An acrylate-based binder suitable for sulfide solid-state electrolytes and a method of preparing the same

Abstract

The application belongs to the technical field of adhesives, and particularly relates to an acrylic ester-based adhesive suitable for sulfide solid electrolytes and a preparation method thereof. The acrylic ester-based adhesive suitable for sulfide solid electrolytes comprises alkyl acrylate, a functional monomer, a crosslinking monomer, a diamond-containing monomer, an ether oxygen-containing chain segment monomer, an initiator and a solvent A; the mass ratio of the alkyl acrylate, the functional monomer, the crosslinking monomer, the diamond-containing monomer and the ether oxygen-containing chain segment monomer is 50-85:10-40:0-5:1-5:1-5. The electrode sheet prepared by using the acrylic ester-based adhesive suitable for sulfide solid electrolytes provided by the application is in close contact with the sulfide electrolyte, the interface is stable, and it is helpful to build a stable ion / electron mixed conductive network, so as to improve the cycle life, rate performance and safety of the all-solid-state battery.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to an acrylate adhesive suitable for sulfide solid electrolytes and its preparation method. Background Technology

[0002] With the rapid development of new energy vehicles, the demand for energy density in lithium-ion batteries is constantly increasing. Currently, commercially available lithium-ion batteries face two major bottlenecks due to the liquid electrolyte: an upper limit on energy density and safety risks. All-solid-state batteries, with their higher energy density, better safety, and longer cycle life, represent the core direction for the technological iteration and upgrading of lithium-ion batteries. Among them, sulfide solid electrolytes, due to their extremely high ionic conductivity and good mechanical ductility, are considered key materials for next-generation high-energy-density all-solid-state lithium batteries. However, their inherent brittleness and poor flexibility often make it difficult to achieve good physical and chemical coupling with the positive electrode active material. During battery charging and discharging, volume changes can easily cause interface cracking, affecting cycle stability.

[0003] To achieve large-scale manufacturing of all-solid-state batteries, slurry-based wet processes are increasingly being used to prepare large-area composite cathodes. The wet process involves dispersing active materials, sulfide electrolytes, and binders in a solvent to prepare a slurry, which is then coated and dried. In all-solid-state batteries, the performance of the cathode plays a crucial role in the overall performance of the battery. Therefore, selecting a suitable binder is essential for forming a uniform electrode.

[0004] Traditional polyvinylidene fluoride (PVDF) adhesives require the use of toxic and volatile N-methylpyrrolidone (NMP) solvents. Furthermore, NMP molecules are highly polar and may undergo interfacial side reactions with sulfide electrolytes, leading to increased interfacial impedance.

[0005] Acrylic polymers, with their abundant functional groups, tunable molecular chain flexibility, and good electrochemical stability, are considered promising alternative binders. For example, Chinese patent CN 120795837 A discloses a solid-state battery binder and its preparation method, comprising: a viscous monomer, wherein the viscous monomer has C3-C... 12 Acrylate monomers with alkyl side chains; lithium-donating monomers, wherein the lithium-donating monomers are monomers containing phosphate esters or monomers containing hydroxyl or amino groups that are easily prepared into phosphate esters through phosphorylation reaction; lithium-conducting monomers, wherein the lithium-conducting monomers are polyethylene glycol acrylates and their derivatives containing ethoxy groups; however, this technical solution does not perform cycle life testing.

[0006] For example, Chinese patent CN 121160251 A discloses an acrylate functional copolymer adhesive, its preparation method, and its application. The raw materials for preparing this acrylate functional copolymer adhesive, by weight, include: 40-60 parts of acrylate flexible monomers, 20-40 parts of acrylate wetting functional monomers containing ether bonds, and 10-30 parts of acrylate rigid monomers. However, the rate performance of this technical solution needs improvement. Summary of the Invention

[0007] The purpose of this invention is to provide an acrylate binder suitable for sulfide solid electrolytes and its preparation method. Electrode sheets prepared using the acrylate binder provided by this invention have close contact with the sulfide electrolyte, exhibiting a stable interface. This facilitates the construction of a robust ion / electron hybrid conductive network, thereby improving the cycle life, rate performance, and safety of all-solid-state batteries.

[0008] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides an acrylate binder suitable for sulfide solid electrolytes, comprising alkyl acrylate, functional monomers, crosslinking monomers, adamantane-containing monomers, ether-containing oxygen segment monomers, an initiator, and solvent A; The mass ratio of the alkyl acrylate, functional monomer, crosslinking monomer, adamantane-containing monomer, and ether-containing oxygen segment monomer is 50-85:10-40:0-5:1-5:1-5.

[0009] As a preferred embodiment of the present invention, the alkyl acrylate is selected from at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0010] As a preferred embodiment of the present invention, the functional monomer is selected from at least one of acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate and styrene.

[0011] As a preferred embodiment of the present invention, the functional monomer is acrylic acid, styrene and hydroxyethyl acrylate; or acrylic acid and acrylonitrile.

[0012] As a preferred embodiment of the present invention, the crosslinking monomer is selected from at least one of divinylbenzene, trimethylolpropane triacrylate and polyethylene glycol diacrylate.

[0013] As a preferred embodiment of the present invention, the adamantane-containing monomer is at least one of 1-adamantane acrylate and adamantane methyl vinyl ether.

[0014] As a preferred embodiment of the present invention, the ether-containing oxygen segment monomer is selected from at least one of polyethylene glycol, polypropylene oxide and polyetheramine.

[0015] As a preferred embodiment of the present invention, the mass ratio of the alkyl acrylate, functional monomer, crosslinking monomer, adamantane-containing monomer, and ether oxygen segment-containing monomer is 70-80:20-25:1-2:1-2:1-2.

[0016] As a preferred embodiment of the present invention, the initiator is selected from at least one of azobisisobutyronitrile, dimethyl azobisisobutyrate, and benzoyl peroxide.

[0017] As a preferred embodiment of the present invention, the amount of the initiator added is 0.1-2% of the total mass of the main monomer, functional monomer, crosslinking monomer and ether-containing oxygen segment monomer.

[0018] As a preferred embodiment of the present invention, solvent A is selected from at least one of toluene, xylene, ethyl acetate, butyl butyrate, anisole, and n-hexane.

[0019] A second aspect of the present invention provides a method for preparing an acrylate binder suitable for sulfide solid electrolytes, comprising the following steps: S1. Add the main monomer, functional monomer, ether-containing oxygen segment monomer and adamantane-containing monomer and organic solvent to the reaction vessel, stir and mix evenly to obtain a monomer mixture. S2. Under an inert atmosphere, heat up, add initiator, then add crosslinking monomer, and maintain the temperature for reaction; S3. After the reaction is complete, cool the reaction solution to room temperature, place it in excess solvent B, precipitate, filter, and dry to obtain an acrylate binder suitable for sulfide solid electrolytes.

[0020] As a preferred embodiment of the present invention, the temperature after heating is 50-90°C.

[0021] As a preferred embodiment of the present invention, the heat preservation reaction time is 4-12 hours.

[0022] As a preferred embodiment of the present invention, the solvent B is selected from at least one of petroleum ether, n-hexane, and methanol.

[0023] As a preferred embodiment of the present invention, the inert atmosphere is nitrogen or argon.

[0024] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The acrylate binder provided by this invention is copolymerized using alkyl acrylates, functional monomers, crosslinking monomers, adamantane-containing monomers, and ether-containing oxygen-chain monomers in specific mass ratios. Alkyl acrylates are the main component, possessing a low glass transition temperature and long alkyl chains that provide flexibility and basic adhesion to the polymer skeleton. The functional monomers, containing polar functional groups, enhance interactions with the surface of sulfide electrolyte particles (such as hydrogen bonds and coordination bonds), forming a strong bond and reducing binder peeling during cycling due to volume changes and stress. They also exhibit chemical compatibility, reducing side reactions and potentially providing lithium-ion transport sites. The crosslinking monomers form a suitable three-dimensional network during curing, improving the mechanical strength of the binder. The binder's strength and dimensional stability enable it to better withstand the volume expansion / contraction stress of the electrode material during lithium-ion insertion / extraction, suppressing the generation and propagation of cracks in the electrode sheet. Adamantane monomers are used to introduce adamantane units into the polymer chain, working synergistically with flexible acrylate segments to achieve a balance of rigidity and flexibility. This maintains a certain level of flexibility while improving the polymer's dimensional stability. Furthermore, the low polarity of adamantane makes it less prone to chemical reactions, improving the stability and ionic conductivity of the sulfide solid electrolyte. Etheroxy monomers are used to introduce etheroxy units into the polymer side chain, enhancing compatibility with lithium salts. They can weakly coordinate with lithium ions, providing additional lithium-ion hopping channels at the polymer-sulfide interface, assisting lithium-ion migration, improving interfacial ion transport, and reducing interfacial impedance.

[0025] 2. The acrylate adhesives provided by this invention can be prepared and used with low-toxicity or non-toxic solvents (such as alcohols and alkanes), avoiding the use of traditional NMP, making them more environmentally friendly and safer to produce.

[0026] 3. The acrylate binder provided by this invention has suitable viscosity and good rheological properties, and is suitable for various electrode preparation processes such as doctor blade coating and spraying.

[0027] 4. The acrylate adhesive provided by this invention has high peel strength, a first coulombic efficiency of more than 80% at 0.5C charge-discharge, and a capacity retention rate of more than 87% after 200 cycles. Attached Figure Description

[0028] Figure 1 The specific capacity of the acrylic adhesive of Example 1 after 200 cycles at 0.5C is given. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1 S1. In a four-necked flask equipped with a stirrer, condenser, and argon inlet tube, add 74g of butyl acrylate, 8g of styrene, 11g of hydroxyethyl acrylate, 3g of acrylic acid, 2g of polyethylene glycol (Mv=1000), 1g of adamantane methyl vinyl ether, and 50g of p-xylene; separately, take a constant pressure dropping funnel, add 0.6g of azobisisobutyronitrile, and dissolve it in 150g of p-xylene to obtain an initiator solution.

[0031] S2. Introduce argon gas and bubble for 30 minutes to remove oxygen. Then, heat the mixture to 70°C under an argon atmosphere, add an initiator solution, and then add 1g of polyethylene glycol diacrylate (Mn=400). Maintain a constant temperature of 70°C and stir for 8 hours.

[0032] S3. After the reaction is complete, cool to room temperature and slowly pour the viscous reaction solution into 500 mL of vigorously stirred methanol. A white fibrous polymer precipitate will form. Filter, collect the precipitate, wash twice with methanol, and place the product in an 80°C vacuum drying oven to dry for 36 hours to obtain an acrylate binder suitable for sulfide solid electrolytes.

[0033] Example 2: This embodiment differs from Example 1 only in the following way: 2g of polyethylene glycol (Mv=1000) is replaced with 1g of polyetheramine (monofunctional, average molecular weight 2000) and 75g of butyl acrylate; all other aspects are the same.

[0034] Example 3: The only difference between this embodiment and Example 1 is as follows: In a four-necked flask equipped with a stirrer, a condenser and an argon inlet tube, 75g of butyl acrylate, 8g of methyl methacrylate, 11g of acrylonitrile, 3g of acrylic acid, 2g of polyethylene glycol (Mv=1000), 1g of adamantane methyl vinyl ether and 50g of p-xylene are added; all other components are the same.

[0035] Example 4: This embodiment differs from Example 1 only in the following way: polyethylene glycol diacrylate (Mn=400) is replaced with an equal mass of trimethylolpropane triacrylate; all other aspects are the same.

[0036] Example 5: The only difference between this embodiment and Example 1 is as follows: S1, In a four-necked flask equipped with a stirrer, a condenser and an argon inlet tube, add 56g of butyl acrylate, 20g of styrene, 20g of acrylic acid, 2g of polyetheramine (monofunctional, average molecular weight 2000), 1g of adamantane methyl vinyl ether and 50g of ethyl acetate; Separately, take a constant pressure dropping funnel and add 0.6g of azobisisobutyronitrile, dissolve it in 150g of ethyl acetate to obtain an initiator solution; All other aspects are the same.

[0037] Comparative Example 1: The only difference between this comparative example and Example 1 is that the functional monomer is styrene, i.e., S1. In a four-necked flask equipped with a stirrer, a condenser and an argon inlet tube, 89g of butyl acrylate, 8g of styrene, 2g of polyethylene glycol (Mv=1000), 1g of adamantane methyl vinyl ether and 50g of p-xylene are added; all other components are the same.

[0038] Comparative Example 2: The only difference between this comparative example and Example 1 is that it does not contain monomers containing ether oxygen segments, i.e., S1; and 76g of butyl acrylate, 8g of styrene, 11g of hydroxyethyl acrylate, 3g of acrylic acid, 1g of adamantane methyl vinyl ether, and 50g of p-xylene are added to a four-necked flask equipped with a stirrer, a condenser, and an argon inlet tube; all other components are the same.

[0039] Comparative Example 3 The only difference between this comparative example and Example 1 is that adamantane methyl vinyl ether is not present, i.e., S1; 75g of butyl acrylate, 8g of styrene, 11g of hydroxyethyl acrylate, 3g of acrylic acid, 2g of polyethylene glycol (Mv=1000), and 50g of p-xylene are added to a four-necked flask equipped with a stirrer, a condenser, and an argon inlet tube; all other components are the same.

[0040] Comparative Example 4 The only difference between this comparative example and Example 1 is as follows: S1, In a four-necked flask equipped with a stirrer, a condenser and an argon inlet tube, add 45g of butyl acrylate, 10g of styrene, 22g of hydroxyethyl acrylate, 5g of acrylic acid, 6g of polyethylene glycol (Mv=1000), 6g of adamantane methyl vinyl ether and 50g of p-xylene; Separately, take a constant pressure dropping funnel and add 0.6g of azobisisobutyronitrile, dissolve it in 150g of p-xylene to obtain an initiator solution.

[0041] S2. Introduce argon gas and bubble for 30 minutes to remove oxygen. Then, heat to 70°C under argon atmosphere, add initiator solution, and then add 6g of polyethylene glycol diacrylate (Mn=400). Maintain constant temperature at 70°C and stir for 8 hours. The rest is the same.

[0042] Comparative Example 5 The only difference between this comparative example and Example 1 is as follows: S1, In a four-necked flask equipped with a stirrer, a condenser and an argon inlet tube, add 88g of butyl acrylate, 3g of styrene, 5g of hydroxyethyl acrylate, 1g of acrylic acid, 2g of polyethylene glycol (Mv=1000), 0.5g of adamantane methyl vinyl ether and 50g of p-xylene; Separately, take a constant pressure dropping funnel and add 0.6g of azobisisobutyronitrile, dissolve it in 150g of p-xylene to obtain an initiator solution.

[0043] S2. Introduce argon gas and bubble for 30 minutes to remove oxygen. Then, heat to 70°C under argon atmosphere, add initiator solution, and then add 0.5g of polyethylene glycol diacrylate (Mn=400). Maintain constant temperature at 70°C and stir for 8 hours. The rest is the same.

[0044] Comparative Example 6 This comparative example differs from Example 1 only in the following way: polyethylene glycol (Mv=1000) is replaced with an equal mass of polyethylene glycol methyl ether acrylate (Mn=480); all other aspects are the same.

[0045] Comparative Example 7 This comparative example differs from Example 1 only in the following aspect: adamantane methyl vinyl ether is replaced with 2-allylnaphthalene; all other aspects are the same.

[0046] Comparative Example 8 This comparative example differs from Example 1 only in the following aspect: the acrylate adhesive is replaced with a PVDF adhesive; all other aspects are the same.

[0047] Performance testing: Preparation of the positive electrode sheet: High-nickel ternary positive electrode material (NCM811), silver-germanium sulfide electrolyte (Li6PS5Cl) powder, acrylate binders prepared in Examples 1-5, Comparative Examples 1-7, and PVDF binder in Comparative Example 8, and conductive agent Super C were mixed at a mass ratio of 75:15:5:5. An appropriate amount of n-heptane was added as a solvent, and the mixture was stirred for 4 hours to obtain a uniform slurry with a solid content of 30%. The slurry was coated onto an aluminum foil current collector using a 200µm SQZ four-sided coating tool. After the solvent evaporated at room temperature, it was transferred to an 80℃ vacuum oven for drying for 12 hours. Subsequently, it was hot-pressed at 10MPa pressure and 100℃ for 1 minute to obtain the positive electrode sheet.

[0048] Preparation of sulfide electrolyte layer: Li6PS5Cl powder was pressed into thin sheets at 300MPa to obtain sulfide electrolyte layer.

[0049] Assembly of CR2032 all-solid-state battery: In an argon-protected glove box, the positive electrode, sulfide electrolyte sheet, and lithium metal sheet (negative electrode) are placed into a button cell mold in sequence. A certain pressure (50MPa) is applied to ensure that each layer is in close contact, and the CR2032 all-solid-state battery is assembled for testing.

[0050] The acrylate binders, slurries, electrodes, and batteries obtained in the examples and comparative examples were tested using the following methods: 1. Peel strength test: According to GB 2792-2014 "Test Method for Peel Strength of Adhesive Tape", the peel force of the slurry to the positive electrode was tested using the 180° peel test method. The average value of 10 tests was recorded in Table 1.

[0051] 2. Viscosity test: The viscosity of acrylic adhesives at 25°C was tested using a viscosity meter.

[0052] 3. Cyclic performance test: The assembled battery was placed in a 25°C constant temperature chamber for 12 hours. Then, the positive electrode was subjected to a 0.5C charge-discharge test within a voltage range of 3.0-4.3V. The initial charge-discharge specific capacity, initial coulombic efficiency, and capacity retention after 200 cycles were tested. The specific capacity of the acrylic binder in Example 1 after 200 cycles at 0.5C was as follows: Figure 1 As shown.

[0053] The test results are shown in Table 1 below: Table 1 Test Results As can be seen from Table 1, the acrylate binders of Examples 1-5 have suitable viscosity and good rheological properties; the slurry prepared using the acrylate binders of Examples 1-5 has high peel strength to the positive electrode, and the prepared all-solid-state battery has high 0.5C first charge-discharge specific capacity, first coulombic efficiency, and high 0.5C cycle performance.

[0054] As can be seen from Example 1 and Comparative Examples 1-3, when the functional monomer only contains styrene or does not contain monomers containing ether oxygen segments or does not contain adamantane methyl vinyl ether, the bonding strength and viscosity of the prepared acrylate binder decrease, the cycle performance of the battery deteriorates, ion transport is hindered, resulting in low capacity and coulombic efficiency.

[0055] As can be seen from Examples 1 and Comparative Examples 4-5, when alkyl acrylates, functional monomers, crosslinking monomers, adamantane-containing monomers, and ether-containing oxygen segment monomers are not within the scope of protection of this invention, the bonding strength and viscosity of the prepared acrylate binders decrease, the cycle performance of the battery deteriorates, and the capacity and coulombic efficiency are low.

[0056] As can be seen from Examples 1 and Comparative Examples 6-7, when the monomers containing adamantane or ether oxygen segments are changed, the bonding strength and viscosity of the prepared acrylate binders decrease, the cycle performance of the battery deteriorates, and the capacity and coulombic efficiency are low.

[0057] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An acrylate binder suitable for sulfide solid electrolytes, characterized in that, Includes alkyl acrylates, functional monomers, crosslinking monomers, adamantane-containing monomers, ether-containing oxygen segment monomers, initiators, and solvent A; The mass ratio of the alkyl acrylate, functional monomer, crosslinking monomer, adamantane-containing monomer, and ether-containing oxygen segment monomer is 50-85:10-40:0-5:1-5:1-5.

2. The acrylate binder for sulfide solid electrolytes according to claim 1, characterized in that, The alkyl acrylate is selected from at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, and ethyl methacrylate.

3. The acrylate binder for sulfide solid electrolytes according to claim 2, characterized in that, The functional monomer is selected from at least one of acrylic acid, acrylamide, acrylonitrile, hydroxyethyl acrylate and styrene.

4. The acrylate binder for sulfide solid electrolytes according to claim 3, characterized in that, The functional monomers are acrylic acid, styrene, and hydroxyethyl acrylate; or acrylic acid and acrylonitrile.

5. The acrylate binder for sulfide solid electrolytes according to any one of claims 1-4, characterized in that, The crosslinking monomer is selected from at least one of divinylbenzene, trimethylolpropane triacrylate, and polyethylene glycol diacrylate.

6. The acrylate binder for sulfide solid electrolytes according to claim 5, characterized in that, The adamantane-containing monomer is at least one of 1-adamantane acrylate and adamantane methyl vinyl ether.

7. The acrylate binder for sulfide solid electrolytes according to claim 6, characterized in that, The ether-containing oxygen segment monomer is selected from at least one of polyethylene glycol, polypropylene oxide, and polyetheramine.

8. The acrylate binder for sulfide solid electrolytes according to claim 6 or 7, characterized in that, The mass ratio of the alkyl acrylate, functional monomer, crosslinking monomer, adamantane-containing monomer, and ether-containing oxygen segment monomer is 70-80:20-25:1-2:1-2:1-2.

9. The method for preparing an acrylate binder suitable for sulfide solid electrolytes according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add the main monomer, functional monomer, ether-containing oxygen segment monomer and adamantane-containing monomer and organic solvent to the reaction vessel, stir and mix evenly to obtain a monomer mixture. S2. Under an inert atmosphere, heat up, add initiator, then add crosslinking monomer, and maintain the temperature for reaction; S3. After the reaction is complete, cool the reaction solution to room temperature, place it in excess solvent B, precipitate, filter, and dry to obtain an acrylate binder suitable for sulfide solid electrolytes.

10. The method for preparing an acrylate binder suitable for sulfide solid electrolytes according to claim 9, characterized in that, The temperature after heating is 50-90℃; the heat preservation reaction time is 4-12h.

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