Electrode sheet preparation method, electrode sheet, and battery cell

Abstract

The present application discloses an electrode sheet preparation method, an electrode sheet, and a battery cell. In the electrode sheet preparation method, the surface of a current collector is coated with alternately arranged long film surfaces (i.e., first coating regions and third coating regions) and short film surfaces (i.e., second coating regions and fourth coating regions), recesses are formed on the boundary lines between adjacent long film surfaces and short film surfaces, and during subsequent slitting, slitting lines pass through the recesses, so that residual strip material regions between the recesses and the edges of electrode sheets obtained after slitting can be avoided, and the recesses at the tails of the electrode sheets obtained after slitting can be avoided, it can be guaranteed that a subsequent battery cell winding structure is correct, the preparation process of an electrode sheet can be simplified, the quality of the electrode sheet is guaranteed, and the flatness and safety performance of the wound battery cell are improved.

Description

A method for preparing a pole piece, a pole piece and a battery cell Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a method for preparing a pole piece, a pole piece, and a battery cell. Background Art

[0002] With the development of consumer electronics and new energy vehicles, the demand for lithium-ion battery energy density is gradually increasing. In a tab-centering structure, the tab is typically placed in the middle of the active material layer, forming an embedded tab to improve energy density.

[0003] In the related art, the active material is first coated on the current collector to form a large electrode sheet, and then the active layer is removed by scraping or laser cleaning according to the predetermined cutting position on the large electrode sheet to make a slot for welding the electrode ear, and finally the large electrode sheet is cut into multiple electrode sheets. Ideally, the edges of the slots should all be located on the cutting line, but due to the inevitable process fluctuations in the manufacturing process of the electrode sheet, for example, there are processing errors in the position and size of the slots, and there are position errors in the installation of the cutting tool, etc., which makes it almost impossible for the cutting position to completely fit the edge of the electrode ear welding slot. This may lead to the following two situations:

[0004] 1. There is a strip area with an active material layer between the edge of the slot and the cutting line. This strip area needs to be removed by die cutting. However, removing the strip area will cause a gap in the electrode. During the subsequent winding process of the electrode, the presence of the gap will easily lead to electrode breakage and diaphragm wrinkling, and the unevenness of the battery cell after winding will increase. If the strip area is not die-cut, it will not be possible to reduce the thickness of the battery cell and increase the energy density.

[0005] 2. The slitting line passes through the slots, so that some slots are located at the tail of the adjacent pole piece. Some slots at the tail of the pole piece will increase the unevenness of the battery cell after winding, and there is a risk of foil leakage in these slots, which may cause the battery cell to short-circuit and affect the safety performance of the battery cell. To avoid short-circuiting of the battery cell, it is necessary to stick adhesive tape on some slots at the tail of the pole piece. On the one hand, it will increase material costs and complicate the process. On the other hand, when the size of some slots at the tail of the pole piece is small, it is not convenient to stick adhesive tape.

[0006] In summary, the electrode preparation method in the related art has defects, which may lead to problems in the subsequent battery cell preparation process, and may also cause problems such as increased unevenness or reduced safety performance in the finished battery cells.

[0007] Summary of the Invention

[0008] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a method for preparing a pole piece that can avoid the residual strip area between the slot and the edge of the pole piece after slitting, and can also avoid the presence of a slot at the end of the pole piece after slitting. It can also ensure the correct winding structure of the subsequent battery cell, which is conducive to streamlining the pole piece preparation process, ensuring the quality of the pole piece, and improving the flatness and safety performance of the wound battery cell.

[0009] This application also proposes a pole piece.

[0010] The present application also proposes a battery cell comprising the above-mentioned electrode.

[0011] The first embodiment of the present application provides a method for preparing a pole piece, comprising the steps of:

[0012] Taking or preparing a current collector, the current collector having an alignment portion, the current collector having a first side and a second side opposite to each other along a thickness direction thereof;

[0013] Applying active material to the first side to form a plurality of first coating regions and a plurality of second coating regions extending along the length direction of the current collector on the first side, wherein the plurality of first coating regions and the plurality of second coating regions are alternately arranged along the width direction of the current collector, one end of the plurality of first coating regions is aligned with one end of the plurality of second coating regions at the alignment position, and the length of the first coating region is greater than the length of the second coating region;

[0014] Dividing a plurality of the first coating areas and a plurality of the second coating areas into a plurality of first coating area groups arranged along the width direction of the current collector, wherein the first coating area group includes one first coating area and an adjacent second coating area, and in the first coating area group, removing a portion of the coating to form a first groove, so that a boundary line between the first coating area and the second coating area passes through the first groove;

[0015] Applying active material to the second side to form a plurality of third coating regions and a plurality of fourth coating regions extending along the length direction of the current collector on the second side, wherein the plurality of third coating regions and the plurality of fourth coating regions are alternately arranged along the width direction of the current collector, one end of the plurality of third coating regions is aligned with one end of the plurality of fourth coating regions at the alignment position, the length of the third coating region is the same as the length of the first coating region, the length of the fourth coating region is the same as the length of the second coating region, the width of the third coating region is the same as the width of the first coating region, the width of the fourth coating region is the same as the width of the second coating region, and the second coating region is opposite to each of the third coating regions, and the first coating region is opposite to each of the fourth coating regions;

[0016] Dividing the plurality of third coating areas and the plurality of fourth coating areas into a plurality of second coating area groups arranged along the width direction of the current collector, wherein the second coating area group includes one third coating area and an adjacent fourth coating area, and in the second coating area group, removing a portion of the coating to form a second groove, so that the boundary line between the third coating area and the fourth coating area passes through the second groove, and in a projection perpendicular to the current collector, the second groove coincides with the first groove;

[0017] The first coating area and the second coating area are cut along the boundary line between the adjacent pole pieces to form a plurality of pole pieces. Each of the first slots and each of the second slots is cut into two pole tab slots provided on two adjacent pole pieces. The pole tab slots are used to connect pole tabs.

[0018] The electrode preparation method provided in the first embodiment of the present application has at least the following beneficial effects:

[0019] The surface of the current collector is coated with alternating long film surfaces (i.e., the first coating area and the third coating area) and short film surfaces (i.e., the second coating area and the fourth coating area), and grooves are made on the dividing lines between adjacent long film surfaces and short film surfaces. During subsequent cutting, the cutting line passes through the grooves, which can avoid residual material areas between the grooves and the edges of the pole pieces after cutting, and can avoid the appearance of grooves at the tail of the pole pieces after cutting. It can also ensure that the subsequent winding structure of the battery cell is correct, which is conducive to streamlining the preparation process of the pole pieces, ensuring the quality of the pole pieces, and improving the flatness and safety performance of the battery cell after winding.

[0020] In some embodiments of the present application, the first slot is symmetrical about the boundary line between the first coating area and the second coating area, and the second slot is symmetrical about the boundary line between the third coating area and the fourth coating area.

[0021] In some embodiments of the present application, the pole piece preparation method further includes the steps of:

[0022] Before cutting along the boundary line between the adjacent first coating area and the second coating area, a portion of the coating is removed in the first coating area group to form a third slot, so that the boundary line between the first coating area and the second coating area passes through the third slot, and the third slot is spaced apart from the first slot in the length direction of the current collector; after cutting along the boundary line between the adjacent first coating area and the second coating area to form a plurality of electrode sheets, each of the third slots is divided into two avoidance slots provided on two adjacent electrode sheets, and the avoidance slots are used to avoid the tabs of the other electrode sheet;

[0023] and / or,

[0024] Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the second coating area group, part of the coating is removed to form a fourth slot, so that the boundary line between the third coating area and the fourth coating area passes through the fourth slot, and the fourth slot and the second slot are spaced apart in the length direction of the collector; after the cutting is performed along the boundary line between the adjacent first coating area and the second coating area to form a plurality of pole pieces, each of the fourth slots is divided into two avoidance slots provided on two adjacent pole pieces.

[0025] In some embodiments of the present application, the third slot is symmetrical about the boundary line between the first coating area and the second coating area; the fourth slot is symmetrical about the boundary line between the third coating area and the fourth coating area.

[0026] In some embodiments of the present application, before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, part of the coating is removed in the first coating area group to form the third slot, and part of the coating is removed in the second coating area group to form the fourth slot; in the projection perpendicular to the current collector, the fourth slot coincides with the third slot, or the fourth slot is staggered with the third slot.

[0027] In some embodiments of the present application, the pole piece preparation method further includes the steps of:

[0028] Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, a portion of the coating is removed in the first coating area group to form a third slot and a fourth slot, so that the boundary line between the first coating area and the second coating area passes through the third slot and the fourth slot, and the first slot, the third slot, and the fourth slot are sequentially spaced apart in the length direction of the current collector;

[0029] or,

[0030] Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the second coating area group, part of the coating is removed to form a third slot and a fourth slot, so that the boundary line between the third coating area and the fourth coating area passes through the third slot and the fourth slot, and the second slot, the third slot and the fourth slot are arranged in sequence at intervals in the length direction of the collector.

[0031] In some embodiments of the present application, the pole piece preparation method further includes the steps of:

[0032] Coating a first insulating layer at an edge of a portion of the first coating area that exceeds the second coating area along the length direction of the current collector, wherein the first insulating layer partially covers the first coating area and the remaining portion covers the exposed current collector;

[0033] A second insulating layer is coated on the edge of the portion of the third coating area that exceeds the fourth coating area along the length direction of the current collector. The second insulating layer partially covers the third coating area and the remaining portion covers the exposed current collector.

[0034] In some embodiments of the present application, the material of the first insulating layer and the second insulating layer is ceramic.

[0035] In some embodiments of the present application, the pole piece preparation method further includes the steps of:

[0036] Applying active material to the first side to form a first extension area on the first side extending along the length direction of the current collector, wherein a plurality of the first coating areas and a plurality of the second coating areas together constitute a first region, and the first extension areas are provided on both sides of the first region in the width direction of the current collector;

[0037] Applying active material to the second side to form a second extended area extending along the length direction of the current collector on the second side, wherein a plurality of the third coated areas and a plurality of the fourth coated areas together constitute a second region, and the second extended areas are provided on both sides of the second region in the width direction of the current collector;

[0038] A first extension area is adjacent to a first coating area and has the same length as the first coating area, a second extension area is adjacent to a fourth coating area and has the same length as the fourth coating area, and is cut along the boundary line between the first extension area and the first coating area; a first extension area is adjacent to a second coating area and has the same length as the second coating area, a second extension area is adjacent to a third coating area and has the same length as the third coating area, and is cut along the boundary line between the first extension area and the second coating area.

[0039] In some embodiments of the present application, the active material is one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and a ternary material.

[0040] A second embodiment of the present application provides a pole piece, comprising:

[0041] current collector;

[0042] a first active layer covering one side of the current collector in the thickness direction and having the same width as the current collector;

[0043] a second active layer covering the other side of the current collector in the thickness direction and having the same width as the current collector; the first active layer and the second active layer both have a tab groove, one side edge of the tab groove coincides with one side edge of the current collector in the width direction, the current collector is exposed at the tab groove, and in a projection perpendicular to the current collector, the tab groove of the second active layer coincides with the tab groove of the first active layer, one of the tab grooves is used to accommodate a tab, one end of the second active layer is aligned with one end of the first active layer, the length of the second active layer is less than the length of the first active layer, so that part of the current collector is exposed on the side where the second active layer is located to form a hollow foil area;

[0044] The insulating layer at least covers one side of the empty foil area in the width direction of the current collector.

[0045] The second embodiment of the present application provides a pole piece having at least the following beneficial effects:

[0046] The pole piece provided in the second embodiment of the present application can be made by the pole piece preparation method provided in the first embodiment of the present application, and the surface of the current collector is coated with alternating long film surfaces (i.e., the first coating area and the third coating area) and short film surfaces (i.e., the second coating area and the fourth coating area), and grooves are made on the boundary line between the adjacent long film surfaces and the short film surfaces. During subsequent slitting, the slitting line passes through the grooves, which can avoid residual material areas between the grooves and the edge of the pole piece after slitting, and can avoid the appearance of grooves at the tail of the pole piece after slitting, and can also ensure the correct winding structure of the subsequent battery cell, which is conducive to streamlining the preparation process of the pole piece, ensuring the quality of the pole piece, and improving the flatness and safety performance of the wound battery cell; before slitting, Along the length direction of the current collector, an insulating layer with a certain width is coated on the edge of the part where the long film surface exceeds the short film surface, and then cutting is performed. The insulating layer with a certain width can allow the cutting line to be offset within a certain range. As long as the cutting line is ensured to pass through the insulating layer, it can be cut to form a pole piece with an insulating layer covering at least one side of the empty foil area in the width direction of the current collector. When the cutting position fluctuates, resulting in the active material of one pole piece remaining in the empty foil area of ​​the adjacent pole piece, the insulating layer can cover the remaining active material; when the cutting position fluctuates, resulting in the empty foil area of ​​one pole piece remaining in the active material area of ​​the adjacent pole piece, the insulating layer can cover the remaining empty foil area, thereby ensuring the performance of the pole piece.

[0047] In some embodiments of the present application, the first active layer and / or the second active layer has an air avoidance groove, one side edge of the air avoidance groove coincides with one side edge of the current collector in its width direction, the air avoidance groove and the pole tab groove are located on the same side of the current collector in the width direction, the air avoidance groove and the pole tab groove are spaced apart along the length direction of the current collector, and the air avoidance groove is used to avoid the pole tab of another pole sheet after winding.

[0048] In some embodiments of the present application, the first active layer or the second active layer has two spaced-apart air-avoidance grooves, one side edge of the air-avoidance groove coincides with one side edge of the current collector in its width direction, the air-avoidance groove and the pole tab groove are located on the same side of the current collector in the width direction, the air-avoidance groove and the pole tab groove are spaced-apart along the length direction of the current collector, and the air-avoidance groove is used to avoid the pole tab of the other pole sheet after winding.

[0049] In some embodiments of the present application, the air avoidance groove includes a first recess and a second recess that are connected in sequence along the thickness direction of the current collector, the second recess is recessed from the bottom wall of the first recess toward the current collector, one side edge of the second recess and one side edge of the first recess both coincide with one side edge of the current collector in its width direction, the cross-sectional area of ​​the second recess is smaller than the cross-sectional area of ​​the first recess, and the second recess is used to correspond to the pole ear.

[0050] In some embodiments of the present application, the width of the insulating layer is less than or equal to 1 mm.

[0051] In some embodiments of the present application, the width of the insulating layer is 0.1 mm.

[0052] In some embodiments of the present application, the thickness of the insulating layer is less than or equal to the thickness of the first active layer.

[0053] A third embodiment of the present application provides a battery cell, including:

[0054] Extreme ears;

[0055] The electrode sheet provided by any embodiment of the second aspect of the present application, the electrode tab is connected to the electrode tab groove of the electrode sheet, and the electrode sheet is wound to form the battery core.

[0056] The battery cell provided in the third embodiment of the present application has at least the following beneficial effects:

[0057] The battery cell provided in the third aspect embodiment of the present application includes the electrode provided in the second aspect embodiment of the present application, and the electrode is made by the electrode preparation method provided in the first aspect embodiment of the present application. In the electrode preparation method, alternating long film surfaces (i.e., the first coating area and the third coating area) and short film surfaces (i.e., the second coating area and the fourth coating area) are coated on the surface of the current collector, and grooves are made on the dividing line between adjacent long film surfaces and short film surfaces. During subsequent cutting, the cutting line passes through the grooves, which can avoid residual material areas between the grooves and the edges of the electrode after cutting, and can avoid the appearance of grooves at the tail of the electrode after cutting. It can also ensure that the winding structure of the subsequent battery cell is correct, which is conducive to streamlining the preparation process of the electrode, ensuring the quality of the electrode, and improving the flatness and safety performance of the battery cell after winding.

[0058] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present application is further described below with reference to the accompanying drawings and embodiments, wherein:

[0060] FIG1 is a schematic diagram of a method for preparing a pole piece in the related art under ideal conditions;

[0061] FIG2 is a schematic diagram showing a stripped area between the edge of the slot and the cutting line in a method for preparing a pole piece in the related art;

[0062] FIG3 is a schematic diagram of a cutting line passing through a slot in a method for preparing a pole piece in the related art;

[0063] FIG4 is a schematic diagram of the process for preparing a pole piece according to an embodiment of the first aspect of the present application after coating the active material on the first side of the current collector;

[0064] FIG5 is a schematic diagram of the process for preparing a pole piece according to an embodiment of the first aspect of the present application after coating the active material on the second side of the current collector;

[0065] 6 is a schematic diagram of a method for preparing a pole piece according to an embodiment of the first aspect of the present application after a first slot and a third slot are formed on a first side of a current collector;

[0066] 7 is a schematic diagram of a method for preparing a pole piece according to an embodiment of the first aspect of the present application after a second slot and a fourth slot are formed on the second side of the current collector;

[0067] FIG8 is a schematic diagram of a method for preparing a pole piece after a first insulating layer is formed on a first side of a current collector in an embodiment of the first aspect of the present application;

[0068] FIG9 is a schematic diagram of the electrode sheet preparation method according to the embodiment of the first aspect of the present application after the second insulating layer is formed on the second side of the current collector;

[0069] FIG10 is a schematic diagram of a pole piece on a first side of a current collector provided by an embodiment of the second aspect of the present application, as shown at B1 in FIG6 and FIG7 ;

[0070] FIG11 is a schematic diagram of the electrode shown in FIG10 on the second side of the current collector;

[0071] FIG12 is a side view of the pole piece shown in FIG10;

[0072] FIG13 is a schematic diagram of the cooperation between the air-avoiding groove of the pole piece shown in FIG10 and another pole piece;

[0073] FIG14 is a schematic diagram of a pole piece preparation method according to other embodiments of the first aspect of the present application after a first insulating layer is formed on the first side of the current collector;

[0074] FIG15 is a schematic diagram of a method for preparing a pole piece according to other embodiments of the first aspect of the present application after a second insulating layer is formed on the second side of the current collector;

[0075] FIG16 is a schematic diagram of a pole piece on a first side of a current collector provided by an embodiment of the second aspect of the present application, as shown at B2 in FIG14 and FIG15 ;

[0076] FIG17 is a schematic diagram of the electrode shown in FIG16 on the second side of the current collector;

[0077] FIG18 is a schematic diagram of the cooperation between the air-avoiding groove of the pole piece shown in FIG16 and another pole piece;

[0078] FIG19 is a schematic diagram of a pole piece on a first side of a current collector provided by an embodiment of the second aspect of the present application, as shown at C2 in FIG14 and FIG15 ;

[0079] FIG20 is a schematic diagram of the electrode shown in FIG19 on the second side of the current collector;

[0080] FIG21 is a schematic diagram of the cooperation between the air-avoiding groove of the pole piece shown in FIG19 and another pole piece;

[0081] FIG22 is a schematic diagram of the coordination between the air-avoiding groove of one electrode piece and another electrode piece prepared by the electrode piece preparation method provided in some other embodiments of the first aspect of the present application;

[0082] FIG23 is a schematic diagram of the coordination between the air-avoiding groove of another electrode piece and another electrode piece prepared by the electrode piece preparation method provided in some other embodiments of the first aspect of the present application;

[0083] FIG24 is a schematic diagram of a method for preparing a pole piece according to still other embodiments of the first aspect of the present application after a first insulating layer is formed on the first side of a current collector;

[0084] FIG25 is a schematic diagram of a pole piece on a first side of a current collector provided by an embodiment of the second aspect of the present application shown at B3 in FIG24 ;

[0085] FIG26 is a schematic diagram of the cooperation between the air-avoiding groove of the pole piece shown in FIG25 and another pole piece;

[0086] FIG27 is a schematic diagram of a pole piece on a first side of a current collector provided by an embodiment of the second aspect of the present application, as shown at C3 in FIG24 ;

[0087] FIG28 is a schematic diagram of the coordination between the air-avoiding groove of the pole piece shown in FIG27 and another pole piece;

[0088] FIG29 is a schematic diagram of the cooperation between the air-avoiding groove of a pole piece and another pole piece provided in some embodiments of the second aspect of the present application;

[0089] FIG30 is a front view of the air avoidance groove shown in FIG29.

[0090] Figure markings: current collector 100, 100', alignment point 110, first side 130, second side 140, first area 200, first coating area group 210, first coating area 211, second coating area 212, first slot 220, 220', third slot 230, second area 300, second coating area group 310, third coating area 311, fourth coating area 312, second slot 320, fourth slot 330, pole piece 400, pole ear groove 410, air avoidance groove 420, first recess 421, second recess 422, first insulating layer 500, second insulating layer 600, first extension area 700, second extension area 800, pole ears 900, 900", protective tape 910, 910". DETAILED DESCRIPTION

[0091] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0092] In the description of this application, it should be understood that descriptions involving orientation, such as up, down, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0093] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0094] Throughout the description of this application, reference to terms such as "one embodiment" or "some embodiments" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of this application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0095] With the development of consumer electronics and new energy vehicles, the demand for lithium-ion battery energy density is gradually increasing. In a tab-centering structure, the tab is typically placed in the middle of the active material layer, forming an embedded tab to improve energy density.

[0096] In the related art, the active material is first coated on the current collector 100' to form a large electrode sheet, and then the active layer is removed by scraping or laser cleaning according to the predetermined cutting position on the large electrode sheet to produce the first slot 220' for welding the electrode ear, and finally the large electrode sheet is cut into multiple electrode sheets. Ideally, referring to Figure 1, the first slots 220' should all be located on the cutting line, but due to the inevitable process fluctuations in the manufacturing process of the electrode sheet, for example, there are machining errors in the position and size of the first slot 220', and there are position errors in the installation of the cutting tool, etc., resulting in the cutting position being almost unable to completely fit at the edge of the first slot 220'. This may result in the following two situations:

[0097] 1. Referring to FIG. 2 , there is a stripped area with an active material layer between the edge of the first slot 220 ′ and the cutting line. The stripped area needs to be removed by die-cutting. However, removing the stripped area will cause a gap in the electrode sheet. During the subsequent electrode sheet winding process, the presence of the gap will easily cause the electrode sheet to break and the diaphragm to wrinkle. Moreover, the unevenness of the battery cell after winding will increase. If the stripped area is not die-cut, it will not be possible to reduce the thickness of the battery cell and increase the energy density.

[0098] 2. Referring to Figure 3, the cutting line passes through the first slot 220', so that part of the first slot 220' is located at the tail of the adjacent pole piece. The part of the first slot 220' located at the tail of the pole piece will cause the unevenness of the battery cell to increase after the winding is completed, and there is a risk of foil leakage in this part of the first slot 220', which may cause the battery cell to short circuit and affect the safety performance of the battery cell; if the battery cell short circuit is to be avoided, it is necessary to affix adhesive tape to part of the first slot 220' at the tail of the pole piece. On the one hand, it will lead to increased material costs and complicated processes. On the other hand, when the size of the part of the first slot 220' at the tail of the pole piece is small, it is not convenient to affix adhesive tape.

[0099] In summary, the electrode preparation method in the related art has defects, which may lead to problems in the subsequent battery cell preparation process, and may also cause problems such as increased unevenness or reduced safety performance in the finished battery cells.

[0100] Based on this, referring to Figures 4 to 9, it should be noted that in Figures 4 to 9, along the width direction of the current collector 100, A1, B1, C1, D1, E1, and F1 are used as the codes for the multiple electrode pieces 400 after cutting. The first embodiment of the present application provides a method for preparing an electrode piece, comprising the steps of:

[0101] A current collector 100 is obtained or prepared, wherein the current collector 100 has an alignment portion 110 and a first side 130 and a second side 140 opposite to each other along a thickness direction of the current collector 100;

[0102] 4 , the active material is coated on the first side 130 to form a plurality of first coating regions 211 and a plurality of second coating regions 212 extending along the length direction of the current collector 100 on the first side 130 . The plurality of first coating regions 211 and the plurality of second coating regions 212 are alternately arranged along the width direction of the current collector 100 . One end of the plurality of first coating regions 211 is aligned with one end of the plurality of second coating regions 212 at an alignment point 110 . The length of the first coating region 211 is greater than the length of the second coating region 212 .

[0103] 6 , the plurality of first coating regions 211 and the plurality of second coating regions 212 are divided into a plurality of first coating region groups 210 arranged along the width direction of the current collector 100 . The first coating region group 210 includes a first coating region 211 and an adjacent second coating region 212 . In the first coating region group 210 , a portion of the coating is removed to form a first groove 220 , so that the boundary between the first coating region 211 and the second coating region 212 passes through the first groove 220 .

[0104] 5 , an active material is coated on the second side 140 to form a plurality of third coating regions 311 and a plurality of fourth coating regions 312 extending along the length direction of the current collector 100 on the second side 140 . The plurality of third coating regions 311 and the plurality of fourth coating regions 312 are alternately arranged along the width direction of the current collector 100 . One end of the plurality of third coating regions 311 is aligned with one end of the plurality of fourth coating regions 312 at an alignment point 110 . The length of the third coating region 311 is the same as the length of the first coating region 211 , the length of the fourth coating region 312 is the same as the length of the second coating region 212 , the width of the third coating region 311 is the same as the width of the first coating region 211 , and the width of the fourth coating region 312 is the same as the width of the second coating region 212 . The second coating region 212 is located opposite each third coating region 311 , and the first coating region 211 is located opposite each fourth coating region 312 .

[0105] 7 , the plurality of third coating areas 311 and the plurality of fourth coating areas 312 are divided into a plurality of second coating area groups 310 arranged along the width direction of the current collector 100. The second coating area group 310 includes a third coating area 311 and an adjacent fourth coating area 312. In the second coating area group 310, a portion of the coating is removed to form a second groove 320. The boundary between the third coating area 311 and the fourth coating area 312 passes through the second groove 320. In a projection perpendicular to the current collector 100, the second groove 320 coincides with the first groove 220.

[0106] 8 and 9 , the dotted lines are cutting lines, and the electrode pieces 400 are cut along the boundary line between the adjacent first coating area 211 and the second coating area 212 . Referring to FIG. 10 to FIG. 12 , each first slot 220 and each second slot 320 are cut into two tab slots 410 provided on two adjacent electrode pieces 400 .

[0107] The surface of the current collector 100 is coated with alternating long film surfaces (i.e., the first coating area 211 and the third coating area 311) and short film surfaces (i.e., the second coating area 212 and the fourth coating area 312), and grooves (i.e., the first groove 220 and the second groove 320) are made on the dividing line between the adjacent long film surfaces and the short film surfaces. During subsequent cutting, the cutting line passes through the grooves, which can avoid residual material areas between the grooves and the edges of the pole pieces 400 after cutting, and can also avoid the appearance of grooves at the tails of the pole pieces 400 after cutting. Moreover, the positions of the pole ear grooves 410 of the multiple pole pieces 400 formed after cutting are the same, and can also ensure that the subsequent winding structure of the battery cell is correct, which is conducive to streamlining the preparation process of the pole pieces 400, ensuring the quality of the pole pieces 400, and improving the flatness and safety performance of the battery cell after winding.

[0108] Further, referring to Figure 6, the first slot 220 is symmetrical about the boundary line between the first coating area 211 and the second coating area 212; referring to Figure 7, the second slot 320 is symmetrical about the boundary line between the third coating area 311 and the fourth coating area 312, which is conducive to making the shape and width, length and other dimensions of the tab slots 410 on the two adjacent pole pieces 400 formed after cutting more consistent, thereby improving the consistency of the prepared pole pieces 400.

[0109] Another way to increase energy density is to reduce the thickness of the battery cell due to auxiliary materials, reducing the cell volume and thus increasing the cell's energy density. In conventional cell structure design, the cell's tabs need to be covered with tab protective tape, resulting in a thicker tab area, which is not conducive to improving the cell's energy density.

[0110] To address this issue, some related technologies can reduce the thickness of the battery cell's tabs by reducing the thickness of the adhesive tape. However, this reduction in tape thickness reduces its strength, increasing the likelihood that burrs at the tab welds will break through the tape and pierce the separator, reducing the safety of the battery cell.

[0111] In other related technologies, scraping or laser cleaning can also be used to remove the active material corresponding to the protective tape to form a groove. After the electrode sheets are wound to form a battery cell, the protective tape at the location of the tab of one electrode sheet can be embedded in the groove of the other electrode sheet, thereby reducing the thickness of the battery cell at the tab. However, this method may also cause the residual material area between the groove and the edge of the electrode sheet, or the groove may partially remain at the end of the adjacent electrode sheet.

[0112] Based on this, a method similar to the tab groove can be used to make the air avoidance groove. There are many ways to set up the air avoidance groove. The following uses several embodiments to specifically illustrate several feasible ways to set up the air avoidance groove.

[0113] Example 1

[0114] 6 to 9 , the electrode preparation method further includes the following steps:

[0115] 6 , in the first coating zone group 210 , a portion of the coating is removed to form a third slot 230 , so that the boundary between the first coating zone 211 and the second coating zone 212 passes through the third slot 230 , and the third slot 230 and the first slot 220 are spaced apart in the length direction of the current collector 100 ;

[0116] 7 , in the second coating area group 310 , a portion of the coating is removed to form a fourth slot 330 , so that the boundary between the third coating area 311 and the fourth coating area 312 passes through the fourth slot 330 . The fourth slot 330 and the second slot 320 are spaced apart in the longitudinal direction of the current collector 100 . In a projection perpendicular to the current collector 100 , the fourth slot 330 overlaps with the third slot 230 .

[0117] 8 and 9 , after cutting along the boundary line between the adjacent first coating area 211 and the second coating area 212 to form a plurality of pole pieces 400, referring to Figures 10 to 12 , each third slot 230 is cut into two air-avoiding grooves 420 provided on two adjacent pole pieces 400, and each fourth slot 330 is cut into two air-avoiding grooves 420 provided on two pole pieces 400, and the structures of the six pole pieces 400 A1, B1, C1, D1, E1, and F1 formed after cutting are exactly the same, which is beneficial to improving the consistency of the structure of the pole piece 400.

[0118] 13 , after the electrode 400 is wound to form a battery cell, two air-avoidance grooves 420 are located on one side of the location of the pole ear 900 ″ of the other electrode sheet, which can avoid the pole ear 900 ″ of the other electrode sheet and the protective tape 910 ″ on the opposite sides of the location of the pole ear 900 ″. When the electrode 400 is wound to form a battery cell, the electrode 400 is pressed against the other electrode sheet, and the current collector 100 between the two air-avoidance grooves 420 can be deformed under the squeezing of the pole ear 900 ″ of the other electrode sheet and the protective tape 910 ″, so that the air-avoidance groove 420 away from the other electrode sheet can also play a role in avoiding the pole ear 900 ″ and the protective tape 910 ″ of the other electrode sheet, thereby reducing the thickness of the pole ear of the battery cell and improving the energy density of the battery cell.

[0119] The surface of the current collector 100 is coated with alternating long film surfaces (i.e., the first coating area 211 and the third coating area 311) and short film surfaces (i.e., the second coating area 212 and the fourth coating area 312), and slots (i.e., the first slot 220, the second slot 320, the third slot 230 and the fourth slot 330) are made on the dividing line between the adjacent long film surfaces and the short film surfaces. During subsequent cutting, the cutting line passes through the slots, which can avoid residual material areas between the slots and the edges of the electrode pieces 400 after cutting, and can avoid the appearance of slots at the tail of the electrode pieces 400 after cutting. It can also ensure that the winding structure of the subsequent battery cells is correct, which is conducive to streamlining the preparation process of the electrode pieces 400, ensuring the quality of the electrode pieces 400, and improving the flatness and safety performance of the battery cells after winding.

[0120] Example 2

[0121] 14 and 15 , it should be noted that in FIG14 and FIG15 , along the width direction of the current collector 100, A2, B2, C2, D2, E2, and F2 are used as the codes for the plurality of electrode sheets 400 after segmentation. The difference between this embodiment and Example 1 is that, in the projection perpendicular to the current collector 100, the fourth slot 330 is staggered with the third slot 230.

[0122] The positions of the tab grooves 410 and the avoidance grooves 420 of the B2, D2, and F2 pole pieces 400 after slitting on the pole piece 400 are shown in Figures 16 and 17. On the long film surface (i.e., the first coating area 211), the distance between the tab grooves 410 and the avoidance grooves 420 is relatively close, and on the short film surface (i.e., the fourth coating area 312), the distance between the tab grooves 410 and the avoidance grooves 420 is relatively far. Referring to Figure 18, after the pole piece 400 is wound to form a battery cell, the two avoidance grooves 420 are respectively located on both sides of the tab 900" of the other pole piece, and both face the other pole piece. The two avoidance grooves 420 can avoid the tab 900" of the other pole piece and the protective tape 910" on the opposite sides of the tab 900" on both sides of the other pole piece, and the location of the avoidance grooves 420 does not need to be deformed to reduce the thickness of the tab of the battery cell, thereby improving the energy density of the battery cell. The positions of the tab grooves 410 and the air-avoiding grooves 420 of the A2, C2, and E2 pole pieces 400 after cutting are shown in Figures 19 and 20. On the long film surface (i.e., the third coating area 311), the distance between the tab grooves 410 and the air-avoiding grooves 420 is relatively far, and on the short film surface (i.e., the second coating area 212), the distance between the tab grooves 410 and the air-avoiding grooves 420 is relatively close. 21 , after the electrode 400 is wound to form a battery cell, the two air-avoidance grooves 420 are respectively located on both sides of the position of the pole ear 900" of the other electrode, and both face away from the other electrode. The two air-avoidance grooves 420 can respectively avoid the pole ear 900" of the other electrode and the protective tape 910" on the opposite sides of the position of the pole ear 900" on both sides of the other electrode. When the electrode 400 is wound to form a battery cell, the electrode 400 is pressed against the other electrode, and the position of the air-avoidance groove 420 can be deformed under the pressure of the pole ear 900" of the other electrode and the protective tape 910". Therefore, although the air-avoidance groove 420 is located on the side of the electrode 400 facing away from the other electrode, it can also play a role in avoiding the pole ear 900" and the protective tape 910" of the other electrode, thereby reducing the thickness of the pole ear of the battery cell and improving the energy density of the battery cell.

[0123] Example 3

[0124] The difference between this embodiment and embodiment 1 is that, as shown in Figure 6, only part of the coating is removed in the first coating area group 210 to form a third groove 230, so that the boundary line between the first coating area 211 and the second coating area 212 passes through the third groove 230, and the third groove 230 and the first groove 220 are spaced apart in the length direction of the current collector 100.

[0125] Referring to Figure 8, after cutting along the dividing line between the adjacent first coating area 211 and the second coating area 212 to form multiple pole pieces 400, the air avoidance grooves 420 of the A1, C1, and E1 pole pieces 400 are located on the short film surface (i.e., the second coating area 212). Referring to Figure 22, after the pole pieces 400 are wound to form a battery cell, the air avoidance grooves 420 are located on one side of the position of the pole ear 900" of the other pole piece and face the other pole piece. The air avoidance grooves 420 can avoid the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the position of the pole ear 900" on one side of the other pole piece, thereby reducing the thickness of the pole ear of the battery cell and improving the energy density of the battery cell.

[0126] The air-avoidance groove 420 of the B1, D1, and F1 pole pieces 400 is located on the long film surface (i.e., the first coating area 211). Referring to FIG23, after the pole piece 400 is wound to form a battery cell, the air-avoidance groove 420 is located on one side of the location of the pole ear 900" of the other pole piece and away from the other pole piece. The air-avoidance groove 420 can avoid the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the location of the pole ear 900" on one side of the other pole piece. When After the electrode 400 is wound to form a battery cell, the electrode 400 is pressed against another electrode, and the position of the air-avoidance groove 420 can be deformed under the squeezing of the electrode ear 900" and the protective tape 910" of the other electrode. Therefore, although the air-avoidance groove 420 is located on the side of the electrode 400 away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, thereby reducing the thickness of the electrode ear of the battery cell and improving the energy density of the battery cell.

[0127] Example 4

[0128] The difference between this embodiment and embodiment 1 is that, as shown in Figure 7, only part of the coating is removed in the second coating area group 310 to form the fourth slot 330, so that the boundary line between the third coating area 311 and the fourth coating area 312 passes through the fourth slot 330, and the fourth slot 330 and the second slot 320 are spaced apart in the length direction of the current collector 100.

[0129] 9 , after cutting along the boundary line between the adjacent third coating area 311 and the fourth coating area 312 to form a plurality of pole pieces 400, the air avoidance grooves 420 of the B1, D1, and F1 pole pieces 400 are located on the short film surface (i.e., the fourth coating area 312). Referring to FIG22 , after the pole pieces 400 are wound to form a battery cell, the air avoidance grooves 420 are located on one side of the position of the pole ear 900" of the other pole piece and face the other pole piece. The air avoidance grooves 420 can avoid the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the position of the pole ear 900" on one side of the other pole piece, thereby reducing the thickness of the pole ear of the battery cell and improving the energy density of the battery cell.

[0130] The air-avoidance groove 420 of the A1, C1, and E1 pole pieces 400 is located on the long film surface (i.e., the third coating area 311). Referring to FIG23, after the pole piece 400 is wound to form a battery cell, the air-avoidance groove 420 is located on one side of the location of the pole ear 900" of the other pole piece and away from the other pole piece. The air-avoidance groove 420 can avoid the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the location of the pole ear 900" on one side of the other pole piece. When After the electrode 400 is wound to form a battery cell, the electrode 400 is pressed against another electrode, and the position of the air-avoidance groove 420 can be deformed under the squeezing of the electrode ear 900" and the protective tape 910" of the other electrode. Therefore, although the air-avoidance groove 420 is located on the side of the electrode 400 away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, thereby reducing the thickness of the electrode ear of the battery cell and improving the energy density of the battery cell.

[0131] Example 5

[0132] 24 , before cutting along the boundary line between the adjacent first coating area 211 and the second coating area 212, part of the coating is removed in the first coating area group 210 to form a third slot 230 and a fourth slot 330, so that the boundary line between the first coating area 211 and the second coating area 212 passes through the third slot 230 and the fourth slot 330, and the first slot 220, the third slot 230 and the fourth slot 330 are arranged in sequence in the length direction of the current collector 100.

[0133] After cutting along the boundary line between the adjacent first coating area 211 and the second coating area 212 to form a plurality of pole pieces 400, the positions of the tab grooves 410 and the air-avoidance grooves 420 of the B3, D3, and F3 pole pieces 400 after cutting on the pole piece 400 are shown in FIG25 , and the long film surface (i.e., the first coating area 211) has a tab groove 410 and two air-avoidance grooves 420. Referring to FIG26 , after the pole piece 400 is wound to form a battery cell, the two air-avoidance grooves 420 are respectively located on both sides of the position of the tab 900" of the other pole piece, one of the air-avoidance grooves 420 faces the other pole piece, and the other air-avoidance groove 420 faces away from the other pole piece. The two air-avoidance grooves 420 can avoid the tab 900" of the other pole piece and the protective tape 910" on the opposite sides of the tab 900" on both sides of the other pole piece. When the pole piece 400 is wound After the battery cell is formed, the electrode 400 is pressed against the other electrode, and the position of the avoidance groove 420 facing away from the other electrode can be deformed under the pressure of the electrode ear 900" and the protective tape 910" of the other electrode. Therefore, although the avoidance groove 420 is located on the side of the electrode 400 facing away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, which can reduce the thickness of the electrode ear of the battery cell and improve the energy density of the battery cell.

[0134] The positions of the tab grooves 410 and the avoidance grooves 420 of the A3, C3, and E3 pole pieces 400 after slitting on the pole piece 400 are shown in FIG27 . The short film surface (i.e., the second coating area 212) has a tab groove 410 and two avoidance grooves 420. Referring to FIG28 , after the pole piece 400 is wound to form a battery cell, the two avoidance grooves 420 are respectively located on both sides of the tab 900" of the other pole piece. One of the avoidance grooves 420 faces the other pole piece, and the other avoidance groove 420 faces away from the other pole piece. The two avoidance grooves 420 can avoid the tab 900" of the other pole piece and the protective tape 910" on the opposite sides of the tab 900" on both sides of the other pole piece. When the pole piece 400 is wound to form a battery cell, the two avoidance grooves 420 are respectively located on both sides of the other pole piece. After the battery cell is formed, the electrode 400 is pressed against the other electrode, and the position of the avoidance groove 420 facing away from the other electrode can be deformed under the pressure of the electrode ear 900" and the protective tape 910" of the other electrode. Therefore, although the avoidance groove 420 is located on the side of the electrode 400 facing away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, which can reduce the thickness of the electrode ear of the battery cell and improve the energy density of the battery cell.

[0135] Example 6

[0136] Before cutting along the boundary line between the adjacent first coating area 211 and the second coating area 212, in the second coating area group 310, part of the coating is removed to form the third slot 230 and the fourth slot 330, so that the boundary line between the third coating area 311 and the fourth coating area 312 passes through the third slot 230 and the fourth slot 330, and the second slot 320, the third slot 230 and the fourth slot 330 are arranged in sequence in the length direction of the current collector 100.

[0137] After cutting along the boundary line between the adjacent first coating area 211 and the second coating area 212 to form multiple pole pieces 400, similar to Example 5, two types of pole pieces 400 can also be formed, one of which has a pole lug groove 410 and two air avoidance grooves 420 on the long film surface (i.e., the third coating area 311), and the other pole piece 400 has a pole lug groove 410 and two air avoidance grooves 420 on the short film surface (i.e., the fourth coating area 312). The matching form of the air avoidance grooves 420 of these two pole pieces 400 and the other pole piece is also the same as in Example 5, and will not be repeated here.

[0138] Further, referring to Figure 6, the third slot 230 is symmetrical about the boundary line between the first coating area 211 and the second coating area 212, which is beneficial to making the shape and width, length and other dimensions of the first air avoidance groove 420 on the two adjacent pole pieces 400 formed after cutting more consistent, thereby improving the consistency of the prepared pole piece 400; referring to Figure 7, the fourth slot 330 is symmetrical about the boundary line between the third coating area 311 and the fourth coating area 312, which is beneficial to making the shape and width, length and other dimensions of the second air avoidance groove 430 on the two adjacent pole pieces 400 formed after cutting more consistent, thereby improving the consistency of the prepared pole piece 400.

[0139] In order to ensure that the tab 900 can be reliably accommodated inside the tab groove 410, the width, length and other dimensions of the tab groove 410 are usually larger than the width, length and other dimensions of the overlapping part of the tab 900 and the current collector 100, and the protective tape 910 needs to completely cover the exposed current collector 100 at the tab groove 410. Therefore, the part of the protective tape 910 covering the tab 900 is thicker than the part not covering the tab 900. Based on this, referring to Figures 29 and 30, the air avoidance groove 420 includes a first recess 421 and a second recess 422 that are sequentially connected along the thickness direction of the current collector 100. The second recess 422 is recessed from the bottom wall of the first recess 421 toward the current collector 100. One side edge of the second recess 422 and one side edge of the first recess 421 both coincide with one side edge of the current collector 100 in its width direction. The cross-sectional area of ​​the second recess 422 is smaller than that of the first recess 421. The second recess 422 is used to correspond to the tab 900" of the other pole piece, and the second recess 422 is used to avoid the position of the thicker tab 900". The air avoidance groove 420 including the first recess 421 and the second recess 422 can more specifically avoid areas of different thickness on the other pole piece, which is beneficial to further improve the flatness of the battery cell.

[0140] Due to equipment fluctuations, the position of the cutting line may also deviate, which may cause the long film surface of a pole piece 400 (i.e., the first coating area 211 or the third coating area 311) to remain on the empty foil area of ​​the short film surface of the adjacent pole piece 400 (i.e., the second coating area 212 or the fourth coating area 312). It may also cause the empty foil area of ​​the short film surface of a pole piece 400 (i.e., the second coating area 212 or the fourth coating area 312) to remain on the long film surface of the adjacent pole piece 400 (i.e., the first coating area 211 or the third coating area 311), thereby causing the performance of the battery cell formed after the pole piece 400 is wound to deteriorate and create safety risks.

[0141] Based on this, referring to FIG8 and FIG9, the electrode preparation method further includes the following steps:

[0142] 8 , along the length direction of the current collector 100 , a first insulating layer 500 is coated at the edge of the portion where the first coating region 211 exceeds the second coating region 212 . The first insulating layer 500 partially covers the first coating region 211 and the remaining portion covers the exposed current collector 100 .

[0143] 9 , along the length direction of the current collector 100 , a second insulating layer 600 is coated at the edge of the portion where the third coating region 311 exceeds the fourth coating region 312 . The second insulating layer 600 partially covers the third coating region 311 and the remaining portion covers the exposed current collector 100 .

[0144] 11 , the B1 and D1 pole pieces 400 after cutting have the second insulating layer 600 on both sides in the width direction of the empty foil area. Similarly, the C1 and E1 pole pieces 400 after cutting also have the first insulating layer 500 on both sides in the width direction of the empty foil area. The F1 pole piece 400 after cutting has the second insulating layer 600 only on one side in the width direction of the empty foil area, and the A1 pole piece 400 after cutting has the first insulating layer 500 only on one side in the width direction of the empty foil area.

[0145] The first insulating layer 500 and the second insulating layer 600 having a certain width can allow the deviation of the slitting line within a certain range. As long as the slitting line passes through the first insulating layer 500 and the second insulating layer 600, when the long film surface of one electrode 400 (i.e., the first coating area 211 or the third coating area 311) remains in the empty foil area of ​​the short film surface of the adjacent electrode 400 (i.e., the second coating area 212 or the fourth coating area 312), the first insulating layer 500 and the second insulating layer 600 cover the residual area. The active materials in the domain can eliminate the influence of this part of the active materials on the performance of the battery cell; when the empty foil area of ​​the short film surface (i.e., the second coating area 212 or the fourth coating area 312) of one electrode 400 remains to the long film surface (i.e., the first coating area 211 or the third coating area 311) of the adjacent electrode 400, the first insulating layer 500 and the second insulating layer 600 cover the exposed current collector 100 in the residual area, which can prevent the exposed current collector 100 from causing a short circuit of the battery cell and ensure the safety performance of the battery cell.

[0146] Specifically, the first insulating layer 500 and the second insulating layer 600 are made of ceramics, which have high mechanical strength, good wear resistance, and excellent insulation performance at high temperatures, which helps to ensure the quality of the electrode 400 and the safety performance of the battery cell.

[0147] When the position of the cutting line deviates, it may also cause the width of the electrode pieces 400 on both sides of the width direction of the current collector 100 to be greater or less than the designed width after cutting, thereby causing the electrode pieces 400 to be unable to be used normally and the yield rate to be low.

[0148] Based on this, referring to FIG8 to FIG9, the pole piece preparation method further includes the following steps:

[0149] 8 , an active material is coated on the first side 130 to form a first extended region 700 extending along the length direction of the current collector 100 on the first side 130 . A plurality of first coated regions 211 and a plurality of second coated regions 212 together constitute a first region 200 . The first region 200 is provided with first extended regions 700 on both sides in the width direction of the current collector 100 .

[0150] 9 , an active material is coated on the second side 140 to form a second extended region 800 extending along the length direction of the current collector 100. A plurality of third coated regions 311 and a plurality of fourth coated regions 312 together constitute a second region 300. The second extended regions 800 are provided on both sides of the second region 300 in the width direction of the current collector 100.

[0151] 8 and 9 , a first extension area 700 is adjacent to a first coating area 211 and has the same length as the first coating area 211, a second extension area 800 is adjacent to a fourth coating area 312 and has the same length as the fourth coating area 312, and is cut along the boundary line between the first extension area 700 and the first coating area 211; another first extension area 700 is adjacent to a second coating area 212 and has the same length as the second coating area 212, another second extension area 800 is adjacent to a third coating area 311 and has the same length as the third coating area 311, and is cut along the boundary line between the first extension area 700 and the second coating area 212.

[0152] Setting the first extension area 700 and the second extension area 800 can allow the cutting line to be offset within a certain range, ensuring that the pole pieces 400 located on both sides of the first area 200 in the width direction (i.e., both sides of the second area 300 in the width direction) still have the designed width when the cutting line position is offset to a certain extent, thereby improving the yield of the pole pieces 400.

[0153] It should be noted that the first coating area 211, the second coating area 212, and the first extension area 700 can be formed through multiple coating operations or through a single coating operation. Forming the first coating area 211, the second coating area 212, and the first extension area 700 simultaneously through a single coating operation is beneficial to improving the preparation efficiency of the pole piece 400; the third coating area 311, the fourth coating area 312, and the second extension area 800 can be formed through multiple coating operations or through a single coating operation. Forming the third coating area 311, the fourth coating area 312, and the second extension area 800 simultaneously through a single coating operation is beneficial to improving the preparation efficiency of the pole piece 400.

[0154] It should be noted that the cutting operation of the first extension area 700 and the first coating area 211 or the second coating area 212 adjacent to the first extension area 700 and the cutting operation of the adjacent first coating area 211 and the second coating area 212 can be performed successively or simultaneously. The simultaneous execution is conducive to improving the preparation efficiency of the electrode 400.

[0155] Specifically, the active material is one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and a ternary material including lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0156] 10 to 12, 16 and 17, 19 and 20, 25 and 27, an embodiment of the second aspect of the present application provides a pole piece 400, including a current collector 100, a first active layer (i.e., the first coating area 211 or the third coating area 311), a second active layer (i.e., the second coating area 212 or the fourth coating area 312) and an insulating layer (i.e., the first insulating layer 500 or the second insulating layer 600).

[0157] The first active layer covers one side of the current collector 100 in the thickness direction and has the same width as the current collector 100; the second active layer covers the other side of the current collector 100 in the thickness direction and has the same width as the current collector 100; the first active layer and the second active layer both have a tab groove 410, one side edge of the tab groove 410 coincides with one side edge of the current collector 100 in its width direction, the current collector 100 is exposed at the tab groove 410, and in the projection perpendicular to the direction of the current collector 100, the tab groove 410 of the second active layer coincides with the tab groove 410 of the first active layer, one of the tab grooves 410 is used to accommodate the tab 900, one end of the second active layer is aligned with one end of the first active layer, the length of the second active layer is less than the length of the first active layer, so that part of the current collector 100 is exposed on the side where the second active layer is located to form an empty foil area; the insulating layer covers at least one side of the empty foil area in the width direction of the current collector 100.

[0158] The pole piece 400 provided in the second aspect embodiment of the present application can be made by the pole piece preparation method provided in the first aspect embodiment of the present application. In the pole piece preparation method, alternating long film surfaces (i.e., the first coating area 211 and the third coating area 311) and short film surfaces (i.e., the second coating area 212 and the fourth coating area 312) are coated on the surface of the current collector 100, and grooves are made on the dividing line between the adjacent long film surfaces and the short film surfaces. During subsequent cutting, the cutting line passes through the grooves, which can avoid residual material areas between the grooves and the edges of the pole piece 400 after cutting, and can avoid the appearance of grooves at the tail of the pole piece 400 after cutting. It can also ensure that the winding structure of the subsequent battery cell is correct, which is conducive to streamlining the preparation process of the pole piece 400, ensuring the quality of the pole piece 400, and improving the flatness and safety of the battery cell after winding. Before cutting, an insulating layer with a certain width is coated on the edge of the portion where the long film surface exceeds the short film surface along the length direction of the current collector 100, and then cutting is performed. The insulating layer with a certain width can allow the cutting line to be offset within a certain range. As long as the cutting line passes through the insulating layer, the electrode 400 can be cut to form at least one side of the empty foil area in the width direction of the current collector 100 covered with an insulating layer. When the cutting position fluctuates, resulting in the active material of one electrode 400 remaining in the empty foil area of ​​the adjacent electrode 400, the insulating layer can cover the remaining active material; when the cutting position fluctuates, resulting in the empty foil area of ​​one electrode 400 remaining in the active material area of ​​the adjacent electrode 400, the insulating layer can cover the remaining empty foil area, thereby ensuring the performance of the electrode 400.

[0159] There are many ways to set the insulating layer, and it can be set specifically according to the position of the electrode 400 that may be defective due to the offset of the cutting line before slitting. For example, in some embodiments, the electrode 400 can be set to include one insulating layer, and the one insulating layer covers the entire empty foil area; in other embodiments, referring to Figures 11, 17, 19 and 27, the electrode 400 can be set to include two insulating layers, and the two insulating layers are respectively provided on both sides of the empty foil area in the width direction; in some other embodiments, the electrode 400 can also be provided to include one insulating layer, and the one insulating layer is provided on the side of the empty foil area adjacent to the long film surface of the other electrode 400 in the width direction.

[0160] Furthermore, when the electrode piece 400 is provided with two insulating layers disposed on both sides of the hollow foil region in the width direction, or when the electrode piece 400 is provided with one insulating layer disposed on one side of the hollow foil region in the width direction, the width of the insulating layer can be set according to the manufacturing capacity of the equipment to ensure that the sum of the widths of the two insulating layers of two adjacent electrode pieces 400 before slitting is sufficient to cover the offset range of the slitting line. Exemplarily, the width of the insulating layer is less than or equal to 1 mm, and preferably, the width of the insulating layer is 0.1 mm.

[0161] Furthermore, the thickness of the first active layer and the second active layer is the same, and the thickness of the insulating layer is less than or equal to the thickness of the first active layer, which can avoid the influence of excessive thickness of the insulating layer on the flatness of the battery cell and is conducive to improving the flatness of the battery cell.

[0162] Another way to improve energy density is to reduce the thickness of the battery cell added by the auxiliary materials, reduce the volume of the battery cell, and thus increase the energy density of the battery cell. In conventional battery cell structure design, since the location of the battery cell's pole tabs needs to be covered with pole tab protective tape, etc., the thickness of the battery cell's pole tabs is relatively thick, which is not conducive to improving the battery cell's energy density. Based on this, an air-avoidance groove 420 can be provided on the electrode 400, so that after the electrode 400 is wound to form a battery cell, the protective tape 910" at the location of the pole tab 900" of one electrode sheet can be embedded in the air-avoidance groove 420 on the other electrode sheet 400, thereby reducing the thickness of the battery cell's pole tabs.

[0163] There are many ways to set up the air-avoiding groove 420, for example:

[0164] In some embodiments, referring to FIG. 10 to FIG. 12 , both the first active layer and the second active layer of the electrode 400 have air-avoiding grooves 420 , and in a projection perpendicular to the current collector 100 , the two air-avoiding grooves 420 overlap. 13 , after the electrode 400 is wound to form a battery cell, two air-avoidance grooves 420 are located on one side of the location of the pole ear 900 ″ of the other electrode sheet, which can avoid the pole ear 900 ″ of the other electrode sheet and the protective tape 910 ″ on the opposite sides of the location of the pole ear 900 ″. When the electrode 400 is wound to form a battery cell, the electrode 400 is pressed against the other electrode sheet, and the current collector 100 between the two air-avoidance grooves 420 can be deformed under the squeezing of the pole ear 900 ″ of the other electrode sheet and the protective tape 910 ″, so that the air-avoidance groove 420 away from the other electrode sheet can also play a role in avoiding the pole ear 900 ″ and the protective tape 910 ″ of the other electrode sheet, thereby reducing the thickness of the pole ear of the battery cell and improving the energy density of the battery cell.

[0165] In other embodiments, referring to Figures 19 and 20, the first active layer and the second active layer of the electrode 400 both have an air avoidance groove 420, and the two air avoidance grooves 420 are staggered on the projection perpendicular to the current collector 100. Referring to Figure 18, after the electrode 400 is wound to form a battery cell, the two air avoidance grooves 420 are respectively located on both sides of the position of the pole ear 900" of the other electrode, and both face the other electrode. The two air avoidance grooves 420 can avoid the pole ear 900" of the other electrode and the protective tape 910" on the opposite sides of the position of the pole ear 900" on both sides of the other electrode, and the position of the air avoidance groove 420 does not need to be deformed to reduce the thickness of the pole ear of the battery cell, thereby improving the energy density of the battery cell; or, referring to Figure 21, after the electrode 400 is wound to form a battery cell, the two air avoidance grooves 420 are respectively located on both sides of the position of the pole ear 900" of the other electrode, and both face away from For the other pole piece, the two avoidance grooves 420 can respectively avoid the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the pole ear 900" on both sides of the other pole piece. When the pole piece 400 is wound to form a battery cell, the pole piece 400 is pressed tightly against the other pole piece, and the position of the avoidance groove 420 can be deformed under the squeezing of the pole ear 900" of the other pole piece and the protective tape 910". Therefore, although the avoidance groove 420 is located on the side of the pole piece 400 away from the other pole piece, it can also play a role in avoiding the pole ear 900" and the protective tape 910" of the other pole piece, which can reduce the thickness of the pole ear of the battery cell and improve the energy density of the battery cell.

[0166] In some other embodiments, only the first active layer of the electrode 400 has an air avoidance groove 420 or only the second active layer has an air avoidance groove 420. Referring to Figure 22, after the electrode 400 is wound to form a battery cell, the air avoidance groove 420 is located on one side of the location of the pole ear 900" of the other electrode and faces the other electrode. The air avoidance groove 420 can avoid the pole ear 900" of the other electrode and the protective tape 910" on the opposite sides of the location of the pole ear 900" on one side of the other electrode, which can reduce the thickness of the pole ear of the battery cell and improve the energy density of the battery cell; or, referring to Figure 23, after the electrode 400 is wound to form a battery cell, the air avoidance groove 420 is located on one side of the location of the pole ear 900" of the other electrode and faces away from the other electrode. The air avoidance groove 420 can One side of the other pole piece avoids the pole ear 900" of the other pole piece and the protective tape 910" on the opposite sides of the position of the pole ear 900". When the pole piece 400 is wound to form a battery cell, the pole piece 400 is pressed against the other pole piece, and the position of the avoidance groove 420 can be deformed under the squeezing of the pole ear 900" of the other pole piece and the protective tape 910". Therefore, although the avoidance groove 420 is located on the side of the pole piece 400 away from the other pole piece, it can also play a role in avoiding the pole ear 900" and the protective tape 910" of the other pole piece, which can reduce the thickness of the pole ear of the battery cell and improve the energy density of the battery cell.

[0167] In some further embodiments, only the first active layer of the electrode 400 has two air-avoidance grooves 420 or only the second active layer has two air-avoidance grooves 420. Referring to FIG26 , after the electrode 400 is wound to form a battery cell, the two air-avoidance grooves 420 are respectively located on both sides of the position of the pole ear 900" of the other electrode, one of the air-avoidance grooves 420 faces the other electrode, and the other air-avoidance groove 420 faces away from the other electrode. The two air-avoidance grooves 420 can avoid the pole ear 900" of the other electrode and the protective tape 910" on the opposite sides of the position of the pole ear 900" on both sides of the other electrode. When the electrode 400 is wound After the battery cell is formed, the electrode 400 is pressed against the other electrode, and the position of the avoidance groove 420 facing away from the other electrode is squeezed by the electrode ear 900" and the protective tape 910" of the other electrode, and can be deformed. Therefore, although the avoidance groove 420 is located on the side of the electrode 400 facing away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, thereby reducing the thickness of the electrode ear of the battery cell and improving the energy density of the battery cell; or 28, after the electrode 400 is wound to form a battery cell, the two avoidance grooves 420 are respectively located on both sides of the location of the pole ear 900" of the other electrode, one of the avoidance grooves 420 faces the other electrode, and the other avoidance groove 420 faces away from the other electrode. The two avoidance grooves 420 can avoid the pole ear 900" of the other electrode and the protective tape 910" on the opposite sides of the location of the pole ear 900" on both sides of the other electrode. When the electrode 400 is wound to form a battery cell, the two avoidance grooves 420 are respectively located on both sides of the other electrode. After winding to form a battery cell, the electrode 400 is pressed against the other electrode, and the position of the avoidance groove 420 facing away from the other electrode can be deformed under the pressure of the electrode ear 900" and the protective tape 910" of the other electrode. Therefore, although the avoidance groove 420 is located on the side of the electrode 400 facing away from the other electrode, it can also play a role in avoiding the electrode ear 900" and the protective tape 910" of the other electrode, thereby reducing the thickness of the electrode ear of the battery cell and improving the energy density of the battery cell.

[0168] In order to ensure that the tab 900 can be reliably accommodated inside the tab groove 410, the width, length and other dimensions of the tab groove 410 are usually larger than the width, length and other dimensions of the overlapping part of the tab 900 and the current collector 100, and the protective tape 910 needs to completely cover the exposed current collector 100 at the tab groove 410. Therefore, the part of the protective tape 910 covering the tab 900 is thicker than the part not covering the tab 900. Based on this, referring to Figures 29 and 30, the air avoidance groove 420 includes a first recess 421 and a second recess 422 that are sequentially connected along the thickness direction of the current collector 100. The second recess 422 is recessed from the bottom wall of the first recess 421 toward the current collector 100. One side edge of the second recess 422 and one side edge of the first recess 421 both coincide with one side edge of the current collector 100 in its width direction. The cross-sectional area of ​​the second recess 422 is smaller than that of the first recess 421. The second recess 422 is used to correspond to the tab 900" of the other pole piece, and the second recess 422 is used to avoid the position of the thicker tab 900". The air avoidance groove 420 including the first recess 421 and the second recess 422 can more specifically avoid areas of different thickness on the other pole piece, which is beneficial to further improve the flatness of the battery cell. A battery cell provided in an embodiment of the third aspect of the present application includes a tab 900 and a pole piece 400 provided in any embodiment of the second aspect of the present application. The tab 900 is connected to the tab groove 410 of the pole piece 400, and the pole piece 400 is wound to form a battery cell.

[0169] The battery cell provided by the third aspect embodiment of the present application includes the electrode 400 provided by the second aspect embodiment of the present application, and the electrode 400 is made by the electrode preparation method provided by the first aspect embodiment of the present application. In the electrode preparation method, the surface of the current collector 100 is coated with alternating long film surfaces (i.e., the first coating area 211 and the third coating area 311) and short film surfaces (i.e., the second coating area 212 and the fourth coating area 312), and grooves are made on the dividing line between adjacent long film surfaces and short film surfaces. During subsequent cutting, the cutting line passes through the grooves, which can avoid residual material areas between the grooves and the edges of the electrode 400 after cutting, and can avoid the appearance of grooves at the tail of the electrode 400 after cutting. It can also ensure that the winding structure of the subsequent battery cell is correct, which is conducive to streamlining the preparation process of the electrode 400, ensuring the quality of the electrode 400, and improving the flatness and safety performance of the battery cell after winding.

[0170] It is understood that a battery cell typically includes two electrode sheets with opposite polarities, and both electrode sheets may be prepared using the electrode sheet 400 provided in the second embodiment of the present application and prepared using the electrode sheet preparation method provided in the first embodiment of the present application, or only one of the electrode sheets may be prepared using the electrode sheet 400 provided in the second embodiment of the present application and prepared using the electrode sheet preparation method provided in the first embodiment of the present application. Those skilled in the art may select the preparation method for the two electrode sheets in the battery cell according to actual needs.

[0171] The embodiments of the present application have been described in detail above with reference to the accompanying drawings. However, the present application is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the purpose of the present application. In addition, the embodiments of the present application and the features of the embodiments can be combined with each other unless there is a conflict.

Claims

1. A method for preparing a pole piece, characterized in that, it includes the steps of: taking or preparing a current collector, the current collector having an alignment position, and the current collector having opposite first and second sides in its thickness direction; coating an active material on the first side, so that a plurality of first coating areas and a plurality of second coating areas extending along the length direction of the current collector are formed on the first side, the plurality of first coating areas and the plurality of second coating areas are alternately arranged along the width direction of the current collector, one end of the plurality of first coating areas is aligned with one end of the plurality of second coating areas at the alignment position, and the length of the first coating area is greater than the length of the second coating area; dividing the plurality of first coating areas and the plurality of second coating areas into a plurality of first coating area groups arranged along the width direction of the current collector, the first coating area group including one of the first coating areas and an adjacent second coating area, in the first coating area group, removing a part of the coating to form a first slot, so that the boundary line between the first coating area and the second coating area passes through the first slot; coating an active material on the second side, so that a plurality of third coating areas and a plurality of fourth coating areas extending along the length direction of the current collector are formed on the second side, the plurality of third coating areas and the plurality of fourth coating areas are alternately arranged along the width direction of the current collector, one end of the plurality of third coating areas is aligned with one end of the plurality of fourth coating areas at the alignment position, the length of the third coating area is the same as the length of the first coating area, the length of the fourth coating area is the same as the length of the second coating area, the width of the third coating area is the same as the width of the first coating area, the width of the fourth coating area is the same as the width of the second coating area, the opposite side of each third coating area is the second coating area, and the opposite side of each fourth coating area is the first coating area; dividing the plurality of third coating areas and the plurality of fourth coating areas into a plurality of second coating area groups arranged along the width direction of the current collector, the second coating area group including one of the third coating areas and an adjacent fourth coating area, in the second coating area group, removing a part of the coating to form a second slot, so that the boundary line between the third coating area and the fourth coating area passes through the second slot, and in the projection perpendicular to the current collector, the second slot coincides with the first slot; performing slitting along the boundary line between the adjacent first coating area and the second coating area to form a plurality of pole pieces, and each first slot and each second slot are slit into two pole ear slots respectively provided on two adjacent pole pieces, and the pole ear slots are used for connecting pole ears.

2. The method for preparing a pole piece according to claim 1, characterized in that, the first slot is symmetric about the boundary line between the first coating area and the second coating area, and the second slot is symmetric about the boundary line between the third coating area and the fourth coating area.

3. The method for preparing a pole piece according to claim 1 or 2, characterized in that, the method for preparing a pole piece further includes the step of: Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the first coating area group, a portion of the coating is removed to form a third slot, so that the boundary line between the first coating area and the second coating area passes through the third slot, and the third slot and the first slot are arranged at intervals in the length direction of the current collector; after the cutting is performed along the boundary line between the adjacent first coating area and the second coating area to form a plurality of pole pieces, each of the third slots is divided into two avoidance slots provided on two adjacent pole pieces, and the avoidance slots are used to avoid the pole ears of another pole piece; and / or, Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the second coating area group, part of the coating is removed to form a fourth slot, so that the boundary line between the third coating area and the fourth coating area passes through the fourth slot, and the fourth slot and the second slot are spaced apart in the length direction of the collector; after the cutting is performed along the boundary line between the adjacent first coating area and the second coating area to form a plurality of pole pieces, each of the fourth slots is divided into two avoidance slots arranged on two adjacent pole pieces.

4. The method for preparing a pole piece according to claim 3, It is characterized in that The third slot is symmetrical about the boundary line between the first coating area and the second coating area; the fourth slot is symmetrical about the boundary line between the third coating area and the fourth coating area.

5. The method for preparing a pole piece according to claim 3, It is characterized in that Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the first coating area group, part of the coating is removed to form the third slot, and in the second coating area group, part of the coating is removed to form the fourth slot; in the projection perpendicular to the current collector, the fourth slot coincides with the third slot, or the fourth slot is staggered with the third slot.

6. The method for preparing a pole piece according to claim 1 or 2, It is characterized in that The pole piece preparation method further comprises the steps of: Before the cutting along the boundary line between the adjacent first coating area and the second coating area, in the first coating area group, a portion of the coating is removed to form a third slot and a fourth slot, so that the boundary line between the first coating area and the second coating area passes through the third slot and the fourth slot, and the first slot, the third slot and the fourth slot are sequentially spaced in the length direction of the current collector; or, Before the cutting is performed along the boundary line between the adjacent first coating area and the second coating area, in the second coating area group, part of the coating is removed to form a third slot and a fourth slot, so that the boundary line between the third coating area and the fourth coating area passes through the third slot and the fourth slot, and the second slot, the third slot and the fourth slot are sequentially spaced in the length direction of the collector.

7. The method for preparing a pole piece according to claim 1, It is characterized in that The pole piece preparation method further comprises the steps of: Along the length direction of the current collector, a first insulating layer is coated at the edge of the part where the first coating area extends beyond the second coating area. The first insulating layer partially covers the first coating area and the remaining part covers the exposed current collector; Along the length direction of the current collector, a second insulating layer is coated at the edge of the part where the third coating area extends beyond the fourth coating area. The second insulating layer partially covers the third coating area and the remaining part covers the exposed current collector.

8. The method for preparing a pole piece according to claim 7, characterized in that, the materials of the first insulating layer and the second insulating layer are ceramics.

9. The method for preparing a pole piece according to claim 1, characterized in that, the method for preparing the pole piece further comprises the steps of: coating an active material on the first side to form a first extension area extending along the length direction of the current collector on the first side. A plurality of the first coating areas and a plurality of the second coating areas together form a first region, and the first extension areas are provided on both sides of the first region in the width direction of the current collector; coating an active material on the second side to form a second extension area extending along the length direction of the current collector on the second side. A plurality of the third coating areas and a plurality of the fourth coating areas together form a second region, and the second extension areas are provided on both sides of the second region in the width direction of the current collector; one first extension area is adjacent to one first coating area and has the same length as the first coating area, and one second extension area is adjacent to one fourth coating area and has the same length as the fourth coating area. Cutting is performed along the boundary line between the first extension area and the first coating area; one first extension area is adjacent to one second coating area and has the same length as the second coating area, and one second extension area is adjacent to one third coating area and has the same length as the third coating area. Cutting is performed along the boundary line between the first extension area and the second coating area.

10. The method for preparing a pole piece according to claim 1, characterized in that, the active material is one of lithium cobaltate, lithium manganate, lithium iron phosphate, and ternary materials.

11. A pole piece, characterized in that, comprising: a current collector; a first active layer covering one side of the current collector in the thickness direction and having the same width as the current collector; A second active layer, covering the other side of the current collector in the thickness direction and having the same width as the current collector; both the first active layer and the second active layer have tab slots, one side edge of the tab slot coincides with one side edge of the current collector in its width direction, the current collector is exposed at the tab slot, and in the projection perpendicular to the direction of the current collector, the tab slot of the second active layer coincides with the tab slot of the first active layer. One of the tab slots is used to accommodate a tab. One end of the second active layer is aligned with one end of the first active layer, and the length of the second active layer is less than the length of the first active layer, so that part of the current collector is exposed on the side where the second active layer is located to form an empty foil area; An insulating layer, covering at least one side of the empty foil area in the width direction of the current collector.

12. The electrode tab according to claim 11, wherein, the first active layer and / or the second active layer has a clearance slot, one side edge of the clearance slot coincides with one side edge of the current collector in its width direction, the clearance slot and the tab slot are located on the same side of the current collector in the width direction, the clearance slot and the tab slot are arranged at intervals along the length direction of the current collector, and the clearance slot is used to avoid the tab of another electrode tab after winding.

13. The electrode tab according to claim 11, wherein, the first active layer or the second active layer has two clearance slots arranged at intervals, one side edge of the clearance slot coincides with one side edge of the current collector in its width direction, the clearance slot and the tab slot are located on the same side of the current collector in the width direction, the clearance slot and the tab slot are arranged at intervals along the length direction of the current collector, and the clearance slot is used to avoid the tab of another electrode tab after winding.

14. The electrode tab according to claim 12 or 13, wherein, the clearance slot includes a first recess and a second recess that are sequentially connected along the thickness direction of the current collector. The second recess is recessed from the bottom wall of the first recess towards the current collector. One side edge of the second recess and one side edge of the first recess both coincide with one side edge of the current collector in its width direction. The cross-sectional area of the second recess is smaller than the cross-sectional area of the first recess, and the second recess is used to correspond to the tab.

15. The electrode tab according to claim 11, wherein, the width of the insulating layer is less than or equal to 1 mm.

16. The electrode tab according to claim 15, wherein, the width of the insulating layer is 0.1 mm.

17. The electrode tab according to claim 11, wherein, the thickness of the insulating layer is less than or equal to the thickness of the first active layer.

18. A battery cell, wherein, comprising: a tab; the electrode tab according to any one of claims 11 to 17, the tab is connected to the tab slot of the electrode tab, and the electrode tab is wound to form the battery cell.

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