Antistatic release film for solid-state battery electrode casting and preparation method

Abstract

The application discloses a kind of solid battery electrode casting with antistatic release film, comprising: substrate layer, at least one surface is provided with antistatic layer;Release layer is connected with at least one antistatic layer;Antistatic layer is prepared by drying antistatic coating solution, and the main raw material of antistatic coating solution is antistatic agent, modified silicon dioxide and isopropyl alcohol;Antistatic agent is siloxane antistatic agent;Release layer is prepared by curing release agent coating solution, and the main raw material of release agent coating solution is main agent silicone oil, crosslinking agent, anchoring agent, catalyst, inhibitor and solvent.The solid battery electrode casting with antistatic release film includes substrate layer, antistatic layer and release layer, and the raw material of antistatic coating solution includes siloxane antistatic agent, not only gives the antistatic property of release film, and the adhesion of silicone oil type release layer and antistatic layer is good, also effectively improves the residual sticking rate of release film.

Description

Technical Field

[0001] This invention relates to the field of thin film materials technology, specifically to an antistatic release film for solid-state battery electrode casting and its preparation method. Background Technology

[0002] Solid-state battery electrode processing typically involves coating a slurry onto a substrate and then drying and curing it to obtain the electrode substrate. The substrate includes a release layer, which is in direct contact with the electrode substrate. Therefore, the surface smoothness of the release layer and the thermal stability of the substrate directly affect the uniformity of the electrode substrate surface, thereby affecting the capacity, internal resistance, and safety of the final battery product.

[0003] Conventional substrates consist of a release film composed of a substrate layer and a release layer. The release layer is a silicone oil-containing release layer. While the release film itself does not possess conductive properties, static electricity is generated during the battery electrode manufacturing process. The accumulation of static electricity can easily damage the internal structure of the battery electrode. Furthermore, the silicone oil-containing release layer can cause silicon transfer, which can negatively impact the battery electrode, such as causing contamination.

[0004] Therefore, it is necessary to improve the release film in the existing technology. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide an antistatic release film for solid-state battery electrode casting. By using a siloxane-based antistatic agent, not only is the release film given antistatic properties, but the silicone oil-based release layer also has good adhesion to the antistatic layer, effectively improving the residual adhesion rate of the release film.

[0006] To achieve the above-mentioned process effects, the technical solution of the present invention is: an antistatic release film for solid-state battery electrode casting, comprising:

[0007] The substrate layer has an antistatic layer on at least one surface;

[0008] A release layer, connected to at least one of the aforementioned antistatic layers;

[0009] The antistatic layer is obtained by drying an antistatic coating liquid, the main raw materials of which are antistatic agent and isopropanol;

[0010] The antistatic agent is a siloxane-based antistatic agent;

[0011] The release layer is obtained by curing a release agent coating liquid, the main raw materials of which are silicone oil, crosslinking agent, anchoring agent, catalyst, inhibitor and solvent.

[0012] The preferred technical solution is that the mass ratio of antistatic agent to isopropanol in the antistatic coating liquid is 1:(1-3).

[0013] Furthermore, the mass ratio of antistatic agent to isopropanol in the antistatic coating solution is 1:

[0014] (1~2).

[0015] The preferred technical solution is as follows: by mass parts, the main raw materials of the release agent coating liquid are 100 parts of the main agent silicone oil, 0.8 to 1.6 parts of the crosslinking agent, 0.3 to 0.9 parts of the anchoring agent, 1.5 to 2.2 parts of the catalyst, 1 to 2 parts of the inhibitor, and 2500 to 3500 parts of the solvent.

[0016] Furthermore, by mass fraction, the main raw materials of the release agent coating liquid are: 100 parts of main agent silicone oil, 0.9 to 1.5 parts of crosslinking agent, 0.4 to 0.8 parts of anchoring agent, 1.6 to 2 parts of catalyst, 1 to 2 parts of inhibitor, and 2500 to 3300 parts of solvent.

[0017] The preferred technical solution is that the antistatic agent is COLCOAT-N-103X.

[0018] The preferred technical solution is that the main silicone oil is Dow Corning LTC-750A and / or Dow Corning SLY-OFF 7458.

[0019] The preferred technical solution is that the solvent includes toluene, butanone, and n-heptane; further, the mass ratio of toluene, butanone, and n-heptane is (1.7-4):(4.5-11):1.

[0020] Furthermore, the mass ratio of toluene, butanone, and n-heptane is (2-4):(6-11):1.

[0021] The preferred technical solution is that the crosslinking agent is Dow Corning 7672 and / or Dow Corning 7028, and the anchoring agent is Dow Corning 297 and / or Dow Corning 9176.

[0022] The second objective of this invention is to overcome the deficiencies in the prior art and provide a method for preparing an antistatic release film for solid-state battery electrode casting, comprising the following steps:

[0023] S1: Preparation of antistatic coating liquid and release agent coating liquid;

[0024] S2: The antistatic coating liquid is applied to at least one surface of the substrate layer and cured for the first time to obtain a film with an antistatic layer;

[0025] S3: The release agent coating liquid is coated on the surface of at least one layer of the antistatic layer, and then cured for the second time to obtain a release film semi-finished product with a release layer;

[0026] S4: Curing the semi-finished release film to obtain an antistatic release film.

[0027] The preferred technical solution is that the temperature of the first curing is set sequentially as follows: 70±5℃, 95±5℃, 110±5℃, 110±5℃, 110±5℃, 95±5℃;

[0028] The temperatures for the second curing were set sequentially as follows: 70±5℃, 95±5℃, 110±5℃, 125±5℃, 120±5℃, and 95±5℃.

[0029] The preferred technical solution is that the ripening temperature in S4 is 60-65℃.

[0030] Furthermore, the thickness of the obtained antistatic layer is 0.1–0.3 μm, and the thickness of the obtained release layer is 0.1–0.4 μm.

[0031] The advantages and beneficial effects of this invention are as follows:

[0032] The antistatic release film for solid-state battery electrode casting includes a substrate layer, an antistatic layer, and a release layer. The raw materials of the antistatic coating liquid include siloxane-based antistatic agents, which not only impart antistatic properties to the release film, but also ensure good adhesion between the silicone oil-based release layer and the antistatic layer, effectively improving the residual adhesion rate of the release film. The antistatic layer obtained by coating with a mixture of siloxane-based antistatic agents and isopropanol has uniform conductivity and a smooth film surface, which is conducive to the formation of a well-adhered release layer. Detailed Implementation

[0033] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solution of the present invention and should not be construed as limiting the antistatic coating liquid.

[0034] The main raw materials are antistatic agent and isopropanol, and the antistatic agent is COLCOAT-N-103X.

[0035] The addition of isopropanol improves the uniformity of antistatic coating. Excessive addition of isopropanol can lead to the leaching of effective components from the antistatic agent; insufficient addition results in poor leveling of the antistatic coating, making it prone to pinholes and orange peel texture when applied to the substrate.

[0036] Release agent coating liquid

[0037] The main raw materials are silicone oil, crosslinking agent, anchoring agent, catalyst, inhibitor and solvent.

[0038] Silicone oil, the main agent, is the most important raw material in the formulation, affecting the release force performance, stability, and smoothness of the release layer. Good adhesion between the main agent and the antistatic layer, along with low-temperature curing, effectively avoids defects such as release film shrinkage after heat curing, which is beneficial for the casting of solid-state battery electrodes. Excessive addition of crosslinking agent leads to a large increase in release force during aging; insufficient addition results in incomplete curing and unusable release film. Excessive addition of anchoring agent reduces the reaction rate, or even prevents normal curing; insufficient addition reduces the adhesion between the release layer and the antistatic layer, and also lowers the residual adhesion rate. Excessive addition of platinum catalyst increases the cost of the release film, causes excessively fast reaction of the release agent coating solution, shortens the lifespan of the coating solution, easily produces gel-like material that cannot be processed, and accelerates the aging of the resulting release film; insufficient addition of platinum catalyst prevents normal curing. If too much inhibitor is added, the release film will not cure; if too little inhibitor is added, the release force of the release film will decrease over time.

[0039] solvent

[0040] The release agent mixture includes toluene, methyl ethyl ketone (MEK), and n-heptane. Insufficient toluene addition hinders the dissolution of the silicone oil, while excessive toluene can cause pinholes in the release agent coating before curing, resulting in pinholes when applied to the antistatic layer. Excessive MEK addition can also lead to pinholes on the release film surface; insufficient MEK addition slows evaporation and hinders low-temperature curing. Excessive n-heptane addition can cause rainbow-like patterns on the release film surface; insufficient n-heptane addition results in poor leveling properties and increases the likelihood of pinholes when applied to the antistatic layer.

[0041] A method for preparing an antistatic release film for solid-state battery electrode casting includes the following steps: S1: preparing an antistatic coating liquid and a release agent coating liquid;

[0042] S2: Apply the antistatic coating liquid to at least one surface of the substrate, and cure it for the first time to obtain a film with an antistatic layer. The coating method is oblique micro-recessed coating with a screen of 150 or 200 lines and a coating speed of 35 to 45 m / min. Cure it in an oven with 6 sections, each section being 4 meters long. The first curing temperature is set sequentially as follows: 70±5℃, 95±5℃, 110±5℃, 110±5℃, 110±5℃, 95±5℃.

[0043] S3: Apply the release agent coating liquid to the surface of at least one antistatic layer, and cure it a second time to obtain a release film semi-finished product with a release layer. The coating method is hexagonal micro-recessed coating, the mesh size is 400 mesh or 500 mesh, and the coating speed is 35-45 m / min. Cure it in an oven with 6 sections, each section being 4 meters long. The temperatures for the second curing are set sequentially as follows: 70±5℃, 95±5℃, 110±5℃, 125±5℃, 120±5℃, 95±5℃.

[0044] S4: Curing release film semi-finished product to obtain antistatic release film. The curing temperature is 60-64℃ and the curing time is more than 24 hours.

[0045] The curing process in S4 effectively reduces the internal stress of the substrate layer and the main silicone oil, which helps the adhesion between the main silicone oil and the antistatic layer, and between the antistatic layer and the substrate layer. At the same time, it can hydrolyze the residual curing agent, optimize the aging stability of the release film, prevent the phenomenon of aging ramp-up during the use of the release film, and improve the phenomenon that the release film is difficult to peel off from the battery electrode as the bonding time increases.

[0046] The structure of an antistatic release film consists of, from bottom to top, a substrate layer, an antistatic layer, and a release layer.

[0047] Structure 2 of antistatic release film: Antistatic layers are provided on both sides of the substrate layer, and a release layer is provided on one surface of the antistatic layer. The antistatic release film is double-sided antistatic.

[0048] The structure of the antistatic release film consists of three layers: from the inside out, a substrate layer, an antistatic layer, and a release layer. The antistatic layer and the release layer are symmetrically disposed on the two surfaces of the substrate layer, making the antistatic release film double-sided antistatic.

[0049] The formulations of the antistatic coating liquid and release agent coating liquid in the examples and comparative examples, by weight, are shown in Table 1 below:

[0050]

[0051]

[0052] The substrate has a surface roughness Ra≤40nm and is heat resistant.

[0053] The mass ratio of the solvents toluene, butanone, and n-heptane is 7:20:3.

[0054] A method for preparing an antistatic release film for solid-state battery electrode casting, based on the structure of an antistatic release film, which comprises, from bottom to top, a stacked substrate layer, an antistatic layer, and a release layer, includes the following steps:

[0055] S1: Prepare the antistatic coating liquid and release agent coating liquid according to Table 1 above;

[0056] S2: Apply the antistatic coating liquid to the surface of the substrate and cure it for the first time to obtain a film with an antistatic layer. The coating method is oblique micro-recessed coating with a screen of 150 lines and a coating speed of 40m / min. Cure it in an oven with 6 sections, each section being 4 meters long. The first curing temperature is set sequentially as follows: 70℃, 95℃, 110℃, 110℃, 110℃, 95℃.

[0057] S3: Apply the release agent coating liquid to the surface of the antistatic layer, and cure it a second time to obtain the semi-finished release film. The coating method is hexagonal micro-recessed coating with a mesh size of 400 and a coating speed of 40 m / min. Cure it in an oven with 6 sections, each 4 meters long. The curing temperatures for the second curing are set sequentially as follows: 70℃, 95℃, 110℃, 125℃, 120℃, and 95℃. S4: Curl the semi-finished release film to obtain the antistatic release film. The curing temperature is 60℃ and the curing time is 24 hours.

[0058] Example 5

[0059] The structure of the antistatic release film consists of, from bottom to top, a stacked substrate layer, an antistatic layer, and a release layer.

[0060] A method for preparing an antistatic release film for solid-state battery electrode casting includes the following steps:

[0061] S1: Prepare the antistatic coating liquid and release agent coating liquid according to the proportions in Example 1 of Table 1 above;

[0062] S2: Apply the antistatic coating liquid to the surface of the substrate and cure it for the first time to obtain a film with an antistatic layer. The coating method is oblique micro-recessed coating with a screen of 150 lines and a coating speed of 40m / min. Cure it in an oven with 6 sections, each section being 4 meters long. The first curing temperature is set sequentially as follows: 70℃, 95℃, 110℃, 110℃, 110℃, 95℃.

[0063] S3: Apply the release agent coating liquid to the surface of the antistatic layer, and cure it a second time to obtain the release film semi-finished product. The coating method is hexagonal micro-recessed coating, the mesh size is 400 mesh, and the coating speed is 40m / min. Cure it in an oven with 6 sections, each section is 4 meters long. The second curing temperature is set sequentially as follows: 90℃, 115℃, 130℃, 140℃, 130℃, 115℃.

[0064] S4: Curing release film semi-finished product to obtain antistatic release film. The curing temperature is 60℃ and the curing time is 24h.

[0065] Example 6

[0066] The structure of the antistatic release film consists of, from bottom to top, a stacked substrate layer, an antistatic layer, and a release layer.

[0067] A method for preparing an antistatic release film for solid-state battery electrode casting includes the following steps:

[0068] S1: Prepare the antistatic coating liquid and release agent coating liquid according to the proportions in Example 1 of Table 1 above;

[0069] S2: Apply the antistatic coating liquid to the surface of the substrate and cure it for the first time to obtain a film with an antistatic layer. The coating method is oblique micro-recessed coating with a screen of 150 lines and a coating speed of 40m / min. Cure it in an oven with 6 sections, each section being 4 meters long. The first curing temperature is set sequentially as follows: 70℃, 95℃, 110℃, 110℃, 110℃, 95℃.

[0070] S3: Apply the release agent coating liquid to the surface of the antistatic layer, and cure it a second time to obtain the release film semi-finished product. The coating method is hexagonal micro-recessed coating, the mesh size is 400 mesh, and the coating speed is 40m / min. Cure it in an oven with 6 sections, each section is 4 meters long. The second curing temperature is set sequentially as follows: 70℃, 95℃, 110℃, 110℃, 110℃, 95℃.

[0071] S4: Curing release film semi-finished product to obtain antistatic release film. The curing temperature is 30℃ and the curing time is 24h.

[0072] Example 7

[0073] The structure of the antistatic release film consists of, from bottom to top, a stacked substrate layer, an antistatic layer, and a release layer.

[0074] The antistatic coating liquid and release agent coating liquid were prepared according to the ratio in Example 1 of Table 1 above. The thickness of the antistatic layer was 0.2 μm and the thickness of the release layer was 1 to 2 μm. Under the condition that the temperature of the second curing remained unchanged, the release layer was not cured well, which also led to poor adhesion to the antistatic layer.

[0075] In order to further solidify the thicker release layer, the temperature of the second curing is increased to above 140°C. The resulting release layer is thick, the surface roughness of the release film is poor (i.e., the roughness Ra is greater than 40), and the peeling force of the resulting release film is too weak. When preparing solid battery electrode casting, the battery electrode casting slurry is prone to fail to adhere to the initially shaped electrode preform, resulting in poor applicability of the release film.

[0076] Testing method for antistatic release film samples used in solid-state battery electrode casting:

[0077] 1. Release force test tool: Tesa 7475 tape; Method: Peel at 300mm / min, 180°.

[0078] 2. Residual adhesion rate test tool: Nitto 31B tape;

[0079] 3. Resistance standard: ASTM D257; Instrument: American TREK 152-1 surface resistivity tester;

[0080] 4. Release film surface roughness: The KEYENCE non-contact roughness tester was used.

[0081] 5. Tensile strength: Test standard ASTM D-882;

[0082] The measurement results of the examples and comparative examples are shown in Table 2 below:

[0083]

[0084] A superior release film meets the following conditions: surface roughness Ra≤40nm; light transmittance≥90%; haze≤6%; longitudinal tensile strength≥150MPa, transverse tensile strength≥150MPa; release force at room temperature and release force after aging are both 6~12g / inch; residual adhesion rate≥90%. Among these, the tensile strength is mainly determined by the substrate material of the substrate layer.

[0085] Compared to Example 1, the release film obtained by using Dow Corning SLY-OFF 7458 as the main agent in Example 2 had a slightly lower residual adhesion rate, while other properties were comparable.

[0086] Compared to Example 1, the release films obtained by Dow Corning LTC-750A with Dow Corning 7672 crosslinking agent and Dow Corning 297 anchoring agent in Examples 3 and 4 showed better residual adhesion.

[0087] Compared to Example 1, in Example 5, after the second curing temperature was increased, the residual adhesion rate of the release film was improved, but the surface of the release film shrank, and lines appeared in the MD direction of the release film, resulting in poor surface smoothness of the release film.

[0088] Compared to Example 1, Example 6 showed a lower curing temperature, incomplete hydrolysis of the crosslinking agent, and a significant increase in release force after aging of the release film.

[0089] Compared to Example 1, Comparative Example 1 showed poor uniformity in the distribution of the antistatic coating liquid during application, resulting in large pinholes with large areas and diameters. After drying, the antistatic coating liquid formed a mesh-like texture, leading to uneven antistatic performance of the resulting antistatic layer and poor overall antistatic properties of the release film. During the rub-off test, localized rub-off phenomena occurred.

[0090] Compared to Example 1, Comparative Example 2 used a mixture of ethanol solvent and antistatic agent. Even when cured at a relatively low temperature of 110°C, the solvent still evaporated too quickly, resulting in an orange peel-like appearance in the cured antistatic layer.

[0091] Compared to Example 1, Comparative Example 3 showed better film-forming properties of the antistatic coating liquid, but the resulting antistatic layer exhibited a small number of pinholes after curing, and the pore size was relatively small. During the rub-off test, localized rub-off occurred, and the rub-off area was smaller than that of Comparative Example 1.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An antistatic release film for solid-state battery electrode casting, comprising: a substrate layer, at least one surface of which is provided with an antistatic layer; a release layer connected to the at least one antistatic layer; characterized in that the antistatic layer is prepared by drying an antistatic coating solution, raw materials of the antistatic coating solution being an antistatic agent and isopropyl alcohol in a mass ratio of 1: (1.8-3); the antistatic agent being COLCOAT-N-103X; the release layer being prepared by curing a release agent coating solution, raw materials of the release agent coating solution being, in terms of mass fraction, 100 parts of a main agent silicone oil, 0.8-1.6 parts of a crosslinking agent, 0.3-0.9 parts of an anchoring agent, 1.5-2.2 parts of a catalyst, 1-2 parts of an inhibitor, and 2500-3500 parts of a solvent; the main agent silicone oil being Dow Corning LTC-750A or Dow Corning SLY-OFF 7458; the solvent including toluene, butanone, and n-heptane.

2. The solid-state battery electrode flow casting antistatic release film according to claim 1, characterized by, the mass ratio of the toluene, butanone, and n-heptane being (1.7-4): (4.5-11):

1.

3. The solid-state battery electrode casting antistatic release film according to claim 1, characterized by, the crosslinking agent being Dow Corning 7672 and / or Dow Corning 7028, and the anchoring agent being Dow Corning 297 and / or Dow Corning 9176.

4. A method for producing the antistatic release film for electrode casting of a solid-state battery according to any one of claims 1 to 3, characterized by, comprising the following steps: S1: preparing an antistatic coating solution and a release agent coating solution; S2: coating the antistatic coating solution on at least one surface of the substrate layer to obtain a thin film with the antistatic layer by first curing; S3: coating the release agent coating solution on the surface of the at least one antistatic layer to obtain a release film semi-finished product with the release layer by second curing; S4: aging the release film semi-finished product to obtain the antistatic release film.

5. The method for producing a solid-state battery electrode flow casting antistatic release film according to claim 4, characterized by, the first curing being performed in an oven with six sections, the temperatures of the six sections being set as 70±5℃, 95±5℃, 110±5℃, 110±5℃, 110±5℃, and 95±5℃ in sequence; the second curing being performed in an oven with six sections, the temperatures of the six sections being set as 70±5℃, 95±5℃, 110±5℃, 125±5℃, 120±5℃, and 95±5℃ in sequence.

6. The method for producing a solid-state battery electrode flow casting antistatic release film according to claim 4, characterized by, the aging temperature in S4 being 60-65℃.

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