A method of improving the winding of a pole piece spiral

Abstract

The application discloses a method for improving the winding spiral of a pole piece, comprising the following steps: before the pole piece is rolled, cutting the pole lug area of the pole piece, so that the pole lug area forms a plurality of cuts. The application also provides a full-pole lug pole piece. By using the method, the stress of the pole piece can be released at the cuts of the pole lug when the pole piece is rolled on a rolling machine, so that the surface of the pole piece is prevented from being curved during the rolling process, and the folding and spiral phenomena are avoided during the winding process of the pole piece; meanwhile, the round corners arranged at the ends of the cuts can prevent the pole piece from being torn and the belt from being broken during the winding process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery processing, in particular to a method for improving spiral winding of pole piece. BACKGROUND

[0002] There are various structures of battery cell, one of which is a cylindrical cell formed by winding a plurality of separators and positive and negative pole pieces alternately. For the cylindrical cell, the pole piece is generally prepared by the process of batching, coating, rolling, slitting, laser cutting and winding in each enterprise. Specifically, for the ordinary cell, after batching, coating, rolling and slitting, most of the tabs on the positive and negative pole pieces are cut off by laser intermittently, and only a small part is left as the tab of the battery. Or, the tabs are welded on the pole piece in an intermittent coating manner. For the full-tab cell, since the full tab needs to be reserved, laser cutting is not needed, and only the positive and negative pole pieces need to be processed accordingly. After the tabs are formed on the positive and negative pole pieces, the winding process is performed.

[0003] When the positive and negative pole pieces are prepared by the above process, since the stress is not completely released during the rolling of the pole piece, a curved surface will be generated on the surface of the pole piece after rolling. The existence of the curved surface will lead to the generation of spiral and wrinkle in the winding process of the pole piece, which will not only cause poor coating, lithium precipitation and other phenomena, but also cause safety risks. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for improving the spiral winding of the pole piece, which is simple, easy to operate, and can significantly improve the wrinkle and "spiral" phenomenon in the winding process of the pole piece.

[0005] In order to solve the above technical problem, the present application provides the following technical solution:

[0006] The present application provides a method for improving the spiral winding of the pole piece. Before the pole piece is rolled, the tab area of the pole piece is cut to form a plurality of cuts in the tab area.

[0007] In one embodiment of the present application, the method for improving the spiral winding of the pole piece comprises the following steps:

[0008] A metal foil is provided, and an active material slurry is coated on the middle part of the metal foil in the length direction, so that a material area and light foil areas on both sides of the material area are formed on the metal foil;

[0009] The material area is slitted from the middle part of the material area;

[0010] The light foil areas are cut to form a plurality of regularly distributed cuts in the light foil areas;

[0011] The material area is rolled and then wound.

[0012] In one embodiment of the present application, the plurality of cuts are arranged equidistantly along the length direction of the metal foil.

[0013] In one embodiment of the present application, the distance between two adjacent cuts is 300 mm.

[0014] In one embodiment of the present application, the cut is at an angle of 45° with the length direction of the metal foil.

[0015] In one embodiment of the present application, the width of the cut is 10 mm.

[0016] In one embodiment of the present application, the end of the cut is formed with a rounded corner.

[0017] In one embodiment of the present application, the light foil area is coated with a ceramic layer along the length direction near the material area.

[0018] The present application also provides a full-tab tab, comprising a metal foil, which is wound into a roll along the length direction; the metal foil is coated with an active material slurry along the length direction to form a material area, one side of the material area is a light foil area, and a plurality of cuts are formed regularly along the length direction on the light foil area.

[0019] In one embodiment of the present application, the plurality of cuts are arranged equidistantly along the length direction of the metal foil, the cut is at an angle of 45° with the length direction of the metal foil, and the end of the cut is formed with a rounded corner.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1. In the present application, the tab is first cut by laser to form a plurality of cuts before rolling, and the stress of the tab itself can be released at the tab cut during subsequent rolling on the rolling machine, thereby avoiding the generation of a curved surface on the surface of the tab during rolling, and improving the wrinkles and spiral phenomenon generated during the winding process of the tab.

[0022] 2. In the present application, the end of the tab cut is cut to form a rounded corner, which can prevent tearing and belt breaking during the winding process of the tab.

[0023] 3. After the positive tab and the negative tab are wound, they are transferred to the rubbing process. In the present application, the aluminum scraps generated after the positive tab is treated by cutting the tab and then rubbed by spinning are significantly less than those of the battery without cutting the tab, and the wrinkles generated at the connection between the tab and the auxiliary material on the positive tab are also less.

[0024] 4. In this invention, after the positive electrode sheet undergoes laser tab cutting, it has a larger internal space, higher liquid injection efficiency, and higher wetting efficiency compared to the battery cell that has not undergone tab cutting. Attached Figure Description

[0025] Figure 1 A state diagram of a wound battery cell formed after the positive electrode sheet is wound using existing processes;

[0026] Figure 2 This is a schematic diagram of the structure of the positive electrode sheet prepared in an embodiment of the present invention;

[0027] Figure 3 This is a state diagram of a wound cell formed after the positive electrode sheet prepared by the method of the present invention is wound.

[0028] The components are: 1. Metal foil; 2. Material area; 3. Light foil area; 4. Ceramic layer; 5. Cutout; 6. Rounded corner; 7. Tab. Detailed Implementation

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] As described in the background section, in existing technologies, the preparation of electrode sheets generally employs a process of material preparation, coating, rolling, slitting, laser cutting, and winding. That is, after material preparation, coating, rolling, and slitting, most of the tabs on the positive and negative electrode sheets are cut off intermittently and at equal intervals using a laser, leaving only a small portion as the battery tabs; or an intermittent coating method is used to weld tabs at equal intervals onto the electrode sheets. In the positive electrode sheet, stress is not completely released during rolling, resulting in a curved surface after rolling, and spirals and wrinkles are generated during winding. (See attached...) Figure 1 As shown, after winding, each loop of the electrode tab is not on the same horizontal plane, similar to a gyroscope, resulting in the aforementioned "spiral" phenomenon. This not only leads to poor electrode coating and lithium plating, but also poses safety risks.

[0031] To address this technical problem, this invention provides a method for improving the spiral winding of electrode sheets. The original process flow is modified from batching, coating, rolling, slitting, laser cutting, and winding to a process flow of batching, coating, slitting, laser cutting, rolling, and winding. This improves the wrinkling and "spiral" phenomenon during electrode winding. The method is described in detail below.

[0032] During the rolling process of the pole piece, the incomplete stress release of the pole piece is the main cause of the "spiral" phenomenon during winding. Based on this, in the present application, the tab area of the pole piece is cut before the pole piece is rolled, so that the tab area forms a plurality of cuts. In the present application, "a plurality of" means at least one, for example, it can be 5, 10, 15, 20, etc. The existence of the cut can fully release the stress of the pole piece during the rolling process, thereby improving the "spiral" phenomenon during winding.

[0033] Specifically, the method for improving the winding spiral of the pole piece comprises the following steps:

[0034] A metal foil 1 is provided, and active material slurry is coated on the middle part of the metal foil 1 along the length direction, so that a material area 2 and light foil areas 3 located on both sides of the material area 2 are formed on the metal foil 1;

[0035] The material area 2 is slitted from the middle part of the material area 2;

[0036] The light foil areas 3 are cut, so that the light foil areas 3 form a plurality of regularly distributed cuts 5;

[0037] The material area 2 is rolled, and then wound.

[0038] In the present application, the pole piece is a positive pole piece. As a preferred embodiment of the present application, the metal foil 1 is an aluminum foil, and the active material slurry comprises one or more positive active materials such as lithium cobaltate, ternary lithium, lithium iron phosphate, lithium manganate, etc. The aluminum foil is easy to process, has good mechanical properties, and is soft in texture and good in ductility, which can ensure that the pole piece does not break during winding, and has good electrical conductivity and thermal conductivity, and is therefore suitable as a positive current collector. The active materials such as lithium cobaltate, ternary lithium, lithium iron phosphate or lithium manganate have high energy density, power density, good cycle performance and reliable safety performance. These positive active materials are mixed with binders, conductive agents, etc. to form a positive active slurry, which is coated on the surface of the aluminum foil, and after drying, the positive pole piece is obtained by rolling and slicing.

[0039] In the present application, the material area 2 is the area coated with the positive active slurry, and the light foil area 3 is the area not coated with the positive active slurry. As a preferred embodiment of the present application, the shape of the material area 2 is rectangular, which not only facilitates coating, but also ensures that the material area 2 is immersed in the electrolyte during operation.

[0040] As a preferred embodiment of the present application, when the active material slurry is coated to form the material area 2, a ceramic layer 4 can also be coated on both sides of the material area 2. The existence of the ceramic layer 4 occupies a part of the position of the light foil area 3, which reduces the short circuit rate. In a preferred embodiment, the raw material of the ceramic layer 4 is boehmite.

[0041] In this invention, after the coating process, a slitting process is performed from the middle of the material area 2, thereby cutting the metal foil 1 along its length from the middle of the material area 2 to obtain two electrode sheets of identical size, wherein each electrode sheet has a material area 2 and a foil area 3 located on one side of the material area 2. (See attached diagram) Figure 2 As shown, in a preferred embodiment, after slitting, the width of the electrode sheet is 196.5 mm, the width of the material area 2 is 185 mm, the width of the ceramic layer 4 is 4 mm, and the width of the foil area 3 is 7.5 mm.

[0042] In this invention, after the slitting process, the foil area 3 of the electrode sheet is cut to form multiple slits 5, thereby forming multiple tabs 7 in the foil area 3. The presence of the slits 5 releases the stress on the electrode sheet during rolling. Preferably, laser cutting is used. Compared to other cutting methods, laser cutting is more precise, the shape of the slit is easier to control, and the slit is smoother, avoiding burrs or curling at the slit.

[0043] In a preferred embodiment of the present invention, the plurality of slits 5 are arranged at equal intervals along the length of the metal foil 1. The equidistant arrangement of the slits 5 can fully release the stress generated in each area of ​​the electrode sheet during the rolling process, ensuring the flatness of the electrode sheet after rolling and avoiding the "spiral" phenomenon during the winding process.

[0044] In this invention, the distance between two adjacent cuts 5 should be neither too large nor too small. If the distance is too large, it will affect the stress release effect of the electrode; if the distance is too small, it will reduce the amount of tabs and affect the current flow effect of the tabs. In a preferred embodiment of this invention, the distance between two adjacent cuts 5 is 300 mm.

[0045] In this invention, the width of the cut 5 must be neither too large nor too small. If the width of the cut 5 is too small, the stress-relieving effect will be insignificant; if the width of the cut 5 is too large, it will reduce the area of ​​the electrode tab and affect the conductivity of subsequent current. In a preferred embodiment of this invention, the width of the cut is 10 mm.

[0046] In this invention, the clamping angle between the cut 5 and the length direction of the metal foil 1 is α, preferably an acute angle, which better releases the stress on the electrode. The acute angle can be 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc. In a preferred embodiment, the cut 5 forms a 45° angle with the length direction of the metal foil 1; this clamping angle maximizes stress release and avoids a "spiral" phenomenon.

[0047] In a preferred embodiment of the present invention, the end of the cut 5 is rounded 6. The rounded corner 6 can be easily formed by laser cutting. Please refer to the appendix. Figure 2The round corner 6 can reach the area where the ceramic layer 4 is located. In the present application, by setting the round corner 6 at the end of the cut 5, the tearing and breaking of the tab during winding can be prevented.

[0048] Figure 3 A schematic diagram of a wound cell formed by winding the positive tab prepared by the method of the present application. As can be seen from the diagram, the tab ears of each turn of the positive tab are in the same horizontal plane after winding, i.e. the "spiral" phenomenon during winding is improved.

[0049] After the winding process, the positive tab and the negative tab will be transferred to the rubbing process. In the present application, since the positive tab has been treated by cutting the tab ears, the amount of aluminum scraps produced after the spinning rubbing process is significantly less than that of the cell without cutting the tab ears, and the wrinkles at the connection between the tab ears and the auxiliary materials on the positive tab are also less.

[0050] By the above method of the present application, a full-tab positive tab can be prepared, which has regularly arranged cuts on the tab ears. Such full-tab positive tab will not produce the "spiral" phenomenon during winding, and can avoid the phenomena of poor coating, lithium precipitation, etc., and is safer. Such full-tab positive tab can be further prepared into a full-tab cell together with the separator, the negative tab and the electrolyte. Compared with the cell without cutting the tab ears, the internal space of such cell is larger, the injection efficiency is higher, and the infiltration efficiency is also higher.

[0051] The above-described embodiments are only preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Any equivalent substitutions or transformations made by those skilled in the art based on the present application are within the protection scope of the present application. The protection scope of the present application is subject to the claims.

Claims

1. A full tab, characterized by, The metal foil is coated with active material paste along the length direction to form a material area, and one side of the material area is a light foil area, and a plurality of regularly distributed cuts are formed on the light foil area along the length direction. The preparation of the full-tab tab includes the following steps: A metal foil is provided, and active material paste is coated on the middle part of the metal foil along the length direction to form a material area and light foil areas on both sides of the material area; The material area is divided into strips from the middle part of the material area; The light foil areas are cut to form a plurality of regularly distributed cuts, the cuts are at an angle of 45° with the length direction of the metal foil, the width of the cuts is 10 mm, the ends of the cuts are formed with rounded corners, and the distance between adjacent two cuts is 300 mm; The material area is rolled and then wound.

2. The full tab sheet according to claim 1, characterized by, The light foil area is coated with a ceramic layer along the length direction near the material area.

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