solution is 5-10 wt%.

[0035] Preferably, in step B, the first drying is vacuum drying.

[0036] Preferably, the vacuum drying temperature is 50~70℃ and the time is 18~32h.

[0037] Furthermore, the second polymerization reaction is carried out under ultraviolet light irradiation.

[0038] Preferably, the power of the ultraviolet light is 0.5~1.5kw, and the irradiation time is 10~30min.

[0039] Preferably, the preparation method further includes filtration after the second polymerization reaction and a second drying process to obtain the terpolymer.

[0040] Preferably, the second drying is vacuum drying.

[0041] Preferably, the vacuum drying temperature is 50~70℃.

[0042] A third aspect of the present invention provides the application of the terpolymer in a silicon anode binder for lithium batteries.

[0043] Furthermore, the lithium battery includes a sulfide all-solid-state lithium-ion battery.

[0044] Compared with the prior art, the present invention has at least the following beneficial effects:

[0045] The ternary copolymer provided by this invention has a main molecular chain composed of flexible diene units, giving the copolymer a good elastic backbone structure. During the polymerization process, unsaturated alkoxysilanes are introduced as functional monomers, forming siloxy groups on the copolymer side chains. Subsequently, a dithiol compound is used to undergo an addition reaction with the carbon-carbon double bonds in the main chain, further introducing thiol groups (-SH). The final ternary copolymer has a flexible main chain structure, and the side chains contain both siloxy groups and thiol groups, exhibiting both good elasticity and functionalization properties.

[0046] The preparation method provided by this invention first employs emulsion polymerization with diene and unsaturated alkoxysilane as comonomers, constructing a reaction system under the action of an emulsifier and an initiator to obtain a first polymer. Subsequently, functionalization is achieved through a mercapto-olefin click reaction, introducing thiol groups to obtain the target product. This preparation method features continuous process steps, is easy to control, and is suitable for large-scale industrial production.

[0047] This invention utilizes a ternary copolymer as a binder for the silicon anode. The flexible segments of this ternary copolymer effectively buffer the volume changes of the silicon anode during charge and discharge. Simultaneously, the bifunctional groups form stable interfacial connections with both the silicon anode and the sulfide electrolyte, synergistically maintaining tight contact and structural integrity at the electrode / electrolyte interface. Furthermore, the highly elastic network constructed from the flexible long chains helps disperse the volumetric stress of the silicon particles, suppressing the initiation and propagation of internal cracks in the electrode, thereby improving the cycle stability and structural reliability of the electrode. Attached Figure Description

[0048] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0049] Figure 1 This is an in-situ optical test photograph of the all-solid-state lithium battery prepared using the binder in Example 2 after completing 400 charge-discharge cycles;

[0050] Figure 2 This is an in-situ optical test photograph of the all-solid-state lithium battery prepared using the binder in Comparative Example 4 after 400 charge-discharge cycles. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0052] In the following, the terms “comprising,” “having,” and their cognates, which may be used in various embodiments of the invention, are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0053] The first aspect of the present invention provides a terpolymer mainly composed of a diene and an unsaturated alkoxysilane copolymerized to form a main chain, and then a thiol group is introduced by a click reaction of a dithiol compound.

[0054] The unsaturated alkoxysilane contains carbon-carbon double bonds and siloxy groups.

[0055] The ternary copolymer provided by this invention has a main molecular chain composed of flexible diene units, giving the copolymer a good elastic backbone structure. During the polymerization process, unsaturated alkoxysilanes are introduced as functional monomers, forming siloxy groups on the copolymer side chains. Subsequently, a dithiol compound is used to undergo an addition reaction with the carbon-carbon double bonds in the main chain, further introducing thiol groups (-SH). The final ternary copolymer has a flexible main chain structure, and the side chains contain both siloxy groups and thiol groups, exhibiting both good elasticity and functionalization properties.

[0056] Furthermore, the diene contains 3 to 8 carbon atoms.

[0057] And / or, the diene includes at least one of propylene, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene.

[0058] Furthermore, the dithiol compound includes at least one of 1,2-ethanedithiol, 1,6-hexanedithiol, polyethylene glycol dithiol, or 1,4-butanedithiol.

[0059] And / or, the unsaturated alkoxysilane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane.

[0060] Furthermore, the molar ratio of the diene to the unsaturated alkoxysilane is (28~32):(1.1~2).

[0061] Typical, but not limiting, molar ratios of diene and unsaturated alkoxysilane can be, for example, 28:1.1, 29:1.3, 30:1.5, 31:1.8 or 32:2, or any combination of proportions within the range of (28 to 32): (1.1 to 2).

[0062] A second aspect of the present invention provides a method for preparing the aforementioned terpolymer, comprising the following steps:

[0063] A. Add unsaturated alkoxysilane, deionized water and emulsifier to the reactor and stir until homogeneous. Under inert gas protection, add diene and initiator to carry out the first polymerization reaction.

[0064] B. After the first polymerization reaction is completed, an acid solution is added to the system to break the emulsion, filter, wash, and perform a first drying to obtain the first polymer;

[0065] C. The first polymer, photoinitiator, and dithiol compound are added to an organic solvent to carry out a second polymerization reaction to obtain the terpolymer.

[0066] The preparation method provided by this invention first employs emulsion polymerization with diene and unsaturated alkoxysilane as comonomers, constructing a reaction system under the action of an emulsifier and an initiator to obtain a first polymer. Subsequently, functionalization is achieved through a mercapto-olefin click reaction, introducing thiol groups to obtain the target product. This preparation method features continuous process steps, is easy to control, and is suitable for large-scale industrial production. Further, the emulsifier includes sodium dodecyl sulfate and / or sodium dodecylbenzenesulfonate.

[0067] And / or, the amount of the emulsifier added is 0.05 to 0.15 times the mass of the unsaturated alkoxysilane.

[0068] Typically, but not limitingly, the amount of emulsifier added is 0.05, 0.08, 0.1, 0.12, or 0.15 times the mass of the unsaturated alkoxysilane, or any value in the range of 0.05 to 0.15 times.

[0069] And / or, the amount of deionized water used is 10 to 20 times the mass of the unsaturated alkoxysilane.

[0070] Typically, but not limitingly, the amount of deionized water used can be 10, 12, 14, 16, 18, or 20 times the mass of the unsaturated alkoxysilane, or any value within the range of 10 to 20 times.

[0071] And / or, the initiator is a sulfate initiator.

[0072] And / or, the sulfate initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0073] And / or, the amount of the initiator added is 0.04 to 0.06 times the mass of the unsaturated alkoxysilane.

[0074] Typically, but not limitingly, the amount of initiator added is 0.04, 0.045, 0.05, 0.055, or 0.06 times the mass of the unsaturated alkoxysilane, or any value in the range of 0.04 to 0.06 times.

[0075] And / or, the photoinitiator includes benzophenone and / or 2,4-dihydroxybenzophenone.

[0076] And / or, the amount of the photoinitiator is 0.05 to 0.12 times the mass of the first polymer.

[0077] Typically, but not limitingly, the amount of photoinitiator used is 0.05, 0.06, 0.08, 0.1, or 0.12 times the mass of the dithiol compound, or any value in the range of 0.05 to 0.12 times.

[0078] Preferably, the amount of the dithiol compound is 0.5 to 1.5 times the mass of the first polymer.

[0079] And / or, in step C, the organic solvent includes at least one of toluene, p-xylene, dichloromethane, and dibromomethane. It should be noted that the organic solvent here is a non-polar solvent.

[0080] Furthermore, the temperature of the first polymerization reaction is 40~60℃.

[0081] Typically, but not limitingly, the temperature of the first polymerization reaction can be, for example, 40°C, 45°C, 50°C, 55°C, or 60°C, or any value in the range of 40°C to 60°C.

[0082] And / or, in step B, the acid solution is a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution.

[0083] And / or, in step B, the concentration of the acid solution is 5~10wt%.

[0084] And / or, in step B, the first drying is vacuum drying.

[0085] And / or, the vacuum drying temperature is 50~70℃ and the time is 18~32h.

[0086] Typically, but not limitingly, the vacuum drying temperature can be, for example, 50°C, 55°C, 60°C, 65°C, or 70°C, and the time can be, for example, 18h, 20h, 24h, 28h, or 32h, or any combination thereof.

[0087] Furthermore, the second polymerization reaction is carried out under ultraviolet light irradiation.

[0088] And / or, the power of the ultraviolet light is 0.5~1.5kw, and the irradiation time is 10~30min.

[0089] Typically, but not limitingly, the power of the ultraviolet light can be, for example, 0.5 kW, 0.8 kW, 1.0 kW, 1.2 kW or 1.5 kW, and the irradiation duration can be, for example, 10 min, 15 min, 20 min, 25 min or 30 min, or any combination of the above ranges.

[0090] And / or, the preparation method further includes filtration after the second polymerization reaction and a second drying process to obtain the terpolymer.

[0091] And / or, the second drying is vacuum drying.

[0092] And / or, the vacuum drying temperature is 50~70℃.

[0093] Typical, but not limiting, vacuum drying temperatures can be, for example, 50°C, 55°C, 60°C, 65°C, or 70°C.

[0094] A third aspect of the present invention provides the application of the terpolymer in a silicon anode binder for lithium batteries.

[0095] This invention utilizes a ternary copolymer as a binder for silicon anodes. The flexible segments of this copolymer effectively buffer the volume changes of the silicon anode during charge and discharge. Simultaneously, bifunctional groups form stable interfacial connections with both the silicon anode and the sulfide electrolyte, synergistically maintaining tight contact and structural integrity at the electrode / electrolyte interface. Specifically, the siloxy groups on the side chains hydrolyze and undergo a condensation reaction with the hydroxyl groups on the silicon anode surface, forming stable Si–O–Si covalent bonds, thus effectively anchoring the silicon anode. Thiol groups form SS bonds with the sulfur groups in the sulfide electrolyte, enhancing the interaction between the binder and the sulfide electrolyte. The highly elastic network constructed by the flexible long chains helps disperse the volumetric stress of the silicon particles, inhibiting the initiation and propagation of internal cracks in the electrode, thereby improving the cycle stability and structural reliability of the electrode.

[0096] Meanwhile, this invention effectively overcomes the limitations of traditional binders in terms of solvent compatibility. Conventional binder systems, such as polyvinylidene fluoride (PVDF), typically rely on strongly polar solvents for dissolution and coating. These polar solvents are prone to side reactions with sulfide solid electrolytes, leading to electrolyte structure damage and battery performance degradation. In contrast, the ternary copolymer used in this invention is soluble in non-polar solvents, avoiding direct contact and chemical reactions with sulfide electrolytes from the outset, significantly improving the chemical stability and interfacial compatibility of the lithium battery system.

[0097] Furthermore, the lithium battery includes a sulfide all-solid-state lithium-ion battery.

[0098] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0099] Example 1

[0100] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0101] 1. Add 200g of deionized water, 10g of vinyltrimethoxysilane, and 1g of sodium dodecyl sulfate to a reactor equipped with a stirrer, thermometer, and gas inlet. Evacuate the reactor three times to purge the butadiene gas. Then raise the temperature to 60°C, maintain the butadiene pressure at 0.3MPa, and introduce 0.5g of potassium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. Stop the reaction when 90g of butadiene has been introduced. Cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and vacuum dry the resulting polymer at 60°C for 24 hours to obtain the first polymer.

[0102] 2. Take 5g of the first polymer, 0.5g of benzophenone, and 5g of 1,2-ethanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0103] Example 2

[0104] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0105] 1. Add 200g of deionized water, 15g of vinyltrimethoxysilane, and 1.3g of sodium dodecylbenzenesulfonate to a reactor equipped with a stirrer, thermometer, and gas inlet. Evacuate the reactor three times to purge the butadiene gas, then raise the temperature to 60°C, maintain the butadiene pressure at 0.3 MPa, and introduce 0.7g of ammonium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. Stop the reaction when the mass of butadiene introduced reaches 88.5g. Cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and vacuum dry the obtained polymer at 60°C for 24 hours to obtain the first polymer.

[0106] 2. Take 4g of the first polymer, 0.5g of benzophenone, and 5g of 1,6-hexanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0107] Example 3

[0108] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0109] 1. Add 200g of deionized water, 12g of vinyltrimethoxysilane, and 1g of sodium dodecyl sulfate to a reactor equipped with a stirrer, thermometer, and gas inlet. Evacuate the reactor three times to purge the butadiene gas. Then raise the temperature to 60°C, maintain the butadiene pressure at 0.3 MPa, and introduce 0.5g of sodium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. When the mass of butadiene introduced reaches 88g, stop the reaction, cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and dry the resulting polymer under vacuum at 60°C for 24 hours to obtain the first polymer.

[0110] 2. Take 5g of the first polymer, 0.4g of 2,4-dihydroxybenzophenone, and 5g of polyethylene glycol dithiol (average molecular weight 1,000) and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0111] Example 4

[0112] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0113] 1. Add 200g of deionized water, 14g of vinyltrimethoxysilane, and 0.86g of sodium dodecyl sulfate to a reactor equipped with a stirrer, thermometer, and gas inlet. Vacuum the reactor three times to purge the butadiene gas, then raise the temperature to 60°C, maintain the butadiene pressure at 0.3 MPa, and introduce 0.5g of ammonium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. Stop the reaction when 86g of butadiene has been introduced, cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and vacuum dry the resulting polymer at 60°C for 24 hours to obtain the first polymer.

[0114] 2. Take 5g of the first polymer, 0.5g of benzophenone, and 5g of 1,4-butanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0115] Example 5

[0116] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0117] 1. Add 200g of deionized water, 19.25g of vinyltriethoxysilane, and 1.3g of sodium dodecylbenzenesulfonate to a reactor equipped with a stirrer, thermometer, and gas inlet. Evacuate the reactor three times to purge the propadiene gas. Then raise the temperature to 60°C, maintain the propadiene pressure at 0.3 MPa, and introduce 0.7g of ammonium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. When the mass of propadiene introduced reaches 65.2g, stop the reaction, cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and dry the resulting polymer under vacuum at 60°C for 24 hours to obtain the first polymer.

[0118] 2. Take 4g of the first polymer, 0.5g of benzophenone, and 5g of 1,4-butanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0119] Example 6

[0120] This embodiment provides a terpolymer, the preparation process of which is as follows:

[0121] 1. Add 200g of deionized water, 15g of vinyltrimethoxysilane, and 1.3g of sodium dodecylbenzenesulfonate to a reactor equipped with a stirrer, thermometer, and gas inlet. Purge the reactor with nitrogen three times, then raise the temperature to 60°C. Slowly add 110.8g of 1,4-pentadiene and inject 0.7g of ammonium persulfate initiator (dissolved in 10g of water) to begin the polymerization reaction. Slowly add 1,4-pentadiene, and stop the reaction half an hour after the addition is complete. Cool to room temperature, add 10wt% nitric acid aqueous solution to demulsify, filter, wash the precipitate several times with deionized water, and dry the obtained polymer under vacuum at 60°C for 24 hours to obtain the first polymer.

[0122] 2. Take 4g of the first polymer, 0.5g of benzophenone, and 5g of 1,2-ethanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the terpolymer.

[0123] Example 7

[0124] This embodiment provides a terpolymer, which differs from Example 2 in that the mass of vinyltrimethoxysilane is 8.15g. The other raw materials and preparation methods are the same as in Example 2, and will not be repeated here.

[0125] Example 8

[0126] This embodiment provides a terpolymer, which differs from Example 2 in that the mass of vinyltrimethoxysilane is 16.89g. The other raw materials and preparation methods are the same as in Example 2, and will not be repeated here.

[0127] Comparative Example 1

[0128] This comparative example provides a binary copolymer, the preparation process of which is as follows:

[0129] 1. In a reactor equipped with a stirrer, thermometer, and gas inlet, butadiene gas was evacuated and replaced three times. Then, the temperature was raised to 60°C, and the butadiene pressure was maintained at 0.3 MPa. 0.7 g of ammonium persulfate initiator (dissolved in 10 g of water) was introduced to start the polymerization reaction. When the mass of butadiene introduced was 88.5 g, the reaction was stopped. The mixture was cooled to room temperature, and 10 wt% nitric acid aqueous solution was added to break the emulsion. The mixture was filtered, and the precipitate was washed several times with deionized water. The obtained polymer was vacuum dried at 60°C for 24 hours to obtain the first polymer.

[0130] 2. Take 4g of the first polymer, 0.5g of benzophenone, and 5g of 1,2-ethanedithiol and dissolve them in 100g of toluene solution. Irradiate the solution with a 1kW high-pressure mercury lamp as the ultraviolet light source for 20 minutes. After filtering the solution, dry it under vacuum at 60℃ to obtain the binary copolymer.

[0131] Comparative Example 2

[0132] This comparative example provides a binary copolymer, which differs from Example 2 in that step 2 is omitted, and the resulting first polymer is a binary copolymer.

[0133] Comparative Example 3

[0134] This comparative example provides an adhesive made of styrene-butadiene rubber, which is commercially available.

[0135] Comparative Example 4

[0136] This comparative example provides an adhesive made of ethyl cellulose, which is commercially available.

[0137] Test Example 1

[0138] The substances obtained in the examples and comparative examples were used as adhesives for bonding ability testing. Peel strength was used to reflect the bonding ability.

[0139] Peel strength test method: Dissolve the adhesive in toluene, and add silicon, sulfide solid electrolyte, adhesive and conductive agent in a ratio of 50:40:5:5 to form a slurry. Coat the slurry with copper foil and vacuum dry at 80℃. Cut a strip sample with a length of 400mm and a width of 10mm. Place a strip of transparent tape of a certain width horizontally on the bottom and end face of an ungraded steel ruler. Then attach double-sided tape to the transparent tape with the same length as the width of the transparent tape and centered. Finally, attach the test sample to the double-sided tape with the end face flush. Roll the sample freely back and forth on the electrode surface more than 3 times. Fold the unattached end of the electrode of the test sample 180 degrees and clamp it on the upper clamp of the tensile testing machine. Peel the electrode at a tensile speed of 100mm / min. Read the peel strength test results and record them in Table 1.

[0140] Table 1

[0141]

[0142] Test Example 2

[0143] All-solid-state lithium batteries were prepared according to the following method:

[0144] (1) Positive electrode: Aluminum foil with a diameter of 10 mm and a thickness of 12 μm is used as the positive electrode current collector. Cis-butadiene rubber (as binder) is dissolved in toluene and a slurry is formed by mixing ternary positive electrode: binder: LGPS electrolyte: conductive agent 78:2:1.9:0.1 with toluene as solvent. The slurry is coated on the aluminum foil and vacuum dried at 80 °C.

[0145] (2) Negative electrode: A copper foil with a diameter of 10 mm and a thickness of 12 μm is used as the negative electrode current collector; the copolymer obtained in the examples and comparative examples (as a binder) is dissolved in toluene, and carbon, sulfide solid electrolyte, binder and conductive agent are added in a ratio of 50:40:5:5 to form a slurry, which is coated on the copper foil and then vacuum dried at 80°C to form the slurry.

[0146] (3) Electrolyte: Li6PS5Cl powder (D50=5μm, ionic conductivity 10.32 mS / cm) and PVDF binder are mixed in toluene at a ratio of 98:2 to form a slurry, which is then directly coated onto the negative electrode and vacuum dried at 80℃ to form the slurry.

[0147] The negative electrode and positive electrode coated with electrolyte are placed in a pressure battery mold with an inner diameter of 10 mm and pressed into a sheet at 100 MPa for 2 minutes on a tablet press.

[0148] The all-solid-state lithium battery prepared above was subjected to electrical performance testing at a stacking voltage of 20 mPa, specifically including charge and discharge capacity testing at a rate of 0.2C, and the data are recorded in Table 2.

[0149] Table 2

[0150]

[0151] As can be seen from Table 2, the capacity retention rate of the examples is generally better than that of the comparative examples, proving that the synthesized bifunctional groups of the binder contribute to capacity retention.

[0152] Test Example 3

[0153] The all-solid-state lithium batteries obtained by assembling the binders of Example 2 and Comparative Example 4 were assembled according to the method in Test Example 2, using a visible light-transmitting quartz mold. After 400 charge-discharge cycles, the expansion of the in-situ optical test electrode was measured.

[0154] Figure 1 This is an in-situ optical test photograph of the all-solid-state lithium battery prepared using the binder in Example 2 after completing 400 charge-discharge cycles; Figure 2 The images show in-situ optical test photographs of the all-solid-state lithium battery prepared using the binder in Comparative Example 4 after 400 charge-discharge cycles. The cracks in Comparative Example 4 caused by electrode expansion are larger than those in Example 2, which is also the main reason for its capacity decay.

[0155] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A terpolymer, characterized in that, It is formed by copolymerizing dienes and unsaturated alkoxysilanes to form the main chain, and then introducing thiol groups through a click reaction of dithiol compounds; The unsaturated alkoxysilane contains a carbon-carbon double bond and a siloxy group; The molar ratio of the diene to the unsaturated alkoxysilane is (28~32):(1.1~2).

2. The terpolymer according to claim 1, characterized in that, The diene contains 3 to 8 C atoms; And / or, the diene includes at least one of propylene, 1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene.

3. The terpolymer according to claim 1, characterized in that, The dithiol compound includes at least one of 1,2-ethanedithiol, 1,6-hexanedithiol, polyethylene glycol dithiol, or 1,4-butanedithiol. And / or, the unsaturated alkoxysilane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and allyltrimethoxysilane.

4. A method for preparing the terpolymer according to any one of claims 1 to 3, characterized in that, Includes the following steps: A. Add unsaturated alkoxysilane, deionized water and emulsifier to the reactor and stir until homogeneous. Under inert gas protection, add diene and initiator to carry out the first polymerization reaction. B. After the first polymerization reaction is completed, an acid solution is added to the system to break the emulsion, filter, wash, and perform a first drying to obtain the first polymer; C. The first polymer, photoinitiator, and dithiol compound are added to an organic solvent to carry out a second polymerization reaction to obtain the terpolymer.

5. The preparation method according to claim 4, characterized in that, The emulsifier includes sodium dodecyl sulfate and / or sodium dodecylbenzene sulfonate; And / or, the amount of the emulsifier added is 0.05 to 0.15 times the mass of the unsaturated alkoxysilane; And / or, the amount of deionized water used is 10 to 20 times the mass of the unsaturated alkoxysilane; And / or, the initiator includes at least one of ammonium persulfate, potassium persulfate, and sodium persulfate; And / or, the amount of the initiator added is 0.04 to 0.06 times the mass of the unsaturated alkoxysilane; And / or, the photoinitiator comprises benzophenone and / or 2,4-dihydroxybenzophenone; And / or, the amount of the photoinitiator is 0.05 to 0.12 times the mass of the first polymer; And / or, the amount of the dithiol compound is 0.5 to 1.5 times the mass of the first polymer; And / or, in step C, the organic solvent includes at least one of toluene, p-xylene, dichloromethane, and dibromomethane.

6. The preparation method according to claim 4, characterized in that, The temperature of the first polymerization reaction is 40~60℃; And / or, in step B, the acid solution is a nitric acid solution, a sulfuric acid solution, or a hydrochloric acid solution; And / or, in step B, the concentration of the acid solution is 5~10 wt%; And / or, in step B, the first drying is vacuum drying; And / or, the vacuum drying temperature is 50~70℃ and the time is 18~32h.

7. The preparation method according to claim 4, characterized in that, The second polymerization reaction was carried out under ultraviolet light irradiation; And / or, the power of the ultraviolet light is 0.5~1.5kw, and the irradiation time is 10~30min; And / or, the preparation method further includes filtration after the second polymerization reaction and a second drying process to obtain the terpolymer; And / or, the second drying is vacuum drying; And / or, the vacuum drying temperature is 50~70℃.

8. The application of the terpolymer according to any one of claims 1 to 3 as a binder for silicon anodes in lithium batteries.

9. The application according to claim 8, characterized in that, The lithium battery includes a sulfide all-solid-state lithium-ion battery.

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