Battery cell, battery cell manufacturing method, electrode sheet, and electrode sheet manufacturing method

Abstract

Provided are a battery cell, a battery cell manufacturing method, an electrode sheet, and an electrode sheet manufacturing method. The battery cell comprises an electrode assembly, wherein the electrode assembly comprises a plurality of first electrode sheets and a plurality of second electrode sheets, each first electrode sheet is provided with a first empty foil region, the first empty foil region is located at a first corner of the first electrode sheet, each second electrode sheet is provided with a first notch, and observed in a first direction, the first empty foil region at least partially overlaps with the first notch; and a plurality of first empty foil regions are stacked and folded in the first direction, and in the first direction, the maximum projection area of the plurality of first empty foil regions is S1, the overlapping portion between a region among the plurality of first empty foil regions that has the maximum projection area and a region among the plurality of first empty foil regions that has the minimum projection area is a first overlapping region, the area of the first overlapping region is S2, and 55%≤S2 / S1≤100%. By means of the battery cell of the structure, the current-carrying capacity of a plurality of first empty foil regions can be improved while the influence on the energy density of the battery cell is relatively small.

Description

Battery cell and battery cell manufacturing method, pole piece and pole piece manufacturing method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese patent application CN202410370899.X, filed on March 28, 2024, entitled “Battery Cell and Battery Cell Manufacturing Method, Pole Piece and Pole Piece Manufacturing Method,” and the entire contents of that application are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of battery cell technology, and in particular to a battery cell and a battery cell manufacturing method, a pole piece and a pole piece manufacturing method. Background Art

[0003] In the prior art, battery cells include electrode assemblies. When the electrode assemblies are laminated, the multiple tabs need to be folded together before being electrically connected to the adapter. However, after the multiple tabs are stacked, the overlapping area of ​​the tabs is small due to the thickness differences between the folded tabs. This results in poor connection security between the adapter and the tabs, and poor current handling capacity. Summary of the Invention

[0004] The present application provides a battery cell and a battery cell manufacturing method, a pole piece and a pole piece manufacturing method, which can improve the current capacity while having little impact on the energy density of the battery cell.

[0005] In a first aspect, embodiments of the present application provide a battery cell comprising an electrode assembly. The electrode assembly has a laminated structure, comprising a plurality of first electrode sheets and a plurality of second electrode sheets stacked along a first direction, the first electrode sheets having opposite polarities to the second electrode sheets, each first electrode sheet having a first hollow foil region located at a first corner of the first electrode sheet, and each second electrode sheet having a first notch. When viewed along the first direction, the first hollow foil region at least partially overlaps the first notch. The plurality of first hollow foil regions are stacked and converged in the first direction, and along the first direction, the maximum projected area of ​​the plurality of first hollow foil regions is S1. The overlapping portion of the largest projected area among the plurality of first hollow foil regions and the smallest projected area among the plurality of first hollow foil regions is a first overlapping area. The area of ​​the first overlapping area is S2, satisfying the condition 55% ≤ S2 / S1 ≤ 100%. Each first hollow foil region has a projected area, and the maximum / minimum projected area of ​​the plurality of first hollow foil regions refers to the projected area corresponding to the first hollow foil region with the largest / minimum projected area.

[0006] According to the battery cell of the embodiment of the present application, the first empty foil area is located at the first corner of the first electrode piece, the second electrode piece has a first notch, and the first empty foil area at least partially overlaps with the first notch, so that the first electrode piece and the second electrode piece can be respectively provided with more active materials; the area ratio of the first overlapping area to the maximum projected area of ​​the multiple first empty foil areas satisfies the above relationship (S2 / S1≥55%). When the multiple first empty foil areas occupy a small space, since the ratio of the area of ​​the first overlapping area to the maximum projected area of ​​the multiple first empty foil areas is large, the overlapping area of ​​the multiple first empty foil areas is sufficient to meet the overcurrent requirements and can even have a larger overcurrent area. The battery cell of the embodiment of the present application can improve the overcurrent capacity of the multiple first empty foil areas while having little impact on the energy density of the battery cell. Therefore, when the multiple first empty foil areas meet the overcurrent requirements, since the multiple first empty foil areas occupy a small space, the multiple first electrode pieces of the battery cell of the present application can have more active materials, so that the battery cell has a higher energy density.

[0007] In one or more of the above optional embodiments, 58%≤S2 / S1≤80%.

[0008] In the above scheme, compared with 55%≤S2 / S1≤100%, when 58%≤S2 / S1≤80%, the multiple first empty foil areas occupy a smaller space, and the multiple first empty foil areas further have a larger overlapping area, so that the battery cell has a higher energy density.

[0009] In one or more optional embodiments above, the shape of the first empty foil area is a triangle, and S1 and S2 satisfy: 70%≤S2 / S1≤80%.

[0010] In the above solution, the first hollow foil area is located at the first corner and is triangular in shape, facilitating manufacturing. Compared to 58% ≤ S2 / S1 ≤ 80%, when 70% ≤ S2 / S1 ≤ 80%, multiple first hollow foil areas occupy less space and have a larger overlapping area, resulting in a higher energy density for the battery cell.

[0011] In one or more of the above optional embodiments, the first electrode piece further has a first main body area, the first main body area is provided with a first active material layer, and the first empty foil area is not provided with the first active material layer; in the width direction of the first electrode piece, the edge of the first empty foil area is flush with the edge of the first main body area.

[0012] In the above solution, in the width direction of the first electrode, the edge of the first empty foil area is flush with the edge of the first main body area. On the one hand, it is convenient for multiple first empty foil areas to have a larger overlapping area, and on the other hand, it reduces the risk of interference between the first empty foil area and other components.

[0013] In one or more of the above optional embodiments, 90%≤S2 / S1≤100%.

[0014] In the above scheme, compared with 55%≤S2 / S1≤100%, when 90%≤S2 / S1≤100%, when multiple first empty foil areas occupy a smaller space, since the ratio of the area of ​​the first overlapping area to the maximum projected area of ​​the multiple first empty foil areas is larger, the overlapping area of ​​the multiple first empty foil areas is sufficient to meet the overcurrent requirements, and the space occupied by the multiple first empty foil areas can be further reduced, so that the first electrode can have a larger area of ​​active material, and the battery cell has a higher energy density.

[0015] In one or more optional embodiments above, the first electrode piece includes a first main body area provided with a first active material layer and a first empty foil area not provided with the first active material layer. Along the width direction of the first electrode piece, the first empty foil area is connected to the first main body area, and along the length direction of the first electrode piece, a first gap is formed between the first empty foil area and the first main body area, so that the first empty foil area can move relative to the first main body area along the connection with the first main body area; the shape of the first empty foil area is a quadrilateral.

[0016] In the above scheme, the shape of the first empty foil area is a quadrilateral, and a first gap is formed between the first empty foil area and the first main area to facilitate the folding of multiple first empty foil areas, so that the multiple first empty foil areas can have a larger overlapping area after folding, thereby making the area of ​​the first overlapping area larger than the maximum projected area of ​​the multiple first empty foil areas.

[0017] In one or more optional embodiments above, in the width direction of the first pole piece, the edge of the first empty foil area is flush with the edge of the first main body area; in the length direction of the first pole piece, the edge of the first empty foil area is flush with the edge of the first main body area.

[0018] In the above scheme, in the width direction of the first pole piece and the length direction of the first pole piece, the edges of the first empty foil area are flush with the edges of the first main body area. On the one hand, it is convenient for multiple first empty foil areas to have a larger overlapping area, and on the other hand, it reduces the risk of interference between the first empty foil area and other components.

[0019] In one or more of the above optional embodiments, the expanded areas of the plurality of first empty foil areas gradually increase along a direction opposite to a direction in which the plurality of first empty foil areas collapse.

[0020] In the above solution, when unfolding in the direction opposite to the folding direction of the first empty foil areas, the unfolding areas of the multiple first empty foil areas gradually increase, so that the multiple first empty foil areas can have a larger overlapping area while occupying a smaller assembly space after folding.

[0021] In one or more optional embodiments above, each first electrode also has a second notch, each second electrode has a second empty foil area, the second empty foil area is located at the second corner of the second electrode, and when viewed along the first direction, the second empty foil area at least partially overlaps with the second notch; multiple second empty foil areas are stacked and gathered in the first direction, and along the first direction, the projection area of ​​the multiple second empty foil areas is S3, and the projections of the multiple second empty foil areas have a second overlapping area, and the area of ​​the second overlapping area is S4, satisfying 55%≤S4 / S3≤100%.

[0022] In the above solution, the second hollow foil area is located at the second corner of the second electrode piece, the first electrode piece has a second notch, and the second hollow foil area at least partially overlaps with the second notch, so that the first electrode piece and the second electrode piece can each be provided with a larger amount of active material; the ratio of the area of ​​the second overlapping area to the projected area of ​​the plurality of second hollow foil areas satisfies the above relationship (S4 / S3 ≥ 55%). When the plurality of second hollow foil areas occupy a relatively small space, the ratio of the area of ​​the second overlapping area to the projected area of ​​the plurality of second hollow foil areas is relatively large, so that the overlapping area of ​​the plurality of second hollow foil areas is sufficient to meet the overflow requirement, and can even have a larger overflow area. Therefore, when the plurality of second hollow foil areas meet the overflow requirement, the plurality of second hollow foil areas occupy a relatively small space, so that the plurality of second electrode pieces can have a larger amount of active material, thereby facilitating an improvement in energy density.

[0023] In one or more of the above optional embodiments, the battery cell further includes a packaging bag, a first adapter and a second adapter, the electrode assembly is accommodated in the packaging bag, the first adapter is electrically connected to multiple first empty foil areas and extends out of the packaging bag, and the second adapter is electrically connected to multiple second empty foil areas and extends out of the packaging bag.

[0024] In the above solution, the battery cell can be a soft-pack battery cell with a higher energy density; the first adapter extends out of the packaging bag, and the second adapter extends out of the packaging bag to facilitate the extraction of electrical energy from the electrode assembly.

[0025] In one or more optional embodiments above, the electrode assembly further includes a diaphragm, which is disposed between adjacent first and second electrode sheets. The diaphragm has a third notch and a fourth notch. Along the first direction, the third notch at least partially overlaps with the first empty foil area, and the fourth notch at least partially overlaps with the second empty foil area.

[0026] In the above solution, the diaphragm can insulate and isolate the first and second electrode pieces, reducing the risk of short circuits caused by contact between the positive and negative electrodes. The third notch facilitates the folding of the multiple first empty foil areas, and the fourth notch facilitates the folding of the multiple second empty foil areas.

[0027] In a second aspect, embodiments of the present application further provide an electrode sheet comprising a current collector and an active material layer. The current collector comprises a main body region provided with the active material layer and a hollow foil region not provided with the active material layer; the main body region comprises a first edge, a second edge, and a third edge, the first edge and the second edge being arranged relative to each other along a second direction perpendicular to the thickness direction of the electrode sheet; the third edge being located between the first edge and the second edge; the hollow foil region being located at a corner formed by the second edge and the third edge, the corner formed by the first edge and the third edge being provided with a notch; the hollow foil region comprises a first portion and a second portion arranged continuously, the first portion protruding from the second edge and the second portion not protruding from the second edge along the second direction, and the first portion and the notch being complementary.

[0028] According to the electrode of the embodiment of the present application, the first part of the empty foil area protrudes from the second edge, and the outline of the first part matches the outline of the gap, and the first part can fill the gap. During the processing and manufacturing process of the electrode, multiple electrode sheets can be cut out from the continuous strip structure. On the one hand, it is convenient for the processing and manufacturing of the electrode sheet. On the other hand, when the electrode sheets constitute an electrode assembly of a stacked structure, the multiple stacked empty foil areas can have a larger overlapping area, thereby improving the current flow capacity of the multiple empty foil areas, and the multiple empty foil areas occupy a smaller assembly space, so as to improve the energy density of the battery cell.

[0029] In one or more of the above optional embodiments, the empty foil area includes a first outer edge and a second outer edge, the first outer edge is flush with the third edge, and the second outer edge matches the contour of the notch.

[0030] In the above scheme, the second outer edge matches the contour of the notch. During the processing and manufacturing process of the pole piece, the pole piece strip can be cut into multiple pole pieces, so that the pole piece strip can be cut into two complementary pole pieces through the second outer edge and the second edge, which facilitates processing and manufacturing and reduces material waste.

[0031] In one or more of the above optional embodiments, the second outer edge is a straight line segment, a curved line segment or a broken line segment.

[0032] In the above solution, the contour of the second outer edge can be in various styles to facilitate processing and manufacturing.

[0033] In one or more of the above optional embodiments, the first portion and the second portion are symmetrically arranged along an extension line of the second edge.

[0034] In the above solution, the first part and the second part are symmetrically arranged about the second edge, which facilitates processing and manufacturing.

[0035] On the third aspect, an embodiment of the present application also provides a method for manufacturing an electrode, which includes: providing a electrode strip, the electrode strip including a current collector and an active material layer, the current collector having a main body area provided with an active material layer and multiple empty foil areas without active material layers, the current collector having a first side edge and a second side edge opposite to each other along the width direction of the electrode strip, and the multiple empty foil areas are spaced apart along the first side edge; cutting the electrode strip along a preset trajectory to form a electrode with complementary empty foil areas and notches; wherein the preset trajectory includes a first segment and a second segment arranged continuously, one end of the first segment is located at the first side edge, one end of the second segment is located at the second side edge, and the first segment coincides with the boundary line between the empty foil area and the main body area.

[0036] According to the electrode sheet manufacturing method of the embodiment of the present application, starting from the first side edge, the electrode sheet strip is cut along a preset trajectory to form multiple electrode sheets, so that the hollow foil area of ​​one electrode sheet complements the gap of the adjacent electrode sheet, facilitating processing and reducing material waste. Furthermore, after the electrode sheets are stacked and folded together, the hollow foil areas of the multiple electrode sheets have a large overlapping area, and the battery cell has more active material and a higher energy density.

[0037] In one or more optional embodiments above, providing the electrode strip includes: coating the active material on the surface of the current collector; and cleaning a portion of the active material on the current collector to form a plurality of empty foil areas that are spaced apart.

[0038] In the above scheme, the entire current collector can be coated when the active material is coated, the coating process is simple, and the processing and manufacturing are convenient. The empty foil area is formed by washing, which has high processing and manufacturing efficiency.

[0039] In one or more optional embodiments above, providing the electrode strip includes: attaching a plurality of spaced-apart shielding members on the surface of the current collector; coating the active material on the surface of the current collector; and separating the shielding members from the current collector to form a plurality of spaced-apart empty foil areas.

[0040] In the above scheme, the active material can be applied continuously during coating, and the coating process is simple. The hollow foil area is formed by shielding, and after the active material is applied, the shielding member can be separated from the current collector, which is easy to process and manufacture.

[0041] In a fourth aspect, an embodiment of the present application also provides a method for manufacturing a battery cell, which includes: providing a first electrode piece and a second electrode piece, the first electrode piece and the second electrode piece being the electrode pieces provided in any embodiment, the first electrode piece having a first hollow foil area, a first main area and a second notch, and the second electrode piece having a first notch, a second hollow foil area and a second main area; along a first direction, arranging a plurality of first electrode pieces and a plurality of second electrode pieces in an alternating and stacked manner so that the first hollow foil area is exposed to the first notch and the second hollow foil area is exposed to the second notch; along the first direction, folding a plurality of first hollow foil areas and folding a plurality of second hollow foil areas; in the width direction of the first electrode piece, cutting off the portion of the first hollow foil area that exceeds the edge of the first main area, and cutting off the portion of the second hollow foil area that exceeds the edge of the second main area, wherein the width direction of the first electrode piece, the second direction and the first direction are perpendicular to each other.

[0042] According to the battery cell manufacturing method of the embodiment of the present application, in the manufactured battery cell, the multiple first empty foil areas and the multiple second empty foil areas all have a large overlapping area, which meets the overcurrent requirements, and the multiple first empty foil areas and the multiple second empty foil areas occupy a small space, so more active materials can be set, so that the battery cell has a higher energy density.

[0043] 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

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. 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.

[0045] FIG1 is a cross-sectional view of a pole piece provided in some embodiments of the present application;

[0046] FIG2 is a schematic diagram of the structure of a pole piece provided in some embodiments of the present application;

[0047] FIG3 is a schematic structural diagram of pole pieces provided in other embodiments of the present application;

[0048] FIG4 is a schematic structural diagram of pole pieces provided in some other embodiments of the present application;

[0049] FIG5 is a schematic diagram of the structure of a pole piece strip provided in some embodiments of the present application;

[0050] FIG6 is a schematic diagram of a partial structure of a battery cell provided in some embodiments of the present application;

[0051] FIG7 is a schematic diagram of the structure of an electrode assembly before cutting provided in some embodiments of the present application;

[0052] FIG8 is a schematic structural diagram of a first pole piece before lamination provided in some embodiments of the present application;

[0053] FIG9 is a schematic structural diagram of a second pole piece before lamination and cutting provided in some embodiments of the present application;

[0054] FIG10 is a schematic diagram of a partial structure of a battery cell provided in some other embodiments of the present application;

[0055] FIG11 is a schematic structural diagram of a first electrode piece having a quadrilateral first empty foil area provided in some embodiments of the present application;

[0056] FIG12 is a schematic structural diagram of a second electrode piece having a quadrilateral second empty foil area provided in some embodiments of the present application;

[0057] FIG13 is a schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0058] FIG14 is a schematic diagram of the structure of the diaphragm provided in some embodiments of the present application.

[0059] Icons: 1-pole piece; 11-current collector; 12-active material layer; 13-main body area; 131-first edge; 132-second edge; 133-third edge; 14-empty foil area; 141-first part; 142-second part; 143-first outer edge; 144-second outer edge; 15-notch; 20-pole piece strip; 21-first side edge; 22-second side edge; 23-preset track; 231-first section; 232-second section; 30-electrode assembly; 31-first pole piece; 31a-first corner position; 31b-third corner position; 311-first empty foil area; 312- First main body area; 313-first overlapping area; 314-second notch; 315-first gap; 32-second pole piece; 32a-second corner; 32b-fourth corner; 321-first notch; 322-second empty foil area; 323-second main body area; 324-second overlapping area; 325-second gap; 33-diaphragm; 33a-fifth corner; 33b-sixth corner; 331-third notch; 332-fourth notch; 40-packaging bag; 50-first adapter; 60-second adapter; 100-battery cell; X-first direction; Y-second direction; Z-length direction of the pole piece. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0061] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first" and "second" in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary-secondary relationship.

[0062] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0063] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," and "attached" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0064] The term "and / or" in this application simply describes an association between related objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally indicates that the related objects are in an "or" relationship.

[0065] The term "multiple" in this application refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0066] In the prior art, electrode sheets are typically manufactured in a rectangular structure. When multiple electrode sheets are stacked and their hollow foil areas are folded together, the overlapping area of ​​the hollow foil areas decreases in the stacking direction, resulting in a smaller connection area between the hollow foil areas and the adapter. To meet the connection requirements between the multiple hollow foil areas and the adapter, the area of ​​the hollow foil areas is often increased. However, this reduces the area of ​​the active material in the electrode sheets, affecting the energy density of the battery cell.

[0067] In the prior art, in order to increase the flow area, the overlapping area of ​​multiple empty foil areas is increased, which leads to a decrease in the energy density of the battery cell. The present application provides a technical solution, wherein an electrode assembly includes a plurality of first electrode sheets and a plurality of second electrode sheets stacked along a first direction, the first electrode sheets and the second electrode sheets having opposite polarities, each first electrode sheet having a first empty foil area, the first empty foil area being located at a first corner of the first electrode sheet, the second electrode sheet having a first notch, the first empty foil area at least partially overlapping with the first notch, and since the plurality of first empty foil areas are stacked and folded in the first direction, there is a thickness difference between the first empty foil area and the electrode sheet body, and therefore the plurality of first empty foil areas have a plurality of projected areas of different sizes after folding, taking folding from the top layer to the bottom layer as an example, the projected area of ​​the top layer along the first direction after folding is the smallest, and the projected area of ​​the bottom layer along the first direction after folding is the largest, along the first direction, the maximum projected area of ​​the plurality of first empty foil areas is S1, the overlapping part of the largest projected area among the plurality of first empty foil areas and the smallest projected area among the plurality of first empty foil areas is the first overlapping area, and the area of ​​the first overlapping area is S2, satisfying 55%≤S2 / S1≤100%. In the present application, when multiple first empty foil areas occupy a relatively small space, since the ratio of the area of ​​the first overlapping region to the maximum projected area of ​​the multiple first empty foil areas is relatively large, the overlapping area of ​​the multiple first empty foil areas is sufficient to meet the overcurrent requirement, and can even have a relatively large overcurrent area. The battery cell of the embodiment of the present application can improve the overcurrent capacity of the multiple first empty foil areas while having little impact on the energy density of the battery cell. Therefore, compared with the prior art with the same overlapping area of ​​multiple first empty foil areas, when multiple first empty foil areas meet the overcurrent requirement, since the multiple first empty foil areas of the present application occupy a relatively small space, the multiple first pole pieces of the battery cell of the present application can have more active materials, so that the battery cell has a higher energy density.

[0068] The pole piece provided in the embodiment of the present application will be described below with reference to the accompanying drawings.

[0069] 1 and 2 , an embodiment of the present application provides a pole piece 1 , which includes a current collector 11 and an active material layer 12 . The current collector 11 includes a main body area 13 provided with the active material layer 12 and a hollow foil area 14 not provided with the active material layer 12 .

[0070] The current collector 11 is a sheet-like structure and can be a metal foil or a composite current collector.

[0071] The active material layer 12 may be an active material coated on the surface of the current collector 11 or may be an active material pressed onto the surface of the current collector 11 .

[0072] The main body area 13 includes a first edge 131, a second edge 132 and a third edge 133. The first edge 131 and the second edge 132 are arranged relative to each other along the second direction Y, and the second direction Y is perpendicular to the thickness direction of the electrode 1. The third edge 133 is located between the first edge 131 and the second edge 132. The empty foil area 14 is located at the corner formed by the second edge 132 and the third edge 133. A notch 15 is provided at the corner formed by the first edge 131 and the third edge 133.

[0073] In some embodiments, the electrode 1 may be substantially rectangular, the third edge 133 may be located at one end of the length direction Z of the electrode, and the second direction Y may be parallel to the width direction of the electrode 1. The hollow foil area 14 and the notch 15 are located at both ends of the third edge 133. The hollow foil area 14 and the notch 15 are located at two adjacent corners of the electrode 1 to facilitate processing and manufacturing.

[0074] For ease of description, please refer to FIG. 1 and FIG. 2 , the thickness direction of the pole piece 1 may be parallel to the X direction.

[0075] The empty foil area 14 includes a first portion 141 and a second portion 142 that are continuously arranged. Along the second direction Y, the first portion 141 protrudes from the second edge 132 , and the second portion 142 does not protrude from the second edge 132 . The first portion 141 is complementary to the notch 15 .

[0076] An extension line P of the second edge 132 may be a boundary line between the first portion 141 and the second portion 142 .

[0077] The first portion 141 is a portion of the empty foil area 14 that extends beyond the second edge 132 in the second direction Y.

[0078] The first part 141 and the notch 15 are complementary in that the contour of the first part 141 matches the contour of the notch 15. For example, during the manufacturing process of the pole piece 1, a plurality of pole pieces 1 can be cut out from a continuous strip of material. In two adjacent pole pieces 1, the first part 141 of one pole piece 1 matches the notch 15 of the other pole piece 1.

[0079] According to the electrode piece 1 of the embodiment of the present application, the first part 141 of the empty foil area 14 protrudes from the second edge 132, and the outline of the first part 141 matches the outline of the gap 15. The first part 141 can fill the gap 15. During the processing and manufacturing process of the electrode piece 1, a plurality of electrode pieces 1 can be cut out from a continuous strip structure. On the one hand, it is convenient for processing and manufacturing the electrode piece 1. On the other hand, when the electrode piece 1 constitutes an electrode assembly of a laminated structure, the plurality of stacked empty foil areas 14 can have a larger overlapping area, and the plurality of empty foil areas 14 occupy a smaller assembly space, so as to improve the energy density of the battery cell.

[0080] 2 , in one or more optional embodiments above, the empty foil area 14 includes a first outer edge 143 and a second outer edge 144 . The first outer edge 143 is flush with the third edge 133 , and the second outer edge 144 matches the contour of the notch 15 .

[0081] The first outer edge 143 is flush with the third edge 133 , which means that the first outer edge 143 and the third edge 133 are the same processed edge, and the first outer edge 143 and the third edge 133 are substantially collinear, and a processing error may exist.

[0082] The first outer edge 143 is flush with the third edge 133 , which facilitates the processing and manufacturing of the pole piece 1 .

[0083] The second outer edge 144 matches the contour of the notch 15. During the processing and manufacturing process of the pole piece 1, after the pole piece material strip is cut along the cutting track, the contour of the second outer edge 144 of one pole piece 1 in two adjacent pole pieces 1 matches the contour of the notch 15 of the other pole piece 1.

[0084] In the above scheme, the second outer edge 144 matches the contour of the notch 15. During the processing and manufacturing process of the pole piece 1, the pole piece strip can be cut into multiple pole pieces 1, so that the pole piece strip can be cut into two complementary pole pieces 1 through the second outer edge 144 and the second edge 132, which facilitates processing and manufacturing and reduces material waste.

[0085] In one or more of the above optional embodiments, the second outer edge 144 is a straight line segment, a curved line segment, or a broken line segment.

[0086] In the above solution, the contour of the second outer edge 144 can be in various styles to facilitate processing and manufacturing.

[0087] In some embodiments, the second outer edge 144 may be a straight line segment intersecting the second edge 132 .

[0088] In some embodiments, the first edge 131 , the second edge 132 and the third edge 133 may all be straight line segments, the straight line where the first edge 131 is located is perpendicular to the straight line where the third edge 133 is located, and the straight line where the second edge 132 is located is perpendicular to the straight line where the third edge 133 is located.

[0089] Referring to FIG. 2 , in one or more of the above optional embodiments, the shape of the empty foil area 14 is a triangle.

[0090] For example, the first outer edge 143 and the second outer edge 144 are both straight line segments, and the first outer edge 143 may be the base of a triangle.

[0091] In some embodiments, please refer to Figure 2. In the Y direction, the length of the first outer edge 143 is L1, and in the Z direction, the shortest distance between the end of the second outer edge 144 away from the first outer edge 143 and the first outer edge 143 is L2, satisfying L1≤60mm, L2≤30mm.

[0092] When the first outer edge 143 is the base of a triangle, the shortest distance between the end of the second outer edge 144 away from the first outer edge 143 and the first outer edge 143 may be the height of the triangle.

[0093] When the first outer edge 143 and the second outer edge 144 are both straight line segments, L2 may be the size of a line segment intercepted by a line passing through an end of the second outer edge 144 away from the first outer edge 143 and perpendicular to the first outer edge 143 .

[0094] When L1≤60mm and L2≤30mm, after the multiple pole pieces 1 are stacked and the empty foil areas 14 of the multiple pole pieces 1 are folded together, the empty foil areas 14 of the multiple pole pieces 1 have a higher overlapping area, and the empty foil areas 14 occupy a smaller assembly space, so that the battery cell can have a higher energy density.

[0095] In the above scheme, the shape of the empty foil area 14 is triangular, which is convenient for processing and manufacturing; the length of the first outer edge 143 and the shortest distance between the end of the second outer edge 144 away from the first outer edge 143 and the first outer edge 143 satisfy the above relationship. After the multiple pole pieces 1 are stacked and folded together, the empty foil areas 14 of the multiple pole pieces 1 have a larger overlapping area, so there is no need to set an excessively large empty foil area, thereby enabling the battery cell to have a higher energy density.

[0096] Referring to FIG. 2 , in one or more of the above optional embodiments, the first portion 141 and the second portion 142 are symmetrically arranged about the second edge 132 .

[0097] The second edge 132 may be a straight line segment, and the straight line where the second edge 132 is located may be a symmetric center line of the first portion 141 and the second portion 142 , so that the first portion 141 and the second portion 142 are symmetrically arranged about the straight line where the second edge 132 is located.

[0098] In the above solution, the first portion 141 and the second portion 142 are symmetrically arranged about the second edge 132 , which facilitates processing and manufacturing.

[0099] In the embodiment where the second edge 132 is a straight line segment and the empty foil area 14 is a triangle, when the first outer edge 143 and the second outer edge 144 are both straight line segments, the first outer edge 143 can be perpendicular to the second edge 132, and the shape of the empty foil area 14 can be an isosceles triangle.

[0100] In some embodiments, the shape of the empty foil area 14 can be a quadrilateral (see FIG. 3 ), a hexagon (see FIG. 4 ), or other polygonal shapes.

[0101] The following will introduce a method for manufacturing a pole piece, which is used to manufacture the pole piece 1 provided in any of the above embodiments.

[0102] According to some embodiments of the present application, the present application also provides a method for manufacturing a pole piece, which includes:

[0103] S100: Provide a pole piece strip 20. Referring to FIG5 , the pole piece strip 20 includes a current collector and an active material layer. The current collector has a main body region 13 provided with the active material layer and a plurality of hollow foil regions 14 not provided with the active material layer. The current collector has a first side edge 21 and a second side edge 22 opposite to each other along the width direction Z1 of the pole piece strip. The plurality of hollow foil regions 14 are spaced apart along the first side edge 21.

[0104] S200 , cutting the electrode strip 20 along a predetermined trajectory 23 to form an electrode 1 having a complementary hollow foil region 14 and a notch 15 (see FIG2 ). The predetermined trajectory 23 includes a first segment 231 and a second segment 232 , each of which is continuously arranged. One end of the first segment 231 is located at the first side edge 21 , and one end of the second segment 232 is located at the second side edge 22 . The first segment 231 coincides with the boundary line between the hollow foil region 14 and the main body region 13 .

[0105] In step "S100, providing a pole piece strip 20", the pole piece strip 20 is a continuous structure and has a certain length. The first side edge 21 and the second side edge 22 are parallel to each other (parallel here means approximately parallel, and processing errors are allowed, and the errors can be allowed within 0.5mm). The first side edge 21 and the second side edge 22 are both straight segments. A plurality of empty foil areas 14 are arranged at intervals along the first side edge 21, and the outer edge of each empty foil area 14 coincides with the first side edge 21.

[0106] During the manufacturing process of the electrode strip 20 , active material slurry may be coated on the current collector to form an active material layer, and a plurality of spaced empty foil areas 14 may be provided at the first side edge 21 of the current collector.

[0107] In step “ S200 , cutting the pole piece strip 20 along the preset track 23 to form a first pole piece 31 having complementary empty foil areas 14 and notches 15 ”, the pole piece strip 20 may be cut by laser cutting.

[0108] In step "S200, cutting the electrode material strip 20 along the preset trajectory 23 to form a first electrode 31 having a complementary empty foil area 14 and a notch 15", the preset trajectory 23 can extend from the first side edge 21 toward the second side edge 22. During the cutting process, the cutting tool starts from the first side edge 21 and cuts the electrode material strip 20 along the first section 231 and the second section 232 in sequence until the second side edge 22. Among them, after the cutting tool cuts the electrode material strip 20 along the first section 231, the part of the boundary line between the empty foil area 14 and the main body area 13 is disconnected; after the cutting tool cuts the electrode material strip 20 along the second section 232, the cutting of the two adjacent electrode sheets 1 is completed, so that in the two adjacent electrode sheets 1, the empty foil area 14 of one electrode sheet 1 is complementary to the notch 15 of the other electrode sheet 1.

[0109] The length direction Z of the pole piece may be parallel to the width direction Z1 of the pole piece strip, and the width direction of the pole piece 1 may be parallel to the length direction Y1 of the pole piece strip.

[0110] According to the electrode sheet manufacturing method of the embodiment of the present application, starting from the first side edge 21, the electrode sheet strip 20 is cut along the preset trajectory 23 to form multiple electrode sheets 1, so that the hollow foil area 14 of one electrode sheet 1 complements the notch 15 of the adjacent electrode sheet 1, which facilitates processing and reduces material waste. At the same time, after the electrode sheets 1 manufactured by the above method are stacked and folded, the hollow foil areas 14 of the multiple electrode sheets 1 have a larger overlapping area, thereby improving the flow capacity of the multiple hollow foil areas 14, and the battery cell has more active material and a higher energy density.

[0111] In some embodiments, in step "S200, cutting the pole piece strip 20 along a preset trajectory 23 to form a pole piece 1 having a complementary empty foil area 14 and a notch 15", the cutting tool can also start from the second side edge 22, and cut the pole piece strip 20 along the second section 232 and the first section 231 in sequence until the first side edge 21.

[0112] In one or more optional embodiments above, providing the pole piece strip 20 includes:

[0113] S110, coating the active material on the surface of the current collector;

[0114] S120 , cleaning a portion of the active material on the current collector to form a plurality of empty foil areas 14 that are spaced apart.

[0115] In step “ S110 , coating the active material on the surface of the current collector”, the active material is coated on the entire surface of the current collector, that is, the active material layer extends from the first side edge 21 to the second side edge 22 .

[0116] In step “S120, cleaning a portion of the active material on the current collector”, a portion of the active material layer may be removed by laser cleaning, and the active material layer may be cleaned at intervals along the extension direction of the first side edge 21, thereby forming a plurality of empty foil areas 14 distributed at intervals.

[0117] In the above solution, the entire current collector can be coated when the active material is coated, the coating process is simple, and the processing and manufacturing are convenient. The empty foil area 14 is formed by washing, which has high processing and manufacturing efficiency.

[0118] In one or more optional embodiments above, providing the pole piece strip 20 includes:

[0119] S130, attaching a plurality of shielding members spaced apart on the surface of the current collector;

[0120] S140, coating the active material on the surface of the current collector;

[0121] S150 , separating the shielding member from the current collector to form a plurality of empty foil areas 14 that are spaced apart.

[0122] In step S130 , attaching a plurality of shielding members disposed at intervals on the surface of the current collector, the plurality of shielding members are disposed on the first side edge 21 and are distributed at intervals along the first side edge 21 .

[0123] In step “ S140 , coating the active material on the surface of the current collector”, the active material layer extends from the first side edge 21 to the second side edge 22 , and the active material layer covers the shielding member to achieve continuous coating.

[0124] In step “S150, separating the shielding member from the current collector”, the overlapping area of ​​the shielding member and the current collector can match the outline of the empty foil area 14. After the shielding member is separated from the current collector, the area of ​​the current collector shielded by the shielding member forms the empty foil area 14.

[0125] In the above scheme, the active material can be continuously coated, and the coating process is simple. The hollow foil area 14 is formed by shielding. After the active material is coated, the shielding member can be separated from the current collector, which is easy to process and manufacture.

[0126] The following describes the battery cell provided by the embodiments of the present application. The electrode 1 provided by any of the above embodiments is used to form the first electrode and the second electrode of the battery cell. The first electrode and the second electrode have opposite polarities. The first electrode and the second electrode are manufactured using the above electrode manufacturing method.

[0127] Please refer to Figures 6 to 9. Figure 6 shows a partial structure of the battery cell, and only shows a schematic diagram of the assembly of the electrode assembly and the first adapter and the second adapter. Figure 7 is a schematic diagram of the uncut edge of the electrode assembly provided in an embodiment of the present application, in which a plurality of first pole pieces and a plurality of second pole pieces are stacked, and the first empty foil areas of the plurality of first pole pieces are folded together, and the second empty foil areas of the plurality of second pole pieces are folded together; after completing the folding of the plurality of first empty foil areas and the folding of the plurality of second empty foil areas, the plurality of first empty foil areas and the plurality of second empty foil areas are cut respectively to cut off the first empty foil areas that exceed the edge of the first pole piece and to cut off the second empty foil areas that exceed the edge of the second pole piece, so that the electrode assembly forms the structure shown in Figure 6. Figure 8 shows a schematic diagram of the structure of the first pole piece, and Figure 9 shows a schematic diagram of the structure of the second pole piece. According to some embodiments of the present application, the embodiment of the present application also provides a battery cell 100, which includes an electrode assembly 30. The electrode assembly 30 is a laminated structure, and includes a plurality of first pole pieces 31 and a plurality of second pole pieces 32 stacked along a first direction X. The first pole pieces 31 and the second pole pieces 32 have opposite polarities.

[0128] The first electrode piece 31 may be a negative electrode piece, and the second electrode piece 32 may be a positive electrode piece; or the first electrode piece 31 may be a positive electrode piece, and the second electrode piece 32 may be a negative electrode piece.

[0129] The length direction of the first pole piece 31 is parallel to the length direction of the second pole piece 32, and the width direction of the first pole piece 31 is parallel to the width direction of the second pole piece 32. The length direction of the first pole piece 31 is parallel to the Z direction, and the width direction of the first pole piece 31 is parallel to the Y direction.

[0130] 6 , 8 and 9 , each first electrode piece 31 has a first empty foil area 311 located at a first corner 31 a of the first electrode piece 31 , and each second electrode piece 32 has a first notch 321 . When viewed along the first direction X, the first empty foil area 311 and the first notch 321 at least partially overlap.

[0131] The first electrode plate 31 further has a first main body region 312 , in which a first active material layer is provided. The first empty foil region 311 is not provided with the first active material layer.

[0132] The first empty foil area 311 is located at the first corner 31a of the first electrode 31 , and the first empty foil area 311 at least partially overlaps with the first notch 321 , so that the first electrode 31 can be provided with more first active material layers, and the second electrode 32 can be provided with more second active material layers.

[0133] In some embodiments, when viewed along the first direction X, the first empty foil area 311 partially overlaps with the first notch 321 , or the first empty foil area 311 completely overlaps with the first notch 321 .

[0134] In some embodiments, the first notch 321 is formed at an edge of the second pole piece 32 .

[0135] Observed along the first direction X, the first empty foil areas 311 are exposed to the first notches 321 , so that the plurality of first empty foil areas 311 can be folded together, thereby facilitating connection between the plurality of first empty foil areas 311 and the adapter and reducing the risk of short circuit between the positive and negative electrodes.

[0136] 6 and 7 , a plurality of first empty foil areas 311 are stacked and gathered in a first direction X. Along the first direction X, a maximum projection area of ​​the plurality of first empty foil areas 311 is S1. An overlapping portion of a region with the largest projection area among the plurality of first empty foil areas 311 and a region with the smallest projection area among the plurality of first empty foil areas 311 is a first overlapping area 313. An area of ​​the first overlapping area 313 is S2, satisfying the condition 55% ≤ S2 / S1 ≤ 100%.

[0137] The first overlapping region 313 is the overlapping region of the maximum projections of the plurality of first empty foil regions 311 along the first direction X after the plurality of first empty foil regions 311 are gathered together. In other words, it is the overlapping portion of the first empty foil region 311 with the largest projected area among the plurality of first empty foil regions 311 and the first empty foil region 311 with the smallest projected area among the plurality of first empty foil regions 311. When the plurality of first empty foil regions 311 are gathered together from top to bottom along the first direction X, the projected area of ​​the first empty foil region 311 in the topmost layer is the smallest, and the projected area of ​​the first empty foil region 311 in the bottommost layer is the largest.

[0138] The maximum projection area of ​​the plurality of first empty foil areas 311 is measured by using an image sensor (such as an industrial camera) to capture images of the plurality of first empty foil areas 311 along the first direction X to obtain the maximum projection area of ​​the plurality of first empty foil areas 311 .

[0139] The area of ​​the first overlapping region 313 is measured by using an image sensor (such as an industrial camera) to capture an image of the first overlapping region 313 along the direction of convergence of the plurality of first empty foil areas 311 to obtain the area of ​​the first overlapping region 313 .

[0140] S2 / S1 refers to the ratio of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the plurality of first empty foil areas 311 .

[0141] When S2 / S1 ≥ 55%, the plurality of first empty foil regions 311 have a larger overlapping area under the premise that the plurality of first empty foil regions 311 occupy a smaller assembly space.

[0142] Optionally, S2 / S1 may be, but is not limited to, 55%, 58%, 58.37%, 65.83%, 70%, 73.73%, 80%, 90%, 99.85%, 100%, etc.

[0143] According to the battery cell 100 of the embodiment of the present application, the first hollow foil area 311 is located at the first corner 31a of the first electrode sheet 31, and the second electrode sheet 32 ​​has a first notch 321. The first hollow foil area 311 and the first notch 321 at least partially overlap, so that the first electrode sheet 31 and the second electrode sheet 32 ​​can each be provided with a large amount of active material. The ratio of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the plurality of first hollow foil areas 311 satisfies the aforementioned relationship (S2 / S1≥55%). When the plurality of first hollow foil areas 311 occupy a small space, the ratio of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the plurality of first hollow foil areas 311 is large, so that the overlapping area of ​​the plurality of first hollow foil areas 311 is sufficient to meet the overflow requirement, and can even have a larger overflow area. Therefore, when the plurality of first hollow foil areas 311 meet the overflow requirement, the plurality of first hollow foil areas 311 occupy a small space, so that the plurality of first electrode sheets 31 can be provided with a large amount of active material, thereby improving the energy density of the battery cell 100. The battery cell of the present embodiment can improve the current capacity of the multiple first hollow foil areas while having little impact on the energy density of the battery cell. That is, when the overlapping area of ​​the multiple first hollow foil areas 311 is the same, the multiple first electrode sheets 31 of the battery cell 100 of the present application can have more active material, thereby achieving a higher energy density of the battery cell 100.

[0144] Depending on the shape of the first empty foil regions 311 , the ratio of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the plurality of first empty foil regions 311 may be different.

[0145] For example, referring to Figures 10 and 11, when the shape of the first empty foil area 311 is rectangular, in order to facilitate the folding of the multiple first empty foil areas 311, the first electrode 31 is provided with a first slit 315. The first slit 315 is arranged along a partial boundary line between the first empty foil area 311 and the first main area 312, so that the first empty foil area 311 can move relative to the first main area 312, so that the area of ​​the first overlapping area 313 and the maximum projected area of ​​the multiple first empty foil areas 311 can be 100%.

[0146] In one or more of the above optional embodiments, 58%≤S2 / S1≤80%.

[0147] In the above solution, compared with 55%≤S2 / S1≤100%, when 58%≤S2 / S1≤80%, the multiple first empty foil areas 311 occupy a smaller space, and the multiple first empty foil areas 311 further have a larger overlapping area, so that the battery cell 100 has a higher energy density.

[0148] In one or more optional embodiments above, the shape of the first empty foil area 311 is a triangle, and S1 and S2 satisfy: 70%≤S2 / S1≤80%.

[0149] In the above solution, first hollow foil area 311 is located at first corner 31a and is triangular in shape, facilitating manufacturing. Compared to 58% ≤ S2 / S1 ≤ 80%, when 70% ≤ S2 / S1 ≤ 80%, multiple first hollow foil areas 311 occupy less space and have a larger overlapping area, resulting in a higher energy density for the battery cell 100.

[0150] In one or more of the above optional embodiments, in the width direction of the first pole piece 31 , the edge of the first hollow foil region 311 is flush with the edge of the first main body region 312 .

[0151] It can be understood that after the multiple first empty foil areas 311 are folded together, the portions of the multiple first empty foil areas 311 that extend beyond the edge of the first main area 312 in the width direction of the first electrode 31 are cut off, so that in the width direction of the first electrode 31, the edge of the first empty foil area 311 is flush with the edge of the first main area 312. Because the first empty foil area 311 is in the shape of a triangle, there is a situation of shrinkage due to thickness difference when the first electrode 31 is folded together in both the length direction and the width direction. Since the first electrode 31 of the present application has a margin only in the width direction, the portion that extends beyond the edge of the first main area 312 is cut off after folding, thereby ensuring that the edge of the first empty foil area 311 in the width direction is flush with the edge of the first main area 312. It should be noted that the flush here means roughly flush, and there can be a processing error within 0.5mm.

[0152] In the above scheme, in the width direction of the first electrode 31, the edge of the first empty foil area 311 is flush with the edge of the first main body area 312. On the one hand, it is convenient for multiple first empty foil areas 311 to have a larger overlapping area; on the other hand, it reduces the risk of interference between the first empty foil area 311 and other components, for example, reducing the risk of short circuit between the first electrode 31 and the second electrode 32, and for another example, reducing the risk of interference between the first electrode 31 and the packaging of the package.

[0153] In one or more of the above optional embodiments, 90%≤S2 / S1≤100%.

[0154] In the above scheme, compared with 55%≤S2 / S1≤100%, when 90%≤S2 / S1≤100%, when multiple first empty foil areas 311 occupy a smaller space, since the ratio of the area of ​​the first overlapping area 313 to the maximum projected area of ​​the multiple first empty foil areas 311 is larger, the overlapping area of ​​the multiple first empty foil areas 311 is sufficient to meet the overcurrent requirement, and the space occupied by the multiple first empty foil areas 311 can be further reduced, so that the first electrode 31 can have a larger area of ​​active material, so that the battery cell 100 has a higher energy density.

[0155] In one or more optional embodiments above, the first electrode piece 31 includes a first main body area 312 provided with a first active material layer and a first empty foil area 311 not provided with the first active material layer. Along the width direction of the first electrode piece 31, the first empty foil area 311 is connected to the first main body area 312. Along the length direction of the first electrode piece 31, a first gap 315 is formed between the first empty foil area 311 and the first main body area 312, so that the first empty foil area 311 can move relative to the first main body area 312 along the connection with the first main body area 312; the shape of the first empty foil area 311 is a quadrilateral.

[0156] The extension direction of the first slit 315 is parallel to the width direction of the first electrode sheet 31. During the manufacturing process of the electrode assembly 30, after the multiple first electrode sheets 31 are stacked, the multiple first empty foil areas 311 are simultaneously contracted along the width direction of the first electrode sheet 31 when they are contracted along the first direction X. Because the first electrode sheet 31 is manufactured using the electrode sheet manufacturing method of the above embodiment, even if the multiple first empty foil areas 311 are contracted along the width direction of the first electrode sheet 31, the multiple first empty foil areas 311 can have a large overlapping area. After the contraction is completed, the portion exceeding the edge of the first electrode sheet 31 is trimmed, and the ratio of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the multiple first empty foil areas 311 can reach 90% or more.

[0157] In the above scheme, the first empty foil area 311 is in the shape of a quadrilateral. Along the length direction of the first electrode 31, a first gap 315 is formed between the first empty foil area 311 and the first main area 312 to facilitate the folding of the multiple first empty foil areas 311, so that the multiple first empty foil areas 311 can have a larger overlapping area after folding, thereby making the area of ​​the first overlapping region 313 larger than the maximum projected area of ​​the multiple first empty foil areas 311.

[0158] In one or more optional embodiments above, in the width direction of the first electrode piece 31 , the edge of the first empty foil area 311 is flush with the edge of the first main body area 312 ; in the length direction of the first electrode piece 31 , the edge of the first empty foil area 311 is flush with the edge of the first main body area 312 .

[0159] It can be understood that after the multiple first empty foil areas 311 are folded together, the portions of the multiple first empty foil areas 311 that extend beyond the edges of the first main area 312 in the width direction of the first electrode piece 31 and the length direction of the first electrode piece 31 are cut off, so that the edges of the first empty foil areas 311 are flush with the edges of the first main area 312 in the width direction of the first electrode piece 31 and the length direction of the first electrode piece 31. Since there is a first gap 315 between the first empty foil areas 311 and the first main area 312 along the length direction of the first electrode piece 31, after folding, the edges of the first empty foil areas 311 along the length direction of the first electrode piece 31 will not shrink, and the portions of the first empty foil areas 311 that extend beyond the first main area 312 along the length direction of the first electrode piece 31 are cut off, so that the first empty foil areas 311 can be flush with the first main area 312 in both the length direction and the width direction of the first electrode piece 31. It should be noted that the flushing here means approximately flushing, and there can be a processing error within 0.5 mm.

[0160] In the above scheme, in the width direction of the first electrode piece 31 and the length direction of the first electrode piece 31, the edges of the first empty foil area 311 are flush with the edges of the first main body area 312. On the one hand, it is convenient for multiple first empty foil areas 311 to have a larger overlapping area. On the other hand, it reduces the risk of interference between the first empty foil area 311 and other components, for example, reducing the risk of short circuit between the first electrode piece 31 and the second electrode piece 32, and for example, reducing the risk of interference between the first electrode piece 31 and the packaging package.

[0161] In one or more optional embodiments above, the expanded areas of the plurality of first empty foil areas 311 gradually increase along a direction opposite to the contraction direction of the plurality of first empty foil areas 311 .

[0162] The first direction X may be parallel to the gathering direction of the plurality of first empty foil areas 311 .

[0163] Before the multiple first empty foil areas 311 are collapsed, each first empty foil area 311 may have a relatively large area. After the multiple first empty foil areas 311 are collapsed along the first direction X, at least some of the first empty foil areas 311 are bent to provide a larger overlapping area for the multiple first empty foil areas 311. Furthermore, the collapsed multiple first empty foil areas 311 are trimmed, with portions of the first empty foil areas 311 that extend beyond the edges of the first main area 312 being trimmed to reduce the risk of interference between the first empty foil areas 311 and other components. Therefore, when the multiple first empty foil areas 311 are expanded in a direction opposite to the collapse direction, the expanded area of ​​the multiple first empty foil areas 311 gradually increases.

[0164] For example, when the ratio S2 / S1 of the area of ​​the first overlapping region 313 to the maximum projected area of ​​the multiple first empty foil areas 311 is 100%, the overlapping area of ​​the multiple first empty foil areas 311 is the largest. When the multiple first empty foil areas 311 are gradually unfolded in the opposite direction of the folding direction of the multiple first empty foil areas 311, the unfolded area of ​​the multiple first empty foil areas 311 gradually increases.

[0165] In the above solution, when unfolding in the direction opposite to the folding direction of the first empty foil areas 311, the unfolding areas of the multiple first empty foil areas 311 gradually increase, so that the multiple first empty foil areas 311 can have a larger overlapping area while occupying a smaller assembly space after folding.

[0166] Please refer to Figures 7 to 9. In one or more optional embodiments above, each first electrode 31 further has a second notch 314, and each second electrode 32 has a second empty foil area 322. The second empty foil area 322 is located at the second corner 32a of the second electrode 32. When viewed along the first direction X, the second empty foil area 322 at least partially overlaps with the second notch 314.

[0167] The second notch 314 can be located at the third corner 31b of the first pole piece 31, and the third corner 31b and the first corner 31a can be two adjacent corners of the first pole piece 31, or the third corner 31b and the first corner 31a can be two non-adjacent corners of the first pole piece 31, or the third corner 31b and the first corner 31a can be two symmetrical corners of the first pole piece 31.

[0168] The first notch 321 can be located at the fourth corner 32b of the second pole piece 32. The fourth corner 32b and the second corner 32a can be two adjacent corners of the second pole piece 32, or the fourth corner 32b and the second corner 32a can be two non-adjacent corners of the second pole piece 32, or the fourth corner 32b and the second corner 32a can be two symmetrical corners of the second pole piece 32.

[0169] The second electrode sheet 32 ​​further has a second main body region 323 . The second main body region 323 is provided with a second active material layer, and the second empty foil region 322 is not provided with a second active material layer.

[0170] The second empty foil area 322 is located at the second corner 32a of the second electrode 32. The second empty foil area 322 at least partially overlaps with the second notch 314, so that the second electrode 32 can be provided with more second active material layers and the first electrode 31 can be provided with more first active material layers.

[0171] In some embodiments, when viewed along the first direction X, the second empty foil area 322 partially overlaps with the second notch 314 , or the second empty foil area 322 completely overlaps with the second notch 314 .

[0172] In some embodiments, the second notch 314 is formed at an edge of the first pole piece 31 .

[0173] Observed along the first direction X, the second empty foil areas 322 are exposed to the second notches 314 , so that the plurality of second empty foil areas 322 can be collapsed, thereby facilitating connection between the plurality of second empty foil areas 322 and the adapter and reducing the risk of short circuit between the positive and negative electrodes.

[0174] Multiple second empty foil areas 322 are stacked and folded in the first direction X. Along the first direction X, the maximum projection area of ​​the multiple second empty foil areas 322 is S3. The projections of the uppermost second empty foil area 322 and the lowermost second empty foil area 322 in the multiple second empty foil areas 322 are the second overlapping areas 324. The area of ​​the second overlapping areas 324 is S4, satisfying 55%≤S4 / S3≤100%.

[0175] The second overlapping region 324 refers to an overlapping region of projections of the plurality of second empty foil regions 322 along the first direction X after the plurality of second empty foil regions 322 are folded together.

[0176] S4 / S3 refers to the ratio of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the plurality of second empty foil areas 322 .

[0177] When S4 / S3≥55%, the plurality of second empty foil regions 322 have a larger overlapping area under the premise that the plurality of second empty foil regions 322 occupy a smaller assembly space.

[0178] Optionally, S4 / S3 may be, but is not limited to, 55%, 58%, 58.37%, 65.83%, 70%, 73.73%, 80%, 90%, 99.85%, 100%, etc.

[0179] In the above embodiment, the second hollow foil region 322 is located at the second corner 32a of the second electrode 32. The first electrode 31 has a second notch 314. The second hollow foil region 322 at least partially overlaps the second notch 314, allowing the first electrode 31 and the second electrode 32 to each be provided with a relatively large amount of active material. The ratio of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the plurality of second hollow foil regions 322 satisfies the aforementioned relationship (S4 / S3 ≥ 55%). When the plurality of second hollow foil regions 322 occupy a relatively small space, the relatively large ratio of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the plurality of second hollow foil regions 322 ensures that the overlapping area of ​​the plurality of second hollow foil regions 322 is sufficient to meet the flow rate requirements, and can even provide a relatively large flow rate area. Therefore, when the plurality of second hollow foil regions 322 meet the flow rate requirements, the plurality of second electrode 32s can be provided with a relatively large amount of active material, thereby improving energy density.

[0180] Depending on the shape of the second empty foil regions 322 , the ratio of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the plurality of second empty foil regions 322 may be different.

[0181] For example, referring to Figures 10 and 12, when the shape of the second empty foil area 322 is rectangular, in order to facilitate the folding of the multiple second empty foil areas 322, the second electrode 32 is provided with a second slit 325. The second slit 325 is arranged along a partial boundary line between the second empty foil area 322 and the second main area 323, so that the second empty foil area 322 can move relative to the second main area 323, so that the area of ​​the second overlapping area 324 and the maximum projected area of ​​the multiple second empty foil areas 322 can be 100%.

[0182] In one or more of the above optional embodiments, 58%≤S4 / S3≤80%.

[0183] In the above solution, compared with 55%≤S4 / S3≤100%, when 58%≤S4 / S3≤80%, the plurality of second empty foil areas 322 occupy a smaller space, and the plurality of second empty foil areas 322 further have a larger overlapping area, so that the battery cell 100 has a higher energy density.

[0184] In one or more optional embodiments above, the second empty foil area 322 is in a triangular shape, and S3 and S4 satisfy: 70%≤S4 / S3≤80%.

[0185] In the above embodiment, second hollow foil region 322 is located at second corner 32a and is triangular in shape, facilitating manufacturing. Compared to 58% ≤ S4 / S3 ≤ 80%, when 70% ≤ S4 / S3 ≤ 80%, multiple second hollow foil regions 322 occupy less space and have a larger overlapping area, resulting in a higher energy density for battery cell 100.

[0186] In one or more of the above optional embodiments, in the width direction of the second pole piece 32 , the edge of the second hollow foil region 322 is flush with the edge of the second main body region 323 .

[0187] It can be understood that after the multiple second empty foil areas 322 are folded together, the portions of the multiple second empty foil areas 322 that extend beyond the edge of the second main area 323 in the width direction of the second electrode 32 are cut off, so that in the width direction of the second electrode 32, the edge of the second empty foil area 322 is flush with the edge of the second main area 323. Because the second empty foil area 322 is triangular in shape, it shrinks due to the thickness difference when the second electrode 32 is folded together in both the length and width directions. However, since the second electrode 32 of the present application has a margin only in the width direction, the portion that extends beyond the edge of the second main area 323 is cut off after folding, thereby ensuring that the edge of the second empty foil area 322 in the width direction is flush with the edge of the second main area 323. It should be noted that the flush here means approximately flush, and there can be a processing error within 0.5 mm.

[0188] In the above scheme, in the width direction of the second electrode 32, the edge of the second empty foil area 322 is flush with the edge of the second main area 323. On the one hand, it is convenient for multiple second empty foil areas 322 to have a larger overlapping area; on the other hand, it reduces the risk of interference between the second empty foil area 322 and other components, for example, reducing the risk of short circuit between the first electrode 31 and the second electrode 32, and for another example, reducing the risk of interference between the second electrode 32 and the packaging of the package.

[0189] In one or more of the above optional embodiments, 90%≤S4 / S3≤100%.

[0190] In the above scheme, compared with 55%≤S4 / S3≤100%, when 90%≤S4 / S3≤100%, when the multiple second empty foil areas 322 occupy a smaller space, since the ratio of the area of ​​the second overlapping area 324 to the maximum projected area of ​​the multiple second empty foil areas 322 is larger, the overlapping area of ​​the multiple second empty foil areas 322 is sufficient to meet the overcurrent requirement, and the space occupied by the multiple second empty foil areas 322 can be further reduced, so that the second electrode 32 can have a larger area of ​​active material, so that the battery cell 100 has a higher energy density.

[0191] In one or more optional embodiments above, the second electrode piece 32 includes a second main body area 323 provided with a second active material layer and a second empty foil area 322 not provided with a second active material layer. Along the width direction of the second electrode piece 32, the second empty foil area 322 is connected to the second main body area 323. Along the length direction of the second electrode piece 32, a second gap 325 is formed between the second empty foil area 322 and the second main body area 323, so that the second empty foil area 322 can move relative to the second main body area 323 along the connection with the second main body area 323; the shape of the second empty foil area 322 is a quadrilateral.

[0192] The extension direction of the second slit 325 is parallel to the width direction of the second electrode sheet 32. During the manufacturing process of the electrode assembly 30, after the multiple second electrode sheets 32 are stacked, the multiple second hollow foil areas 322 are simultaneously collapsed along the width direction of the second electrode sheet 32 ​​when they are collapsed along the first direction X. Because the second electrode sheet 32 ​​is manufactured using the electrode sheet manufacturing method of the above embodiment, even if the multiple second hollow foil areas 322 are collapsed along the width direction of the second electrode sheet 32, the multiple second hollow foil areas 322 can have a large overlapping area. After the collapse is completed, the portion exceeding the edge of the second electrode sheet 32 ​​is trimmed, and the ratio of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the multiple second hollow foil areas 322 can reach 90% or more.

[0193] In the above scheme, the second empty foil area 322 is in the shape of a quadrilateral. Along the length direction of the second electrode 32, a second gap 325 is formed between the second empty foil area 322 and the second main area 323 to facilitate the folding of the plurality of second empty foil areas 322, so that the plurality of second empty foil areas 322 can have a larger overlapping area after folding, thereby making the area of ​​the second overlapping region 324 larger than the maximum projected area of ​​the plurality of second empty foil areas 322.

[0194] In one or more optional embodiments above, in the width direction of the second pole piece 32 , the edge of the second empty foil area 322 is flush with the edge of the second main body area 323 ; in the length direction of the second pole piece 32 , the edge of the second empty foil area 322 is flush with the edge of the second main body area 323 .

[0195] It can be understood that after the multiple second empty foil areas 322 are folded together, the portions of the second empty foil areas 322 that extend beyond the edges of the second main area 323 in the width direction and the length direction of the second electrode piece 32 are removed, so that the edges of the second empty foil areas 322 are flush with the edges of the second main area 323 in the width direction and the length direction of the second electrode piece 32. Since there is a second gap 325 between the second empty foil areas 322 and the second main area 323 along the length direction of the second electrode piece 32, after folding, the edges of the second empty foil areas 322 along the length direction of the second electrode piece 32 do not shrink. Instead, the portions of the second empty foil areas 322 that extend beyond the second main area 323 along the length direction of the second electrode piece 32 are removed, so that the second empty foil areas 322 are flush with the second main area 323 in both the length and width directions of the second electrode piece 32. It should be noted that the flushing here means approximately flushing, and a processing error within 0.5 mm is allowed.

[0196] In the above scheme, in the width direction of the second electrode piece 32 and the length direction of the second electrode piece 32, the edges of the second empty foil area 322 are flush with the edges of the second main body area 323. On the one hand, it is convenient for multiple second empty foil areas 322 to have a larger overlapping area. On the other hand, it reduces the risk of interference between the second empty foil area 322 and other components, for example, reducing the risk of short circuit between the first electrode piece 31 and the second electrode piece 32, and for example, reducing the risk of interference between the second electrode piece 32 and the packaging of the package.

[0197] In one or more optional embodiments above, the expanded areas of the plurality of second empty foil areas 322 gradually increase along a direction opposite to the contraction direction of the plurality of second empty foil areas 322 .

[0198] The first direction X may be parallel to the gathering direction of the plurality of second empty foil areas 322 .

[0199] Before the plurality of second empty foil areas 322 are collapsed, each second empty foil area 322 may have a relatively large area. After the plurality of second empty foil areas 322 are collapsed along the first direction X, at least some of the second empty foil areas 322 are bent to provide a relatively large overlapping area. Furthermore, the collapsed plurality of second empty foil areas 322 are trimmed, with portions of the second empty foil areas 322 that extend beyond the edges of the second main area 323 being trimmed to reduce the risk of interference between the second empty foil areas 322 and other components. Therefore, when the plurality of second empty foil areas 322 are expanded in a direction opposite to the collapse direction, the expanded area of ​​the plurality of second empty foil areas 322 gradually increases.

[0200] For example, when the ratio S4 / S3 of the area of ​​the second overlapping region 324 to the maximum projected area of ​​the multiple second empty foil areas 322 is 100%, the overlapping area of ​​the multiple second empty foil areas 322 is the largest, and when the multiple second empty foil areas 322 are gradually unfolded in the opposite direction of the folding direction of the multiple second empty foil areas 322, the unfolded area of ​​the multiple second empty foil areas 322 gradually increases.

[0201] In the above solution, when unfolding in the direction opposite to the folding direction of the second empty foil areas 322, the unfolding areas of the plurality of second empty foil areas 322 gradually increase, so that the plurality of second empty foil areas 322 can have a larger overlapping area while occupying a smaller assembly space after folding.

[0202] Please refer to Figure 13. In one or more optional embodiments above, the battery cell 100 further includes a packaging bag 40, a first adapter 50 and a second adapter 60. The electrode assembly 30 is accommodated in the packaging bag 40. The first adapter 50 is electrically connected to the multiple first empty foil areas 311 and extends out of the packaging bag 40. The second adapter 60 is electrically connected to the multiple second empty foil areas 322 and extends out of the packaging bag 40.

[0203] The battery cell 100 may be a soft-pack battery cell.

[0204] The packaging bag 40 may be made of aluminum, aluminum-plastic film, or other metal films.

[0205] One end of the first adapter 50 is welded to the plurality of first empty foil areas 311 , and the other end of the first adapter 50 extends out of the packaging bag 40 .

[0206] One end of the second adapter 60 is welded to the plurality of second empty foil areas 322 , and the other end of the second adapter 60 extends out of the packaging bag 40 .

[0207] In the above solution, the battery cell 100 can be a soft-pack battery cell 100 with a higher energy density; the first adapter 50 extends out of the packaging bag 40, and the second adapter 60 extends out of the packaging bag 40 to facilitate the extraction of electrical energy from the electrode assembly 30.

[0208] Please refer to Figure 14. In one or more optional embodiments above, the electrode assembly 30 further includes a diaphragm 33, which is arranged between the adjacent first electrode piece 31 and the second electrode piece 32. The diaphragm 33 has a third notch 331 and a fourth notch 332. Along the first direction X, the third notch 331 at least partially overlaps with the first empty foil area 311 (please refer to Figure 6), and the fourth notch 332 at least partially overlaps with the second empty foil area 322 (please refer to Figure 6).

[0209] In some embodiments, the third notch 331 may be located at the fifth corner 33 a of the diaphragm 33 , and the fourth notch 332 may be located at the sixth corner 33 b of the diaphragm 33 .

[0210] In some embodiments, the third notch 331 and the fourth notch 332 may be located at two adjacent corners of the diaphragm 33 .

[0211] In some embodiments, the separator 33 is further located at an end of the electrode assembly 30 in the first direction X to be insulated from the packaging bag 40 .

[0212] When viewed along the first direction X, the first empty foil area 311 is exposed at the third notch 331 , and the second empty foil area 322 is exposed at the fourth notch 332 .

[0213] When viewed along the first direction X, the projection of the first empty foil area 311 partially overlaps with the third notch 331 , or the projection of the first empty foil area 311 completely overlaps with the third notch 331 .

[0214] When viewed along the first direction X, the projection of the second empty foil area 322 partially overlaps with the fourth notch 332 , or the projection of the second empty foil area 322 completely overlaps with the fourth notch 332 .

[0215] In the above solution, the provision of the diaphragm 33 can insulate and isolate the first electrode piece 31 from the second electrode piece 32, thereby reducing the risk of short circuits caused by contact between the positive and negative electrodes. The provision of the third notch 331 facilitates the folding of the plurality of first hollow foil areas 311; the provision of the fourth notch 332 facilitates the folding of the plurality of second hollow foil areas 322.

[0216] In some embodiments, the maximum projection of the plurality of first empty foil areas 311 is a triangle, a rectangle, or an N-gon, where N≥5.

[0217] The following describes a method for manufacturing a battery cell using the first pole piece 31 and the second pole piece 32 produced by the pole pieces provided in the above embodiment.

[0218] The present invention also provides a method for manufacturing a battery cell, which includes:

[0219] A first electrode piece 31 and a second electrode piece 32 are provided. The first electrode piece 31 and the second electrode piece 32 are the electrode pieces provided in any embodiment. The first electrode piece 31 has a first hollow foil area 311, a first main body area 312, and a second notch 314. The second electrode piece 32 has a first notch 321, a second hollow foil area 322, and a second main body area 323.

[0220] Along the first direction X, the plurality of first electrode sheets 31 and the plurality of second electrode sheets 32 are alternately stacked so that the first empty foil area 311 is exposed to the first notch 321 and the second empty foil area 322 is exposed to the second notch 314; along the first direction X, the plurality of first empty foil areas 311 and the plurality of second empty foil areas 322 are folded together;

[0221] In the length direction and / or width direction of the first electrode piece 31 , the portion of the first empty foil area 311 that exceeds the edge of the first main area 312 is cut off, and the portion of the second empty foil area 322 that exceeds the edge of the second main area 323 is cut off.

[0222] The length direction of the second pole piece 32 is parallel to the length direction of the first pole piece 31 , and the width direction of the second pole piece 32 is parallel to the width direction of the first pole piece 31 .

[0223] During the battery cell manufacturing process, taking the first electrode sheet 31 as an example, before the multiple first electrode sheets 31 and the multiple second electrode sheets 32 are stacked, because the first hollow foil area 311 extends beyond the edge of the first main body area 312, the first hollow foil area 311 can have a larger area while occupying a smaller assembly space. After the multiple first electrode sheets 31 and the multiple second electrode sheets 32 are stacked, the multiple first hollow foil areas 311 are retracted, and some of the first hollow foil areas 311 move toward the first main body area 312. Portions of the first hollow foil areas 311 that extend beyond the edge of the first main body area 312 are removed along the length direction and / or the width direction of the first electrode sheet 31 to reduce the excessive assembly space occupied by the first hollow foil areas 311. However, the multiple first hollow foil areas 311 have a large overlapping area, and the first adapter 50 is connected to the overlapping area of ​​the multiple first hollow foil areas 311, ensuring a secure connection between the first adapter 50 and the multiple first hollow foil areas 311 and providing good current flow capacity.

[0224] Similarly, the plurality of second empty foil areas 322 have a large overlapping area, and the second adapter 60 is connected to the overlapping areas of the plurality of second empty foil areas 322, so that the second adapter 60 is firmly connected to the plurality of second empty foil areas 322 and has a good flow capacity.

[0225] After completing the connection between the first adapter 50 and the multiple first empty foil areas 311 and the connection between the second adapter 60 and the multiple second empty foil areas 322, the assembled electrode assembly 30 is placed in the packaging bag 40. After packaging, the electrolyte is injected into the packaging bag 40 to complete the preparation of the battery cell 100.

[0226] The battery cell 100 according to the embodiment of the present application is described below with reference to specific embodiments.

[0227] The length of the battery cell 100 is 80 mm, the width is 71 mm, the first electrode piece 31 is a negative electrode piece, the length of the first electrode piece 31 is 77.5 mm, and the width of the first electrode piece 31 is 69 mm. For other parameters, please refer to the following table (Table 1).

[0228] Table 1

[0229] In the above table, after the first electrode piece and the second electrode piece are stacked and the portion of the first hollow foil area that exceeds the outer edge of the first main body area is cut, in Examples 1-3, the maximum projected shape of the multiple first hollow foil areas is a triangle; in Examples 4-6, the maximum projected shape of the multiple first hollow foil areas is a quadrilateral. In Comparative Examples 1-3, before the first electrode piece is stacked with the second electrode piece, the first electrode piece is rectangular, the first hollow foil area of ​​the first electrode piece is an isosceles triangle, and is located at the first corner of the first electrode piece. The two waists of the first hollow foil area are respectively flush with the two outer edges of the first main body area (ignoring processing errors). After the first electrode piece and the second electrode piece are stacked, the maximum projected shape of the multiple first hollow foil areas is a triangle.

[0230] After the first electrode sheet and the second electrode sheet are stacked and the portion of the first empty foil area that exceeds the outer edge of the first main area is cut off, it can be seen from Table 1 that the maximum projected areas of the multiple first empty foil areas in Examples 1-6 are the same as the maximum projected areas of the multiple first empty foil areas in Comparative Examples 1-3.

[0231] It can be seen from Table 1 that, under the same maximum projection area of ​​multiple first empty foil areas, compared with comparative examples 1-3, under the condition of the same first empty foil area occupying space and the same first main area area (first active material area), the maximum overlapping area of ​​multiple first empty foil areas in Examples 1-3 is larger, the multiple first empty foil areas are firmly connected to the adapter, and the multiple first empty foil areas have a larger flow area. Conversely, when the overlapping areas of multiple first empty foil areas are equal, the battery cells of Examples 1-3 can have a larger first active material area, and Examples 1-3 can have a higher energy density.

[0232] Compared with Comparative Examples 1-3, Example 4-6 has a different shape of the first empty foil area. In Example 4-6, when the area of ​​the first main area (first active material area) is the same, the area of ​​the first overlapping area is larger than the maximum projected area of ​​the multiple first empty foil areas. When the first empty foil areas occupy the same space, the multiple first empty foil areas have a larger overlapping area, the multiple first empty foil areas are firmly connected to the adapter, and the multiple first empty foil areas have a larger flow area; conversely, when the overlapping areas of the multiple first empty foil areas are equal, the battery cell of Example 4-6 can have a larger first active material area, and Example 4-6 can have a higher energy density.

[0233] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A battery cell, characterized in that: include: The electrode assembly has a laminated structure, comprising a plurality of first electrode sheets and a plurality of second electrode sheets stacked along a first direction, wherein the first electrode sheets and the second electrode sheets have opposite polarities, each of the first electrode sheets has a first hollow foil area, the first hollow foil area being located at a first corner of the first electrode sheet, and each of the second electrode sheets has a first notch, wherein the first hollow foil area at least partially overlaps with the first notch when viewed along the first direction; Among them, multiple first empty foil areas are stacked and gathered in the first direction, and along the first direction, the maximum projection area of ​​the multiple first empty foil areas is S1, the overlapping part of the largest projection area area among the multiple first empty foil areas and the smallest projection area area among the multiple first empty foil areas is the first overlapping area, and the area of ​​the first overlapping area is S2, satisfying 55%≤S2 / S1≤100%.

2. The battery cell according to claim 1, characterized in that 58%≤S2 / S1≤80%.

3. The battery cell according to claim 2, characterized in that The shape of the first empty foil area is a triangle, and S1 and S2 satisfy: 70%≤S2 / S1≤80%.

4. The battery cell according to claim 3, characterized in that The first electrode sheet further comprises a first main body region, wherein the first main body region is provided with a first active material layer, and the first hollow foil region is not provided with the first active material layer; In the width direction of the first pole piece, edges of the plurality of first empty foil regions are flush with an edge of the first main body region.

5. The battery cell according to claim 1, characterized in that 90%≤S2 / S1≤100%.

6. The battery cell according to claim 5, characterized in that The first electrode piece includes a first main body region provided with a first active material layer and a first hollow foil region not provided with the first active material layer. The first hollow foil region is connected to the first main body region along the width direction of the first electrode piece. A first gap is formed between the first hollow foil region and the first main body region along the length direction of the first electrode piece, so that the first hollow foil region can move relative to the first main body region along the connection with the first main body region. The shape of the first empty foil area is a quadrilateral.

7. The battery cell according to claim 6, characterized in that In the width direction of the first pole piece, the edge of the first hollow foil area is flush with the edge of the first main body area; In the length direction of the first pole piece, edges of the plurality of first empty foil areas are flush with an edge of the first main body area.

8. The battery cell according to claim 1, characterized in that Along the direction opposite to the shrinking direction of the plurality of first empty foil regions, the expanded areas of the plurality of first empty foil regions gradually increase.

9. The battery cell according to claim 1, characterized in that: Each of the first pole pieces further has a second notch, and each of the second pole pieces has a second empty foil area, the second empty foil area is located at a second corner of the second pole piece, and when viewed along the first direction, the second empty foil area at least partially overlaps with the second notch; Multiple second empty foil areas are stacked and gathered in the first direction. Along the first direction, the projection area of ​​the multiple second empty foil areas is S3. The projections of the multiple second empty foil areas have a second overlapping area. The area of ​​the second overlapping area is S4, satisfying 55%≤S4 / S3≤100%.

10. The battery cell according to claim 9, characterized in that: The battery cell also includes a packaging bag, a first adapter and a second adapter. The electrode assembly is accommodated in the packaging bag. The first adapter is electrically connected to the multiple first empty foil areas and extends out of the packaging bag. The second adapter is electrically connected to the multiple second empty foil areas and extends out of the packaging bag.

11. The battery cell according to claim 9, characterized in that The electrode assembly also includes a diaphragm, which is arranged between the adjacent first electrode sheet and the second electrode sheet. The diaphragm has a third notch and a fourth notch. Along the first direction, the third notch at least partially overlaps with the first empty foil area, and the fourth notch at least partially overlaps with the second empty foil area.

12. A pole piece, characterized in that: The device comprises a current collector and an active material layer, wherein the current collector comprises a main body area provided with the active material layer and a hollow foil area not provided with the active material layer; The main body area includes a first edge, a second edge and a third edge, the first edge and the second edge are arranged opposite to each other along a second direction, the second direction is perpendicular to the thickness direction of the electrode, the third edge is located between the first edge and the second edge, the empty foil area is located at the corner formed by the second edge and the third edge, and a notch is provided at the corner formed by the first edge and the third edge; The empty foil area includes a first portion and a second portion that are continuously arranged. Along the second direction, the first portion protrudes from the second edge, the second portion does not protrude from the second edge, and the first portion is complementary to the notch.

13. The pole piece according to claim 12, characterized in that: The empty foil area includes a first outer edge and a second outer edge, the first outer edge is flush with the third edge, and the second outer edge matches the contour of the notch.

14. The pole piece according to claim 13, characterized in that: The second outer edge is a straight line segment, a curved line segment or a broken line segment.

15. The pole piece according to claim 12, characterized in that: The first portion and the second portion are symmetrically arranged along an extension line of the second edge.

16. A method for manufacturing a pole piece, characterized in that: The pole piece manufacturing method comprises: Providing a pole piece strip, the pole piece strip comprising a current collector and an active material layer, the current collector having a main body region provided with the active material layer and a plurality of hollow foil regions not provided with the active material layer, the current collector having a first side edge and a second side edge opposite to each other along a width direction of the pole piece strip, the plurality of hollow foil regions being spaced apart along the first side edge; The electrode material strip is cut along a preset trajectory to form a electrode having complementary hollow foil areas and gaps; wherein the preset trajectory includes a first segment and a second segment arranged continuously, one end of the first segment is located at the first side edge, one end of the second segment is located at the second side edge, and the first segment coincides with the boundary line between the hollow foil area and the main area.

17. The pole piece manufacturing method according to claim 16, characterized in that: Providing the pole piece strip includes: coating the active material on the surface of the current collector; A portion of the active material on the current collector is cleaned to form a plurality of empty foil areas that are spaced apart.

18. The pole piece manufacturing method according to claim 16, characterized in that: Providing the pole piece strip includes: Attaching a plurality of shielding members spaced apart on the surface of the current collector; coating an active material on the surface of the current collector; The shielding member is separated from the current collector to form a plurality of empty foil areas that are spaced apart.

19. A method for manufacturing a battery cell, characterized in that: include: Providing a first electrode piece and a second electrode piece, wherein the first electrode piece and the second electrode piece are the electrode pieces according to any one of claims 12 to 15, wherein the first electrode piece has a first hollow foil area, a first main body area, and a second notch, and the second electrode piece has a first notch, a second hollow foil area, and a second main body area; Along a first direction, a plurality of the first electrode sheets and a plurality of the second electrode sheets are alternately stacked so that the first empty foil area is exposed to the first notch, and the second empty foil area is exposed to the second notch; Along the first direction, folding a plurality of the first empty foil areas and folding a plurality of the second empty foil areas; In the length direction and / or the width direction of the first electrode piece, a portion of the first hollow foil area exceeding the edge of the first main body area is cut off, and a portion of the second hollow foil area exceeding the edge of the second main body area is cut off.

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