Electrode assembly and battery cell

Abstract

Disclosed in the present application are an electrode assembly and a battery cell. The electrode assembly comprises a first wound electrode sheet unit and a second wound electrode sheet unit, the polarities of the first electrode sheet unit and the second electrode sheet unit being opposite. At least one of the first electrode sheet unit and the second electrode sheet unit comprises an electrode sheet, an electrode tab, and a separator. The separator comprises a first separator part and a second separator part which are respectively arranged on two opposite sides of the electrode sheet along the thickness of the electrode sheet, the first separator part comprising a first extension which extends out of the edge of the electrode sheet along the width of the electrode sheet, and the second separator part comprising a second extension which extends out of the edge of the electrode sheet along the width of the electrode sheet. The electrode tab is arranged on the electrode sheet, and the electrode tab extends out of the separator through the space between the first extension and the second extension. A portion of the first extension and a portion of the second extension are connected to form sealing regions; at least two sealing regions are formed, and said sealing regions provide clearance for the electrode tab. The electrode assembly provided in the embodiments of the present application can effectively improve the drop resistance of a battery cell.

Description

Electrode assemblies and battery cells

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 30, 2023, with application number 202310802063.8 and invention name “Electrode Assembly and Battery Cell”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of electrochemical technology, and in particular to an electrode assembly and a battery cell. Background Art

[0003] As the use scenarios of 3C (Computer, Communication, Consumer Electronic) electronic products become more diversified and complex, people have increasingly stringent requirements for the safety of electronic products, and are paying more and more attention to battery safety. After multiple drops, the battery will experience a drop in voltage or even catch fire and explode. Studies have found that the main reason for the voltage drop or fire and explosion of dropped batteries is the shrinkage of the isolation membrane inside the battery, which causes an internal short circuit. When the battery is dropped multiple times, the free electrolyte will repeatedly impact the isolation membrane. When the impact force of the electrolyte is greater than the binding force of the isolation membrane, the isolation membrane inside the battery shrinks, and the positive and negative electrodes will come into direct contact, causing an internal short circuit, resulting in a significant drop in voltage and failure or direct smoke and fire. Therefore, the shrinkage of the isolation membrane poses a serious threat to battery safety and needs to be urgently addressed.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide an electrode assembly and a battery cell, which can solve the problem of poor drop resistance of the battery cell.

[0006] In a first aspect, the present application provides an electrode assembly, comprising a first pole piece unit and a second pole piece unit that are wound together; the first pole piece unit and the second pole piece unit have opposite polarities;

[0007] At least one of the first pole piece unit and the second pole piece unit includes a pole piece, a pole ear and an isolation membrane, the isolation membrane includes a first diaphragm and a second diaphragm arranged on opposite sides of the pole piece in the thickness direction of the pole piece, the first diaphragm includes a first extension portion extending from the edge of the pole piece along the width direction of the pole piece, the second diaphragm includes a second extension portion extending from the edge of the pole piece along the width direction of the pole piece, the pole ear is provided on the pole piece, and the pole ear extends out of the isolation membrane between the first extension portion and the second extension portion, the first extension portion and the second extension portion are connected to form a sealing area, the number of the sealing areas is at least two, and the sealing area avoids the pole ear.

[0008] In the electrode assembly according to the embodiments of the present application, the portions of the first separator and the second separator that exceed the width of the electrode tab are connected and cured with each other in a certain manner to form a sealing area, preventing the contact between the positive electrode tab and the negative electrode tab from causing the failure of the voltage drop of the battery cell and short circuit. The adjacent two sealing areas are arranged at intervals, and the electrolyte can enter between the first separator and the second separator from the area where the first separator and the second separator are not connected, and the electrode assembly still has a good electrolyte infiltration effect. The sealing area avoids the electrode ear, which can prevent overvoltage on the electrode ear and the electrode tab corresponding to and connected to the electrode ear, effectively improving the stability of the performance of the prepared battery cell.

[0009] In some exemplary embodiments, at least a part of the sealing area is arranged at intervals along the length direction of the electrode tab; in the length direction of the electrode tab, the length of the electrode tab is L, the length of the sealing area is l0, and the width between two adjacent sealing areas is a1, where,

[0010] 1 < L / l0 ≤ 200; and / or,

[0011] 200 ≤ L / a1 ≤ 4000; and / or,

[0012] 1 ≤ l0 / a1 ≤ 4000.

[0013] Based on the above embodiments, by controlling the ratios of L, l0, and a1 within a suitable range, it is convenient to distribute the length and spacing of the sealing area in the length direction of the electrode tab, so that the sealing area is firmly encapsulated in the length direction of the electrode tab and has a good electrolyte infiltration effect.

[0014] In some exemplary embodiments, a part of the sealing area is arranged at intervals along the length direction of the electrode tab, and another part of the sealing area is arranged at intervals along the width direction of the electrode tab; in the width direction of the electrode tab, the width of the electrode tab is W, the width of the sealing area is w0, and the width between two adjacent sealing areas is a2, where,

[0015] 1 ≤ W / w0 ≤ 20; and / or,

[0016] W / a2 ≥ 20; and / or,

[0017] w0 / a2 ≥ 1.

[0018] Based on the above embodiments, by controlling the ratios of W, w0, and a2 within the above range, it is convenient to distribute the length and spacing of the sealing area in the width direction of the electrode tab, so that the sealing area is firmly encapsulated in the width direction of the electrode tab and has a good electrolyte infiltration effect.

[0019] In some exemplary embodiments, in the width direction of the pole piece, the first extension portion includes a first part located on one side of the pole piece, and a partial area of ​​the first part is connected to the second extension portion to form at least two sealing areas.

[0020] In some exemplary embodiments, in the width direction of the pole piece, one end of the first diaphragm facing away from the first portion is integrally formed with the second diaphragm.

[0021] Based on the above embodiment, the cutting process of the isolation film is reduced, which helps to improve assembly efficiency.

[0022] In some exemplary embodiments, in the width direction of the pole piece, the first extension portion includes a second portion away from the first portion, and a partial area of ​​the second portion is connected to the second extension portion to form at least one of the sealing areas.

[0023] Based on the above embodiments, on the one hand, it is convenient to improve the firmness of the connection of multiple sealing areas and prevent the movement of the pole pieces from causing an acute short circuit between two opposite pole pieces. On the other hand, in the width direction of the pole pieces, the electrolyte can enter between the first diaphragm and the second diaphragm from the opposite ends of the isolation membrane, which helps to improve the wetting effect of the electrolyte.

[0024] In some exemplary embodiments, each of the sealing areas is a hot pressing sealing portion or a rolling sealing portion; or, an adhesive layer is provided between the first extension portion and the second extension portion, and the first extension portion and the second extension portion are connected by the adhesive layer to form the sealing area.

[0025] Based on the above embodiments, the hot pressing sealing part and the rolling sealing part can avoid the pressing of the pole ear according to the preset pressing rules, and form a sealing area by applying adhesive on the surface of at least one of the first extension part and the second extension part and then bonding them. The processing method is simple, prevents overpressure on the pole ear and the pole piece part corresponding to the pole ear, and improves the performance stability of the electrode assembly.

[0026] In some exemplary embodiments, the electrode assembly includes a straight portion and a curved portion, and the sealing area is disposed on the straight portion.

[0027] Based on the above embodiment, a sealing area is provided in the straight portion, the structure of the sealing area is stable, and the isolation membrane can better protect the electrode, thereby preventing the occurrence of unstable connection of the sealing area due to high stress in the curved portion.

[0028] In some exemplary embodiments, the sealing areas are correspondingly arranged in the thickness direction of the electrode assembly, and the first extension portion and the second extension portion of the bent portion are spaced apart.

[0029] Based on the above embodiment, the electrolyte wettability of the electrode assembly is improved. In addition, the regular arrangement of the sealing area helps to plan space for installing other structures of the battery cell, reducing the space occupied by the electrode assembly, and thus helping to improve the energy density of the battery cell.

[0030] In some exemplary embodiments, the electrode assembly includes two electrode pieces, at least two electrode tabs and a separator; wherein at least one electrode tab is provided on one of the electrode pieces, and the electrode piece is provided between the first diaphragm and the second diaphragm of the separator to form the first electrode piece unit; the remaining electrode tabs are provided on the other electrode piece to form the second electrode piece unit; the polarities of the two electrode pieces are opposite; or,

[0031] The electrode assembly includes two pole pieces, at least two pole tabs and two isolation membranes; at least one pole tab is arranged on one of the pole pieces and the pole piece is arranged between the first diaphragm and the second diaphragm of one of the isolation membranes to form the first pole piece unit; the remaining pole tab is arranged on the other pole piece and the pole piece is arranged between the first diaphragm and the second diaphragm of the other isolation membrane to form the second pole piece unit; the polarities of the two pole pieces are opposite.

[0032] Based on the above embodiments, the isolation film can provide more comprehensive protection for the electrode and more effectively prevent the short circuit between two electrode pieces with opposite polarities.

[0033] In some exemplary embodiments, the pole tab extends out of the isolation membrane along the width direction of the pole piece, and in the width direction of the pole piece, the width of one of the pole pieces is smaller than the width of the other pole piece, and at least the pole piece with the smaller width is arranged between the first membrane and the second membrane of the isolation membrane.

[0034] Based on the above embodiment, when the isolation membrane extends out of the edge of the pole piece with a smaller width, the first extension portion and the second extension portion of the isolation membrane can also separate the two adjacent parts of the pole piece with a larger width, saving the amount of isolation membrane and further saving the space occupied by the isolation membrane, which helps to improve the energy density of the battery cell using the electrode assembly of the present application.

[0035] In some exemplary embodiments, the electrode piece with a smaller width is a positive electrode piece, and the electrode piece with a larger width is a negative electrode piece.

[0036] In some exemplary embodiments, the sealing area is spaced apart from the pole piece, and a distance from an edge of the sealing area facing the pole piece to an edge of the pole piece is S, where S satisfies: 0.1 mm ≤ S ≤ 1 mm.

[0037] Based on the above embodiment, the sealing area is spaced apart from the electrode to buffer the impact of the electrolyte on the isolation membrane and prevent the sealing area from moving to abut against the edge of the electrode when the isolation membrane is impacted by the electrolyte, causing the sealing area to tear.

[0038] In some exemplary embodiments, the tab extends out of the isolation membrane along the width direction of the pole piece; in the length direction of the pole piece, one of the sealing areas is provided on one side of the tab, and the other sealing area is provided on the other side of the tab, and the distance from the edge of the sealing area to the edge of the tab is Q, and Q satisfies: 0.2mm≤Q≤2mm.

[0039] Based on the above embodiment, the sealing area is provided adjacent to the tab, which helps to improve the packaging stability of the sealing area at the tab. In addition, the two sealing areas are provided on opposite sides of the tab, so that the isolation film can act on the tab, which helps to improve the stability of the tab installed on the pole piece.

[0040] In a second aspect, the present application provides a battery cell, comprising a packaging bag, and the electrode assembly as described above, wherein the electrode assembly is disposed in the packaging bag.

[0041] The electrode assembly and battery cell according to the embodiments of the present application have at least the following beneficial effects:

[0042] By extending the separator beyond the bonding area, multiple sealing zones are formed. This prevents contact between the positive and negative electrodes due to separator shrinkage, separator folding, or electrode movement during a drop, potentially leading to a short circuit. This improves the safety and cycling performance of the battery cells. The portions of the first and second separators that extend beyond the electrode width are interconnected and solidified to form the sealing zones. This constrains the electrode between the first and second separators, preventing contact between the positive and negative electrodes due to separator shrinkage and minimizing voltage drop failure and short circuits in the battery cells. Adjacent sealing zones are spaced apart, leaving unconnected portions between the first and second separators that extend beyond the electrode width. This allows electrolyte to flow between the unconnected portions of the first and second separators, ensuring good electrolyte wetting throughout the electrode assembly. During the machining of the sealing zones on the first and second extensions, the sealing zones are positioned away from the tabs to prevent overpressure on the tabs and the electrode sheets in the area corresponding to the tabs, effectively improving the stability of the resulting battery cell performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings.

[0044] FIG1 is a schematic diagram of the three-dimensional structure of an electrode assembly according to an embodiment of the present application;

[0045] FIG2 is a schematic diagram of a three-dimensional structure of a first pole piece unit in an embodiment of the present application when it is unfolded;

[0046] FIG3 is a cross-sectional view taken along the line BB in FIG1 ;

[0047] FIG4 is a schematic diagram of the front structure of the unfolded first pole piece unit according to an embodiment of the present application;

[0048] FIG5 is a partial enlarged view of point M in FIG4 ;

[0049] FIG6 is a schematic side view of the rear portion of a wound electrode assembly according to an embodiment of the present application;

[0050] FIG7 is a partial enlarged view of point N in FIG6 .

[0051] Reference numerals:

[0052] 10. Electrode assembly; 11. First pole piece unit; 12. Second pole piece unit; 101. Sealing area;

[0053] 100, electrode; 110, positive electrode; 120, negative electrode;

[0054] 200, isolation membrane; 210, first diaphragm; 201, first extension; 211, first portion; 212, second portion; 213, third portion; 214, fourth portion; 220, second diaphragm; 202, second extension;

[0055] 400, tab; 410, protective layer;

[0056] 310, straight part; 320, curved part;

[0057] X, length direction; Y, width direction; Z, thickness direction. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0059] The inventors have found that in the related art, it is difficult to effectively solve the shrinkage problem of the isolation membrane by adopting the glue wrapping solution and the low-liquid-retention design solution. The glue wrapping solution is to set U-shaped adhesive tape at the head and tail of the electrode in the width direction, and the U-shaped adhesive tape is adhered to the isolation membrane on one side of the electrode and then wrapped to the other side of the electrode (for example, the U-shaped adhesive tape is adhered to the isolation membrane in the OH area of ​​the electrode assembly) to adhere to the isolation membrane on the other side, and the position of the isolation membrane is fixed by the U-shaped adhesive tape. The low-liquid-retention design is to reduce the content of free electrolyte in the battery cell and reduce the impact of free electrolyte on the isolation membrane in the OH area of ​​the electrode assembly. However, in the case of multiple drops, there is still the impact of electrolyte on the isolation membrane, which causes the isolation membrane to deform or shrink.

[0060] The inventors also discovered that while providing a closed containment area for the separator and positioning the electrode within this containment area can effectively reduce separator shrinkage caused by electrolyte impact, the separator forms a fully enclosed structure, which is not conducive to electrolyte infiltration and affects the production efficiency of the battery cell. Furthermore, when manufacturing an electrode assembly, if roller pressing is used to seal the separator, the thickness at the tab is greater than at other locations due to the presence of the tab. The composite roller and auxiliary rollers will over-press the tab connection, making processing difficult and affecting the quality of the resulting electrode assembly. Based on this, embodiments of the present application provide an electrode assembly and a battery cell.

[0061] As shown in Figure 1, it is a schematic structural diagram of an electrode assembly 10 of an embodiment of the present application. The electrode assembly 10 includes a first pole piece unit and a second pole piece unit that are wound, and the polarity of the first pole piece unit is opposite to that of the second pole piece unit. As shown in Figure 2, it is a schematic structural diagram of the three-dimensional structure of the first pole piece unit 11 or the second pole piece unit 12 in an unfolded state of an embodiment of the present application. The first pole piece unit 11 and the second pole piece unit 12 both have a length direction X. The first pole piece unit 11 and the second pole piece unit 12 are stacked and the length directions X of the two are the same, and the first pole piece unit 11 and the second pole piece unit 12 are wound along the length directions X of the two to obtain an electrode assembly 10 with a wound structure. As shown in Figure 3, it is a cross-sectional view of the electrode assembly 10 with a wound structure. It can be seen from Figure 3 that the first pole piece unit 11 and the second pole piece unit 12 are alternately arranged.

[0062] The first electrode unit 11 and the second electrode unit 12 each include an electrode 100 and a tab 400. The tab 400 is provided on the electrode 100 and is used to electrically connect to an external circuit. The polarity of the first electrode unit 11 and the second electrode unit 12 are opposite, that is, one of the electrode 100 of the first electrode unit 11 and the electrode 100 of the second electrode unit 12 is a negative electrode 120, and the other is a positive electrode 110. The tab 400 provided on the positive electrode 110 is a positive tab 400, and the tab 400 provided on the negative electrode 120 is a negative tab 400. For example, when the electrode 100 of the first electrode unit 11 is a positive electrode 110, the electrode 100 of the second electrode unit 12 is a negative electrode 120; when the electrode 100 of the first electrode unit 11 is a negative electrode 120, the electrode 100 of the second electrode unit 12 is a positive electrode 110.

[0063] At least one of the first pole piece unit 11 and the second pole piece unit 12 further includes an isolation membrane 200. The isolation membrane 200 has insulating properties. At least a portion of the isolation membrane 200 is disposed between the pole piece 100 of the first pole piece unit 11 and the pole piece 100 of the second pole piece unit 12 to prevent the two pole pieces 100 of opposite polarity from short-circuiting. The material of the isolation membrane 200 may include at least one of polyethylene and polypropylene. The present embodiment of the present application does not limit the material of the isolation membrane 200. Any conventional material used in the art for preparing the isolation membrane 200 is applicable to the present application.

[0064] Among them, the isolation membrane 200 includes a first diaphragm 210 and a second diaphragm 220 which are arranged on opposite sides of the electrode 100 in the thickness direction Z of the electrode 100. The first diaphragm 210 includes a first extension portion 201 extending from the edge of the electrode 100 along the width direction Y of the electrode 100, and the second diaphragm 220 includes a second extension portion 202 extending from the edge of the electrode 100 along the width direction Y of the electrode 100. The electrode ear 400 is provided on the electrode 100, and the electrode ear 400 extends out of the isolation membrane 200 between the first extension portion 201 and the second extension portion 202. The first extension portion 201 is connected to the second extension portion 202 to form a sealing area 101. The number of sealing areas 101 is at least two, and the sealing area 101 avoids the electrode ear 400.

[0065] In the embodiment of the present application, the portion of the separator 200 extending beyond the adhesive area is provided with multiple sealing areas 101 to prevent the positive electrode 110 and the negative electrode 120 from contacting each other due to shrinkage, folding of the separator 200, or movement of the electrode 100 during the battery cell's fall, thereby improving the safety and cycle performance of the battery cell. Specifically, the portions of the first separator 210 and the second separator 220 that extend beyond the width of the electrode 100 are interconnected and solidified in a certain manner to form the sealing areas 101, so that the electrode 100 is constrained between the first separator 210 and the second separator 220, preventing the positive electrode 110 and the negative electrode 120 from contacting each other, which could lead to voltage drop failure and short circuit in the battery cell. Adjacent sealing areas 101 are spaced apart, and the first and second diaphragms 210, 220 have unconnected portions extending beyond the width of the electrode sheet 100. This allows electrolyte to flow between the first and second diaphragms 210, 220 from the unconnected regions, ensuring that the electrode assembly 10 maintains good electrolyte wetting. During the process of forming the sealing areas 101 on the first and second extensions 201, 202, the sealing areas 101 are positioned to avoid the tabs 400, preventing overpressure on the tabs 400 and the corresponding electrode sheet 100, effectively improving the stability of the resulting battery cell performance.

[0066] Optionally, the sealing area 101 is spaced apart from the electrode 100 to buffer the impact of the electrolyte on the isolation membrane 200 and prevent the sealing area 101 from moving to abutting the edge of the electrode 100 when the isolation membrane 200 is impacted by the electrolyte, causing the sealing area 101 to tear. In conjunction with Figures 4 and 5, the distance from the edge of the sealing area 101 facing the electrode 100 to the edge of the electrode 100 is S, and S satisfies: 0.1mm≤S≤1mm, and S can be 0.1mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or a range consisting of any two thereof, for example, 0.1mm≤S≤0.5mm, 0.1mm≤S≤0.6mm, 0.1mm≤S≤0.7mm, 0.1mm≤S≤0.8mm, 0.1mm≤S≤0.9mm, etc.

[0067] At least part of the sealing region 101 is arranged at intervals along the length direction X of the electrode tab 100. For example, the number of the sealing regions 101 arranged at intervals along the length direction X of the electrode tab 100 is at least two. The tab 400 extends out of the separator 200 between the first extension portion 201 and the second extension portion 202 along the width direction Y of the electrode tab 100. In the length direction X of the electrode tab 100, one of the sealing regions 101 is arranged on one side of the tab 400 and adjacent to the tab 400, and the other sealing region 101 is arranged on the other side of the tab 400 and adjacent to the tab 400. Wherein, the distance from the edge of the sealing region 101 adjacent to the tab 400 to the edge of the tab 400 is Q, and Q satisfies: 0.2mm ≤ Q ≤ 2mm. Q can be 0.3mm, 0.6mm, 0.9mm, 1.1mm, 1.5mm, 1.8mm or the range composed of any two of them. For example, 0.2mm ≤ Q ≤ 0.3mm, 0.2mm ≤ Q ≤ 0.6mm, 0.2mm ≤ Q ≤ 0.9mm, 0.2mm ≤ Q ≤ 1.1mm, 0.2mm ≤ Q ≤ 1.5mm, 0.2mm ≤ Q ≤ 1.8mm. In addition, when Q satisfies 0.2mm ≤ Q ≤ 2mm, the separator 200 can also act on the surface of the tab 400 to improve the stability of the tab 400 installed on the electrode tab 100.

[0068] In the length direction X of the electrode tab 100, the length of the electrode tab 100 is L, and the length of the sealing region 101 is l0. L and l0 satisfy: 1 < L / l0 ≤ 200. L / l0 can be 1, 20, 30, 50, 60, 100, 130, 150, 200 or the range composed of any two of them. For example, 1 < L / l0 ≤ 20, 1 < L / l0 ≤ 30, 1 < L / l0 ≤ 50, 1 < L / l0 ≤ 60, 1 < L / l0 ≤ 100, 1 < L / l0 ≤ 130, 1 < L / l0 ≤ 150, etc. In the above range, the length of the sealing region 101 is appropriate, and the structure of the sealing region 101 is firm, which can effectively resist the impact of the electrolyte.

[0069] In the length direction X of the electrode tab 100, the width between two adjacent sealing regions 101 is a1, and L / a1 satisfies: 200 ≤ L / a1 ≤ 4000. L / a1 can be 200, 300, 500, 800, 1000, 2000, 4000 or the range composed of any two of them. For example, 200 ≤ L / a1 ≤ 300, 200 ≤ L / a1 ≤ 500, 200 ≤ L / a1 ≤ 800, 200 ≤ L / a1 ≤ 1000, 300 ≤ L / a1 ≤ 500, etc. In the above spacing range, the spacing between two adjacent sealing regions 101 in the length direction X of the electrode tab 100 is appropriate, which is helpful for the electrolyte to infiltrate.

[0070] Wherein, 1≤l0 / a1≤4000, l0 / a1 can be 10, 100, 500, 800, 1000, 2000, 4000 or a range consisting of any two thereof, for example, 1≤l0 / a1≤10, 1≤l0 / a1≤100, 1≤l0 / a1≤500, 1≤l0 / a1≤800, 1≤l0 / a1≤1000, 1≤l0 / a1≤2000, 10≤l0 / a1≤4000, etc. By controlling the ratio of l0 and a1 within an appropriate range, it is convenient to distribute the length and spacing of the sealing area 101 in the length direction X of the electrode piece 100, so that the sealing area 101 is firmly encapsulated in the length direction X of the electrode piece 100 and has a good electrolyte infiltration effect.

[0071] Furthermore, in the length direction X of the electrode 100 , the lengths l0 of the plurality of sealing areas 101 (first sealing areas 1011 ) may be the same or different, and the width a1 between any two adjacent sealing areas 101 (first sealing areas 1011 ) may be the same or different.

[0072] It is understandable that the dimension of the pole piece 100 in the length direction X is larger than the dimension of the pole piece 100 in the width direction Y. Correspondingly, the dimension of the isolation membrane 200 in the length direction X of the pole piece 100 is larger than the dimension of the isolation membrane 200 in the width direction Y of the pole piece 100. In addition, in the wound electrode assembly 10, the pole piece 100 and the isolation membrane 200 can interact with each other. In the long direction (winding direction) of the pole piece 100, the pole piece 100 can provide support for the isolation membrane 200, which helps to reduce the shrinkage of the isolation membrane 200. Therefore, when impacted, the shrinkage or folding of the isolation membrane 200 in the width direction Y of the pole piece 100 will more easily cause the two pole pieces 100 with opposite polarities to short-circuit. In the embodiment of the present application, the portion of the isolation membrane 200 extending out of the pole piece 100 in the width direction Y of the pole piece 100 is provided with a sealing area 101, which can solve the problem of the two pole pieces 100 with opposite polarities being short-circuited due to the shrinkage of the pole piece 100 in the width direction Y.

[0073] When the first extension portion 201 and the second extension portion 202 are spaced apart at both ends of the length direction X of the pole piece 100, optionally, as shown in Figure 4, the width of the first extension portion 201 and the second extension portion 202 extending out of the pole piece 100 in the length direction X of the pole piece 100 is set to be greater than the width of the first extension portion 201 and the second extension portion 202 extending out of the pole piece 100 in the width direction Y of the pole piece 100. By increasing the width of the first extension portion 201 and the second extension portion 202 extending out of the pole piece 100 in the length direction X of the pole piece 100, the short circuit of the two pole pieces 100 with opposite polarities caused by the contraction of the isolation membrane 200 in the length direction X of the pole piece 100 is prevented.

[0074] Of course, when the isolation membrane 200 is not fixed at both ends of the pole piece 100 in the length direction X, the isolation membrane 200 may still shrink at both ends of the pole piece 100 in the length direction X, resulting in a short circuit between the two pole pieces 100 with opposite polarities. Optionally, a portion of the sealing areas 101 (first sealing areas) are arranged at intervals along the length direction X of the pole piece 100, and another portion of the sealing areas 101 (second sealing areas) are arranged at intervals along the width direction Y of the pole piece 100, that is, the portion of the isolation membrane 200 extending out of the pole piece 100 in the width direction Y of the pole piece 100 and the length direction X of the pole piece 100 has a sealing area 101, which effectively prevents the short circuit between the two pole pieces 100 with opposite polarities caused by the shrinkage of the isolation membrane 200 in the length direction X and the width direction Y of the pole piece 100.

[0075] In the width direction Y of the pole piece 100, the width of the pole piece 100 is W, and the width of the sealing area 101 is w0. W and w0 satisfy: 1≤W / w0≤20, and W / w0 can be a range of 1, 4, 8, 10, 15, 18, 20 or any two of them, for example, 1≤W / w0≤4, 1≤W / w0≤8, 1≤W / w0≤15, 4≤W / w0≤20, etc.

[0076] In the width direction Y of the pole piece 100, the width between two adjacent sealing areas 101 is a2, and W and a2 satisfy: 20≤W / a2, W / a2 can be 20, 25, 50, 80, 100, 200, 400 or any numerical range therein, for example, 25≤W / a2, 50≤W / a2, 80≤W / a2, 100≤W / a2, 200≤W / a2, 400≤W / a2, etc.

[0077] Wherein, w0 and a2 satisfy: 1≤w0 / a2, w0 / a2 can be 20, 25, 50, 80, 100, 200, 400, or any range therein, for example, 20≤w0 / a2, 25≤w0 / a2, 50≤w0 / a2, 80≤w0 / a2, 100≤w0 / a2, 200≤w0 / a2. Similarly, by controlling the ratios of W, w0, and a2 within the above ranges, it is convenient to distribute the length and spacing of the sealing area 101 in the width direction Y of the electrode piece 100, so that the sealing area 101 is firmly encapsulated in the width direction Y of the electrode piece 100 and has good electrolyte infiltration effect.

[0078] Furthermore, in the width direction Y of the electrode 100 , the widths w0 of the plurality of sealing areas 101 (second sealing areas) may be the same or different, and the width a2 between any two adjacent sealing areas 101 (second sealing areas) may be the same or different.

[0079] Optionally, the first diaphragm 210 and the second diaphragm 220 are integrally provided. Specifically, in the width direction Y of the pole piece 100, the first extension 201 includes a first portion 211 located on one side of the pole piece 100. Part of the first portion 211 is connected to the second extension 202 to form at least two sealing areas 101. The end of the first diaphragm 210 facing away from the first portion 211 is integrally formed with the second diaphragm 220, forming a fully encapsulated structure directly on one side of the pole piece 100. For example, a diaphragm substrate can be selected to be wrapped from one side of the pole piece 100 through one of the long sides of the pole piece 100 to the other side of the pole piece 100. In this way, in the thickness direction Z of the pole piece 100, the portion of the diaphragm substrate located on one side of the pole piece 100 forms the first diaphragm 210, and the portion located on the other side of the pole piece 100 forms the second diaphragm 220. In this way, the cutting process of the isolation membrane 200 is reduced, which helps to improve assembly efficiency.

[0080] Optionally, the first diaphragm 210 and the second diaphragm 220 are provided separately. Specifically, the first extension portion 201 includes a first portion 211, a second portion 212, a third portion 213, and a fourth portion 214. In the width direction Y of the electrode 100, the first portion 211 is located on one side of the electrode 100, and the second portion 212 is located on the other side of the electrode 100. In the length direction X of the electrode 100, the third portion 213 is located on one side of the electrode 100, and the fourth portion 214 is located on the other side of the electrode 100. Part of the first portion 211 is connected to the second extension portion 202 to form at least two sealing areas 101, part of the second portion 212 is connected to the second extension portion 202 to form at least one sealing area 101, part of the third portion 213 is connected to the second extension portion 202 to form at least one sealing area 101, and part of the fourth portion 214 is connected to the second extension portion 202 to form at least one sealing area 101. This helps to improve the wetting effect of the electrolyte.

[0081] Optionally, the first extension 201 and the second extension 202 are pressed together to form the sealing area 101. For example, each sealing area 101 is a hot press seal or a roll press seal. When the sealing area 101 is formed by pressing together, the tab 400 can be pressed together to form the sealing area 101 according to a predetermined pressing rule, thereby preventing overpressure on the tab 400 and the portion of the electrode sheet 100 corresponding to the tab 400, thereby improving the performance stability of the resulting electrode assembly 10.

[0082] Optionally, the first extension portion 201 and the second extension portion 202 are bonded to form the sealing area 101. For example, an adhesive layer is provided between the first extension portion 201 and the second extension portion 202, and the first extension portion 201 and the second extension portion 202 are connected by the adhesive layer to form the sealing area 101. The sealing area 101 can be formed by applying an adhesive to the surface of at least one of the first extension portion 201 and the second extension portion 202 and then bonding them together, with the adhesive avoiding the tab 400.

[0083] As shown in Figure 6, the electrode assembly 10 in the wound state includes a straight portion 310 and a curved portion 320, wherein the stress of the curved portion 320 is relatively large. Due to the existence of stress, the first extension portion 201 and the second extension portion 202 of the sealing area 101 formed by the curved portion 320 are more likely to be loosely connected. When the stress is large, wrinkles are likely to occur, which interfere with the isolation membrane 200 in other areas.

[0084] Optionally, both the curved portion 320 and the straight portion 310 are provided with a sealing area 101 , and the length of the sealing area 101 of the curved portion 320 is smaller than that of the straight portion 310 , so as to reduce the influence of the stress of the curved portion 320 on the structural stability of the sealing area 101 .

[0085] Preferably, the straight portion 310 is provided with a sealing area 101, and the first extension portion 201 and the second extension portion 202 of the curved portion 320 are spaced apart. The surface of the straight portion 310 described in the embodiment of the present application can be flat (i.e., the straight portion 310 is flat), or the straight portion 310 can have a slight curvature, but the curvature of the straight portion 310 is smaller than that of the curved portion 320, and the curvature of the straight portion 310 and the curvature of the curved portion 320 are significantly different.

[0086] 6 and 7 , when the straight portion 310 has a sealing area 101, the sealing area 101 of the straight portion 310 is arranged in the thickness direction of the electrode assembly 10, and the first extension 201 and the second extension 202 of the curved portion 320 are spaced apart. This helps improve the electrolyte infiltration efficiency. The width direction of the electrode assembly 10 is the same as the width direction Y of the electrode sheet 100, and the thickness direction of the electrode assembly 10 is the thickness direction Y of the electrode sheet 100 of the straight portion 310.

[0087] Of course, in some other embodiments, the sealing area 101 of the straight portion 310 may also be staggered or partially overlapped in the thickness direction Z of the electrode assembly 10 .

[0088] The electrode assembly 10 is in a wound state, and two electrode sheets 100 of opposite polarity are alternately arranged in the thickness direction Z of the electrode assembly 10. A portion of the separator 200 is required between any two electrode sheets 100 of opposite polarity to separate the two electrode sheets 100 of opposite polarity and prevent short circuit. Optionally, referring to FIG3 , one of the electrode sheets 100 is configured to be constrained between the first diaphragm 210 and the second diaphragm 220 of the same separator 200. Specifically, the electrode assembly 10 includes two electrode sheets 100, at least two electrode tabs 400, and a separator 200; at least one electrode tab 400 is provided on one of the electrode sheets 100, and the electrode sheet 100 is provided between the first diaphragm 210 and the second diaphragm 220 of the separator 200 to form a first electrode sheet unit 11; the remaining electrode tab 400 is provided on the other electrode sheet 100 to form a second electrode sheet unit 12; the polarity of the two electrode sheets 100 is opposite. In this way, in the wound electrode assembly 10 , the portions of the two electrode sheets 100 with opposite polarities can be isolated in the thickness direction Z of the electrode assembly 10 .

[0089] Optionally, one electrode piece 100 of the electrode assembly 10 is constrained between the first diaphragm 210 and the second diaphragm 220 of one of the separators 200, and the other electrode piece 100 is constrained between the first diaphragm 210 and the second diaphragm 220 of the other separator 200. Specifically, the electrode assembly 10 includes two electrode pieces 100, at least two electrode tabs 400, and two separators 200; at least one electrode tab 400 is provided on one of the electrode pieces 100 and the electrode piece 100 is provided between the first diaphragm 210 and the second diaphragm 220 of one of the separators 200 to form a first electrode piece unit 11; the remaining electrode tab 400 is provided on the other electrode piece 100 and the electrode piece 100 is provided between the first diaphragm 210 and the second diaphragm 220 of the other separator 200 to form a second electrode piece unit 12; the polarities of the two electrode pieces 100 are opposite. In this way, the isolation film 200 can provide more comprehensive protection for the electrode 100 and more effectively prevent the two electrode 100 with opposite polarities from being short-circuited.

[0090] The pole tab 400 extends out of the isolation membrane 200 along the width direction Y of the pole piece 100. In the width direction Y of the pole piece 100, the width of one pole piece 100 is smaller than the width of the other pole piece 100. At least the pole piece 100 with the smaller width is arranged between the first diaphragm 210 and the second diaphragm 220 of the isolation membrane 200. In this way, when the isolation membrane 200 extends out from the edge of the pole piece 100 with the smaller width, the first extension portion 201 and the second extension portion 202 of the isolation membrane 200 can also separate the two adjacent parts of the pole piece 100 with the larger width. At the same time, the amount of isolation membrane 200 is saved, and the space occupied by the isolation membrane 200 is saved, which helps to improve the energy density of the battery cell using the electrode assembly 10 of the present application.

[0091] Optionally, the electrode piece 100 with a smaller width is the positive electrode piece 110 , and the electrode piece 100 with a larger width is the negative electrode piece 120 .

[0092] The electrode assembly 10 also includes a protective layer 410 provided on the surface of the tab 400, and the protective layer 410 avoids the connection between the tab 400 and the pole piece 100. The protective layer 410 is used to prevent the tab 400 from contacting other structures, for example, preventing the tab 400 from contacting sharp structures such as burrs generated during the processing of other structures. Among them, the protective layer 410 is provided on the surface of the tab 400 extending out of the isolation membrane 200. Furthermore, the protective layer 410 also extends between the isolation membrane 200 and the tab 400, which helps to buffer the stress of the tab 400 installed on the pole piece 100. For example, the protective layer 410 is a tab glue. The protective layer 410 can also be used to connect with other structures of the battery cell to fix the position of the tab 400. For example, the protective layer 410 is connected to the outer packaging (packaging bag) of the battery cell.

[0093] An embodiment of the present application also provides a battery cell, which includes an outer packaging and the electrode assembly 10 as described above. The electrode assembly 10 is arranged in the internal space of the outer packaging, wherein the tab 400 extends from the pole piece 100 out of the outer packaging and is used to electrically connect to an external circuit, and the tab 400 is fixed to the outer packaging.

[0094] In the embodiment of the present application, the battery cells include soft-pack batteries and hard-shell batteries. The outer packaging of the soft-pack battery can be an aluminum-plastic film. The tab 400 is connected to the aluminum-plastic film when it extends out of the outer packaging. Furthermore, the tab 400 is connected to the aluminum-plastic film by a protective layer 410 provided on the surface of the tab 400. For example, the material of the protective layer 410 includes polypropylene (PP) or polyethylene (PE). The outer packaging of the hard-shell battery can be an aluminum shell. The hard-shell battery also includes a pole provided on the outer packaging. The tab 400 can extend from the pole piece 100 to connect to the pole post, and is connected to the external circuit through the pole post. Alternatively, the tab 400 can also extend from the pole piece 100 to connect to the outer shell, and then be electrically connected to the external circuit.

[0095] The numerical values ​​and numerical ranges involved in the embodiments of the present application are approximate values. Due to the influence of the manufacturing process, there may be a certain range of errors. Those skilled in the art may consider this part of the error to be negligible.

[0096] In the description of this application, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.

[0097] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrode assembly, characterized in that: It includes a first electrode tab unit and a second electrode tab unit arranged in a wound manner; the polarities of the first electrode tab unit and the second electrode tab unit are opposite; At least one of the first electrode tab unit and the second electrode tab unit includes an electrode tab, a tab, and a separator film. The separator film includes a first separator and a second separator disposed on opposite sides of the electrode tab in the thickness direction of the electrode tab. The first separator includes a first extension portion extending out of the edge of the electrode tab along the width direction of the electrode tab, and the second separator includes a second extension portion extending out of the edge of the electrode tab along the width direction of the electrode tab. The tab is disposed on the electrode tab, and the tab extends out of the separator film between the first extension portion and the second extension portion. The first extension portion and the second extension portion are connected to form a sealing area. The number of the sealing areas is at least two, and the sealing areas avoid the tab.

2. The electrode assembly according to claim 1, characterized in that: At least part of the sealing areas are arranged at intervals along the length direction of the electrode tab; in the length direction of the electrode tab, the length of the electrode tab is L, the length of the sealing area is l0, and the distance between two adjacent sealing areas is a1, where 1 < L / l0 ≤ 200; and / or, 200 ≤ L / a1 ≤ 4000; and / or, 1 ≤ l0 / a1 ≤ 4000.

3. The electrode assembly according to claim 2, characterized in that: One part of the sealing areas are arranged at intervals along the length direction of the electrode tab, and the other part of the sealing areas are arranged at intervals along the width direction of the electrode tab; in the width direction of the electrode tab, the width of the electrode tab is W, the width of the sealing area is w0, and the width between two adjacent sealing areas is a2, where 1 ≤ W / w0 ≤ 20; and / or, W / a2 ≥ 20; and / or, w0 / a2 ≥ 1.

4. The electrode assembly according to claim 1, characterized in that: In the width direction of the electrode tab, the first extension portion includes a first part located on one side of the electrode tab, and a partial area of the first part is connected to the second extension portion to form at least two of the sealing areas; In the width direction of the electrode tab, one end of the first separator背离 the first part is integrally formed with the second separator; or, In the width direction of the electrode tab, the first extension portion includes a second part背离 the first part, and a partial area of the second part is connected to the second extension portion to form at least one of the sealing areas.

5. The electrode assembly according to claim 1, wherein Each of the sealing areas is a hot-pressed sealing portion or a roll-pressed sealing portion; or, A bonding layer is provided between the first extension portion and the second extension portion, and the first extension portion and the second extension portion are connected through the bonding layer to form the sealing area.

6. The electrode assembly according to claim 1, characterized in that: The electrode assembly includes a straight portion and a bent portion, and the sealing area is disposed on the straight portion.

7. The electrode assembly according to claim 6, characterized in that: The sealing areas are correspondingly arranged in the thickness direction of the electrode assembly, and the first extension portion and the second extension portion of the bent portion are arranged at intervals.

8. The electrode assembly according to claim 1, wherein The electrode assembly comprises two pole pieces, at least two pole ears and one isolation membrane; wherein at least one pole ear is arranged on one of the pole pieces, and the pole piece is arranged between the first diaphragm and the second diaphragm of the isolation membrane to form the first pole piece unit; the remaining pole ears are arranged on the other pole piece to form the second pole piece unit; the polarities of the two pole pieces are opposite; or, The electrode assembly includes two pole pieces, at least two pole ears and two isolation membranes; at least one of the pole ears is arranged on one of the pole pieces and the pole piece is arranged between the first diaphragm and the second diaphragm of one of the isolation membranes to form the first pole piece unit; the remaining pole ears are arranged on the other pole piece and the pole piece is arranged between the first diaphragm and the second diaphragm of the other isolation membrane to form the second pole piece unit; the polarities of the two pole pieces are opposite.

9. The electrode assembly according to claim 8, characterized in that: The pole ear extends out of the isolation membrane along the width direction of the pole piece. In the width direction of the pole piece, the width of one pole piece is smaller than the width of the other pole piece, and at least the pole piece with the smaller width is arranged between the first membrane and the second membrane of the isolation membrane.

10. The electrode assembly according to claim 9, characterized in that: The electrode sheet with a smaller width is a positive electrode sheet, and the electrode sheet with a larger width is a negative electrode sheet.

11. The electrode assembly according to claim 1, characterized in that: The sealing area is spaced apart from the pole piece, and the distance from the edge of the sealing area facing the pole piece to the edge of the pole piece is S, and S satisfies: 0.1mm≤S≤1mm; and / or, The pole ear extends out of the isolation membrane along the width direction of the pole piece; in the length direction of the pole piece, one of the sealing areas is arranged on one side of the pole ear, and the other sealing area is arranged on the other side of the pole ear, and the distance from the edge of the sealing area to the edge of the pole ear is Q, and Q satisfies: 0.2mm≤Q≤2mm.

12. A battery cell, characterized in that: include: Packaging bags; and The electrode assembly according to any one of claims 1-11, wherein the electrode assembly is arranged in the packaging bag.

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