High-safety, long-life and low-attenuation tab and forming method thereof

Abstract

The application belongs to the technical field of lithium batteries, and particularly relates to a tab with high safety, long service life and low attenuation and a forming method thereof, the forming method comprising the following steps: preparing modified tab adhesive; pretreating a metal coil to obtain a metal base material; respectively feeding the modified tab adhesive and the metal base material, feeding the modified tab adhesive to the surface of the metal base material, heating and pressing the metal base material and the modified tab adhesive in an internal heating mode to obtain tab connected material; and single-piece cutting the tab connected material to obtain a tab with high safety and long service life. The tab adhesive is improved through a radiation cross-linking process, the surface of the metal base material is passivated, the conductivity of the tab is improved, and the forming process is optimized through internal heating technology, so that the tensile force, electrolyte resistance attenuation and cycle life of the tab are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a tab with high safety, long service life and low attenuation and a forming method thereof. BACKGROUND

[0002] As a core component of lithium batteries, the tab is a key conductive part connecting the positive and negative active materials and the external circuit, and its performance directly affects the safety, cycle life and reliability of the battery. Under the background of the continuous growth of the demand for high-energy-density batteries in the fields of new energy vehicles and energy storage systems, the tab needs to withstand chemical corrosion in electrochemical reactions, mechanical stress in charge and discharge cycles, and interface stability challenges in high-voltage environments. An ideal tab should have excellent peel strength, electrolyte attenuation resistance and long cycle life to ensure stable operation of the battery under complex working conditions.

[0003] However, the performance bottleneck of the traditional tab significantly restricts the further development of lithium batteries, for example:

[0004] Insufficient peel strength: the traditional tab relies on conventional adhesives to combine with the metal substrate, and its peel strength is generally only about 2.0 MPa. In the battery charging and discharging process, corrosion occurs due to chemical reactions, which easily causes interface debonding and leads to battery failure;

[0005] Poor electrolyte attenuation resistance: when the tab is immersed in aqueous electrolyte for a long time and in a high-temperature environment, the molecular chain of the traditional tab glue is easily eroded by HF in the electrolyte, resulting in a tensile force attenuation of more than 50%, or even complete loss of mechanical properties, which seriously affects the long-term reliability of the battery (there is moisture in the battery production environment, and there is also moisture in the supporting materials);

[0006] Short cycle life: in high-voltage (above 4.5V) and ultrahigh-voltage (above 4.8V) systems, ordinary tabs are prone to bulging and liquid leakage after long-term use due to the insufficient oxidation resistance of the passivation film and the poor stability of the conductive network. The cycle number is lower under ultrahigh voltage, and the service life is shorter, which cannot meet the demand of long-life energy storage equipment.

[0007] Based on the above problems, the application provides a tab with high safety, long service life and low attenuation and a forming method thereof to improve the above problems. SUMMARY

[0008] The application aims to provide a forming method of a high-safety, long-life and low-decay tab, improve the tab rubber through a radiation cross-linking process, passivate the surface of a metal substrate, and improve the conductivity of the tab. The inner heating technology optimizes the forming process, significantly improves the tensile strength, electrolyte decay resistance and cycle life of the tab. The improved tab meets the requirements of high-energy density batteries, especially exhibits high-voltage resistance and cycle stability in a high-voltage environment, significantly enhances the mechanical strength, corrosion resistance and battery life of the tab, and solves the problem of easy failure of traditional tabs.

[0009] The technical solutions adopted by the application are as follows:

[0010] A forming method of a high-safety, long-life and low-decay tab comprises the following steps:

[0011] St1: preparing modified tab rubber;

[0012] St2: pretreating a metal coil to obtain a metal substrate;

[0013] St3: respectively feeding the modified tab rubber and the metal substrate, feeding the modified tab rubber to the surface of the metal substrate, and heating and pressing the metal substrate and the modified tab rubber in an inner heating manner to obtain tab connected material;

[0014] St4: single-piece cutting the tab connected material to obtain a high-safety, long-life tab;

[0015] When the metal substrate and the modified tab rubber are heated in an inner heating manner, heat is transferred from the tab to the modified tab rubber through the contact surface, and the modified tab rubber melts outward from the contact surface.

[0016] In a preferred solution, the modified tab rubber comprises the following components by weight fraction: 40-60 parts of main body resin, 15-25 parts of plasticizer, 10-20 parts of filler, 0.5-1 part of antioxidant, and 1-3 parts of cross-linking sensitizer.

[0017] In a preferred solution, the preparation step of the modified tab rubber is as follows:

[0018] S11: pre-mixing, putting the main body resin, plasticizer, filler, antioxidant and cross-linking sensitizer into a stirring device, stirring at a speed of 200-300 r / min for 20-30 minutes until the material is uniformly translucent to obtain pre-mixed material;

[0019] S12: melt blending and granulation, transferring the pre-mixed material to a double-screw extrusion device, extruding the material from a die after melt blending, cooling into a strip through a water cooling tank, and then cutting into granules with a length by a granulator;

[0020] S13: tabletting, the granules are placed in a flat curing machine mold, heated to 150-180℃ to completely melt the granules, 5-10MPa pressure is applied, pressure is maintained for 5-10 minutes, and after cooling to room temperature, the mold is removed to obtain the tab lead wire;

[0021] S14: gamma irradiation crosslinking, the tab lead wire is placed in a cobalt-60 gamma irradiation device for radiation crosslinking treatment, and the environmental temperature is maintained at 25±5℃ during the irradiation process;

[0022] S15: post-treatment and performance stabilization, the irradiated tab lead wire is placed in a forced air drying oven for annealing treatment at a temperature of 60-80℃ for 2-4 hours to obtain the modified tab lead wire.

[0023] In a preferred embodiment, the main resin is ethylene-vinyl acetate copolymer, the plasticizer is dibutyl phthalate, the filler is nano calcium carbonate, the antioxidant is hindered phenolic antioxidant 1010, and the crosslinking sensitizer is triallyl isocyanurate.

[0024] In a preferred embodiment, in S14, the irradiation dose rate is 5-20kGy / h, and the total absorbed dose is 10-30kGy.

[0025] In a preferred embodiment, in S14, the crosslinking degree of the modified tab lead wire is ≥60%.

[0026] In a preferred embodiment, the step of pretreating the metal coil in S2 includes:

[0027] S21: longitudinally slitting the metal coil to obtain a metal wire;

[0028] S22: edge rolling the metal wire;

[0029] S23: immersing the edge-rolled metal wire in a passivation solution to perform passivation treatment on the surface of the metal wire;

[0030] S24: winding the passivated metal wire to obtain a wound metal substrate.

[0031] In a preferred embodiment, the metal coil includes a positive electrode coil and a negative electrode coil, and when the negative electrode coil is pretreated, the step before S23 further includes: performing electroplating treatment on the metal wire.

[0032] In a preferred embodiment, the passivation solution includes the following components by weight: 12-18 parts of potassium dichromate, 8-12 parts of ammonium dihydrogen phosphate, 4-7 parts of aminotri(methylene) phosphonic acid, 2-4 parts of benzotriazole, 1-3 parts of ethylenediaminetetraacetic acid, and 3-6 parts of graphene nanosheet.

[0033] In a preferred embodiment, the preparation step of the passivation solution is as follows:

[0034] Step one: add deionized water to the container, place the container on a magnetic stirrer, start stirring, and the stirring speed is 300-400 r / min;

[0035] Step two: slowly add potassium dichromate, ammonium dihydrogen phosphate and aminotri (methylene) phosphonic acid to the container in sequence, stir and dissolve, and the stirring time is 20-30 minutes;

[0036] Step three: add benzotriazole and ethylenediaminetetraacetic acid to the container, stir for 15-20 minutes, and obtain a precursor solution;

[0037] Step four: ultrasonic dispersion treatment is performed on the graphene nanosheet, the ultrasonic power is 200-300 W, the ultrasonic dispersion time is 10-15 minutes, the graphene nanosheet is uniformly dispersed in the deionized water to form a stable suspension, the suspension is slowly added to the precursor solution, and the stirring is continued for 30-40 minutes to obtain the passivation solution.

[0038] A high-safety, long-life and low-attenuation tab is prepared by the forming method of the high-safety, long-life and low-attenuation tab according to any one of the above, characterized by comprising a metal strip, the upper end and the lower end of the metal strip are respectively bonded with a first adhesive sheet and a second adhesive sheet, and the first adhesive sheet and the second adhesive sheet are bonded and connected.

[0039] The technical effects obtained by the application are as follows:

[0040] The application improves and prepares modified tab adhesive by radiation crosslinking process on tab adhesive, passivates the surface of metal substrate by passivation solution, and improves the conductivity of the tab. At the same time, the forming process is optimized by internal heating technology, so that the tab is greatly improved in three key performance indicators of tensile strength, electrolyte resistance attenuation and cycle life. The optimized tab meets the strict requirements of high-energy-density batteries on tabs, especially in extreme high-voltage environments, it exhibits excellent high-voltage resistance and cycle stability, effectively overcoming the failure problem of traditional tabs under extreme conditions. The unique formula and process design not only enhance the mechanical strength and electrolyte corrosion resistance of the tab, but also significantly improve the service life of the battery, providing solid technical support for the research and application of high-energy-density batteries. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is the structure explosion schematic diagram of the preheating unit in the embodiment one of the application;

[0042] Figure 2 is the structure schematic diagram of the tab in the embodiment two of the application;

[0043] Figure 3 is a schematic diagram of the penetration test result of the lug in Test Example 2 of the present application.

[0044] In the drawings, the components represented by the reference numbers are listed as follows:

[0045] 7, metal strip; 8, first adhesive tape; 9, second adhesive tape; 10, upper pressing block; 11, lower pressing block; 12, base material slot; 13, adhesive material avoiding slot; 14, heat insulation pressing block. DETAILED DESCRIPTION

[0046] In order to make the above objectives, features and advantages of the present application more apparent, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0047] In the following description, a lot of specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can be practiced in other manners different from those described herein, and those skilled in the art can make similar generalization without departing from the spirit and scope of the present application, therefore, the present application is not limited to the specific embodiments disclosed below.

[0048] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in a preferred embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an embodiment that is independent or alternative to other embodiments.

[0049] Thirdly, the present application is described in detail in combination with the schematic diagrams, and in the detailed description of the embodiments of the present application, the sectional view of the device structure is partially enlarged without the general proportion for the convenience of description, and the schematic diagram is only an example, which should not limit the scope of protection of the present application. In addition, the three-dimensional spatial dimensions including length, width and depth should be included in the actual manufacture.

[0050] Preparation Example

[0051] Preparation Example 1

[0052] Preparation of modified lug adhesive:

[0053] Put 53 parts of ethylene-vinyl acetate copolymer (EVA), 15 parts of dibutyl phthalate (DBP), 17 parts of nano calcium carbonate, 0.8 parts of hindered phenolic antioxidant 1010, and 2 parts of triallyl isocyanurate (TAIC) into a stirring device, stir at a speed of 300 r / min for 25 minutes, until the material is uniform and translucent, obtain a premix, transfer the premix to a twin-screw extrusion device, set the screw temperature of each zone to: 120-130℃ for the feeding section, 140-150℃ for the melting section, 150-160℃ for the homogenization section, the screw speed is 150-200 r / min, the premix is extruded from the die after melt blending, cooled into a strip through a water cooling tank (water temperature 20-25℃), and then cut into granules with a length of 2-3mm through a granulator, place the granules in a flat vulcanizing machine mold, heat to 170℃ to completely melt the granules, apply a pressure of 5MPa and keep for 10 minutes, demold after cooling to room temperature, and prepare a tab rubber wire with uniform thickness, place the tab rubber wire in a cobalt-60 gamma ray irradiation device for radiation crosslinking treatment, the irradiation dose rate is 20kGy / h, the total absorbed dose is 18kGy, the environmental temperature is maintained at 25±3℃ during the irradiation process to avoid thermal degradation of the material, until the crosslinking degree of the tab rubber wire reaches the expected value (crosslinking degree≥60%), and then place the irradiated tab rubber wire in a blast drying oven for annealing treatment at a temperature of 75℃ for 3.5 hours to eliminate internal stress and promote molecular chain relaxation, further stabilize the crosslinked structure, and obtain a modified tab rubber wire.

[0054] Here, the tab rubber wire is treated by gamma ray irradiation to promote crosslinking reaction of the high molecular chains therein, forming a more compact three-dimensional network structure, which effectively prevents the relative slipping between molecules, increases the rigidity of the material, and reduces the creep behavior; since gamma rays have strong penetrating power, they can ensure uniform irradiation of the interior of the tab rubber wire, thereby achieving uniform crosslinking effect and significantly improving the physical properties and chemical stability of the tab rubber wire, including heat resistance, chemical corrosion resistance, and mechanical strength, etc. In addition, by precisely controlling the irradiation dose rate and total absorbed dose, the crosslinking degree can be precisely controlled to meet the specific requirements of the performance of the tab rubber wire in different application scenarios.

[0055] It should be noted that, in order to ensure that the crosslinking degree of the tab rubber wire reaches the expected value, during the irradiation process, a sample can be intercepted by a mechanical hand, and the crosslinking degree of the tab rubber wire can be obtained by a nuclear magnetic resonance analyzer, of course, an online swelling test module can also be added inside the irradiation device to obtain the crosslinking degree of the tab rubber wire, wherein the nuclear magnetic resonance analyzer and the swelling test module are both existing mature applications, and their specific working principles can be referred to the existing technology, in this preparation example, as long as the crosslinking degree of the tab rubber wire can be obtained, the specific detection method is not limited.

[0056] Preparation Example Two

[0057] Preparation of passivation solution:

[0058] Into a container, 300 parts of deionized water was added, the container was placed on a magnetic stirrer, and the stirring was started with a stirring speed of 300 r / min. Then, 15 parts of potassium dichromate, 9 parts of ammonium dihydrogen phosphate, and 7 parts of aminotrimethylenephosphonic acid were slowly added into the container in sequence, and stirred for 30 minutes. Then, 3 parts of benzotriazole and 1 part of ethylenediaminetetraacetic acid were added into the container, and stirred for 20 minutes to ensure that the additives were uniformly dispersed in the solution, thereby obtaining a precursor solution. Then, 3 parts of graphene nanosheets were added into 15 parts of deionized water for ultrasonic dispersion treatment at an ultrasonic power of 200-300 W for 15 minutes, so that the graphene nanosheets were uniformly dispersed in the deionized water to form a stable suspension. The suspension was slowly added into the precursor solution, and continued to be stirred for 40 minutes, so that the graphene nanosheets were uniformly distributed in the precursor solution, thereby obtaining the passivation solution.

[0059] When the metal substrate surface is passivated by the passivation solution, the potassium dichromate can form an oxide film on the surface of the metal substrate and provide a basic framework for the subsequent reaction. The ammonium dihydrogen phosphate participates in the formation of a phosphating film, which can enhance the bonding force between the film and the substrate, and its ionic structure can promote the electron transmission to a certain extent. The aminotrimethylenephosphonic acid stabilizes the system, which can optimize the microstructure of the passivation film and make the electron transmission more smooth. The conjugated structure of benzotriazole is beneficial to the movement of electrons. The ethylenediaminetetraacetic acid can make the ion distribution on the metal surface uniform and reduce the hindrance in the process of electron transmission. In addition, the graphene nanosheets have a unique crystal structure, which is a two-dimensional carbon nanomaterial with a hexagonal honeycomb lattice structure composed of carbon atoms. The electrons have a very high mobility in the plane of the graphene nanosheets, and almost no scattering occurs during the transmission. When the graphene nanosheets are added into the passivation solution and act on the surface of the metal substrate, the graphene nanosheets will form a continuous conductive network in the passivation film, and the electrons can move quickly along these networks, greatly reducing the resistance of electron transmission, thereby significantly improving the conductivity of the tab substrate. These components and the graphene nanosheets synergistically promote the efficient transmission of electrons between the passivation film and the metal substrate, and finally greatly improve the conductivity of the tab prepared from the metal substrate.

[0060] Preparation Example Three

[0061] Pre-treatment of metal coil

[0062] The metal coil is longitudinally slitting by a slitting module to obtain a metal strip, the metal strip is edge-pressing by an edge-pressing module, the edge-pressed metal strip is immersed in a passivation solution for 30 minutes, the surface of the metal strip is passivated, the passivated metal strip is cleaned and dried to remove the residual passivation solution on the surface of the metal strip, and the metal substrate in a rolled state is obtained after drying.

[0063] It should be noted that the metal coil includes positive electrode coil and negative electrode coil, and the metal strip (for negative electrode) needs to be electroplated before passivation during the pretreatment of the negative electrode coil. In the present preparation example, the electroplating is nickel plating of the metal strip for negative electrode.

[0064] Embodiment

[0065] Embodiment one

[0066] A forming method of a high-safety, long-life and low-attenuation tab, comprising the following steps:

[0067] St1: feeding the modified tab adhesive and the metal substrate by a feeding module respectively, and feeding the modified tab adhesive to the surface of the metal substrate;

[0068] St2: heating and pressing the metal substrate and the modified tab adhesive by a pressing module in an internal heating manner to obtain a tab connected material, wherein the pressing module at least includes a preheating unit, a first hot pressing unit, a second hot pressing unit, a third hot pressing unit and a forming pressing unit, the preheating unit can preheat the metal substrate and the modified tab adhesive, the preheating temperature is 150℃, the preheating time is 5S, the modified tab adhesive is preliminarily melted by the preheating unit, and the bubbles between the metal substrate and the modified tab adhesive are removed; the heating temperature of the first hot pressing unit is 295℃, and the hot pressing time is 3S; the heating temperature of the second hot pressing unit is 295℃, and the hot pressing time is 3S; the hot pressing temperature of the third hot pressing unit is 295℃, and the hot pressing time is 2S; the forming pressing unit can physically press the metal substrate and the modified tab adhesive at room temperature, and cool and fix the shape of the metal substrate and the modified tab adhesive adhered to the surface thereof, so that the tab appearance is formed;

[0069] St4: single piece cutting the tab connected material by a slitting module to obtain a high-safety, long-life tab;

[0070] When the metal substrate and the modified tab adhesive are heated in an internal heating manner, the heat is transferred from the tab to the modified tab adhesive through the contact surface, and the modified tab adhesive melts outwardly from the contact surface.

[0071] In one specific embodiment, in the prior art, the preheating unit at least includes an upper heat-conducting block, a lower heat-conducting block and a driving member (for specific structural forms, please refer to the prior art), heating pipes are fixed between the upper heat-conducting block and the lower heat-conducting block, the heating pipes can heat the upper heat-conducting block and the lower heat-conducting block respectively after being started, and the driving member can drive the upper heat-conducting block to move in the vertical direction, so that the upper heat-conducting block and the lower heat-conducting block are attached, and through the cooperation of the upper heat-conducting block and the lower heat-conducting block, the tab rubber is melted and bonded to the surface of the metal substrate; in the embodiment, the preheating unit at least includes an upper pressing block 10 and a lower pressing block 11 (for the structural form of the lower pressing block 11, please refer to Figure 1 the drawing), heating pipes are fixed in the upper pressing block 10 and the lower pressing block 11, guide columns are fixed at both ends of the lower pressing block 11, and the upper pressing block 10 and the guide columns are slidingly connected, the heating pipes can heat the upper pressing block 10 and the lower pressing block 11 respectively after being started, wherein, base material clamping grooves 12 and rubber material avoiding grooves 13 are formed at the ends of the upper pressing block 10 and the lower pressing block 11 which are close to each other, heat insulation pressing blocks 14 are fixed in the rubber material avoiding grooves 13, the base material clamping grooves 12 are matched with the metal substrate, the heat insulation pressing blocks 14 are matched with the modified tab rubber, and heat insulation coating layers are arranged on the inner walls of the rubber material avoiding grooves 13, wherein, the material of the heat insulation pressing blocks 14 is alumina ceramic, the alumina ceramic has a low thermal conductivity and good high-temperature resistance, when the metal substrate and the modified tab rubber are pressed, the alumina ceramic heat insulation pressing blocks 14 can avoid the upper pressing block 10 and the lower pressing block 11 from transmitting to the modified tab rubber, so that the melting phenomenon of the modified tab rubber outside is avoided, specifically, the metal substrate and the modified tab rubber are fed by the feeding module, so that the metal substrate is matched with the base material clamping grooves 12 in the lower pressing block 11, and the modified tab rubber is matched with the heat insulation pressing blocks 14, when the upper pressing block 10 and the lower pressing block 11 are attached, the base material clamping grooves 12 are tightly attached with the metal substrate, the upper pressing block 10 heats the metal substrate, so that the metal substrate transmits heat to the modified tab rubber through the contact surface, the modified tab rubber starts to melt from the contact surface, and the purpose of melting the modified tab rubber from the inside to the outside is achieved, of course, in the embodiment, the preheating unit also includes other components, such as a machine table, a control module, a driving module and the like, for the specific structure and working principle, please refer to the prior art, and make adaptive adjustment according to actual needs, here, no further elaboration is made.

[0072] Through the above scheme, in the melting process of the modified tab rubber, the contact surface between the modified tab rubber and the metal substrate is preferentially melted, and has the advantages of no overflow, good heat sealing performance, anti-aging, good penetration resistance, safety and the like, further improving the safety and service life of the tab.

[0073] Further, the contact surface refers to the surface where the metal substrate and the modified tab rubber are attached to each other.

[0074] It should be noted that the feeding module, the pressing module and the slitting module can constitute an integrated forming device for continuously preparing the tab, and the feeding module, the pressing module and the slitting module are all mature applications, and their specific structures can refer to the prior art, of course, they can also be adjusted according to the actual needs, and here, no further description is made.

[0075] Example two

[0076] Please refer to Figure 2 As shown in FIG. 1, a high-safety, long-life, and low-attenuation tab is prepared by the forming method of any one of the high-safety, long-life, and low-attenuation tabs in Example One, comprising a metal strip 7, and a first adhesive sheet 8 and a second adhesive sheet 9 are respectively bonded to the upper end and the lower end of the metal strip 7, and the first adhesive sheet 8 and the second adhesive sheet 9 are bonded and connected.

[0077] Comparative example

[0078] Comparative example one

[0079] This comparative example is obtained by purchasing.

[0080] Test example

[0081] Here, all the test examples use negative tabs for testing.

[0082] Test example one

[0083] Peeling strength test

[0084] Using the tabs in Example One and the tabs in Comparative Example One, a group of samples are prepared, with a size of 50mm*50mm*0.3mm, and 5 parallel samples are tested in each group. The specific steps are as follows:

[0085] 1. Take 200ml of battery carbonate electrolyte containing 1000ppm of moisture (solvent EC:DEC=1:1, solute LiPF61mol / L), and place it in a test container;

[0086] 2. Seal 5 pieces of the tabs in Comparative Example One and 5 pieces of the tabs in Example One, with a size of 100mm*10mm*0.5mm, in the container;

[0087] 3. Place the container in an 85℃ air drying oven, and continuously store for 24 hours, with the temperature fluctuation in the oven being ≤±1℃;

[0088] 4. After 24 hours, wash the tabs with clean water and dry them with degreasing gauze;

[0089] 5. After peeling off one side of the tab adhesive, use a tensile testing machine to clamp the peeled position and reverse the other side by 180° to peel off the tab adhesive from the conductor;

[0090] 6. The tensile speed is 20 mm / min, the interface of 10-20 mm reserved at the other end is not peeled (the test should be completed within 1 h after the sample is washed), and the peeling strength of the sample is calculated. The test results are shown in Table 1.

[0091] Table 1:

[0092]

[0093] As can be seen from Table 1, the peeling strength of the tab prepared in Example 1 is increased by 25% compared with the commercially available tab, reaching 2.5 MPa, which is much higher than 2.0 MPa of the tab in Comparative Example 1. The increase in tensile force is mainly due to the radiation crosslinking process of the tab adhesive and the surface metal-plated layer treatment, which significantly enhances the interfacial adhesion between the tab adhesive and the metal substrate, effectively reducing the risk of tab delamination under high-temperature electrolyte corrosion.

[0094] Test Example 2

[0095] Penetration test

[0096] The specific steps are as follows:

[0097] 1. Take 200 ml of battery carbonate electrolyte containing 1000 ppm of moisture (solvent EC:DEC = 1:1, solute LiPF61 mol / L), and load it into the test container;

[0098] 2. Take 5 pieces of the tab in Comparative Example 1 and 5 pieces of the tab in Example 1, each with a size of 100 mm*10 mm*0.5 mm, and seal them together in the container;

[0099] 3. Place the container in an 85°C air-drying oven, and maintain the temperature fluctuation in the oven within ≤±1°C during the period;

[0100] 4. At the time points of 24 hours, 10 days, 20 days, 30 days, and 40 days, respectively, take out one sample of Example 1 and one sample of Comparative Example 1, wash the surface electrolyte with clean water, and then wipe the surface of the tab with a water-absorbing cloth;

[0101] 5. Air dry for 12 hours, and observe the tab adhesive and the conductor every 2 hours during the period to see if there is any peeling or delamination;

[0102] 6. After air drying for 12 hours, immerse the test tab in the penetrant for 30 minutes;

[0103] 7. After soaking, rinse the surface of the tab with clean water and wipe it dry with a water-absorbing cloth;

[0104] 8. Observe and measure the penetration between the tab adhesive and the metal substrate under a microprojector, and the test data are shown in Table 2.

[0105] Table II

[0106]

[0107] Table II and the accompanying Figure 3 It can be seen that, in the process of penetration test, the tab of Preparation Example One exhibits significantly better anti-penetration performance than that of Comparative Example One. The tab of Preparation Example One can ensure stable and close bonding between the tab adhesive and the metal substrate, and even under the harsh conditions of long-term high temperature and electrolyte immersion, there is no phenomenon of penetrating penetration. In contrast, the tab of Comparative Example One has penetration on the 10th day of the test, and the penetration width gradually increases over time, and by the 40th day, the tab adhesive and the metal substrate have been separated, which fully illustrates that the tab preparation method of the present application can significantly improve the anti-penetration performance of the tab, thereby prolonging the service life of the battery and enhancing the safety of the battery.

[0108] It should be noted that in this embodiment, the criterion for judging the failure of the tab product is that the penetration width is greater than or equal to 500 μm, i.e. the tab fails after the penetration width is greater than or equal to 500 μm. The specific product failure criterion can be adjusted according to actual use requirements, which does not constitute a specific limitation here.

[0109] Test Example Three

[0110] Electrolyte attenuation test (simulating high temperature corrosion environment of battery)

[0111] Take 200 ml of carbonic acid ester electrolyte for battery containing 1000 ppm of moisture (solvent EC:DEC=1:1, solute LiPF61 mol / L), and put it into the test container. Take 5 pieces of the tab of Comparative Example One and 5 pieces of the tab of Example One, each with a size of 50 mm*10 mm*0.5 mm, and seal them together in the container. Put the container into an 85°C air drying oven and store it for 28 days, keeping the temperature fluctuation in the oven ≤±1°C during the period. After 28 days, take out the sample, wash the surface electrolyte with clean water, and after drying, measure the peel strength between the tab adhesive and the metal conductor according to the steps in Test Example One, and calculate the tensile force attenuation rate according to the following formula:

[0112] The test results are shown in Table III.

[0113] Table III

[0114]

[0115] As can be seen from Table II, the tab in Comparative Example I has a tensile force decay rate of 55% in a high-temperature electrolyte environment, while the tab in Example I has a decay rate of only 8%, which is far below the target value of 10%. The core reason for the slowed decay is the synergistic effect of the antioxidant (hindered phenol 1010) and the crosslinking sensitizer (TAIC) in the tab adhesive, which inhibits the erosion of the molecular chain by HF in the electrolyte. Meanwhile, the dense film layer formed by the passivation solution (conductive enhancement system containing graphene nanosheets) effectively blocks the penetration of the electrolyte, thereby improving the chemical corrosion resistance of the tab.

[0116] Test Example Four

[0117] Battery capacity cycle test (high voltage system)

[0118] Soft pack batteries were prepared using the tabs in Comparative Example I and Example I, respectively. The positive electrode material was preferably NCM811, the negative electrode material was preferably graphite, the electrolyte was preferably LiPF6 electrolyte containing 10% FEC (high voltage resistant), the capacity of the battery was 5 Ah, the voltage range was 3.0-4.35 V, and the test was carried out in an environment of 25±2°C. The battery was charged at 0.5C constant current to 4.5V, the cutoff current was 0.05C, and discharged at 1C constant current to 3.0V. The capacity retention rate and appearance state were recorded every 100 cycles, and the test data were recorded. The results are shown in Table IV.

[0119] Table IV:

[0120]

[0121] Battery capacity cycle test (ultra-high voltage system)

[0122] Soft pack batteries were prepared using the tabs in Comparative Example I and Example I, respectively. The positive electrode material was preferably high-nickel lithium-rich manganese-based material (LiNi05Mn03Co02O2), the negative electrode material was preferably graphite, the electrolyte was preferably high-voltage electrolyte containing 2% VC, the capacity of the battery was 5 Ah, the voltage range was 3.0-4.8 V, and the test was carried out in an environment of 45±2°C. The battery was charged at 0.3C constant current to 4.8V, the cutoff current was 0.05C, and discharged at 0.5C constant current to 3.0V. The capacity retention rate and appearance state were recorded every 100 cycles, and the test data were recorded. The test was carried out until the battery capacity was close to 0 mAh or safety failure occurred. The results are shown in Table V.

[0123] Table V:

[0124]

[0125] As can be seen from Table 3 and Table 4, in the high-voltage system, the tab in Example 1 improves the cycle life of the battery cell to more than 6000 times, which is mainly due to the low creep property of the tab adhesive (irradiation crosslinking degree ≥ 60%) and the conductive enhanced network of the passivation film (graphene nanosheet constructed electronic channel), reducing the stress concentration and contact resistance increase of the tab and the interface of the battery cell during the cycle; in the super high-voltage system, the tab in Comparative Example 1 fails after 300 cycles due to the insufficient oxidation resistance of the passivation film, while the tab in Example 1 forms a composite film layer with conductivity and high pressure resistance through the synergistic effect of benzotriazole (corrosion inhibitor) in the passivation solution and graphene, so that the battery cell remains structurally intact after 1600 cycles without bulging and liquid leakage, significantly improving the safety and life of the battery under extreme conditions.

[0126] In summary, the test results show that in Example 1, by improving the tab adhesive formula (using radiation crosslinking process), passivation solution composition (adding graphene conductive enhancer) and molding process (applying internal heating technology), the prepared tab significantly exceeds the traditional tab in three key performance indicators of tensile strength, electrolyte resistance and cycle life. The tab meets the strict requirements of high energy density batteries for tabs, especially in extreme high voltage environments, it exhibits excellent high pressure resistance and cycle stability, effectively overcoming the problem of easy failure of traditional tabs under extreme conditions. The unique formula and process design not only enhance the mechanical strength and electrolyte corrosion resistance of the tab, but also significantly improve the service life of the battery, providing solid technical support for the research and application of high energy density batteries. In addition, the production process of the tab is simple and easy to realize large-scale industrial production, indicating that it has great market potential and application prospect.

[0127] The above is only the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can make several improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application. The structures, devices and operation methods not specifically described and explained in the present application, such as no special description and limitation, are implemented according to the conventional means in the art.

Claims

1. A method for forming a tab with high safety, long life, and low attenuation, the method comprising: The method comprises the following steps: ​ St1: preparing modified tab adhesive, the modified tab adhesive comprises the following components by weight fraction: main resin 40-60 parts, plasticizer 15-25 parts, filler 10-20 parts, antioxidant 0.5-1 part, crosslinking sensitizer 1-3 parts; St2: pretreating the metal coil to obtain a metal base material, the steps comprising: S21: longitudinally slitting the metal coil to obtain a metal wire; S22: edge rolling the metal wire; S23: immersing the edge-rolled metal wire in a passivation solution to perform passivation treatment on the surface of the metal wire, the passivation solution comprising the following components by weight: potassium dichromate 12-18 parts, ammonium dihydrogen phosphate 8-12 parts, aminotri (methylene) phosphonic acid 4-7 parts, benzotriazole 2-4 parts, ethylenediaminetetraacetic acid 1-3 parts, and graphene nanosheet 3-6 parts; S24: winding the passivated metal wire to obtain a wound metal base material; St3: respectively feeding the modified tab adhesive and the metal base material, feeding the modified tab adhesive to the surface of the metal base material, and heating and pressing the metal base material and the modified tab adhesive in an internal heating manner to obtain a tab connected material; St4: single-piece cutting the tab connected material to obtain a high-safety and long-life tab; When the metal base material and the modified tab adhesive are heated in an internal heating manner, heat is transferred from the tab to the modified tab adhesive through the contact surface, and the modified tab adhesive melts outward from the contact surface.

2. The tab forming method of claim 1, wherein the tab forming method is a method of forming a tab having high safety, long life, and low attenuation. The preparation steps of the modified tab adhesive are as follows: S11: putting the main resin, plasticizer, filler, antioxidant, and crosslinking sensitizer into a stirring device, and stirring at a speed of 200-300 r / min for 20-30 minutes to obtain a premix; S12: transferring the premix to a double-screw extrusion device, melting and blending the material, and then extruding from a die, cooling into a strip through a water cooling tank, and then cutting into granules through a granulator; S13: placing the granules in a flat vulcanizing machine mold, heating to 150-180°C to completely melt the granules, applying a pressure of 5-10 MPa, and maintaining the pressure for 5-10 minutes, then demolding after cooling to room temperature to obtain a tab adhesive wire; S14: placing the tab adhesive wire in a cobalt-60 gamma ray irradiation device for radiation crosslinking treatment at an ambient temperature of 25±5°C; S15: placing the irradiated tab adhesive wire in a blast drying oven for annealing treatment at a temperature of 60-80°C for 2-4 hours to obtain a modified tab adhesive.

3. The tab forming method of claim 2, wherein the tab forming method is characterized by: In S14, the irradiation dose rate is 5-20 kGy / h, and the total absorbed dose is 10-30 kGy.

4. The tab forming method of claim 2, wherein the tab forming method is characterized by: In S14, the crosslinking degree of the modified tab adhesive is ≥60%.

5. The tab forming method of claim 1, wherein the tab forming method is characterized by: The metal coil comprises a positive electrode coil and a negative electrode coil, and when the negative electrode coil is pretreated, the steps before S23 further comprise: performing electroplating treatment on the metal wire.

6. The tab forming method of claim 1, wherein the tab forming method is a method of forming a tab having high safety, long life, and low attenuation. The preparation steps of the passivation solution are as follows: Step one: adding deionized water to a container, placing the container on a magnetic stirrer, and starting stirring at a speed of 300-400 r / min; Step two: slowly add potassium dichromate, ammonium dihydrogen phosphate, aminotri methylene phosphonic acid into the container in turn, stir and dissolve, and stir for 20-30 minutes; Step three: add benzotriazole and ethylenediaminetetraacetic acid into the container again, stir for 15-20 minutes, and obtain a precursor solution; Step four: perform ultrasonic dispersion treatment on the graphene nanosheet, so that the graphene nanosheet is uniformly dispersed in deionized water to form a stable suspension, slowly add the suspension into the precursor solution, continue to stir for 30-40 minutes, and obtain a passivation chemical solution.

7. A high-safety, long-life, low-attenuation tab prepared by the high-safety, long-life, low-attenuation tab forming method according to any one of claims 1 to 6, characterized by: The metal belt (7) has a first adhesive sheet (8) and a second adhesive sheet (9) bonded to the upper end and the lower end of the metal belt (7) respectively, and the first adhesive sheet (8) and the second adhesive sheet (9) are bonded and connected.

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