Tab for a full-eared cell and a method of making the same

Abstract

This invention discloses an electrode sheet for all-tab battery cells and its preparation method, belonging to the field of lithium-ion battery manufacturing technology. The electrode sheet of this invention features a transition reinforcement band with a width of 0.5–2.0 mm between the coated area and the blank area. The binder content in this band is 2–4 times that of the coated area, and the conductive agent content is 5–10 times that of the coated area. Optional addition of 3%–8% nano-ceramic powder forms a three-zone gradient structure: "coated area—transition reinforcement band—blank area". A dual-chamber, zoned feeding slit die is used for synchronous coating. After gradient drying and zoned rolling, the resulting electrode sheet utilizes the mechanical gradient of the transition reinforcement band to disperse and flatten stress, reducing the short-circuit rate by 50%–70%. A multi-dimensional thermally conductive network is constructed using a high-conductivity agent and nano-ceramic powder, increasing the welding pull-out force by 30%–50% and reducing the contact resistance by more than 70%, exhibiting fundamental differences and significant advantages compared to boehmite coatings. This invention is applicable to the large-scale production of 4680 and other all-tab cylindrical batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery manufacturing technology, specifically relating to an electrode sheet for a multi-tab battery cell and its preparation method. Background Technology

[0002] Lithium-ion batteries, as high-energy-density energy storage devices, have been widely used in new energy vehicles, energy storage systems, and consumer electronics. In recent years, the 46-series large cylindrical batteries, represented by the 4680, have become a hot topic in industry research due to their advantages such as high single-cell energy density, high power output, and short heat dissipation path. One of the core technical features of the 4680 battery is its use of a full-tab (or tabless) structure, where the entire current collector edge serves as the current transmission interface. The full tabs at both ends of the core are shaped and flattened into a plane through a flattening process, and then laser-welded to the current collector plate, thus enabling the entire current collector edge to simultaneously serve as a current transmission channel. However, the introduction of the full-tab structure also brings new technological challenges: In conventional electrodes, the coated area and the uncoated area form abrupt property interface: the coated area is thick (100-200 μm), while the uncoated area is only 6-12 μm of bare foil. During flattening, mechanical stress is highly concentrated at this abrupt interface, easily leading to fatigue fracture at the root of the uncoated area. Simultaneously, the edges of the coated area experience powdering and warping due to stress transmission, generating metal debris or active particles, which can then cause internal short circuits. In subsequent laser welding processes, the heat generated during welding is conducted along the bare foil in the uncoated area to the coated area, easily causing thermal failure of the active material in the coated area. When laser heat is applied instantaneously, the poor thermal conductivity of the bare foil area makes it easy for heat to concentrate, leading to weld perforation, causing short circuits, reducing weld pull-out force, and compromising the long-term cycle reliability of the cell.

[0003] To improve the edge processing performance of electrode sheets, existing technologies have proposed a boehmite (γ-AlOOH) edge coating scheme to prevent diaphragm puncture by filling cutting burrs. However, this scheme has the following limitations: ① Insufficient mechanical properties: Boehmite coatings have poor tensile toughness and are prone to generating dust, burrs, or molten beads during processing; ② Functional mismatch: It aims for electrical insulation (volume resistivity > 10¹² Ω·cm), while the flattened area of ​​the full electrode tab requires good conductivity to reduce the contact resistance with the current collector; ③ Weak thermal conductivity: The thermal conductivity is only 1~5 W / m·K, which cannot provide rapid lateral heat dissipation during laser welding and instead aggravates damage to the heat-affected zone; ④ Abrupt interface: There is also an interface with abrupt changes in physical properties between the coating area and the coating area, and the stress concentration problem during flattening is not alleviated; In summary, there is an urgent need to develop an electrode edge reinforcement structure that combines mechanical support, thermal management, and low contact resistance to fundamentally solve the above problems at the electrode structure level. Summary of the Invention

[0004] This invention mainly provides an electrode sheet for a multi-tab battery cell and its preparation method, in order to solve the following technical problems existing in the prior art: First, it addresses the stress concentration problem caused by the abrupt change in the physical properties of the interface between the coated area and the blank area during the flattening process of conventional electrodes in the 4680 full tab. This stress concentration can easily cause the root of the blank area to break, the edge of the coated area to peel off powder and curl up, which in turn can lead to short circuit failure.

[0005] Secondly, it addresses the issue that during the laser welding process of conventional electrode sheets on the current collector, when the laser heat is applied instantaneously, the bare foil area has poor thermal conductivity, causing the heat to concentrate at a single point, which leads to weld perforation, short circuit, reduced welding pull-out force, and decreased long-term cycle reliability of the battery cell.

[0006] Third, it addresses the problem that existing boehm edge coatings, due to their functional positioning as electrical insulation, low thermal conductivity, and poor tensile toughness, cannot simultaneously meet the mechanical support requirements of the full tab flattening process, the thermal management requirements of the laser welding process, and the low contact resistance requirements of the tab root.

[0007] To achieve the above objectives, the present invention provides an electrode sheet for a multi-tab battery cell, comprising: a current collector, a coating area, a transition reinforcement band, and a blank area; For current collectors, aluminum foil is commonly used for the positive electrode and copper foil is commonly used for the negative electrode; The coating area is coated on the surface of the positive and negative current collectors, and the coating area includes an active material layer formed by drying a conventional active slurry; The blank area, located at the edge of the current collector, is a bare foil area without any slurry coating, which is used for subsequent flattening to form a full electrode tab; A transition reinforcement strip is applied between the coated area and the blank area, naturally connecting with the coated area and directly adjacent to the blank area; The width of the blank area is 3-15 mm, the width of the transition reinforcement band is 0.5-2.0 mm, and its thickness gradually decreases from the coating area side to the blank area side. Its binder content is 2-4 times that of the coating area binder content, and its conductive agent content is 5-10 times that of the coating area conductive agent content. The transition reinforcement band, coating area and blank area together constitute a three-zone gradient structure of "coating area - transition reinforcement band - blank area", so that the mechanical strength, thickness and conductivity of the electrode sheet transition from the coating area to the blank area in a gradient.

[0008] Preferably, the dry film thickness of the transition reinforcement band is 20% to 60% of the dry film thickness of the coating area.

[0009] Preferably, the transition reinforcement band further comprises nano-ceramic powder, wherein the nano-ceramic powder is selected from alumina ( ), silicon dioxide ( Titanium dioxide () Zirconia ( ), magnesium oxide ( ), zinc oxide ( ), cerium oxide ( ), iron oxide ( ), aluminum nitride ( Boron nitride ( Titanium nitride ( One or more of the following are used: the nano-ceramic powder has a particle size of 50–300 nm and is added at an amount of 3%–8% of the total solid content of the transition reinforcement slurry. The nano-ceramic powder and the conductive agent in the transition reinforcement zone together form a multidimensional thermally conductive network, and the thermal conductivity of the thermally conductive network is 20–50 W / m·K.

[0010] To achieve the above objectives, the present invention also provides a method for preparing the above-mentioned electrode sheet, comprising the following steps: S1: Prepare conventional positive and negative electrode active slurries and transition reinforcement slurries. The conventional positive and negative electrode active slurries include active materials, conductive agents, binders, aqueous solvents, and oil-based solvents. The transition reinforcement slurry includes binders, conductive agents, solvents, and optional active materials and / or nano-ceramic powders. The binder content in the transition reinforcement slurry is 2 to 4 times that in the conventional active slurry, and the conductive agent content is 5 to 10 times that in the conventional active slurry. S2: A dual-chamber partitioned feeding slit die is used for synchronous coating. The die has a first chamber and a second chamber separated by an adjustable shim partition. The first chamber contains conventional active slurry, and the second chamber contains transition reinforcement slurry. The coating substrate is controlled to move at a speed of 2 to 50 m / min, so that the conventional active slurry is extruded from the first chamber to form the coating area, and the transition reinforcement slurry is extruded from the second chamber to form the transition reinforcement band. The transition reinforcement band is located between the coating area and the preset blank area. There is a natural mixing area between the two slurries at the interface, and its width is less than 0.2 mm. The coating area and the transition reinforcement band are seamlessly connected. S3: Drying. The coated electrode is sent into a multi-temperature zone oven for gradient drying. The electrode is kept in the low temperature zone at 60-80℃ for 3-5 minutes to match the drying rate of the transition reinforcement zone and the coating zone and prevent interface cracking. S4: Roll pressing to obtain an electrode sheet with a three-zone gradient structure.

[0011] Preferably, the conductive agent in S1 is selected from one or more of Super P, C45, C65, acetylene black, artificial graphite, natural graphite, carbon nanotubes (CNT), and graphene; the aqueous solvent is deionized water; the oil solvent is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO); and the transitional reinforcing slurry binder is selected from one or more of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVF), polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FRP), soluble polytetrafluoroethylene (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-tetrachloroethylene copolymer (ETFE), polyimide resin (PI), styrene-butadiene rubber, polyamide, polyterephthalic acid, their derivatives, their crosslinks, and their copolymers.

[0012] Preferably, the preparation of the transition-reinforced slurry in step S1 includes the following steps: Take a binder, an oil-based solvent, a conductive agent, an optional active material, and / or nano-ceramic powder, wherein the mass ratio of the binder, oil-based solvent, conductive agent, active material, and nano-ceramic powder is (3-10):(20-30):(5-15):(30-60):(2-8). At room temperature, add the binder and solvent to a mixer and disperse at high speed for 2-5 hours to obtain a slurry. Then add the conductive agent and continue high-speed dispersion for 1 hour. Finally, add the active material and nano-ceramic powder at the same time, appropriately reduce the dispersion speed of the mixer, and continue stirring for 1-3 hours to obtain a transition-reinforced slurry.

[0013] Preferably, in the drying step S3, after the low temperature zone, there is a medium temperature zone of 90-110°C and 4-6 m in length, and a high temperature zone of 120-140°C and 2-4 m in length.

[0014] Preferably, in the rolling step S4, the compaction density difference between the transition reinforcement zone and the coating zone is controlled by partitioned rolling to ensure that the difference is ≤0.2 g / cm³.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. Stress dispersion and short-circuit rate reduction during the kneading process. This invention creates a three-zone gradient structure of "coated area – transition reinforcement zone – blank area" by setting a transition reinforcement zone between the coated area and the blank area, covering the root of the flattened area (the blank area is closer to the coated area). In this structure, the thickness and modulus of the transition reinforcement zone are between those of the coated area and the blank area, changing the mechanical stress during flattening from "point concentration" in conventional electrode sheets to "surface dispersion," avoiding high stress concentration at a single interface. Experimental results show that using the electrode sheet of this invention reduces the short-circuit rate of the entire electrode tab by 50% to 70% during flattening.

[0016] 2. Reduce the burn-through rate and increase the pull-out force in laser welding processes. In this invention, the high content of conductive agent (10-20 wt%) in the transition reinforcement band, combined with optional nano-ceramic powder (3-8 wt%), synergistically forms a multi-dimensional thermally conductive network with a thermal conductivity of 20-50 W / m·K. During laser welding, this network rapidly diffuses welding heat laterally, preventing laser heat from concentrating at a single point and reducing the probability of weld perforation. Simultaneously, the high binder content (8-15 wt%) in the transition reinforcement band provides strong adhesion and mechanical support, constraining thermal deformation and vibration in the bare foil area during welding. This synergistic effect increases the weld pull-out force by 30%-50% compared to electrodes without a transition band, and changes the failure mode from "coating-foil interface peeling" to "weld body tearing," significantly enhancing welding reliability.

[0017] 3. Reduce the contact resistance at the root of the electrode tab. The conductive agent content in the transition reinforcement zone of this invention is 5 to 10 times that of the conventional coating zone, and a three-dimensional continuous conductive network is constructed at the root of the flattened zone. This network reduces the contact resistance at the root of the tab by 80% to 90%.

[0018] 4. The essential differences and technological advantages compared to existing boehmite coatings The transition reinforcement zone of this invention differs fundamentally from existing boehm edge coatings in terms of functional positioning, material composition, and technical effects. Its technical advantages are compared below: In summary, this invention, through the design of a three-zone gradient structure of "coating zone - transition reinforcement zone - blank zone" and the use of a dual-chamber partitioned feeding slit die head to achieve integrated fabrication, simultaneously meets the mechanical support requirements of the full tab flattening process, the thermal management requirements of the laser welding process, and the low contact resistance requirements of the tab root. It significantly reduces the flattening short-circuit rate and improves the welding pull-out force, and has essential differences and significant technical advantages compared with existing boehmite coating solutions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the all-electrode electrode plate provided by the present invention; Figure 2 This is a schematic diagram showing the completed winding of the full-tie electrode sheet provided by the present invention; Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0021] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0022] Example 1: Omnipolar battery cell with transition enhancement band I. Preparation of the positive electrode sheet (1) Conventional active slurry (coating area) The following materials were prepared: 96.0 wt% NCM811 cathode material (D50=12μm), 2.0 wt% Super P conductive agent, 0.5 wt% carbon nanotubes (CNTs, 10nm in diameter, 10μm in length), and 1.5 wt% PVDF (HSV900) binder. NMP was used as the solvent, and the solid content was 68%. Preparation method: PVDF was pre-dissolved in NMP to prepare an 8% gel solution. The conductive agent was added and dispersed for 1 hour. Finally, NCM811 was added and dispersed at high speed for 2 hours to obtain a conventional active slurry with a viscosity of (…). The value is 5500 cP.

[0023] (2) Transition reinforcement slurry (transition zone) The following components (by total mass percentage of slurry) are used: PVDF binder 12 wt%, conductive agent (CNT:SuperP=1:3) 15 wt%, nano- (Particle size 100nm) 6 wt%, active material NCM811 42 wt%, NMP solvent 25 wt%. Preparation method: PVDF and NMP are dispersed at high speed in a mixer at room temperature for 3 hours to obtain a gel solution. A conductive agent is added and dispersion at high speed is continued for 1 hour. Then, nanoparticles are added simultaneously. Mix with NCM811, reduce the stirring speed and stir for 2.5 hours to obtain a transition-reinforced slurry with a viscosity of ( The value is 1800 cP.

[0024] (3) Coating, drying and rolling A dual-chamber, zoned-feed slit die was used, with 13μm aluminum foil as the current collector, and a coating speed of 30 m / min. Conventional active slurry was extruded to form the coating zone, while transition reinforcement slurry was extruded to form a transition reinforcement band (1.2mm wide, covering the root of the blank area) located between the coating zone and the pre-defined blank area. The wet film thickness of the coating zone was 180μm, and the wet film thickness of the transition band was 45μm. The coated electrode was then placed in a three-temperature zone oven: low temperature zone 70℃, 4m; medium temperature zone 100℃, 5m; and high temperature zone 130℃, 3m. After drying, the dry film thickness of the coating zone was 120μm, and the dry film thickness of the transition band was 32μm. During rolling, the compaction density difference between the transition band and the coating zone was controlled to be ≤0.2 g / cm³, resulting in the positive electrode.

[0025] II. Preparation of the negative electrode sheet (1) Conventional active slurry (coating area) The following components were used: 95.5 wt% artificial graphite (D50=15μm), 1.5 wt% conductive agent Super P, 0.5 wt% CNT, 2.0 wt% binder SBR, and 0.5 wt% thickener CMC. Deionized water was used as the solvent, and the solid content was 52%. Preparation method: CMC was pre-dissolved in water to prepare a 2% adhesive solution. The conductive agent was added and dispersed for 1 hour, followed by the graphite and dispersion for 2 hours. Finally, the SBR emulsion was added and stirred at low speed for 30 minutes to obtain a conventional active slurry with a viscosity of (…). The value is 4000 cP.

[0026] (2) Transition reinforcement slurry (transition zone) The following components (by total mass percentage of slurry) were prepared: 10 wt% PAA (polyacrylic acid, molecular weight 450,000) binder, 18 wt% conductive agent (CNT:Super P=1:4), 5 wt% nano-BN (80 nm particle size), 39 wt% artificial graphite active material, and 28 wt% deionized water. Preparation method: PAA was dissolved in water and stirred for 2 hours to obtain a slurry. The conductive agent was added and dispersed for 1 hour. Then, nano-BN and graphite were added and stirred at low speed for 2 hours to obtain a transition-reinforced slurry with a solid content of 45% and a viscosity (100s⁻¹) of 1500 cP.

[0027] (3) Coating, drying and rolling Using 6μm copper foil as the current collector, the coating speed was 25 m / min, the wet film thickness in the coated area was 160μm, and the wet film thickness in the transition zone was 40μm. Drying conditions were the same as for the positive electrode. Rolling: The compaction density difference between the transition zone and the coated area was controlled to ≤0.2 g / cm³ to obtain the negative electrode sheet.

[0028] III. Rolling and Kneading The aforementioned positive and negative electrode sheets (both with transition reinforcement bands) were wound together with the separator (ceramic-coated PE, 12μm thick) according to the specifications of a 4680 large cylindrical battery. The result is as follows. Figure 2 As shown. The positive electrode is 3.5m long, the negative electrode is 3.8m long, and the separator is slightly wider than the electrode. After winding, the two ends of the cell are flattened using a flattening roller (3000rpm, 0.3MPa, 5s) to press the blank areas at both ends into a dense plane. After flattening, the insulation resistance of the cell is tested to calculate the short-circuit rate. 50 cells are prepared for each example.

[0029] IV. Laser Welding of Manifold The flattened end face of the battery cell was laser-welded to the current collector. Welding parameters: fiber laser, power 800W, pulse width 8ms, spot diameter 0.4mm, welding speed 50mm / s. After welding, 10 battery cells were randomly selected for pull-out force testing.

[0030] Example 2: Transition reinforcement zone without nano-ceramic powder The only difference between this embodiment and Example 1 is that no nano-ceramic powder is added to the transition reinforcement slurries for both the positive and negative electrodes. Specifically, the positive electrode transition reinforcement slurry formulation is: PVDF 12 wt%, conductive agent 15 wt%, NCM811 48 wt%, NMP 25 wt%; the negative electrode transition reinforcement slurry formulation is: PAA 10 wt%, conductive agent 18 wt%, artificial graphite 44 wt%, deionized water 28 wt%. All other coating, drying, rolling, winding, leveling, and welding parameters are the same as in Example 1.

[0031] Comparative Example 1: Conventional Electrode The same conventional active slurry as in Example 1 was used, but a standard single-chamber die was used for coating, and no transition reinforcement band was provided. Both the positive and negative electrode sheets consisted only of coated areas and blank areas, and they were directly adjacent to each other. The drying and rolling parameters were the same as in Example 1. The winding, leveling, and welding parameters were the same as in Example 1.

[0032] Comparative Example 2: Electrode with edge-coated boehmite coating First, the coated area is obtained by coating with the conventional active slurry as in Example 1. Then, a second coating is applied to the blank area of ​​the positive electrode sheet near the edge (1.5 mm wide) of the coated area, using boehmite slurry. The boehmite slurry formulation (mass percentage): boehmite (γ-AlOOH) 85 wt%, PVDF 10 wt%, Super P 5 wt%, solid content 45%. The negative electrode sheet is not coated with boehmite (boehmite is usually only used for the positive electrode). After coating, drying and rolling are performed using the same parameters as in Example 1. Winding, smoothing, and welding parameters are the same as in Example 1.

[0033] Test methods and results Test items and standards: Short circuit rate after flattening: For each group of 50 cells, after flattening, use a 500V megohmmeter to test the insulation resistance, record the number of cells with a resistance <20MΩ, and calculate the short circuit rate.

[0034] Laser welding pull-out force: 10 cells (after flattening and welding) are randomly selected from each group, and the current collector is pulled out axially using a universal tensile testing machine. The maximum force (N) at the time of breakage is recorded and the average value is taken.

[0035] Powder shedding rate in the coated area after welding: After welding, the powder is collected by tape at the edge of the coated area of ​​the battery cell (within 2mm of the weld), and the weight is used to calculate the percentage of powder shedding relative to the total mass of the active layer in that area.

[0036] Contact resistance at the base of the tab: After disassembling and flattening the battery cell, the base of the blank area (0.5mm from the edge of the coated area) is brought into contact with a copper probe, and the contact resistance (mΩ·cm²) is measured using the four-probe method.

[0037] Transition zone thermal conductivity: The transition reinforcement slurry was coated separately on the aluminum foil (thickness of about 30 μm), and after drying, the in-plane thermal conductivity was measured by laser scintillation method (LFA 467).

[0038] Test Results Summary Comparative Example 2: The boehmite coating is an insulator. The contact resistance measurement value is the data of the coating surface. After smoothing, the coating may partially peel off. This is for reference only.

[0039] Comparing Comparative Example 1 and Example 1, it can be seen that the transition reinforcement strip of the present invention reduces the flattening short-circuit rate from 12% to 2%, increases the weld pull-out force from 28.5N to 49.2N, and reduces the contact resistance by approximately 73%. Comparing Comparative Example 2 (boehmite coating) and Example 1, the thermal conductivity of the present invention (32.6 W / m·K) is much higher than that of boehmite (3.2 W / m·K), the weld pull-out force is increased by approximately 58%, and the powdering rate is reduced by 90%. Comparing Example 2 (without ceramic) and Example 1 (with...)... After adding nano-ceramic powder, the thermal conductivity increased from 18.5 W / m·K to 32.6 W / m·K, and the welding pull-out force further increased from 43.6 N to 49.2 N, demonstrating the synergistic effect of nano-ceramic powder in thermal management. In summary, the transition reinforcement strip scheme proposed in this invention can effectively improve the short-circuit failure rate of the all-tab and the yield rate of laser welding of the current collector, significantly improve the welding strength of the current collector, reduce contact resistance, and has high industrial practical value.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered to be within the protection scope of the present invention.

Claims

1. An electrode sheet for a multi-tab battery cell, characterized in that, include: Current collector, coating area, transition reinforcement zone, blank area; For current collectors, aluminum foil is commonly used for the positive electrode and copper foil is commonly used for the negative electrode; The coating area (1) is coated on the surface of the positive and negative current collectors, and the coating area includes an active material layer formed by drying a conventional active slurry; The blank area (3) is located at the edge of the current collector and is a bare foil area without any slurry coating, which is used for subsequent flattening to form a full electrode tab; A transition reinforcement band (2) is applied between the coated area and the blank area, naturally connecting with the coated area and directly adjacent to the blank area; The width of the blank area (3) is 3 to 15 mm, the width of the transition reinforcement band (2) is 0.5 to 2.0 mm, and its thickness gradually decreases from the coating area (1) side to the blank area side. Its adhesive content is 2 to 4 times that of the coating area adhesive content, and its conductive agent content is 5 to 10 times that of the coating area conductive agent content. The transition reinforcement band (2), the coating area (1) and the blank area (3) together constitute a three-zone gradient structure of "coating area - transition reinforcement band - blank area", so that the mechanical strength, thickness and conductivity of the electrode sheet from the coating area (1) to the blank area (3) are gradient transition.

2. The electrode sheet for a multi-tab battery cell according to claim 1, characterized in that, The dry film thickness of the transition reinforcement band (2) is 20% to 60% of the dry film thickness of the coating area.

3. The electrode sheet for a multi-tab battery cell according to claim 1, characterized in that, The transition reinforcement band (2) further comprises nano-ceramic powder, which is selected from alumina ( ), silicon dioxide ( Titanium dioxide () Zirconia ( ), magnesium oxide ( ), zinc oxide ( ), cerium oxide ( ), iron oxide ( ), aluminum nitride ( Boron nitride ( Titanium nitride ( One or more of the following, with a particle size of 50 to 300 nm, are added at an amount of 3% to 8% of the total solid content of the transitional reinforced slurry.

4. The electrode sheet for a multi-tab battery cell according to claim 3, characterized in that, The nano-ceramic powder and the conductive agent in the transition reinforcement band (2) together form a multidimensional thermal conductive network with a thermal conductivity of 20 to 50 W / m·K.

5. A method for preparing an electrode sheet for a multi-tab battery cell as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Prepare conventional positive and negative electrode active slurries and transition reinforcement slurries. The conventional positive and negative electrode active slurries include active materials, conductive agents, binders, aqueous solvents, and oil-based solvents. The transition reinforcement slurry includes binders, conductive agents, solvents, and optional active materials and / or nano-ceramic powders. The binder content in the transition reinforcement slurry is 2 to 4 times that in the conventional active slurry, and the conductive agent content is 5 to 10 times that in the conventional active slurry. S2: A dual-chamber partitioned feeding slit die is used for synchronous coating. The die is provided with a first chamber and a second chamber separated by an adjustable shim partition. The first chamber contains conventional active slurry, and the second chamber contains transition reinforcement slurry. The coating substrate is controlled to move at a speed of 2 to 50 m / min, so that the conventional active slurry is extruded from the first chamber to form a coating area (1), and the transition reinforcement slurry is extruded from the second chamber to form a transition reinforcement band (2). The transition reinforcement band (2) is located between the coating area and the preset blank area (3). There is a natural mixing area between the two slurries at the interface, and its width is less than 0.2 mm. S3: Drying. The coated electrode is sent into a multi-temperature zone oven for gradient drying, with the low temperature zone at 60-80°C and the oven length at 3-5 m, so that the drying rate of the transition reinforcement zone (2) matches that of the coated zone (1) to prevent interface cracking. S4: Roll pressing to obtain an electrode sheet with a three-zone gradient structure.

6. The method for preparing the electrode sheet for a multi-tab battery cell according to claim 5, characterized in that, The conductive agent in S1 is selected from one or more of Super P, C45, C65, acetylene black, artificial graphite, natural graphite, carbon nanotubes (CNT), and graphene; the aqueous solvent is deionized water; the oil solvent is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO); the transitional reinforcing slurry binder is selected from one or more of polyvinylidene fluoride (PVDF), polyvinyl chloride (PVF), polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FRP), soluble polytetrafluoroethylene (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-tetrachloroethylene copolymer (ETFE), polyimide resin (PI), styrene-butadiene rubber, polyamide, polyterephthalic acid, their derivatives, their crosslinks, and their copolymers.

7. The method for preparing the electrode sheet for a multi-tab battery cell according to claim 5, characterized in that, The preparation of the transition-reinforced slurry in S1 includes the following steps: Take a binder, an oil-based solvent, a conductive agent, an optional active material, and / or nano-ceramic powder, wherein the mass ratio of the binder, oil-based solvent, conductive agent, active material, and nano-ceramic powder is (3-10):(20-30):(5-15):(30-60):(2-8). At room temperature, add the binder and solvent to a mixer and disperse at high speed for 2-5 hours to obtain a slurry. Then add the conductive agent and continue high-speed dispersion for 1 hour. Finally, add the active material and nano-ceramic powder at the same time, appropriately reduce the dispersion speed of the mixer, and continue stirring for 1-3 hours to obtain a transition-reinforced slurry.

8. The method for preparing the electrode sheet for a multi-tab battery cell according to claim 5, characterized in that, In the drying step, after the low temperature zone, there is a medium temperature zone of 90-110℃ and a length of 4-6 m, and a high temperature zone of 120-140℃ and a length of 2-4 m.

9. The method for preparing the electrode sheet for a multi-tab battery cell according to claim 5, characterized in that, In the rolling step, the compaction density difference between the transition reinforcement zone (2) and the coating zone is controlled by partitioned rolling to ensure that the difference is ≤0.2 g / cm³.

10. The application of the electrode sheet for a multi-tab cell according to any one of claims 1 to 4 or the method for preparing the electrode sheet for a multi-tab cell according to any one of claims 5 to 9 in all compatible multi-tab cylindrical lithium-ion batteries such as 4680, 4695, 32650, and 21700.

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