Composite release film for lithium ion battery processing, processing technology and application

Abstract

This invention discloses a composite release film assembly for lithium-ion battery processing. The key technical points are: it includes a release film A and a release film B, each comprising a film body, a release layer, and a protective film. The film body has a coated surface and an uncoated surface, respectively. The release layer is attached to the coated surface of the film body, and the protective film is separable and laminated to the uncoated surface of the film body. The invention also discloses the processing technology of this composite release film for lithium-ion battery processing. Based on the above solution, the application of the composite release film assembly in rolling ultra-thin lithium foil strips is also disclosed. A protective film is laminated to the uncoated surface of the release film. During winding, the silicone oil from the coated surface is transferred to the surface of the protective film instead of to the uncoated surface. During the rolling of the ultra-thin lithium foil strip, the protective film is first peeled off before entering the rolling mill. This effectively avoids the relative slippage between the film and the pressure rollers caused by the transfer of silicone to the uncoated surface.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery processing technology, specifically to a composite release film, processing technology, and application for lithium-ion battery processing. Background Technology

[0002] Ultra-thin lithium foil strips, used as battery anodes, can significantly improve battery energy density. Currently, the technology of rolling lithium foil strips into ultra-thin strips for use as anodes in solid-state batteries is receiving increasing attention due to its ability to significantly improve battery performance.

[0003] In the process of rolling lithium foil strips into ultra-thin lithium foil strips, the use of release film assemblies for protecting and supporting the lithium foil strip is widely adopted. However, due to the silicone transfer problem of the release film—that is, the silicone oil on the coated side of the release film partially transfers to the uncoated side during winding—the presence of silicone oil on the uncoated side during lithium foil strip rolling causes relative slippage between the pressure roller and the release film when they come into contact. This relative slippage causes the lithium strip to wrinkle and deform, significantly impacting production stability. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the background art described above, by providing a composite release film assembly for lithium-ion battery processing, and disclosing the processing technology of this composite release film for lithium-ion battery processing. A protective film is laminated onto the uncoated side of the release film. During winding, the silicone oil from the coated side is transferred to the surface of the protective film instead of to the uncoated side. When rolling ultra-thin lithium foil strips, the protective film is first peeled off before entering the rolling mill. This effectively avoids the problem of relative slippage between the film and the pressure rollers caused by silicone transfer to the uncoated side.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] A composite release film assembly for lithium-ion battery processing includes a release film A and a release film B. Both release film A and release film B comprise a film body, a release layer, and a protective film. The two sides of the film body are a coated side and an uncoated side, respectively. The release layer is attached to the coated side of the film body, and the protective film is separable and laminated to the uncoated side of the film body.

[0007] Furthermore, the parameters of the release agent for release film A and release film B are designed as follows:

[0008] Release film A: The release force of the release layer is 4-6 g / in, the residual adhesion rate is 60%-80%, and the dry coating amount of the release agent is 0.4-0.6 g / m. 2 ;

[0009] Release film B: The release force of the release layer is 3-5 g / in, the residual adhesion rate is 80%-100%, and the dry coating amount of the release agent is 0.8-1.2 g / m. 2 .

[0010] Furthermore, the protective film is a PE film, which is attached and fixed to the uncoated surface of the film body by a second unwinding system.

[0011] This invention discloses a processing technology for a composite release film used in lithium-ion battery manufacturing, comprising the following steps:

[0012] 1) Release agent preparation;

[0013] 2) First unwinding: Select PET film as the main body of the film and unwind the PET film placed on the roll.

[0014] 3) Coating: The release agent prepared in step 1) is coated on one surface of the unwound film body;

[0015] 4) Drying: Use an oven to dry and cure the release agent coated on the surface of the film body;

[0016] 5) Second unwinding: Using PE film as a protective film, the PE film placed on the roll is unwound;

[0017] 6) Lamination: The membrane body exiting the oven is laminated with the unwound PE film, with the PE film attached to the uncoated side of the membrane body;

[0018] 7) Cooling: After the composite membrane substrate and PE membrane are cooled, a composite membrane is formed;

[0019] 8) Rewinding: The cooled composite film is then rewound.

[0020] Furthermore, two different ratios of release agents were coated onto the membrane substrate to prepare release film A and release film B, respectively.

[0021] The release agent used for release film A (1a) includes a silicone oil system and a solvent. The silicone oil system is formulated as follows: 1000 parts of silicone oil main agent, 15-25 parts of crosslinking agent, 5-15 parts of anchoring agent, 15-30 parts of catalyst, and 15-25 parts of peel strength additive.

[0022] The release agent used for release film B (1b) includes a silicone oil system and a solvent. The silicone oil system is formulated as follows: 1000 parts of silicone oil main agent, 15-25 parts of crosslinking agent, 5-15 parts of anchoring agent, 15-30 parts of catalyst, and 5-15 parts of anti-sticking agent.

[0023] Furthermore, two different ratios of release agents were coated onto the membrane substrate to prepare release film A and release film B, respectively.

[0024] For the release agent used in release film A, its 20-minute release force is 4-6 g / in, the residual adhesion rate is 60%-80%, and the dry coating amount of the release agent is 0.4-0.6 g / m. 2 ;

[0025] For the release agent used in release film B, its 20-minute release force is 3-5 g / in, the residual adhesion rate is 80%-100%, and the dry coating amount of the release agent is 0.8-1.2 g / m. 2 .

[0026] This invention also discloses the application of the above-mentioned composite release film assembly for lithium-ion battery processing in the rolling of ultrathin lithium foil strips, specifically including:

[0027] The raw material used for rolling ultra-thin lithium foil strip is thick lithium strip; the equipment used includes a same-speed rolling device and a protective film separation device. The same-speed rolling device includes at least one set of pressure roller mechanism, which includes two rollers with the same speed but opposite rotation directions, and a rolling channel is formed between the two rollers; the specific application of this composite release film combination in rolling ultra-thin lithium foil strip is as follows: release film A, release film B and thick lithium strip pass through the rolling channel of the same-speed rolling device for rolling and thinning. The thick lithium strip is sandwiched between release film A and release film B. The coating surface of release film A faces one surface of the thick lithium strip, and the coating surface of release film B faces the other surface of the thick lithium strip. Before entering the same-speed rolling device, release film A and release film B are stripped of their protective film by the protective film separation device. After the same-speed rolling device, an ultra-thin lithium foil strip with release film A and release film B attached to both sides respectively is produced.

[0028] For release film A / release film B in the winding state, the coated side and the uncoated side are isolated by a protective film. The silicone oil on the coated side is transferred to the surface of the protective film instead of being transferred to the uncoated side. When rolling ultra-thin lithium foil, the uncoated sides of release film A and release film B contact the rollers on both sides of the rolling channel to eliminate the defect of relative slippage between the uncoated side and the rollers due to the silicone oil adhering to it. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the release membrane A / release membrane in an embodiment of the present invention.

[0030] Figure 2 This is a process flow diagram of the composite release film assembly in an embodiment of the present invention.

[0031] Figure 3 This is a schematic diagram illustrating the application of the composite release film combination in an embodiment of the present invention.

[0032] Reference numerals: 1a, Release film A; 1b, Release film B; 10, PET transparent film; 11, Release layer; 12, PE protective film; 2, Thick lithium strip; 20, Ultra-thin lithium foil strip; 3, Same speed rolling device; 30, Roller; 4, Rewinding drum. Detailed Implementation

[0033] The present invention will now be further described with reference to the accompanying drawings.

[0034] like Figure 1 The composite release film assembly shown for lithium-ion battery processing includes release film A 1a and release film B 1b. Both release film A 1a and release film B 1b comprise a film body, a release layer 11, and a protective film. The film body is a PET transparent film 10, and the protective film is a PE protective film 12. The PET transparent film 10 has two coated and uncoated sides, respectively. The release layer 11 is attached to the coated side of the PET transparent film 10, and the PE protective film 12 is separable and laminated to the uncoated side of the PET transparent film 10. Release film A 1a and release film B 1b are distinguished by coating with different proportions of release agent.

[0035] For the release layer 11 of release film A 1a, an organosilicon-based release agent is used. The silicone oil system of this release agent is formulated as follows: 1000 parts of silicone oil main agent, 20 parts of crosslinking agent, 8 parts of anchoring agent, 22 parts of catalyst, and 30 parts of peel strength additive. The silicone oil main agent is a reactive siloxane polymer (Dow, 9106), the crosslinking agent is a SiH functional siloxane (Dow, 7028), the anchoring agent is a composite organofunctional siloxane (Dow, 9176), the catalyst is an organoplatinum compound (Dow, 4000), and the peel strength additive is a silicone resin solution (Dow, 7200). The solvent used in this release agent is a mixture of ethyl acetate and 120# solvent oil in a ratio of ethyl acetate: 120# solvent oil = 7:3. The 20-minute release force of the release layer 11 of release film A1a is 4.2 g / in, the residual adhesion (SA) is 70%, and the dry coating weight is 0.55 g / m. 2 .

[0036] The specific parameters of the release layer 11 of release film A 1a are shown in Table 1 below:

[0037]

[0038] Table 1

[0039] For the release layer 11 of release film B1b, an organosilicon-based release agent is used. The silicone oil system of this release agent is formulated as follows: 1000 parts silicone oil main agent, 21 parts crosslinking agent, 8 parts anchoring agent, 24 parts catalyst, and 9 parts anti-sticking agent. The silicone oil main agent is a reactive siloxane polymer (Dow, 9106), the crosslinking agent is a SiH-functionalized siloxane (Dow, 7028), the anchoring agent is a composite organofunctionalized siloxane (Dow, 9176), and the catalyst is an organoplasmic compound (Dow, 4000). The solvent used in this release agent is a mixture of ethyl acetate and 120# solvent oil in a ratio of ethyl acetate:120# solvent oil = 7:3. The 20-minute release force of the release layer 11 of release film B1b is 4.5 g / in, the residual adhesion (SA) is 99%, and the dry coating weight is 0.88 g / m. 2 .

[0040] The parameters of the release agent used in release film B1b are shown in Table 2 below:

[0041]

[0042] Table 2

[0043] like Figure 2 The processing technology shown is for the composite release film used in lithium-ion battery manufacturing. This technology can process release film A1a and release film B1b, and specifically includes the following steps:

[0044] 1) Release agent preparation:

[0045] For processing release film A1a, the silicone oil system of the release agent is formulated as follows: 1000 parts reactive siloxane polymer (Dow, 9106), 20 parts SiH functional siloxane (Dow, 7028), 8 parts complex organofunctional siloxane (Dow, 9176), 22 parts organoplatinum compound (Dow, 4000), and 30 parts silicone resin solution (Dow, 7200). The solvent is a mixture of ethyl acetate and 120# solvent oil in a ratio of ethyl acetate: 120# solvent oil = 7:3.

[0046] For processing release film B1b, the silicone oil system of the release agent is formulated as follows: 1000 parts reactive siloxane polymer (Dow, 9106), 21 parts SiH functional siloxane (Dow, 7028), 8 parts complex organofunctional siloxane (Dow, 9176), 24 parts organoplatinum compound (Dow, 4000), and 9 parts anti-sticking agent. The solvent is a mixture of ethyl acetate and 120# solvent oil in a ratio of ethyl acetate: 120# solvent oil = 7:3.

[0047] 2) First unwinding: Select PET transparent film 10 as the main body of the film and perform unwinding operation on the PET transparent film 10 placed on the roll;

[0048] 3) Coating:

[0049] The release agent prepared in step 1) for processing release film A 1a is coated onto the coating surface of the unwound PET transparent film 10 using a micro-recessed reverse coating method. The 20-minute release force is 4.2 g / in, the residual adhesion (SA) is 70%, and the dry coating amount of the release agent is 0.55 g / m². 2 ;

[0050] The release agent prepared in step 1) for processing release film B1b is coated onto the coating surface of the unwound PET transparent film 10 using a micro-recessed reverse coating method. The 20-minute release force is 4.5 g / in, the residual adhesion (SA) is 99%, and the dry coating weight of the release agent is 0.88 g / m². 2 ;

[0051] 4) Drying: Use an oven to dry and cure the release agent coated on the surface of the PET transparent film 10. The oven has 8 zones, the temperature is 80℃-150℃, and the drying time is 30 seconds.

[0052] 5) Second unwinding: Using PE film as a protective film, the PE film placed on the roll is unwound;

[0053] 6) Lamination: The PET transparent film 10 exiting the oven is laminated with the unwound PE film. The lamination method is roller pressing, and the PE film is attached to the uncoated side of the PET transparent film 10.

[0054] 7) Cooling: After the composite PET transparent film 10 and PE film are cooled, a composite film (including release film A 1a and release film B 1b) is formed.

[0055] 8) Rewinding: The cooled release film A1a and release film B1b are rewound separately.

[0056] like Figure 3 As shown, the application of the aforementioned composite release film assembly for lithium-ion battery processing in the rolled ultrathin lithium foil strip 20 includes the following specific details:

[0057] The raw material used for rolling the ultra-thin lithium foil strip 20 is a thick lithium strip 2. Release film A 1a and release film B 1b need to be rolled and fixed on the two surfaces of the ultra-thin lithium foil strip 20 to protect and support the ultra-thin lithium foil strip 20. The equipment used includes a rolling device 3 with the same speed and a protective film separation device. The rolling device 3 with the same speed includes a set of pressure roller mechanism, which includes two rollers 30 with the same speed but opposite rotation directions. A rolling channel is formed between the two rollers 30. The protective film separation device includes two winding drums 4, which are driven to rotate by a motor.

[0058] The specific application of this composite release film assembly on rolled ultra-thin lithium foil strip 20 is as follows:

[0059] Release film A 1a, release film B 1b, and thick lithium strip 2 are rolled thin by passing through the rolling channel of the same-speed rolling device 3. The thick lithium strip 2 is sandwiched between release film A 1a and release film B 1b, with the coated surface of release film A 1a facing one surface of the thick lithium strip 2, and the coated surface of release film B 1b facing the other surface of the thick lithium strip 2. Two take-up drums 4 are respectively positioned on the sides of release film A 1a and release film B 1b. Release film A 1a and release film B 1b pass through the take-up drums 4 before entering the same-speed rolling device 3. P on release film A 1a... The PE protective film 12 is peeled off from the PET transparent film 10 and wound onto the corresponding winding drum 4. The PE protective film 12 on the release film B 1b is peeled off from the PET transparent film 10 and wound onto the corresponding winding drum 4. During the process of the release film A 1a and release film B 1b entering the rolling channel with the thick lithium strip 2, the PE protective film 12 of the release film A 1a and release film B 1b is continuously peeled off by the winding drum 4. After the same speed rolling device 3, an ultra-thin lithium foil strip 20 with the release film A 1a and release film B 1b peeled off on both sides is formed.

[0060] For release film A1a / release film B1b in the winding state, the coated surface and the uncoated surface are isolated by a protective film. The silicone oil on the coated surface is transferred to the surface of the protective film instead of being transferred to the uncoated surface. When rolling ultra-thin lithium foil, the uncoated surfaces of release film A1a and release film B1b contact the rollers 30 on both sides of the rolling channel to eliminate the defect of relative slippage between the uncoated surface and the rollers 30 due to the silicone oil adhering to it.

[0061] The above are preferred embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the principle of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A composite release film assembly for lithium-ion battery processing, characterized in that: It includes a release A film (1a) and a release B film (1b), both of which include a film body, a release layer (11) and a protective film. The two sides of the film body are coated and uncoated, respectively. The release layer (11) is attached to the coated side of the film body, and the protective film can be separated and laminated to the uncoated side of the film body. Two release agents in different ratios were coated onto the membrane body to prepare release film A (1a) and release film B (1b) respectively. For the release agent used in release film A (1a), its 20-minute release force is 4-6 g / in, the residual adhesion rate is 60%-80%, and the dry coating amount of the release agent is 0.4-0.6 g / m. 2 ; For the release agent used in release film B (1b), its 20-minute release force is 3-5 g / in, the residual adhesion rate is 80%-100%, and the dry coating amount of the release agent is 0.8-1.2 g / m. 2 ; The protective film is a PE protective film (12), which is attached and fixed to the uncoated surface of the film body by a second unwinding system; The processing technology for composite release films used in lithium-ion battery manufacturing includes the following steps: 1) Release agent preparation; 2) First unwinding: Select PET film as the main body of the film and unwind the PET film placed on the roll. 3) Coating: The release agent prepared in step 1) is coated on one surface of the unwound film body; 4) Drying: Use an oven to dry and cure the release agent coated on the surface of the film body; 5) Second unwinding: PE film is selected as the protective film, and the PE protective film (12) placed on the roll is unwound; 6) Lamination: The membrane body exiting the oven is laminated with the unwound PE protective film (12), and the PE protective film (12) is attached to the uncoated surface of the membrane body; 7) Cooling: After the composite membrane body and PE protective film (12) are cooled, a composite membrane is formed; 8) Rewinding: The cooled composite film is then rewound.

2. The processing technology of the composite release film for lithium-ion battery processing according to claim 1, characterized in that: Two release agents in different ratios were coated onto the membrane body to prepare release film A (1a) and release film B (1b) respectively. The release agent used for release film A (1a) includes a silicone oil system and a solvent. The silicone oil system is formulated as follows: 1000 parts of silicone oil main agent, 15-25 parts of crosslinking agent, 5-15 parts of anchoring agent, 15-30 parts of catalyst, and 15-25 parts of peel strength additive. The release agent used for release film B (1b) includes a silicone oil system and a solvent. The silicone oil system is formulated as follows: 1000 parts of silicone oil main agent, 15-25 parts of crosslinking agent, 5-15 parts of anchoring agent, 15-30 parts of catalyst, and 5-15 parts of anti-sticking agent.

3. The application of composite release film assemblies for lithium-ion battery processing in the rolling of ultra-thin lithium foil strips, characterized in that: The composite release film assembly comprises the release film A (1a) and release film B (1b) as described in claim 1; the raw material used for rolling the ultrathin lithium foil strip (20) is a thick lithium strip (2); the equipment used includes a rolling device (3) with the same speed and a protective film separation device, the rolling device (3) with the same speed includes at least one set of pressure roller mechanism, the pressure roller mechanism includes two rollers (30) with the same speed but opposite rotation directions, and a rolling channel is formed between the two rollers (30); the specific application of this composite release film assembly in rolling the ultrathin lithium foil strip (20) is as follows: the release film A (1a), the release film B (1b) and the thick lithium strip (2) together The thick lithium strip (2) is rolled thin by passing through the rolling channel of the same speed rolling device (3). The thick lithium strip (2) is sandwiched between release film A (1a) and release film B (1b). The coating surface of release film A (1a) faces one surface of the thick lithium strip (2), and the coating surface of release film B (1b) faces the other surface of the thick lithium strip (2). Before entering the same speed rolling device (3), both release film A (1a) and release film B (1b) are stripped of their protective film by a protective film separation device. After the same speed rolling device (3), an ultra-thin lithium foil strip (20) is made with release film A (1a) and release film B (1b) with the protective film stripped on both sides respectively.

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