A low-silicon-extraction silica gel protective film for copper foil and a preparation method thereof

Abstract

The application discloses a low-silica gel release protective film for copper foil and a preparation method thereof. The protective film comprises a double-resistant PET substrate layer, a low-silica gel layer and a release layer which are sequentially stacked. The low-silica gel layer is formed by coating and curing silica gel pressure-sensitive adhesive. The silica gel pressure-sensitive adhesive comprises methyl vinyl silicone rubber, vinyl polysiloxane, methyl hydrogen-containing MQ silicone resin, side-chain hydrogen-containing polymethyl hydrogen siloxane, low-release additive, platinum gold catalyst, inhibitor and solvent. The low-release additive comprises fumed silica treated by hexamethyldisilazane and vinyl-containing cage-type silsesquioxane. The application realizes the inhibition of small molecule release from the source, effectively guarantees the coating uniformity of lithium battery copper foil and the safety performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of thin film technology, and in particular to a low-precipitation silicone protective film for copper foil and its preparation method. Background Technology

[0002] Copper foil is a key material for the negative electrode current collector in lithium-ion batteries. Its surface dyne value (surface tension) directly affects the uniformity of the battery slurry coating and the adhesion of the electrode, thus affecting the cycle life and safety of the battery. During the production, slitting, transportation, and storage of copper foil, a protective film is usually used to cover its surface to prevent oxidation, scratches, and contamination.

[0003] Currently, commercially available protective films, especially in high temperature and high humidity environments, generally have the following defects after being applied to copper foil: small molecules such as silicone oil in the protective film precipitate out and migrate to the surface of the copper foil, causing a significant decrease in its dyn value (usually below 28 dyn); the peeling force of the protective film increases significantly with aging time (more than 200%), and even delamination and residue may occur, causing irreversible damage to the copper foil. Summary of the Invention

[0004] This invention provides a low-precipitation silicone copper foil protective film for copper foil and its preparation method, in order to solve the technical problems of small molecules easily precipitating in the protective film under high temperature and high humidity conditions, which leads to a decrease in the dyne value of the copper foil and unstable peel strength.

[0005] In a first aspect, the present invention provides a low-exudation silicone protective film for copper foil, comprising a double-anti-PET substrate layer, a low-exudation silicone layer, and a release layer sequentially stacked thereon. The low-exudation silicone layer is formed by coating and curing a silicone pressure-sensitive adhesive, wherein the silicone pressure-sensitive adhesive comprises the following raw material components in parts by mass: 35 to 45 parts of methyl vinyl silicone rubber; 15 to 25 parts of vinyl polysiloxane; 25 to 35 parts of methyl hydrogen-containing MQ silicone resin; Side chain hydrogen-containing polymethylhydrosiloxane 0.5 parts to 2.5 parts; 8 to 18 parts of low-precipitation additive; Platinum catalyst 0.3 to 0.6 parts; Inhibitor 0.08 to 0.12 parts; The solvent makes the solid content of the silicone pressure-sensitive adhesive 28%~32%; The low-precipitation additives include fumed silica surface-treated with hexamethyldisilazane and vinyl-containing cage-like silsesquioxanes.

[0006] Preferably, the molar ratio of Si-H to Si-Vi in the system is 1.2~2. The dual-antistatic PET substrate can be an antistatic and antioxidant PET substrate, and the release layer can be a PET release film.

[0007] In some embodiments, the low-exudation additive comprises 6 to 12 parts of fumed silica surface-treated with hexamethyldisilazane and 2 to 4 parts of vinyl-containing cage-like silsesquioxane, wherein the mass ratio of the surface-treated fumed silica to vinyl POSS is (3 to 6): 1. Treatment with hexamethyldisilazane trimethylsilanizes the silica surface, resulting in extremely low residual silanol content and excellent compatibility with silicone rubber.

[0008] In some embodiments, the specific surface area of ​​the fumed silica is 200±30m² / g; the vinyl-containing cage-like silsesquioxane is octavinyl cage-like silsesquioxane (octavinyl-POSS) with a purity ≥95%, and is dried to remove moisture before use.

[0009] In some embodiments, the methyl vinyl silicone rubber has a molecular weight of 50W~120W, a vinyl molar fraction of 0.1%~1.2%, and a total D3~D10 cyclosiloxane content ≤1wt%. Methyl vinyl silicone rubber (raw rubber) is the main film-forming material that forms the cohesive strength of the pressure-sensitive adhesive. It can be a linear polydimethylsiloxane containing methyl and vinyl groups directly bonded to silicon atoms in its molecular chain. The molecular weight is preferably 65W~85W, and the vinyl molar fraction is preferably 0.15%~0.5%. To reduce the precipitation of molecular rings, low-cyclic raw rubber that has undergone low-molecular-weight removal treatment is preferred, and its total D3~D10 cyclosiloxane content is preferably ≤0.5%.

[0010] In some embodiments, the vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s to 5000 mPa·s and a vinyl molar fraction of 0.2% to 0.5%. The vinyl polysiloxane serves as an active diluent and network regulator in the system, participating in the hydrosilylation reaction to adjust the crosslinking density and the flexibility of the pressure-sensitive adhesive. Preferably, the vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane with one vinyl group at each end, and its viscosity (at 25°C) is preferably 2000 mPa·s to 4000 mPa·s; the vinyl molar fraction is preferably 0.25% to 0.4%.

[0011] In some embodiments, the M / Q ratio of the methyl hydrogen-containing MQ silicone resin is 0.6 to 0.85, and the active hydrogen content is 0.02 wt% to 0.05 wt%. The methyl hydrogen-containing MQ silicone resin is composed of monofunctional repeating units (M units, mainly trimethylsiloxy groups) and tetrafunctional repeating units (Q units, silicon dioxide / siloxane network), and its structure also contains active hydrogen (Si-H) directly bonded to silicon. The methyl hydrogen-containing MQ silicone resin has both reinforcing and cross-linking functions, and the M / Q molar ratio is preferably 0.65 to 0.8; the active hydrogen content (i.e., the mass percentage of Si-H groups) is preferably 0.03 wt% to 0.04 wt%.

[0012] In some embodiments, the viscosity of the side-chain hydrogen-containing polymethylhydrosiloxane is 20 mPa·s to 100 mPa·s, and the active hydrogen content is 0.3 wt% to 0.8 wt%. The side-chain hydrogen-containing polymethylhydrosiloxane, as an auxiliary crosslinking agent, can provide more dispersed Si-H groups, participate in the construction of the crosslinking network, and fine-tune the peeling force; the molecular structure is linear polymethylhydrosiloxane, with Si-H mainly located in the side chain; the viscosity (25°C) is preferably 30 mPa·s to 800 mPa·s, and the active hydrogen content is preferably 0.4 wt% to 0.7 wt%.

[0013] In some embodiments, the inhibitor is 1-ethynyl-1-cyclohexanol with a purity ≥99%; the platinum catalyst is a caster catalyst (platinum-divinyltetramethyldisiloxane complex) with a platinum content of 3000ppm~5000ppm; the solvent includes at least one of toluene, xylene and ethyl acetate, preferably a mixture of toluene and ethyl acetate in a ratio of (1~3):1.

[0014] Secondly, the present invention also provides a method for preparing a low-deposition silicone protective film for copper foil, comprising the following steps: Methyl vinyl silicone rubber was dissolved in a portion of the solvent to obtain the first mixture; Vinyl polysiloxane, methyl hydrogen MQ silicone resin, low precipitation additive and residual solvent are mixed and dispersed in a planetary mixer or high-speed disperser at 1000 rpm to 2500 rpm for 15 min to 30 min (or by ultrasonic dispersion), and then transferred to a three-roll mill or sand mill to grind to a fineness ≤10 μm to obtain a second mixture. Combine the first mixture and the second mixture, add the inhibitor, stir evenly, add the side-chain hydrogen-containing polymethylhydrosiloxane and platinum catalyst, mix evenly (50rpm~150rpm, 15min~20min) and degas under vacuum (-0.09MPa~-0.1MPa, 5min~15min) to obtain silicone pressure-sensitive adhesive. The silicone pressure-sensitive adhesive is coated onto the surface of the dual-resistance PET substrate layer (pre-treated with corona to a surface dyn value ≥50 dyn / cm), cured for 2 min to 5 min through multiple drying tunnels (first stage 80℃~100℃, second stage 120℃~130℃, third stage 150℃~160℃), then a release layer is attached, and cured at 40℃~55℃ for 24 h~48 h to obtain a low-exudation silicone protective film for copper foil.

[0015] Thirdly, the present invention also provides the application of a low-deposition silicone protective film for copper foil in the preparation of a negative electrode current collector for lithium-ion batteries.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Based on methyl vinyl silicone rubber and terminal vinyl polysiloxane, the polymers are cured via platinum-catalyzed hydrosilylation reaction. MQ resin has a tight core-shell structure, which not only acts as a reinforcing resin to improve cohesion, but also its multifunctional Si-H groups participate in crosslinking to form rigid nodes. The side-chain hydrogen-containing siloxane provides dispersion crosslinking points, making the network more compact. The fumed silica surface treated with hexamethyldisilazane is highly hydrophobic, and it physically adsorbs and locks in low molecular weight silicone oil in the form of a nanoparticle network, reducing its migration. Vinyl-containing cage-like silsesquioxane (POSS) has a cubic cage-like rigid structure, and its multiple vinyl groups can participate in the crosslinking reaction, embedding themselves in the network in the form of nanoscale nodes, significantly improving the crosslinking density and reducing the free volume. It blocks the silicone oil precipitation path at the molecular scale, thereby inhibiting the precipitation of small molecules from the source and effectively ensuring the coating uniformity of lithium battery copper foil and the battery safety performance. Detailed Implementation

[0017] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] As used herein, the terms “prepared from” and “comprising” are synonymous. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0019] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, it should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Unless otherwise specified, the raw materials used in the following examples and comparative examples are commercially available industrial products or prepared by conventional methods, and conditions not specifically stated are conventional conditions. Example 1

[0021] The silicone pressure-sensitive adhesive comprises the following raw material components in parts by weight: 35 parts of methyl vinyl silicone rubber (molecular weight 700,000, vinyl molar fraction 0.1%, D3~D10 cyclic content 0.3wt%); Vinyl-terminated polydimethylsiloxane (viscosity 1000 mPa·s, vinyl molar fraction 0.2%) 15 parts; 35 parts of methyl hydrogen-containing MQ silicone resin (M / Q ratio 0.75, active hydrogen content 0.05wt%); 2.5 parts of hydrogen-containing polymethylhydrosiloxane with side chain (viscosity 50 mPa·s, active hydrogen content 0.8 wt%); Six parts of fumed silica (specific surface area 200 m² / g) surface-treated with hexamethyldisilazane; Two parts of octavinyl POSS (purity ≥95%); 0.5 parts of caster catalyst (platinum content 5000ppm); 0.1 parts of 1-ethynyl-1-cyclohexanol (purity ≥99%); Use an appropriate amount of solvent (toluene: ethyl acetate = 2:1) to make the solid content of the adhesive solution 30%.

[0022] Preparation method of low-exudation silica gel protective film: Dissolve methyl vinyl silicone rubber in half of the mixed solvent and stir until completely dissolved to obtain the first mixture. The vinyl-terminated polydimethylsiloxane, methyl hydrogen MQ silicone resin, surface-treated fumed silica, octavinyl POSS and the remaining solvent were mixed and dispersed at high speed of 1500 rpm for 20 min, and then ground with a three-roll mill until the fineness was ≤10 μm to obtain the second mixture. Combine the first and second mixtures, add the inhibitor and stir until homogeneous; then add the side-chain hydrogen-containing silicone oil and the caster catalyst, stir at 80 rpm for 15 min, and degas under vacuum (-0.095 MPa, 10 min) to obtain the silicone pressure-sensitive adhesive. The adhesive is applied to a double-resistant PET substrate that has been corona-treated (surface dyn value ≥50 dyn / cm), cured in three drying tunnels (100℃, 125℃, 150℃) for 3 minutes, cooled, and then laminated with a release film. The film is then cured in a 50℃ oven for 48 hours to obtain a low-exudation silicone protective film. Example 2

[0023] The silicone pressure-sensitive adhesive comprises the following raw material components in parts by weight: 45 parts of methyl vinyl silicone rubber (molecular weight 800,000, vinyl molar fraction 0.5%, D3~D10 cyclic 0.5wt%); Vinyl-terminated polydimethylsiloxane (viscosity 4000 mPa·s, vinyl molar fraction 0.4%) 25 parts; 35 parts of methyl hydrogen-containing MQ silicone resin (M / Q ratio 0.8, active hydrogen content 0.05wt%); 2.5 parts of hydrogen-containing polymethylhydrosiloxane with side chain (viscosity 80 mPa·s, active hydrogen content 0.8 wt%); 12 parts of fumed silica (220 m² / g) surface-treated with hexamethyldisilazane; Octadecylvinyl POSS (purity ≥95%) 2 parts; 0.5 parts of caster catalyst (platinum content 5000ppm); 0.1 parts of 1-ethynyl-1-cyclohexanol (purity ≥99%); Use an appropriate amount of solvent (toluene: ethyl acetate = 3:1) to make the solid content of the adhesive solution 30%.

[0024] Preparation method of low-precipitation silica protective film: same as in Example 1, except that the oven temperature is adjusted to 90℃, 120℃, and 155℃, and the curing conditions are adjusted to 55℃ and 36h. Example 3

[0025] The silicone pressure-sensitive adhesive comprises the following raw material components in parts by weight: 35 parts of methyl vinyl silicone rubber (molecular weight 600,000, vinyl molar fraction 0.1%, D3~D10 cyclic 0.3wt%); Vinyl-terminated polydimethylsiloxane (viscosity 2000 mPa·s, vinyl molar fraction 0.2%) 15 parts; 35 parts of methyl hydrogen-containing MQ silicone resin (M / Q ratio 0.75, active hydrogen content 0.05wt%); 2.5 parts of hydrogen-containing polymethylhydrosiloxane with side chain (viscosity 100 mPa·s, active hydrogen content 0.8 wt%); Eight parts of fumed silica (200 m² / g) surface-treated with hexamethyldisilazane; Octadecylvinyl POSS (purity ≥95%) 2.2 parts; 0.5 parts of caster catalyst (platinum content 5000ppm); 0.1 parts of 1-ethynyl-1-cyclohexanol (purity ≥99%); Use an appropriate amount of solvent (toluene:xylene = 1:1) to make the solid content of the adhesive solution 29%.

[0026] Preparation method of low-precipitation silicone protective film: Same as Example 1, except that the second mixture is ground to a fineness of ≤5μm, cured in the oven at 100℃, 130℃ and 150℃ for 4min, and aged at 45℃ for 48h. Example 4

[0027] The silicone pressure-sensitive adhesive comprises the following raw material components in parts by weight: 35 parts of methyl vinyl silicone rubber (molecular weight 650,000, vinyl molar fraction 0.1%, D3~D10 cyclic 0.3wt%); Vinyl-terminated polydimethylsiloxane (viscosity 3000 mPa·s, vinyl molar fraction 0.2%) 15 parts; 35 parts of methyl hydrogen-containing MQ silicone resin (M / Q ratio 0.7, active hydrogen content 0.05wt%); 2.5 parts of hydrogen-containing polymethylhydrosiloxane with side chain (viscosity 60 mPa·s, active hydrogen content 0.8 wt%); Six parts of fumed silica (200 m² / g) surface-treated with hexamethyldisilazane; Octadecylvinyl POSS (purity ≥95%) 2.4 parts; 0.5 parts of caster catalyst (platinum content 5000ppm); 0.1 parts of 1-ethynyl-1-cyclohexanol (purity ≥99%); Use an appropriate amount of solvent (toluene: ethyl acetate = 1:1) to make the solid content of the adhesive solution 31%.

[0028] Preparation method of low-precipitation silica protective film: same as in Example 1, except that it is degassed under vacuum of -0.1MPa for 15 min and cured at 40℃ for 48 h.

[0029] Comparative Example 1 The difference from Example 1 is that Comparative Example 1 replaces octavinyl POSS with surface-treated fumed silica.

[0030] Comparative Example 2 The difference from Example 1 is that Comparative Example 2 replaces the surface-treated fumed silica with octavinyl POSS.

[0031] Comparative Example 3 The difference from Example 1 is that Comparative Example 3 uses surface-treated fumed silica instead of untreated fumed silica (200 m² / g).

[0032] Comparative Example 4 The difference from Example 1 is that the methyl vinyl silicone rubber in Comparative Example 4 was replaced with raw rubber (molecular weight 700,000, vinyl molar fraction 0.1%, D3~D10 cyclic content 2.5wt%).

[0033] Comparative Example 5 The difference from Example 1 is that the 2.5 parts of side-chain hydrogen-containing polymethylhydrosiloxane in Comparative Example 5 were replaced with 40 parts of methyl hydrogen-containing MQ silicone resin with the same active hydrogen content.

[0034] Comparative Example 6 The difference from Example 1 is that Comparative Example 6 removes the side chain hydrogen-containing polymethylhydrosiloxane and uses methyl hydrogen-containing MQ silicone resin with an active hydrogen content of 0.107%.

[0035] Performance testing: 1. Silicon precipitation rate test: Take a copper foil (circular diameter 2cm) and test the dry silicon content M1 on the surface. Attach a protective film (circular diameter 2cm) to the surface of the copper foil and place it in a 200℃ oven for 6 hours. After cooling, remove the protective film and test the dry silicon content M2 on the surface of the copper foil. Calculate the silicon precipitation rate = (M2-M1)×100%.

[0036] 2. Refer to GB / T 2792-2014 to test peel strength, including: peel strength against steel plate at room temperature, peel strength against copper foil at room temperature, and peel strength against copper foil after aging (temperature 85℃, humidity 85%, 3 days, 7 days, 15 days).

[0037] 3. Refer to GB / T 14216-2008 to test the dyne value of copper foil aging (temperature 85℃, humidity 85%, 3 days, 7 days, 15 days).

[0038] Table 1 Test results of Examples 1-4 Silicon precipitation rate 0.5 0.4 0.3 0.8 Peel force of steel plate at room temperature (gf) 8.4 9.1 7.7 7.1 Copper foil peel strength at room temperature (gf) 7.5 7.9 6.9 6.3 Copper foil peel strength 85 / 3 days (gf) 10.5 17.1 14.5 12.0 Copper foil peel strength 85 / 7 days (gf) 11.0 19.2 15.4 13.1 Copper foil peel strength 85 / 15 days (gf) 11.1 19.6 15.9 15.5 Dyne value 85 / 3 days (dyn) 30 30 30 30 Dyne value 85 / 7 days (dyn) 30 30 30 28 Dyne value 85 / 15 days (dyn) 30 30 32 28 Table 2 Test results of Comparative Examples 1-6 Silicon precipitation rate 8.3 9.1 6.5 12.0 3.2 4.0 Peel force of steel plate at room temperature (gf) 2.6 (Residual Adhesive) 1.3 (Residual Adhesive) 5.7 (Residual Adhesive) 6.3 13.8 15.1 Copper foil peel strength at room temperature (gf) 3.4 1.7 6.1 6.4 13.2 14.8 Copper foil peel strength 85 / 3 days (gf) 18.7 23.4 15.3 5.7 21.3 22.7 Copper foil peel strength 85 / 7 days (gf) 34.6 41.2 27.4 4.9 29.1 31.4 Copper foil peel strength 85 / 15 days (gf) 53.2 62.8 43.5 4.1 36.8 39.3 Dyne value 85 / 3 days (dyn) 28 26 30 28 30 30 Dyne value 85 / 7 days (dyn) 24 22 26 24 28 28 Dyne value 85 / 15 days (dyn) 20 18 22 20 24 26 As shown in Table 1, Examples 1 to 4 achieved excellent low precipitation performance through the composite reinforcement of fumed silica with hexamethyldisilazane surface treatment and octavinyl POSS, the crosslinking of hydrogen-containing MQ resin and side-chain hydrogen-containing silicone oil, and the synergistic effect of low-cyclic raw rubber. Under extreme aging conditions, the silicon precipitation rate was extremely low, the dyne value of the copper foil surface remained good, and the peel force increased slightly within a moderate range, indicating that the adhesive layer was fully crosslinked, with very few free substances and no contamination to the copper foil.

[0039] As shown in Table 2, Comparative Example 1 (without POSS) had a peel strength of only 3.4 gf at room temperature and left adhesive residue. After 15 days of aging with double 85, the peel strength soared to 53.2 gf, and the silicon precipitation rate was 8.3%. Comparative Example 2 (without treated silica) had a semi-flowing adhesive layer, a peel strength of only 1.7 gf, and severe adhesive residue. After aging, the peel strength soared to 62.8 gf (the worst), and the silicon precipitation rate was 9.1%. This indicates that octavinyl POSS and surface-treated fumed silica are both key to ensuring the performance of the protective film. In Comparative Example 3 (untreated silica), the surface silanol groups poisoned the catalyst and consumed Si-H, hindering curing and causing the peel strength to climb to 43.5 gf. Comparative Example 4 (high-cyclic raw rubber, D3~D10=2.5wt%) showed a high silica precipitation rate of 12.0% (the highest). Cyclosiloxane molecules continuously migrated to the copper surface, forming a weak boundary layer, resulting in an abnormally low peel strength of 4.1 gf and a dyne value of 20. This indicates that low-cyclic raw rubber is the primary guarantee for achieving low precipitation. Comparative Examples 5 and 6 (removed side-chain hydrogen-containing silicone oil, fully MQ crosslinked), although stoichiometric, lacked linear flexible bridging chains, resulting in an uneven crosslinking network and initially high peel strength, which climbed to 36.8 gf ~ 39.3 gf after aging. This demonstrates that the combination of side-chain hydrogen-containing silicone oil and hydrogen-containing MQ resin is key to constructing a uniform network and achieving low and stable peel strength.

[0040] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A low-deposition silicone protective film for copper foil, characterized in that, It comprises a double-resistant PET substrate layer, a low-exudation silicone layer, and a release layer, which are stacked sequentially. The low-exudation silicone layer is formed by coating and curing silicone pressure-sensitive adhesive, which consists of the following raw material components in parts by weight: 35 to 45 parts of methyl vinyl silicone rubber; 15 to 25 parts of vinyl polysiloxane; 25 to 35 parts of methyl hydrogen-containing MQ silicone resin; 0.5 to 2.5 parts of hydrogen-containing polymethylhydrosiloxane with side chain; 8 to 18 parts of low-precipitation additive; Platinum catalyst 0.3 to 0.6 parts; Inhibitor 0.08 to 0.12 parts; The solvent makes the solid content of the silicone pressure-sensitive adhesive 28%~32%; The low-precipitation additives include fumed silica surface-treated with hexamethyldisilazane and vinyl-containing cage-like silsesquioxanes.

2. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The low-precipitation additive comprises 6 to 12 parts of fumed silica surface-treated with hexamethyldisilazane, and 2 to 4 parts of vinyl-containing cage-type silsesquioxane.

3. The low-deposition silicone protective film for copper foil as described in claim 2, characterized in that, The specific surface area of ​​the fumed silica is 200±30m² / g; the vinyl-containing cage-like silsesquioxane is an octavinyl cage-like silsesquioxane.

4. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The methyl vinyl silicone rubber has a molecular weight of 50W~120W, a vinyl molar fraction of 0.1%~1.2%, and a total D3~D10 cyclosiloxane content ≤1wt%.

5. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The vinyl polysiloxane is a vinyl-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s to 5000 mPa·s and a vinyl molar fraction of 0.2% to 0.5%.

6. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The methyl hydrogen-containing MQ silicone resin has an M / Q ratio of 0.6 to 0.85 and an active hydrogen content of 0.02 wt% to 0.05 wt%.

7. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The side-chain hydrogen-containing polymethylhydrosiloxane has a viscosity of 20 mPa·s to 100 mPa·s and an active hydrogen content of 0.3 wt% to 0.8 wt%.

8. The low-deposition silicone protective film for copper foil as described in claim 1, characterized in that, The inhibitor is 1-ethynyl-1-cyclohexanol; the platinum catalyst is a caster catalyst with a platinum content of 3000ppm~5000ppm; the solvent includes at least one of toluene, xylene and ethyl acetate.

9. A method for preparing a low-deposition silica gel protective film for copper foil as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Methyl vinyl silicone rubber was dissolved in a portion of the solvent to obtain the first mixture; Vinyl polysiloxane, methyl hydrogen MQ silicone resin, low precipitation additive and remaining solvent are mixed, dispersed and ground to a fineness ≤10μm to obtain a second mixture; Combine the first mixture and the second mixture, add the inhibitor, stir evenly, add the side-chain hydrogen-containing polymethylhydrosiloxane and platinum catalyst, mix evenly and degas under vacuum to obtain silicone pressure-sensitive adhesive; The silicone pressure-sensitive adhesive is coated onto the surface of the double-resistant PET substrate layer, cured through multiple drying tunnels, and then a release layer is attached. After curing at 40℃~55℃ for 24h~48h, a low-exudation silicone protective film for copper foil is obtained.

10. The application of a low-deposition silica gel protective film for copper foil as described in any one of claims 1 to 8 in the preparation of a negative electrode current collector for lithium-ion batteries.