Electrode sheet structure, electrode sheet manufacturing method, and electrochemical device

Abstract

The present application provides an electrode sheet structure, an electrode sheet manufacturing method, and an electrochemical device. The electrode sheet structure comprises a first electrode sheet, and the first electrode sheet comprises a first current collector and a first active material layer arranged on the surface of the first current collector. In the width direction of the first electrode sheet, the first electrode sheet has a first side edge and a second side edge which are opposite to each other, the first side edge is provided with a first groove, the second side edge is provided with a second groove, and the projection of the second groove on the first side edge at least partially overlaps with the first groove. A first exposed foil area is provided in the first groove, and the second groove runs through the first electrode sheet in the thickness direction of the first electrode sheet. In the length direction of the first electrode sheet, the size of the second groove is larger than that of the first groove. No active material is present between the first groove and the edge of the first electrode sheet, so that secondary active material removal is not required, and burrs in the first groove are reduced; the size of the second groove is configured to be larger than that of the first groove, so that it can be ensured that no exposed foil area is left, and the safety risk caused by burrs is reduced.

Description

Electrode structure, electrode manufacturing method and electrochemical device Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a pole piece structure, a pole piece manufacturing method, and an electrochemical device. Background Art

[0002] In the prior art, the electrode is usually provided with a slot for welding the electrode tab. During the electrode preparation process, a slitting process is used to cut the electrode mother sheet to produce multiple electrode sheets. Due to slitting fluctuations or the accuracy of the slitting equipment, the slitting process cannot be carried out completely along the edge of the empty foil area slot on the electrode mother sheet, resulting in the presence of some active material at the edge of the electrode slot and the electrode after slitting. Therefore, this part of the active material needs to be removed before welding the electrode tab. The process of removing this part of the active material will cause more burrs to form on the metal foil in the electrode tab slot, which may cause safety risks. Summary of the Invention

[0003] The present application provides a pole piece structure, a pole piece manufacturing method and an electrochemical device to solve the above-mentioned technical problems.

[0004] The embodiment of the present application is implemented as follows:

[0005] A pole piece structure includes a first pole piece, the first pole piece includes a first current collector and a first active material layer arranged on the surface of the first current collector. Along the width direction of the first pole piece, the first pole piece has a first side and a second side that are opposite to each other, the first side is provided with a first groove, and the second side is provided with a second groove. Along the width direction of the first pole piece, the projection of the second groove on the first side at least partially overlaps with the first groove. The first groove has a first hollow foil area in the first groove, and the second groove passes through the first pole piece along the thickness direction of the first pole piece. Along the length direction of the first pole piece, the size of the second groove is larger than the size of the first groove. The first groove is a groove formed by removing part of the first active material layer, with the first hollow foil area as the bottom and the first active material layer as the periphery.

[0006] In this way, the first groove and the second groove can be formed on the two side walls of the first pole piece respectively by cutting the empty foil area slot on the pole piece mother sheet. There is no active material between the first groove and the edge of the first pole piece, and there is no need to remove the active material for the second time, thereby reducing the burrs in the first groove. The second groove can pass through the first pole piece by secondary die-cutting. The size of the second groove is set to be larger than that of the first groove, which can ensure that no empty foil area will remain in the second groove, reduce the safety risks caused by burrs, and fully improve the safety of use of the first pole piece.

[0007] In some possible implementations, along the length of the first electrode sheet, the second groove has a dimension a, and the first groove has a dimension b, where 0 < ab ≤ 2 mm. This ensures that during the secondary die-cutting process, the second groove is formed without leaving any empty foil area, while also minimizing active material loss through dimensional constraints, keeping energy density loss within an acceptable range.

[0008] In some possible implementations: along the length direction of the first pole piece, the dimensions of the second groove and the first groove satisfy 0.1 mm ≤ ab ≤ 0.8 mm.

[0009] In some possible embodiments, the electrode structure further includes a second electrode having a polarity opposite to that of the first electrode; the second electrode includes a second current collector and a second active material layer, the second active material layer being disposed on the surface of the second current collector. Along the width of the second electrode, the second electrode has opposing third and fourth sides, with a third groove provided on the third side and a fourth groove provided on the fourth side. Along the width of the second electrode, the projection of the fourth groove on the third side at least partially overlaps with the third groove. A second hollow foil region is defined within the third groove, extending through the second electrode along its thickness. Along the length of the second electrode, the fourth groove is larger than the third groove. The second electrode has a polarity opposite to that of the first electrode. The third and fourth grooves can also be formed on either side of the second electrode by cutting the hollow foil region slots on the electrode mother sheet. The fourth groove can be formed by a secondary die-cutting process through the second electrode, eliminating the hollow foil region within the fourth groove, thereby improving the safety of the second electrode.

[0010] In some possible implementations, the first electrode piece is a cathode piece, the second electrode piece is an anode piece, and the area of ​​the third groove is larger than that of the first groove. Since the anode tab is typically made of nickel, which has lower current carrying capacity than aluminum tabs, the area of ​​the anode tab can be increased to increase the current carrying area.

[0011] In some possible implementations: the area of ​​the first groove is S1, the area of ​​the third groove is S2, 20mm 2 ≤S2-S1≤80mm 2 .

[0012] In the above solution, by controlling the area of ​​the third groove to be larger, the anode tab can be made larger.

[0013] Increase the diversion area and control S1-S2 to less than 80mm 2 , which can ensure that not too much energy density is lost and prevent lithium plating to a certain extent.

[0014] In some possible embodiments, along the length of the first electrode sheet, the fourth groove has a dimension c, and the second groove has a dimension a, where 0 < c a ≤ 2 mm. To ensure the flow area of ​​the anode tab, the width of the third groove is larger than that of the first groove, resulting in the corresponding fourth groove being larger than the second groove. However, if the width is too large, lithium deposition may occur in the area corresponding to the fourth groove.

[0015] In some possible implementations, along the length direction of the first electrode sheet, the dimensions of the fourth groove and the second groove satisfy 0.4 mm ≤ ca ≤ 1.6 mm, thereby further ensuring the current capacity of the anode tab and reducing lithium plating.

[0016] In some possible embodiments, the second groove has a bottom wall and two side walls, the side walls being spaced apart and connecting the bottom wall and the second side edge, a first arc segment being defined between the side wall and the bottom wall, and a second arc segment being defined between the side wall and the second side edge. This can reduce the risk of sharp corners of the second groove piercing the pole pieces during pole piece stacking or winding.

[0017] In some possible implementations, along the width direction of the first pole piece, the dimension of the first groove is f, and the dimension of the second groove is e, where f>e and 3≤f / e≤10. By constraining the dimensions of the first and second grooves, on the one hand, the impact of an oversized second groove on the overall strength of the pole piece is reduced, reducing the risk of tearing and deformation of the pole piece. It also mitigates the problems of low tab connection strength and current carrying capacity caused by an undersized first groove. On the other hand, the formation of the second groove is ensured.

[0018] In some possible implementations, a ratio of the size f of the first groove to the size e of the second groove is 3-6.

[0019] In some possible embodiments, the first electrode tab is further included, the first electrode tab is partially disposed in the first groove, and the first electrode tab is electrically connected to the first current collector, and the overlapping area between the first electrode tab and the first current collector is greater than or equal to 140 mm 2 So that the electrode tab has sufficient connection strength and flow capacity with the first electrode piece in the first groove.

[0020] In some possible embodiments, a first insulating member is further included. The first insulating member is disposed on the surface of the first active material layer and covers the first groove. The area of ​​the first insulating member is larger than the area of ​​the first groove. Thus, the first insulating member can protect the first hollow foil area and the first tab within the first groove, reducing internal short circuits caused by contact between the first hollow foil area and the first tab and a pole piece of opposite polarity, thereby improving pole piece safety.

[0021] In some possible embodiments, the device further comprises a diaphragm, a second pole piece, and a second insulating member. The first pole piece, the diaphragm, and the second pole piece are stacked, and the second insulating member is disposed on the surface of the second pole piece. The position of the second insulating member corresponds to the position of the second groove, and the area of ​​the second insulating member is less than or equal to the area of ​​the second groove. In this way, the second insulating member can be accommodated in the second groove, reducing thickness differences on the pole piece surface and improving the surface consistency of the pole piece.

[0022] In some possible embodiments, the first active material layer is disposed on opposite sides of the first current collector. The thickness of the second insulating member is less than or equal to the sum of the thicknesses of the first current collector and the two first active material layers. This can reduce the risk of the second insulating member protruding from the electrode surface and further improve the surface consistency of the electrode.

[0023] An embodiment of the present application further provides a pole piece manufacturing method for manufacturing the pole piece structure of the above embodiment, the pole piece manufacturing method comprising:

[0024] Providing a first pole piece mother sheet, the first pole piece mother sheet comprising a first current collector and a first active material layer disposed on a surface of the first current collector;

[0025] A portion of the first active material layer is removed to form a first empty foil area slot, and a plurality of first empty foil area slots are arranged at intervals along the width direction of the first pole piece mother sheet;

[0026] A cutting line is set along the length direction of the first pole piece mother sheet, and a plurality of cutting lines pass through the first empty foil area slot respectively;

[0027] Cutting the first pole piece mother sheet along the cutting line to form a plurality of first pole pieces, the cut first empty foil area is slotted on both sides of the first pole piece to form a first sub-empty foil area and a second sub-empty foil area, respectively, and the first sub-empty foil area forms a first groove;

[0028] The side of the first pole piece having the second sub-empty foil area is cut to remove the second sub-empty foil area, thereby forming a second groove on the side of the first pole piece.

[0029] In some possible embodiments, the pole piece manufacturing method includes: cutting the edge of the second groove, forming a first arc segment between the side wall and the bottom wall of the second groove, and forming a second arc segment between the side wall of the second groove and the side edge of the first pole piece.

[0030] An embodiment of the present application further provides an electrochemical device, comprising the electrode structure and a packaging shell of the above embodiment, wherein the electrode structure is disposed in the packaging shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0032] FIG1 is a schematic structural diagram of a pole piece structure according to an embodiment of the present application.

[0033] FIG2 is a schematic structural diagram of a pole piece structure in one embodiment.

[0034] FIG3 is a schematic structural diagram of a pole piece structure in one embodiment.

[0035] FIG4 is a schematic structural diagram of a pole piece structure in one embodiment.

[0036] FIG5 is a schematic diagram of the cross-sectional structure of a pole piece structure in one embodiment.

[0037] FIG6 is a schematic structural diagram of a pole piece manufacturing method in one embodiment.

[0038] FIG. 7 is a schematic structural diagram of an electrochemical device in one embodiment.

[0039] Description of the main component symbols: Pole piece structure 100 First pole piece 10 First current collector 11 First active material layer 12 First side 13 Second side 14 First groove 15 Second groove 16 Bottom wall 161 Side wall 162 First arc segment 163 Second arc segment 164 First empty foil area 17 Second pole piece 20 Second current collector 21 Second active material layer 22 Third side 23 Fourth side 24 Third groove 25 Fourth groove 26 Second empty foil area 27 First pole tab 30 First insulating member 40 Second insulating member 50 Diaphragm 60 First pole piece mother sheet 70 First empty foil area slot 71 First sub-empty foil area 72 Second sub-empty foil area 73 Cutting line 74 Cutting line 75 Electrochemical device 200 Packaging shell 201 Second pole tab 80 DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0041] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may also be an element centered therein. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may also be an element centered therein. When an element is considered to be "set on" another element, it may be directly set on the other element or there may also be an element centered therein. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "or / and" as used herein includes any and all combinations of one or more of the relevant listed items.

[0043] Some embodiments of the present application are described in detail. In the absence of conflict, the following embodiments and features of the embodiments can be combined with each other.

[0044] 1 and 6 , an embodiment of the present application further provides a pole piece manufacturing method for manufacturing a pole piece structure 100. The pole piece manufacturing method includes:

[0045] Providing a first pole piece mother sheet 70, the first pole piece mother sheet 70 includes a first current collector 701 and a first active material layer 702 disposed on the surface of the first current collector 701;

[0046] A portion of the first active material layer 702 is removed to form a first empty foil area slot 71 , and a plurality of first empty foil area slots 71 are arranged at intervals along the width direction of the first pole piece mother sheet 70 ;

[0047] A plurality of cutting lines 74 are provided along the length direction of the first pole piece mother sheet 70 , and the plurality of cutting lines 74 are provided at intervals and respectively pass through the first empty foil area slots 71 ;

[0048] The first pole piece mother sheet 70 is cut along the cutting line 74 to form a plurality of first pole pieces 10. The cut first empty foil area slot 71 forms a first sub-empty foil area 72 and a second sub-empty foil area 73 on both sides of the first pole piece 10, and the first sub-empty foil area 72 forms a first groove 15.

[0049] The side of the first pole piece 10 having the second sub-empty foil area 73 is cut and removed to form a second groove 16 on the side of the first pole piece 10 . The second groove 16 passes through the first pole piece 10 along the thickness direction of the first pole piece 10 .

[0050] In the embodiment of the present application, the first empty foil area slot 71 is a generally rectangular slot structure, and the dimension of the first empty foil area slot 71 along the width direction of the first pole piece mother sheet 70 is smaller than the dimension of the first pole piece 10, thereby reducing the impact of active material layer loss on energy density. The first current collector 701 is present in the slot, but the first active material layer 702 is absent, so that the first current collector 701 in the slot forms an empty foil area structure. No through-holes or other structures are provided on the first current collector 701 in the slot, thereby reducing the risk of burrs.

[0051] When the second sub-empty foil area 73 is cut and removed, the side of the first pole piece 10 having the second sub-empty foil area 73 is cut along the cut 75, and the area surrounded by the cut 75 covers the second sub-empty foil area 73. Affected by the processing accuracy, the cutting accuracy of the secondary die-cutting may have deviations. The range of the cut 75 is set to be larger than the range of the second sub-empty foil area 73, and the cut 75 is placed within the area of ​​the first active material layer 702, so that the first pole piece 10 can completely remove the second sub-empty foil area 73 during the secondary die-cutting process, and the formed second groove 16 does not have any empty foil area. The edge structure of the second groove 16 is a structure of the active material layer coated with the current collector, which greatly reduces the problem of burrs in the cutting process, allowing the first pole piece 10 to be used directly after the secondary die-cutting, and reducing the safety risks caused by burrs in the second groove 16 during the stacking or winding of the first pole piece 10.

[0052] As shown in FIG2 , the pole piece manufacturing method further includes: cutting the edge of the second groove 16, forming a first arc segment 163 between the side wall 162 and the bottom wall 161 of the second groove 16, and forming a second arc segment 164 between the side wall 162 of the second groove 16 and the side edge of the first pole piece 10. In this way, after the second groove 16 is formed, it is less likely to have sharp corners or burrs on the edges, further improving the safety of the pole piece.

[0053] Please refer to Figure 1 again. This embodiment provides a pole piece structure 100, including a first pole piece 10. The first pole piece 10 includes a first current collector 11 and a first active material layer 12 arranged on the surface of the first current collector 11. Along the width direction of the first pole piece 10, the first pole piece 10 has a first side 13 and a second side 14 relative to each other. The first side 13 is provided with a first groove 15, and the second side 14 is provided with a second groove 16. The projection of the second groove 16 on the first side 13 at least partially overlaps with the first groove 15. The first groove 15 has a first empty foil area 17, and the second groove 16 passes through the first pole piece 10 along the thickness direction of the first pole piece 10. Along the length direction of the first pole piece 10, the size of the second groove 16 is larger than the size of the first groove 15.

[0054] In the embodiment of the present application, the direction indicated by arrow A is the length direction of the first pole piece 10, that is, the direction in which the long side of the first pole piece 10 extends. The direction indicated by arrow B is the width direction of the first pole piece 10, that is, the direction in which the short side of the first pole piece 10 extends. The thickness direction of the first pole piece 10 is perpendicular to the length direction and width direction of the first pole piece 10. The width direction of the first pole piece mother sheet 70 is the same as the width direction of the first pole piece 10. The length direction of the first pole piece mother sheet 70 is the same as the length direction of the first pole piece 10.

[0055] In the embodiment of the present application, the first groove 15 and the second groove 16 can be formed on both sides of the first pole piece 10 by cutting the empty foil area slots on the pole piece mother sheet. In the first pole piece 10 formed after the pole piece mother sheet is cut, there is no active material between the first groove 15 and the edge of the first pole piece 10, and there is no need to remove the active material for the second time, thereby reducing the burrs in the first groove 15. The second groove 16 can pass through the first pole piece 10 by secondary die-cutting, and the size of the second groove 16 is set to be larger than the size of the first groove 15, which can ensure that no empty foil area will remain in the second groove 16, and also reduce the safety risks caused by burrs, thereby fully improving the safety of use of the first pole piece 10.

[0056] In some embodiments, as shown in FIG1 , along the length of the first pole piece 10 , the second groove 16 has a dimension a, and the first groove 15 has a dimension b, where 0 < ab ≤ 2 mm. This ensures that, during the secondary die-cutting process, the second groove 16 is formed without any empty foil area remaining within the second groove 16 , while also minimizing active material loss through dimensional constraints, thereby keeping energy density loss within an acceptable range.

[0057] In one embodiment, the dimensions of the second groove 16 and the first groove 15 satisfy 0.1 mm ≤ ab ≤ 0.8 mm, thereby optimizing the dimensional constraint between the first groove 15 and the second groove 16 and further reducing energy density loss. Alternatively, ab can be any value among 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, and 2.0 mm, or between any two values.

[0058] As shown in Figure 2, in some embodiments, the second groove 16 has a bottom wall 161 and two side walls 162. The side walls 162 are spaced apart and connect the bottom wall 161 to the second side edge 14. A first arc segment 163 is defined between the side walls 162 and the bottom wall 161, and a second arc segment 164 is defined between the side walls 162 and the second side edge 14. This reduces the risk of sharp corners of the second groove 16 piercing the pole pieces during pole piece stacking or winding.

[0059] Please refer to Figure 3. In some embodiments, the electrode structure 100 further includes a second electrode 20. The polarity of the second electrode 20 is opposite to that of the first electrode 10. The second electrode 20 includes a second current collector 21 and a second active material layer 22, and the second active material layer 22 is disposed on the surface of the second current collector 21. Along the width direction of the second electrode 20, the second electrode 20 has a third side 23 and a fourth side 24 opposite to each other. The third side 23 is provided with a third groove 25, and the fourth side 24 is provided with a fourth groove 26. The projection of the fourth groove 26 on the third side 23 at least partially overlaps with the third groove 25. The third groove 25 has a second empty foil area 27, and the fourth groove 26 passes through the second electrode 20 along the thickness direction of the second electrode 20. Along the length direction of the second electrode 20, the size of the fourth groove 26 is larger than that of the third groove 25.

[0060] The width, length, and thickness of the second pole piece 20 are respectively the same as those of the first pole piece 10. The manufacturing method of the second pole piece 20 is substantially the same as the aforementioned pole piece manufacturing method. The third groove 25 and the fourth groove 26 can also be formed on both sides of the second pole piece 20 by cutting the empty foil area slots on the pole piece mother sheet. The fourth groove 26 can be passed through the second pole piece 20 by secondary die cutting, so that there is no empty foil area in the fourth groove 26, thereby improving the safety of the second pole piece 20.

[0061] In some embodiments, the first electrode sheet 10 and the second electrode sheet 20 can be stacked or wound to form a component of a battery cell. The first electrode sheet 10 is the cathode sheet, the second electrode sheet 20 is the anode sheet, and the area of ​​the third groove 25 is larger than the area of ​​the first groove 15. Since the anode tab is typically made of nickel, which has lower current carrying capacity than aluminum tabs, this method can increase the area of ​​the anode tab, thereby increasing the current carrying area.

[0062] In some embodiments, the area of ​​the first groove 15 is S1, the area of ​​the third groove 25 is S2, and the area of ​​the first groove 15 is S1. 2 ≤S2-S1≤80mm 2 By making the area of ​​the third groove 25 larger, the anode tab can be made larger, increasing the flow conduction area, and S1-S2 can be controlled to be less than 80mm. 2, which can ensure that not too much energy density is lost and prevent lithium plating to a certain extent.

[0063] In some embodiments, along the length of the first electrode sheet 10, the fourth groove 26 has a dimension c, and the second groove 16 has a dimension a, where 0 < c a ≤ 2 mm. To ensure the flow area of ​​the anode tab, the width of the third groove 25 is greater than that of the first groove 15, resulting in a corresponding larger fourth groove 26 than the second groove 16. However, if the width is too large, lithium deposition may occur in the portion corresponding to the fourth groove 26.

[0064] In one embodiment, the dimensions of the fourth groove 26 and the second groove 16 satisfy 0.4 mm ≤ ca ≤ 1.6 mm, thereby optimizing the dimensional constraint between the fourth groove 26 and the second groove 16, further ensuring the current capacity of the anode tab while reducing lithium plating. Alternatively, ca can be any value among 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2.0 mm, or between any two numerical ranges.

[0065] In some embodiments, along the width direction of the first electrode sheet 10, the size of the first groove 15 is f, and the size of the second groove 16 is e, wherein the units of the dimensions of the first groove 15 and the second groove 16 are both mm, f>e, and 3≤f / e≤10. By constraining the height dimension between the first groove 15 and the second groove 16, the electrode sheet between the first groove 15 and the second groove 16 is prevented from being too narrow, the impact of excessive groove size on the overall strength of the electrode sheet is reduced, and the risk of tearing, pulling and deforming the electrode sheet is reduced. In addition, when cutting the electrode mother sheet, the first groove 15 can have a larger size under the condition that the area of ​​the empty foil area slot is constant, thereby reducing the problems of low lug connection strength and flow capacity caused by the first groove 15 being too small, and the formation of the second groove 16 can be ensured.

[0066] In one embodiment, the ratio f / e of the dimension f of the first groove 15 to the dimension e of the second groove 16 is 3 to 6 to further optimize the height relationship between the first groove 15 and the second groove 16. Alternatively, f / e can be any value among 3, 4, 5, 6, 7, 8, 9, 10, or a value between any two numerical ranges. The height relationship between the third groove 25 and the fourth groove 26 in the second pole piece 20 can also be substantially the same as the height relationship between the first groove 15 and the second groove 16, and will not be further described here.

[0067] Referring to FIG4 , in some embodiments, the electrode structure 100 further includes a first electrode tab 30 , which is partially disposed within the first groove 15 and electrically connected to the first current collector 11 . The first empty foil area 17 within the first groove 15 is part of the first current collector 11 , and the first electrode tab 30 can be fixed to the empty foil area within the first groove 15 by welding, conductive adhesive bonding, or the like, to achieve electrical connection between the first electrode tab 30 and the first current collector 11 . The overlapping area between the first electrode tab 30 and the first current collector 11 is greater than or equal to 140 mm 2 so that the first electrode tab 30 has sufficient connection strength and flow capacity with the first electrode piece 10 in the first groove 15 .

[0068] Optionally, a second pole tab may be provided in the third groove 25 of the second pole piece 20 . The connection scheme between the second pole tab and the second pole piece 20 is the same as the connection scheme between the first pole tab 30 and the first pole piece 10 , which will not be repeated here.

[0069] In some embodiments, referring to Figures 1 and 4 , the electrode structure 100 further includes a first insulating member 40, which is disposed on the surface of the first active material layer 12 and covers the first groove 15. The area of ​​the first insulating member 40 is larger than that of the first groove 15. Thus, both the first groove 15 and the first electrode tab 30 can be covered by the first insulating member 40, reducing the internal short circuit problem caused by the first hollow foil area 17 and the first electrode tab 30 contacting the electrode of opposite polarity, thereby further improving the safety of the electrode.

[0070] Referring to FIG. 5 , in some embodiments, the electrode structure 100 further includes a diaphragm 60, a second electrode 20, and a second insulating member 50. The first electrode 10, diaphragm 60, and second electrode 20 are stacked, with the diaphragm 60 disposed between the first electrode 10 and the second electrode 20 to prevent the first electrode 10 and the second electrode 20 from contacting and short-circuiting. The second electrode 20 may be provided with a third groove 25 and a fourth groove 26 as in the aforementioned embodiment, or may be omitted to meet design requirements. The second insulating member 50 is disposed on the surface of the second electrode 20, and its position corresponds to the position of the second groove 16 on the first electrode 10. The area of ​​the second insulating member 50 is less than or equal to the area of ​​the second groove 16. When the first electrode 10 and the second electrode 20 are stacked or wound to form a cell structure, the second insulating member 50 can be accommodated in the second groove 16, reducing thickness differences on the electrode surface and improving the surface consistency of the electrode.

[0071] In some embodiments, the first active material layer 12 is disposed on opposite sides of the first current collector 11. The second groove 16 extends through the first current collector 11 and the two first active material layers 12. The thickness of the second insulating member 50 is less than or equal to the sum of the thicknesses of the first current collector 11 and the two first active material layers 12. This reduces the risk of the second insulating member 50 protruding from the electrode surface, further improving the surface consistency of the electrode.

[0072] Referring to FIG. 7 , an embodiment of the present application further provides an electrochemical device 200, comprising the electrode structure 100 described in the above embodiment and a packaging shell 201. The electrode structure 100 is disposed within the packaging shell 201. The first electrode 10 and the second electrode 20 in the electrode structure 100 may be stacked or wound and housed within the packaging shell 201. The first electrode tab 30 and the second electrode tab 80 are electrically connected to the first electrode 10 and the second electrode 20, respectively, and extend out of the packaging shell 201 for electrical connection to an external circuit structure.

[0073] In the electrode structure 100, electrode manufacturing method and electrochemical device 200 of the present application, the first electrode 10 can be obtained by cutting along the cutting line 74 that passes through the middle area of ​​the empty foil area slot on the electrode mother sheet. The empty foil area slot forms a first groove 15 and a second groove 16 on both sides of the first electrode 10. There is no active material between the first groove 15 and the edge of the first electrode 10, and there is no need to perform secondary removal of the active material, thereby reducing the burrs in the first groove 15. The second groove 16 can pass through the first electrode 10 by secondary die-cutting, and the size of the second groove 16 is set to be larger than the size of the first groove 15, which can ensure that no empty foil area will remain in the second groove 16, and also reduce the safety risks caused by burrs, thereby fully improving the safety of use of the first electrode 10.

[0074] After the electrode structure 100 of the embodiment of the present application is used to prepare the electrochemical device 200, the electrochemical device 200 will undergo a puncture test (Nail) and an impact test (Impact) to test the product quality. The specific testing process is as follows.

[0075] Puncture test (Nail).

[0076] In a test environment of 20±5℃, place the sample on the test table and use a 4mm diameter steel nail to test from the center of the sample at a speed of 150mm / s. The sample must be completely pierced. Judgment standard: the sample does not catch fire or explode.

[0077] Impact test (Impact).

[0078] In a test environment of 20±5℃, place the sample on the test table. Use a round rod with a diameter of 15.8mm to be placed at the center of the wide side of the sample, with the round rod perpendicular to the long axis of the sample. Use a 9.1±0.1kg hammer to drop it vertically from a height of 610±25mm and drop it onto the intersection of the round rod and the sample. Judgment standard: the sample does not catch fire or explode.

[0079] Table 1

[0080] In Comparative Examples 1, 2, and 3, the difference ab between the dimensions of the second groove 16 and the first groove 15 along the length of the electrode sheet is -1 mm, 3 mm, and 0 mm, respectively, which does not meet the requirement of 0 < ab ≤ 2 mm in the embodiment. The test results of Comparative Examples 1 and 3 show that when the dimension of the second groove 16 along the length of the electrode sheet is less than or equal to that of the first groove 15, although the energy density loss is good, the test results of the puncture test and impact test are poor, demonstrating that the electrode structure is not safe for use. In Comparative Example 3, although ab is defined as being as low as 0 during the manufacturing process, since the manufacturing process cannot guarantee complete accuracy, process deviations still exist. Therefore, to achieve 100% safety, this application sets the difference ab to be greater than 0. The test results of Comparative Example 2 show that the dimension of the second groove 16 along the length of the electrode sheet is greater than that of the first groove 15. However, when it exceeds 2 mm, although the safety of the electrode structure is improved, it will lead to increased energy density loss, which is not conducive to improving the overall performance of the electrochemical device.

[0081] In Examples 1, 2, 3, 4, and 5, the difference ab between the dimensions of the second groove 16 and the first groove 15 along the length of the electrode sheet satisfies the requirement of 0 < ab ≤ 2 mm. The test results and energy density loss parameters of Examples 1-5 demonstrate that the electrode sheet structures of the present invention not only improve safety but also control energy density loss within an acceptable range, thereby comprehensively improving the performance of the electrochemical device.

[0082] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present application should not depart from the spirit and scope of the technical solutions of the present application.

Claims

1. A pole piece structure, characterized in that: include: A first pole piece includes a first current collector and a first active material layer, wherein the first active material layer is disposed on a surface of the first current collector; Along the width direction of the first pole piece, the first pole piece has a first side and a second side opposite to each other, the first side is provided with a first groove, and the second side is provided with a second groove; Along the width direction of the first pole piece, a projection of the second groove on the first side at least partially overlaps with the first groove; The first groove has a first empty foil area, and the second groove passes through the first pole piece along the thickness direction of the first pole piece; along the length direction of the first pole piece, the size of the second groove is larger than that of the first groove.

2. The pole piece structure according to claim 1, characterized in that: Along the length direction of the first pole piece, the size of the second groove is a, and the size of the first groove is b, wherein 0<ab≤2mm.

3. The pole piece structure according to claim 2, characterized in that: Along the length direction of the first pole piece, the dimensions of the second groove and the first groove satisfy 0.1 mm≤ab≤0.8 mm.

4. The pole piece structure according to claim 1, characterized in that: The electrode structure further includes a second electrode, the polarity of the second electrode is opposite to that of the first electrode; the second electrode includes a second current collector and a second active material layer, and the second active material layer is provided on the surface of the second current collector; Along the width direction of the second pole piece, the second pole piece has a third side and a fourth side opposite to each other, the third side is provided with a third groove, and the fourth side is provided with a fourth groove; Along the width direction of the second pole piece, a projection of the fourth groove on the third side at least partially overlaps with the third groove; The third groove has a second empty foil area, and the fourth groove passes through the second pole piece along the thickness direction of the second pole piece; along the length direction of the second pole piece, the size of the fourth groove is larger than that of the third groove.

5. The pole piece structure according to claim 4, characterized in that: The first pole piece is a cathode piece, the second pole piece is an anode piece, and the area of ​​the third groove is larger than the area of ​​the first groove.

6. The pole piece structure according to claim 5, characterized in that: The area of ​​the first groove is S1, the area of ​​the third groove is S2, 20mm 2 ≤S2-S1≤80mm 2 .

7. The pole piece structure according to claim 5, characterized in that: Along the length direction of the first pole piece, the size of the fourth groove is c, and the size of the second groove is a, wherein 0<ca≤2mm.

8. The pole piece structure according to claim 7, characterized in that: Along the length direction of the first pole piece, the dimensions of the fourth groove and the second groove satisfy 0.4 mm≤ca≤1.6 mm.

9. The pole piece structure according to claim 1, characterized in that: The second groove has a bottom wall and two side walls, the two side walls are spaced apart and connect the bottom wall and the second side edge, a first arc segment is defined between the side wall and the bottom wall, and a second arc segment is defined between the side wall and the second side edge.

10. The pole piece structure according to claim 1, characterized in that: Along the width direction of the first pole piece, the size of the first groove is f, and the size of the second groove is e, wherein f>e, 3≤f / e≤10.

11. The pole piece structure according to claim 10, characterized in that: The ratio of the size f of the first groove to the size e of the second groove is 3-6.

12. The pole piece structure according to claim 1, characterized in that: The first electrode tab is also included, wherein the first electrode tab is partially disposed in the first groove and is electrically connected to the first current collector, and the overlapping area between the first electrode tab and the first current collector is greater than or equal to 140 mm 2 .

13. The pole piece structure according to claim 12, characterized in that: The invention further includes a first insulating member, which is arranged on the surface of the first active material layer and covers the first groove. The area of ​​the first insulating member is larger than the area of ​​the first groove.

14. The pole piece structure according to claim 1, characterized in that: It also includes a diaphragm, a second pole piece and a second insulating member. The first pole piece, the diaphragm and the second pole piece are stacked. The second insulating member is arranged on the surface of the second pole piece, and the position of the second insulating member corresponds to the position of the second groove. The area of ​​the second insulating member is less than or equal to the area of ​​the second groove.

15. The pole piece structure according to claim 14, characterized in that: The first active material layer is disposed on two opposite surfaces of the first current collector; The thickness of the second insulating member is less than or equal to the sum of the thicknesses of the first current collector and the two first active material layers.

16. A method for manufacturing a pole piece, for manufacturing the pole piece structure according to any one of claims 1 to 15, characterized in that: The pole piece manufacturing method comprises: Providing a first pole piece mother sheet, wherein the first pole piece mother sheet includes a first current collector and a first active material layer disposed on a surface of the first current collector; A portion of the first active material layer is removed to form a first empty foil area slot, and a plurality of first empty foil area slots are arranged at intervals along the width direction of the first pole piece mother sheet; A cutting line is set along the length direction of the first pole piece mother sheet, and a plurality of the cutting lines pass through the first empty foil area respectively; Cutting the first pole piece mother sheet along the cutting line to form a plurality of first pole pieces, the cut first empty foil area is slotted on both sides of the first pole piece to form a first sub-empty foil area and a second sub-empty foil area, respectively, and the first sub-empty foil area forms a first groove; The side of the first pole piece having the second sub-empty foil area is cut to remove the second sub-empty foil area, thereby forming a second groove on the side of the first pole piece.

17. The pole piece manufacturing method according to claim 16, characterized in that: Also includes: The edge of the second groove is cut to form a first arc segment between the side wall and the bottom wall of the second groove, and a second arc segment is formed between the side wall of the second groove and the side edge of the first pole piece.

18. An electrochemical device, characterized in that It comprises the pole piece structure and packaging shell according to any one of claims 1 to 15, wherein the pole piece structure is arranged in the packaging shell.

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