Production process of ultrathin soft package battery tab

Abstract

The invention relates to the technical field of lithium batteries, in particular to a production process of an ultrathin soft-package battery tab, a metal adhesive is added into a metal conductor and tab glue, double-layer tab glue is used, the metal adhesive is modified polyurethane, and the modified polyurethane is prepared from epoxy resin, polypropylene glycol, diphenylmethane-4, 4-diisocyanate, 2, 4-diphenyl-2, 4-diisocyanate, 2, 4-diphenyl-1, 3, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 3-triazole-1, 3-triazole-1, the metal adhesive is prepared from 2, 2-diimidazole methane and gamma-aminopropyltriethoxysilane, the performance of polyurethane can be improved, an imidazole group in the 2, 2-diimidazole methane can be chelated with metal, and the bonding strength of the metal adhesive and the metal is improved; the first tab glue layer is a modified polypropylene layer, so that the melting point of the first tab glue layer is reduced, the difficulty of thermal compounding between a metal conductor and tab glue in the tab production process is reduced, hydroxyl in epoxy acrylate can react with a metal adhesive, the bonding uniformity and the bonding strength of the metal conductor and the tab glue are improved, and the possibility that the tab glue falls off is reduced; wide application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and particularly to a production process for the tabs of an ultra-thin soft-pack battery. Background Art

[0002] A soft-pack battery, also known as a polymer soft-pack lithium-ion battery, is a battery that uses an aluminum-plastic composite film as the outer casing material. The structural feature of a soft-pack battery is that it contains a positive electrode, a negative electrode, a separator, and an electrolyte inside, but the external packaging does not use a metal shell. Instead, multiple layers of plastic and metal foil (such as aluminum) are combined through heat-sealing technology to form a flexible package.

[0003] In a lithium-ion battery, the metal conductor component that leads the positive and negative electrodes of the battery out of the battery core and undertakes the energy exchange inside and outside the battery during charging and discharging of the battery is called a tab. The battery tab is composed of a metal conductor and an insulating tab glue. Generally, aluminum tabs are used for the positive electrode of a lithium-ion power battery, nickel or nickel-plated copper tabs are used for the negative electrode, and there are also copper tabs and stainless-steel tabs, etc.

[0004] Generally, metal aluminum is used for the positive electrode tab of a lithium-ion battery. Aluminum has good electrical conductivity. At the same time, at a relatively high potential, metal aluminum has a more stable and smaller polarization potential range than copper, is not prone to alloying reaction with Li, and has good chemical stability, making it more suitable as the positive electrode tab of a lithium-ion battery. Under the working voltage of a lithium-ion battery, aluminum will undergo an oxidation reaction as the positive electrode tab material, but there is a layer of oxide composed of Al 2 O 3 on the surface of aluminum. This oxide film protects the aluminum tab from oxidation reaction. However, the corrosion resistance of this oxide film is poor. When the battery is in a working state for a long time, this oxide layer fails to protect the aluminum tab, resulting in a corrosion reaction inside the battery and a series of problems. Generally, metal nickel is used for the negative electrode tab of a lithium-ion battery. The standard electrode potential of nickel is -0.246V, which is lower than the electrode potential of the carbon material used for the negative electrode of a lithium-ion battery. Therefore, during the operation of the battery, the negative electrode tab is stable. However, if aluminum is used as the negative electrode tab material, aluminum will react with lithium at a low potential to form a lithium-aluminum alloy, affecting the battery performance.

[0005] After long-term use, the existing tab is prone to problems such as tab glue shedding, decreased insulation performance, and poor corrosion resistance because the metal conductor strip cannot be stably connected to the tab glue material, which affects the normal use of the battery. The patent technical literature CN108134042B discloses a production process for the tab of a high-sealing and leak-proof lithium-ion battery. The base metal material is subjected to bright rolling and matte rolling, followed by electrochemical polishing and passivation, then cleaned and dried. The rolled metal conductor in strip form is cut into sections, ultrasonically cleaned and dried, treated with deionized water and dried. Finally, a strip-shaped polymer insulating film is attached to the sectioned metal conductor. The tab of the lithium-ion battery produced by this process has an increased surface roughness of the metal conductor, which improves the effective contact area between the metal conductor and the polymer insulating film, so it can effectively improve the adhesion force and make the two bond more firmly. However, it does not solve the problem that the tab glue is difficult to be heated evenly and is prone to shedding.

[0006] Therefore, according to the relevant technologies described above, there is an urgent need to develop a production process for the tab of an ultra-thin soft-pack battery. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a production process for the tab of an ultra-thin soft-pack battery to solve the problems of easy shedding of the tab glue and poor corrosion resistance after long-term use in the prior art.

[0008] Based on the above purpose, the present invention provides a production process for the tab of an ultra-thin soft-pack battery.

[0009] A production process for the tab of an ultra-thin soft-pack battery, including a metal conductor and tab glue; The metal conductor includes a conductor and an adhesive area; The adhesive area bonds a metal adhesive layer, and the metal adhesive layer bonds the tab glue; The tab glue includes a first tab glue layer and a second tab glue layer; The metal adhesive layer bonds the first tab glue layer, and the first tab glue layer bonds the second tab glue layer; The metal adhesive layer and the second tab layer are bonded on both sides of the first tab layer; The metal adhesive layer is prepared from a metal adhesive; The metal adhesive is a modified polyurethane; The modified polyurethane is prepared from epoxy resin, polypropylene glycol, diphenylmethane-4,4-diisocyanate, 2,2-dimethylimidazole methane, and γ-aminopropyltriethoxysilane; The first tab glue layer is a modified polypropylene; The modified polypropylene is prepared from propylene, ethylene, and epoxy acrylate; The second tab glue layer is polypropylene.

[0010] Preferably, the preparation method of the metal adhesive is as follows: Step A1. Under a nitrogen atmosphere, diphenylmethane-4,4-diisocyanate is added to polypropylene glycol, γ-aminopropyltriethoxysilane, and N,N-dimethylformamide, and the reaction is carried out at 70-80 °C for 3-5 h to obtain a polyurethane prepolymer; Step A2. Continuously introduce nitrogen, raise the temperature to 85-90 °C, add epoxy resin, 2,2-dimethylimidazole methane, dibutyltin dilaurate, and an active diluent to the polyurethane prepolymer, and react for 1-4 h to obtain a metal adhesive.

[0011] Preferably, the dosage ratio of diphenylmethane-4,4-diisocyanate, polypropylene glycol, γ-aminopropyltriethoxysilane, and N,N-dimethylformamide in Step A1 is 20-30 g: 30-35 mL: 5-8 mL: 400-500 mL.

[0012] Preferably, the mass ratio of the polyurethane prepolymer, epoxy resin, 2,2-dimethylimidazole methane, dibutyltin dilaurate, and active diluent in Step A2 is 55-65: 15-20: 10-15: 0.3-0.5: 1-3.

[0013] Preferably, the preparation method of the first tab glue layer is as follows: Step B1. Propylene, ethylene, and a metallocene catalyst are added to n-hexane, and the reaction is carried out at 3-8 MPa and 70-80 °C for 3-5 h to obtain copolymerized polypropylene, followed by plasma treatment. After evacuating to 100 Pa - 200 Pa, argon is introduced, and the gas flow rate is 20-40 cm 3 / s, the power is 20-100 KW, the voltage is 380 V, and the treatment time is 30-100 s. Then ammonia is introduced, and the gas flow rate is 20-40 cm 3 / s, the power is 20-100 KW, the voltage is 380 V, and the treatment time is 30-100 s; Step B2. The treated copolymerized polypropylene is immersed in toluene containing epoxy acrylate, an activator, and an initiator, and after a water bath at 60-70 °C for 5-8 h, ultraviolet irradiation treatment is carried out, rinsed 3-5 times with deionized water, and dried for 3-5 h to obtain the first tab glue layer.

[0014] Preferably, the dosage ratio of propylene, ethylene, the metallocene catalyst, and n-hexane in Step B1 is 60-80 mL: 5-8 mL: 0.3-0.5 g: 700-800 mL; The metallocene catalyst is methylaluminoxane; In step B2, the mass ratio of the treated copolymerized polypropylene, epoxy acrylate, activator, initiator and toluene is 70-90:20-30:1-2:0.3-0.5:60-80; The activator is sodium petroleum sulfonate; The initiator is azobisisobutyronitrile.

[0015] Preferably, the production process of the ultra-thin soft-pack battery tab is as follows: Step C1. The conductor is subjected to bright rolling forming by a rolling mill, then dull rolling forming, then electrochemically polished, cleaned and dried, and passivated to obtain a treated conductor; Step C2. The surface of the adhesive area of the treated conductor is coated with a metal adhesive to obtain a metal adhesive layer, then the first tab adhesive layer is adhered to the metal adhesive layer, and finally the second tab adhesive layer is adhered to the first tab adhesive; Step C3. Heat pressing is carried out by a high-frequency forming hot press to obtain an ultra-thin soft-pack battery tab.

[0016] Preferably, when carrying out dull rolling forming in step C1, the surface roughness of the conductor is 35-45 µm; When carrying out electrochemically polishing in step C1, the surface roughness of the conductor is 15-18 µm; The conductor is any one of aluminum, nickel and nickel-plated copper.

[0017] Preferably, the thickness of the metal adhesive layer in step C2 is 3-5 µm; The thickness of the first tab adhesive layer in step C2 is 30-50 µm; The thickness of the second tab adhesive layer in step C2 is 10-20 µm.

[0018] Preferably, the heat pressing temperature in step C3 is 150-180 °C, the pressure is 3-5 MPa, and the time is 30-35 s.

[0019] Advantages of the present invention: The present invention provides a production process of an ultra-thin soft-pack battery tab. By adding a metal adhesive to the metal conductor and tab adhesive, and using measures such as double-layer tab adhesive, the bonding uniformity and bonding strength are improved, and the possibility of tab adhesive shedding can be reduced in the case of long-term use; The metal adhesive provided by the present invention is a modified polyurethane, which is prepared from epoxy resin, polypropylene glycol, diphenylmethane - 4,4 - diisocyanate, 2,2 - dimidazolylmethane and γ - aminopropyltriethoxysilane. γ - aminopropyltriethoxysilane has excellent thermal stability, good weather resistance and insulation properties, which can improve the performance of polyurethane. The hydroxyl groups in the epoxy resin can react with the isocyanate groups in the polyurethane to form an interpenetrating network structure polymer, improving the performance of the metal adhesive. The imidazole groups in 2,2 - dimidazolylmethane can chelate with metals, increasing the bonding strength between the metal adhesive and the metal; The first tab glue layer provided by the present invention is a modified polypropylene layer, which is prepared from propylene, ethylene and epoxy acrylate; by adding a small amount of ethylene during the polypropylene polymerization process to form a copolymer, its melting point can be lowered, reducing the difficulty of thermal compounding between the metal conductor and the tab glue during the tab production process. The hydroxyl groups in the epoxy acrylate can react with the metal adhesive, improving the bonding uniformity and strength between the two. The combined action of the two reduces the possibility of the tab glue falling off. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic structural diagram of the tab of the ultra - thin soft - package battery in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further details the present invention with specific embodiments.

[0023] The sources and properties of some raw materials used in the present invention are as follows: Diphenylmethane - 4,4 - diisocyanate was purchased from Shanghai Xiangkang Technology Development Co., Ltd.; 2,2 - dimidazolylmethane was purchased from Beijing Huawei Ruike Chemical Co., Ltd.; γ - aminopropyltriethoxysilane was purchased from Shanghai Aladdin Reagent Co., Ltd.; the active diluent model is 660A, which was purchased from Changzhou Hongfa Electronic Materials Co., Ltd.; the metallocene catalyst is methylaluminoxane, which was purchased from Sinopharm Chemical Reagent Co., Ltd.; epoxy acrylate was purchased from Hubei Yongkuo Technology Co., Ltd.

[0024] Example 1: A production process for the tab of an ultra - thin soft - package battery, including the following steps: S1. Under a nitrogen atmosphere, 20 g of diphenylmethane - 4,4 - diisocyanate was added to 30 mL of polypropylene glycol, 5 mL of γ - aminopropyltriethoxysilane, and 400 mL of N,N - dimethylformamide, and the reaction was carried out at 70 °C for 3 h to obtain a polyurethane prepolymer; S2. Continuing to introduce nitrogen, the temperature was raised to 85 °C. 15 g of epoxy resin, 10 g of 2,2 - dimidazolylmethane, 0.3 g of dibutyltin dilaurate, and 1 g of active diluent 660A were added to 55 g of the polyurethane prepolymer, and the reaction was carried out for 1 h to obtain a metal adhesive; S3. 60 mL of propylene, 5 mL of ethylene, and 0.3 g of methylaluminoxane were added to 700 mL of n - hexane, and the reaction was carried out at 3 MPa and 70 °C for 3 h to obtain copolymerized polypropylene. After plasma treatment, the vacuum was pumped to 100 Pa, and then argon was introduced. The gas flow rate was 20 cm 3 / s, the power was 20 KW, the voltage was 380 V, and the treatment time was 30 s. Then ammonia was introduced. The gas flow rate was 20 cm 3 / s, the power was 20 KW, the voltage was 380 V, and the treatment time was 30 s; S4. The treated 70 g of copolymerized polypropylene was soaked in 60 g of toluene containing 20 g of epoxy acrylate, 1 g of sodium petroleum sulfonate, and 0.3 g of azobisisobutyronitrile. After a 5 - h water bath at 60 °C, ultraviolet irradiation treatment was carried out, and it was rinsed 3 times with deionized water and dried for 3 h to obtain the first tab glue layer; S5. The aluminum conductor was subjected to bright rolling forming by a rolling mill and then matte rolling forming until the surface roughness of the conductor was 35 µm. Then it was electrochemically polished until the surface roughness of the conductor was 15 µm. After cleaning and drying, passivation was carried out to obtain the treated conductor; S6. The bonding area surface of the treated conductor was coated with the metal adhesive, and the thickness of the metal bonding layer was 3 µm to obtain the metal bonding layer. Then the first tab glue layer was bonded to the metal bonding layer, and finally the second tab glue layer was bonded to the first tab glue layer. The thickness of the first tab glue layer was 30 µm, and the thickness of the second tab glue layer was 10 µm; S7. Heating and pressing were carried out by a high - frequency forming hot press to obtain an ultra - thin soft - pack battery tab. The heating and pressing temperature was 150 °C, the pressure was 3 MPa, and the time was 30 s.

[0025] Example 2: A production process for an ultra - thin soft - pack battery tab, comprising the following steps: S1. Under a nitrogen atmosphere, 24 g of diphenylmethane - 4,4 - diisocyanate was added to 32 mL of polypropylene glycol, 6 mL of γ - aminopropyltriethoxysilane, and 440 mL of N,N - dimethylformamide, and the reaction was carried out at 74 °C for 4 h to obtain a polyurethane prepolymer; S2. Continuously introduce nitrogen, heat up to 86 °C, add 16 g of epoxy resin, 12 g of 2,2 - dimidazole methane, 0.4 g of dibutyltin dilaurate and 2 g of reactive diluent 660A into 58 g of polyurethane prepolymer, react for 2 h to obtain a metal adhesive; S3. Add 62 mL of propylene, 6 mL of ethylene and 0.4 g of methylaluminoxane into 740 mL of n - hexane, react at 4 MPa and 74 °C for 4 h to obtain copolymerized polypropylene, then carry out plasma treatment. After evacuating to 140 Pa, introduce argon, the gas flow rate is 24 cm 3 / s, the power is 60 KW, the voltage is 380 V, the treatment time is 50 s, then introduce ammonia, the gas flow rate is 28 cm 3 / s, the power is 60 KW, the voltage is 380 V, the treatment time is 50 s; S4. Immerse 74 g of the treated copolymerized polypropylene in 66 g of toluene containing 24 g of epoxy acrylate, 1.4 g of sodium petroleum sulfonate and 0.4 g of azobisisobutyronitrile, carry out water - bath at 64 °C for 6 h, then carry out ultraviolet irradiation treatment, rinse 4 times with deionized water, and dry for 4 h to obtain the first tab glue layer; S5. Pass the aluminum conductor through a rolling mill for bright rolling and then through a dull rolling to make the surface roughness of the conductor reach 38 µm, then carry out electrochemical polishing to make the surface roughness of the conductor reach 16 µm, carry out cleaning and drying, and carry out passivation to obtain the treated conductor; S6. Coat the adhesive area surface of the treated conductor with the metal adhesive, the thickness of the metal adhesive layer is 4 µm to obtain the metal adhesive layer, then bond the first tab glue layer to the metal adhesive layer, and finally bond the second tab glue layer to the first tab glue layer, where the thickness of the first tab glue layer is 38 µm and the thickness of the second tab glue layer is 14 µm; S7. Carry out heating and pressing through a hot press for high - frequency forming to obtain an ultra - thin soft - pack battery tab, where the heating and pressing temperature is 160 °C, the pressure is 4 MPa, and the time is 32 s.

[0026] Example 3: A production process of an ultra - thin soft - pack battery tab, including the following steps: S1. Under a nitrogen environment, add 28 g of diphenylmethane - 4,4 - diisocyanate into 34 mL of polypropylene glycol, 7 mL of γ - aminopropyltriethoxysilane and 480 mL of N,N - dimethylformamide, react at 78 °C for 4.5 h to obtain a polyurethane prepolymer; S2. Continuously introduce nitrogen, heat up to 88 °C, add 18 g of epoxy resin, 14 g of 2,2 - dimidazole methane, 0.45 g of dibutyltin dilaurate and 2.5 g of reactive diluent 660A into 62 g of polyurethane prepolymer, react for 3 h to obtain a metal adhesive; S3. Add 68 mL of propylene, 7 mL of ethylene, and 0.45 g of methylaluminoxane into 780 mL of n - hexane, react at 6 MPa and 78 °C for 4.5 h. After obtaining the copolymerized polypropylene, perform plasma treatment. After evacuating to 180 Pa, introduce argon with a gas flow rate of 32 cm 3 / s, a power of 80 KW, a voltage of 380 V, and a treatment time of 80 s. Then introduce ammonia with a gas flow rate of 35 cm 3 / s, a power of 80 KW, a voltage of 380 V, and a treatment time of 80 s; S4. Immerse 82 g of the treated copolymerized polypropylene in 72 g of toluene containing 28 g of epoxy acrylate, 1.8 g of sodium petroleum sulfonate, and 0.45 g of azobisisobutyronitrile. After water - bathing at 68 °C for 7 h, perform ultraviolet irradiation treatment, rinse 5 times with deionized water, and dry for 4.5 h to obtain the first tab glue layer; S5. After the nickel conductor is polished to a bright finish by a rolling mill and then to a dull finish until the surface roughness of the conductor is 40 µm, perform electrochemical polishing until the surface roughness of the conductor is 17 µm. After cleaning and drying, perform passivation to obtain the treated conductor; S6. Coat the adhesive area surface of the treated conductor with a metal adhesive, with the thickness of the metal adhesive layer being 5 µm to obtain the metal adhesive layer. Then bond the first tab glue layer to the metal adhesive layer, and finally bond the second tab glue layer to the first tab glue layer, where the thickness of the first tab glue layer is 45 µm and the thickness of the second tab glue layer is 18 µm; S7. Perform heating and pressing through a hot press for high - frequency forming to obtain the ultra - thin soft - package battery tab, where the heating and pressing temperature is 170 °C, the pressure is 5 MPa, and the time is 34 s.

[0027] Example 4: A production process for an ultra - thin soft - package battery tab, comprising the following steps: S1. Under a nitrogen environment, add 30 g of diphenylmethane - 4,4 - diisocyanate into 35 mL of polypropylene glycol, 8 mL of γ - aminopropyltriethoxysilane, and 500 mL of N,N - dimethylformamide, and react at 80 °C for 5 h to obtain a polyurethane prepolymer; S2. Continuously introduce nitrogen, raise the temperature to 90 °C, add 20 g of epoxy resin, 15 g of 2,2 - dimidazolemethane, 0.5 g of dibutyltin dilaurate, and 3 g of reactive diluent 660A into 65 g of the polyurethane prepolymer, and react for 4 h to obtain the metal adhesive; S3. Add 80 mL of propylene, 8 mL of ethylene, and 0.5 g of methylaluminoxane into 800 mL of n - hexane, react at 8 MPa and 80 °C for 5 h. After obtaining the copolymerized polypropylene, perform plasma treatment. After evacuating to 200 Pa, introduce argon with a gas flow rate of 40 cm 3 / s, with a power of 100 KW, a voltage of 380 V, a processing time of 100 s, and then ammonia is introduced, and the gas flow rate is 40 cm 3 / s, with a power of 100 KW, a voltage of 380 V, and a processing time of 100 s; S4. Immerse 90 g of the treated copolymer polypropylene in 80 g of toluene containing 30 g of epoxy acrylate, 2 g of sodium petroleum sulfonate, and 0.5 g of azobisisobutyronitrile, perform ultraviolet irradiation treatment after water bath at 70 °C for 8 h, rinse 5 times with deionized water, and dry for 5 h to obtain the first tab glue layer; S5. The copper-plated nickel conductor is subjected to bright rolling forming through a rolling mill and then to matte rolling forming until the surface roughness of the conductor is 45 µm, and then electrochemically polished until the surface roughness of the conductor is 18 µm, washed and dried, and passivated to obtain the treated conductor; S6. Coat the bonding area surface of the treated conductor with a metal bonding agent, and the thickness of the metal bonding layer is 5 µm to obtain the metal bonding layer. Then bond the first tab glue layer to the metal bonding layer, and finally bond the second tab glue layer to the first tab glue. Among them, the thickness of the first tab glue layer is 50 µm, and the thickness of the second tab glue layer is 20 µm; S7. Heat and press through a hot press for high-frequency forming to obtain an ultra-thin soft-pack battery tab, where the heat and press temperature is 180 °C, the pressure is 5 MPa, and the time is 35 s.

[0028] Comparative Example 1: In this comparative example, compared with Example 1, γ-aminopropyltriethoxysilane was not added during the preparation process of the metal bonding agent, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally an ultra-thin soft-pack battery tab was obtained.

[0029] Comparative Example 2: In this comparative example, compared with Example 1, epoxy resin was not added during the preparation process of the metal bonding agent, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally an ultra-thin soft-pack battery tab was obtained.

[0030] Comparative Example 3: In this comparative example, compared with Example 1, 2,2-bis(imidazol-1-yl)methane was not added during the preparation process of the metal bonding agent, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally an ultra-thin soft-pack battery tab was obtained.

[0031] Comparative Example 4: In this comparative example, compared with Example 1, ethylene was not added during the preparation process of the first tab glue layer, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally an ultra-thin soft-pack battery tab was obtained.

[0032] Comparative Example 5: This comparative example is the same as Example 1 in all steps and parameters except that the first ear glue layer is not added during the preparation of the ultra-thin soft-pack battery tab. This comparative example will not be repeated here, and finally, the ultra-thin soft-pack battery tab is obtained.

[0033] Comparative Example 6: This comparative example is the same as Example 1 in all steps and parameters except that the metal bonding agent is not added during the preparation of the ultra-thin soft-pack battery tab. This comparative example will not be repeated here, and finally, the ultra-thin soft-pack battery tab is obtained.

[0034] Performance test: Peel strength test: The ear glue peel strength experiment was carried out using an HMM-JERY51 type ear glue hot press and a QT-6203 type universal material testing machine. The ultra-thin soft-pack battery tabs prepared in Examples 1-4 and Comparative Examples 1-6 were completely immersed in the lithium-ion power battery electrolyte, and soaked at a constant temperature of 85 °C for 24 h. The electrolyte composition was 1 mo / L LiPF 6 dissolved in dimethyl carbonate and ethylene carbonate with a mass ratio of 1:1. After soaking, the tabs were rinsed clean with absolute ethanol and deionized water in turn, and the joints between the ear glue and the metal conductor were observed for bubbles or debonding. The universal material testing machine was used to test the peel strength between the ear glue and the metal conductor before and after electrolyte soaking, and the peeling rate was 50 mm / min. Three parallel samples were taken for each test, and the average value of the measurement results of the three parallel samples was taken as the average peel strength of the sample.

[0035] Corrosion resistance test: The salt spray test was carried out on the ultra-thin soft-pack battery tabs prepared in Examples 1-4 and Comparative Examples 1-6 with reference to the test standard of GB / T10125-2012 "Artificial Atmosphere Corrosion Test: Salt Spray Test". The experimental equipment was the YWX / F-150 salt spray chamber produced by Jiangsu Anwente Experimental Equipment Co., Ltd. The salt spray test temperature was 35 ± 2 °C, the NaC1 concentration was 50 g / L, and the pH value was 6.5-7.2. After the experiment, the salt spray grade evaluation was carried out with reference to the standard of GB / T6461-2002 "Rating of Specimens and Test Pieces after Corrosion Tests on Metallic Substrates with Metallic and Other Inorganic Coatings". Among them, grade 10 has the best corrosion resistance and grade 0 has the worst corrosion resistance. If the test result is between two grades, it is rated in increments of 0.5.

[0036] Conductivity test: In this paper, a JK2512B DC low-resistance tester was used to measure the multi-point resistance at different positions of the tabs of the ultra-thin soft-pack batteries prepared in Examples 1-4 and Comparative Examples 1-6, and the tab resistivity was calculated through the average resistance. The measured sample area was 6 cm × 5 cm. When measuring the resistance, the resistance between five points of a-d, a-e, a-f, b-d, and b-e was measured respectively, and the average value was calculated. The length, width, and thickness of the five points were measured respectively, the average length, average width, and average thickness of the conductor were calculated, and the average resistivity of the tab was calculated through the resistivity calculation formula.

[0037] Resistivity calculation formula: ρ = R×S / L; where ρ is the resistivity of the sample, with the unit of Ω•m; R is the average resistance value of the sample, with the unit of Ω, S is the average cross-sectional area of the sample, with the unit of m 2 ; L is the sample length, with the unit of m.

[0038] Table 1 Data summary of Examples 1-4 and Comparative Examples 1-6

[0039] Data analysis: As can be seen from Table 1, the tabs of the ultra-thin soft-pack batteries prepared by the present invention have stronger bonding strength and mechanical properties, the prepared tabs have good electrical conductivity, while the tab glue has good insulation; This may be because the present invention improves the bonding uniformity and bonding strength by adding a metal adhesive to the metal conductor and the tab glue, and using double-layer tab glue and other measures, which can reduce the possibility of tab glue shedding under long-term use; the metal adhesive provided by the present invention is a modified polyurethane, and the modified polyurethane is prepared from epoxy resin, polypropylene glycol, diphenylmethane-4,4-diisocyanate, 2,2-dimethylimidazole methane, and γ-aminopropyltriethoxysilane. γ-aminopropyltriethoxysilane has good weather resistance and insulation, which can improve the performance of polyurethane. The lack of γ-aminopropyltriethoxysilane may lead to a decrease in the performance of the metal adhesive and a reduction in the bonding effect with the tab glue; the hydroxyl group in the epoxy resin can react with the isocyanate group in the polyurethane to form an interpenetrating network structure polymer, improving the performance of the metal adhesive. The lack of epoxy resin may lead to a decrease in the bonding strength of the metal adhesive; the imidazole group in 2,2-dimethylimidazole methane can chelate with metals, increasing the bonding strength between the metal adhesive and the metal. Without the 2,2-dimethylimidazole methane grafted on the polyurethane, the metal adhesive cannot bond well with the metal and is prone to falling off after long-term use; The first tab glue layer provided by the present invention is a modified polypropylene layer, and the modified polypropylene layer is prepared from propylene, ethylene and epoxy acrylate; by adding a small amount of ethylene during the polypropylene polymerization process to form a copolymer, its melting point can be lowered, reducing the difficulty of thermal compounding between the metal conductor and the tab glue during the tab production process, and the hydroxyl group in the epoxy acrylate can react with the metal binder to improve the bonding uniformity and bonding strength between the two. The combined action of the two reduces the possibility of the tab glue falling off.

[0040] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0041] The present invention aims to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A production process for ultra-thin soft-pack battery tabs, characterized in that: Including metal conductor and ear glue; The metal conductor includes a conductor and a glue-attaching area; The adhesive bonding area is bonded to the metal adhesive layer, and the metal adhesive layer is bonded to the tab adhesive; The tab glue comprises a first tab glue layer and a second tab glue layer; The metal bonding layer is bonded to the first tab adhesive layer, and the first tab adhesive layer is bonded to the second tab adhesive layer; The metal bonding layer and the second tab layer are bonded to both sides of the first tab layer; The metal bonding layer is prepared from a metal bonding agent; The metal adhesive is modified polyurethane; The modified polyurethane is prepared from epoxy resin, polypropylene glycol, diphenylmethane-4,4-diisocyanate, 2,2-diimidazole methane and γ-aminopropyltriethoxysilane; The first tab rubber layer is prepared from modified polypropylene; The modified polypropylene is prepared from propylene, ethylene and epoxy acrylate; The second tab rubber layer is made of polypropylene.

2. The production process of an ultra-thin soft-pack battery tab according to claim 1, characterized in that: The preparation method of the metal adhesive is as follows: Step A1. Under a nitrogen environment, diphenylmethane-4,4-diisocyanate is added to polypropylene glycol, γ-aminopropyltriethoxysilane and N,N-dimethylformamide, and reacted at 70-80° C. for 3-5 hours to obtain a polyurethane prepolymer; Step A2. Nitrogen is continuously introduced, the temperature is raised to 85-90° C., epoxy resin, 2,2-diimidazole methane, dibutyltin dilaurate and active diluent are added to the polyurethane prepolymer, and the reaction is carried out for 1-4 hours to obtain a metal adhesive.

3. The production process of an ultra-thin soft-pack battery tab according to claim 2, characterized in that: The usage ratio of diphenylmethane-4,4-diisocyanate, polypropylene glycol, γ-aminopropyltriethoxysilane and N,N-dimethylformamide in step A1 is 20-30 g: 30-35 mL: 5-8 mL: 400-500 mL.

4. The production process of an ultra-thin soft-pack battery tab according to claim 2, characterized in that: The mass ratio of the polyurethane prepolymer, epoxy resin, 2,2-diimidazole methane, dibutyltin dilaurate and active diluent in step A2 is 55-65:15-20:10-15:0.3-0.5:1-3.

5. The production process of an ultra-thin soft-pack battery tab according to claim 1, characterized in that: The preparation method of the first electrode ear glue layer is as follows: Step B1. Add propylene, ethylene and metallocene catalyst into n-hexane, react at 3-8MPa and 70-80°C for 3-5h to obtain copolymerized polypropylene, then perform plasma treatment, evacuate to 100Pa-200Pa, and introduce argon at a gas flow rate of 20-40cm 3 / s, power is 20-100KW, voltage is 380V, treatment time is 30-100s, then ammonia is introduced, gas flow rate is 20-40cm 3 / s, power is 20-100KW, voltage is 380V, and processing time is 30-100s; Step B2. Soak the treated copolymerized polypropylene in toluene containing epoxy acrylate, activator and initiator, place in a water bath at 60-70°C for 5-8 hours, then irradiate with ultraviolet light, rinse with deionized water for 3-5 times, and dry for 3-5 hours to obtain the first tab glue layer.

6. The production process of the ultra-thin soft-pack battery tab according to claim 5, characterized in that: The usage ratio of propylene, ethylene, metallocene catalyst and n-hexane in step B1 is 60-80 mL: 5-8 mL: 0.3-0.5 g: 700-800 mL; The metallocene catalyst is methylaluminoxane; The mass ratio of the treated copolymerized polypropylene, epoxy acrylate, activator, initiator and toluene in step B2 is 70-90:20-30:1-2:0.3-0.5:60-80; The activator is sodium petroleum sulfonate; The initiator is azobisisobutyronitrile.

7. The production process of an ultra-thin soft-pack battery tab according to claim 1, characterized in that: The following steps are involved: Step C1. The conductor is subjected to bright rolling and matte rolling by a rolling mill, and then electrochemically polished, cleaned, dried, and passivated to obtain a treated conductor; Step C2. Coating the surface of the adhesive area of ​​the treated conductor with a metal adhesive to obtain a metal adhesive layer, then bonding the first tab adhesive layer to the metal adhesive layer, and finally bonding the second tab adhesive layer to the first tab adhesive; Step C3: Heat and press the battery using a high-frequency forming hot press to obtain an ultra-thin soft-pack battery tab.

8. The production process of the ultra-thin soft-pack battery tab according to claim 7, characterized in that: During the matte rolling process in step C1, the surface roughness of the conductor is 35-45 µm; During the electrochemical polishing described in step C1, the surface roughness of the conductor is 15-18 µm; The conductor is any one of aluminum, nickel and copper plated with nickel.

9. The production process of the ultra-thin soft-pack battery tab according to claim 7, characterized in that: The thickness of the metal bonding layer in step C2 is 3-5 µm; In step C2, the thickness of the first tab glue layer is 30-50 μm; In step C2, the thickness of the second tab glue layer is 10-20 μm.

10. The production process of an ultra-thin soft-pack battery tab according to claim 7, characterized in that: The heating and pressing temperature in step C3 is 150-180° C., the pressure is 3-5 MPa, and the time is 30-35 s.

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