A positive electrode sheet, a production method, and a high-density long-life battery

Abstract

This invention provides a positive electrode sheet, a preparation method, and a high-density, long-life battery. The positive electrode sheet includes a positive current collector, a positive active layer located on at least one side of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer. The tab coating includes an organic component, a first inorganic component, and a second inorganic component. The organic component includes a polymer binder. The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide. The second inorganic component includes one or more of lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte. This invention provides a tab coating on the positive electrode portion corresponding to the overhang region, solving the lithium plating problem at the edge of the negative electrode sheet, while improving the energy density and cycle life of the battery cell.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, and particularly relates to a positive electrode sheet, a preparation method thereof, and a high-density, long-life battery. Background Technology

[0002] In lithium-ion battery design, the negative electrode is typically designed to extend beyond the positive electrode in both length and width. This design is often called AC overhang design, primarily to reduce battery assembly difficulty and prevent lithium plating issues caused by the negative electrode failing to cover the positive electrode due to electrode misalignment. While the overhang design can improve battery safety through excessive electrode size, it does reduce energy density to some extent.

[0003] More seriously, the overhang design affects battery capacity and causes lithium plating at the edges of the negative electrode. During charging, some lithium ions diffuse laterally into the overhang region. During discharging, these lithium ions may not be able to completely return to the positive electrode, leading to a decrease in discharge capacity. As the number of cycles increases, lithium ions in the overhang region may gradually diffuse back into the overlapping region, but under high current conditions, this can cause an excess of lithium ions in both overlapping and non-overlapping regions, resulting in edge lithium plating and ultimately affecting the cell's cycle life.

[0004] The current approach involves adding a conventional ceramic coating to the top of the positive electrode to mitigate the lithium plating problem caused by overhang at the negative electrode, thanks to the insulating properties of ceramics. However, this method does not significantly improve the actual lithium-ion cycling performance. Summary of the Invention

[0005] The purpose of this invention is to provide a positive electrode, a preparation method, and a high-density, long-life battery. The positive electrode of this invention can solve the problem of lithium plating at the edge of the negative electrode, while improving the energy density and cycle life of the battery cell.

[0006] The present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector, a positive active layer located on at least one side of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer;

[0007] The electrode coating comprises an organic component, a first inorganic component, and a second inorganic component;

[0008] The organic component includes a polymeric binder;

[0009] The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide;

[0010] The second inorganic component includes one or more of the following: lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte.

[0011] Preferably, the organic component includes one or more of polyvinylidene fluoride, hydrogenated nitrile rubber, and polyvinyl butyral.

[0012] Preferably, in the tab coating, the mass fraction of the organic component is 5-20%, the mass fraction of the first inorganic component is 0-50%, and the mass fraction of the second inorganic component is 40-90%.

[0013] Preferably, in the tab coating, the mass fraction of the organic component is 10-15%, the mass fraction of the first inorganic component is 0-40%, and the mass fraction of the second inorganic component is 50-90%.

[0014] Preferably, an interpenetrating layer is formed at the junction of the tab coating and the positive electrode active layer.

[0015] Preferably, with the direction in which the positive electrode tab is set as the first direction, the positive electrode active layer is provided with a first tab coating and a second tab coating at two edges in the first direction, respectively.

[0016] This invention provides a method for preparing the positive electrode sheet described above, comprising the following steps:

[0017] A) The organic component, the first inorganic component, the second inorganic component, and the solvent are mixed to obtain the tab coating slurry;

[0018] B) The tab coating slurry and the positive electrode active slurry are simultaneously coated on the surface of the positive electrode current collector, and then dried and rolled to obtain the positive electrode sheet.

[0019] Preferably, the viscosity of the tab coating slurry is 2000-8000 mPa·s; the tab coating slurry and the positive electrode active slurry are simultaneously coated on the surface of the positive electrode current collector using a slit extrusion coating method.

[0020] This invention provides a high-density, long-life battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte;

[0021] The positive electrode is the positive electrode as described in any one of claims 1 to 6.

[0022] Preferably, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector;

[0023] In the first direction, the edge of the first tab coating away from the positive active layer does not extend beyond the first edge of the negative active layer in the thickness direction of the negative electrode sheet, and the edge of the second tab coating away from the positive active layer does not extend beyond the second edge of the negative active layer in the thickness direction of the negative electrode sheet.

[0024] This invention provides a positive electrode sheet, comprising a positive current collector, a positive active layer located on at least one side of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer. The tab coating comprises an organic component, a first inorganic component, and a second inorganic component. The organic component includes a polymer binder. The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide. The second inorganic component includes one or more of lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte. This invention provides a tab coating on the positive electrode portion corresponding to the overhang region, and this tab coating has electronic insulation and lithium-ion conduction properties. It can provide an ion migration channel for lithium in the non-overlapping negative electrode region during the negative electrode delithiation process, improving lithium-ion cycling and thus solving the lithium plating problem at the edge of the negative electrode sheet, while simultaneously improving the energy density and cycle life of the battery cell. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0026] Figure 1 This is a schematic diagram illustrating the working principle of the positive electrode in this invention. Figure 1 The black arrows indicate the migration direction of lithium ions;

[0027] Figure 2 This is a schematic diagram of the structure of the positive electrode (a) and the negative electrode (b) of the present invention;

[0028] Figure 3 This is a schematic cross-sectional view of the positive and negative electrode plates of the present invention.

[0029] Among them, 1+2 is the overhang region, 2 is the tab coating, 3 is the interpenetration region, 4 is the positive electrode active layer, and 5 is the negative electrode active layer. Detailed Implementation

[0030] The present invention provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector, a positive active layer located on at least one side of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer;

[0031] The electrode coating comprises an organic component, a first inorganic component, and a second inorganic component;

[0032] The organic component includes a polymeric binder;

[0033] The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide;

[0034] The second inorganic component includes one or more of the following: lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte.

[0035] In this invention, the positive current collector is preferably aluminum foil.

[0036] In this invention, the positive electrode active layer preferably includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material, binder, and conductive agent can be commonly used in the art. Specifically, in the embodiments of this invention, the positive electrode active material can be lithium cobalt oxide, the binder can be polyvinylidene fluoride, and the conductive agent can be carbon black and / or carbon nanotubes.

[0037] In this invention, a positive electrode active layer and a tab coating are disposed on the positive electrode current collector. The thickness of the tab coating is preferably equal to the thickness of the positive electrode active layer, or the absolute value of the difference between the thickness of the tab coating and the thickness of the positive electrode active layer is 0 to 20 μm, more preferably 0 to 10 μm.

[0038] In this invention, the tab coating comprises an organic component, a first inorganic component, and a second inorganic component; the organic component preferably comprises a polymeric binder, mainly providing adhesion, and more preferably comprises one or more of polyvinylidene fluoride (PVDF), hydrogenated nitrile butadiene rubber (HNBR), and polyvinyl butyral (PVB); the first inorganic component mainly functions as electronic insulation and structural support, and preferably comprises one or more of boehmite, alumina, titanium dioxide, and zirconium oxide; the second inorganic component mainly functions as providing lithium-ion transport channels, and preferably comprises one or more of lithium lanthanum titanium oxide solid electrolyte (LLTO), lithium aluminum germanium phosphate solid electrolyte (LAGP), lithium aluminum titanium phosphate solid electrolyte (LATP), and lithium lanthanum zirconium oxide solid electrolyte (LLZO).

[0039] In this invention, the organic component in the tab coating preferably has a mass fraction of 5-20%, more preferably 10-15%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, preferably within the range of any of the above values ​​as the upper or lower limit. The first inorganic component preferably has a mass fraction of 0-50%, more preferably 0-40%, such as 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, preferably within the range of any of the above values ​​as the upper or lower limit. The second inorganic component preferably has a mass fraction of 40-90%, more preferably 50-90%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, preferably within the range of any of the above values ​​as the upper or lower limit. Within this range, the formation of the tab coating can be guaranteed, and the lithium-ion transport effect can be further improved.

[0040] In this invention, the direction in which the positive electrode tab is set is taken as the first direction. In this first direction, the width of the positive electrode current collector is greater than the width of the positive electrode active layer. The positive electrode active layer has a first edge and a second edge in the first direction. Preferably, the width of the positive electrode current collector in the first direction exceeds both the first edge and the second edge of the positive electrode active layer. In this case, the tab coatings are respectively present at both ends of the positive electrode active layer in the first direction. That is, the tab coatings in this invention include a first tab coating and a second tab coating. In this invention, the first edge of the positive electrode active layer contacts the first tab coating, forming a first interpenetration region at the junction. The second edge of the positive electrode active layer contacts the second tab coating, forming a second interpenetration region at the junction. The interpenetration layer contains components of both the positive electrode active layer and the ion-conducting coating. The permeation region reduces the difference in the positive electrode coating and improves the ion-conducting performance of the coating.

[0041] In this invention, the components and proportions in the first tab coating and the second tab coating can be the same or different. Preferably, the first tab coating and the second tab coating are prepared using tab coatings with the same components.

[0042] In this invention, in the first direction, the width of the first interpenetrating zone is preferably 0 to 0.5 mm, more preferably 0.05 to 0.25 mm; the width of the second interpenetrating zone is preferably 0 to 0.5 mm, more preferably 0.05 to 0.25 mm. In this invention, the width of the first interpenetrating zone and the width of the second interpenetrating zone may be the same or different.

[0043] The present invention also provides a method for preparing the positive electrode sheet described above, comprising the following steps:

[0044] A) The organic component, the first inorganic component, the second inorganic component, and the solvent are mixed to obtain the tab coating slurry;

[0045] B) The tab coating slurry and the positive electrode active slurry are simultaneously coated on the surface of the positive electrode current collector, and then dried and rolled to obtain the positive electrode sheet.

[0046] In this invention, the organic component is first mixed with a solvent and stirred until completely dissolved and dispersed. Then, the resulting organic component solution is mixed with the first inorganic component and the second inorganic component and dispersed at high speed to obtain the tab coating slurry.

[0047] In this invention, the types and amounts of the organic component, the first inorganic component, and the second inorganic component are the same as those described above, and will not be repeated here.

[0048] In this invention, the solvent is preferably N-methylpyrrolidone (NMP), the mixing temperature of the organic component and the solvent is preferably 40-50°C, the mixing time is preferably 2-4 hours, and the viscosity of the resulting organic component solution is controlled at 10000-20000 mPa·s.

[0049] In this invention, the viscosity of the tab coating slurry is preferably 2000–8000 mPa·s. After high-speed dispersion, the viscosity of the tab coating slurry can be adjusted to the required range by adding solvent. Within this viscosity range, a more uniform interpenetrating layer can be formed during the coating process.

[0050] This invention mixes a positive electrode active material, a conductive agent, a binder, and a solvent to obtain a positive electrode active slurry. The positive electrode active material, conductive agent, binder, and solvent can all be commonly used positive electrode active materials, conductive agents, binders, and solvents in the art, or can be the same as those described above. This invention will not elaborate further here.

[0051] After obtaining the tab coating slurry and the positive electrode active slurry, the present invention preferably employs a slot extrusion coating method to simultaneously coat the tab coating slurry and the positive electrode active slurry on the surface of the positive electrode current collector. After drying and rolling, a positive electrode sheet is obtained. During the simultaneous coating process of the two slurries, interpenetration of the slurries occurs at the interface between them. After drying and rolling, a first interpenetration zone and a second interpenetration zone are formed.

[0052] In this invention, the coating speed is preferably 5-30 m / min, more preferably 10-25 m / min; the drying is preferably a three-stage drying process, with the drying temperature of the first stage preferably 60-90℃, more preferably 70-80℃, the drying temperature of the second stage preferably 100-130℃, more preferably 110-120℃, and the drying temperature of the third stage preferably 140-160℃, more preferably 145-150℃. After drying, the solvent residue in the tab coating and the positive electrode active layer is <0.1%; the rolling pressure is preferably 10-20 MPa.

[0053] This invention provides a high-density, long-life battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte.

[0054] In this invention, the positive electrode is the positive electrode described above.

[0055] In this invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the surface of the negative electrode current collector; the negative electrode current collector is preferably a copper foil, and the negative electrode active layer preferably includes a negative electrode active material, a conductive agent and a binder. The negative electrode active material, conductive agent and binder are all commonly used negative electrode active materials, conductive agents and binders in the art, and will not be described in detail here.

[0056] Furthermore, the negative electrode sheet includes an overhang region, which refers to the non-overlapping region of the negative electrode active layer and the positive electrode active layer projected in the thickness direction of the negative electrode sheet. The portion of the negative electrode sheet corresponding to this non-overlapping region is the overhang region.

[0057] In this invention, the overhang region includes a first overhang region and a second overhang region, the first overhang region corresponding to the first tab coating, and the second overhang region corresponding to the second tab coating.

[0058] In a first direction, the negative electrode active layer has a first edge near the first tab coating and a second edge near the second tab coating. The edge of the first tab coating away from the positive electrode active layer does not extend beyond the first edge of the negative electrode active layer in the thickness direction of the negative electrode sheet, and the edge of the second tab coating away from the positive electrode active layer does not extend beyond the second edge of the negative electrode active layer in the thickness direction of the negative electrode sheet.

[0059] Alternatively, in the first direction, the first edge and the edge of the first tab coating away from the positive active layer are projected to overlap in the negative electrode thickness direction, and the second edge and the edge of the second tab coating away from the positive active layer are projected to overlap in the negative electrode thickness direction.

[0060] In this invention, the diaphragm is preferably a PP diaphragm, a PE diaphragm, or a PE diaphragm coated on one side.

[0061] In this invention, the electrolyte preferably includes lithium salt, additives and solvent. The lithium salt, additives and solvent can all be commonly used lithium salt, additives and solvents in the art, and will not be described in detail here.

[0062] This invention provides a positive electrode sheet, comprising a positive current collector, a positive active layer located on at least one side of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer. The tab coating comprises an organic component, a first inorganic component, and a second inorganic component. The organic component includes a polymer binder. The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide. The second inorganic component includes one or more of lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte. This invention provides a tab coating on the positive electrode portion corresponding to the overhang region, and this tab coating has electronic insulation and lithium-ion conduction properties. It can provide an ion migration channel for lithium in the non-overlapping negative electrode region during the negative electrode delithiation process, improving lithium-ion cycling and thus solving the lithium plating problem at the edge of the negative electrode sheet, while simultaneously improving the energy density and cycle life of the battery cell.

[0063] The technical solutions of the embodiments 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, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] Example 1

[0065] Weigh PVDF 5130 according to the proportions in Table 1, dissolve it in NMP, and stir until completely dissolved and dispersed (45℃, 2h). The viscosity range is controlled at 15000±1000mPa·s.

[0066] After a uniform dispersion is formed, a mixed solid electrolyte consisting of boehmite, LLZO, and LATP in a 1:1 mass ratio (as shown in Table 1) is added and dispersed at high speed for 4-6 hours. Then, NMP is added until the slurry viscosity reaches 4000 ± 1000 mPa·s. This yields the tab coating slurry.

[0067] Lithium cobalt oxide, conductive carbon black SP, conductive carbon nanotubes CNT, binder polyvinylidene fluoride PVDF, and solvent NMP are mixed to obtain a positive electrode active slurry; wherein the mass ratio of lithium cobalt oxide, conductive carbon black SP, conductive carbon nanotubes CNT, and binder polyvinylidene fluoride PVDF is 98.2:0.4:0.8:0.6.

[0068] The tab coating slurry and the positive electrode main slurry are coated simultaneously using a slit extrusion coating method at a coating speed of 30 m / min.

[0069] Segmented drying (80℃→120℃→150℃), solvent residue after drying <0.1%.

[0070] A positive electrode sheet was prepared by rolling at a pressure of 20 MPa. The thickness difference between the tab coating and the positive electrode active layer was controlled to be 0-5 μm, and the areal density of the positive electrode sheet was 15.3 mg / cm³. 2 The positive electrode compaction density is 4.05 g / cm³. 3 .

[0071] The negative electrode material is selected from Shanshan 5C fast-charging graphite, the conductive agent is carbon black (sp), and the binders are lithium carboxymethyl cellulose (CMC-Li) and styrene-butadiene rubber (SBR). The mass ratio of the negative electrode material, conductive agent carbon black (sp), binder lithium carboxymethyl cellulose (CMC-Li), and binder SBR is 96.8:0.5:1.2:1.5; the areal density is 6.2 mg / cm³. 2 The negative electrode compaction density is 1.60 g / cm³. 3 .

[0072] A battery cell was prepared by stacking a positive electrode, a negative electrode, and a PE separator (5μm PE base film, 2μm boehmite layer, and 1μm PVDF adhesive layers on both sides). The boehmite layer of the PE separator was positioned opposite the positive electrode. The AC overhang on each side of the positive and negative electrodes was designed to be 2mm ± 0.5mm, and the interpenetration zone was controlled to be 0.1-0.2mm. An electrolyte containing 1mol / L LiPF6 was injected. The solvent consisted of EC (ethylene carbonate): EMC (ethyl methyl carbonate): PP (propyl propionate): EP (methyl propionate) in a ratio of 20%:40%:15%:25%. The additives were 0.5% VC (ethylene carbonate), 1% FEC (fluoroethylene carbonate), 1% LiPO2F2 (lithium difluorophosphate), 0.5% AND (adiponitrile), and 1.5% HTCN (hexanetrionitrile), resulting in the battery.

[0073] Examples 2-5

[0074] The battery was prepared according to the method in Example 1, except that the amounts of the organic component, the first inorganic component, and the second inorganic component were proportioned according to Table 1.

[0075] Comparative Example 1

[0076] The battery was prepared according to the method in Example 1, except that the amounts of the organic component, the first inorganic component, and the second inorganic component were proportioned according to Table 1.

[0077] Comparative Example 2

[0078] The battery was prepared according to the method in Example 1, except that no tab coating was provided in Comparative Example 2.

[0079] The battery performance of Examples 1-5 and Comparative Examples 1-2 was tested for charge and discharge performance. The full battery design capacity was 5100mAh. The batteries were subjected to 5C step charge at room temperature and 45°C high temperature cycling, with 800 cycles at room temperature and 600 cycles at high temperature.

[0080] The charging and discharging process for soft-pack batteries is as follows:

[0081] 5C constant current charging (CC) to 4.25V, 4C constant current charging (CC) to 4.35V, 3C constant current charging (CC) to 4.45V, 2C constant current constant voltage charging (CC-CV) to 4.48V, 0.05C cutoff, rest for 10 minutes;

[0082] Charge at 1C constant current (CC) to 3.0V, charge at 0.5C constant current (CC) to 3.0V, and rest for 10 minutes.

[0083] The results are shown in Table 1.

[0084] Table 1. Battery performance data for Examples 1-5 and Comparative Examples 1-2

[0085]

[0086] As shown in Table 1, batteries containing the tab coating described in this application can significantly improve battery cycle life and energy density.

Claims

1. A positive electrode sheet, the positive electrode sheet comprising a positive current collector, a positive active layer located on at least one side surface of the positive current collector, and a tab coating located on the same side of the positive current collector and in contact with the edge of the positive active layer; The electrode coating comprises an organic component, a first inorganic component, and a second inorganic component; The organic component includes a polymeric binder; The first inorganic component includes one or more of boehmite, alumina, titanium dioxide, and zirconium oxide; The second inorganic component includes one or more of the following: lithium lanthanum titanium oxide solid electrolyte, lithium germanium aluminum phosphate solid electrolyte, lithium titanium aluminum phosphate solid electrolyte, and lithium lanthanum zirconium oxide solid electrolyte.

2. The positive electrode sheet according to claim 1, characterized in that, The organic components include one or more of polyvinylidene fluoride, hydrogenated nitrile rubber, and polyvinyl butyral.

3. The positive electrode sheet according to claim 1, characterized in that, In the electrode coating, the mass fraction of the organic component is 5-20%, the mass fraction of the first inorganic component is 0-50%, and the mass fraction of the second inorganic component is 40-90%.

4. The positive electrode sheet according to claim 3, characterized in that, In the electrode coating, the mass fraction of the organic component is 10-15%, the mass fraction of the first inorganic component is 0-40%, and the mass fraction of the second inorganic component is 50-90%.

5. The positive electrode sheet according to claim 1, characterized in that, An interpenetrating layer is formed at the junction of the tab coating and the positive electrode active layer.

6. The positive electrode sheet according to claim 1, characterized in that, With the direction in which the positive electrode tab is set as the first direction, the positive electrode active layer has a first tab coating and a second tab coating respectively at two edges in the first direction.

7. A method for preparing a positive electrode sheet as described in any one of claims 1 to 6, comprising the following steps: A) The organic component, the first inorganic component, the second inorganic component, and the solvent are mixed to obtain the tab coating slurry; B) The tab coating slurry and the positive electrode active slurry are simultaneously coated on the surface of the positive electrode current collector, and then dried and rolled to obtain the positive electrode sheet.

8. The preparation method according to claim 7, characterized in that, The viscosity of the tab coating slurry is 2000-8000 mPa·s; the tab coating slurry and the positive electrode active slurry are simultaneously coated on the surface of the positive electrode current collector using a slit extrusion coating method.

9. A high-density, long-life battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; The positive electrode is the positive electrode as described in any one of claims 1 to 6.

10. The high-density, long-life battery according to claim 9, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector; In the first direction, the edge of the first tab coating away from the positive active layer does not extend beyond the first edge of the negative active layer in the thickness direction of the negative electrode sheet, and the edge of the second tab coating away from the positive active layer does not extend beyond the second edge of the negative active layer in the thickness direction of the negative electrode sheet.

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