Release film for transferring lithium and method for manufacturing same

Abstract

The present invention relates to a release film for transferring lithium and a method for manufacturing same and, more specifically, to a release film for transferring lithium and a method for manufacturing same, the release film being for depositing lithium (Li) on the release film and then transferring same to a current collector of a battery, wherein the occurrence of pin holes during the deposition of lithium (Li) on the release film is minimized, and thus deposition efficiency is excellent, the efficiency of transferring the lithium deposited on the release film to the current collector is excellent, and the lithium peel strength is low, and thus lithium can be easily transferred to the current collector even at low pressure and temperature.

Description

Lithium transfer release film and method for manufacturing the same

[0001] The present invention relates to a lithium transfer release film and a method for manufacturing the same. More specifically, the invention relates to a release film for transferring lithium (Li) to a current collector of a battery after depositing lithium (Li) on the release film, wherein the deposition efficiency is excellent by minimizing the occurrence of pinholes when depositing lithium (Li) on the release film, and the efficiency of transferring the lithium deposited on the release film to the current collector is excellent, and the lithium can be easily transferred to the current collector even at low pressure and temperature due to low lithium peeling force.

[0002]

[0003] In batteries, specifically secondary batteries, the battery capacity is reduced compared to the theoretical capacity of the anode material because a large proportion of the lithium ions released from the positive electrode during the first charge remain adsorbed on the negative electrode. To avoid such irreversible capacity loss, a technique has been disclosed in which lithium equivalent to the irreversible capacity loss is adsorbed on the negative electrode in advance, and then the secondary battery is assembled and charging and discharging are initiated. By utilizing this technique, a high 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.

[0004] Meanwhile, as a common method for pre-absorbing lithium onto the cathode, a method of depositing lithium onto the cathode is used. In order to deposit lithium equivalent to an irreversible capacity, a method is being studied to increase the amount of lithium deposited by pre-treating a graphite material or a silicon graphite material onto a current collector.

[0005] However, graphite materials have a capacity limit when lithium ions move, and silicon graphite materials are highly likely to cause problems with battery durability due to rapid volume expansion during lithium ion movement.

[0006] For this reason, there is a need to develop a new method to pre-charge a sufficient amount of lithium into the cathode and / or prevent volume expansion due to an increase in the amount of lithium, and as one such method, a method is being attempted in which lithium metal is deposited on a release film and then transferred to a current collector, preferably a cathode current collector.

[0007] In conclusion, regarding the method of depositing lithium on a release film and then transferring it to a current collector, there is a need for measures to ensure uniform lithium deposition and high transfer efficiency.

[0008]

[0009] The present invention was devised to solve the above-mentioned problems and aims to provide a lithium transfer release film capable of securing uniform deposition performance and transfer efficiency, and a method for manufacturing the same.

[0010] In addition, the purpose is to provide a lithium transfer release film and a method for manufacturing the same, wherein multiple lithium transfer release films of the present invention are laminated for ease of use, and not only is there excellent unravelability when separated, but lithium (Li) can also be prevented from transferring to parts other than the portion where lithium (Li) is deposited.

[0011] In addition, another objective is to provide a lithium transfer release film and a method for manufacturing the same, which allows lithium to be easily transferred to a current collector even at low pressure and temperature due to low lithium peeling force.

[0012]

[0013] To solve the above-mentioned problem, the lithium transfer release film of the present invention may have a structure in which a first release layer, a base film, and a second release layer are sequentially laminated.

[0014] In a preferred embodiment of the present invention, the lithium transfer release film of the present invention can satisfy the following condition (1).

[0015] (1) A ≥ B

[0016] In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0017] In a preferred embodiment of the present invention, the lithium transfer release film of the present invention may further satisfy the following condition (2).

[0018] (2) B : A = 1 : 1.0 ~ 5.0

[0019] In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0020] In a preferred embodiment of the present invention, the base film and the first release layer may have a thickness ratio of 1:0.0014 to 0.0026.

[0021] In a preferred embodiment of the present invention, the base film and the second release layer may have a thickness ratio of 1:0.001 to 0.0018.

[0022] In a preferred embodiment of the present invention, the lithium transfer release film of the present invention deposits lithium to a thickness of 2 to 25 μm on one surface of the second release layer, and then irradiates the first release layer with white light, so that 100 or fewer pin holes may occur per unit area of ​​10 cm x 10 cm in the deposited lithium.

[0023] In a preferred embodiment of the present invention, the lithium transfer release film of the present invention deposits lithium to a thickness of 2 to 8 μm on one surface of the second release layer, and then irradiates the first release layer with white light, so that 100 or fewer pin holes may occur per unit area of ​​10 cm x 10 cm in the deposited lithium.

[0024] In a preferred embodiment of the present invention, the first release layer may include a resin composition.

[0025] In a preferred embodiment of the present invention, the resin composition of the first release layer may include 10 to 70 weight percent of a silicone-based resin based on the total weight percent.

[0026] In a preferred embodiment of the present invention, the first release layer may comprise 0.1 to 5 parts by weight of a catalyst and 0.1 to 5 parts by weight of an adhesion enhancer, based on 100 parts by weight of a resin composition.

[0027] In a preferred embodiment of the present invention, the first release layer may contain silicon (Si) in an amount of 0.1 to 15 weight% with respect to the total weight%.

[0028] In a preferred embodiment of the present invention, the second release layer may contain silicon (Si) in an amount of 5.0 to 25 weight% with respect to the total weight%.

[0029] In a preferred embodiment of the present invention, the lithium transfer release film of the present invention can satisfy the following condition (3).

[0030] (3) C ≤ D

[0031] In the above condition (3), C represents the weight percentage of silicon (Si) contained in the first release layer, and D represents the weight percentage of silicon (Si) contained in the second release layer.

[0032] In a preferred embodiment of the present invention, the base film may include one or more selected from PET (Polyethylene terephthalate), PP (Polypropylene), PBT (Polybutyleneterephthalate), PEN (Polyethylene naphthalate), PI (Polyimide), and PE (Polyethylene).

[0033] In a preferred embodiment of the present invention, the resin composition of the first release layer may include a silicone-based resin and a non-silicone-based resin.

[0034] In a preferred embodiment of the present invention, the silicone resin may include one or more selected from addition-type silicone resin, condensation-type silicone resin, and UV-type silicone resin.

[0035] 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.

[0036] Meanwhile, the method for manufacturing a lithium transfer release film of the present invention comprises a first step of preparing a base film and a second step of applying a composition for forming a first release layer to one side of the base film and applying a composition for forming a second release layer to the other side of the base film, and then curing to form a first release layer on one side of the base film and a second release layer on the other side of the base film, and can satisfy the following condition (1).

[0037] (1) A ≥ B

[0038] In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0039] In a preferred embodiment of the present invention, the method for manufacturing a lithium transfer release film of the present invention may further satisfy the following condition (2).

[0040] (2) B : A = 1 : 1.0 ~ 5.0

[0041] In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0042] In a preferred embodiment of the present invention, after depositing lithium to a thickness of 2 to 25 μm on one surface of the second release layer, if white light is irradiated onto the first release layer, 100 or fewer pin holes may occur per unit area of ​​10 cm x 10 cm in the deposited lithium.

[0043] In a preferred embodiment of the present invention, the composition for forming the first release layer may be a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent.

[0044] In a preferred embodiment of the present invention, the resin composition of the composition for forming the first release layer may be a mixture of 10 to 70 weight percent of silicone-based resin based on the total weight percent.

[0045] In a preferred embodiment of the present invention, the composition for forming the first release layer may be a mixture of 0.1 to 5 parts by weight of a catalyst, 0.1 to 5 parts by weight of an adhesion enhancer, and 800 to 1000 parts by weight of a solvent, based on 100 parts by weight of a resin composition.

[0046] In a preferred embodiment of the present invention, curing can be performed at a temperature of 100 to 140°C for 10 to 40 seconds.

[0047]

[0048] The lithium transfer release film and the method for manufacturing the same according to the present invention are release films for depositing lithium (Li) on the release film and then transferring it to the current collector of a battery, and can increase the capacity of a secondary battery by pre-absorbing lithium on the negative current collector equivalent to the amount of lithium ions irreversibly lost during the first charge and discharge cycle of the secondary battery.

[0049] In addition, the lithium transfer release film and the method for manufacturing the same according to the present invention minimize the occurrence of pinholes when lithium (Li) is deposited on the release film, thereby providing excellent deposition efficiency.

[0050] In addition, the lithium transfer release film and the method for manufacturing the same according to the present invention have excellent efficiency in transferring lithium deposited on the release film to the current collector.

[0051] In addition, the lithium transfer release film of the present invention and the method for manufacturing the same allow for the lamination of multiple lithium transfer release films of the present invention for convenience of use, and even when separated, the release properties are excellent.

[0052] In addition, the lithium transfer release film of the present invention and the method for manufacturing the same can prevent the phenomenon in which lithium (Li) is transferred to parts other than the portion where lithium (Li) is deposited, even when multiple lithium transfer release films of the present invention are laminated for convenience of use and separated again.

[0053] In addition, the lithium transfer release film and the method for manufacturing the same according to the present invention have low lithium peeling strength, so lithium can be easily transferred to the current collector even at low pressure and temperature.

[0054]

[0055] FIG. 1 is a cross-sectional view showing a lithium transfer release film on one side according to a preferred embodiment of the present invention.

[0056] FIG. 2 is a schematic diagram showing the observation of pinholes occurring in the deposited lithium after depositing lithium on one surface of a second release layer according to a preferred embodiment of the present invention and then irradiating a first release layer with white light.

[0057]

[0058] Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts unrelated to the explanation have been omitted to clearly explain the present invention, and the same reference numerals are assigned to identical or similar components throughout the specification.

[0059]

[0060] Referring to FIG. 1, the lithium transfer release film of the present invention may have a structure in which a first release layer (10), a base film (20), and a second release layer (30) are sequentially laminated.

[0061] The first release layer (10) is a film that not only improves the releaseability but also prevents lithium that can be deposited on the second release layer (30) from being transferred to the opposite side.

[0062] Additionally, the first release layer (10) may have a thickness of 0.05 to 5 μm, preferably 0.1 to 1 μm, and more preferably 0.1 to 0.3 μm. If the thickness is less than 0.05 μm, there may be a problem with increased release force, and if it exceeds 5 μm, there may be a problem with blocking.

[0063] Additionally, the first release layer (10) may contain silicon (Si) in an amount of 0.1 to 15 weight%, preferably 1 to 10 weight%, more preferably 2 to 7 weight%, and even more preferably 4 to 6 weight% with respect to the total weight%. If silicon is contained in an amount less than 0.1 weight%, there may be a problem of reduced lithium transfer prevention effect due to increased release force, and if silicon is contained in an amount exceeding 15 weight%, there may be a problem of the silicon (Si) component of the first release layer (10) being transferred to lithium that can be deposited on the second release layer (30).

[0064] The first release layer (10) may include a resin composition, and the resin composition may include a silicone-based resin in an amount of 10 to 70 weight%, preferably 30 to 70 weight%, more preferably 45 to 70 weight%, and even more preferably 55 to 65 weight% based on the total weight%. If the silicone-based resin is included in an amount of less than 10 weight%, there may be a problem with lithium (Li) that can be deposited on the second release layer (20) adhering to the first release layer (10), and if it is included in an amount exceeding 70 weight%, there may be a problem with the excessive silicone component of the first release layer (10) contaminating the lithium (Li) that can be deposited on the second release layer (20).

[0065] Meanwhile, the silicone resin may include one or more selected from addition-type silicone resin, condensation-type silicone resin, and UV-type silicone resin, and preferably may include an addition-type silicone resin.

[0066] In addition, the resin composition may include a silicone-based resin and a non-silicone-based resin, and the non-silicone-based resin may be included in an amount of 30 to 90 weight%, preferably 30 to 70 weight%, more preferably 30 to 55 weight%, and even more preferably 35 to 45 weight% based on the total weight% of the resin composition.

[0067] In addition, the non-silicone resin is a resin that does not contain silicon (Si) as a component, and may include one or more selected from cellulose resin, acrylate resin, melamine resin, and alkyd resin, and preferably may include cellulose resin.

[0068] Furthermore, the first release layer (10) may contain 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, with respect to 100 parts by weight of resin composition. If the catalyst is contained in an amount less than 0.1 parts by weight, there may be a problem of incomplete curing, and if it exceeds 5 parts by weight, there may be a problem of the peel strength rising above a certain level.

[0069] In addition, any catalyst commonly used in the industry may be used, and preferably may include platinum.

[0070] Furthermore, the first release layer (10) may contain 0.1 to 5 parts by weight, preferably 0.5 to 3.0 parts by weight, and more preferably 0.5 to 1.5 parts by weight of an adhesion enhancer with respect to 100 parts by weight of the resin composition. If the adhesion enhancer is contained in an amount less than 0.1 parts by weight, there may be a problem with poor adhesion between the first release layer (10) and the base film (20), and if it exceeds 5 parts by weight, there may be a problem with silicon (Si) contained in the first release layer (10) being transferred to the back surface (the surface on which the third release layer is formed) of the base film (20).

[0071] The adhesion enhancer is a material that improves the adhesion between the first release layer (10) and the base film (20), and any adhesion enhancer commonly used in the industry can be used, and preferably, it may include dimethyl epoxide-containing methylvinyl siloxane.

[0072] The base film (20) serves as a substrate for forming the first release layer (10) and the second release layer (30), as well as a substrate that enables uniform lithium deposition on the second release layer (30) and / or a support for transferring the lithium that can be deposited on the second release layer (30) to a current collector. Any base film material used in the industry can be used, and preferably, it may include one or more selected from PET (Polyethylene terephthalate), PP (Polypropylene), PBT (Polybutylene terephthalate), PEN (Polyethylene naphthalate), PI (Polyimide), and PE (Polyethylene), and more preferably, it may include PET.

[0073] Additionally, the base film (20) of the present invention may have a thickness of 10 to 250 μm, preferably 25 to 100 μm. If the thickness is less than 10 μm, there may be a problem of thermal deformation occurring in the base film (20) during a lithium (Li) deposition process performed at a high temperature, and if it exceeds 250 μm, there may be an economic problem.

[0074] The second release layer (30) is a layer that uniformly deposits lithium (Li) or smoothly transfers lithium (Li) to a current collector, and is a layer on which lithium is deposited on one surface to transfer lithium, and may include a silicon-based resin, preferably one or more selected from addition-reaction type silicon-based resin, condensation-reaction type silicon-based resin and UV-reaction type silicon-based resin, and preferably may include an addition-reaction type silicon-based resin.

[0075] Additionally, the second release layer (30) may have a thickness of 0.01 to 1 μm, preferably 0.05 to 0.5 μm, and more preferably 0.05 to 0.3 μm. If the thickness is less than 0.01 μm, there may be a problem with transfer failure, and if it exceeds 1 μm, there may be a problem with blocking occurring during winding.

[0076] Additionally, the second release layer (30) may contain silicon (Si) in an amount of 5.0 to 25 weight%, preferably 8.0 to 20 weight%, more preferably 10 to 15 weight%, and even more preferably 12 to 14 weight% with respect to the total weight%. If silicon is contained in an amount less than 5.0 weight%, there may be a problem of significantly reduced lithium transfer efficiency, and if it is contained in an amount exceeding 25 weight%, there may be a problem of increased pinhole occurrence rate in the deposited lithium when lithium is deposited on one surface of the second release layer.

[0077] Additionally, the second release layer (30) may contain 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, with respect to 100 parts by weight of silicone resin. If the catalyst is contained in an amount less than 0.1 parts by weight, there may be a problem of incomplete curing, and if it exceeds 5 parts by weight, there may be a problem of the release force rising above an appropriate level.

[0078] In addition, any catalyst commonly used in the industry may be used, and preferably may include platinum.

[0079] Furthermore, the second release layer (30) may contain 0.1 to 5 parts by weight, preferably 0.5 to 3.0 parts by weight, and more preferably 0.5 to 1.5 parts by weight of an adhesion enhancer with respect to 100 parts by weight of silicone resin. If the adhesion enhancer is contained in an amount less than 0.1 parts by weight, there may be a problem with poor adhesion between the second release layer (30) and the base film (20), and if it exceeds 5 parts by weight, there may be a problem with silicon (Si) contained in the second release layer (30) being transferred to the back surface (the surface on which the first release layer is formed) of the base film (20).

[0080] The adhesion enhancer is a material that improves adhesion between the second release layer (30) and the base film (20), and any adhesion enhancer commonly used in the industry can be used, and preferably, it may include dimethyl epoxide-containing methylvinyl siloxane.

[0081]

[0082] Meanwhile, the base film (20) and the first release layer (10) may have a thickness ratio of 1:0.0014 to 0.0026, preferably 1:0.0016 to 0.0024.

[0083] Additionally, the base film (20) and the second release layer (30) may have a thickness ratio of 1:0.001 to 0.0018, preferably 1:0.0011 to 0.0016.

[0084]

[0085] Meanwhile, the lithium transfer release film of the present invention can satisfy the following condition (1).

[0086] (1) A ≥ B

[0087] In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0088] If condition (1) is not satisfied, there may be a problem where the lithium deposited on the second layer is transferred to the first layer.

[0089] In addition, the lithium transfer release film of the present invention can further satisfy the following condition (2).

[0090] (2) B : A = 1 : 1.0 ~ 5.0, preferably B : A = 1 : 1.5 ~ 5.0, more preferably B : A = 1 : 2.5 ~ 5.0, even more preferably B : A = 1 : 3.5 ~ 4.5, even more preferably B : A = 1 : 3.5 ~ 4.0

[0091] In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0092] If B : A is less than 1 : 1.0, there may be a problem where lithium that can be deposited on the second release layer is transferred to the first release layer, and if it exceeds 1 : 5.0, the silicon (Si) content of the first release layer may increase, and the increased silicon (Si) content may cause a problem where silicon (Si) is transferred to the lithium surface that can be deposited on the second release layer.

[0093] In addition, the release force of the first release layer may be 10 to 60 gf / inch, preferably 20 to 55 gf / inch, more preferably 30 to 50 gf / inch, and even more preferably 40 to 45 gf / inch. If the release force of the first release layer is less than 10 gf / inch, there may be a problem that the excessive silicon component of the first release layer contaminates the lithium (Li) that can be deposited on the second release layer, and if it exceeds 60 gf / inch, there may be a problem that the lithium (Li) that can be deposited on the second release layer adheres to the first release layer.

[0094] In addition, the release force of the second release layer may be 1 to 40 gf / inch, preferably 3 to 30 gf / inch, more preferably 5 to 20 gf / inch, and even more preferably 8 to 14 gf / inch. If the release force of the second release layer is less than 1 gf / inch, there may be a problem with not uniformly depositing lithium (Li), and if it exceeds 40 gf / inch, there may be a problem with poor transfer performance of lithium (Li).

[0095] In addition, the lithium transfer release film of the present invention can further satisfy the following condition (3).

[0096] (3) C ≤ D

[0097] In the above condition (3), C represents the weight percentage of silicon (Si) contained in the first release layer and D represents the weight percentage of silicon (Si) contained in the second release layer. If the above condition (3) is not satisfied, there may be a problem where lithium (Li) that can be deposited on the second release layer adheres to the first release layer.

[0098]

[0099] Furthermore, referring to FIG. 2, the lithium transfer release film of the present invention has lithium (40) deposited on one surface of the second release layer (30) 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. After the lithium (40) is deposited, if white light is irradiated on the first release layer (10), the number of pinholes per unit area of ​​10 cm x 10 cm may be 100 or fewer. A pinhole refers to a pore that occurs in the lithium (40) during deposition. If more than 100 pinholes occur per unit area of ​​10 cm x 10 cm in the lithium (40), there may be a problem that the lithium (40) is not deposited uniformly. In addition, white light refers to light with a wavelength of 400 to 700 nm.

[0100]

[0101] Meanwhile, the method for manufacturing a lithium transfer release film of the present invention includes a first step and a second step.

[0102] First, the first step of the method for manufacturing a lithium transfer release film of the present invention may be to prepare a base film. At this time, the base film is as described above.

[0103] Next, the second step of the method for manufacturing a lithium transfer release film of the present invention may involve applying a composition for forming a first release layer to one side of a base film prepared in the first step and applying a composition for forming a second release layer to the other side of the base film, and then curing to form a first release layer on one side of the base film and a second release layer on the other side of the base film.

[0104] The composition for forming the first release layer may be a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent. Specifically, the composition for forming the first release layer may be a mixture comprising, with respect to 100 parts by weight of the resin composition, 0.1 to 5 parts by weight of 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 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 solvent, preferably 850 to 950 parts by weight. At this time, the catalyst and the adhesion enhancer are as described above. In addition, any solvent generally used in the industry may be used, and preferably, it may include one or more selected from toluene, MEK (Methyl Ethyl Keton), n-Hexane, and MIBK (Methyl Isobutyl Keton).

[0105] In addition, the resin composition may be a mixture of a silicone-based resin and a non-silicone-based resin, wherein the silicone-based resin may be mixed in an amount of 10 to 70 weight%, preferably 30 to 70 weight%, more preferably 45 to 70 weight%, and even more preferably 55 to 65 weight% based on the total weight% of the resin composition, and the non-silicone-based resin may be mixed in an amount of 30 to 90 weight%, preferably 30 to 70 weight%, more preferably 30 to 55 weight%, and even more preferably 35 to 45 weight% based on the total weight% of the resin composition. At this time, the silicone-based resin and the non-silicone-based resin are as described above.

[0106] In addition, the first release layer formed by curing the composition for forming the first release layer may contain silicon (Si) in an amount of 0.1 to 15 weight%, preferably 1 to 10 weight%, more preferably 2 to 7 weight%, and even more preferably 4 to 6 weight% with respect to the total weight%. In addition, the first release layer is as described above.

[0107] The composition for forming the second release layer may be a mixture of a silicone-based resin, a catalyst, an adhesion enhancer, and a solvent. Specifically, the composition for forming the second release layer may be a mixture comprising, with respect to 100 parts by weight of silicone-based resin, 0.1 to 5 parts by weight of 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 adhesion enhancer, preferably 0.5 to 3.0 parts by weight, more preferably 0.5 to 1.5 parts by weight, and 500 to 5000 parts by weight of solvent, preferably 550 to 4000 parts by weight. At this time, the catalyst and the adhesion enhancer are as described above. In addition, any solvent generally used in the industry may be used, and preferably, it may include one or more selected from toluene, MEK (Methyl Ethyl Keton), n-Hexane, and MIBK (Methyl Isobutyl Keton).

[0108] In addition, the second release layer formed by curing the composition for forming the second release layer may contain silicon (Si) in an amount of 5.0 to 25 weight%, preferably 8.0 to 20 weight%, more preferably 10 to 15 weight%, and even more preferably 12 to 14 weight%, based on the total weight%. Furthermore, the second release layer is as described above.

[0109] In addition, the second stage of curing can be performed at a temperature of 100 to 140°C, preferably 110 to 130°C, for 10 to 40 seconds, preferably 15 to 25 seconds. If the curing temperature is less than 100°C, there may be a problem of incomplete curing, and if it exceeds 140°C, there may be a problem of thermal deformation in the base film.

[0110] Furthermore, when lithium is deposited on one surface of a second 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, and then white light is irradiated on the first release layer, the number of pinholes in the deposited lithium can be 100 or fewer per unit area of ​​10 cm x 10 cm.

[0111] In addition, the lithium transfer release film produced by the method of producing the lithium transfer release film of the present invention can satisfy the following condition (1).

[0112] (1) A ≥ B

[0113] In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0114] In addition, the lithium transfer release film produced by the method for producing the lithium transfer release film of the present invention may further satisfy the following condition (2).

[0115] (2) B : A = 1 : 1.0 ~ 5.0, preferably B : A = 1 : 1.5 ~ 5.0, more preferably B : A = 1 : 2.5 ~ 5.0, even more preferably B : A = 1 : 3.5 ~ 4.5, even more preferably B : A = 1 : 3.5 ~ 4.0

[0116] In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

[0117]

[0118] Although the present invention has been described above with reference to embodiments, this is merely illustrative and does not limit the embodiments of the present invention. Those skilled in the art will understand that various modifications and applications not exemplified above are possible within the scope of the essential characteristics of the present invention. For example, each component specifically shown in the embodiments of the present invention may be modified and implemented. Furthermore, differences related to such modifications and applications should be interpreted as being included within the scope of the present invention as defined in the appended claims.

[0119]

[0120] Preparation Example 1-1: Preparation of a composition for forming a second release layer

[0121] A composition for forming a second release layer was 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 respect to 100 parts by weight of a silicone-based resin. At this time, an addition-reaction type silicone-based resin (Dimethyl, 5-hexenylmethyl siloxane) was used as the silicone-based resin, platinum was used as the catalyst, dimethyl, epoxide-containing methylvinyl siloxane was used as the adhesion enhancer, and toluene was used as the solvent.

[0122]

[0123] Preparation Example 1-2: Preparation of a composition for forming a second release layer

[0124] A composition for forming a second release layer was prepared by mixing 1.5 parts by weight of a catalyst, 1 part by weight of an adhesion enhancer, and 1,100 parts by weight of a solvent with respect to 100 parts by weight of a silicone-based resin. At this time, an addition-reaction type silicone-based resin (Dimethyl, 5-hexenylmethyl siloxane) was used as the silicone-based resin, platinum was used as the catalyst, dimethyl, epoxide-containing methylvinyl siloxane was used as the adhesion enhancer, and toluene was used as the solvent.

[0125]

[0126] Preparation Example 1-3: Preparation of a composition for forming a second release layer

[0127] A composition for forming a second release layer was prepared by mixing 1.5 parts by weight of a catalyst, 1 part by weight of an adhesion enhancer, and 3,500 parts by weight of a solvent with respect to 100 parts by weight of a silicone-based resin. At this time, an addition-reaction type silicone-based resin (Dimethyl, 5-hexenylmethyl siloxane) was used as the silicone-based resin, platinum was used as the catalyst, dimethyl, epoxide-containing methylvinyl siloxane was used as the adhesion enhancer, and toluene was used as the solvent.

[0128]

[0129] Preparation Example 1-4: Preparation of a composition for forming a second release layer

[0130] A composition for forming a second release layer was 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 respect to 100 parts by weight of a mixed composition. At this time, the mixed composition used consisted of 80% by weight of a silicone-based resin and 20% by weight of dimethylvinylated and trimethylated silica (CAS Reg. No. 68988-89-6) based on the total weight percentage; platinum was used as the catalyst; dimethyl methylvinyl siloxane with epoxide was used as the adhesion enhancer; and toluene was used as the solvent. Additionally, an addition-reaction type silicone-based resin (dimethyl, 5-hexenylmethyl siloxane) was used as the silicone-based resin.

[0131]

[0132] Preparation Example 2: Preparation of a composition for forming a first release layer

[0133] A composition for forming a first release layer was 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 respect to 100 parts by weight of a resin composition. At this time, a mixture of 60% by weight of a silicone-based resin and 40% by weight of a non-silicone-based resin was used as the resin composition based on the total weight%, platinum was used as the catalyst, dimethyl methylvinyl siloxane with epoxide was used as the adhesion enhancer, and toluene was used as the solvent. In addition, an addition-reaction type silicone-based resin (dimethyl, 5-hexenylmethyl siloxane) was used as the silicone-based resin, and a cellulose resin was used as the non-silicone-based resin.

[0134]

[0135] Example 1: Preparation of a release film for lithium transfer

[0136] (1) A PET (Polyethylene terephthalate) film (XD510P, TAK) with a thickness of 75㎛ was prepared as a base film.

[0137] (2) Using a bar coater, a first release layer forming composition prepared in Preparation Example 2 was applied to one side of a prepared base film, and a second release layer forming composition prepared in Preparation Example 1-1 was applied to the other side of the base film, and then cured at a temperature of 120°C for 20 seconds and aged at a temperature of 40°C for 2 days to form a first release layer with a thickness of 0.15 μm on one side of the base film and a second release layer with a thickness of 0.1 μm on the other side of the base film, thereby producing a lithium transfer release film.

[0138]

[0139] Example 2: Preparation of a release film for lithium transfer

[0140] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Example 1-2 was used instead of the second release layer forming composition prepared in Preparation Example 1-1, and a second release layer with a thickness of 0.08 μm was formed to finally produce a lithium transfer release film.

[0141]

[0142] Example 3: Preparation of a release film for lithium transfer

[0143] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Example 1-3 was used instead of the second release layer forming composition prepared in Preparation Example 1-1, and a second release layer with a thickness of 0.025 μm was formed to finally produce a lithium transfer release film.

[0144]

[0145] Example 4: Preparation of a release film for lithium transfer

[0146] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Example 1-4 was used instead of the second release layer forming composition prepared in Preparation Example 1-1, and a second release layer with a thickness of 0.1 μm was formed to finally produce a lithium transfer release film.

[0147]

[0148] Example 5: Preparation of a release film for lithium transfer

[0149] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Examples 1-4 was used instead of the first release layer forming composition prepared in Preparation Example 2, and a first release layer with a thickness of 0.1 μm was formed to finally produce a lithium transfer release film.

[0150]

[0151] Example 6: Preparation of a release film for lithium transfer

[0152] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Examples 1-3 was used instead of the first release layer forming composition prepared in Preparation Example 2, and a first release layer with a thickness of 0.1 μm was formed to finally produce a lithium transfer release film.

[0153]

[0154] Example 7: Preparation of a release film for lithium transfer

[0155] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Example 1-2 was used instead of the first release layer forming composition prepared in Preparation Example 2, and a first release layer with a thickness of 0.1 μm was formed to finally produce a lithium transfer release film.

[0156]

[0157] Example 8: Preparation of a release film for lithium transfer

[0158] A lithium transfer release film was prepared in the same manner as in Example 1. However, unlike in Example 1, a second release layer forming composition prepared in Preparation Example 1-1 was used instead of the first release layer forming composition prepared in Preparation Example 2, and a first release layer with a thickness of 0.1 μm was formed to finally produce a lithium transfer release film.

[0159]

[0160] Comparative Example 1: Preparation of a release film for lithium transfer

[0161] (1) A PET (Polyethylene terephthalate) film (XD510P, TAK) with a thickness of 75㎛ was prepared as a base film.

[0162] (2) A second release layer forming composition prepared in Preparation Example 1-4 was applied to one side of a prepared base film using a bar coater, then cured at a temperature of 120°C for 20 seconds and aged at a temperature of 40°C for 2 days to form a second release layer with a thickness of 0.1 μm on one side of the base film, thereby producing a lithium transfer release film.

[0163]

[0164] Experimental Example 1: Evaluation of annealing properties and whether lithium was transferred to the first release layer

[0165] Lithium was deposited to a thickness of 5 μm on one surface of the second release layer of each lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1 using a Physical Vapor Deposition (PVD) method. Two lithium transfer release films with deposited lithium were laminated, and 2 kg / cm² 2 After applying a load to the lithium formed on the surface of the lithium transfer release film, the film was left at a temperature of 40°C for 2 days. Subsequently, when separating the two stacked lithium transfer release films, the releaseability was evaluated as follows: ◎ if no sticky sound occurred, ○ if only a very faint sticky sound occurred, and Ⅹ if a loud sticky sound occurred; the results are shown in Tables 1 and 2 below. In addition, after evaluating the releaseability, it was checked whether lithium had been transferred to the first release layer of the separated lithium transfer release film; the transferability was evaluated as follows: ○ if no lithium occurred, and Ⅹ if lithium occurred; the results are shown in Tables 1 and 2 below.

[0166]

[0167] Experimental Example 2: Measurement of Pinhole Count

[0168] Lithium was deposited to a thickness of 5 μm on one side of the second release layer of each lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1 using a PVD (Physical Vapor Deposition) method. Then, after irradiating the first release layer of each lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1 with white light, the deposited lithium was observed visually, and the number of pinholes per unit area of ​​10 cm x 10 cm is shown in Tables 1 and 2.

[0169]

[0170] Experimental Example 3-1: Measurement of release force of the first release layer

[0171] After attaching an acrylic adhesive tape (TESA7475) with a width of 25 mm x a length of 175 mm to the first release layer of the lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1, the release force of the first release layer of the lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1 was measured according to the Finat-10 evaluation method and is shown in Tables 1 and 2 below.

[0172]

[0173] Experimental Example 3-2: Measurement of release force of the second release layer

[0174] After attaching an acrylic adhesive tape (TESA7475) with a width of 25 mm x a length of 175 mm to the second release layer of the lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1, the release force of the second release layer of the lithium transfer release film prepared in Examples 1 to 8 and Comparative Example 1 was measured according to the Finat-10 evaluation method and is shown in Tables 1 and 2 below.

[0175]

[0176] Experimental Example 4: Measurement of Silicon (Si) Content

[0177] Using a scanning electron microscope (SEM) equipped with EDS (Energy Dispersive X-ray Spectroscopy), the silicon (Si) content contained in the first release layer and the second release layer of the lithium transfer release films prepared in Examples 1 to 8 and Comparative Example 1 was measured and is shown in Tables 1 and 2 below.

[0178]

[0179] Experimental Example 5: Measurement of Lithium Transfer Efficiency

[0180] In Examples 1 to 8 and Comparative Example 1, lithium was deposited to a thickness of 5 μm on one side of the second release layer of each lithium transfer release film prepared using the PVD (Physical Vapor Deposition) method. Then, the lithium deposited on the lithium transfer release film was roll-laminated onto one side of a copper foil (Cu foil) used as a negative electrode current collector, and the lithium transfer release film was removed to transfer the lithium to the copper foil. After transfer, the area of ​​lithium remaining on the lithium transfer release film was visually inspected, and the lithium transfer efficiency was calculated using the following formula 1 and is shown in Tables 1 and 2 below.

[0181] [Formula 1]

[0182] Lithium Transfer Efficiency (%) = (Area of ​​lithium deposited on the lithium transfer release film - Area of ​​lithium remaining on the lithium transfer release film after transferring the lithium deposited on the lithium transfer release film to the copper foil) / Area of ​​lithium deposited on the lithium transfer release film

[0183]

[0184] Experimental Example 6: Measurement of Lithium Peeling Strength

[0185] In Examples 1 to 8 and Comparative Example 1, lithium was deposited to a thickness of 10 μm on one side of the second release layer of each lithium transfer release film using the PVD (Physical Vapor Deposition) method. Then, Kapton tape was attached to one side of the lithium in a size of 25 mm x 175 mm, and after leaving it for 30 minutes, the lithium (Li) peel strength was measured according to the Finat-10 evaluation method and is shown in Tables 1 and 2 below.

[0186]

[0187]

[0188]

[0189] As can be seen in Tables 1 and 2, the lithium transfer release film prepared in Example 1 not only has excellent unwindability, but also does not transfer lithium to the first release layer, has a pin hole count of 100 or less, has excellent lithium transfer efficiency, and has low lithium peeling force, so that lithium can be easily transferred to the current collector even at low pressure and temperature.

[0190]

[0191] Experimental Example 6: Measurement of Pinhole Count

[0192] Lithium was deposited on one surface of the second release layer of the lithium transfer release film prepared in Example 1 using a Physical Vapor Deposition (PVD) method to thicknesses of 5 μm, 10 μm, 15 μm, 20 μm, and 30 μm, respectively. Then, white light was irradiated onto the first release layer of each of the lithium transfer release films prepared in Example 1, on which lithium was deposited at different thicknesses, and the deposited lithium was observed visually. The number of pinholes per unit area of ​​10 cm x 10 cm is shown in Table 3.

[0193]

[0194] As can be seen in Table 3, it was confirmed that even when lithium was deposited on one side of the second release layer of the lithium transfer release film prepared in Example 1 with thicknesses of 5㎛, 10㎛, 15㎛, and 20㎛, the number of pinholes per unit area of ​​10cm x 10cm was 100 or less. However, when lithium was deposited on one side of the second release layer of the lithium transfer release film prepared in Example 1 with a thickness of 30㎛, it was confirmed that thermal deformation occurred during the deposition process.

[0195]

[0196] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be within the scope of the present invention.

Claims

1. A lithium transfer release film comprising a first release layer; a base film; and a second release layer, wherein these are sequentially laminated, A lithium transfer release film characterized by satisfying the following condition (1). (1) A ≥ B In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

2. In Paragraph 1, A lithium transfer release film characterized by further satisfying the following condition (2). (2) B : A = 1 : 1.0 ~ 5.0 In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

3. In Paragraph 1, A lithium transfer release film characterized by the fact that, after depositing lithium to a thickness of 2 to 25 μm on one surface of the second release layer, white light is irradiated onto the first release layer, resulting in 100 or fewer pinholes per unit area of ​​10 cm x 10 cm occurring in the deposited lithium.

4. In Paragraph 3, A lithium transfer release film characterized by the fact that, after depositing lithium to a thickness of 2 to 8 μm on one surface of the second release layer, white light is irradiated onto the first release layer, and the number of pinholes in the deposited lithium is 100 or fewer per unit area of ​​10 cm x 10 cm.

5. In Paragraph 1, The above first release layer comprises a resin composition, and A lithium transfer release film characterized by the above resin composition containing 10 to 70 weight percent of a silicone-based resin based on the total weight percent.

6. In Paragraph 5, A lithium transfer release film characterized in that the first release layer comprises 0.1 to 5 parts by weight of a catalyst and 0.1 to 5 parts by weight of an adhesion enhancer, based on 100 parts by weight of a resin composition.

7. In Paragraph 1, The first release layer above contains silicon (Si) in an amount of 0.1 to 15 weight% based on the total weight%, and The second release layer above contains silicon (Si) in an amount of 5.0 to 25 weight% based on the total weight%, and A lithium transfer release film characterized by satisfying the following condition (3). (3) C ≤ D In the above condition (3), C represents the weight percentage of silicon (Si) contained in the first release layer, and D represents the weight percentage of silicon (Si) contained in the second release layer.

8. In Paragraph 1, A lithium transfer release film characterized by the above base film comprising one or more selected from PET (Polyethylene terephthalate), PP (Polypropylene), PBT (Polybutyleneterephthalate), PEN (Polyethylene naphthalate), PI (Polyimide), and PE (Polyethylene).

9. In Paragraph 5, The above resin composition includes a silicone-based resin and a non-silicone-based resin, and The above silicone-based resin comprises one or more types selected from addition-reaction type silicone-based resins, condensation-reaction type silicone-based resins, and UV-reaction type silicone-based resins, and A lithium transfer release film characterized by comprising one or more types selected from cellulose resin, acrylate resin, melamine resin, and alkyd resin.

10. A first step of preparing a base film; and A second step comprising applying a composition for forming a first release layer to one side of the base film and applying a composition for forming a second release layer to the other side of the base film, and then curing to form a first release layer on one side of the base film and a second release layer on the other side of the base film; A method for manufacturing a lithium transfer release film characterized by satisfying the following condition (1). (1) A ≥ B In the above condition (1), A represents the release force of the first release layer, and B represents the release force of the second release layer.

11. In Paragraph 10, A method for manufacturing a lithium transfer release film characterized by further satisfying the following condition (2). (2) B : A = 1 : 1.0 ~ 5.0 In the above condition (2), A represents the release force of the first release layer, and B represents the release force of the second release layer.

12. In Paragraph 10, A method for manufacturing a lithium transfer release film characterized by depositing lithium to a thickness of 2 to 25 μm on one surface of the second release layer, and then irradiating the first release layer with white light, such that 100 or fewer pinholes occur per unit area of ​​10 cm x 10 cm in the deposited lithium.

13. In Paragraph 10, The above composition for forming the first release layer is a mixture of a resin composition, a catalyst, an adhesion enhancer, and a solvent, and A method for manufacturing a lithium transfer release film, characterized in that the resin composition comprises 10 to 70 weight percent of a silicone-based resin mixed with respect to the total weight percent.

14. In Paragraph 13, A method for manufacturing a lithium transfer release film, characterized in that the composition for forming the first release layer is mixed with 0.1 to 5 parts by weight of a catalyst, 0.1 to 5 parts by weight of an adhesion enhancer, and 800 to 1000 parts by weight of a solvent, based on 100 parts by weight of a resin composition.

15. In Paragraph 10, A method for manufacturing a lithium transfer release film, characterized by performing the above curing at a temperature of 100 to 140℃ for 10 to 40 seconds.

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