High-safety distributed copper-aluminum composite current collector and preparation method thereof

Abstract

The application relates to the technical field of lithium batteries, in particular to a high-safety distributed copper-aluminum composite current collector and a preparation method thereof; in order to improve the safety performance of the prepared composite current collector, boehmite is added in a binder as inorganic filler, the thermal stability of the boehmite is utilized, and the characteristics of heat absorption and decomposition under a high-temperature environment are utilized to enhance the flame-retardant performance of the binder; and on the basis, the application also prepares a modified trihydric alcohol with a polyphenyl ring structure, and an ether bond is introduced into the modified trihydric alcohol to improve the flexibility of a molecular chain segment, the problem that the crosslinking degree of the binder is reduced due to a steric hindrance effect is avoided, meanwhile, phosphorus elements are introduced into isocyanate, the flame-retardant performance of the binder is further enhanced, and the safety performance of the finally prepared composite current collector is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a high-safety distributed copper-aluminum composite current collector and its preparation method. Background Technology

[0002] Lithium batteries have gradually become the mainstream direction of battery development in recent years due to their technological advantages such as long cycle life, high energy density, and energy saving and environmental protection; and current collectors, as an important component of lithium-ion batteries, have also gradually become a focus of attention.

[0003] Most existing lithium batteries commonly use pure copper foil for the negative electrode and pure aluminum foil for the positive electrode as current collectors. Although these metal current collectors have excellent electrical performance, their fluid ductility is limited, which undoubtedly restricts the processing and use of current collectors. Composite current collectors use polymer materials as the base film, which can greatly improve the ductility of the current collector and significantly improve its applicability. However, polymer materials are not resistant to high temperatures and have a low ignition point, which can easily lead to battery fire when the battery is heated. Therefore, it is necessary to improve this defect to better meet market demands. Summary of the Invention

[0004] The purpose of this invention is to provide a high-safety distributed copper-aluminum composite current collector and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-safety distributed copper-aluminum composite current collector, which has the following technical features: the high-safety distributed composite current collector is composed of an aluminum foil layer on the upper surface, a polymer film on the inner side and a copper foil layer on the lower surface;

[0006] The polymer film has flame-retardant adhesive layers on both sides to bond and fix the aluminum foil layer and the copper foil layer.

[0007] Furthermore, the polymer film is any one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, and polyamide film, with a thickness of 4-20 μm.

[0008] Furthermore, the aluminum foil layer is made of double-sided smooth, double-sided rough, or single-sided smooth and single-sided rough rolled aluminum foil with a thickness of 5-20 μm;

[0009] The copper foil layer is made of electrolytic copper foil or rolled copper foil, with a thickness of 2-15 μm.

[0010] Furthermore, the flame-retardant adhesive layer is prepared by coating and drying a modified flame-retardant adhesive, with a single-layer coating weight of 1-20 g / m².2 ;

[0011] The modified flame-retardant adhesive is composed of component A and component B.

[0012] The mass ratio of component A to component B is (2-4.5):1.

[0013] Furthermore, by weight, component A comprises the following components: 1-3 parts modified triol, 2-5 parts diol, 0.5-1.5 parts boehmite, and 0.05-0.2 parts silane coupling agent;

[0014] The diol is any one of polyhexanediol carbonate diol, polyethylene adipate diol, ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol; the silane coupling agent is KH-550 silane coupling agent.

[0015] Component B is prepared by reacting diphenyl aminophosphate with triphenylmethane triisocyanate.

[0016] A method for preparing a high-safety distributed copper-aluminum composite current collector includes the following steps:

[0017] S1. Prepare component A;

[0018] S11. Under a nitrogen atmosphere, tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate was dispersed in tetrahydrofuran and mixed thoroughly. Then, it was added dropwise to a mixed solution containing 4,4'-diaminodiphenyl ether. After the addition was complete, the temperature was raised to 62-65℃ and reacted for 4-8 hours. Then, the heating was stopped and the mixture was cooled to room temperature. Then, it was added dropwise to a DMF solution containing terephthalic acid and mixed thoroughly. Then, the temperature was raised to 50-60℃ and reacted for 2-4 hours. Then, it was added dropwise to diethylene glycol treated in an ice-water bath. Dibutyltin dilaurate was added, and the temperature was raised to 62-65℃. After reacting for 18-36 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0019] S12. Mix the modified triol and diol prepared in step S11, stir evenly, add boehmite, ultrasonically disperse for 15-30 min, add silane coupling agent, evacuate to the reaction pressure of 0-500 Pa, heat to 110-120℃, continue mixing and reacting for 45-80 min to obtain component A.

[0020] S2. Prepare component B;

[0021] Diphenyl aminophosphate was dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. Triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was completed, the temperature was raised to 85-95℃ and the reaction was carried out for 2-4 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0022] S3. Mix component A and component B for 2-5 minutes to obtain a modified flame-retardant adhesive. Coat both sides of the polymer film with the modified adhesive and then attach aluminum foil and copper foil layers respectively. After aging treatment, a high-safety distributed copper-aluminum composite current collector is obtained.

[0023] Furthermore, in step S11, by weight, the mass ratio of 1,2,4-tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate, 4,4'-diaminodiphenyl ether, terephthalic acid, and diethylene glycol is 1:(1.2-1.8):(1.15-1.4)(0.7-0.9).

[0024] Furthermore, the mass ratio of dibutyltin dilaurate to diethylene glycol is (0.03-0.05):(0.7-0.9).

[0025] Furthermore, in step S2, the mass ratio of DMF diphenyl aminophosphate to triphenylmethane triisocyanate is (0.62-0.72):1.

[0026] Furthermore, in step S3, when bonding the aluminum foil layer and the copper foil layer, the bonding pressure is 0.5-1.5MPa, the bonding temperature is 30-40℃, and the bonding speed is 50-200m / min; during the aging treatment, the aging temperature is 30-80℃, and the aging time is 12-30s.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0028] 1. In order to improve the safety performance of the prepared composite current collector, the present invention prepares a modified flame-retardant binder with flame-retardant function, and adds boehmite as an inorganic filler, which can form a filling skeleton in the modified flame-retardant binder, enhance the hardness of the binder, reduce the wrinkling defects of the electrode, and the boehmite also has thermal stability and will decompose and absorb heat at high temperature, reduce the temperature of the substrate, and generate a flame-retardant alumina layer, which isolates the contact between oxygen and combustibles and inhibits the combustion reaction.

[0029] 2. To further enhance the flame-retardant properties of the adhesive, this invention also limits the composition of the adhesive. First, this invention uses a mixture of 1,2,4-tris(ethylene oxide methyl) 1,2,4-phenyltricarboxylate and 4,4'-diaminodiphenyl ether to generate a three-armed compound with an amino group as the terminal group, utilizing the reaction between amino and epoxy groups. This compound is then further reacted with terephthalic acid and diethylene glycol to finally generate a three-armed compound with an alcohol hydroxyl group as the terminal group. In preparing this three-armed compound, this invention limits the raw materials and reaction conditions, introducing a large number of benzene ring structures with high-temperature stability, which can significantly improve the high-temperature resistance of the adhesive. Simultaneously, to avoid steric hindrance caused by excessive benzene ring structures affecting the subsequent curing of the adhesive, this invention also introduces ether bonds, thereby enhancing the mobility and flexibility of the molecular chain segments and improving the curing and bonding efficiency.

[0030] 3. In addition, the present invention further uses diphenyl aminophosphate and triphenylmethane triisocyanate to prepare a phosphorus-containing isocyanate compound as component B. The flame retardant properties of phosphorus are utilized to further enhance the flame retardant properties of the binder. After mixing components A and B, a binder with high adhesion is generated. The current collector is then subjected to composite aging treatment to finally obtain a high-safety distributed copper-aluminum composite current collector. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] There are no special restrictions on the suppliers of any of the raw materials involved in this invention. Exemplary examples include: 1,2,4-tris(ethylene oxide methyl) 1,2,4-phenyltricarboxylate, CAS No. 7237-83-4, which can be purchased from Shaanxi Didu New Materials Co., Ltd.; 4,4'-diaminodiphenyl ether, CAS No. 101-80-4, which can be purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; boehmite, CAS No. 1318-23-6, with a particle size of 0.9-1 micrometer, which can be purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; diphenyl aminophosphate, CAS No. 7450-69-3, which can be purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; triphenylmethane triisocyanate, CAS No. 2422-91-5, which can be purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; biaxially oriented polypropylene film, which can be provided by Dongguan Shengsi Electronics Co., Ltd.; aluminum foil with a purity of ≥99.5%; and copper foil with a purity of ≥99.5%.

[0033] Example 1. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0034] S1. Prepare component A;

[0035] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.2 parts of 4,4'-diaminodiphenyl ether.

[0036] After the addition was complete, the temperature was raised to 62°C and reacted for 4 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.15 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 50°C and reacted for 2 hours. The mixture was then added dropwise to 0.7 parts of diethylene glycol treated in an ice-water bath. 0.03 parts of dibutyltin dilaurate were added, and the temperature was raised to 62°C. After reacting for 18 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0037] S12. By weight, mix 1 part of the modified triol prepared in step S11 with 2 parts of 1,4-butanediol, stir evenly, add 0.5 parts of boehmite, ultrasonically disperse for 15 min, add 0.05 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 110 °C, and continue mixing and reacting for 45 min to obtain component A;

[0038] S2. Prepare component B;

[0039] Under a nitrogen atmosphere, 0.62 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 85°C and the reaction was carried out for 2 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0040] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0041] Example 2. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0042] Compared with Example 1, this example increases the amount of 4,4'-diaminodiphenyl ether added in step S11;

[0043] S1. Prepare component A;

[0044] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.8 parts of 4,4'-diaminodiphenyl ether.

[0045] After the addition was complete, the temperature was raised to 62°C and reacted for 4 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.15 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 50°C and reacted for 2 hours. The mixture was then added dropwise to 0.7 parts of diethylene glycol treated in an ice-water bath. 0.03 parts of dibutyltin dilaurate were added, and the temperature was raised to 62°C. After reacting for 18 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0046] S12. By weight, mix 1 part of the modified triol prepared in step S11 with 2 parts of 1,4-butanediol, stir evenly, add 0.5 parts of boehmite, ultrasonically disperse for 15 min, add 0.05 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 110 °C, and continue mixing and reacting for 45 min to obtain component A;

[0047] S2. Prepare component B;

[0048] Under a nitrogen atmosphere, 0.62 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 85°C and the reaction was carried out for 2 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0049] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0050] Example 3. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0051] Compared with Example 1, this example increases the amount of diethylene glycol added in step S11;

[0052] S1. Prepare component A;

[0053] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.2 parts of 4,4'-diaminodiphenyl ether.

[0054] After the addition was complete, the temperature was raised to 62°C and reacted for 4 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.15 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 50°C and reacted for 2 hours. The mixture was then added dropwise to 0.9 parts of diethylene glycol treated in an ice-water bath. 0.03 parts of dibutyltin dilaurate were added, and the temperature was raised to 62°C. After reacting for 18 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0055] S12. By weight, mix 1 part of the modified triol prepared in step S11 with 2 parts of 1,4-butanediol, stir evenly, add 0.5 parts of boehmite, ultrasonically disperse for 15 min, add 0.05 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 110 °C, and continue mixing and reacting for 45 min to obtain component A;

[0056] S2. Prepare component B;

[0057] Under a nitrogen atmosphere, 0.62 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 85°C and the reaction was carried out for 2 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0058] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0059] Example 4. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0060] Compared with Example 1, this example increases the amount of diphenyl aminophosphate added in step S2;

[0061] S1. Prepare component A;

[0062] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.2 parts of 4,4'-diaminodiphenyl ether.

[0063] After the addition was complete, the temperature was raised to 62°C and reacted for 4 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.15 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 50°C and reacted for 2 hours. The mixture was then added dropwise to 0.7 parts of diethylene glycol treated in an ice-water bath. 0.03 parts of dibutyltin dilaurate were added, and the temperature was raised to 62°C. After reacting for 18 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0064] S12. By weight, mix 1 part of the modified triol prepared in step S11 with 2 parts of 1,4-butanediol, stir evenly, add 0.5 parts of boehmite, ultrasonically disperse for 15 min, add 0.05 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 110 °C, and continue mixing and reacting for 45 min to obtain component A;

[0065] S2. Prepare component B;

[0066] Under a nitrogen atmosphere, 0.72 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 85°C, and the reaction was carried out for 2 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0067] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0068] Example 5. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0069] S1. Prepare component A;

[0070] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.8 parts of 4,4'-diaminodiphenyl ether.

[0071] After the addition was complete, the temperature was raised to 56°C and reacted for 8 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.4 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 60°C and reacted for 4 hours. The mixture was then added dropwise to 0.9 parts of diethylene glycol treated in an ice-water bath. 0.05 parts of dibutyltin dilaurate were added, and the temperature was raised to 65°C. After reacting for 36 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0072] S12. By weight, mix 3 parts of the modified triol prepared in step S11 with 5 parts of 1,4-butanediol, stir evenly, add 1.5 parts of boehmite, ultrasonically disperse for 30 min, add 0.2 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 120 °C, and continue mixing and reacting for 80 min to obtain component A;

[0073] S2. Prepare component B;

[0074] Under a nitrogen atmosphere, 0.72 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 95°C and the reaction was carried out for 4 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0075] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 5 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0076] Comparative Example 1. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0077] Compared with Example 1, no modified triol was prepared in this comparative example;

[0078] S1. Prepare component A;

[0079] By weight, 0.5 parts boehmite were added to 3 parts 1,4-butanediol, and the mixture was ultrasonically dispersed for 15 min. Then, 0.05 parts KH-550 silane coupling agent were added, the reaction pressure was evacuated to 50 Pa, the temperature was raised to 110 °C, and the mixture was mixed and reacted for another 45 min to obtain component A.

[0080] S2. Prepare component B;

[0081] Under a nitrogen atmosphere, 0.62 parts by weight of diphenyl aminophosphate were dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. 1 part of triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was complete, the temperature was raised to 85°C and the reaction was carried out for 2 hours. Excess solvent was removed by rotary evaporation to obtain component B.

[0082] S3. Mix component A and component B at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0083] Comparative Example 2. A method for preparing a high-safety distributed copper-aluminum composite current collector, comprising the following steps:

[0084] Compared with Example 1, this comparative example uses isophorone diisocyanate as component B;

[0085] S1. Prepare component A;

[0086] S11. Under a nitrogen atmosphere, disperse 1 part by weight of tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate in tetrahydrofuran, mix thoroughly, and then add it dropwise to a mixed solution containing 1.2 parts of 4,4'-diaminodiphenyl ether.

[0087] After the addition was complete, the temperature was raised to 62°C and reacted for 4 hours. Heating was then stopped, and the mixture was cooled to room temperature. The mixture was then added dropwise to a DMF solution containing 1.15 parts of terephthalic acid. After mixing thoroughly, the temperature was raised to 50°C and reacted for 2 hours. The mixture was then added dropwise to 0.7 parts of diethylene glycol treated in an ice-water bath. 0.03 parts of dibutyltin dilaurate were added, and the temperature was raised to 62°C. After reacting for 18 hours, excess solvent was removed by rotary evaporation to obtain the modified triol.

[0088] S12. By weight, mix 1 part of the modified triol prepared in step S11 with 2 parts of 1,4-butanediol, stir evenly, add 0.5 parts of boehmite, ultrasonically disperse for 15 min, add 0.05 parts of KH-550 silane coupling agent, evacuate to a reaction pressure of 50 Pa, heat to 110 °C, and continue mixing and reacting for 45 min to obtain component A;

[0089] S2. Mix component A with isophorone diisocyanate at a mass ratio of 2:1. After mixing for 2 minutes, a modified flame-retardant adhesive is obtained. This modified adhesive is then coated onto both sides of a 4-micron thick biaxially oriented polypropylene film at a coating weight of 5 g / m². 2 A 6-micron thick aluminum foil layer and a copper foil layer were respectively bonded together. The bonding pressure was 0.5 MPa, the bonding temperature was 30℃, and the bonding speed was 50 m / min. After bonding, the material was subjected to aging treatment at 50℃ for 15 seconds. After aging, a high-safety distributed copper-aluminum composite current collector was obtained.

[0090] The samples prepared in Examples 1-5 and Comparative Examples 1-2 were tested:

[0091] Tensile strength: The current collectors prepared in Examples 1-5 and Comparative Examples 1-2 were made into 150×20mm high-safety distributed copper-aluminum composite current collectors; then the narrower ends were placed at both ends of a tensile testing machine and fixed; the tensile testing machine was started to stretch the high-safety distributed copper-aluminum composite current collector. The data recorded at the point of fracture is the tensile strength.

[0092] Elongation: The current collectors prepared in Examples 1-5 and Comparative Examples 1-2 were prepared as 100×15mm high-safety distributed copper-aluminum composite current collectors. The narrower ends were placed at both ends of a tensile testing machine and fixed. The tensile testing machine was started to perform a tensile test on the sample. The length between the upper and lower clamps was set to 50mm before the test. The sample was stretched at a tensile speed of 100mm / min until the sample was just broken. The distance between the two clamps was recorded as L1. The elongation of the sample = (L1-L0) / L0.

[0093] Limiting Oxygen Index (LOI): The limiting oxygen index of the polymer film coated with the flame-retardant adhesive layer was measured using a limiting oxygen index meter according to GB 2406 standard. Each separator was measured three times using the limiting oxygen index meter, and the average value was calculated to one decimal place. The calculation formula is as follows: (Limiting Oxygen Index OI) = O2 / (O2+N2)*100%.

[0094] Peel strength: According to the GB / T 1457-2005 testing standard, the current collectors prepared in Examples 1-5 and Comparative Examples 1-2 were prepared into 100×15mm high-safety distributed copper-aluminum composite current collectors. Then, a stainless steel plate with a surface roughness of 50±25nm was first wiped with an alcohol-soaked lint-free cloth. Then, the metal layer of the sample to be tested was fixed to the stainless steel plate with double-sided tape. After rolling back and forth twice with a 2kg manual pressure roller, the stainless steel plate with the sample to be tested was installed on the machine fixture. A multi-functional tensile testing machine was used to perform 180° peeling. The tensile speed of the multi-functional tensile testing machine was set to 100mm / min. The peel test was started and stopped when the copper foil or aluminum foil of the high-safety distributed copper-aluminum composite current collector was completely peeled off from the polymer layer. The peel force value was then read.

[0095] Peel strength after high-temperature aging: According to the GB / T 1457-2005 testing standard, the current collectors prepared in Examples 1-5 and Comparative Examples 1-2 were prepared into 100×15mm high-safety distributed copper-aluminum composite current collectors. Then, a stainless steel plate with a surface roughness of 50±25nm was wiped with an alcohol-soaked lint-free cloth. After that, the metal layer of the sample to be tested was fixed to the stainless steel plate with double-sided tape. After rolling back and forth twice with a 2kg manual pressure roller, the plate was heated to 85℃ and stored for 7 days. Then, the stainless steel plate with the sample to be tested was installed on the machine fixture, and a multi-functional tensile testing machine was used to perform 180° peeling. The tensile speed of the multi-functional tensile testing machine was set to 100mm / min. The peel test was started and stopped when the copper foil or aluminum foil of the high-safety distributed copper-aluminum composite current collector was completely peeled off from the polymer layer. The peel force value was then read.

[0096]

[0097]

[0098] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-safety distributed copper-aluminum composite current collector, characterized in that: The high-security distributed copper-aluminum composite current collector consists of an aluminum foil layer on the upper surface, a polymer film on the inner side, and a copper foil layer on the lower surface. The polymer film has flame-retardant adhesive layers on both sides for bonding and fixing the aluminum foil layer and the copper foil layer. The flame-retardant adhesive layer is prepared by coating and drying a modified flame-retardant adhesive, with a single-layer coating amount of 1-20 g / m². 2 ; The modified flame-retardant adhesive is composed of component A and component B. The mass ratio of component A to component B is (2-4.5):1; By weight, component A comprises the following components: 1-3 parts modified triol, 2-5 parts diol, 0.5-1.5 parts boehmite, and 0.05-0.2 parts silane coupling agent; The modified triol was prepared by the following steps: Under a nitrogen atmosphere, 1,2,4-tris(epoxyethylene methyl) ester of 1,2,4-phenyltricarboxylate was dispersed in tetrahydrofuran and mixed evenly. Then, it was added dropwise to a mixed solution containing 4,4'-diaminodiphenyl ether. After the addition was completed, the temperature was raised to 62-65℃ and reacted for 4-8 hours. After the reaction was stopped and cooled to room temperature, it was added dropwise to a DMF solution containing terephthalic acid. After the mixture was mixed evenly, the temperature was raised to 50-60℃ and reacted for 2-4 hours. Then, it was added dropwise to diethylene glycol treated in an ice-water bath. Dibutyltin dilaurate was added, and the temperature was raised to 62-65℃. After the reaction was carried out for 18-36 hours, the excess solvent was removed by rotary evaporation to obtain the modified triol. The diol is any one of polyhexanediol carbonate diol, polyethylene adipate diol, ethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexanediol; the silane coupling agent is KH-550 silane coupling agent. Component B is prepared by reacting diphenyl aminophosphate with triphenylmethane triisocyanate.

2. The high-security distributed copper-aluminum composite current collector according to claim 1, characterized in that: The polymer film is any one of polypropylene, polyethylene, polyethylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, and polyamide film, with a thickness of 4-20 μm.

3. The high-security distributed copper-aluminum composite current collector according to claim 1, characterized in that: The aluminum foil layer is made of double-sided smooth, double-sided rough, or single-sided smooth and single-sided rough rolled aluminum foil with a thickness of 5-20μm. The copper foil layer is made of electrolytic copper foil or rolled copper foil, with a thickness of 2-15 μm.

4. A method for preparing a high-safety distributed copper-aluminum composite current collector as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Prepare component A; S11. Under a nitrogen atmosphere, tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate was dispersed in tetrahydrofuran and mixed thoroughly. Then, it was added dropwise to a mixed solution containing 4,4'-diaminodiphenyl ether. After the addition was complete, the temperature was raised to 62-65℃ and reacted for 4-8 hours. Then, the heating was stopped and the mixture was cooled to room temperature. Then, it was added dropwise to a DMF solution containing terephthalic acid and mixed thoroughly. Then, the temperature was raised to 50-60℃ and reacted for 2-4 hours. Then, it was added dropwise to diethylene glycol treated in an ice-water bath. Dibutyltin dilaurate was added, and the temperature was raised to 62-65℃. After reacting for 18-36 hours, excess solvent was removed by rotary evaporation to obtain the modified triol. S12. Mix the modified triol and diol prepared in step S11, stir evenly, add boehmite, ultrasonically disperse for 15-30 min, add silane coupling agent, evacuate to the reaction pressure of 0-500 Pa, heat to 110-120℃, continue mixing and reacting for 45-80 min to obtain component A. S2. Prepare component B; Diphenyl aminophosphate was dissolved in DMAc and mixed thoroughly to obtain a diphenyl aminophosphate solution. Triphenylmethane triisocyanate was dispersed in DMF and mixed thoroughly. The mixture was then heated to a constant temperature in an ice-water bath. Under a nitrogen atmosphere, the diphenyl aminophosphate solution was added dropwise while stirring. After the addition was completed, the temperature was raised to 85-95℃ and the reaction was carried out for 2-4 hours. Excess solvent was removed by rotary evaporation to obtain component B. S3. Mix component A and component B for 2-5 minutes to obtain a modified flame-retardant adhesive. Coat both sides of the polymer film with the modified adhesive and then attach aluminum foil and copper foil layers respectively. After aging treatment, a high-safety distributed copper-aluminum composite current collector is obtained.

5. The method for preparing a high-safety distributed copper-aluminum composite current collector according to claim 4, characterized in that: In step S11, by weight, the mass ratio of 1,2,4-tris(epoxyethylene methyl) 1,2,4-benzenetricarboxylate, 4,4'-diaminodiphenyl ether, terephthalic acid, and diethylene glycol is 1:(1.2-1.8):(1.15-1.4):(0.7-0.9).

6. The method for preparing a high-safety distributed copper-aluminum composite current collector according to claim 4, characterized in that: The mass ratio of dibutyltin dilaurate to diethylene glycol is (0.03-0.05):(0.7-0.9).

7. The method for preparing a high-safety distributed copper-aluminum composite current collector according to claim 4, characterized in that: In step S2, the mass ratio of diphenyl aminophosphate to triphenylmethane triisocyanate is (0.62-0.72):

1.

8. The method for preparing a high-safety distributed copper-aluminum composite current collector according to claim 4, characterized in that: In step S3, when bonding the aluminum foil layer and the copper foil layer, the bonding pressure is 0.5-1.5MPa, the bonding temperature is 30-40℃, and the bonding speed is 50-200m / min; During the aging process, the aging temperature is 30-80℃ and the aging time is 12-30s.

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