Release film and oxide solid electrolyte film

Abstract

This invention relates to a release film for an oxide solid electrolyte membrane, the release film comprising a release substrate layer and an EVA functionalized coating coated on the surface of the release substrate layer, wherein the vinyl acetate content of the EVA functionalized coating is between 10% and 50%. Furthermore, this invention also provides an oxide solid electrolyte membrane comprising a release film, an oxide solid electrolyte membrane body, and a carrier as described above, wherein the oxide solid electrolyte membrane body is located between the release film and the carrier, and the release film is bonded to the oxide solid electrolyte membrane body via the EVA functionalized coating.

Description

Technical Field

[0001] This invention relates to the field of solid electrolytes, and more particularly to a release membrane and an oxide solid electrolyte membrane. Background Technology

[0002] Compared to traditional liquid lithium-ion batteries, all-solid-state lithium-ion batteries offer superior safety, high energy density, and good cycle performance, attracting increasing attention in recent years. Solid-state electrolytes, as the core material in all-solid-state batteries, directly determine their performance. Oxide solid-state electrolytes possess numerous advantages, including high ionic conductivity, a wide electrochemical window, high mechanical strength, and stability to air and metallic lithium, making them highly promising solid-state electrolytes.

[0003] However, during the preparation of oxide solid electrolyte membranes, a release film is typically applied to the oxide solid electrolyte membrane to protect it. Generally, the release film is an adhesive such as acrylic, polyurethane, or silicone coated onto a polyethylene terephthalate (PET) film substrate. However, when the release film needs to be detached from the oxide solid electrolyte membrane, it often causes structural damage to the oxide solid electrolyte membrane and difficulties in release. Summary of the Invention

[0004] In view of this, it is indeed necessary to provide a release film for an oxide solid electrolyte membrane and an oxide solid electrolyte membrane.

[0005] A release film for an oxide solid electrolyte membrane, the release film comprising a release substrate layer and an EVA functionalized coating coated on the surface of the release substrate layer, wherein the vinyl acetate content of the EVA functionalized coating is between 10% and 50%.

[0006] An oxide solid electrolyte membrane includes a release film of a solid electrolyte membrane as described above, an oxide solid electrolyte membrane body, and a carrier. The oxide solid electrolyte membrane body is located between the release film and the carrier, and the release film is bonded to the oxide solid electrolyte membrane body through the EVA functionalized coating.

[0007] Compared with existing technologies, the release film of the oxide solid electrolyte membrane provided by this invention includes an EVA functionalized coating. Therefore, the release film and the solid electrolyte membrane have a matching adhesive force, ensuring complete adhesion during the bonding process and matching dyne values. Gases will not enter between the release film and the solid electrolyte membrane during the manufacturing process, causing appearance abnormalities and effectively protecting the solid electrolyte membrane. Furthermore, the release film provided by this invention does not damage the surface of the solid electrolyte membrane when detached, making release easy. When the solid electrolyte membrane is used for full-cell assembly, it has no impact on the battery's electrical performance. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the structure of the oxide solid electrolyte membrane product provided by the present invention.

[0009] Figure 2 This is a schematic diagram of the release membrane structure of the oxide solid electrolyte membrane provided by the present invention.

[0010] Figure 3 This is a schematic diagram of the structure in which the release film and the solid electrolyte membrane body are bonded together, as provided by the present invention.

[0011] Figure 4 This is a schematic diagram of the structure of the release film and the solid electrolyte membrane body of the solid electrolyte membrane provided by the present invention from another angle.

[0012] Figure 5 This is a schematic diagram of the structure of a release membrane without an EVA functionalized coating bonded to a solid electrolyte membrane.

[0013] Figure 6 This is a schematic diagram of another angle showing the bonding of a release film without an EVA functionalized coating to a solid electrolyte membrane.

[0014] Figure 7 SEM image of the surface of a solid electrolyte membrane without a release membrane.

[0015] Figure 8 SEM image of the surface of the solid electrolyte membrane after peeling off the release membrane of the present invention with an adhesion of 1 g / inch.

[0016] Figure 9 SEM image of the surface of the solid electrolyte membrane after peeling off the release film of the present invention with an adhesion of 15 g / inch.

[0017] Figure 10 This is a schematic diagram of the carrier material for the oxide solid electrolyte membrane provided by the present invention.

[0018] Figure 11This is a schematic diagram of the structure of an oxide solid electrolyte membrane prepared by the RTR (roll-to-roll) method provided by the present invention.

[0019] Figure 12 Electrical properties curves for full cell assembly of a solid electrolyte membrane without a release membrane.

[0020] Figure 13 The electrical properties of a release membrane with a 0.5 μm thick EVA functionalized coating are obtained after the solid electrolyte membrane is removed and a full cell is assembled.

[0021] Figure 14 The electrical properties of a release membrane with a 2.0 μm thick EVA functionalized coating bonded to a solid electrolyte membrane, followed by the removal of the solid electrolyte membrane for full cell assembly, are obtained.

[0022] Explanation of main component symbols

[0023] Release membrane of oxide solid electrolyte membrane 300

[0024] Release substrate layer 301

[0025] EVA functionalized coating 302

[0026] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0027] The release film and the oxide solid electrolyte membrane of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of this application belong. The terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the embodiments of this application.

[0029] Furthermore, the terminology used herein is for describing particular embodiments only and is not intended to limit the embodiments. Expressions used in the singular include plural expressions unless they have a clearly different meaning in the context. In this specification, the terms “comprising,” “having,” indicate the presence of the listed features, integrals, steps, operations, components, and / or constructions, and do not exclude the presence or addition of one or more features, integrals, steps, operations, components, constructions, and / or sets thereof.

[0030] Furthermore, the numerical values ​​stated herein are within the permissible deviation range for a specific value, determined by those skilled in the art taking into account errors related to the specific quantity being measured (e.g., limitations of the measurement system). For example, this may mean within one or more standard deviations relative to the stated value, or within ±20%, 10%, or 5%.

[0031] The technical solution of the present invention will be further described in detail below with reference to the specification, accompanying drawings and specific embodiments.

[0032] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of the finished oxide solid electrolyte membrane. The oxide solid electrolyte membrane 10, from bottom to top, comprises a carrier 100 (hereinafter referred to as the carrier), an oxide solid electrolyte membrane body 200, and a release membrane 300 (hereinafter referred to as the release membrane). The lower layer is the carrier 100, with a thickness of 120-130 μm; the middle layer is the oxide solid electrolyte membrane body 200, with a thickness of 20-50 μm; and the upper layer is the release membrane 300, with a thickness of 40.5-52 μm.

[0033] Please see Figure 2 , Figure 2 This is a schematic diagram of the release membrane structure of an oxide solid electrolyte membrane. The release membrane 300 includes a release substrate layer 301 and a functionalized coating 302 of ethylene-vinyl acetate copolymer (hereinafter referred to as EVA functionalized coating 302) coated on the surface of the release substrate layer. Because EVA exhibits different properties depending on the VA (vinyl acetate) content, such as resilience, flexibility, adhesion, rigidity, wear resistance, electrical insulation, solubility, stress resistance, cracking resistance, impact performance, etc., the VA (vinyl acetate) content of the EVA functionalized coating 302 used in this invention must be between 15% and 50%, preferably between 30% and 40%.

[0034] The release substrate layer 301 can be made of polymers such as polyethylene terephthalate (PET) film or polypropylene (PP), and its thickness is 40 μm to 50 μm. The surface of the release substrate layer 301 is coated with an EVA-functionalized coating 302 with adhesive strength of 1–15 g / inch. EVA is a hot-melt polymer material, and the EVA-functionalized coating slurry is 100% EVA, formed by simultaneous thermal extrusion with the release substrate layer 301. The adhesive strength of the EVA-functionalized coating 302 increases the adhesion between the release substrate layer 301 and the solid electrolyte membrane 200. Adhesion refers to the tight bonding between the release substrate layer 301 and the solid electrolyte membrane 200 through the EVA-functionalized coating 302 in a near-vacuum state.

[0035] Please refer to the table below. In the release film, the thicker the EVA functionalized coating, the greater its adhesion. The number of bubbles that penetrate between the release film 300 and the solid electrolyte membrane 200 and the appearance of the solid electrolyte membrane surface are shown in the table below.

[0036]

[0037]

[0038] As shown in the table above, when the thickness of the EVA functionalized coating 302 is between 0.5 μm and 2.0 μm, the adhesion of the release film 300 is suitable, no air bubbles are formed between the release film 300 and the solid electrolyte membrane 200, and the appearance of the solid electrolyte membrane surface is normal. That is, the release film 300 and the solid electrolyte membrane 200 are completely adhered during the bonding process. However, the coating process can be affected by slight differences in process parameters such as environment, equipment, and materials, which may cause some possible variables in the test results. Therefore, in this embodiment, the limiting condition of the EVA functionalized coating 302 must at least meet one of the following:

[0039] 1. The thickness of the EVA functionalized coating 302 is less than 0.5 μm and the adhesion test data is greater than or equal to 1 g / inch.

[0040] 2. The thickness of the EVA functionalized coating 302 is between 0.5μm and 2.0μm and / or the adhesion test data is between 1g / inch and 15g / inch.

[0041] 3. The thickness of the EVA functionalized coating 302 is greater than 2.0 μm and the adhesion test data is less than or equal to 15 g / inch.

[0042] In this embodiment, the preferred thickness range of the EVA functionalized coating 302 is 0.5 μm to 2.0 μm. Preferably, the optimal thickness of the EVA functionalized coating 302 is 0.5 μm. Due to the thinner thickness, the RTR roll winding length is longer for the same roll outer diameter.

[0043] For details, please see Figure 3 and Figure 4 Because the release film 300 has a matching adhesive force with the solid electrolyte membrane 200, it is completely adhered during the bonding process and the dyne values ​​are matched. Gas will not enter between the release film 300 and the solid electrolyte membrane 200 during the preparation process, causing abnormal appearance.

[0044] Please see Figure 5 and Figure 6 , Figure 5 and Figure 6 When a release film without an EVA functionalized coating 302 is bonded to a solid electrolyte membrane 200, insufficient adhesion can cause gas to seep into the space between the release film and the solid electrolyte membrane 200 during the bonding process due to unevenness between the materials, forming air bubbles. Since the air bubbles exist between the release film 300 and the solid electrolyte membrane 200, they are subsequently rolled into the roll, resulting in an abnormal appearance of the membrane surface.

[0045] Please see Figures 7 to 9 , Figure 7 SEM image of the surface of a solid electrolyte membrane without release membrane 300; Figure 8 SEM image of the surface of the solid electrolyte membrane after peeling off the release film 300 with an adhesion of 1 g / inch of the present invention; Figure 9 This is a SEM image of the surface of the solid electrolyte membrane after peeling off the release film 300 of the present invention, which has an adhesion strength of 15 g / inch. Comparing the three SEM images of the solid electrolyte membrane surface, there are essentially no differences, indicating that the release film 300 provided by the present invention does not damage the surface of the solid electrolyte membrane. Furthermore, even if the adhesion strength of the EVA functionalized coating 302 of the release film 300 is increased to a certain range, it will not damage the surface of the solid electrolyte membrane.

[0046] The following is a comparative analysis of the composition and properties of the release film provided by this invention and other release films. Please refer to the table below for details.

[0047]

[0048] As can be seen from the table above, the release film PE01 provided by the present invention has superior characteristics.

[0049] The oxide solid electrolyte membrane 200 can be a lithium lanthanum zirconium oxide (LLZO) solid electrolyte membrane, a lithium titanium aluminum phosphate (LATP) solid electrolyte membrane, a lithium germanium aluminum phosphate (LAGP) solid electrolyte membrane, or a lithium lanthanum titanate (LLTO) solid electrolyte membrane, etc., and is not limited to these, and can also be other solid electrolyte membranes.

[0050] Please see Figure 10 The carrier 100 is used to support the oxide solid electrolyte membrane 200. The carrier 100 includes a substrate 102, a first coating 104, and a second coating 106. The first coating 104 is applied to the surface of the substrate 102, and the second coating 106 is applied to the surface of the first coating 104. The first coating 104 is disposed between the substrate 102 and the second coating 106.

[0051] The substrate 102 is a material that is heat-resistant and has a low shrinkage rate at high temperatures, such as polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), propylene oxide (PO), cellulose triacetate (TAC), cyclic olefin polymers (COP), etc. Preferably, after the substrate 102 is held at a temperature of 160°C or higher for 10 minutes, the thermal shrinkage rate in both the longitudinal (MD) and transverse (TD) directions is less than 0.5%.

[0052] The thickness of the substrate 102 is preferably in the range of 120–130 μm, but is not limited thereto. The substrate 102 has good mechanical properties. Preferably, the longitudinal tensile strength MD of the substrate 102 is >18 N / m. 2 The transverse tensile strength TD > 13 N / m 2 .

[0053] The coefficient of friction of the substrate 102 is preferably greater than 0.4 μs. The wetting index of the outer surface of the substrate 102 is preferably greater than 55, and the wetting index of the inner surface is preferably less than 42. The outer surface refers to the surface of the substrate 102 that is not in contact with the first coating 104, and the inner surface refers to the surface of the substrate 102 that is in contact with the first coating 104.

[0054] The first coating 104 is an adhesive layer used to increase the adhesion between the substrate 104 and the second coating 106. The thickness of the first coating is preferably 0.5 to 2.0 μm, but is not limited thereto.

[0055] Preferably, the first coating 104 is a functionalized adhesive layer. More preferably, the first coating 104 is a polyethyleneimine (PEI) functionalized adhesive layer. The PEI functionalized adhesive layer provides functionalized interlocking force, appropriately bonding the substrate 102 and the second coating 106, so that the carrier 100 exhibits a characteristic surface energy that matches the oxide solid electrolyte, allowing the oxide solid electrolyte colloid to be effectively coated and interlocked on the surface of the carrier 100. After a series of baking processes, an oxide solid electrolyte film 200 is formed on the surface of the carrier 100, and the oxide solid electrolyte film 200 can be effectively attached to the carrier 100.

[0056] The second coating 106 is a resin layer, and its thickness is preferably 10-12 μm, but not limited thereto. Preferably, the second coating is a silicone-grafted resin layer. The mass ratio of silicon in the silicone-grafted resin layer is preferably 1%-5%. More preferably, the second coating is a silicone-grafted acrylic resin (methyl acrylate).

[0057] Please refer to the following: Figure 1 and Figure 2 This embodiment provides an oxide solid electrolyte membrane 10. The release substrate layer 301 of the release film 300 in the oxide solid electrolyte membrane 10 is made of PP with a thickness of 50 μm. An EVA functionalized coating 302 with adhesive strength is coated on the surface. The EVA functionalized coating 302 has a thickness of 0.5 μm and an adhesive strength of 1 g / inch. The adhesive strength of the EVA functionalized coating 302 is used to increase the adhesion between the solid electrolyte membrane 200 and the membrane.

[0058] The oxide solid electrolyte membrane 200 is formed from lithium lanthanum zirconium oxide (LLZO) solid electrolyte gel. The LLZO solid electrolyte gel contains 5-45% LLZO particles by mass, and the cumulative particle size distribution percentage of the LLZO particles is D50 < 50 nm; D90 < 200 nm. The LLZO solid electrolyte gel contains a polymer, which is a mixture of PVDF1, PVDF2, PVDF3, PMMA, and LiTFSI, wherein PVDF1 > 200 megada; PVDF2 > 1 million Da; and PVDF3 > 300,000 Da. The mass percentages of each component in the polymer are as follows: PVDF1 0-30%; PVDF2 0-30%; PVDF3 0-30%; PMMA 0-10%; and LiTFSI 0-25%. The solvent in the LLZO solid electrolyte gel is: dimethylacetamide (DMAC): N-methylpyrrolidone (NMP): tetrahydrofuran (THF): butanone (MEK): toluene = (70-85): (1-10): (1-15): (1-7): (1-5).

[0059] The substrate 102 in the carrier 100 is a PET sheet with a thickness of 125 μm and a tensile strength MD > 18 N / m. 2 TD>13N / m 2 The coefficient of friction is >0.4 μs; the thermal shrinkage rates in both the transverse and longitudinal directions are less than 0.5; the outer surface wetting index is >55; and the inner surface wetting index is <42. The first coating 104 is polyethyleneimine (PEI), with a degree of polymerization of approximately 90–110 and a monomer molecular weight of 43; the thickness of the adhesive layer is 1 μm. The second coating 106 is polysiloxane-grafted acrylic resin, wherein the mass percentage of silicon in the polysiloxane-grafted acrylic resin is approximately 1%.

[0060] Additionally, please see Figure 11This invention provides a method for preparing an oxide solid electrolyte membrane using the RTR (roll-to-roll) method. First, a solid electrolyte gel is coated onto the surface of a carrier material using a blade coating method, followed by drying to form a solid electrolyte membrane with a thickness of 20–50 μm. Specifically, the carrier material coated with the solid electrolyte gel is placed in an oven and baked at three temperature stages: Stage 1: Heating temperature 80°C–110°C, fan intake airflow 30 Hz, exhaust airflow 25 Hz; Stage 2: Initial solvent evaporation, heating temperature 130°C–150°C, fan intake airflow 30 Hz, exhaust airflow 25 Hz; Stage 3: Heating temperature 130°C–150°C, fan intake airflow 43 Hz, exhaust airflow 25 Hz. Higher fan frequency and larger airflow will affect the solvent concentration and solvent evaporation effect within the oven. Next, the release film provided by this invention is bonded to the surface of the solid electrolyte membrane away from the carrier material. Then, it is rolled up to form an oxide solid electrolyte membrane.

[0061] Please see Figure 12 The electrical properties of the solid electrolyte membrane without release film are shown in the full cell assembly curve. The positive electrode is NCM811, the negative electrode is SiO demixed graphite, the ICE is 88.73%, and the positive electrode lead-out capacity is 203.05mAh / g.

[0062] Please see Figure 13 After a release film with a 0.5 μm thick EVA functionalized coating was bonded to a solid electrolyte membrane, the solid electrolyte membrane was removed for full cell assembly. The positive electrode was NCM811, and the negative electrode was SiO demixed graphite. The ICE was 89.01%, and the positive electrode extraction capacity was 203.6 mAh / g. Figure 12 In contrast, this indicates that the release film with a 0.5 μm thick EVA functionalized coating has no effect on the battery's electrical properties.

[0063] Please see Figure 14 After a release membrane with a 2.0 μm thick EVA functionalized coating was bonded to a solid electrolyte membrane, the solid electrolyte membrane was removed for full cell assembly. The positive electrode was NCM811, and the negative electrode was SiO demixed graphite. The ICE was 89.01%, and the positive electrode extraction capacity was 203.6 mAh / g. Figure 12 In contrast, this indicates that the release film with a 2.0 μm thick EVA functionalized coating has no effect on the battery's electrical properties.

[0064] The release film and oxide solid electrolyte membrane provided by this invention have the following advantages: First, due to the matching adhesive force between the release film and the solid electrolyte membrane, the release film adheres completely during the bonding process, and because the dyne values ​​are mutually matched, gas will not enter between the release film and the solid electrolyte membrane during the preparation process, causing abnormal appearance, thus effectively protecting the solid electrolyte membrane. Second, the release film provided by this invention will not damage the surface of the solid electrolyte membrane when detaching from it, making release easy. When the solid electrolyte membrane is used for full-cell assembly, the solid electrolyte membrane has no impact on the battery's electrical performance.

[0065] Furthermore, those skilled in the art may make other changes within the spirit of this invention, and of course, all such changes made in accordance with the spirit of this invention should be included within the scope of protection claimed by this invention.

Claims

1. A release film for an oxide solid electrolyte membrane, the release film comprising a release substrate layer and an EVA functionalized coating coated on the surface of the release substrate layer, wherein the vinyl acetate content of the EVA functionalized coating is between 10% and 50%.

2. The release film of the oxide solid electrolyte membrane as described in claim 1, wherein, The thickness of the EVA functionalized coating is from 0.5 μm to 2.0 μm.

3. The release film of the oxide solid electrolyte membrane as described in claim 1 or 2, wherein, The adhesion of the EVA functionalized coating is 1–15 g / inch.

4. The release film of the oxide solid electrolyte membrane as described in claim 1, wherein, The EVA functionalized coating satisfies at least one of the following: A. Thickness less than 0.5μm and adhesion greater than or equal to 1g / inch; B. Thickness greater than 2.0 μm and adhesion less than or equal to 15 g / inch.

5. The release film of the oxide solid electrolyte membrane as described in claim 1, wherein, The release substrate layer is made of a thermoplastic polymer of polyethylene terephthalate or polypropylene.

6. The release film of the oxide solid electrolyte membrane as described in claim 1 or 5, wherein, The thickness of the release substrate layer is 40μm to 50μm.

7. The release film of the oxide solid electrolyte membrane as described in claim 1, wherein, The release film is composed of the release substrate layer and the EVA functionalized coating, wherein the vinyl acetate content of the EVA functionalized coating is between 30% and 40%.

8. An oxide solid electrolyte membrane, comprising: Release film as described in any one of claims 1-7; Oxide solid electrolyte membrane; as well as The carrier material, wherein the oxide solid electrolyte membrane is located between the release membrane and the carrier material, and the release membrane is bonded to the oxide solid electrolyte membrane through the EVA functionalized coating.

9. The oxide solid electrolyte membrane as described in claim 8, wherein, The carrier material includes a substrate, a first coating, and a second coating. The first coating is applied to the surface of the substrate, and the second coating is applied to the surface of the first coating. The first coating is a polyethyleneimine-functionalized adhesive layer, and the second coating is a silicone-grafted acrylic resin layer.

10. The oxide solid electrolyte membrane as described in claim 9, wherein, The substrate material is a polymer selected from which the thermal shrinkage rate in both the longitudinal (MD) and transverse (TD) directions is less than 0.5 after being held at a temperature greater than or equal to 160°C for at least 10 minutes.

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