Easy-peeling coating for lithium battery solid electrolyte membrane, and preparation method and application thereof

Abstract

This invention provides an easy-peel coating for solid electrolyte membranes in lithium batteries, its preparation method, and its application, relating to the field of lithium battery technology. The easy-peel coating is composed of poly(N-isopropylacrylamide), a binder, glycidyl methacrylate, and inorganic fillers; wherein the binder is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyisobutylene, and polyimide. In this invention, glycidyl methacrylate promotes the formation of a homogeneous dispersion system between poly(N-isopropylacrylamide) and the binder in an anhydrous organic solvent; after the coating is applied to a copper foil substrate, it exhibits a hydrophobic state at the drying temperature of the lithium battery slurry, providing strong interfacial anchoring and ensuring a smooth film formation without curling; however, when cooled to room temperature, the poly(N-isopropylacrylamide) undergoes hydrophilic swelling, achieving controllable peeling of the solid electrolyte membrane of the lithium battery without tearing or curling.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to an easy-peel coating for solid electrolyte membranes in lithium batteries, its preparation method, and its application. Background Technology

[0002] One of the key technologies for all-solid-state lithium batteries is the preparation of solid electrolyte membranes, which typically employs a casting coating process: lithium battery powder, binder, and solvent are mixed into a slurry, which is then uniformly coated onto a substrate. After the slurry dries to form a film, the electrolyte membrane is peeled off from the substrate for subsequent manufacturing.

[0003] However, existing lithium-ion battery solid electrolyte membrane peeling processes may encounter problems such as tearing, stretching deformation, and breakage, directly impacting yield and quality. Therefore, the peeling process is a critical step restricting continuous production and yield. Current research mainly focuses on the composition and preparation methods of the lithium-ion battery solid electrolyte membrane itself, without addressing the yield and quality issues in the peeling process.

[0004] Therefore, it is both necessary and urgent to develop an easy-peel coating that can achieve complete and low-damage peeling at room temperature while ensuring the quality of the solid electrolyte membrane in lithium batteries.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first objective of this invention is to provide an easy-peel coating for lithium-ion battery solid electrolyte membranes. The easy-peel coating can achieve strong interfacial anchoring at the film-forming temperature to ensure smooth film formation, and at the same time, it can trigger hydrophilic swelling of poly(N-isopropylacrylamide) at room temperature to significantly reduce interfacial adhesion, thereby enabling controllable peeling on copper foil substrates and ensuring that the peeling surface is stably positioned between the coating and the lithium-ion battery solid electrolyte membrane.

[0007] A second objective of this invention is to provide a method for preparing an easily peelable coating.

[0008] A third objective of this invention is to provide an application of an easy-to-peel coating.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The present invention provides an easy-peel coating for solid electrolyte membranes of lithium batteries, the easy-peel coating comprising: poly(N-isopropylacrylamide) (PNIPAM), binder, glycidyl methacrylate (GMA) and inorganic filler; The adhesive is selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyisobutylene (PIB), and polyimide (PI).

[0010] Furthermore, by parts by weight, the coating comprises: 10-20 parts of poly(N-isopropylacrylamide), 10-20 parts of binder, 2-4 parts of glycidyl methacrylate, and 65-75 parts of inorganic filler.

[0011] Furthermore, the substrate for preparing the lithium battery solid electrolyte membrane is copper foil.

[0012] Furthermore, the thickness of the copper foil is 10~30μm.

[0013] Furthermore, the inorganic filler is NMC powder with a particle size D. 50 The thickness is 5~10μm; The present invention provides a method for preparing the above-mentioned easy-peel coating, the method comprising: (a) Poly-N-isopropylacrylamide, binder and glycidyl methacrylate are mixed in a slurry solvent to form a homogeneous solution; (b) Add inorganic filler to the homogeneous solution and disperse it evenly to obtain a coating slurry; Furthermore, the slurry solvent is selected from at least one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

[0014] Preferably, the solid content of the slurry solvent is 20-40%.

[0015] Furthermore, the mixing in (a) is carried out under stirring conditions, wherein the stirring temperature is 20~40℃ and the stirring time is 1~3 hours.

[0016] Furthermore, the present invention also includes step (c) of preparing an easy-peel coating using the above-mentioned easy-peel coating material, as follows: (c) Apply the coating slurry obtained in step (b) onto the lithium battery solid electrolyte membrane substrate and dry it to obtain an easy-to-peel coating.

[0017] Furthermore, the drying temperature in (c) is 50~80℃, and the drying time is 5~30min.

[0018] Furthermore, the thickness of the coating after drying (c) ranges from 20µm to 50µm.

[0019] This invention provides the application of the above-mentioned easy-peel coating in the casting coating of solid electrolyte membranes for lithium batteries.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides an easy-peel coating for lithium-ion battery solid electrolyte membranes. The easy-peel coating introduces a composite system of poly(N-isopropylacrylamide) and a binder, and utilizes glycidyl methacrylate to achieve homogeneous dispersion of the two in anhydrous organic solvents. This allows the coating to have good interfacial anchoring ability at the drying temperature of the lithium-ion battery slurry, ensuring a smooth and curl-free film formation process. At room temperature, it significantly reduces the interfacial adhesion between the coating and the lithium-ion battery solid electrolyte membrane, thereby achieving complete, tear-free, and curl-free controllable peeling of the lithium-ion battery solid electrolyte membrane. Simultaneously, when this coating is applied to a high surface energy metal substrate, it ensures that the peeling surface stably occurs between the coating and the lithium-ion battery solid electrolyte membrane, preventing the coating from detaching from the substrate.

[0021] This invention provides a method for preparing an easy-to-peel coating. The method involves first mixing poly(N-isopropylacrylamide), a binder, and glycidyl methacrylate in a slurry solvent to form a homogeneous solution. This ensures effective interaction between the two components at the molecular scale, thereby allowing the subsequently added inorganic filler to be uniformly dispersed, resulting in a coating slurry with good stability. This process avoids precipitation or agglomeration caused by poor compatibility between components, ensuring the structural uniformity and interfacial performance consistency of the obtained coating. This, in turn, supports the smoothness of the lithium battery solid electrolyte membrane during the coating and film formation stage and its integrity during the peeling stage.

[0022] The easy-peel coating provided by this invention can be widely used in the casting coating of solid electrolyte membranes for lithium batteries. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the structure of the lithium battery solid electrolyte membrane, easy-to-peel coating, and substrate provided in Embodiment 1 of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0026] According to one aspect of the present invention, an easy-peel coating for a solid electrolyte membrane of a lithium battery, the easy-peel coating comprising: poly(N-isopropylacrylamide) (PNIPAM), a binder, glycidyl methacrylate (GMA), and an inorganic filler; The adhesive is selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyisobutylene (PIB), and polyimide (PI).

[0027] This invention provides an easy-peel coating for lithium-ion battery solid electrolyte membranes. The easy-peel coating introduces a composite system of poly(N-isopropylacrylamide) and a binder, and utilizes glycidyl methacrylate to achieve homogeneous dispersion of the two in anhydrous organic solvents. This allows the coating to have good interfacial anchoring ability at the drying temperature of the lithium-ion battery slurry, ensuring a smooth and curl-free film formation process. At room temperature, it significantly reduces the interfacial adhesion between the coating and the lithium-ion battery solid electrolyte membrane, thereby achieving complete, tear-free, and curl-free controllable peeling of the lithium-ion battery solid electrolyte membrane. Simultaneously, when this coating is applied to a high surface energy metal substrate, it ensures that the peeling surface stably occurs between the coating and the lithium-ion battery solid electrolyte membrane, preventing the coating from detaching from the substrate.

[0028] It should be noted that the number average molecular weight of the poly(N-isopropylacrylamide) is 30,000 to 50,000. Poly(N-isopropylacrylamide) (PNIPAM) is a thermoresponsive hydrogel. At the coating drying temperature, it is hydrophobic and adheres well to the solid electrolyte membrane of lithium batteries. However, when the temperature drops to room temperature or lower, it becomes hydrophilic and swollen, and the interfacial adhesion decreases sharply, thus achieving easy peeling. At the same time, poly(N-isopropylacrylamide) is not miscible with other binders at low concentrations (≤30%), and the mixed solution exhibits a layered state. Simply mixing poly(N-isopropylacrylamide) and PVDF is not usable. To address the aforementioned issues, this invention utilizes glycidyl methacrylate as a co-solvent. Its epoxy groups exhibit physical affinity with the amide groups of poly(N-isopropylacrylamide), while its side chain polarity allows for miscibility with PVDF. Only a small amount of glycidyl methacrylate is needed to achieve homogeneous blending of poly(N-isopropylacrylamide) and PVDF, thereby effectively realizing the miscibility of poly(N-isopropylacrylamide) and the binder at low concentrations.

[0029] In a preferred embodiment of the present invention, the coating comprises, by weight parts: 10-20 parts of poly(N-isopropylacrylamide), 10-20 parts of binder, 2-4 parts of glycidyl methacrylate, and 65-75 parts of inorganic filler; In the preferred embodiment described above, the mass fraction of polyN-isopropylacrylamide in the coating is 10 to 20 parts, for example, it can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts or 20 parts, or any continuous value between 10 and 20 parts; In the preferred embodiment described above, the mass fraction of the adhesive in the coating is 10 to 20 parts, for example, it can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts or 20 parts, or any continuous value between 10 and 20 parts; In the preferred embodiment described above, the mass fraction of glycidyl methacrylate in the coating is 2 to 4 parts, for example, it can be 2 parts, 3 parts or 4 parts, or any continuous value between 2 and 4 parts. In the preferred embodiment described above, the inorganic filler in the coating is 65 to 75 parts by mass, for example, 65, 67, 69, 71, 73 or 75 parts, or any continuous value between 65 and 75 parts.

[0030] In a preferred embodiment, the present invention controls the mass fractions of poly(N-isopropylacrylamide), binder, glycidyl methacrylate, and inorganic filler within the aforementioned range, thereby enabling the coating to possess both good film-forming stability and controllable interfacial peeling. Specifically, the synergistic effect of poly(N-isopropylacrylamide) and glycidyl methacrylate is effectively utilized, ensuring that the coating exhibits suitable adhesion strength to both the substrate and the lithium-ion battery solid electrolyte membrane during the lithium-ion battery slurry drying process. The binder provides the necessary film-forming effect and mechanical strength, preventing coating cracking or powdering. The inorganic filler is uniformly dispersed in the coating, improving the wetting and spreading performance of the solid electrolyte slurry coating on its surface, and partially remaining on the surface of the lithium-ion battery solid electrolyte membrane after peeling, which is beneficial for subsequent interfacial compatibility with the cathode material.

[0031] In a preferred embodiment of the present invention, the substrate for preparing the lithium battery solid electrolyte membrane is copper foil.

[0032] In a preferred embodiment, the present invention uses copper foil as the substrate for preparing the lithium battery solid electrolyte membrane. This ensures a sufficiently strong interfacial bond between the easy-peel coating and the copper foil, thereby maintaining the integrity of the easy-peel coating structure and preventing it from falling off during the coating, drying, and film formation processes of the solid electrolyte slurry. Simultaneously, the strong bond between the easy-peel coating and the copper foil is reasonably matched with the relatively weak adhesion between the easy-peel coating and the lithium battery solid electrolyte membrane (the high surface energy of the copper foil results in a large adhesion between it and the easy-peel coating, while the small adhesion between the lithium battery solid electrolyte membrane and the easy-peel coating results in a small adhesion). This ensures that the separation surface during the peeling process stably occurs between the coating and the lithium battery solid electrolyte membrane, preventing the coating from being peeled off from the substrate along with the lithium battery solid electrolyte membrane, thus guaranteeing the reliability and repeatability of the peeling operation.

[0033] In the preferred embodiment described above, the thickness of the copper foil is 10~30μm; for example, it can be 10μm, 12μm, 15μm, 18μm, 20μm, 25μm or 30μm, or any continuous value within the range of 10~30μm.

[0034] In a preferred embodiment of the present invention, the inorganic filler is NMC powder with a particle size D50 of 5~10μm; for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm or 10μm, or any continuous value in the range of 5~10μm.

[0035] In a preferred embodiment, this invention uses NMC powder with a particle size D50 of 5-10 μm as an inorganic filler. This allows the coating surface to form a moderately rough micron-scale structure, which is beneficial for the uniform wetting and spreading of lithium battery slurry, improving film continuity. Simultaneously, NMC powder within this particle size range can remain microscopically at the interface between the lithium battery solid electrolyte membrane and the coating during the peeling process, enhancing the chemical compatibility of the lithium battery solid electrolyte membrane surface after peeling, and facilitating the formation of a stable interface with the cathode material during subsequent battery assembly. Using other powders results in poor system compatibility and can easily cause system compatibility anomalies during battery fabrication.

[0036] According to one aspect of the present invention, a method for preparing the above-mentioned easy-peel coating, the method comprising: (a) Poly-N-isopropylacrylamide, binder and glycidyl methacrylate are stirred in a slurry solvent to form a homogeneous solution; (b) Add inorganic filler to the homogeneous solution and disperse it evenly to obtain an easy-to-peel coating.

[0037] This invention provides a method for preparing an easy-to-peel coating. The method involves first mixing poly(N-isopropylacrylamide), a binder, and glycidyl methacrylate in a slurry solvent to form a homogeneous solution. This ensures effective interaction between the two components at the molecular scale, thereby allowing the subsequently added inorganic filler to be uniformly dispersed, resulting in a coating slurry with good stability. This process avoids precipitation or agglomeration caused by poor compatibility between components, ensuring the structural uniformity and interfacial performance consistency of the obtained coating. This, in turn, supports the smoothness of the lithium battery solid electrolyte membrane during the coating and film formation stage and its integrity during the peeling stage.

[0038] In a preferred embodiment of the present invention, the slurry solvent is selected from at least one of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and N,N-dimethylformamide (DMF).

[0039] In a preferred embodiment, the present invention uses N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), or N,N-dimethylformamide (DMF) as the slurry solvent, which can effectively dissolve poly(N-isopropylacrylamide), binder, and glycidyl methacrylate to form a stable and homogeneous solution system. During the subsequent drying process, the solvent is fully and controllably evaporated, avoiding residual solvent from causing pollution or side reactions to the lithium battery electrolyte system, thereby ensuring the coating film quality and the electrochemical stability of the lithium battery solid electrolyte membrane.

[0040] Preferably, the solid content of the dispersed, easily peelable coating (b) is 20-40 wt%, for example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt% or 40 wt%, or any continuous value between 20 and 40 wt%.

[0041] In a preferred embodiment of the present invention, the stirring temperature in (a) is 20~40°C and the stirring time is 1~3 hours; In the preferred embodiment described above, the stirring temperature is 20~40℃, for example, it can be 20℃, 25℃, 30℃, 35℃ or 40℃, or any continuous value between 20~40℃; In the preferred embodiment described above, the stirring time is 1 to 3 hours, for example, it can be 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, or any continuous value between 1 and 3 hours.

[0042] In a preferred embodiment, the present invention involves stirring poly(N-isopropylacrylamide), binder, and glycidyl methacrylate at 20-40°C for 1-3 hours. This facilitates the full wetting, dispersion, and interaction of the components in the solvent, promoting the effective establishment of the bridging effect between GMA and PNIPAM and the binder. This results in a uniform and stable solution system, providing a reliable guarantee for the uniform dispersion of subsequent inorganic fillers and the structural consistency of the final coating.

[0043] In a preferred embodiment of the present invention, the present invention further includes step (c) of preparing an easy-peel coating using the above-described easy-peel coating material, as follows: (c) Apply the coating slurry obtained in step (b) onto the lithium battery solid electrolyte membrane substrate and dry it to obtain an easy-to-peel coating.

[0044] In the preferred embodiment above, the drying temperature is 50~80℃, for example, it can be 50℃, 60℃, 70℃ or 80℃, or any continuous value between 50~80℃; In the preferred embodiment described above, the drying time is 5 to 30 minutes, for example, it can be 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, or any continuous value between 5 and 30 minutes.

[0045] In a preferred embodiment, the present invention dries the coating slurry at 50-80°C for 5-30 minutes, allowing the solvent to evaporate fully and uniformly, forming a dense and structurally stable dried coating. This avoids solvent residue affecting the stability of the lithium battery system due to excessively low temperature or short drying time, while also preventing polymer thermal degradation or interfacial side reactions caused by excessively high temperature or long drying time. This ensures the functional integrity and reliability of the coating during subsequent lithium battery slurry coating and peeling processes. Furthermore, the peeling coating of the present invention uses poly(N-isopropylacrylamide) as the main binder, exhibiting high adhesion during high-temperature baking, ensuring that the lithium battery slurry adheres to the easily peelable coating during the drying and film formation process, preventing curling and uneven film formation. At room temperature, the peeling force decreases, facilitating the peeling of the lithium battery solid electrolyte membrane.

[0046] In a preferred embodiment of the present invention, the thickness of the coating after drying (c) is in the range of 20~50μm; for example, it can be 20μm, 25μm, 30μm, 35μm, 40μm, 45μm or 50μm, or any continuous value in the range of 20~50μm.

[0047] In a preferred embodiment, the present invention controls the thickness of the peeled coating after drying to within the range of 20μm to 50μm, which enables the coating to have both sufficient mechanical support strength and good flexible deformation ability, maintain structural integrity and prevent cracking or accumulation during the coating and drying process of lithium battery slurry, and effectively release interfacial stress during peeling, thereby ensuring the integrity and surface smoothness of the lithium battery solid electrolyte membrane peeling.

[0048] According to one aspect of the present invention, the above-mentioned easy-peel coating is used in the casting coating of solid electrolyte membranes for lithium batteries.

[0049] The easy-peel coating provided by this invention can be widely used in the casting coating of solid electrolyte membranes for lithium batteries.

[0050] The technical solution of the present invention will be further described below with reference to the embodiments.

[0051] Example 1 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh the following raw materials according to the mass fractions:

[0052] The NMC powder is lithium nickel cobalt manganese oxide (LiNi). x Co y Mn z O2, x+y+z=1), the particle size D50 of the NMC powder is 5~10μm; The number-average molecular weight of the poly-N-isopropylacrylamide is 30,000 to 50,000.

[0053] (2) PVDF, PNIPAM and GMA are added sequentially to N-methylpyrrolidone (NMP) solvent and stirred at 500 rpm for 2 hours at 25°C until a homogeneous and transparent solution is formed; then, all of the above NMC powder is added to the solution and stirred at 800 rpm for 1 hour at 25°C to obtain an easy-peel coating with a solid content of 30 wt%.

[0054] 2. Preparation of easy-to-peel coating: The coating slurry obtained in step 1 was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was then placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The coating thickness was measured to be 8.3 μm using a thin film thickness gauge.

[0055] The thickness test was performed using a Mahr C1202HR thin film thickness gauge from Germany, in accordance with the applicable standards. The following examples and comparative examples are the same.

[0056] 3. Preparation and peeling of solid electrolyte membrane for lithium batteries: Li6PS5Cl, an active material for lithium batteries, was mixed with styrene-ethylene-butene-styrene block copolymer (SEBS) at a mass ratio of 85:15 to obtain mixture C. Mixture C was added to xylene solvent and stirred at room temperature for 4 hours to prepare lithium battery slurry D with a solid content of 50 wt%. Figure 1 This is a schematic diagram of the structure of the lithium battery solid electrolyte membrane, easy-to-peel coating, and substrate provided in this embodiment.

[0057] The lithium battery slurry D is coated on the surface of the easily peelable coating obtained in step (2) and dried at 60°C for 12 hours. After it is completely dried, it is gently peeled off along the edge of the copper foil at room temperature (25°C). The lithium battery solid electrolyte membrane can be peeled off completely, without tearing or curling, from the surface of the easily peelable coating, resulting in a lithium battery solid electrolyte membrane with a smooth surface and uniform thickness.

[0058] Example 2 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 10 parts of polyvinylidene fluoride (PVDF), 18 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); wherein, the NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step 1 was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a blade coating method. The coated copper foil was then placed in a forced-air drying oven and dried at 60°C for 15 min to obtain a dry, easily peelable coating. The thickness of the coating was measured to be 8.6 μm using a thin film thickness gauge. (3) Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0059] Example 3 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 17 parts of polyvinylidene fluoride (PVDF), 10 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); wherein, the NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.4 μm by a thin film thickness gauge.

[0060] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0061] Example 4 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 65 parts of NMC powder, 17 parts of polyvinylidene fluoride (PVDF), 15 parts of poly(N-isopropylacrylamide) (PNIPAM), and 3 parts of glycidyl methacrylate (GMA); wherein, the NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step 1 was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was then placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.6 μm using a thin film thickness gauge.

[0062] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0063] Example 5 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 65 parts of NMC powder, 15 parts of polyvinylidene fluoride (PVDF), 17 parts of poly(N-isopropylacrylamide) (PNIPAM), and 3 parts of glycidyl methacrylate (GMA); wherein, the NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step 1 was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was then placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.3 μm using a thin film thickness gauge.

[0064] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0065] Example 6 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 73 parts of NMC powder, 10 parts of polyvinylidene fluoride (PVDF), 15 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); wherein, the NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step 1 was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was then placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.8 μm using a thin film thickness gauge.

[0066] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0067] Example 7 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 75 parts of NMC powder, 20 parts of polyvinylidene fluoride (PVDF), 20 parts of poly(N-isopropylacrylamide) (PNIPAM), and 4 parts of glycidyl methacrylate (GMA); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.5 μm by a thin film thickness gauge.

[0068] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0069] Example 8 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 5 parts of polyvinylidene fluoride (PVDF), 23 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.2 μm by a thin film thickness gauge.

[0070] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0071] Example 9 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 60 parts of NMC powder, 20 parts of polyvinylidene fluoride (PVDF), 19 parts of poly(N-isopropylacrylamide) (PNIPAM), and 1 part of glycidyl methacrylate (GMA); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method; the coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain the dried easy-peel coating; the thickness of the coating was measured to be 8.4 μm by a thin film thickness gauge.

[0072] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0073] Example 10 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 80 parts of NMC powder, 8 parts of polyvinylidene fluoride (PVDF), 10 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain the dried easy-peel coating. The thickness of the coating was measured to be 8.1 μm by a thin film thickness gauge.

[0074] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0075] Comparative Example 1: Lithium battery slurry was directly coated onto aluminum foil without using an easy-peel coating. A method for preparing a solid electrolyte membrane for lithium batteries specifically includes the following steps: The lithium battery slurry D (prepared by dispersing Li6PS5Cl and SEBS in xylene at a mass ratio of 85:15, with a solid content of 50 wt%) was directly coated onto a copper foil substrate with a thickness of 12 μm; the coated aluminum foil was placed in a forced-air drying oven and dried at 60°C for 12 hours. Comparative Example 2: Lithium battery slurry was directly applied to PET material without using an easy-peel coating. A method for preparing a solid electrolyte membrane for lithium batteries specifically includes the following steps: The lithium battery slurry D (prepared by dispersing Li6PS5Cl and SEBS in xylene at a mass ratio of 85:15, with a solid content of 50 wt%) was directly coated onto a polyethylene terephthalate (PET) film substrate with a thickness of 12 μm. The coated PET film was placed in a forced-air drying oven and dried at 60°C for 12 hours. Comparative Example 3 did not contain glycidyl methacrylate (GMA), and all other procedures were carried out as in Example 1. An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 14 parts of polyvinylidene fluoride (PVDF), and 14 parts of poly(N-isopropylacrylamide) (PNIPAM); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 7.9 μm by a thin film thickness gauge.

[0076] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0077] Comparative Example 4 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 14 parts of polyvinylidene fluoride (PVDF), 14 parts of polyethylene oxide (PEO), and 2 parts of glycidyl methacrylate (GMA); The polyethylene oxide (PEO) is designated as Shanghai Liansheng Chemical PEO-10, with a molecular weight of 100,000.

[0078] The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.7 μm by a thin film thickness gauge.

[0079] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0080] Comparative Example 5 An easy-peel coating for a solid electrolyte membrane in a lithium battery, the method for preparing the coating comprising: 1. Preparation of easy-peel coating: (1) Weigh out 70 parts of NMC powder, 14 parts of PMMA (Guangzhou Rongdong New Material 8552), 14 parts of poly(N-isopropylacrylamide) (PNIPAM), and 2 parts of glycidyl methacrylate (GMA); The NMC powder is the same as in Example 1; (2) Same as Example 1; 2. Preparation of easy-to-peel coating: The coating slurry obtained in step (1) was uniformly coated onto a copper foil substrate with a thickness of 12 μm using a doctor blade coating method. The coated copper foil was placed in a forced-air drying oven and dried at 60°C for 15 min to obtain an easy-to-peel coating after drying. The thickness of the coating was measured to be 8.3 μm by a thin film thickness gauge.

[0081] 3. Preparation and peeling of solid electrolyte membrane for lithium battery: Same as in Example 1.

[0082] Experimental Example 1 To demonstrate the technical effectiveness of the easily peelable coating of the present invention, Examples 1-7 and Comparative Examples 1-6 were tested. The specific testing methods are as follows: Peel integrity evaluation: The test was conducted according to the method of national standard GB / T 2792-2014, using a 180° peel method, and the width of the test sample was 30mm; the pass / fail criteria were "whether it can be completely peeled off, without tearing, without curling, and without local residue". Peel force determination: Same as the above standard (GB / T 2792-2014), use an electronic tensile testing machine to perform 180° peel test, peel rate 300 mm / min, record the average peel force value in the stable peel stage, the unit is N / mm; Thickness consistency evaluation: Using a Mahr C1202HR thin film thickness gauge from Germany, 30 points were uniformly selected within a 5 mm × 10 mm area of ​​the peeled lithium battery solid electrolyte film according to the equipment operation standard for thickness measurement; the ratio of the standard deviation of thickness (σ) to the average thickness (μ) (σ / μ) was used as the "thickness consistency index". The smaller the value, the more uniform the film thickness and the higher the film quality.

[0083] See Tables 1 and 2 for specific test results.

[0084] Table 1:

[0085] Table 2:

[0086] As can be seen from the test results in Tables 1 and 2 above, Examples 1 to 7 all achieved qualified peel integrity (no tearing, no curling, no local residue), the average peel force was stable in the small range of 1.7 to 2.2 N / m, and the thickness consistency index was better than 5%, which confirms that the easy-peel coating of the present invention can stably achieve the unity of film flatness and peel controllability on copper foil substrate.

[0087] Example 8 uses an implementation method with 23 parts PNIPAM and 5 parts binder. The binder content is too low, and the adhesion of PNIPAM at room temperature is also too low, resulting in insufficient strength of the easy-peel coating itself. After it is completely dry, an attempt was made to gently peel off the lithium battery solid electrolyte membrane along the edge of the copper film at room temperature (25°C). It was found that a small amount of the easy-peel coating adhered to the lithium battery solid electrolyte membrane, affecting the purity of the electrolyte membrane. This resulted in large fluctuations in the thickness of the electrolyte membrane, which did not meet the requirements for use.

[0088] Example 9 uses 60 parts of NMC filler and 1 part of GMA. The amount of GMA co-solvent is too small, which cannot fully and uniformly dissolve the binder and PNIPAM components in the system. After complete drying, an attempt was made to gently peel off the lithium battery solid electrolyte membrane along the edge of the copper film at room temperature (25°C). It was found that the local peeling force was too large or too small, which caused the lithium battery membrane thickness to be stretched unevenly, resulting in less uniformity and affecting the quality and performance of the electrolyte membrane.

[0089] Example 10 uses 80 parts of NMC filler and 8 parts of binder. The proportion of powder is too high and the proportion of binder is too low, resulting in insufficient overall strength of the easy-to-peel coating. After complete drying, an attempt was made to gently peel off the lithium battery solid electrolyte membrane along the edge of the copper film at room temperature (25°C). It was found that the easy-to-peel coating powder adhered to the lithium battery solid electrolyte membrane, affecting the quality and performance of the electrolyte membrane.

[0090] In contrast, in Comparative Example 1, the lithium battery slurry was directly coated onto the aluminum foil without using an easy-peel coating. After it was completely dried, an attempt was made to gently peel off the lithium battery solid electrolyte membrane along the edge of the copper foil at room temperature (25°C). It was found that the lithium battery solid electrolyte membrane was severely adhered to the copper foil surface and could not be completely peeled off. When forcibly peeled off, large-area tearing, edge curling, and local hole collapse occurred. The resulting sample could not be used as a complete and continuous lithium battery solid electrolyte membrane.

[0091] Comparative Example 2 describes an implementation method where lithium battery slurry is directly coated onto a PET film without using an easy-peel coating. During the coating process, the solid electrolyte slurry from the lithium battery has poor wetting affinity with the PET film. At the same time, the PET substrate undergoes significant shrinkage during the coating and drying process, resulting in uneven film thickness of the lithium battery electrolyte film. After complete drying, an attempt was made to gently peel off the solid electrolyte film along the edge of the PET film at room temperature (25°C). It was found that the electrolyte film thickness fluctuated greatly, and the film surface texture was uneven, which did not meet the requirements for use.

[0092] In Comparative Example 3, the implementation without the co-solvent GMA resulted in the binder and release agent being immiscible, leading to uneven distribution of peel force at the coating layer level. After complete drying, an attempt was made to gently peel the lithium battery solid electrolyte membrane along the edge of the copper foil at room temperature (25°C). It was found that the local peel force was too large or too small, causing the lithium battery membrane thickness to be stretched unevenly, reducing uniformity and affecting the quality and performance of the electrolyte membrane. This resulted in deformation and uneven thickness of the lithium battery membrane layer after peeling, failing to meet the usage requirements.

[0093] Comparative Example 4, which did not use poly-N-isopropylacrylamide, could not adjust the peel force to be smaller at room temperature. Attempts were made to peel off the lithium battery solid electrolyte membrane at room temperature (25°C). It was found that the lithium battery solid electrolyte membrane was severely adhered to the easily peelable coating surface. When forcibly peeled off, the coating was torn and the edges curled. The resulting sample could not be used as a complete and continuous lithium battery solid electrolyte membrane.

[0094] Comparative Example 5 uses polymethyl methacrylate (PMMA) instead of PVDF. In actual application, the co-solvent glycidyl methacrylate (GMA) in this system cannot make PMMA and PNIPAM co-fused, resulting in uneven distribution of coating peel force. Attempts were made to peel off the solid electrolyte membrane of the lithium battery at room temperature (25°C). In some areas, the membrane layer was stretched and deformed, and the thickness fluctuated greatly, causing the electrolyte membrane to fail to meet the application requirements.

[0095] 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. An easy-peel coating for solid electrolyte membranes in lithium batteries, characterized in that, The easy-peel coating comprises: poly(N-isopropylacrylamide), binder, glycidyl methacrylate, and inorganic filler; The adhesive is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyisobutylene, and polyimide.

2. The easy-peel coating according to claim 1, characterized in that, By weight parts, the easy-peel coating comprises: 10-20 parts of poly(N-isopropylacrylamide), 10-20 parts of binder, 2-4 parts of glycidyl methacrylate, and 65-75 parts of inorganic filler.

3. The easy-peel coating according to claim 1, characterized in that, The substrate for preparing the lithium battery solid electrolyte membrane is copper foil.

4. The easy-peel coating according to claim 3, characterized in that, The thickness of the copper foil is 10~30 μm.

5. The easy-peel coating according to claim 1, characterized in that, The inorganic filler is NMC powder, and the particle size D50 of the NMC powder is 5~10μm.

6. A method for preparing an easy-peel coating according to any one of claims 1 to 5, characterized in that, The preparation method includes: (a) Poly-N-isopropylacrylamide, binder and glycidyl methacrylate are stirred in a slurry solvent to form a homogeneous solution; (b) Add inorganic filler to the homogeneous solution and disperse it evenly to obtain an easy-to-peel coating.

7. The method for preparing the easy-peel coating according to claim 6, characterized in that, The slurry solvent in (a) is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide and N,N-dimethylformamide.

8. The method for preparing the easy-peel coating according to claim 6, characterized in that, The stirring temperature in (a) is 20~40℃ and the stirring time is 1~3 h.

9. The method for preparing the easy-peel coating according to claim 6, characterized in that, The solid content of the easily peelable coating after dispersion (b) is 20~40wt%.

10. The application of an easy-peel coating according to any one of claims 1 to 4 in the casting coating of solid electrolyte membranes for lithium batteries.

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