Pole piece tab, preparation method thereof and lithium ion battery

Abstract

The invention provides a pole piece tab, a preparation method thereof and a lithium ion battery. The pole piece tab comprises a base material layer, a metal conductive layer and a coating, the material of the base material layer is selected from an organic polymer material; the metal conductive layers are arranged on the surfaces of the two sides of the base material layer; the coating is arranged on at least one side surface, away from the substrate layer, of the metal conductive layer; the coating comprises a tab region and an active material region, the material of the tab region comprises a metal material, and the material of the active material region is selected from a positive electrode active material or a negative electrode active material. Compared with a traditional composite current collector, the pole piece tab provided by the invention further comprises a coating with a specific structure, so that welding treatment is facilitated. The pole piece and the pole lug provided by the invention have good conductivity and relatively low internal resistance, and the electrochemical performance and the cycling stability of the lithium ion battery can be improved when the pole piece and the pole lug are applied to the lithium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery preparation, and in particular to a pole piece and tab, a preparation method thereof, and a lithium ion battery. Background Art

[0002] In the production process of lithium batteries, metal foil is usually used as the current collector, with aluminum foil being used as the positive electrode current collector and copper foil being used as the negative electrode current collector. To improve the energy density and safety of the battery, a composite current collector composed of a polymer film and a metal coating has gradually attracted attention. However, due to the insulating properties of the polymer film used, the metal coatings on both sides of the polymer film are not conductive, and traditional welding methods are no longer suitable for welding this type of composite current collector. Using traditional welding methods, that is, directly welding the tabs of multi-layer composite current collectors, or welding the tabs and metal tabs of multiple layers of composite current collectors stacked alternately, both fail to weld successfully.

[0003] The commonly used method currently involves placing two to five layers of pure metal foil between the multi-layer metal tabs, and then welding these tabs to the lithium battery's positive aluminum tabs or negative copper tabs. However, this welding process is still difficult and prone to poor welding, resulting in a high internal resistance battery.

[0004] Therefore, it is necessary to research and develop a pole piece and a pole ear and a preparation method thereof, which is of great significance for improving the welding processing effect of the pole piece and the pole ear, improving the yield of the product, and thus improving the electrochemical performance and cycle stability of the lithium-ion battery. Summary of the Invention

[0005] The main purpose of the present invention is to provide a pole piece and pole ear, a preparation method thereof and a lithium ion battery, so as to solve the problems in the prior art that the welding processing of the pole piece and pole ear is difficult, the welding effect is poor, and the product yield is low and the conductivity is poor.

[0006] In order to achieve the above-mentioned purpose, the present invention provides a pole piece and pole tab, which includes: a substrate layer, the material of the substrate layer is selected from organic polymer materials; a metal conductive layer, the metal conductive layer is arranged on both side surfaces of the substrate layer; a coating, the coating is arranged on at least one side surface of the metal conductive layer away from the substrate layer; the coating includes an adjacent pole tab area and an active material area, the material of the pole tab area includes a metal material, and the material of the active material area is selected from positive electrode active material or negative electrode active material.

[0007] Furthermore, the metal material is selected from one or more metal elements in the group consisting of elements in Group VIII, Group IVB, Group IB, Group VIB, Group IA, Group IIA, Group IIIA, Group IVA, and Group IIB; and / or, one or more alloys in the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys.

[0008] Furthermore, the metal element is selected from one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn.

[0009] Furthermore, the alloy is selected from one or more of the group consisting of copper alloys, aluminum alloys and nickel alloys.

[0010] Furthermore, the D50 of the metal material is 1 to 10 μm.

[0011] Furthermore, the ratio of the projected areas of the tab region and the active material region on the surface of the metal conductive layer is (10-15):(1000-1500).

[0012] Furthermore, the projection shape of the tab region on the surface of the metal conductive layer is a rectangle.

[0013] Furthermore, the projection shape of the active material region on the surface of the metal conductive layer is a rectangle.

[0014] Furthermore, the substrate layer is selected from polyethylene terephthalate film or biaxially oriented polypropylene film.

[0015] Furthermore, the thickness of the metal conductive layer is 0.5-3 μm.

[0016] Furthermore, the thickness of the tab region is 5 to 15 μm.

[0017] Furthermore, the thickness of the active material region is 130 to 150 μm.

[0018] Furthermore, the positive electrode active material is selected from one or more of the group consisting of nickel-cobalt-manganese ternary positive electrode materials, lithium iron phosphate, lithium manganese oxide, and lithium cobalt oxide.

[0019] Furthermore, the negative electrode active material is selected from one or more of the group consisting of artificial graphite, natural graphite, and silicon oxide.

[0020] Furthermore, the D50 of the positive electrode active material is 4 to 30 μm.

[0021] Furthermore, the D50 of the negative electrode active material is 5 to 100 μm.

[0022] In order to achieve the above-mentioned purpose, another aspect of the present invention further provides a method for preparing the above-mentioned pole piece and pole ear provided in the present application, and the method for preparing the pole piece and pole ear comprises: step S1, preparing metal conductive layer preparation layers on both sides of the substrate layer preparation layer to obtain a first stacked structure; the material of the substrate layer preparation layer is selected from organic polymer materials; step S2, coating a first slurry containing a metal material on at least one side surface of the metal conductive layer preparation layer away from the substrate layer preparation layer to form a plurality of first slurry coating areas arranged in an array; at the same time, coating a second slurry containing an active material on at least one side surface of the metal conductive layer preparation layer away from the substrate layer preparation layer to form a second slurry coating area, wherein the array formed by the first slurry coating area and the second slurry coating area are arranged in an array. The coating areas are arranged alternately; after drying, a second laminated structure containing a coating preparation layer is obtained, and the coating preparation layer includes a plurality of spaced-apart pole tab areas and active material areas, wherein the array formed by the pole tab areas is arranged alternately with the active material areas; in step S2, the coating process is carried out by extrusion coating, gravure coating, screen printing, doctor blade coating or spraying; in step S3, the second laminated structure is subjected to pole piece forming treatment to obtain a third laminated structure; the third laminated structure includes an adjacent pole tab area and an active material area; in step S4, the pole tab areas of the plurality of third laminated structures are welded so that the substrate layer preparation layer, the metal conductive layer preparation layer and the coating preparation layer respectively form a substrate layer, a metal conductive layer and a coating to obtain a pole piece pole tab.

[0023] Furthermore, the projection shape of the first slurry coating area on the surface of the metal conductive layer preparation layer is selected from hexagon, circle, square, rectangle or rhombus.

[0024] Furthermore, when the projection shape of the first slurry coating area on the surface of the metal conductive layer preparation layer is circular, the radius r of each first slurry coating area is 3-8 mm, and the distance d1 between the centers of two adjacent first slurry coating areas is 6-16 mm.

[0025] Furthermore, when the projection shape of the first slurry coating area on the surface of the metal conductive layer preparation layer is a square, the side length a of each first slurry coating area is 4 to 15 mm, and the distance d2 between the centers of two adjacent first slurry coating areas is 4 to 15 mm.

[0026] Furthermore, when the projection shape of the first slurry coating area on the surface of the metal conductive layer preparation layer is a rectangle, the length h of each first slurry coating area is 4 to 10 mm and the width w is 8 to 15 mm, and the distance d3 between the centers of two adjacent first slurry coating areas is 4 to 10 mm.

[0027] Furthermore, when the projection shape of the first slurry coating area on the surface of the metal conductive layer preparation layer is a regular hexagon, the side length b of each first slurry coating area is 1 to 5 mm, and the distance d4 between the centers of two adjacent first slurry coating areas is 5 to 25 mm.

[0028] Furthermore, the coating amount of the first slurry coating area is 10 to 60 g / cm 2 .

[0029] Furthermore, the coating amount of the second slurry coating area is 100 to 200 g / cm 2 .

[0030] Furthermore, the drying temperature is 50-100° C., and the drying time is 12-60 minutes.

[0031] Furthermore, the width of the substrate layer preparation layer and the metal conductive layer preparation layer is 190-1000 mm, and the widths of the two are the same.

[0032] Another aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator arranged between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode and / or the negative electrode is selected from the above-mentioned electrode sheet and tab provided in the present application, or is selected from the electrode sheet and tab prepared by the preparation method of the above-mentioned electrode sheet and tab provided in the present application.

[0033] By applying the technical solution of the present invention, compared to conventional composite current collectors, the above-mentioned pole piece and tab provided by this application also include a coating with a specific structure. The inventors creatively discovered during their research that during the welding process, the metal material in the tab region of the coating undergoes violent vibrations due to the absorption of heat, and the tab region and the metal conductive layer transform into a molten state with viscoelasticity, which is then cooled to form a weld region. Because free electrons can move freely in the weld region, the resulting pole piece and tab have good conductivity and low internal resistance. Applying this in lithium-ion batteries can improve the electrochemical performance and cycle stability of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 A schematic diagram of the cross-sectional structure of a pole piece and a pole ear in a preferred embodiment of the present application is shown;

[0036] Figure 2 A top view of a pole piece and a pole ear in a preferred embodiment of the present application is shown;

[0037] Figure 3A schematic cross-sectional view of a second laminated structure including a coating preparation layer in a preferred embodiment of the present application is shown;

[0038] Figure 4 A top view of a second laminated structure including a coating preparation layer after coating and before drying in a preferred embodiment of the present application is shown, and a schematic diagram of an array arrangement of multiple first slurry coating areas when the projection shape of the first slurry coating area on the surface of the metal conductive layer is circular is shown;

[0039] Figure 5 FIG2 shows a top view of a second laminated structure including a coating preparation layer after coating and before drying in a preferred embodiment of the present application, and a schematic diagram of an array arrangement of multiple first slurry coating areas when the projection shape of the first slurry coating area on the surface of the metal conductive layer is a square;

[0040] Figure 6 FIG2 shows a top view of a second laminated structure including a coating preparation layer after coating and before drying in a preferred embodiment of the present application, and a schematic diagram of an array arrangement of multiple first slurry coating areas when the projection shape of the first slurry coating area on the surface of the metal conductive layer is a rectangle;

[0041] Figure 7 A top view of a second stacked structure containing a coating preparation layer in a preferred embodiment of the present application is shown before drying after coating, and a schematic diagram of the array arrangement of multiple first slurry coating areas when the projection shape of the first slurry coating area on the surface of the metal conductive layer is a regular hexagon.

[0042] The above drawings include the following reference numerals:

[0043] 10. substrate layer; 20. metal conductive layer; 30. coating layer; 40. tab area; 50. active material area;

[0044] 11. Substrate layer preparation layer; 12. Metal conductive layer preparation layer; 13. Coating preparation layer; 14. First slurry coating area; 15. Second slurry coating area. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0046] As described in the background art, the existing pole piece and pole ear have the problems of high difficulty in welding and poor welding effect, resulting in low product yield and poor conductivity. In order to solve the above technical problems, the first aspect of the present application provides a pole piece and pole ear, such as Figure 1As shown, the pole piece and tab include: a substrate layer 10, a metal conductive layer 20 and a coating 30; the material of the substrate layer 10 is selected from organic polymer materials; the metal conductive layer 20 is arranged on both sides of the substrate layer 10; the coating 30 is arranged on at least one side of the metal conductive layer 20 away from the substrate layer 10; Figure 2 As shown, the coating 30 includes a tab region 40 and an active material region 50 adjacent to each other. The material of the tab region 40 includes a metal material, and the material of the active material region 50 is selected from a positive electrode active material or a negative electrode active material.

[0047] Conventional composite current collectors have a "sandwich" structure, comprising a substrate layer 10 and metal conductive layers 20 disposed on either side of the substrate layer 10. However, conventional welding methods are difficult to weld the composite current collector to the electrode tabs, resulting in poor welding results and high internal resistance of the resulting electrode tabs, which in turn affects the electrochemical performance and cycling stability of lithium-ion batteries.

[0048] Compared to traditional composite current collectors, the above-mentioned pole piece and tab provided in this application also includes a coating 30 of a specific structure. During the research process, the inventor creatively discovered that during the welding process, the metal material in the tab region 40 in the coating 30 vibrates violently due to the absorption of heat, and the tab region 40 and the metal conductive layer 20 are transformed into a molten state with viscoelasticity, and then cooled to form a welded area. Since free electrons can move freely in the welded area, the resulting pole piece and tab have good conductivity and low internal resistance. Applying it in lithium-ion batteries can improve the electrochemical performance and cycle stability of lithium-ion batteries.

[0049] In a preferred embodiment, the metal material in the first slurry includes, but is not limited to, one or more metal elements from the group consisting of elements from Groups VIII, IVB, IB, VIB, IA, IIA, IIIA, IVA, and IIB; and / or one or more alloys from the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys. Compared to other types, the use of the aforementioned metal materials facilitates better utilization of the tab region 40 in the coating 30, improves welding processing results, reduces welding difficulty, and thus helps reduce the internal resistance of the tab and improves the electrochemical performance of the lithium-ion battery.

[0050] In order to further improve the welding treatment effect and further reduce the welding difficulty, preferably, the metal element includes but is not limited to one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn; the alloy includes but is not limited to one or more of the group consisting of copper alloy, aluminum alloy and nickel alloy.

[0051] In order to further enhance the conductive properties of the metal material and improve the welding process, preferably, the D50 of the metal material is 1 to 10 μm. The D50 of the metal material refers to the particle size value of the metal material corresponding to the cumulative distribution percentage reaching 50% in the particle size distribution curve.

[0052] In a preferred embodiment, the ratio of the projected areas of the tab region 40 to the active material region 50 on the surface of the metal conductive layer 20 is (10-15):(1000-1500). Compared to other ranges, limiting the ratio of the projected areas of the tab region 40 to the active material region 50 on the surface of the metal conductive layer 20 to the above range is beneficial for improving the conductivity of the electrode tab while reducing production costs.

[0053] In a preferred embodiment, the projection of the tab region 40 onto the surface of the metal conductive layer 20 is a rectangle, preferably with a length of 10-15 mm and a width of 8-10 mm. The tab region 40 has a conventional shape to facilitate subsequent cell fabrication. Compared to other dimensions, limiting its dimensions to the above range facilitates optimal conductivity of the tab and facilitates matching the dimensions of subsequent cells.

[0054] In a preferred embodiment, the active material region 50 is projected onto the surface of the metal conductive layer 20 in a rectangular shape, preferably with a length of 60 to 117 mm and a width of 56 to 87 mm. The conventional shape of the active material region 50 facilitates subsequent cell fabrication. Compared to other dimensions, limiting its dimensions to the aforementioned range facilitates better utilization of the active material and facilitates matching the dimensions of subsequent cells.

[0055] In order to reduce the weight of the battery and improve the flexibility of the electrode tabs without affecting the conductivity of the electrode tabs, in a preferred embodiment, the thickness of the substrate layer 10 is 2 to 15 μm, preferably 4.5 to 8 μm.

[0056] In a preferred embodiment, the substrate layer 10 includes, but is not limited to, polyethylene terephthalate film (PET) or biaxially oriented polypropylene film (BOPP). Compared to other types, the use of the above-mentioned substrate layer 10 helps reduce the weight of the battery and also helps improve the flexibility of the electrode tabs. When the lithium-ion battery is impacted by foreign objects, the substrate layer 10 can wrap the fracture surface, thereby preventing the fracture from piercing the diaphragm and causing a short circuit, thereby improving the safety performance of the battery.

[0057] In a preferred embodiment, the thickness of the metal conductive layer 20 is 0.5-3 μm. Compared with other ranges, limiting the thickness of the metal conductive layer 20 to the above range is beneficial to subsequent welding processing, thereby improving the conductivity of the electrode tab.

[0058] In a preferred embodiment, the thickness of the tab region 40 is 130-150 μm. The thickness of the tab region 40 includes but is not limited to the above range. Limiting the thickness of the tab region 40 within the above range is beneficial to improving the conductivity of the tab and facilitates subsequent welding.

[0059] In a preferred embodiment, the thickness of the active material region 50 is 5 to 15 μm. The thickness of the active material region 50 includes but is not limited to the above range. Limiting the thickness of the active material region 50 within the above range is conducive to the active material function, thereby improving the electrochemical performance of the electrode tab.

[0060] In a preferred embodiment, the positive electrode active material is selected from one or more of the group consisting of nickel-cobalt-manganese ternary positive electrode materials, lithium iron phosphate, lithium manganese oxide, and lithium cobalt oxide. Compared to other types, the use of these types of positive electrode active materials is beneficial for improving the electrochemical performance of the electrode sheet and tab, thereby improving the electrochemical performance of the lithium-ion battery.

[0061] In a preferred embodiment, the negative electrode active material is selected from one or more of the group consisting of artificial graphite, natural graphite, and silicon dioxide. Compared to other types, the use of the above-mentioned negative electrode active materials is beneficial for improving the electrochemical performance of the electrode sheet and tab.

[0062] To further improve the electrochemical performance of the positive electrode active material, and thus the electrode tab, the D50 of the positive electrode active material is preferably 4 to 30 μm. The D50 of the positive electrode active material refers to the particle size value of the positive electrode active material corresponding to the cumulative distribution percentage reaching 50% in the particle size distribution curve.

[0063] To further improve the electrochemical performance of the negative electrode active material, and thus the electrode tab, the negative electrode active material preferably has a D50 of 5 to 100 μm. The D50 of the negative electrode active material refers to the particle size value of the negative electrode active material corresponding to the cumulative distribution percentage reaching 50% in the particle size distribution curve.

[0064] The second aspect of the present application further provides a method for preparing the above-mentioned pole piece and pole ear provided by the present application, and the method for preparing the pole piece and pole ear comprises: step S1, preparing a metal conductive layer preparation layer 12 on both sides of the substrate layer preparation layer 11 to obtain a first laminated structure; the material of the substrate layer preparation layer 11 is selected from an organic polymer material; step S2, coating a first slurry containing a metal material on at least one side of the surface of the metal conductive layer preparation layer 12 away from the substrate layer preparation layer 11 to form a plurality of first slurry coating areas 14 arranged in an array; and at the same time, coating a second slurry containing an active material on at least one side of the surface of the metal conductive layer preparation layer 12 away from the substrate layer preparation layer 11 to form a second slurry coating area 15, wherein, as Figure 3 As shown, the array formed by the first slurry coating area 14 is alternately arranged with the second slurry coating area 15; after drying, a second laminated structure containing a coating preparation layer 13 is obtained, and the coating preparation layer 13 includes a pole ear area 40 and an active material area 50, wherein the array formed by the pole ear area 40 is alternately arranged with the active material area 50; in step S2, the coating process is carried out by extrusion coating, gravure coating, screen printing, doctor blade coating or spraying; in step S3, the second laminated structure is subjected to a pole piece forming process to obtain a third laminated structure; the third laminated structure includes an adjacent pole ear area 40 and an active material area 50; in step S4, a plurality of third laminated structures are stacked and the pole ear area 40 is welded, so that the substrate layer preparation layer 11, the metal conductive layer preparation layer 12, and the coating preparation layer 13 respectively form a substrate layer 10, a metal conductive layer 20 and a coating 30 to obtain a pole piece pole ear.

[0065] Compared to the composite current collector, the second laminated structure obtained by the above-mentioned preparation method of the present application includes a coating preparation layer 13 with a specific structure. During the research process, the inventor creatively discovered that during the welding process, the metal material of the tab area 40 in the coating preparation layer 13 vibrates violently due to the absorption of heat, and the tab area 40 and the metal conductive layer 20 are transformed into a molten state with viscoelasticity, and then cooled to form a welding area. Since free electrons can move freely in the welding area, the pole piece tab obtained by the subsequent pole piece forming process has good conductivity and low internal resistance. Its application in lithium-ion batteries can improve the electrochemical performance and cycle stability of lithium-ion batteries. Moreover, compared to the traditional manual coating method of applying the first slurry or the second slurry, the above-mentioned coating method is used to form the first slurry coating area 14 and the second slurry coating area 15, which can improve the production efficiency and product yield of the pole piece tab.

[0066] In a preferred embodiment, the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 includes but is not limited to a hexagon, a circle, a square, a rectangle or a diamond. Compared to directly coating a first slurry layer to form a sheet, forming a plurality of first slurry coating areas 14 arranged in an array and obtaining a tab area 40 is convenient for subsequent welding processing, thereby improving the conductivity and yield of the electrode tab.

[0067] In a preferred embodiment, Figure 4 As shown, when the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is circular, the radius r of each first slurry coating area 14 is 3 to 8 mm, and the distance d1 between the centers of two adjacent first slurry coating areas 14 is 6 to 16 mm; or Figure 5 As shown, when the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a square, the side length a of each first slurry coating area 14 is 4 to 15 mm, and the distance d2 between the centers of two adjacent first slurry coating areas 14 is 4 to 15 mm; or Figure 6 As shown, when the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a rectangle, the length h of each first slurry coating area 14 is 4 to 10 mm and the width w is 8 to 15 mm, and the distance d3 between the centers of two adjacent first slurry coating areas 14 is 4 to 10 mm; or Figure 7 As shown, when the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a regular hexagon, the side length b of each first slurry coating area 14 is 1 to 5 mm, and the distance d4 between the centers of two adjacent first slurry coating areas 14 is 5 to 25 mm. For different projection shapes, the size of each first slurry coating area 14 and the positional relationship between two adjacent first slurry coating areas 14 include but are not limited to the above ranges. Limiting them to the above ranges facilitates subsequent welding processing, thereby further improving the conductivity and yield of the electrode sheet and tab, and further improving the performance of the lithium-ion battery.

[0068] In a preferred embodiment, the width of the substrate layer preparation layer 11 and the metal conductive layer preparation layer 12 is 190 to 1000 mm, and the width of the two is the same. The width of the substrate layer preparation layer 11 and the metal conductive layer preparation layer 12 includes but is not limited to the above range. Limiting them to the above range is conducive to the subsequent formation of multiple first slurry coating areas 14 arranged in an array, and is conducive to the subsequent formation of arrayed tab areas 40 and active material areas 50, and the array formed by the tab areas 40 and the active material areas 50 are alternately arranged, thereby facilitating the subsequent pole piece forming process (such as slitting and die cutting); at the same time, the above width facilitates the use of existing coating equipment for coating the first slurry and the second slurry, without the need to adjust the coating equipment, which is conducive to reducing production costs and improving production efficiency.

[0069] It should be noted that the number of the third stacked structures obtained after the pole piece forming process corresponds to the width of the substrate layer preparation layer 11 and the metal conductive layer preparation layer 12, and the number of slitting and die-cutting cuts can be adjusted according to the actual required size of the pole piece and the pole ear.

[0070] In a preferred embodiment, the coating amount of the first slurry coating area 14 is 10 to 60 g / cm 2 The coating amount of the first slurry coating area 14 includes but is not limited to the above range. Limiting it to the above range is beneficial to the subsequent welding process, thereby further improving the conductivity and yield of the electrode sheet and the tab.

[0071] In a preferred embodiment, the coating amount of the second slurry coating area 15 is 100 to 200 g / cm 2 The coating amount of the second slurry coating area 15 includes but is not limited to the above range. Limiting it to the above range is conducive to exerting the role of the active material, thereby further improving the conductivity and yield of the electrode sheet and tab.

[0072] In a preferred embodiment, the first slurry further includes a first dispersant and a matrix resin B. The introduction of the first dispersant can improve the surface properties of the metal material, enhance its dispersibility, and improve the coating processability of the first slurry; the introduction of the matrix resin B can improve the dispersibility of the metal material and also enable the metal slurry to better adhere to the surface of the metal conductive layer preparation layer 12, thereby improving the welding process effect.

[0073] In order to further enhance the role of the tab region 40 in promoting welding and further improve the welding effect, preferably, the first slurry includes 5 to 10 parts of metal material, 5 to 10 parts of the first dispersant and 0.5 to 1 part of the base resin B by weight.

[0074] In order to further improve the dispersibility of the metal material, preferably, the first dispersant includes but is not limited to a novolac epoxy resin, more preferably a novolac epoxy resin with an epoxy value of 0.44 to 0.8.

[0075] In a preferred embodiment, matrix resin B includes, but is not limited to, a thermoplastic resin, more preferably one or more of the group consisting of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene, and even more preferably one or more of the group consisting of polyvinylidene fluoride with a weight-average molecular weight of 390,000 to 690,000, polyvinyl alcohol with a weight-average molecular weight of 60,000 to 150,000, and polytetrafluoroethylene with a weight-average molecular weight of 100,000 to 1,000,000. Compared to other types, the use of these resins facilitates melting during welding, thereby improving welding quality and, in turn, reducing the internal resistance of the electrode tab.

[0076] In a preferred embodiment, the first slurry further includes one or more of the group consisting of a first auxiliary dispersant, a curing agent, an accelerator, and a coupling agent. The introduction of the first auxiliary dispersant can improve the dispersibility of the metal material; the introduction of the curing agent can improve the structural stability of the tab region 40 formed after the first slurry is applied, improve the cross-linking and curing performance of the tab region 40, and thus promote the subsequent welding process; the introduction of the accelerator can improve the curing performance of the first slurry; the introduction of the coupling agent can improve the cross-linking and curing performance of the tab region 40, thereby improving its structural stability and promoting the subsequent welding process.

[0077] In order to further improve the dispersibility of the metal material and further improve the coating processability of the first slurry, preferably, in the first slurry, the weight ratio of the metal material to the first auxiliary dispersant is 1:(0.1~0.5); further preferably, the first auxiliary dispersant includes but is not limited to a styrene-butadiene rubber aqueous solution and / or polyacrylamide, and further preferably a styrene-butadiene rubber aqueous solution with a solid content of 35~55% and / or 500,000~20,000,000 polyacrylamide.

[0078] In order to further improve the structural stability of the tab region 40 and improve the cross-linking and curing performance of the tab region 40 , preferably, in the first slurry, the weight ratio of the metal material to the curing agent is 1:(0.01-0.1).

[0079] The curing agent used in this application can be a light curing agent and / or a heat curing agent commonly used in the art. In a preferred embodiment, the curing agent includes but is not limited to diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide and / or 2,2-azobisisobutyronitrile.

[0080] In order to further promote the cross-linking and curing of the tab region 40 , preferably, in the first slurry, the weight ratio of the metal material to the accelerator is 1:(0.01-0.5); further preferably, the accelerator includes but is not limited to polyetheramine and / or acrylate.

[0081] In order to further promote the cross-linking and curing of the tab area 40, preferably, in the first slurry, the weight ratio of the metal material to the coupling agent is 1:(0.01~0.5); further preferably, the coupling agent includes but is not limited to one or more of the group consisting of chromium complex coupling agents, silane coupling agents and titanate coupling agents.

[0082] In a preferred embodiment, the drying temperature is 50-100°C and the drying time is 12-60 minutes. The drying temperature and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to improving the curing and crosslinking performance of the tab region 40, thereby improving the welding effect, reducing the internal resistance of the pole piece and tab, and further improving the electrochemical performance of the lithium-ion battery.

[0083] In a preferred embodiment, in step S1, a wet or dry method is used to prepare the metal conductive layer preparatory layer 12. Using such a method to prepare the metal conductive layer preparatory layer 12 facilitates subsequent coating of the second slurry and subsequent drying and soldering. For example, physical vapor deposition, evaporation deposition, sputtering deposition, and laser deposition methods can be used.

[0084] Ultrasonic welding is a welding method that uses a metal welding head to apply high-frequency and low-amplitude vibrations at the interface of the connection surface of the welding material, thereby first generating frictional heat at the welding interface, and then generating viscoelastic heat internally through frictional heat, thereby connecting the materials together. In a preferred embodiment, ultrasonic welding is used for welding, and the welding frequency is 2000-38000 Hz, the amplitude is 5-95%, the welding pressure is 0.2-0.8 MPa, and the welding time is 0.1-0.4 s. Compared with other ranges, limiting the frequency, amplitude, welding pressure and welding time in the ultrasonic welding process to the above range is conducive to improving the welding effect, thereby helping to reduce the internal resistance of the battery electrode and improve the electrochemical performance of the lithium-ion battery.

[0085] Laser welding utilizes the absorption of laser radiation by the materials being welded, causing the materials to melt and then cool and solidify, ultimately welding the materials together. In a preferred embodiment, laser welding is performed with a power of 500-1000W, a welding rate of 30-60mm / s, and a welding time of 0.1-5s. Limiting the laser welding process parameters within these ranges improves welding performance compared to other ranges, thereby reducing the internal resistance of the battery electrode and enhancing the electrochemical performance of the lithium-ion battery.

[0086] In a preferred embodiment, riveting is used for welding, with a riveting welding head having a diameter of 1 to 15 mm and a welding temperature of 800 to 1400°C. Limiting the laser welding process parameters to the above ranges, compared to other ranges, improves the welding effect, thereby reducing the internal resistance of the electrode tabs and enhancing the electrochemical performance of the lithium-ion battery.

[0087] In order to further improve the welding effect, preferably, the welding process is performed in an inert atmosphere.

[0088] In a fifth aspect, the present application further provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein the positive electrode and / or the negative electrode include, but are not limited to, the aforementioned pole piece and tab provided in the present application, or include, but are not limited to, pole piece and tabs produced by the aforementioned pole piece and tab production method. The pole piece and tab produced by the aforementioned production method provided in the present application have excellent conductivity and low internal resistance, and have a high production yield. Application of the pole piece and tab in a lithium-ion battery can effectively improve its electrochemical performance and cycle stability.

[0089] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0090] Example 1

[0091] A method for preparing a pole piece and a pole tab, comprising:

[0092] (1) Preparing a 6 μm thick and 350 mm wide PET substrate layer preparatory layer 11, and physically vapor depositing a 1 μm thick copper layer on both sides of the substrate layer preparatory layer 11 as a metal conductive layer preparatory layer 12 to obtain a first laminated structure;

[0093] (2) Weighing 50 g of copper, 50 g of phenolic epoxy resin (epoxy value 0.5), 5 g of polyvinylidene fluoride, 0.5 g of polyacrylamide, and 5 g of styrene-butadiene rubber aqueous solution (solid content 50%), stirring at room temperature for 12 h to obtain a first slurry containing copper; wherein the D50 of the copper is 1.2 μm, the weight average molecular weight of the polyvinylidene fluoride is 400,000, and the weight average molecular weight of the polyacrylamide is 520,000;

[0094] Weigh 1000 g of NCM811 (nickel-cobalt-manganese ternary cathode material), 10 g of a conductive agent, 30 g of polyvinylidene fluoride, and 800 g of NMP, and stir at room temperature to obtain a second slurry containing the active material;

[0095] The first slurry is extrusion-coated on the surface of the copper layer away from the PET to form a first slurry coating area 14 with a continuous sheet layer. At the same time, the second slurry is extrusion-coated on the surface of the copper layer away from the PET to form a second slurry coating area 15, wherein the first slurry coating area 14 and the second slurry coating area 15 are coated on the same side. After drying at 65° C. for 30 minutes, a second laminated structure containing a coating preparation layer 13 is obtained. The coating preparation layer 13 includes two first slurry coating areas 14 and two second slurry coating areas 15, wherein the first slurry coating areas 14 and the second slurry coating areas 15 are alternately arranged;

[0096] (4) sequentially slitting and die-cutting the second laminate structure containing the coating preparation layer 13 in a direction perpendicular to the second laminate structure to obtain a third laminate structure, wherein the third laminate structure includes a tab region 40 and an active material region 50 adjacent to each other, wherein the tab region 40 has a thickness of 13 μm and the active material region 50 has a thickness of 145 μm;

[0097] (5) 55 third stacked structures are stacked and the tab region 40 is welded so that the substrate layer preparation layer 11, the metal conductive layer preparation layer 12, and the coating preparation layer 13 form the substrate layer 10, the metal conductive layer 20, and the coating layer 30, respectively, to obtain a tab. The coating layer 30 includes the tab region 40 and the active material region 50. The projection of the tab region 40 on the surface of the copper layer is a rectangle with a length of 10 mm and a width of 8 mm. The projection of the active material region 50 on the surface of the copper layer is a rectangle with a length of 117 mm and a width of 87 mm. The ratio of the projection area of the tab region 40 to the active material region 50 on the surface of the copper layer is 0.0079:1.

[0098] Example 2

[0099] The difference from Example 1 is that: in step (2), the first slurry is extrusion-coated on the surface of the metal conductive layer preparation layer 12 away from the substrate layer preparation layer 11 to form a plurality of first slurry coating areas 14 arranged in an array, and the array formed by the first slurry coating areas 14 is alternately arranged with the second slurry coating areas 15; the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a regular hexagon, the side length b of the regular hexagon is 5 mm, and the distance d4 between the centers of two adjacent first slurry coating areas 14 is 10 mm; the coating amount of the first slurry coating area 14 is 5 g / cm 2 The thickness of the tab region 40 in the obtained laminated structure is 1 μm.

[0100] Example 3

[0101] The difference from Example 1 is that: in step (2), the first slurry is extrusion-coated on the surface of the metal conductive layer preparation layer 12 away from the substrate layer preparation layer 11 to form a plurality of first slurry coating areas 14 arranged in an array, and the array formed by the first slurry coating areas 14 is alternately arranged with the second slurry coating areas 15; the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a circle, the radius r of the circle is 4 mm, and the distance d1 between the centers of two adjacent first slurry coating areas 14 is 8 mm; the coating amount of the first slurry coating area 14 is 10 g / cm 2 The remaining steps are the same as those in Example 1, and the thickness of the tab region 40 in the obtained laminated structure is 4 μm.

[0102] Example 4

[0103] The difference from Example 1 is that: in step (2), the first slurry is extrusion-coated on the surface of the metal conductive layer preparation layer 12 away from the substrate layer preparation layer 11 to form a plurality of first slurry coating areas 14 arranged in an array, and the array formed by the first slurry coating areas 14 is alternately arranged with the second slurry coating areas 15; the projection shape of the first slurry coating area 14 on the surface of the metal conductive layer preparation layer 12 is a square, the side length a of the square is 5 mm, and the distance d2 between the centers of two adjacent first slurry coating areas 14 is 10 mm; the coating amount of the first slurry coating area 14 is 16 g / cm 2 The remaining steps are the same as those in Example 1, and the thickness of the tab region 40 in the obtained laminated structure is 8 μm.

[0104] Example 5

[0105] The difference from Example 1 is that the coating amount of the first slurry layer is 30g / cm 2 The remaining steps are the same as those in Example 1, and the thickness of the tab region 40 obtained is 5 μm.

[0106] Example 6

[0107] The difference from Example 1 is that the coating amount of the first slurry layer is 60g / cm 2 The remaining steps are the same as those in Example 1, and the thickness of the tab region 40 obtained is 15 μm.

[0108] Example 7

[0109] The difference from Example 1 is that the coating amount of the first slurry layer is 80g / cm 2 The remaining steps are the same as those in Example 1, and the thickness of the tab region 40 obtained is 30 μm.

[0110] Comparative Example 1

[0111] The difference from Example 1 is that in step (2), manual scraping is used instead of extrusion coating to form the first slurry coating area 14, and the tab area 40 is obtained after drying.

[0112] Comparative Example 2

[0113] The difference from Example 1 is that in step (2), manual scraping is used instead of extrusion coating to form the second slurry coating area 15, and the active material area 50 is obtained after drying.

[0114] The pole piece and tab prepared in the present application are used as the negative electrode, the nickel-cobalt-manganese ternary 811 system is used as the positive electrode, the ceramic diaphragm is used as the diaphragm, and 1 mol / L LiPF6 electrolyte (containing additives such as EC / DC / EMC) is assembled into a lithium-ion battery. The square resistance of the pole piece and tab is tested using a four-probe tester. The mechanical properties of the pole piece and tab are tested using a tensile testing machine, and the tensile force corresponding to the tensile length of 15 mm is measured. The cycle stability test conditions are as follows: the voltage range is 3 to 4.2 V, and the number of cycles is recorded when the discharge capacity of the lithium-ion battery is 70%. The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117] From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects: compared with the traditional composite current collector, the above-mentioned pole piece and pole ear provided by the present application also includes a coating with a specific structure. The above-mentioned preparation method provided by the present application can effectively improve the welding effect of the pole piece and pole ear, reduce the internal resistance of the pole piece and pole ear, and apply it in lithium-ion batteries to improve the electrochemical performance and cycle stability of lithium-ion batteries. Moreover, compared with the traditional manual coating method of applying the first slurry or the second slurry, the above-mentioned coating method is used to form the first slurry coating area 14 and the second slurry coating area 15, which can improve the production efficiency and product yield of the pole piece and pole ear.

[0118] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0119] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A pole piece and a pole ear, characterized in that: The pole piece and the pole ear include: A substrate layer (10), wherein the material of the substrate layer (10) is selected from organic polymer materials; A metal conductive layer (20), the metal conductive layer (20) being arranged on both side surfaces of the substrate layer (10); A coating (30) is provided on at least one surface of the metal conductive layer (20) away from the substrate layer (10); the coating (30) includes a tab region (40) and an active material region (50) that are adjacent to each other, the material of the tab region (40) includes a metal material, and the material of the active material region (50) is selected from a positive electrode active material or a negative electrode active material.

2. The pole piece and tab according to claim 1, characterized in that: The metal material is one or more metal elements selected from the group consisting of elements in Group VIII, Group IVB, Group IB, Group VIB, Group IA, Group IIA, Group IIIA, Group IVA, and Group IIB; and / or one or more alloys selected from the group consisting of copper alloys, aluminum alloys, nickel alloys, titanium alloys, and cobalt alloys; Preferably, the metal element is selected from one or more of the group consisting of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In and Zn; Preferably, the alloy is selected from one or more of the group consisting of copper alloy, aluminum alloy and nickel alloy; Preferably, the D50 of the metal material is 1-10 μm.

3. The pole piece and tab according to claim 1, characterized in that: The ratio of the projected area of the tab region (40) to the projected area of the active material region (50) on the surface of the metal conductive layer (20) is (10-15):(1000-1500); Preferably, the projection shape of the tab region (40) on the surface of the metal conductive layer (20) is a rectangle; Preferably, the projection shape of the active material region (50) on the surface of the metal conductive layer (20) is a rectangle.

4. The pole piece and tab according to claim 1, characterized in that: The substrate layer (10) is selected from polyethylene terephthalate film or biaxially oriented polypropylene film; and / or the thickness of the metal conductive layer (20) is 0.5 to 3 μm; and / or the thickness of the tab region (40) is 5 to 15 μm; and / or the thickness of the active material region (50) is 130 to 150 μm.

5. The pole piece and tab according to claim 1, characterized in that: The positive electrode active material is selected from one or more of the group consisting of nickel-cobalt-manganese ternary positive electrode material, lithium iron phosphate, lithium manganate, and lithium cobaltate; and / or, the negative electrode active material is selected from one or more of the group consisting of artificial graphite, natural graphite, and silicon dioxide; and / or, the D50 of the positive electrode active material is 4 to 30 μm; and / or, the D50 of the negative electrode active material is 5 to 100 μm.

6. A method for preparing a pole piece and a pole tab according to claim 1, characterized in that: The method for preparing the pole piece and the pole tab comprises: Step S1, preparing metal conductive layer preparation layers (12) on both sides of the substrate preparation layer (11) to obtain a first stacked structure; the material of the substrate preparation layer (11) is selected from organic polymer materials; Step S2, coating a first slurry containing a metal material on at least one side surface of the metal conductive layer preparation layer (12) away from the substrate layer preparation layer (11) to form a plurality of first slurry coating areas (14) arranged in an array; and simultaneously coating a second slurry containing an active material on at least one side surface of the metal conductive layer preparation layer (12) away from the substrate layer preparation layer (11) to form a second slurry coating area (15), wherein the array formed by the first slurry coating area (14) and the second slurry coating area (15) are alternately arranged; after drying, a second laminated structure containing a coating preparation layer (13) is obtained, wherein the coating preparation layer (13) includes a tab area (40) and an active material area (50), wherein the array formed by the tab area (40) and the active material area (50) are alternately arranged; the coating process in step S2 is carried out by extrusion coating, gravure coating, screen printing, doctor blade coating or spray coating; Step S3, the second laminated structure is subjected to a pole piece forming process to obtain a third laminated structure; the third laminated structure includes a tab region (40) and an active material region (50) adjacently arranged; Step S4, stacking a plurality of third stacked structures and welding the tab region (40) thereof, so that the substrate layer preparation layer (11), the metal conductive layer preparation layer (12), and the coating preparation layer (13) respectively form a substrate layer (10), a metal conductive layer (20), and a coating layer (30), thereby obtaining the pole piece tab.

7. The method for preparing a pole piece and a pole tab according to claim 6, characterized in that: The projection shape of the first slurry coating area (14) on the surface of the metal conductive layer preparation layer (12) is selected from a hexagon, a circle, a square, a rectangle or a rhombus; Preferably, when the projection shape of the first slurry coating area (14) on the surface of the metal conductive layer preparation layer (12) is circular, the radius r of each first slurry coating area (14) is 3 to 8 mm, and the distance d1 between the centers of two adjacent first slurry coating areas (14) is 6 to 16 mm; Preferably, when the projection shape of the first slurry coating area (14) on the surface of the metal conductive layer preparation layer (12) is a square, the side length a of each first slurry coating area (14) is 4 to 15 mm, and the distance d2 between the centers of two adjacent first slurry coating areas (14) is 4 to 15 mm; Preferably, when the projection shape of the first slurry coating area (14) on the surface of the metal conductive layer preparation layer (12) is a rectangle, the length h of each first slurry coating area (14) is 4 to 10 mm and the width w is 8 to 15 mm, and the distance d3 between the centers of two adjacent first slurry coating areas (14) is 4 to 10 mm; Preferably, when the projection shape of the first slurry coating area (14) on the surface of the metal conductive layer preparation layer (12) is a regular hexagon, the side length b of each first slurry coating area (14) is 1 to 5 mm, and the distance d4 between the centers of two adjacent first slurry coating areas (14) is 5 to 25 mm.

8. The method for preparing a pole piece and a pole tab according to claim 6 or 7, characterized in that: The coating amount of the first slurry coating area (14) is 10 to 60 g / cm 2 and / or, the coating amount of the second slurry coating area (15) is 100 to 200 g / cm 2 ; and / or, the drying temperature is 50 to 100°C and the drying time is 12 to 60 minutes.

9. The method for preparing a pole piece and tab according to any one of claims 6 to 8, characterized in that: The width of the substrate layer preparation layer (11) and the metal conductive layer preparation layer (12) is 190 to 1000 mm, and the widths of the two are the same.

10. A lithium-ion battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, wherein: The positive electrode and / or the negative electrode is selected from the pole piece and tab according to any one of claims 1 to 5, or the pole piece and tab prepared by the preparation method of the pole piece and tab according to any one of claims 6 to 9.

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