Preparation method of carbon-foil-coated pole piece and carbon-foil-coated pole piece

Abstract

The invention discloses a preparation method of a carbon-foil-coated pole piece and the carbon-foil-coated pole piece, and the preparation method comprises the following steps: step S1, in the process of collecting a battery positive electrode or negative electrode material coating process, obtaining a coating appearance color through online identification equipment, and determining a color recognizable range of a prime coat carbon coating area of the coating process; wherein the carbon coating area comprises a normal coating area, and a first edge transition area and a second edge transition area which are arranged on two opposite sides of the normal coating area; s2, an adaptive preset micro gravure roller is engraved according to the coating procedure; s3, preparing a carbon-coated foil with a preset identification degree on the edge according to the type of the positive electrode or negative electrode material of the battery; and S4, carrying out online edge identification on the first edge transition region and the second edge transition region corresponding to the carbon coating layer, and coating an active material in the identification region to prepare the carbon foil coated pole piece. The preparation method of the carbon foil coated pole piece is high in preparation efficiency and good in product quality.

Description

[Technical field]

[0001] The invention relates to the technical field of lithium / sodium battery primer coating, and in particular to a preparation method of a carbon-coated foil pole piece used in a lithium / sodium battery and the carbon-coated foil pole piece. [Background technology]

[0002] With the development of society and economic progress, lithium, sodium and other secondary batteries on the market are becoming more and more popular. As the most widely used energy storage and transportation devices on the market, they have also been studied more deeply and systematically. Initially, the most widely used method was to directly coat the positive or negative electrode materials on the current collector. With the in-depth study of this type of battery, carbon-coated foil with a layer of carbon on the current collector has gradually become the mainstream of the market. For example, the carbon-coated foil of the most widely used lithium iron phosphate system has become a market hot spot among current collector materials.

[0003] However, unlike the metal foil used in the common ternary system, when using carbon-coated foil current collectors to carry positive or negative electrode materials, the color of the primer coating and the color of the positive or negative electrode materials are both gray-black. This results in the edges of the positive or negative electrode materials being similar and unable to be accurately identified and captured during the coating process using primer products, which leads to a series of dimensional problems such as coating offset and ceramic edge misalignment during the coating process, making it difficult to prepare qualified electrode rolls. On the other hand, when the positive or negative electrode materials undergo the rolling process, the coating edges are more likely to fall off and powder.

[0004] There is a technology on the market that uses a corner mark to position the coating by setting a corner mark at the gap of the gap gravure roller. However, the effect can only be recognized after coating, and it is necessary to adjust the equipment repeatedly to accurately align the positive or negative electrode material on the bottom coating. Therefore, the existing technology cannot be used in conjunction with the online detection and adjustment equipment of the positive or negative electrode coating process, resulting in poor quality of the obtained carbon-coated foil. [Summary of the invention]

[0005] The purpose of the embodiment of the present invention is to provide a method for preparing a carbon-coated foil pole piece to solve the problem of poor quality of the existing carbon-coated foil.

[0006] In order to solve the above technical problems, in a first aspect, an embodiment of the present invention provides a method for preparing a carbon-coated foil pole piece, the preparation method comprising the following steps:

[0007] Step S1, in the process of collecting the coating process of the positive electrode or negative electrode material of the battery, the coating appearance color is obtained by an online recognition device to determine the color identifiable range of the primer carbon coating area of ​​the coating process; wherein the carbon coating area includes a normal coating area and a first edge transition area and a second edge transition area arranged on opposite sides of the normal coating area;

[0008] Step S2, engraving a preset micro-gravure roller adapted according to the coating process;

[0009] Step S3, according to the type of the positive electrode or negative electrode material of the battery, select a matching primer slurry, and perform primer coating through the preset micro-gravure roller to obtain a carbon-coated foil with a preset recognizability at the edge; wherein the carbon-coated foil comprises a metal substrate and a carbon-coated layer coating two opposite sides of the metal substrate; the carbon-coated area corresponds to the carbon-coated layer;

[0010] Step S4, coating the carbon-coated foil, performing online edge recognition on the first edge transition region and the second edge transition region corresponding to the carbon-coated layer, and coating active material in the edge recognition region to obtain a carbon-coated foil pole piece.

[0011] Preferably, in step S1, in step S1, the carbon-coated area also includes a first blank area and a second blank area arranged on the side of the first edge transition area and the second edge transition area away from the normal coating area; the total width of the carbon-coated area is designed according to the width of the battery electrode, the width of the first edge transition area and the second edge transition area are both 1 to 2 mm, and the width of the first blank area and the second blank area are designed according to the width of the battery electrode ear; the width of the normal coating area is 2 to 4 mm narrower than the total width of the coating area.

[0012] Preferably, in step S2, the preset micro-gravure roller includes a gravure roller body and a plurality of engraving areas formed on the gravure roller body; each of the engraving areas includes a normal engraving area, two transition engraving areas arranged on opposite sides of the normal engraving area, and two blank areas arranged on a side of the transition engraving area away from the normal engraving area; the normal engraving area corresponds to the normal coating area, the two transition engraving areas respectively correspond to the first edge transition area and the second edge transition area, and the two blank areas respectively correspond to the first blank area and the second blank area.

[0013] Preferably, a plurality of engraving meshes are provided on the engraving area; if the coating of the transition engraving area needs to be darker, the meshes of the transition engraving area are gradually enlarged.

[0014] Preferably, the mesh depth of the engraving mesh in the normal engraving area is 15-50 um; the mesh depth of the engraving mesh in the transitional engraving area takes the mesh depth of the normal engraving area as the initial depth and gradually becomes shallower from the carbon-coated area toward its edge.

[0015] Preferably, the thickness of the hole wall in the normal engraving area is 3-10 um; the thickness of the hole wall in the transitional engraving area takes the thickness of the hole wall in the normal engraving area as the initial thickness and gradually thickens from the carbon-coated area toward its edge.

[0016] Preferably, the width of the through groove in the normal engraving area is 3-10 um; the width of the through groove in the transitional engraving area takes the width of the through groove in the normal engraving area as the initial width and gradually narrows from the carbon-coated area toward its edge.

[0017] Preferably, the engraved mesh is a through-groove rhombus or regular hexagonal structure.

[0018] Preferably, the step S3 specifically includes the following steps:

[0019] Step S31, preparing a primer slurry, and transferring the primer slurry to the surface of the metal substrate through the preset micro-gravure roller; wherein the amount of slurry in the normal coating area is greater than or less than the amount of slurry in the first edge transition area and the second edge transition area;

[0020] Step S32: obtaining a carbon-coated foil having a primer edge and an edge transition region by baking, and using the carbon-coated foil as a positive electrode current collector or a negative electrode current collector.

[0021] In a second aspect, an embodiment of the present invention provides a carbon-coated foil, which is prepared based on the above-mentioned method for preparing a carbon-coated foil pole piece.

[0022] Compared with the prior art, the preparation method of the carbon-coated foil electrode sheet in the present invention obtains the coating appearance color through an online recognition device during the coating process of collecting the positive or negative electrode material of the battery, and determines the color identifiable range of the base coating carbon coating area of ​​the coating process; wherein the carbon coating area includes a normal coating area and a first edge transition area and a second edge transition area arranged on opposite sides of the normal coating area; a preset micro-gravure roller adapted for engraving according to the coating process is selected; and a matching base coating is selected according to the type of the positive or negative electrode material of the battery. The slurry is coated and the primer is applied by a preset micro-gravure roller to obtain a carbon-coated foil with a preset recognizability at the edge; wherein the carbon-coated foil includes a metal substrate and a carbon-coated layer coated on two opposite sides of the metal substrate; the carbon-coated area corresponds to the carbon-coated layer; the carbon-coated foil is coated and the edge is identified online, and an active material is coated in the edge identification area to obtain a carbon-coated foil electrode; by performing special treatment on the primer edge and distinguishing the coating color of the positive or negative electrode of the battery, the stability of the production of the positive or negative electrode coating process can be improved, thereby improving the production quality of the carbon-coated foil.

Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0024] Figure 1 A flow chart of a method for preparing a carbon-coated foil electrode provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the structure of a carbon-coated foil provided in an embodiment of the present invention;

[0026] Figure 3 for Figure 2 Section view along line AA;

[0027] Figure 4 A left side view of a micro gravure roller provided in an embodiment of the present invention;

[0028] Figure 5 for Figure 4 Sectional view along line BB;

[0029] Figure 6 A schematic diagram of the engraving area of ​​a micro-gravure roller provided in an embodiment of the present invention;

[0030] Figure 7 for Figure 6 Schematic diagram of a single normal engraving area and two transitional engravings;

[0031] Figure 8 A schematic diagram of engraved meshes in the engraving area of ​​a micro-gravure roller provided in an embodiment of the present invention;

[0032] Fig. 9 Schematic diagram of the structure of 8 engraving meshes.

[0033] In the figure, 1, carbon coated foil, 2, normal coating area, 3, first edge transition area, 4, second edge transition area, 5, first blank area, 6, second blank area, 7, coating strip, 8, metal substrate, 20, micro gravure roller, 21, gravure roller body, 22, normal engraving area, 23, transition engraving area, 24, engraving mesh, 241, through groove, 242, aperture, 243, hole wall. [Specific implementation method]

[0034] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Embodiment 1

[0036] like Figure 1-Figure 5 As shown, an embodiment of the present invention provides a method for preparing a carbon-coated foil pole piece, and the preparation method comprises the following steps:

[0037] Step S1, in the process of collecting the coating appearance color of the positive or negative electrode material of the battery and identifying the carbon-coated area of ​​the primer color of the coating process through the online recognition device; wherein the carbon-coated area includes a normal coating area 2 and a first edge transition area 3 and a second edge transition area 4 arranged on opposite sides of the normal coating area 2. Optionally, the online recognition device can be a camera, etc., for taking pictures. wherein the coating appearance color is black and black-gray, the normal coating area 2 is coated black, and the color along the transition area is designed to be black-gray.

[0038] Specifically, according to the appearance of the material in the subsequent coating process, the coating appearance color identified by the online identification equipment of the battery positive or negative electrode material coating process is collected to design the carbon coating area of ​​the primer process. Each carbon coating area is designed to consist of a normal coating area 2 and two transition areas at the edge. The edge color of the subsequent active material is black, so the color of the edge transition area of ​​the primer is designed to be black and gray, so as to facilitate identification during the coating process.

[0039] The last coating process refers to the process of applying the last coating to the product during the production process. After coating, the electrode needs to be dried and cured so that the coating material can dry quickly and solidify into a film.

[0040] Step S2, engraving a preset micro gravure roller 20 adapted to the coating process. The micro gravure roller 20 is designed specifically as a primer device, and the metal substrate 8 is coated by the micro gravure roller 20.

[0041] Step S3, according to the type of the positive electrode or negative electrode material of the battery, select a matching primer slurry, and perform primer coating through the preset micro-gravure roller 20 to obtain a carbon-coated foil 1 with a preset recognizability at the edge. The carbon-coated foil 1 includes a metal substrate 8 and a carbon-coated layer coating two opposite sides of the metal substrate; the carbon-coated area corresponds to the carbon-coated layer;

[0042] Among them, the positive or negative electrode sheet to which the carbon coating layer is adapted is adapted to the thickness of the coating edge of the positive or negative electrode sheet through the transition treatment of the edge of the primer coating area, which facilitates the thinning area treatment of the positive or negative electrode sheet.

[0043] Specifically, according to the type of battery positive or negative electrode material, a matching primer slurry is selected, and the micro-gravure roller 20 prepared in step S2 is used for primer coating, so that a carbon coating layer is attached to one or both sides of the metal substrate 8, and the slurry amount in the edge transition area at the edge position of the carbon coating layer is lower, and the slurry amount in the normal coating area 2 in the middle position is higher; and then the finished carbon-coated foil 1 is obtained after baking.

[0044] Step S4, coating the carbon-coated foil 1 and identifying the edge online, coating the first edge transition area 3, the second edge transition area 4 and the normal coating area 2 corresponding to the carbon-coated layer with active materials respectively, and obtaining the carbon-coated foil 1 pole piece. Optionally, the active materials include positive electrode materials and negative electrode materials, which play a key role in storing and releasing energy in the battery. Positive electrode materials include lithium cobalt oxide, lithium iron phosphate and ternary materials, etc. Negative electrode materials include graphite and silicon materials, etc.

[0045] Specifically, the prepared carbon-coated foil 1 is used as a current collector, and one or more layers of positive or negative electrode materials are coated on the coating area thereof. The edge of the primer and the coating edge of the active material can be easily identified through the online recognition system, so as to control the spray nozzle position of the coating head online to ensure that the active material is not misplaced and directly coated on the plain foil. In this way, the coating and online edge recognition can accurately coat the positive or negative electrode material through the transition zone edge with high recognition, ensuring that the coating process does not deviate and the coating accuracy is high.

[0046] In specific implementation, during the process of collecting the coating process of the positive or negative electrode material of the battery, the coating appearance color is obtained through an online identification device to determine the color identifiable range of the primer and carbon-coated area of ​​the coating process; wherein the coating area includes a normal coating area 2 and a first edge transition area 3 and a second edge transition area 4 arranged on opposite sides of the normal coating area 2; a preset micro-gravure roller 20 adapted for engraving according to the coating process; according to the type of the positive or negative electrode material of the battery, a matching primer slurry is selected, and primer is performed through the preset micro-gravure roller 20 to obtain a carbon-coated foil 1 with a preset recognizability at the edge; the carbon-coated foil 1 is coated and the edge is identified online, and the first edge transition area 3 and the second edge transition area 4 of the carbon-coated foil 1 are respectively coated with active materials to obtain a carbon-coated foil 1 pole piece. By subjecting the primer edge to special treatment and distinguishing the coating colors of the positive or negative electrode of the battery, the edge identification confusion problem during coating of the positive or negative electrode slurry can be solved, and the production stability of the positive or negative electrode coating process can be improved; thereby improving the production quality of the carbon-coated foil 1.

[0047] In this embodiment, in the step S1, the carbon-coated area also includes a first blank area 5 and a second blank area 6 arranged on the side of the first edge transition area 3 and the second edge transition area 4 away from the normal coating area 2; the total width of the carbon-coated area is designed according to the width of the battery pole piece, the width of the first edge transition area 3 and the second edge transition area 4 are both 1-2mm, and the width of the first blank area 5 and the second blank area 6 is designed according to the width of the battery pole ear; the width of the normal coating area 2 is 2-4mm narrower than the total width of the coating area. The carbon coating thickness of the first transition area and the second transition area is 0.01-20um. Optionally, the total width of the carbon-coated area is 300-334mm, the width of the first edge transition area and the second edge transition area are both 1-2mm, and the width of the first blank area and the second blank area are both 10-30mm; the width of the normal coating area is 296mm-332mm.

[0048] Specifically, the carbon-coated foil 1 of the present invention is a three-strip coated carbon-coated foil 1, wherein each coating area is composed of a normal coating area 2 located in the middle and two edge transition areas on both sides thereof, the width of the transition area is about 2 mm, and the total width of the coating area is 334 mm; the width of the blank area in the middle is 20 mm, and the finished product is continuously coated, and both sides are coated with a carbon coating layer. The carbon coating layer is transfer-coated by a micro-gravure roller 20, the surface density of the coating in the normal area is 0.25 g / m2, the coating thickness is thin, and the single-sided thickness is controlled at 0.4 μm. The wet film is converted into a dry film by baking, and the coating texture is fluffy, so that the mechanical thickness difference between the transition area and the normal area is not obvious. Then, the carbon-coated foil 1 with high edge recognition is used as a current collector to carry out the coating of the active material. This process is identified by an online size recognition system with an identification accuracy higher than 2 mm, and the coating area position information can be easily obtained to ensure that the coating process is accurate in position without offset and dislocation. Optionally, the number of the coating strips 7 of the carbon-coated foil 1 can be a single strip, a double strip, or a plurality of strips, which is not limited here.

[0049] In this embodiment, the metal substrate 8 is aluminum foil or current collector foil.

[0050] In this embodiment, the thickness of the current collector foil is 4-50 um. Preferably, the thickness of the current collector foil is 6-15 um.

[0051] In this embodiment, the carbon coating thickness of the carbon coating layer in the normal coating area 2 is 0.2-10um; the carbon coating thickness of the carbon coating layer in the first edge transition area 3 and the second edge transition area 4 is 0.01-20um. Preferably, the carbon coating thickness of the normal coating area 2 is 0.5-2um; the carbon coating thickness of the first edge transition area 3 and the second edge transition area 4 is 0.05-0.5um.

[0052] In this embodiment, Figure 6-8 As shown, in the step S2, the preset micro-gravure roller 20 includes a gravure roller body 21 and a plurality of engraving areas formed on the gravure roller body 21; each of the engraving areas includes a normal engraving area 22, two transition engraving areas 23 arranged on opposite sides of the normal engraving area 22, and two blank areas arranged on the side of the transition engraving area 23 away from the normal engraving area 22; the normal engraving area 22 corresponds to the normal coating area 2, the two transition engraving areas 23 respectively correspond to the first edge transition area 3 and the second edge transition area 4, and the two blank areas respectively correspond to the first blank area 5 and the second blank area 6.

[0053] In this embodiment, Figure 6-9 As shown, a plurality of engraving meshes 24 are provided on the engraving area; if the coating of the transition engraving area 23 needs to be darker, the meshes of the transition engraving area 23 are gradually increased. By designing the mesh depth of the micro-concave roller engraving edge position, it can be adapted to positive or negative electrode materials of different systems, which greatly improves the adaptability of the carbon-coated foil 1 and the positive or negative electrode materials.

[0054] Specifically, if the coating of the transition engraving area 23 is required to be grayish, the transition engraving area 23 is gradually reduced to reduce the amount of ink transfer.

[0055] In this embodiment, the mesh depth of the engraving mesh 24 in the normal engraving area 22 is 15-50um; the mesh depth of the engraving mesh 24 in the transitional engraving area 23 is gradually shallower from the carbon-coated area to its edge, starting from the mesh depth of the normal engraving area 22. Preferably, the mesh depth of the engraving mesh 24 in the normal engraving area 22 is 18-25um.

[0056] Specifically, the mesh depth of the engraving mesh 24 in the transition engraving area 23 takes the mesh depth of the normal engraving area 22 as the initial depth and gradually changes, and the change direction gradually becomes shallower from the carbon-coated area to the edge of the coating.

[0057] In this embodiment, the thickness of the hole wall 243 of the normal engraving area 22 is 3-10um; the thickness of the hole wall 243 of the transitional engraving area 23 is gradually thickened from the carbon-coated area to its edge with the thickness of the hole wall 243 of the normal engraving area 22 as the initial thickness. Preferably, the thickness of the hole wall 243 of the normal engraving area 22 is 5-8um.

[0058] Specifically, the thickness of the hole wall 243 of the transitional engraving area 23 is based on the thickness of the hole wall 243 of the normal engraving area 22 as the initial thickness and gradually changes, and the direction of change is gradually thinning from the carbon-coated area to the edge of the coating.

[0059] In this embodiment, the width of the through groove 241 of the normal engraving area 22 is 3 to 10 um; the width of the through groove 241 of the transitional engraving area 23 is gradually narrowed from the carbon-coated area to its edge with the width of the through groove 241 of the normal engraving area 22 as the initial width. Preferably, the width of the through groove 241 of the normal engraving area 22 is 5 to 8 um.

[0060] Specifically, the width of the through groove 241 of the transitional engraving area 23 is initially the same as the width of the through groove 241 of the normal engraving area 22 and gradually changes, and the change direction gradually narrows from the carbon-coated area to the edge of the coating. Preferably, the through groove 241 may eventually disappear, and the mesh changes from the diamond-shaped holes of the through groove 241 to closed diamond-shaped holes.

[0061] In this embodiment, the engraved mesh 24 is a through groove 241 diamond or regular hexagon structure. The engraved mesh 24 includes mesh wall patterns of a normal engraving area 22 and a transitional engraving area 23. The hole shape of the normal engraving area 22 is a through groove 241 diamond, and the hole diameter 242 is uniform. The hole diameter 242 of the transitional area will gradually decrease, the hole wall 243 will become thicker, and the hole shape will also change from the through groove 241 diamond to a closed diamond.

[0062] In this embodiment, the width of the micro-gravure roller 20 is 1100-1450 mm. There are three normal coating areas 2 and six transition coating areas; each normal coating area is 330 mm wide and each transition coating area is 2 mm wide; the width of the blank area between adjacent coating areas is 20 mm. The remaining part is also the blank area.

[0063] In this embodiment, step S3 specifically includes the following steps:

[0064] Step S31, preparing a primer slurry, and transferring the primer slurry to the surface of the metal substrate 8 through the preset micro-gravure roller 20; wherein the amount of slurry in the normal coating area 2 is greater than the amount of slurry in the first edge transition area 3 and the second edge transition area 4;

[0065] Step S32: obtaining a carbon-coated foil 1 having a primer edge and an edge transition region by baking, and using the carbon-coated foil 1 as a positive electrode current collector or a negative electrode current collector.

[0066] Embodiment 2

[0067] The second embodiment is basically the same as the first embodiment, except that the active material in the present embodiment is grayish white in color, so the transition area of ​​the primer is set to grayish black, and the mesh depth of the transition engraving area 23 of the corresponding primer device gradually deepens, the hole wall 243 gradually narrows, the hole diameter 242 gradually increases, and the hole shape gradually changes from a closed rhombus to a through groove 241 rhombus.

[0068] Embodiment 3

[0069] The third embodiment is basically the same as the first embodiment, except that each coating area of ​​the carbon-coated foil 1 in the present embodiment requires only one transition area, and on the corresponding primer device, each engraving area has only one transition engraving area 23, and adapted thereto is that the coating process is positioned only by edge recognition on one side, and the position of the transition area is consistent with the edge recognition position.

[0070] Comparative Example 1

[0071] This comparative example is basically the same as Example 1, except that the coating area of ​​the carbon-coated foil 1 has no transition edge area, and is a normal coating area. The corresponding engraving process of the engraving area of ​​the primer device is completely consistent, and the hole type, hole diameter 242, and hole depth of the engraving area are exactly the same, and there is no gradual edge engraving design. The coating color of the finished carbon-coated foil 1 of this comparative example 1 is similar to the color of the active material in the coating process. It is impossible to accurately identify the edge online during coating. The edge recognition system frequently mistakenly identifies the edge of the active layer as the edge of the primer layer, causing coating jitter, and the insulating edge also shows obvious wavy lines when coated, and the produced electrode cannot meet the quality requirements.

[0072] Embodiment 4

[0073] The embodiment of the present invention provides a carbon-coated foil 1, which is prepared based on the above-mentioned method for preparing a carbon-coated foil pole piece. The technical effect produced by the carbon-coated foil 1 is the same as that of the first embodiment, and will not be described here.

[0074] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a carbon-coated foil pole piece, characterized in that: The preparation method comprises the following steps: Step S1, in the process of collecting the coating process of the positive electrode or negative electrode material of the battery, the coating appearance color is obtained by an online recognition device to determine the color identifiable range of the primer carbon coating area of ​​the coating process; wherein the carbon coating area includes a normal coating area and a first edge transition area and a second edge transition area arranged on opposite sides of the normal coating area; Step S2, engraving a preset micro-gravure roller adapted according to the coating process; Step S3, according to the type of the positive electrode or negative electrode material of the battery, select a matching primer slurry, and perform primer coating through the preset micro-gravure roller to obtain a carbon-coated foil with a preset recognizability at the edge; wherein the carbon-coated foil comprises a metal substrate and a carbon-coated layer coating two opposite sides of the metal substrate; the carbon-coated area corresponds to the carbon-coated layer; Step S4, coating the carbon-coated foil, performing online edge recognition on the first edge transition region and the second edge transition region corresponding to the carbon-coated layer, and coating active material in the recognition region to obtain a carbon-coated foil pole piece.

2. The method for preparing a carbon-coated foil pole piece according to claim 1, characterized in that: In step S1, the carbon-coated area also includes a first blank area and a second blank area arranged on the side of the first edge transition area and the second edge transition area away from the normal coating area; the total width of the carbon-coated area is designed according to the width of the battery electrode, the width of the first edge transition area and the second edge transition area are both 1 to 2 mm, and the width of the first blank area and the second blank area are designed according to the width of the battery electrode ear; the width of the normal coating area is 2 to 4 mm narrower than the total width of the coating area.

3. The method for preparing a carbon-coated foil pole piece according to claim 2, characterized in that: In step S2, the preset micro-gravure roller includes a gravure roller body and a plurality of engraving areas formed on the gravure roller body; each of the engraving areas includes a normal engraving area, two transition engraving areas arranged on opposite sides of the normal engraving area, and two blank areas arranged on a side of the transition engraving area away from the normal engraving area; the normal engraving area corresponds to the normal coating area, the two transition engraving areas respectively correspond to the first edge transition area and the second edge transition area, and the two blank areas respectively correspond to the first blank area and the second blank area.

4. The method for preparing a carbon-coated foil pole piece according to claim 3, characterized in that: The engraving area is provided with a plurality of engraving meshes; if the coating of the transition engraving area is required to be darker, the meshes of the transition engraving area are gradually enlarged.

5. The method for preparing a carbon-coated foil pole piece according to claim 4, characterized in that: The mesh depth of the engraving mesh in the normal engraving area is 15-50 um; the mesh depth of the engraving mesh in the transitional engraving area takes the mesh depth of the normal engraving area as the initial depth and gradually becomes shallower from the carbon-coated area toward its edge.

6. The method for preparing a carbon-coated foil pole piece according to claim 4, characterized in that: The thickness of the hole wall in the normal engraving area is 3-10 um; the thickness of the hole wall in the transitional engraving area starts from the thickness of the hole wall in the normal engraving area and gradually thickens from the carbon-coated area toward its edge.

7. The method for preparing a carbon-coated foil pole piece according to claim 4, characterized in that: The width of the through groove in the normal engraving area is 3-10 um; the width of the through groove in the transitional engraving area is initially the width of the through groove in the normal engraving area and gradually narrows from the carbon-coated area to its edge.

8. The method for preparing a carbon-coated foil pole piece according to claim 4, characterized in that: The engraved mesh is a through-groove rhombus or regular hexagonal structure.

9. The method for preparing a carbon-coated foil pole piece according to claim 4, characterized in that: The step S3 specifically comprises the following steps: Step S31, preparing a primer slurry, and transferring the primer slurry to the surface of the metal substrate through the preset micro-gravure roller; wherein the amount of slurry in the normal coating area is greater than or less than the amount of slurry in the first edge transition area and the second edge transition area; Step S32: obtaining a carbon-coated foil having a primer edge and an edge transition region by baking, and using the carbon-coated foil as a positive electrode current collector or a negative electrode current collector.

10. A carbon-coated foil, characterized in that: The carbon-coated foil is prepared based on the method for preparing a carbon-coated foil pole piece according to any one of claims 1 to 9.

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