Polymer adhesive film for battery interface, preparation method of polymer adhesive film and solid-state battery

Abstract

The invention relates to the technical field of secondary batteries, in particular to a polymer adhesive film for a battery interface, a preparation method of the polymer adhesive film and a solid-state battery. The preparation method of the polymer adhesive film for the battery interface comprises the following steps: carrying out illumination pretreatment on a mixture of a comonomer, a photoinitiator, a solid lithium salt and a cross-linking agent to obtain pre-polymerized slurry; and coating the pre-polymerized slurry, and carrying out illumination curing to obtain the polymer adhesive film for the battery interface. The specific comonomer is matched with the photoinitiator, the solid-state lithium salt and the cross-linking agent, the polymer adhesive film with good adhesive property and ionic conductivity can be obtained through prepolymerization, coating and curing under the condition that no solvent is introduced, the polymer adhesive film can be used for solid-state battery interface modification and interface adhesion, and the service life of the solid-state battery is prolonged. The interface of a solid-state battery device and the device processing problem can be effectively improved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a polymer adhesive film for battery interfaces, a method for preparing the same, and a solid-state battery. Background Technology

[0002] The development of sustainable, high-energy-density, high-performance lithium-ion batteries is a key technological pillar in the global transition to a fossil fuel-free economy, and its performance improvement largely depends on the development and application of new materials. Among these, the polymer chain structure and bridging effect of binders can construct efficient ion / electron transport pathways and provide necessary mechanical stability and flexibility, playing a crucial role in improving the cycle performance of electrode materials. Furthermore, in the interface design of all-solid-state batteries based on silicon or lithium metal anodes, endowing binders with new functions, such as improving the ion transport properties of the interface layer, suppressing interfacial side reactions, and reducing interfacial contact resistance, can solve interfacial contact problems and significantly improve the performance of solid-state batteries.

[0003] In view of the above, the present invention is hereby proposed. Summary of the Invention The purpose of this invention is to provide a polymer adhesive film for battery interfaces, a method for preparing the same, and a solid-state battery. The polymer adhesive film for battery interfaces of this invention can be used for interface modification and bonding in solid-state batteries, and can effectively improve the interface and device processing problems of solid-state battery devices.

[0004] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a method for preparing a polymer adhesive film for a battery interface, comprising the following steps: A mixture of comonomer, photoinitiator, solid lithium salt and crosslinking agent is subjected to photopretreatment to obtain a prepolymer slurry; the prepolymer slurry is coated and then photocured to obtain the polymer adhesive film for the battery interface. The comonomer comprises, by mass percentage, 5%–15% of a first monomer and 85%–95% of a second monomer; the first monomer comprises (meth)acrylic acid, and the second monomer comprises at least one of the structures shown in the following formula: , , ; Wherein, n1, n2 and n3 are each independently selected from integers between 1 and 30; R1 is selected from hydrogen and methyl, and R2, R3 and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, aryl and substituted aryl.

[0005] In a specific embodiment of the present invention, n1, n2 and n3 are each independently selected from integers between 2 and 16, preferably integers between 9 and 16.

[0006] In a specific embodiment of the present invention, in R2, R3 and R4, each alkyl group is independently selected from alkyl groups having 1 to 3 carbon atoms; in the substituted alkyl group, the substituent is selected from at least one of hydroxyl and alkoxy groups; the aryl group includes phenyl groups; in the substituted aryl group, the substituent is selected from at least one of hydroxyl, alkoxy and alkyl groups having 1 to 10 carbon atoms.

[0007] In a specific embodiment of the present invention, the second monomer includes at least one of (ethoxy)phenol acrylate, (ethoxy)phenol methacrylate, (ethoxy)nonylphenol acrylate, (ethoxy)nonylphenol methacrylate, methoxy polyethylene glycol acrylate, and methoxy polyethylene glycol methacrylate.

[0008] In a specific embodiment of the present invention, the molar ratio of the solid lithium salt (calculated as Li) to the second monomer (calculated as the ethoxy group it contains) is (0.1-2):1, preferably (0.5-1.5):1.

[0009] In a specific embodiment of the present invention, the crosslinking agent includes at least one of the structures shown in the following formula: , , , , , , , , ; Where, n4~n 12 Each integer is independently selected from those greater than 1; R5~R 12 Each is independently selected from hydrogen and methyl.

[0010] In a specific embodiment of the present invention, the amount of the crosslinking agent is 0.1wt% to 3wt% of the total mass of the comonomer.

[0011] In a specific embodiment of the present invention, the solid lithium salt includes lithium hydroxide, lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium fluoride, lithium hexafluorophosphate, lithium chloride, lithium tetrafluorophosphate, and Li7La3Zr2O. 12 and Li 10 GeP2S 12 At least one of them.

[0012] In a specific embodiment of the present invention, the photoinitiator includes at least one selected from 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and benzophenone.

[0013] In a specific embodiment of the present invention, the amount of the photoinitiator is 0.1 wt% to 5 wt% of the sum of the mass of the comonomer and the crosslinking agent.

[0014] In a specific embodiment of the present invention, the viscosity of the prepolymer slurry at 25°C is 500-1000 cp.

[0015] In a specific embodiment of the present invention, the light wavelengths in the light pretreatment and the light curing are each independently selected from 200 to 450 nm.

[0016] In a specific embodiment of the present invention, the prepolymer slurry does not contain solvent.

[0017] The second aspect of the present invention provides a polymer adhesive film for battery interfaces prepared by the preparation method of the first aspect of the present invention.

[0018] In a specific embodiment of the present invention, the thickness of the polymer adhesive film for the battery interface is 1 to 30 μm, preferably 10 to 15 μm.

[0019] A third aspect of the present invention provides a solid-state battery, including the polymer adhesive film for battery interface provided in the second aspect of the present invention.

[0020] In a specific embodiment of the present invention, the solid-state battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, wherein the solid electrolyte layer is disposed between the positive electrode and the negative electrode; the battery interface is disposed between the positive electrode and the solid electrolyte layer, and / or between the negative electrode and the solid electrolyte layer, using a polymer adhesive film.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes specific comonomers, combined with photoinitiators, solid lithium salts, and crosslinking agents, to obtain a polymer adhesive film with both good adhesion and ionic conductivity through prepolymerization, coating, and curing without the introduction of solvents. This film can be used for interface modification and bonding in solid-state batteries, effectively improving the interface and device processing problems of solid-state battery devices. Attached Figure Description

[0022] 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.

[0023] Figure 1This is a schematic diagram of the process for preparing a polymer adhesive film for battery interfaces provided in an embodiment of the present invention; Figure 2 The image shows the AC impedance diagrams of the polymer adhesive film for battery interface prepared in Example 1c of the present invention at different temperatures. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] With the development of solid-state batteries, the function of binders is no longer limited to adhering active materials and conductive agents to current collectors to prevent them from detaching. Constructing an artificial interface layer on the electrode surface plays a crucial role in improving the overall performance of solid-state batteries. To achieve this function, binders need to meet the following requirements: first, they must be able to establish effective ion and electron transport channels; second, they must ensure the stability of the solid electrode-electrolyte interface (including SEI and CEI); and third, they must possess self-healing capabilities to compensate for changes in electrode material volume. For example, Chinese patent applications with publication numbers CN117976907A and CN112615046A disclose technical solutions for improving battery performance by optimizing the solid electrolyte interface layer. However, these methods still rely on solvent-assisted film formation, which not only increases the complexity of production but may also affect interface stability due to solvent residues, thus limiting their application in large-scale mass production.

[0027] Based on this, the first aspect of the present invention provides a method for preparing a polymer adhesive film for a battery interface, comprising the following steps: A mixture of comonomer, photoinitiator, solid lithium salt and crosslinking agent is subjected to photopretreatment to obtain a prepolymer slurry; the prepolymer slurry is coated and then photocured to obtain a polymer adhesive film for battery interface. The comonomer comprises, by mass percentage, 5%–15% of a first monomer and 85%–95% of a second monomer; the first monomer comprises (meth)acrylic acid, and the second monomer comprises at least one of the structures shown in the following formula: , , ; Wherein, n1, n2 and n3 are each independently selected from integers between 1 and 30; R1 is selected from hydrogen and methyl, and R2, R3 and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, aryl and substituted aryl.

[0028] This invention utilizes specific comonomers, combined with photoinitiators, solid lithium salts, and crosslinking agents, to obtain a polymer adhesive film with both good adhesion and ionic conductivity through prepolymerization, coating, and curing without the introduction of solvents. This film can be used for interface modification and bonding in solid-state batteries, effectively improving the interface and device processing problems of solid-state battery devices.

[0029] The introduction of the first monomer primarily imparts certain adhesive properties to the polymer adhesive film. The second monomer is a photocurable substance with certain ethoxy (EO) segments. The polarity of the EO segments effectively promotes the dissociation of lithium salts and enhances ion migration; the flexibility of the EO segments endows the polymer adhesive film with certain chain movement capabilities, which not only improves lithium-ion transport kinetics but also adapts to volume changes in the electrode material during charging and discharging. Furthermore, the introduction of EO segments improves the wettability of the electrode-electrolyte interface and reduces interfacial impedance. The combination of these two monomers comprehensively improves the adhesive properties, ionic conductivity, and interfacial stability of the polymer adhesive film.

[0030] In different embodiments, the amount of the first monomer, by mass percentage, can be 5%, 6%, 8%, 10%, 12%, 15%, or any combination thereof; the amount of the second monomer can be 85%, 88%, 90%, 92%, 94%, 95%, or any combination thereof. When the amount of the first monomer is too low, the cohesive bond strength of the polymer adhesive film is too low and cannot meet the requirements of adhesive performance; when the amount of the first monomer is too high, the ionic conductivity and interfacial stability of the polymer adhesive film are insufficient.

[0031] In a specific embodiment of the present invention, n1, n2 and n3 are each independently selected from integers between 2 and 16, preferably integers between 9 and 16.

[0032] In the second monomer of the present invention, n1, n2, and n3 can each independently be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, preferably 9 to 16. When the EO segment in the second monomer is too short, the improvement in the ionic conductivity of the polymer adhesive film is not significant; when the EO segment in the second monomer is too long, it will lead to a significant reduction in the adhesive performance of the polymer adhesive film, and the improvement in ion-pair conductivity is not significant.

[0033] In specific embodiments of the present invention, in R2, R3 and R4, each alkyl group is independently selected from alkyl groups having 1 to 3 carbon atoms; in substituted alkyl groups, the substituent is selected from at least one of hydroxyl and alkoxy groups; aryl groups include phenyl groups; in substituted aryl groups, the substituent is selected from at least one of hydroxyl, alkoxy and alkyl groups having 1 to 10 carbon atoms.

[0034] Wherein, alkyl groups having 1 to 3 carbon atoms include any one of methyl, ethyl, n-propyl, and isopropyl; substituted alkyl refers to a group in which at least one hydrogen atom of an alkyl group is replaced by a hydroxyl or alkoxy group, and the alkyl group in the substituted alkyl group may have 1 to 3 carbon atoms; substituted aryl refers to a group in which at least one hydrogen atom of an aryl group is replaced by a hydroxyl, alkoxy, or an alkyl group having 1 to 10 carbon atoms.

[0035] In a specific embodiment of the present invention, the second monomer includes at least one of (ethoxy)phenol acrylate, (ethoxy)phenol methacrylate, (ethoxy)nonylphenol acrylate, (ethoxy)nonylphenol methacrylate, methoxy polyethylene glycol acrylate, and methoxy polyethylene glycol methacrylate.

[0036] In a specific embodiment of the present invention, the molar ratio of the solid lithium salt (calculated as Li) to the second monomer (calculated as the ethoxy group (EO) it contains) is (0.1-2):1, preferably (0.5-1.5):1.

[0037] In different embodiments, the molar ratio of the solid lithium salt (calculated as Li) to the second monomer (calculated as the EO content) can be within the range of 0.1:1, 0.2:1, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, or any combination thereof. Adjusting the ratio of the solid lithium salt to the second monomer to meet the above range helps to fully utilize the increased ionic conductivity of the EO segment and lithium salt combination and ensures the adhesive performance of the polymer adhesive film.

[0038] In a specific embodiment of the present invention, the crosslinking agent includes at least one of the structures shown in the following formula: , , , , , , , , ; Where, n4~n 12 Each integer is independently selected from those greater than 1; R5~R 12 Each is independently selected from hydrogen and methyl. For example, in different embodiments, n4 to n 12 Each can be an independent range consisting of 2, 3, 4, 5, 6, 7, 8, 9, 10, or any two of them.

[0039] In a specific embodiment of the present invention, the crosslinking agent includes at least one of polyethylene glycol di(meth)acrylate, methoxy polyethylene glycol bis(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, ethoxylated bis-trimethylolpropane tetra(meth)acrylate, and ethoxylated pentaerythritol tetra(meth)acrylate.

[0040] In a specific embodiment of the present invention, the amount of crosslinking agent is 0.1wt% to 3wt% of the total mass of the comonomer, such as 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, or any combination thereof.

[0041] In specific embodiments of the present invention, the solid lithium salt includes lithium hydroxide, lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium fluoride, lithium hexafluorophosphate, lithium chloride, lithium tetrafluorophosphate, and Li7La3Zr2O. 12 (LLZO) and Li 10 GeP2S 12 At least one of (LGPS).

[0042] In a specific embodiment of the present invention, the photoinitiator includes at least one selected from 1-hydroxycyclohexylphenyl ketone (HCPK), 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and benzophenone (BP).

[0043] In a specific embodiment of the present invention, the amount of photoinitiator is 0.1wt% to 5wt% of the total mass of the comonomer and the crosslinking agent, for example, it can be 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, or any combination thereof.

[0044] In a specific embodiment of the present invention, the viscosity of the prepolymer slurry at 25°C is 500–1000 cp, such as 500 cp, 600 cp, 700 cp, 800 cp, 900 cp, 1000 cp, or any combination thereof, to ensure coating uniformity. The specific conditions for the photopretreatment are not limited, as long as the viscosity of the prepolymer slurry meets the above-mentioned range.

[0045] In a specific embodiment of the present invention, the light wavelengths in the light pretreatment and the light curing are each independently selected from 200 to 450 nm, for example, 365 nm, 385 nm, 405 nm, etc.

[0046] In a specific embodiment of the present invention, the preparation of the mixture includes: mixing the comonomer, photoinitiator, solid lithium salt and crosslinking agent in proportion, and then degassing.

[0047] In a specific embodiment of the present invention, the prepolymer slurry does not contain solvent.

[0048] In a specific embodiment of the present invention, a prepolymer slurry is coated onto the surface of a release film, and then cured by light; the coated layer is cured to form a polymer adhesive film for the battery interface. The release film can be removed during use.

[0049] Figure 1 This is a schematic diagram of the process for preparing a polymer adhesive film for battery interfaces provided in an embodiment of the present invention. Comonomers, photoinitiators, solid lithium salts, and crosslinking agents can be added to a storage tank through different feeding hoppers. The mixture is stirred evenly by a stirring pump, degassed, and then subjected to photopretreatment to obtain a prepolymer slurry with a viscosity that meets the coating requirements. Then, it is coated onto the surface of a release film material by a coating machine and cured by UV light to obtain a polymer adhesive film for battery interfaces.

[0050] The second aspect of the present invention provides a polymer adhesive film for battery interfaces prepared by the preparation method of the first aspect of the present invention.

[0051] In a specific embodiment of the present invention, the thickness of the polymer adhesive film for the battery interface is 1 to 30 μm, preferably 10 to 15 μm. For example, the thickness can be 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any combination thereof.

[0052] In a specific embodiment of the present invention, the polymer adhesive film for the battery interface has an ionic conductivity σ > 1 × 10⁻⁶ at 30°C. -4 S / cm, preferably σ>1×10 -3 S / cm.

[0053] A third aspect of the present invention provides a solid-state battery, including the polymer adhesive film for battery interface provided in the second aspect of the present invention.

[0054] In a specific embodiment of the present invention, the solid-state battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, with the solid electrolyte layer disposed between the positive and negative electrode. A polymer adhesive film for the battery interface is disposed between the positive electrode and the solid electrolyte layer, and / or between the negative electrode and the solid electrolyte layer. The polymer adhesive film of the present invention can be used for bonding the positive or negative electrode to the solid electrolyte layer, and can also serve as an artificial cathode-electrolyte interface layer (CEI) or anode-electrolyte interface layer (SEI).

[0055] In a specific embodiment of the present invention, the solid-state battery includes at least one of lithium metal solid-state battery and silicon-based solid-state battery.

[0056] The comonomers, photoinitiators, lithium salts, crosslinking agents, etc. used in the specific embodiments of the present invention can all be obtained commercially. For example, some crosslinking agents can be monomers from MIWON Corporation, such as the M283 series, but are not limited thereto.

[0057] Example 1 Group This embodiment group provides a method for preparing a polymer adhesive film for battery interfaces, including the following steps: (1) Take the comonomer, photoinitiator, solid lithium salt and crosslinking agent, degas them to obtain slurry, and then prepolymerize it under 365nm ultraviolet light to make its viscosity at 25℃ reach 500~1000cp (e.g. 800cp±100cp) to obtain prepolymerized slurry; (2) The prepolymer slurry is coated on the release film and photocured by 365 nm ultraviolet light for 20s to obtain a polymer adhesive film for battery interface with a thickness of 10μm after curing.

[0058] The comonomers include 10 parts by weight of acrylic acid and 90 parts by weight of methoxy polyethylene glycol acrylate (MP(EO)nMA); the photoinitiator is 0.5 parts by weight of HCPK; the solid lithium salt is lithium hydroxide, and the molar ratio of lithium hydroxide (calculated as Li) to methoxy polyethylene glycol acrylate (calculated as EO) is 0.5:1; the crosslinking agent is 1 part by weight of methoxy polyethylene glycol diacrylate (n=5), with the following structural formula: .

[0059] In the preparation methods of the polymer adhesive film for battery interface in different embodiments of Example 1, the n value in methoxy polyethylene glycol acrylate (MP(EO)nMA) is different, and the general structural formula is as follows. The n values ​​corresponding to the methoxy polyethylene glycol acrylate used in different embodiments are shown in Table 1: .

[0060] Table 1 Raw material information for different embodiments

[0061] Example 2 group This embodiment group provides a method for preparing a polymer adhesive film for battery interfaces, including the following steps: (1) Take the comonomer, photoinitiator, solid lithium salt and crosslinking agent, degas them to obtain slurry, and then prepolymerize it under 365nm ultraviolet light to make its viscosity at 25℃ reach 500~1000cp (e.g. 800cp±100cp) to obtain prepolymerized slurry; (2) The prepolymer slurry is coated on the release film and photocured by 365 nm ultraviolet light for 20 s to obtain a polymer adhesive film for battery interface with a thickness of 10 μm after curing.

[0062] The comonomers include acrylic acid and methoxy polyethylene glycol acrylate (MP(EO)9MA); the photoinitiator is 0.5 parts by weight of HCPK; the solid lithium salt is lithium hydroxide, and the molar ratio of lithium hydroxide (calculated as Li) to methoxy polyethylene glycol acrylate (calculated as EO) is 0.5:1; the crosslinking agent is 1 part by weight of methoxy polyethylene glycol diacrylate (n=5).

[0063] In the preparation methods of the polymer adhesive film for battery interfaces in different embodiments of Example 2, the weight parts of acrylic acid and methoxy polyethylene glycol acrylate (MP(EO)9MA) are different, as shown in Table 2. The structural formula of methoxy polyethylene glycol acrylate (MP(EO)9MA) is as follows: .

[0064] Table 2 Raw material information for different embodiments

[0065] Example 3 Group This embodiment group provides a method for preparing a polymer adhesive film for battery interfaces, including the following steps: (1) Take the comonomer, photoinitiator, solid lithium salt and crosslinking agent, degas them to obtain slurry, and then prepolymerize it under 365nm ultraviolet light to make its viscosity at 25℃ reach 500~1000cp (e.g. 800cp±100cp) to obtain prepolymerized slurry; (2) The prepolymer slurry is coated on the release film and photocured by 365nm ultraviolet light for 20 s to obtain a polymer adhesive film for battery interface with a thickness of 10μm after curing.

[0066] The comonomers include 10 parts by weight of acrylic acid and 90 parts by weight of methoxy polyethylene glycol acrylate (MP(EO)9MA); the photoinitiator is 0.5 parts by weight of HCPK; the solid lithium salt is lithium hydroxide, and the molar ratio of lithium hydroxide (calculated as Li) to methoxy polyethylene glycol acrylate (calculated as EO) is (0.1~2):1; the crosslinking agent is 1 part by weight of methoxy polyethylene glycol diacrylate (n=5).

[0067] In the preparation methods of the polymer adhesive film for battery interfaces in different embodiments of Example 3, the solid lithium salt is lithium hydroxide, and the molar ratio (Li:EO) of lithium hydroxide (calculated as Li) to methoxy polyethylene glycol acrylate (calculated as EO) varies, as detailed in Table 3. The structural formula of methoxy polyethylene glycol acrylate (MP(EO)9MA) is as follows: .

[0068] Table 3 Raw material information for different embodiments

[0069] Example 4 group Example 4 uses the same method as Example 3c for preparing the polymer adhesive film for the battery interface, except that the type of crosslinking agent is different. The specific differences are as follows: In Example 4a, an equal weight of methoxy polyethylene glycol diacrylate (n=9) was used to replace the methoxy polyethylene glycol diacrylate (n=5) in Example 3c; the structural formula of the methoxy polyethylene glycol diacrylate (n=9) is as follows: ; In Example 4b, an equal weight of pentaerythritol tetraacrylate ethoxylate was used to replace the methoxylated polyethylene glycol diacrylate in Example 3c (n=5); wherein, the structural formula of pentaerythritol tetraacrylate ethoxylate is as follows: ; In Example 4c, pentaerythritol tetraacrylate was used in place of methoxy polyethylene glycol diacrylate in Example 3c (n=5).

[0070] Experimental Example The polymer adhesive films for battery interfaces prepared in different embodiments were tested as follows, and the test results are shown in Table 4.

[0071] Ionic conductivity (30℃): Polymer adhesive films prepared in different embodiments were cut into Φ17mm discs, the release film was removed, and they were assembled with stainless steel sheets into button cells to test the AC impedance spectrum of the polymer adhesive films. According to the formula... Calculate the ionic conductivity at 30℃. Where σ is the ionic conductivity. lThe thickness of the polymer adhesive film, S To test the contact surface area of ​​the polymer adhesive film, R The intrinsic impedance of the polymer adhesive film obtained from the corresponding impedance spectroscopy test. Figure 2 The image shows the AC impedance diagrams of the polymer adhesive film for battery interface prepared in Example 1c of the present invention at different temperatures.

[0072] Adhesion strength: The polymer adhesive films prepared in different embodiments were cut into 10mm pieces, the release film was peeled off, one side was attached to a clean stainless steel plate, and the other side was covered with a lithium iron phosphate positive electrode sheet. The sample was then rolled back and forth three times using a 1kg roller. After being placed at room temperature (25℃) for 30 minutes, the peel force between the polymer adhesive film and the lithium iron phosphate layer was tested using a universal tensile testing machine according to the test conditions of the national standard GB / T 2792-2014.

[0073] The preparation of the lithium iron phosphate positive electrode sheet includes: weighing the positive electrode active material lithium iron phosphate, conductive agent carbon black (Ketjen black), and PVDF binder at a solid mass ratio of 96:1.5:2.5, adding the solvent N,N-dimethylpyrrolidone, stirring to obtain a lithium-ion battery positive electrode slurry, coating the slurry onto carbon-coated aluminum foil, and drying to obtain the positive electrode sheet. The coating density on one side of the electrode sheet is 18 mg / cm³. 2 Compacted density 2.4 g / cm³ 3 .

[0074] Table 4 Test results for different embodiments

[0075] As can be seen from the above test results, by using specific comonomers, combined with photoinitiators, solid lithium salts and crosslinking agents, this invention can obtain a polymer adhesive film with both good adhesion and ionic conductivity through prepolymerization, coating and curing without the introduction of solvents.

[0076] According to the test results of Example 1, the ionic conductivity of the polymer adhesive film varies with the length of the EO segment of the second monomer, methoxy polyethylene glycol acrylate, used as the comonomer. When the length of the EO segment of methoxy polyethylene glycol acrylate is within a certain range, the ionic conductivity of the polymer adhesive film increases with the increase of the EO segment length, but decreases when the EO segment length further increases. In addition, the adhesive performance of the polymer adhesive film decreases with the increase of the EO segment length.

[0077] According to the test results of Example 2, when the comonomer lacks acrylic monomer, the cohesive bonding strength of the polymer adhesive film is drastically reduced, and it cannot maintain effective bonding to the electrode. As the amount of acrylic monomer in the comonomer increases, the bonding performance gradually improves, but at the same time, it will cause a decrease in ionic conductivity. Regulating the amount of acrylic acid and methoxy polyethylene glycol acrylate in the comonomer within a certain range helps to improve the balance between ionic conductivity and bonding performance.

[0078] According to the test results of Example 3, the ionic conductivity of the polymer adhesive film increases with the increase of the amount of solid lithium salt. However, excessive lithium salt will cause the acrylic group to lose its adhesive effect. Therefore, adjusting the ratio of lithium salt to the second monomer to meet certain conditions is more helpful to improve the ionic conductivity and adhesive performance.

[0079] According to the test results of Example 4, when using an ethoxylated multifunctional crosslinking agent, compared with a non-ethoxylated multifunctional crosslinking agent, it has a greater advantage in improving the ionic conductivity and adhesive performance of the polymer adhesive film. This is mainly due to the increase in ethoxylated groups, which provides more lithium ion binding / transport sites and also provides some ionic crosslinking sites, thus synergistically improving the ionic conductivity and adhesive performance of the polymer adhesive film.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a polymer adhesive film for battery interfaces, characterized in that, Includes the following steps: A mixture of comonomer, photoinitiator, solid lithium salt and crosslinking agent is subjected to photopretreatment to obtain a prepolymer slurry; the prepolymer slurry is coated and then photocured to obtain the polymer adhesive film for the battery interface. The comonomer comprises, by mass percentage, 5%–15% of a first monomer and 85%–95% of a second monomer; the first monomer comprises (meth)acrylic acid, and the second monomer comprises at least one of the structures shown in the following formula: 、 、 ； Wherein, n1, n2 and n3 are each independently selected from integers between 2 and 16; R1 is selected from hydrogen and methyl, and R2, R3 and R4 are each independently selected from hydrogen, alkyl, substituted alkyl, aryl and substituted aryl.

2. The preparation method according to claim 1, characterized in that, n1, n2, and n3 are each independently selected from integers between 9 and 16.

3. The preparation method according to claim 1, characterized in that, R2, R3, and R4 have at least one of the following characteristics: (1) Each of the alkyl groups is independently selected from alkyl groups having 1 to 3 carbon atoms; (2) In the substituted alkyl group, the substituent is selected from at least one of hydroxyl and alkoxy groups; (3) The aryl group includes phenyl; (4) In the substituted aryl group, the substituent is selected from at least one of hydroxyl, alkoxy and alkyl with 1 to 10 carbon atoms.

4. The preparation method according to claim 1, characterized in that, The second monomer includes at least one of (ethoxy)phenol acrylate, (ethoxy)phenol methacrylate, (ethoxy)nonylphenol acrylate, (ethoxy)nonylphenol methacrylate, methoxy polyethylene glycol acrylate, and methoxy polyethylene glycol methacrylate.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the solid lithium salt (calculated as Li) to the second monomer (calculated as the ethoxy group it contains) is (0.1–2):

1.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent has at least one of the following characteristics: (1) The crosslinking agent comprises at least one of the structures shown in the following formula: 、 、 、 、 、 、 、 、 ； Where, n4~n 12 Each integer is independently selected from those greater than 1; R5~R 12 Each is independently selected from hydrogen and methyl; (2) The amount of the crosslinking agent is 0.1wt% to 3wt% of the total mass of the comonomer.

7. The preparation method according to claim 1, characterized in that, It has at least one of the following characteristics: (1) The solid lithium salt includes lithium hydroxide, lithium bis(trifluoromethanesulfonyl)imide, lithium bisfluorosulfonylimide, lithium fluoride, lithium hexafluorophosphate, lithium chloride, lithium tetrafluorophosphate, and Li7La3Zr2O. 12 and Li 10 GeP2S 12 At least one of them; (2) The photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanone and benzophenone; (3) The amount of the photoinitiator is 0.1 wt% to 5 wt% of the sum of the mass of the comonomer and the crosslinking agent; (4) The viscosity of the prepolymer slurry at 25°C is 500-1000 cp; (5) In the photopretreatment and the photocuring, the wavelength of light is independently selected from 200 to 450 nm; (6) The prepolymer slurry does not contain solvent.

8. A polymer adhesive film for battery interfaces, characterized in that, Prepared by the preparation method according to any one of claims 1 to 7; The thickness of the polymer adhesive film used for the battery interface is 1–30 μm.

9. A solid-state battery, characterized in that, Includes the polymer adhesive film for battery interfaces as described in claim 8.

10. The solid-state battery according to claim 9, characterized in that, The battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, wherein the solid electrolyte layer is disposed between the positive electrode and the negative electrode; a polymer adhesive film for the battery interface is disposed between the positive electrode and the solid electrolyte layer, and / or between the negative electrode and the solid electrolyte layer.

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