Composite aluminum current collector with high binding force and preparation method thereof

Abstract

The invention discloses a composite aluminum current collector with high binding force and a preparation method thereof, and relates to the technical field of composite current collectors. The aluminum oxide of different crystal forms is subjected to magnetron sputtering on the base film to serve as the base layer, the crystal form particle size of the base layer is reduced, the compactness and the specific surface area of the base layer are improved, and therefore the binding force between the base layer and an evaporation aluminum plating layer is improved, the aluminum oxide crystal form with the smaller density serves as the base layer, the overall weight of the current collector is reduced, and the service life of the current collector is prolonged. Therefore, the energy density and the reliability of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite current collectors, in particular to a composite aluminum current collector with high bonding strength and a preparation method thereof. Background Art

[0002] The composite current collector is a new type of current collector material that is a composite of polymer materials and metals. It mainly collects current and carries the positive and negative active materials. The composite current collector structure is similar to a "sandwich" structure, with a base film (polymer materials such as PP, PET, PI, etc.) in the middle and two outer layers of copper or aluminum metal films. The thickness of the metal layer is generally required to be around 1μm. At the same time, the composite current collector has the advantages of high safety, long life, low cost, and high specific energy. Before aluminum plating, the composite aluminum will be coated with a layer of aluminum oxide as a base layer. This base layer plays an important role as a transition layer between the coating and the base film. Generally speaking, there are two types of arrangements of aluminum oxide crystal structures. One is that the oxygen atoms are arranged in a hexagonal stacking, and the other is arranged in a cubic stacking. Different arrangements bring different properties.

[0003] The alumina currently used in composite aluminum base layers is hexagonally stacked, also known as α-Al2O3. While this base layer offers acceptable corrosion resistance and mechanical properties, its adhesion to the base film is limited and degrades in electrolyte environments. Furthermore, compared to other alumina crystal arrangements, such as γ-Al2O3, it has a higher density and larger crystal grain size, resulting in a smaller specific surface area and, consequently, less aluminum adhesion.

[0004] Therefore, the present invention proposes a composite aluminum current collector with high bonding strength and a preparation method thereof, by using alumina with other crystal arrangements as a base layer, or forming a mixed base layer with the original α-Al2O3, combining the advantages of different crystal forms of alumina, and further improving the properties of the base layer. Summary of the Invention

[0005] The object of the present invention is to provide a composite aluminum current collector with high bonding strength and a preparation method thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film and use an aluminum target to perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, and then evaporate aluminum, roll and cut to obtain a composite aluminum current collector.

[0007] Furthermore, in step 1, the thickness of the PET film is 4 μm; In step 1, the thickness of the sputtered aluminum layer is 0.1 nm to 1 nm.

[0008] Furthermore, in step 1, the process conditions of the magnetron sputtering are: sputtering power density 30W / cm 2 ~50W / cm 2 , vacuum degree 4×10 -4 Pa~5×10 -4 Pa.

[0009] Furthermore, in step 1, the aluminum target is one of a γ-Al2O3 target, an η-Al2O3 target, a θ-Al2O3 target, and a mixed target; The mixed target is a mixture of an α-Al2O3 target and a γ-Al2O3 target, a mixture of an α-Al2O3 target and an η-Al2O3 target, or a mixture of an α-Al2O3 target and a θ-Al2O3 target; In the mixed target material, when the α-Al2O3 target material and the γ-Al2O3 target material are mixed, the quantity ratio of the α-Al2O3 target material to the γ-Al2O3 target material is (1-3):1; When the α-Al2O3 target and the η-Al2O3 target are mixed, the quantity ratio of the α-Al2O3 target to the η-Al2O3 target is (1~3):1; When the α-Al2O3 target and the θ-Al2O3 target are mixed, the quantity ratio of the α-Al2O3 target to the θ-Al2O3 target is (1~3):1.

[0010] Furthermore, the sizes of the above-mentioned α-Al2O3 target, γ-Al2O3 target, η-Al2O3 target and θ-Al2O3 target are all the same.

[0011] Furthermore, in step 1, the gas flow rate of argon is 30 mL / min to 50 mL / min.

[0012] Furthermore, in step 2, the process conditions for the winding are: the tension value at the unwinding end is 80N~120N, and the tension value at the winding end is 60N~100N.

[0013] Furthermore, in step 2, the process conditions of the evaporation aluminum plating are: temperature 1000° C.~1200° C., wire feeding speed 60 mm / min~80 mm / min, and PET film transmission speed 280 m / min~300 m / min.

[0014] Furthermore, the γ-Al2O3 target is obtained by dehydrating aluminum hydroxide at a dehydration temperature of 140°C to 150°C; The η-Al2O3 target is obtained by calcining Bayerite at a calcination temperature of 400°C to 750°C; The θ-Al2O3 target material is obtained by pyrolysis of aluminum hydroxide at a pyrolysis temperature of 700°C to 1200°C.

[0015] In the above technical solution, the present invention magnetically controls aluminum oxide of different crystal forms on the base film as a base layer, reduces the size of the crystal particles of the base layer, improves the density and specific surface area of ​​the base layer, and thus improves the bonding strength between the base layer and the evaporated aluminum layer; and also uses aluminum oxide crystal form with lower density as the base layer, which reduces the overall weight of the current collector, thereby improving the energy density and battery reliability of the battery.

[0016] Furthermore, the PET film is first subjected to plasma treatment with a mixed gas before magnetron sputtering the aluminum target, and then coated with a composite coating; The coating thickness of the composite coating is 1 μm to 3 μm; The mixed gas is a mixture of argon and oxygen, and the gas flow ratio of argon to oxygen is (0.5~1.5): (2.5~6.5).

[0017] The process conditions of the plasma treatment are: mixed gas flow rate 100 sccm~300 sccm, treatment power 100 W~300 W, and treatment time 2 min~6 min.

[0018] Furthermore, the composite coating is prepared by the following process: S1: Mixing modified polyisobutylene, an amine curing agent, and toluene, heating and stirring to react, to obtain product A; S2: Mix product A, hyperbranched alkynyl-containing polyimide solution, pentaerythritol tetramercaptoacetate, toluene and triethylamine, stir evenly, heat to react, and keep the temperature for 15 to 25 hours after the reaction is completed to obtain a composite coating.

[0019] Furthermore, in S1, the mass ratio of the modified polyisobutylene, the amine curing agent and toluene is 1:(0.01-0.05):(2-3).

[0020] Furthermore, in S1, the process conditions of the heating and stirring reaction are: heating temperature 65°C~85°C, heating time 30min~60min, and stirring speed 100r / min~500r / min.

[0021] Furthermore, in S2, the mass ratio of the product A, the hyperbranched alkyne-containing polyimide solution, pentaerythritol tetrathioglycolate, toluene and triethylamine is 10: (5-10): (3-5): (40-60): (0.05-0.1).

[0022] Furthermore, in S2, the process conditions of the heating reaction are: heating temperature 45°C~65°C, heating time 10min~30min.

[0023] Furthermore, in S1, the amine curing agent is a mixture of one or more of diethylenetriamine, isophoronediamine, diethylenetriamine, cyclohexylamine, m-phenylenediamine, and 4,4'-diaminodiphenylmethane.

[0024] Furthermore, in S1, the preparation process of the modified polyisobutylene is as follows: The polyisobutylene and perbenzoic acid are mixed and heated for reaction. After the reaction is completed, the mixture is allowed to stand for separation, the oil layer is washed, the pH is adjusted to 7.0, and the mixture is distilled under reduced pressure to obtain modified polyisobutylene.

[0025] Furthermore, the molar ratio of polyisobutylene to peroxybenzoic acid is 1:(0.5~1.5).

[0026] Furthermore, the process conditions of the heating reaction are: heating temperature 40°C~60°C, reaction time 6h~12h.

[0027] Furthermore, the process conditions of the reduced pressure distillation are: vacuum degree 5Kpa~15Kpa, and distillation time 10min~20min.

[0028] Furthermore, in S1, the hyperbranched alkyne-containing polyimide solution is prepared by the following process: Step A: diethylenetriamine, concentrated hydrochloric acid and propargyl formaldehyde are mixed, and under a nitrogen atmosphere, the pH is adjusted to neutral, the mixture is heated for reaction, and filtered to obtain modified diethylenetriamine; Step B: mixing modified diethylenetriamine, pyromellitic dianhydride and methanol, stirring to dissolve, and heating to react to obtain a hyperbranched alkynyl-containing polyimide acid solution; Step C: mixing the hyperbranched alkynyl-containing polyimide acid solution with pyridine, and heating the mixture for reaction to obtain a hyperbranched alkynyl-containing polyimide solution.

[0029] Furthermore, in step A, the molar ratio of diethylenetriamine to propargyl formaldehyde is (2-6):1; The mass ratio of propargyl formaldehyde to hydrochloric acid is 10:(0.05~0.1).

[0030] Furthermore, in step A, the process conditions of the heating reaction are: reaction temperature 120° C. to 160° C., and reaction time 6 h to 10 h.

[0031] Furthermore, in step B, the molar ratio of modified diethylenetriamine to pyromellitic dianhydride is 1:(0.9-1.6); The mass ratio of modified diethylenetriamine to methanol is 1:(3~8).

[0032] Furthermore, in step B, the process conditions of the heating reaction are: reaction temperature 40°C~80°C, reaction time 2h~10h.

[0033] Furthermore, in step C, the mass ratio of the hyperbranched alkynyl-containing polyimide acid solution to pyridine is 1:(0.2-0.8).

[0034] Furthermore, in step C, the process conditions of the heating reaction are: reaction temperature 100° C. to 300° C., and reaction time 2 h to 6 h.

[0035] In the above technical solution, polyisobutylene has excellent flexibility and chemical stability, but lacks reactive groups. Therefore, polyisobutylene is epoxidized to introduce epoxy groups. Then, by introducing alkynyl groups into diethylenetriamine, it is copolymerized with pyromellitic dianhydride to prepare an alkynyl-containing hyperbranched polyimide solution. The two are mixed with pentaerythritol tetramercaptoacetate to prepare a composite coating. Pentaerythritol tetramercaptoacetate can undergo a thiol-alkyne click reaction with the alkynyl-containing hyperbranched polyimide solution at room temperature. It can also undergo a ring-opening reaction with the epoxy groups of polyisobutylene under the action of triethylamine, resulting in cross-linking and forming a network structure. This enhances the bonding strength of the components in the coating system, thereby improving the peel strength of the coating. In addition, the epoxy group has strong polarity and can form chemical bonds with metallic aluminum, thereby enhancing the bonding strength between the PET film and the sputtered aluminum layer. The hyperbranched polyimide containing alkynyl groups has good thermal stability and a small thermal shrinkage rate. On the one hand, this is because the branched structure restricts the movement of the chain segments. On the other hand, the introduction of alkynyl groups increases the cross-linking density between molecules. The alkynyl groups can self-cross-link at high temperatures to form a three-dimensional network structure, which restricts the movement of the chain segments, reduces the thermal shrinkage rate, reduces the thermal creep caused by high temperature during the evaporation aluminum plating process, and extends the service life of the composite aluminum current collector.

[0036] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses alumina of different crystal forms as a base layer on the base film to reduce the size of the base layer crystal particles, improve the density and specific surface area of ​​the base layer, and thus improve the bonding strength between the base layer and the evaporated aluminum coating.

[0037] 2. The present invention reduces the overall weight of the current collector by using alumina crystals with lower density as a base layer, thereby improving the energy density and reliability of the battery.

[0038] 3. By epoxidizing polyisobutylene, alkynyl groups are introduced into diethylenetriamine, and the mixture is copolymerized with pyromellitic dianhydride to prepare an alkynyl-containing hyperbranched polyimide solution. Pentaerythritol tetramercaptoacetate and triethylamine are then added to allow the pentaerythritol tetramercaptoacetate and the alkynyl-containing hyperbranched polyimide solution to undergo a thiol-alkyne click reaction at room temperature. The pentaerythritol tetramercaptoacetate and the alkynyl-containing hyperbranched polyimide solution then undergo a ring-opening reaction with the epoxy groups of polyisobutylene under the action of triethylamine, resulting in cross-linking and forming a network structure. This enhances the binding force of the components in the coating system, thereby improving the peel strength of the coating.

[0039] 4. The epoxy group has strong polarity and can form a chemical bond with metallic aluminum, thereby enhancing the bonding strength between the PET film and the sputtered aluminum layer. The hyperbranched polyimide containing alkynyl groups has good thermal stability and a small thermal shrinkage rate, which reduces the thermal creep caused by high temperature during the evaporation aluminum plating process and extends the service life of the composite aluminum current collector. DETAILED DESCRIPTION

[0040] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0041] In the following specific embodiments, α-Al2O3, γ-Al2O3, η-Al2O3 and θ-Al2O3 targets all have a purity of 99.95%. The amine curing agent is m-phenylenediamine; PET film, thickness 4 μm; Example 1: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film and use 20 γ-Al2O3 targets to perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0042] Example 2: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film and use 20 η-Al2O3 targets to perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0043] Example 3: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film and use 20 θ-Al2O3 targets to perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0044] Example 4: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 10 α-Al2O3 targets and 10 γ-Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0045] Example 5: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 γ-Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0046] Example 6: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 15 α-Al2O3 targets and 5 γ-Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0047] Example 7: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 η--Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0048] Example 8: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 θ--Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0049] Example 9: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 γ-Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 0.5nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 40W / cm 2 , vacuum degree 4.5×10 -4 Pa; in step 1, the gas flow rate of argon is 40 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 100 N, and the tension value at the winding end is 80 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1100 ° C, wire feeding speed 70 mm / min, and PET film transmission speed 290 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 145 ° C.

[0050] Example 10: A method for preparing a composite aluminum current collector with high bonding strength, comprising the following steps: Step 1: Take a PET film, 14 α-Al2O3 targets and 7 γ-Al2O3 targets, and perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 - 3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the thickness of the sputtered aluminum layer is 0.1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 30W / cm 2 , vacuum degree 4×10 -4Pa; in step 1, the gas flow rate of argon is 30 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 80 N, and the tension value at the winding end is 60 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1000 ° C, wire feeding speed 60 mm / min, and PET film transmission speed 280 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 140 ° C.

[0051] Example 11: A method for preparing a composite aluminum current collector with high bonding strength, wherein the PET film is first subjected to plasma treatment with a mixed gas before magnetron sputtering an aluminum target, and then coated with a composite coating, specifically comprising the following steps: (1) Preparation of composite coating: The modified polyisobutylene was obtained by mixing polyisobutylene and peroxybenzoic acid in a molar ratio of 1:1.5, heating to 60°C for 12 hours, and then standing to separate the layers. The oil layer was washed, the pH was adjusted to 7.0, and the mixture was subjected to vacuum distillation to obtain the modified polyisobutylene. The process conditions of the vacuum distillation were: vacuum degree 15KPa, and distillation time 20 minutes. Step A: diethylenetriamine, concentrated hydrochloric acid and propargyl formaldehyde are mixed, and under nitrogen atmosphere, the pH is adjusted to neutral, heated to 160° C. for reaction for 10 hours, and filtered to obtain modified diethylenetriamine; Step B: modified diethylenetriamine, pyromellitic dianhydride and methanol are mixed, stirred and dissolved, heated to 80° C. for reaction for 10 hours to obtain a hyperbranched alkynyl-containing polyimide acid solution; Step C: the hyperbranched alkynyl-containing polyimide acid solution is mixed with pyridine in a mass ratio of 1:0.8, heated to 300° C. for reaction for 6 hours to obtain a hyperbranched alkynyl-containing polyimide solution; in Step A, the molar ratio of diethylenetriamine and propargyl formaldehyde is 6:1; the mass ratio of propargyl formaldehyde to hydrochloric acid is 10:0.1; in Step B, the molar ratio of modified diethylenetriamine and pyromellitic dianhydride is 1:1.6; the mass ratio of modified diethylenetriamine to methanol is 1:8; S1: Modified polyisobutylene, m-phenylenediamine and toluene are mixed in a mass ratio of 1:0.05:3, heated and stirred to react, and product A is obtained; S2: Product A, hyperbranched alkynyl-containing polyimide solution, pentaerythritol tetramercaptoacetate, toluene and triethylamine are mixed in a mass ratio of 10:10:5:60:0.1, stirred evenly, heated to 65°C for reaction for 30 minutes, and kept warm for 25 hours after the reaction is completed to obtain a composite coating; the process conditions for the heating and stirring reaction are: heating temperature 85°C, heating time 60 minutes, and stirring speed 500 r / min; (2) Preparation of composite aluminum current collector: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 θ--Al2O3 targets, pass a mixed gas for plasma treatment, apply a 3 μm thick composite coating, cure at 250 ° C, and perform magnetron sputtering under argon atmosphere protection to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate to 5×10 -3 Pa, and then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the mixed gas is a mixture of argon and oxygen, and the gas flow ratio of argon to oxygen is 1.5:6.5; the process conditions of plasma treatment are: mixed gas flow rate 300sccm, processing power 300W, and processing time 6min; in step 1, the thickness of the sputtered aluminum layer is 1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 50W / cm 2 , vacuum degree 5×10 -4 Pa; in step 1, the gas flow rate of argon is 50 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 120 N, and the tension value at the winding end is 100 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1200 ° C, wire feeding speed 80 mm / min, and PET film transmission speed 300 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 150 ° C.

[0052] Example 12: A method for preparing a composite aluminum current collector with high bonding strength, wherein the PET film is first subjected to plasma treatment with a mixed gas before magnetron sputtering an aluminum target, and then coated with a composite coating, specifically comprising the following steps: (1) Preparation of composite coating: The modified polyisobutylene was obtained by mixing polyisobutylene and peroxybenzoic acid in a molar ratio of 1:1, heating to 50°C for 9 hours, and then standing to separate the layers after the reaction. The oil layer was washed, the pH was adjusted to 7.0, and the mixture was subjected to vacuum distillation to obtain the modified polyisobutylene. The process conditions of the vacuum distillation were: vacuum degree 10KPa, and distillation time 15 minutes. Step A: diethylenetriamine, concentrated hydrochloric acid and propargyl formaldehyde are mixed, and under nitrogen atmosphere, the pH is adjusted to neutral, heated to 140°C for reaction for 8 hours, and filtered to obtain modified diethylenetriamine; Step B: modified diethylenetriamine, pyromellitic dianhydride and methanol are mixed, stirred and dissolved, heated to 60°C for reaction for 6 hours to obtain a hyperbranched alkynyl-containing polyimide acid solution; Step C: the hyperbranched alkynyl-containing polyimide acid solution is mixed with pyridine in a mass ratio of 1:0.6, heated to 200°C for reaction for 4 hours to obtain a hyperbranched alkynyl-containing polyimide solution; in Step A, the molar ratio of diethylenetriamine and propargyl formaldehyde is 4:1; the mass ratio of propargyl formaldehyde to hydrochloric acid is 10:0.08; in Step B, the molar ratio of modified diethylenetriamine and pyromellitic dianhydride is 1:1.3; the mass ratio of modified diethylenetriamine to methanol is 1:5; S1: Modified polyisobutylene, m-phenylenediamine and toluene are mixed in a mass ratio of 1:0.03:2.5, heated and stirred to react, and product A is obtained; S2: Product A, hyperbranched alkynyl-containing polyimide solution, pentaerythritol tetramercaptoacetate, toluene and triethylamine are mixed in a mass ratio of 10:7:4:50:0.08, stirred evenly, heated to 55°C for reaction for 20 minutes, and kept warm for 20 hours after the reaction is completed to obtain a composite coating; the process conditions for the heating and stirring reaction are: heating temperature 75°C, heating time 45 minutes, and stirring speed 300 r / min; (2) Preparation of composite aluminum current collector: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 θ-Al2O3 targets, pass a mixed gas for plasma treatment, apply a 2 μm thick composite coating, cure at 200 ° C, and perform magnetron sputtering under argon atmosphere protection to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the mixed gas is a mixture of argon and oxygen, and the gas flow ratio of argon to oxygen is 1.0:4.5; the process conditions of plasma treatment are: mixed gas flow rate 200sccm, processing power 200W, and processing time 4min; in step 1, the thickness of the sputtered aluminum layer is 0.5nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 40W / cm 2 , vacuum degree 4.5×10 -4Pa; in step 1, the gas flow rate of argon is 40 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 100 N, and the tension value at the winding end is 80 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1100 ° C, wire feeding speed 70 mm / min, and PET film transmission speed 290 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 145 ° C.

[0053] Example 13: A method for preparing a composite aluminum current collector with high bonding strength, wherein the PET film is first subjected to plasma treatment with a mixed gas before magnetron sputtering an aluminum target, and then coated with a composite coating, specifically comprising the following steps: (1) Preparation of composite coating: The modified polyisobutylene was obtained by mixing polyisobutylene and peroxybenzoic acid in a molar ratio of 1:0.5, heating to 40°C for 6 hours, and then standing to separate the layers after the reaction. The oil layer was washed, the pH was adjusted to 7.0, and the mixture was subjected to vacuum distillation to obtain the modified polyisobutylene. The process conditions of the vacuum distillation were: vacuum degree 5 KPa, and distillation time 10 minutes. Step A: diethylenetriamine, concentrated hydrochloric acid and propargyl formaldehyde are mixed, and under nitrogen atmosphere, the pH is adjusted to neutral, heated to 120°C for reaction for 6 hours, and filtered to obtain modified diethylenetriamine; Step B: modified diethylenetriamine, pyromellitic dianhydride and methanol are mixed, stirred and dissolved, heated to 40°C for reaction for 2 hours to obtain a hyperbranched alkynyl-containing polyimide acid solution; Step C: the hyperbranched alkynyl-containing polyimide acid solution is mixed with pyridine in a mass ratio of 1:0.2, heated to 100°C for reaction for 2 hours to obtain a hyperbranched alkynyl-containing polyimide solution; in Step A, the molar ratio of diethylenetriamine and propargyl formaldehyde is 2:1; the mass ratio of propargyl formaldehyde to hydrochloric acid is 10:0.1; in Step B, the molar ratio of modified diethylenetriamine and pyromellitic dianhydride is 1:0.9; and the mass ratio of modified diethylenetriamine to methanol is 1:3; S1: Modified polyisobutylene, m-phenylenediamine and toluene are mixed in a mass ratio of 1:0.01:2, heated and stirred to react, and product A is obtained; S2: Product A, hyperbranched alkynyl-containing polyimide solution, pentaerythritol tetramercaptoacetate, toluene and triethylamine are mixed in a mass ratio of 10:5:3:40:0.05, stirred evenly, heated to 45°C for reaction for 10 minutes, and kept warm for 15 hours after the reaction is completed to obtain a composite coating; the process conditions for the heating and stirring reaction are: heating temperature 65°C, heating time 30 minutes, and stirring speed 100 r / min; (2) Preparation of composite aluminum current collector: Step 1: Take a PET film, use 14 α-Al2O3 targets and 7 θ--Al2O3 targets, pass a mixed gas for plasma treatment, apply a 1 μm thick composite coating, cure at 150 ° C, and perform magnetron sputtering under argon atmosphere protection to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, then evaporate aluminum, roll and cut to obtain a composite aluminum current collector; in step 1, the mixed gas is a mixture of argon and oxygen, and the gas flow ratio of argon to oxygen is 0.5:2.5; the process conditions of plasma treatment are: mixed gas flow rate 100sccm, processing power 100W, and processing time 2min; in step 1, the thickness of the sputtered aluminum layer is 0.1nm; in step 1, the process conditions of magnetron sputtering are: sputtering power density 30W / cm 2 , vacuum degree 4×10 -4 Pa; in step 1, the gas flow rate of argon is 30 mL / min; in step 2, the winding process conditions are: the tension value at the unwinding end is 80 N, and the tension value at the winding end is 60 N; in step 2, the process conditions for evaporation aluminum plating are: temperature 1000 ° C, wire feeding speed 60 mm / min, and PET film transmission speed 280 m / min; the γ-Al2O3 target material is obtained by dehydrating aluminum hydroxide, and the dehydration temperature is 140 ° C.

[0054] Comparative Example 1: Using Example 1 as a comparison, the γ-Al2O3 target was replaced with an α-Al2O3 target for magnetron sputtering, and the other conditions remained unchanged.

[0055] Comparative Example 2: Using Example 9 as a comparison, the modified polyisobutylene was not added to the composite coating, and the other conditions remained unchanged.

[0056] Comparative Example 3: Using Example 9 as a comparison, the hyperbranched alkynyl-containing polyimide solution was not added to the composite coating, and other conditions remained unchanged.

[0057] Experiment: The composite aluminum current collectors obtained in the examples and comparative examples were tested for various properties, as follows: Peel strength test: Cut the composite aluminum current collector into 15mm x 100mm samples. Attach 3M-9080A-15mm tape to a stainless steel plate. Evenly place the sample on the tape and squeeze it back and forth twice using a 2kg standard small roller. Then, attach 3M-9080A-14mm tape to the sample surface and squeeze it back and forth twice using a 2kg standard small roller. Place the pressed sample on a tensile testing machine and stretch it 180° at a speed of 100mm / min and a width of 15mm. Surface density test: Cut the composite aluminum current collector into discs with a radius of 3 cm, weigh the mass three times, and take the average value. Surface density = mass / area; The following table shows the performance test results of the composite aluminum current collector;

[0058] Based on the data in the above table, we can draw the following conclusions: From Examples 1 to 8 and Comparative Example 1, it can be seen that adding alumina of other crystal forms on the basis of α-Al2O3 can improve the bonding strength between the target and the base film, and when the mass ratio of α-Al2O3 target to γ-Al2O3 target is 2:1, the bonding strength is the best. It can be seen that adding alumina of different crystal forms can improve the properties of the base film; As can be seen from Example 6, as the proportion of the γ-Al2O3 target increases, the base layer at the same thickness is lighter and has a lower surface density. When the composite aluminum current collector is applied to the battery, the mass energy density of the battery is also improved. From Examples 11 to 13, it can be seen that after the PET film treated with plasma is coated with the composite coating, the bonding strength with the sputtered aluminum layer is enhanced; In summary, it can be seen that the setting of the materials used for the base layer and composite coating in this application can promote the improvement of the peeling strength of the composite aluminum current collector, while reducing the surface density of the composite aluminum current collector and improving the mass energy density of the battery.

[0059] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for preparing a composite aluminum current collector with high bonding strength, characterized in that: The following steps are involved: Step 1: Take a PET film and use an aluminum target to perform magnetron sputtering under argon atmosphere to obtain a PET film containing a sputtered aluminum layer; Step 2: Wind the PET film containing the sputtered aluminum layer and evacuate it to 5×10 -3 Pa, and then evaporate aluminum, roll and slit to obtain a composite aluminum current collector; In step 1, the aluminum target is one of a γ-Al2O3 target, an η-Al2O3 target, a θ-Al2O3 target, and a mixed target; The mixed target material is a mixture of an α-Al2O3 target material and a γ-Al2O3 target material, a mixture of an α-Al2O3 target material and an η-Al2O3 target material, or a mixture of an α-Al2O3 target material and a θ-Al2O3 target material.

2. The method for preparing a composite aluminum current collector with high bonding strength according to claim 1, wherein: In step 1, the thickness of the PET film is 4 μm.

3. The method for preparing a composite aluminum current collector with high bonding strength according to claim 2, wherein: In step 1, the thickness of the sputtered aluminum layer is 0.1 nm to 1 nm.

4. The method for preparing a composite aluminum current collector with high bonding strength according to claim 3, wherein: In step 1, the process conditions of the magnetron sputtering are: sputtering power density 30W / cm 2 ~50W / cm 2 , vacuum degree 4×10 -4 Pa~5×10 -4 Pa.

5. The method for preparing a composite aluminum current collector with high bonding strength according to claim 4, characterized in that: In step 1, the gas flow rate of argon is 30 mL / min~50 mL / min.

6. The method for preparing a composite aluminum current collector with high bonding strength according to claim 5, characterized in that: In step 2, the process conditions for the winding are: the tension value at the unwinding end is 80N~120N, and the tension value at the winding end is 60N~100N.

7. The method for preparing a composite aluminum current collector with high bonding strength according to claim 6, characterized in that: In step 2, the process conditions of the evaporation aluminum plating are: temperature 1000° C.~1200° C., wire feeding speed 60 mm / min~80 mm / min, and PET film transmission speed 280 m / min~300 m / min.

8. The method for preparing a composite aluminum current collector with high bonding strength according to claim 1, wherein: The PET film is first subjected to plasma treatment with a mixed gas before magnetron sputtering the aluminum target, and then coated with a composite coating; The composite coating is prepared by the following process: S1: Mixing modified polyisobutylene, an amine curing agent, and toluene, heating and stirring to react, to obtain product A; S2: Mix product A, hyperbranched alkynyl-containing polyimide solution, pentaerythritol tetramercaptoacetate, toluene and triethylamine, stir evenly, heat to react, and keep the temperature for 15 to 25 hours after the reaction is completed to obtain a composite coating.

9. The method for preparing a composite aluminum current collector with high bonding strength according to claim 8, wherein: In S1, the mass ratio of the modified polyisobutylene, the amine curing agent and toluene is 1: (0.01-0.05): (2-3); In S2, the mass ratio of the product A, the hyperbranched alkyne-containing polyimide solution, pentaerythritol tetrathioglycolate, toluene and triethylamine is 10: (5-10): (3-5): (40-60): (0.05-0.1).

10. A composite aluminum current collector with high bonding strength, characterized by: Obtained according to the preparation method according to any one of claims 1 to 9.

Images