Release film for lithium transfer and method for producing same

Abstract

The present invention relates to a release film for lithium transfer and a method for manufacturing the same, and more particularly, to a release film for transferring lithium (Li) to a battery current collector after depositing the lithium (Li) on the release film, which can minimize the generation of pin holes when depositing the lithium (Li) on the release film, not only is excellent in deposition efficiency, but also is excellent in reliability. The present invention relates to a release film for lithium transfer and a method for manufacturing the same, and more particularly, to a release film for lithium transfer and a method for manufacturing the same, which have excellent efficiency of transferring lithium deposited on the release film to a current collector.

Description

Technical Field

[0001] This invention relates to a release film for lithium transfer and a method for manufacturing the same. More specifically, it relates to a release film for transferring lithium (Li) deposited on a release film to a battery current collector. The release film minimizes pinhole formation during lithium (Li) deposition, resulting in excellent deposition efficiency and high efficiency in transferring lithium deposited on the release film to the current collector. Background Technology

[0002] Batteries, specifically rechargeable batteries, have a relatively small capacity compared to the theoretical capacity of the negative electrode material because a significant portion of the lithium ions released from the positive electrode during the first charge are embedded in the negative electrode. To avoid this irreversible capacity loss, a technique has been disclosed in which lithium equivalent to the amount of irreversible capacity loss is pre-embedded in the negative electrode before assembling the rechargeable battery and initiating charging and discharging. By utilizing this method, a higher proportion of lithium ions released from the positive electrode during the first charge can be recovered to the negative electrode, thereby increasing the battery capacity.

[0003] On the other hand, a common method for pre-embedding lithium into the negative electrode is to deposit lithium onto the negative electrode. To deposit lithium equivalent to the irreversible capacity, methods are being investigated to pretreat graphite or silicon-graphite materials on the current collector to increase the amount of lithium deposited.

[0004] However, graphite materials have capacity limitations during lithium-ion movement, and silicon-graphite materials experience rapid volume expansion during lithium-ion movement, which may cause battery durability issues.

[0005] For the reasons mentioned above, there is a need to develop a method for pre-charging the negative electrode with sufficient lithium and / or a new method to prevent volume expansion due to the increase in lithium content. One such method is to deposit lithium metal on a release film and then transfer it to a current collector, preferably a negative electrode current collector.

[0006] In summary, regarding the method of transferring lithium to the current collector after deposition on the release film, a solution is currently needed to ensure uniform lithium deposition and high transfer efficiency. Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] The present invention aims to solve the above-mentioned problems, and its purpose is to provide a release film for lithium transfer that can ensure uniform deposition performance and transfer efficiency, and a method for manufacturing the same.

[0009] means for solving problems

[0010] To address the aforementioned problems, the lithium transfer release film of the present invention may include a base film and a release layer formed on one side of the base film.

[0011] In a preferred embodiment of the present invention, after lithium is deposited on one side of the release film for lithium transfer with a thickness of 2 to 25 μm, when white light is irradiated onto the base film, the number of pinholes generated per unit area of ​​10 cm × 10 cm in the deposited lithium can be less than 100.

[0012] In a preferred embodiment of the present invention, after lithium is deposited on one side of the release layer with a thickness of 2 to 8 μm, when white light is irradiated onto the base film, the number of pinholes generated per unit area of ​​10 cm × 10 cm in the deposited lithium can be less than 100.

[0013] In a preferred embodiment of the present invention, the release layer may comprise a resin composition.

[0014] In a preferred embodiment of the present invention, the resin composition may include 10 to 70% by weight of silicone resin.

[0015] In a preferred embodiment of the present invention, the release layer may include 0.1 to 5 parts by weight of catalyst and 0.1 to 5 parts by weight of adhesion enhancer relative to 100 parts by weight of resin composition.

[0016] In a preferred embodiment of the present invention, the release layer may include 2 to 5% by weight of silicon (Si) based on the total weight percentage.

[0017] In a preferred embodiment of the present invention, the surface tension of the release layer can be 25 to 30 dyne.

[0018] In a preferred embodiment of the present invention, the release force of the release layer can be 33 to 44 gf / inch.

[0019] In a preferred embodiment of the present invention, the water contact angle of the release layer can be 95 to 105°.

[0020] In a preferred embodiment of the present invention, the base film may be transferred to one or more of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), and polyethylene (PE).

[0021] In a preferred embodiment of the present invention, the resin composition may include silicone resins and non-silicone resins.

[0022] In a preferred embodiment of the present invention, the silicone resin may include one or more selected from addition-reactive silicone resins, condensation-reactive silicone resins, and UV-reactive silicone resins.

[0023] In a preferred embodiment of the present invention, the non-silicone resin may include one or more selected from cellulose resin, acrylate resin, melamine resin and alkyd resin.

[0024] On the other hand, the method for manufacturing the lithium transfer release film of the present invention includes the following steps: a first step of preparing a base film; and a second step of coating a release layer forming composition on one side of the base film and then curing it to form a release layer; wherein, after lithium is deposited on one side of the release layer with a thickness of 2 to 8 μm, when the base film is irradiated with white light, the number of pinholes generated per unit area of ​​10 cm × 10 cm in the deposited lithium can be less than 100.

[0025] In a preferred embodiment of the present invention, the release layer forming composition may be a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent.

[0026] In a preferred embodiment of the present invention, the resin composition may contain 10 to 70% by weight of silicone resin.

[0027] In a preferred embodiment of the present invention, the release layer forming composition may contain 0.1 to 5 parts by weight of catalyst, 0.1 to 5 parts by weight of adhesion enhancer and 800 to 1000 parts by weight of solvent relative to 100 parts by weight of resin composition.

[0028] In a preferred embodiment of the present invention, curing can be carried out at a temperature of 100–140°C for 10–40 seconds.

[0029] The effects of the invention

[0030] The lithium transfer release film and its manufacturing method of the present invention are release films that deposit lithium (Li) on the release film and then transfer it to the battery current collector. By pre-embedding lithium equivalent to the amount of irreversibly lost lithium ions into the negative electrode current collector during the first charge and discharge of the secondary battery, the capacity of the secondary battery can be improved.

[0031] Furthermore, the lithium transfer release film and its manufacturing method of the present invention can minimize the generation of pinholes when depositing lithium (Li) on the release film, thereby achieving excellent deposition efficiency.

[0032] Furthermore, the lithium transfer release film and its manufacturing method of the present invention have excellent efficiency in transferring lithium deposited on the release film to the current collector. Attached Figure Description

[0033] Figure 1 A cross-sectional view is provided to show a preferred embodiment of the present invention, on one side of which is provided a release film for lithium transfer.

[0034] Figure 2 This diagram illustrates, according to a preferred embodiment of the present invention, the formation of pinholes in the deposited lithium by irradiating the base film with white light after lithium deposition on one side of the release layer. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can readily implement the present invention. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the description are omitted for clarity, and the same or similar reference numerals are used throughout the specification.

[0036] Reference Figure 1 As can be described, the lithium transfer release film of the present invention may include a base film 10 and a release layer 20 disposed on one side of the base film 10.

[0037] The base film 10 is a film that acts as a substrate film when the release layer 20 is coated or lithium (Li) is deposited. Any base film material used in the art can be used. Preferably, it can include one or more selected from polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), and polyethylene (PE). More preferably, it can include PET.

[0038] Furthermore, the base film 10 of the present invention can have a thickness of 10 to 250 μm, preferably 25 to 100 μm. If the thickness is less than 10 μm, thermal deformation of the base film 10 may occur during the lithium (Li) deposition process at high temperature. If the thickness exceeds 250 μm, there may be economic issues.

[0039] Release layer 20 is a layer used to uniformly deposit lithium (Li) or to facilitate the transfer of lithium (Li) to the current collector. It is a layer in which lithium is deposited on one side for the purpose of transferring lithium.

[0040] The release layer 20 can have a thickness of 0.01 to 1 μm, preferably 0.05 to 0.5 μm; if the thickness is less than 0.01 μm, there may be problems with transfer defects, and if it exceeds 1 μm, there may be problems with adhesion during winding.

[0041] The release layer 20 may include a resin composition, which may include 10 to 70% by weight of a silicone resin, preferably 30 to 70% by weight, more preferably 45 to 70% by weight, and even more preferably 55 to 65% by weight, based on the total weight percentage. If the content of the silicone resin is less than 10% by weight, there may be a problem of significantly reduced lithium transfer efficiency. If it exceeds 70% by weight, there may be a problem of increased pinhole rate in the deposited lithium when lithium is deposited on one side of the release layer.

[0042] On the other hand, the silicone resin may include one or more selected from addition-reaction silicone resin, condensation-reaction silicone resin and UV-reaction silicone resin, preferably including addition-reaction silicone resin.

[0043] In addition, the resin composition may include silicone resin and non-silicone resin. The non-silicone resin may include 30 to 90% by weight of the total weight of the resin composition, preferably 30 to 70% by weight, more preferably 30 to 55% by weight, and even more preferably 35 to 45% by weight.

[0044] In addition, non-silicone resins are resins that do not contain silicon (Si) as a constituent component, and may include one or more selected from cellulose resins, acrylate resins, melamine resins and alkyd resins, preferably including cellulose resins.

[0045] Furthermore, the release layer 20 may include 2 to 5% silicon (Si) by weight, preferably 3 to 5% by weight, more preferably 3.3 to 5% by weight, and even more preferably 3.8 to 4.9% by weight. If the silicon content is less than 2% by weight, there may be a problem of significantly reduced lithium transfer efficiency. If it exceeds 5% by weight, there may be a problem of increased pinhole rate in the deposited lithium when depositing lithium on one side of the release layer.

[0046] In addition, the release layer 20 may include 0.1 to 5 parts by weight of catalyst, preferably 0.5 to 3.0 parts by weight, and more preferably 1.0 to 2.0 parts by weight, relative to 100 parts by weight of the resin composition; if the content of catalyst is less than 0.1 parts by weight, there may be a problem of incomplete curing, while if it exceeds 5 parts by weight, there may be a problem of significantly increased peel strength.

[0047] Furthermore, the catalyst can be any catalyst commonly used in the art, and preferably may include platinum.

[0048] Furthermore, the release layer 20 may include 0.1 to 5 parts by weight of an adhesion enhancer relative to 100 parts by weight of the resin composition, preferably 0.5 to 3.0 parts by weight, more preferably 0.5 to 1.5 parts by weight. If the content of the adhesion enhancer is less than 0.1 parts by weight, there may be a problem of poor adhesion between the release layer 20 and the base film 10. If it exceeds 5 parts by weight, there may be a problem of silicon (Si) contained in the release layer 20 transferring to the back side of the base film 10.

[0049] The adhesion enhancer is a material used to improve the adhesion between the release layer 20 and the base film 10. It can be any adhesion enhancer commonly used in the art, and preferably may include dimethyl, Methylvinyl siloxane with epoxide.

[0050] On the other hand, refer to Figure 2To illustrate, in the lithium transfer release film of the present invention, after lithium 30 is deposited on one side of the release layer 20 with a thickness of 2-25 μm, preferably 2-20 μm, more preferably 2-15 μm, even more preferably 2-8 μm, even more preferably 3-7 μm, and even more preferably 4-6 μm, when white light is irradiated onto the base film 10, the number of pinholes generated per 10 cm × 10 cm unit area in the deposited lithium 30 can be less than 100. Pinholes refer to pores generated in the lithium 30 during deposition. If more than 100 pinholes are generated per 10 cm × 10 cm unit area in the lithium 30, there may be a problem of uneven deposition of lithium 30. Furthermore, white light refers to light with a wavelength of 400-700 nm.

[0051] Furthermore, in the lithium transfer release film of the present invention, the surface tension of the release layer 20 can be 25 to 30 dyne, preferably 25 to 28 dyne. If the surface tension is less than 25 dyne, there may be a problem of a large number of pinholes being generated during lithium deposition. If it exceeds 30 dyne, there may be a problem of reduced transfer efficiency when transferring lithium to the current collector.

[0052] Furthermore, in the lithium transfer release film of the present invention, the release force of the release layer 20 can be 33 to 44 gf / inch, preferably 33 to 40 gf / inch, and more preferably 34 to 36 gf / inch. If the release force is less than 33 gf / inch, there may be a problem of a large number of pinholes being generated during lithium deposition. If it exceeds 44 gf / inch, there may be a problem of reduced transfer efficiency when transferring lithium to the current collector.

[0053] Furthermore, in the lithium transfer release film of the present invention, the water contact angle of the release layer 20 can be 95 to 105°, preferably 100 to 105°. If the water contact angle is less than 95°, there may be a problem of reduced transfer efficiency when transferring lithium to the current collector, and if it exceeds 105°, there may be a problem of a large number of pinholes generated during lithium deposition.

[0054] Furthermore, the method for manufacturing the lithium transfer release film of the present invention includes a first step and a second step.

[0055] First, the first step of the method for manufacturing the lithium transfer release film of the present invention can be to prepare a base film. At this time, the base film is as described above.

[0056] Next, in the second step of the method for manufacturing the lithium transfer release film of the present invention, a release layer forming composition is coated on one side of the base film prepared in the first step and then cured to form a release layer.

[0057] The release layer forming composition may be a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent. Specifically, the release layer forming composition may contain, relative to 100 parts by weight of the resin composition, 0.1 to 5 parts by weight of the catalyst, preferably 0.5 to 3.0 parts by weight, more preferably 1.0 to 2.0 parts by weight; 0.1 to 5 parts by weight of the adhesion enhancer, preferably 0.5 to 3.0 parts by weight, more preferably 0.5 to 1.5 parts by weight; and 800 to 1000 parts by weight of the solvent, preferably 850 to 950 parts by weight. In this case, the catalyst and adhesion enhancer are as described above. Furthermore, the solvent may be any solvent commonly used in the art, preferably including one or more selected from toluene, methyl ethyl ketone (MEK), n-hexane, and methyl isobutyl ketone (MIBK).

[0058] Furthermore, the resin composition can be a mixture of silicone resin and non-silicone resin. The silicone resin can contain 10-70% by weight of the total weight of the resin composition, preferably 30-70% by weight, more preferably 45-70% by weight, and even more preferably 55-65% by weight. The non-silicone resin can contain 30-90% by weight of the total weight of the resin composition, preferably 30-70% by weight, more preferably 30-55% by weight, and even more preferably 35-45% by weight. In this case, the silicone resin and non-silicone resin are as described above.

[0059] Furthermore, the release layer formed by curing the release layer forming composition may include 2 to 5% silicon (Si) by weight, preferably 3 to 5% by weight, more preferably 3.3 to 5% by weight, and even more preferably 3.8 to 4.9% by weight, based on the total weight percentage. Additionally, the release layer is as described above.

[0060] In addition, the curing in the second step can be carried out at a temperature of 100-140°C, preferably 110-130°C, for 10-40 seconds, preferably 15-25 seconds. If the curing temperature is lower than 100°C, there may be a problem of incomplete curing, while if it exceeds 140°C, there may be a problem of thermal deformation of the base film.

[0061] Furthermore, the lithium transfer release film prepared by the manufacturing method of the lithium transfer release film of the present invention deposits lithium on one side of the release layer with a thickness of 2 to 25 μm, preferably 2 to 20 μm, more preferably 2 to 15 μm, even more preferably 2 to 8 μm, even more preferably 3 to 7 μm, and even more preferably 4 to 6 μm. Subsequently, when the base film is irradiated with white light, the number of pinholes generated per unit area of ​​10 cm × 10 cm in the deposited lithium can be less than 100.

[0062] Furthermore, in the lithium transfer release film prepared by the method of the present invention, the surface tension of the release layer can be 25 to 30 dyne, preferably 25 to 28 dyne.

[0063] Furthermore, in the lithium transfer release film prepared by the method of the present invention, the release force of the release layer can be 33 to 44 gf / inch, preferably 33 to 40 gf / inch, and more preferably 34 to 36 gf / inch.

[0064] Furthermore, in the lithium transfer release film prepared by the method of the present invention, the water contact angle of the release layer can be 95 to 105°, preferably 100 to 105°.

[0065] The present invention has been described above with reference to embodiments, but these are merely examples and are not intended to limit the embodiments of the present invention. Those skilled in the art will understand that various modifications and applications not illustrated above can be made without departing from the essential characteristics of the present invention. For example, the constituent elements specifically shown in the embodiments of the present invention can be modified. Furthermore, differences related to these modifications and applications should be interpreted as being included within the scope of the present invention as defined in the appended claims.

[0066] Preparation Example 1: Preparation of Composition for Release Layer Forming

[0067] A release layer forming composition is prepared by mixing 1.5 parts by weight of a catalyst, 1 part by weight of an adhesion enhancer, and 900 parts by weight of a solvent with 100 parts by weight of the resin composition. In this case, the resin composition comprises 60% by weight of a silicone resin and 40% by weight of a non-silicone resin, the catalyst is platinum, the adhesion enhancer is dimethyl, methylvinyl siloxane with epoxide, and the solvent is toluene. Furthermore, the silicone resin is an addition-reaction silicone resin (dimethyl, 5-hexenylmethyl siloxane), and the non-silicone resin is a cellulose resin.

[0068] Preparation Example 2: Preparation of Composition for Release Layer Forming

[0069] The release layer forming composition was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, the resin composition used was a composition comprising 50% by weight of a silicone resin and 50% by weight of a non-silicone resin, based on total weight%.

[0070] Preparation Example 3: Preparation of Composition for Release Layer Forming

[0071] The release layer forming composition was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, the resin composition used was a composition comprising 40% by weight of silicone resin and 60% by weight of non-silicone resin, based on total weight%.

[0072] Preparation Example 4: Preparation of Composition for Release Layer Forming

[0073] The release layer forming composition was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, the resin composition used was a composition comprising 20% ​​by weight of silicone resin and 80% by weight of non-silicone resin, based on total weight%.

[0074] Comparative Preparation Example 1: Preparation of Compositions for Release Layer Forming

[0075] The release layer forming composition was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, the resin composition used was a composition comprising 80% by weight of silicone resin and 20% by weight of non-silicone resin, based on total weight%.

[0076] Preparation of compositions for lithium transfer and release layer formation

[0077] The release layer forming composition was prepared using the same method as in Preparation Example 1. However, unlike Preparation Example 1, the resin composition used was only a silicone-based resin.

[0078] Comparative Preparation Example 2: Preparation of Compositions for Release Layer Forming

[0079] A release layer forming composition is prepared by mixing 1.5 parts by weight of a catalyst, 1 part by weight of an adhesion enhancer, and 600 parts by weight of a solvent with 100 parts by weight of the resin composition. In this case, the resin composition is a silicone-based resin; the catalyst is platinum; the adhesion enhancer is dimethyl, methylvinylsiloxane with epoxide; and the solvent is toluene. Furthermore, the silicone-based resin is an addition-reaction type silicone-based resin (dimethyl, 5-hexenylmethyl siloxane).

[0080] Example 1: Manufacturing of release film for lithium transfer

[0081] (1) As a base film, prepare a PET (Polyethylene terephthalate) film (XD510P, TAK Company) with a thickness of 50μm.

[0082] (2) Using a bar coater, the release layer forming composition prepared in Preparation Example 1 was coated on one side of the prepared base film, cured at 120°C for 20 seconds, and aged at 40°C for 2 days to form a release layer with a thickness of 0.1 μm, thereby preparing a release film for lithium transfer.

[0083] Example 2: Manufacturing of release film for lithium transfer

[0084] The lithium transfer release film was prepared using the same method as in Example 1. However, unlike Example 1, the release layer forming composition prepared in Preparation Example 2 was used instead of the release layer forming composition prepared in Preparation Example 1, and the lithium transfer release film was finally prepared.

[0085] Example 3: Manufacturing of release film for lithium transfer

[0086] A release film for lithium transfer was prepared using the same method as in Example 1. However, unlike Example 1, the release layer forming composition prepared in Preparation Example 3 was used instead of the release layer forming composition prepared in Preparation Example 1, and a release film for lithium transfer was finally prepared.

[0087] Example 4: Manufacturing of release film for lithium transfer

[0088] The lithium transfer release film was prepared using the same method as in Example 1. However, unlike Example 1, the release layer forming composition prepared in Preparation Example 4 was used instead of the release layer forming composition prepared in Preparation Example 1, and the lithium transfer release film was finally prepared.

[0089] Comparative Example 1: Manufacturing of Release Film for Lithium Transfer

[0090] The lithium transfer release film was prepared using the same method as in Example 1. However, unlike Example 1, the release layer forming composition prepared in Comparative Preparation Example 1 was used instead of the release layer forming composition prepared in Preparation Example 1, and the lithium transfer release film was finally prepared.

[0091] Comparative Example 2: Manufacturing of Release Film for Lithium Transfer

[0092] The release film for lithium transfer was prepared using the same method as in Example 1. However, unlike Example 1, the release layer forming composition prepared in Comparative Preparation Example 2 was used to form a release layer with a thickness of 0.15 μm, thereby preparing the release film for lithium transfer.

[0093] Experiment Example 1: Determination of the number of pinholes

[0094] Using the PVD (Physical Vapor Deposition) method, lithium with a thickness of 5 μm was deposited on one side of each release layer of the lithium transfer release films prepared in Examples 1-4 and Comparative Examples 1-2. Subsequently, each base film of the lithium transfer release films prepared in Examples 1-4 and Comparative Examples 1-2 was irradiated with white light, and the deposited lithium was observed with the naked eye. The number of pinholes generated per 10 cm × 10 cm unit area is listed in Table 1.

[0095] Experimental Example 2: Surface Tension Measurement

[0096] The surface tension of the release layer of the lithium transfer release films prepared in Examples 1-4 and Comparative Examples 1-2 was measured using dyne reagent, and the results are shown in Table 1. Arcotest's 22-40 dyne test ink was used for the dyne test.

[0097] Experimental Example 3: Release Force Measurement

[0098] Acrylic tape (TESA7475) with a width of 25 mm × a length of 175 mm was pasted onto the release layer of the lithium transfer release film prepared in Examples 1-4 and Comparative Examples 1-2, and the release force of the release layer of each lithium transfer release film was measured according to the Finat-10 evaluation method. The results are listed in Table 1 below.

[0099] Experiment Example 4: Measurement of Water Contact Angle

[0100] After adding 50 μL of distilled water (H2O) to the release layer of the lithium transfer release film prepared in Examples 1-4 and Comparative Examples 1-2, the water contact angle of the release layer of the lithium transfer release film prepared in Examples 1-4 and Comparative Examples 1-2 was measured using a contact angle measuring instrument. The results are shown in Table 1 below.

[0101] Experimental Example 5: Determination of Silicon (Si) Content

[0102] The silicon (Si) content in each lithium transfer release film prepared in Examples 1-4 and Comparative Examples 1-2 was determined using a scanning electron microscope (SEM) equipped with an EDS (Energy Dispersive X-ray Spectroscopy) device. The results are shown in Table 1 below.

[0103] Experiment Example 6: Lithium Transfer Efficiency Measurement

[0104] Using the PVD (Physical Vapor Deposition) method, lithium with a thickness of 5 μm was deposited on one side of each release layer of the lithium transfer release films prepared in Examples 1-4 and Comparative Examples 1-2. Then, the lithium deposited on the lithium transfer release film was rolled laminating onto one side of a copper foil (Cu foil) used as a negative electrode current collector, and the lithium transfer release film was removed, thereby transferring the lithium onto the copper foil. After the transfer was completed, the area of ​​lithium remaining on the lithium transfer release film was visually confirmed, and the lithium transfer efficiency was calculated using the following formula 1. The results are shown in Table 1 below.

[0105] [Calculation Formula 1]

[0106] Lithium transfer efficiency (%) = (Area of ​​lithium deposited on the release film for lithium transfer - Area of ​​lithium remaining on the release film after transferring the lithium deposited on the release film to the copper foil) / Area of ​​lithium deposited on the release film for lithium transfer

[0107]

[0108] As shown in Table 1, it can be confirmed that the lithium transfer release films prepared in Examples 1 to 3 not only have fewer than 100 pinholes per 10cm × 10cm unit area, but also exhibit excellent lithium transfer efficiency.

[0109] Experiment Example 7: Determination of the Number of Pinholes

[0110] Using physical vapor deposition (PVD), lithium with thicknesses of 5 μm, 10 μm, 15 μm, 20 μm, and 30 μm was deposited on the release layer surface of the lithium transfer release film prepared in Example 1. Subsequently, the base films of each lithium transfer release film prepared in Example 1 (with lithium deposited at different thicknesses) were irradiated with white light, and the deposited lithium was visually observed. The number of pinholes per 10 cm × 10 cm unit area is shown in Table 2.

[0111]

[0112] As shown in Table 2, even when lithium with thicknesses of 5 μm, 10 μm, 15 μm, and 20 μm is deposited on the release layer side of the lithium transfer release film prepared in Example 1, the number of pinholes per 10 cm × 10 cm unit area is still less than 100. However, when lithium with a thickness of 30 μm is deposited on the release layer side of the lithium transfer release film prepared in Example 1, thermal deformation can be observed during the deposition process.

[0113] Those skilled in the art can easily make simple modifications or variations to this invention, and all such modifications or variations should be considered to be included within the scope of protection of this invention.

[0114] [National research and development projects supporting this invention]

[0115] [Project Unique Number] 1415185120

[0116] [Project Number] 20011254

[0117] [Department Name] Trade, Industry and Resources Department

[0118] [Name of the project management (professional) organization] Korea Institute for Industrial Technology Evaluation

[0119] [Research Project Name] Material Component Technology Development (Investigation and Analysis Project Name: Material Component Technology Development)

[0120] [Research Project Title] Development of Ultra-Easy-to-Peel Functional Release Adhesive Thin Film Technology with Minimal Time-Related Changes

[0121] [Contribution Rate] 1 / 1

[0122] [Name of the organization undertaking the project] Kurimura Chemical Co., Ltd.

[0123] [Research Period] January 1, 2023 – December 31, 2023

Claims

1. A release film for lithium transfer, comprising: Base film; as well as A release layer formed on one side of the base film; The feature is that, after lithium is deposited on one side of the release layer with a thickness of 2 to 25 μm, when the base film is irradiated with white light, the number of pinholes generated per 10 cm × 10 cm unit area in the deposited lithium is less than 100.

2. The release film for lithium transfer according to claim 1, characterized in that, The release layer comprises a resin composition. The resin composition comprises 10 to 70% by weight of silicone resin, based on the total weight percentage.

3. The release film for lithium transfer according to claim 2, wherein, The release layer comprises, relative to 100 parts by weight of the resin composition, 0.1 to 5 parts by weight of a catalyst and 0.1 to 5 parts by weight of an adhesion enhancer.

4. The release film for lithium transfer according to claim 1, characterized in that, The release layer comprises 2 to 5% by weight of silicon (Si) in total weight percentage.

5. The release film for lithium transfer according to claim 1, characterized in that, The surface tension of the release layer is 25–30 dyne. The release force of the release layer is 33–44 gf / inch. The water contact angle of the release layer is 95–105°.

6. The release film for lithium transfer according to claim 1, characterized in that, The base film comprises one or more selected from polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyimide (PI), and polyethylene (PE).

7. The release film for lithium transfer according to claim 2, characterized in that, The resin composition includes silicone resins and non-silicone resins. The silicone resin includes one or more selected from addition-reaction silicone resins, condensation-reaction silicone resins, and UV-reaction silicone resins. The non-silicone resin includes one or more selected from cellulose resin, acrylate resin, melamine resin and alkyd resin.

8. The release film for lithium transfer according to claim 1, characterized in that, After lithium is deposited on one side of the release layer with a thickness of 2 to 8 μm, when the base film is irradiated with white light, the number of pinholes generated per 10 cm × 10 cm unit area in the deposited lithium is less than 100.

9. A method for manufacturing a release film for lithium transfer, comprising the following steps: The first step is to prepare the base film; and The second step involves coating a release layer forming composition onto one side of the base film and then curing it to form a release layer. Its features are, After lithium is deposited on one side of the release layer with a thickness of 2 to 25 μm, when the base film is irradiated with white light, the number of pinholes generated per 10 cm × 10 cm unit area in the deposited lithium is less than 100.

10. The method for manufacturing a release film for lithium transfer according to claim 9, characterized in that, The release layer forming composition is a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent. The resin composition contains 10 to 70% by weight of silicone resin, based on the total weight percentage.

11. The method for manufacturing a release film for lithium transfer according to claim 10, characterized in that, The release layer forming composition is composed of 0.1 to 5 parts by weight of catalyst, 0.1 to 5 parts by weight of adhesion enhancer and 800 to 1000 parts by weight of solvent, relative to 100 parts by weight of resin composition.

12. The method for manufacturing a release film for lithium transfer according to claim 9, characterized in that, The curing process is carried out at a temperature of 100–140°C for 10–40 seconds.

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