Battery cell and battery

Abstract

The invention relates to the technical field of batteries, in particular to a battery cell and a battery. The battery cell comprises a first pole piece, a second pole piece and a diaphragm, the first pole piece comprises a first current collector and a first active material layer; the first pole piece comprises a first region and a second region; first active material layers are respectively arranged on two sides of the first current collector in the first region; the first active material layer is only arranged on one side of the first current collector in the second region; the second region is positioned on one side, facing the interior of the battery cell, of the first region; the first pole piece is provided with an arc section and a straight section in the first area and the second area; a through hole penetrating through the first pole piece is formed in the arc section of the first area, and the through hole avoids the second area. The first active material layer is provided with a first wire groove in the second area, and the depth of the first wire groove is smaller than the thickness of the first active material layer. The battery cell comprises an electrolyte, and the electrolyte comprises a sulfur-containing additive. By arranging the through hole and the first wire slot, the retention amount of the infolding electrolyte of the battery cell can be ensured, and the service life of the battery is prolonged.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell and a battery. Background Art

[0002] With the rapid development of battery technology, people have put forward higher requirements on battery impedance, rate and battery life.

[0003] At present, the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound to form a battery cell. After winding, the electrode sheet forms arc segments at both ends of the battery cell and a straight segment between the arc segments at both ends.

[0004] However, as the number of cycles increases, the inner fold of the battery cell is prone to electrolyte drying up, affecting the service life of the battery. Summary of the invention

[0005] Based on this, the present application provides a battery cell and a battery to solve the problem in the related art that the inner folding of the battery cell is prone to electrolyte drying up, thus affecting the service life of the battery.

[0006] In a first aspect, an embodiment of the present application provides a battery cell, the battery cell comprising a first pole piece, a second pole piece, and a separator located between the first pole piece and the second pole piece, wherein the first pole piece, the separator, and the second pole piece are stacked and wound to form the battery cell;

[0007] The first pole piece includes a first current collector and a first active material layer located on both sides of the first current collector; the first active material layer includes a silicon-carbon composite material;

[0008] The first pole piece includes a first region where the first active material layer is respectively arranged on both sides of the first current collector and a second region where the first active material layer is arranged only on one side of the first current collector, and the second region is located on a side of the first region facing the inside of the battery cell; the first pole piece has an arc segment located at the end of the battery cell and a straight segment located in the middle of the battery cell in both the first region and the second region;

[0009] A through hole penetrating the first pole piece is provided on the arc segment of the first region, and the through hole avoids the second region;

[0010] The first active material layer is provided with a first linear groove on the second region, the first linear groove is located on a side of the first active material layer away from the first current collector, and the depth of the first linear groove is less than the thickness of the first active material layer;

[0011] The battery cell includes an electrolyte, the electrolyte includes a sulfur-containing additive, the sulfur-containing additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone or vinyl sulfate, and the content of the sulfur-containing additive ranges from 0.1 to 6%;

[0012] The small-diameter end of the through hole faces the inner side of the battery cell, and the large-diameter end of the through hole faces the outer side of the battery cell;

[0013] The aperture of the large-diameter end is D1, and D1 satisfies:

[0014] 30μm ≤ D1 ≤ 200μm.

[0015] In a possible implementation, along the winding direction of the first pole piece, there is a gap between the edge where the first region is connected to the second region and the through hole.

[0016] In a possible implementation, the first pole piece has a plurality of arc segments in the first region;

[0017] Among the plurality of arc segments of the first pole piece in the first region, the through hole avoids the arc segment adjacent to the second region.

[0018] In a possible implementation, a plurality of through holes are provided on the arc segment of the first pole piece in the first region;

[0019] Among the plurality of through holes on the same arc segment, the distance between two adjacent through holes is D2, and D2 satisfies:

[0020] 100μm ≤ D2 ≤ 5000μm; and / or,

[0021] A plurality of through holes are provided on the arc segment of the first pole piece in the first region, and the plurality of through holes on the arc segment define a punched area;

[0022] Along the winding direction of the first pole piece, the size of the arc segment is less than or equal to the size of the corresponding punched area; and / or,

[0023] Along the winding direction of the first pole piece, from the inner side of the battery cell to the outer side of the battery cell, the total area of the through holes at different arc segment positions gradually increases.

[0024] In a possible implementation, the number of the first wire grooves is multiple, and the multiple first wire grooves define a first wire bonding area;

[0025] A plurality of through holes are provided on the arc segment, and the plurality of through holes on the arc segment define a punched area;

[0026] There is a first distance between the first wire bonding area and the adjacent punched area, and the first distance is greater than or equal to 1mm.

[0027] In a possible implementation, there is a second distance between the end of the second region far from the first region and the first wire bonding area, and the second distance is d1, and d1 satisfies:

[0028] 3mm ≤ d1 ≤ 10mm; and / or,

[0029] The first wiring area extends toward one end of the first region to the edge where the second region connects to the first region; and / or,

[0030] At least some of the first wire grooves are arranged in parallel and spaced apart, and the interval between two adjacent and parallel first wire grooves is D3, and D3 satisfies:

[0031] 300μm≤D3≤3000μm;

[0032] and / or,

[0033] The width of the first wire slot is D4, which satisfies:

[0034] 10μm≤D4≤200μm;

[0035] and / or,

[0036] The ratio of the depth of the first linear groove to the thickness of the first active material layer is in the range of 0.15-0.5.

[0037] In one possible implementation, at least one row of concave-convex structures is formed on the second region of the first pole piece, and each row of concave-convex structures is arranged at intervals along the width direction of the first pole piece. The concave-convex structures form a concave portion on one side of the first pole piece in the thickness direction, and the concave-convex structures form a convex portion on the other side of the first pole piece in the thickness direction.

[0038] In one possible implementation, along the width direction of the first pole piece, the edge of the first pole piece has a second wiring area, and the first active material layer is provided with a plurality of second wire grooves on the second wiring area, and the second wire grooves are located on the side of the first active material layer away from the first current collector, and the depth of the second wire grooves is less than the thickness of the first active material layer.

[0039] In a possible implementation, the interval between two adjacent second wire slots is D5, and D5 satisfies:

[0040] 500μm≤D5≤2000μm;

[0041] and / or,

[0042] The width of the second wire groove is D6, and D6 satisfies:

[0043] 10μm≤D6≤200μm;

[0044] and / or,

[0045] The ratio between the depth of the second groove and the thickness of the first active material layer is in the range of 0.15-0.6;

[0046] and / or,

[0047] The size of the second bonding area in the width direction of the first pole piece is 10 mm-35 mm.

[0048] In a second aspect, an embodiment of the present application provides a battery, including the above-mentioned battery cell.

[0049] The battery cell and battery provided by the present application, the battery cell is formed by laminating and winding a first electrode sheet, a separator and a second electrode sheet. The first electrode sheet includes a first region where first active material layers are respectively disposed on both sides of the first current collector and a second region where the first active material layer is only disposed on one side of the first current collector. It can be understood that the first region is the double-sided region of the first electrode sheet, and the second region is the single-sided region of the first electrode sheet. The second region is located on the side of the first region facing the inside of the battery cell. During the winding process of the first electrode sheet, the winding stress received by the first electrode sheet in the second region is greater than the winding stress received by the first electrode sheet in the first region. A through hole penetrating the first electrode sheet is provided on the arc segment of the first electrode sheet in the first region. Through the through hole, the reflux of the electrolyte at the corresponding arc segment position can be accelerated, and the electrolyte can flow through the through hole to the inner fold of the battery cell. A first groove is provided on the second region of the first active material layer. The first groove can play a role in storing the electrolyte and increase the wetting of the electrolyte on the first electrode sheet. The above settings can ensure the retention amount of the electrolyte in the inner fold of the battery cell and improve the service life of the battery. The through hole can also ensure the retention amount of the electrolyte at the arc segment position of the first electrode sheet in the first region, so that it is not easy to deposit lithium at the arc segment position of the first electrode sheet in the first region, and reduce the internal resistance of the battery cell. At the same time, during the cycling of the battery, the through hole and the first groove provide space for the expansion of the first active material layer, which is beneficial to alleviating the problem of battery cell expansion. The through hole avoids the second region, that is, the first electrode sheet is not provided with a through hole in the second region. The first electrode sheet will not form burrs on the side of the first current collector facing away from the first active material layer due to the setting of the through hole in the second region, and the position of the first current collector in the second region will not be damaged due to the setting of the first groove. When the second region of the first electrode sheet forms an arc segment, the first electrode sheet will not be prone to "powder falling" in the second region due to the through hole, avoiding short circuit of the battery cell caused by the burrs on the first electrode sheet or the active material falling from the first electrode sheet contacting the second electrode sheet. Not setting a through hole in the second region of the first electrode sheet can also ensure the tensile strength of the first electrode sheet in the second region. The above settings can improve the safety of the battery and further improve the service life of the battery. The small-diameter end of the through hole faces the inside of the battery cell, and the large-diameter end of the through hole faces the outside of the battery cell; the aperture of the large-diameter end of the through hole is between 30 μm and 200 μm, which is convenient for the electrolyte outside the battery cell to flow through the through hole to the inside of the battery cell. The first electrode sheet can be a negative electrode sheet. During the charge and discharge process of the battery cell, the part of the first active material layer located at the position of the through hole wall is also in contact with the electrolyte. A sulfur-containing additive is added to the electrolyte, which is preferentially reduced and decomposed at the negative electrode and participates in the formation of a dense SEI film containing alkyl sulfonate, thereby reducing the side reaction between the negative electrode and the electrolyte, and further inhibiting the gas generation in the hole. The above settings can avoid the deformation of the aperture of the through hole due to the increase in the gas generation amount in the through hole, and ensure that the electrolyte can smoothly flow through the through hole to the inner fold of the battery cell. Description of the Drawings

[0050] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0051] Figure 1 Structural schematic diagram of the battery cell provided by the embodiment of the present application;

[0052] Figure 2 Structural schematic diagram of the first electrode provided by the embodiment of the present application;

[0053] Figure 3 Top view of the first type of first electrode provided by the embodiment of the present application;

[0054] Figure 4 Top view of the second type of first electrode provided by the embodiment of the present application;

[0055] Figure 5 Top view of the third type of first electrode provided by the embodiment of the present application;

[0056] Figure 6 Top view of the fourth type of first electrode provided by the embodiment of the present application;

[0057] Figure 7 Top view of the fifth type of first electrode provided by the embodiment of the present application.

[0058] Explanation of reference numerals:

[0059] 100 - First electrode; 110 - First current collector; 120 - First active material layer; 121 - First wire groove; 122 - Second wire groove; 131 - First region; 132 - Second region; 133 - Third region; 140 - Through hole; 151 - Arc segment; 152 - Straight segment; 160 - Drilling area; 170 - First wire bonding area; 180 - Second wire bonding area;

[0060] 200 - Second electrode;

[0061] 300 - Separator. Detailed implementation manners

[0062] To make the objectives, technical solutions and advantages of this application more clear, the following will describe in more detail the technical solutions in the embodiments of this application with reference to the accompanying drawings in the preferred embodiments of this application. In the drawings, the same or similar reference numerals denote the same or similar components or components with the same or similar functions from beginning to end. The described embodiments are some but not all of the embodiments of this application. The embodiments described below by referring to the drawings are exemplary and are intended to explain this application and should not be construed as a limitation to this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application. The following will explain in detail the embodiments of this application with reference to the drawings.

[0063] In the description of this application, it should be noted that, unless otherwise clearly defined and limited, the terms "install", "connect", and "couple" should be understood in a broad sense. For example, it may be a fixed connection, or an indirect connection through an intermediate medium, or the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0064] In the description of this application, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships in the drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0065] The terms "first", "second", "third" (if any) in the specification, claims and drawings of this application are used to distinguish similar objects and do not necessarily describe a specific order or sequence.

[0066] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or display that includes a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these process, method, product or display.

[0067] In the prior art, the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound to form the battery cell. After winding, the electrode sheets form arc segments at both ends of the battery cell and a straight segment between the two arc segments at both ends. The electrode sheets, especially the silicon-doped negative electrode sheets, have increased cyclic swelling as the number of battery cycles increases, and internal folding of the battery cell, i.e., the middle part of the wound battery cell, is prone to electrolyte dry-out, affecting the service life of the battery. In addition, the active material layer of the electrode sheet at the arc segment position is more compacted when the electrode sheet expands due to the limitation of the arc segment shape. The electrode sheet is prone to electrolyte dry-out at the arc segment, prone to lithium plating at the arc segment, and causes an increase in the internal resistance of the battery cell.

[0068] After repeated thinking and verification, the inventor found that if through holes are formed in the arc segments of the electrode sheets, during the cycling of the battery, the electrolyte can flow back through the through holes, which can ensure the retention amount of the electrolyte in the arc segments of the electrode sheets. At the same time, the electrolyte can flow from the through holes on the arc segments to the internal folding of the battery cell. The electrode sheet is usually provided with a single-sided area (i.e., an area with an active material layer only on one side of the current collector) and a double-sided area (i.e., areas with active material layers on both sides of the current collector respectively). If the single-sided area of the electrode sheet is located on the side facing the inside of the battery cell after winding, the winding stress on the single-sided area is greater than that on the double-sided area during the winding process of the electrode sheet. A wire groove is formed in the active material layer of the single-sided area of the electrode sheet, and the depth of the wire groove is less than the thickness of the active material layer. While storing the electrolyte through the wire groove, it can also prevent the part of the current collector located in the single-sided area from being damaged due to the formation of the wire groove. Under the action of the through holes and the wire grooves, the retention amount of the electrolyte in the internal folding of the battery cell can be ensured. If through holes are formed in the single-sided area, burrs are likely to appear on the part of the current collector located in the single-sided area of the electrode sheet. When the single-sided area is bent to form an arc segment, if the through hole is located on the arc segment, the active material layer at the edge of the through hole may fall off. The burrs or the fallen active material layer will contact the electrode sheet of the other polarity, resulting in a short circuit. Moreover, the through holes in the single-sided area will reduce the tensile strength of the electrode sheet in the single-sided area, and the electrode sheet is prone to tensile fracture under stress in the single-sided area. By setting the aperture of the through holes, the electrolyte can flow more easily from the through holes to the internal folding of the battery cell. The through holes are formed in the negative electrode sheet, and the active material layer of the negative electrode sheet includes a silicon-carbon composite material. A sulfur-containing additive is added to the electrolyte, and the sulfur-containing additive participates in the formation of a dense SEI film containing alkyl sulfonate on the surface of the negative electrode sheet, thereby reducing the side reaction between the negative electrode and the electrolyte, further inhibiting gas generation in the through holes, and avoiding deformation of the through holes due to an increase in the gas generation amount in the through holes.

[0069] In view of this, the inventor has designed a battery cell and a battery. The first electrode of the battery cell includes a first region where first active material layers are respectively arranged on both sides of a first current collector and a second region where a first active material layer is only arranged on one side of the first current collector. The second region is located on the side of the first region facing the inside of the battery cell. By providing a through hole penetrating the first electrode in the first region of the first electrode, after the electrode is wound, the through hole is located on the arc segment of the electrode. The through hole provides a channel for the reflux of the electrolyte, ensuring the retention amount of the electrolyte at the arc segment position of the second region, and the electrolyte can flow into the battery cell through the through hole. A first groove is arranged in the first active material layer in the second region, and the electrolyte can be stored through the first groove. The through hole and the first groove are used to ensure the retention amount of the in-folded electrolyte in the battery cell. Since the risk of lithium deposition at the position of the second region of the electrode is relatively low, no through hole is provided at the position of the second region of the electrode, avoiding problems such as burrs and powder falling off at the position of the second region of the first electrode and improving the safety of the battery. The fact that no through hole is provided at the second region of the first electrode and the depth of the first groove is less than the thickness of the first active material layer can also ensure the tensile strength of the first electrode at the position of the second region. The first active material layer includes a silicon-carbon composite material, and the electrolyte of the battery cell includes a sulfur-containing additive to inhibit gas generation in the through hole and ensure the aperture size of the through hole.

[0070] The technical solutions of the battery cell and the battery provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0071] Refer to Figures 1 to 3 As shown, the battery cell provided in the embodiments of the present application includes a first electrode 100, a second electrode 200, and a separator 300 located between the first electrode 100 and the second electrode 200. The first electrode 100, the separator 300, and the second electrode 200 are stacked and wound to form a battery cell. Schematically, the first electrode 100 is a negative electrode, and the second electrode 200 is a positive electrode. After the first electrode 100, the separator 300, and the second electrode 200 are stacked, they are wound from the head to the tail to form a battery cell. That is, the battery cell provided in this embodiment is a wound core.

[0072] The first electrode 100 includes a first current collector 110 and first active material layers 120 located on both sides of the first current collector 110. Exemplarily, a copper foil can be used as the first current collector 110. The first active material layer 120 includes a silicon-carbon composite material. Exemplarily, the silicon-carbon composite material includes a porous carbon matrix, silicon grains located in the pores of the porous carbon matrix, and a carbon layer coated on the surface of the porous carbon matrix. The silicon-carbon composite material can improve the specific capacity of the first active material layer 120.

[0073] The first electrode tab 100 includes a first region 131 where first active material layers 120 are respectively disposed on both sides of a first current collector 110 and a second region 132 where a first active material layer 120 is disposed only on one side of the first current collector 110. The second region 132 is located on the side of the first region 131 facing the inside of the battery cell. Among them, the first region 131 is the double-sided area of the first electrode tab 100, the second region 132 is the single-sided area of the first electrode tab 100, and the first region 131 and the second region 132 are connected to each other. As Figure 2 shown, the end of the first current collector 110 extends beyond the end of the first active material layer 120, so that a third region 133 where no first active material layer 120 is disposed on both sides of the first current collector 110 is formed on the first electrode tab 100. The third region 133 is located on the side of the second region 132 away from the first region 131 and is connected to the second region 132. During the winding process of the first electrode tab 100, the end of the third region 133 away from the second region 132 serves as the winding starting point, and the end of the first region 131 away from the second region 132 serves as the winding ending point. When the first electrode tab 100 is wound, the winding stress received by the second region 132 is greater than the winding stress received by the first region 131.

[0074] The first electrode tab 100 has an arc segment 151 located at the end of the battery cell and a straight segment 152 located in the middle of the battery cell in both the first region 131 and the second region 132. As Figure 1 shown, the shape of the battery cell is approximately oblong. The first electrode tab 100 forms an arc segment 151 at the end position of the oblong, and the first electrode tab 100 forms a straight segment 152 at the middle position of the oblong.

[0075] A through hole 140 penetrating the first electrode tab 100 is provided on the arc segment 151 of the first region 131. Schematically, the specific position of the arc segment 151 of the first region 131 can be determined before the first electrode tab 100 is wound according to the specifications of the battery cell, and the through hole 140 can be formed on the arc segment 151 by laser drilling. The axis of the through hole 140 can extend along the thickness direction of the first electrode tab 100, that is, Figure 2 the direction indicated by the Z axis in , and the depth of the through hole 140 is equal to the thickness of the first electrode tab 100. The cross-sectional shape of the through hole 140 is not limited in this embodiment. For example, the cross-sectional shape of the through hole 140 can be square, circular, etc. It can be understood that after the first electrode tab 100, the separator 300, and the second electrode tab 200 form the battery cell, the electrolyte can pass through the through hole 140 of the first electrode tab 100 to penetrate the arc segment 151 of the first electrode tab 100, so as to form a reflux of the electrolyte at the arc segment 151 position of the first electrode tab 100.

[0076] The through holes 140 avoid the second region 132, that is, the first current collector 110 is not provided with through holes 140 in the second region 132, and all the through holes 140 are located in the first region 131. The portion of the first current collector 110 in the second region 132 is not damaged due to the provision of the through holes 140.

[0077] As Figures 1 - 5 shown, a first groove 121 is provided on the first active material layer 120 in the second region 132. The first groove 121 is located on the side of the first active material layer 120 facing away from the first current collector 110, and the depth of the first groove 121 is less than the thickness of the first active material layer 120.

[0078] Among them, the first groove 121 can be provided on the first active material layer 120 by laser scribing. The opening of the first groove 121 is located on the side of the first active material layer 120 facing away from the first current collector 110, and the width of the first groove 121 can gradually decrease from the opening to the bottom of the groove. The depth of the first groove 121 is less than the thickness of the first active material layer 120, so that the first current collector 110 will not be damaged during the process of providing the first groove 121, and no burrs will be generated on the first current collector 110, ensuring the tensile strength of the first electrode sheet 100 in the second region 132.

[0079] The battery cell includes an electrolyte, the electrolyte includes a sulfur-containing additive, the sulfur-containing additive includes at least one of 1,3 - propane sultone, 1,3 - propylene sultone or ethylene sulfate, and the content range of the sulfur-containing additive is 0.1 - 6%.

[0080] The small-diameter end of the through hole faces the inner side of the battery cell, and the large-diameter end of the through hole faces the outer side of the battery cell; optionally, the aperture of the small-diameter end is less than one-half of the aperture of the large-diameter end. During the cycling of the battery, the inner pressure of the battery cell is higher than the outer pressure. Setting the through hole 140 with the large-diameter end facing the outer side of the battery cell facilitates the electrolyte on the outer side of the battery cell to flow into the inner side of the battery cell through the through hole 140, improving the reflux ability of the electrolyte.

[0081] The aperture of the large-diameter end is D1, and D1 satisfies: 30μm ≤ D1 ≤ 200μm.

[0082] Exemplarily, the aperture D1 of the large-diameter end can be 30μm, 50μm, 150μm, 200μm, etc., and there is no unique limitation here. When the aperture D1 of the large-diameter end is less than 30μm, the aperture of the through-hole 140 is small, and the improvement effect on the electrolyte reflux is small; when the aperture D1 of the large-diameter end is greater than 200μm, the aperture of the through-hole 140 is large, and the through-hole 140 will cause the tensile strength of the first electrode sheet 100 to be low. That is to say, 30μm ≤ D1 ≤ 200μm can not only ensure the tensile strength of the first electrode sheet 100, but also ensure the reflux effect of the electrolyte at the position of the through-hole 140. In addition, the aperture of the above-mentioned large-diameter end facilitates the processing of the through-hole 140.

[0083] Preferably, 30μm ≤ D1 ≤ 180μm, which can further ensure the reflux effect of the electrolyte at the position of the through-hole 140 while further ensuring the tensile strength of the first electrode sheet 100.

[0084] In the related art, the infiltration of the electrode sheet in the inner area of the battery cell is poor, and the infiltration effect is even worse under high compaction. For the battery cell provided in this embodiment, during the winding process of the first electrode sheet 100, the winding stress received by the first electrode sheet 100 in the second area 132 is greater than the winding stress received by the first electrode sheet 100 in the first area 131. A through-hole 140 penetrating the first electrode sheet 100 is provided on the arc segment 151 of the first electrode sheet 100 in the first area 131. Through the through-hole 140, the reflux of the electrolyte at the corresponding arc segment 151 position can be accelerated, and the electrolyte can flow through the through-hole 140 to the inner fold of the battery cell, that is, the middle part of the battery cell winding. A first wire groove 121 is provided on the first active material layer 120 in the second area 132, and the first wire groove 121 can play a role in storing the electrolyte and increasing the infiltration of the electrolyte into the first electrode sheet 100. By providing the through-hole 140 and the first wire groove 121 on the first electrode sheet 100, the retention amount of the electrolyte in the inner fold of the battery cell can be ensured, and the service life of the battery can be improved.

[0085] In addition, the through-hole 140 can also ensure the retention amount of the electrolyte at the arc segment 151 position of the first electrode sheet 100 in the first area 131, so that it is not easy to deposit lithium at the arc segment 151 position of the first electrode sheet 100 in the first area 131, and the internal resistance of the battery cell is reduced. At the same time, during the cycling of the battery, the through-hole 140 and the first wire groove 121 provide space for the expansion of the first active material layer 120, which is beneficial to alleviating the problem of battery cell expansion.

[0086] The through hole 140 avoids the second region 132, that is, the first pole piece 100 is not provided with the through hole 140 in the second region 132. In the second region 132 of the first pole piece 100, burrs will not be formed on the side of the first current collector 110 facing away from the first active material layer 120 due to the setting of the through hole 140. When the arc segment 151 is formed in the second region 132 of the first pole piece 100, the first pole piece 100 will not be prone to "powder dropping" in the second region 132 due to the through hole 140, avoiding short circuits in the battery caused by the contact between the burrs on the first pole piece 100 or the active material dropped from the first pole piece 100 and the second pole piece 200. The first pole piece 100 not being provided with the through hole 140 in the second region 132 can also ensure the tensile strength of the first pole piece 100 in the second region 132, and the position of the first current collector 110 in the second region 132 will not be damaged due to the setting of the first wire groove 121. The above settings can improve the safety of the battery and further extend the service life of the battery.

[0087] The large-diameter end of the through hole 140 faces the outside of the battery cell, and the aperture of the large-diameter end is between 30 μm and 200 μm, facilitating the flow of the electrolyte outside the battery cell to the inside of the battery cell through the through hole 140. The first pole piece 100 can be a negative electrode piece. During the charge and discharge process of the battery cell, the part of the first active material layer 120 located at the position of the hole wall of the through hole 140 also contacts the electrolyte. A sulfur-containing additive is added to the electrolyte, which is preferentially reduced and decomposed at the negative electrode and participates in the formation of a dense SEI film containing alkyl sulfonate, thereby reducing the side reaction between the negative electrode and the electrolyte and further inhibiting gas generation in the hole. The above settings can prevent the aperture of the through hole 140 from deforming due to the increase in the gas generation amount in the through hole 140, ensure the aperture size of the through hole 140, and ensure that the electrolyte can smoothly flow to the inner fold of the battery cell through the through hole 140.

[0088] In one embodiment, as Figure 2 and Figure 3 shown, along the winding direction of the first pole piece 100, there is a gap between the edge where the first region 131 is connected to the second region 132 and the through hole 140.

[0089] Specifically, along the length direction of the pole piece, that is, Figure 3In the direction indicated by the Y-axis in the middle, there is a gap between the junction between the first region 131 and the second region 132 and the through-hole 140, and no through-hole 140 is provided at the junction between the first region 131 and the second region 132 on the first pole piece 100. The above setting avoids burrs on the side of the first current collector 110 facing away from the first active material layer 120 in the second region 132 caused by the part of the through-hole 140 located in the second region 132 when the through-hole 140 is set. In addition, if the through-hole 140 is set at the junction between the first region 131 and the second region 132, due to the uneven thickness of the end position of the first active material layer 120, it is not convenient for positioning. The through-hole 140 avoids the junction between the first region 131 and the second region 132, and it is not easy for the through-hole 140 to be misaligned and located in the second region 132, avoiding the through-hole 140 from reducing the tensile strength of the first pole piece 100 at the position of the second region 132, so that the first pole piece 100 is not easy to break during the winding process.

[0090] In a possible implementation manner, the first pole piece 100 has a plurality of arc segments 151 in the first region 131. Specifically, the first pole piece 100 is wound in multiple layers in the first region 131, thereby forming a plurality of arc segments 151. The number of arc segments 151 of the first pole piece 100 in the first region 131 is set according to the size of the battery cell, and no unique limitation is made here.

[0091] Among the multiple arc segments 151 of the first pole piece 100 in the first region 131, the through-hole 140 avoids the arc segments 151 adjacent to the second region 132. That is to say, no through-hole 140 is provided on the arc segments 151 adjacent to the second region 132. Among them, the arc segments 151 of the first region 131 adjacent to the second region 132 are the first fold of the first region 131, and the through-hole 140 starts to be arranged from the second fold of the first region 131, that is, the next fold at the junction between the first region 131 and the second region 132 of the first pole piece 100 is the starting fold for punching.

[0092] Through the above setting, it is further possible to avoid the through-hole 140 from being located in the second region 132 of the first pole piece 100, and reliably ensure the safety of the battery.

[0093] In one embodiment, as Figure 1 and Figure 3 shown, a plurality of through-holes 140 are provided on the arc segments 151 of the first pole piece 100 in the first region 131. Specifically, a plurality of through-holes 140 are provided on the same arc segment 151 in the first region 131, and the plurality of through-holes 140 can be arranged in an array on the corresponding arc segment 151. Those skilled in the art can set the number and arrangement manner of the through-holes 140 according to needs, and no unique limitation is made here.

[0094] Among the multiple through-holes 140 on the same arc segment 151, the distance D2 between two adjacent through-holes 140 satisfies: 100 μm ≤ D2 ≤ 5000 μm.

[0095] For example, the size of D2 can be 100 μm, 500 μm, 1000 μm, 2000 μm, 3000 μm, 4000 μm, 5000 μm, etc., which is not uniquely limited here. When the distance D2 between two adjacent through-holes 140 on the same arc segment 151 is less than 100 μm, it indicates that the arrangement of the through-holes 140 on the arc segment 151 is too dense, and the overly dense through-holes 140 will result in a lower tensile strength of the first pole piece 100; when the distance D2 between two adjacent through-holes 140 on the same arc segment 151 is greater than 5000 μm, it indicates that the arrangement of the through-holes 140 on the arc segment 151 is too sparse, and the improvement effect on the electrolyte reflux is small.

[0096] In this embodiment, while ensuring the tensile strength of the first pole piece 100, the effect of electrolyte reflux at the corresponding arc segment 151 position can also be ensured, further ensuring the electrolyte retention amount of the first pole piece 100 at the arc segment 151 position in the first region 131.

[0097] Preferably, 200 μm ≤ D2 ≤ 1500 μm to further ensure the tensile strength of the first pole piece 100 while further ensuring the effect of electrolyte reflux at the corresponding arc segment 151 position.

[0098] In one embodiment, the first pole piece 100 is provided with multiple through-holes 140 on the arc segment 151 in the first region 131, and the multiple through-holes 140 on the arc segment 151 define a punching area 160. Among them, each through-hole 140 is located inside the punching area 160, and the edge of the punching area 160 is connected to the edge of the outermost through-hole 140.

[0099] Along the winding direction of the first pole piece 100, the size of the arc segment 151 is less than or equal to the size of the corresponding punching area 160. Among them, the first pole piece 100 is wound along its own length direction ( Figure 2 and Figure 3 the direction indicated by the Y-axis in

[0100] In one embodiment, along the winding direction of the first pole piece 100, from the inner side of the battery cell to the outer side of the battery cell, the total area of the through-holes 140 at different arc segment 151 positions gradually increases.

[0101] Specifically, as the number of winding layers of the battery cell increases, along the winding direction of the first pole piece 100, from the inner side to the outer side of the battery cell, the area of the arc segment 151 continuously increases. Correspondingly, the total area of the through holes 140 on the arc segment 151 increases with the increase of the area of the arc segment 151, which can ensure the reflux effect of the electrolyte at different positions of the arc segment 151. Compared with the method of setting a relatively large total area of the through holes 140 at different positions of the arc segment 151, the powder loss of the first pole piece 100 caused by the setting of the through holes 140 can be reduced.

[0102] In one embodiment, as Figures 1 - 5 shown, the number of the first wire grooves 121 is multiple, and the multiple first wire grooves 121 define a first wire bonding area 170. Among them, each first wire groove 121 is located inside the first wire bonding area 170, and the edge of the first wire bonding area 170 is connected to the edge of the outermost first wire groove 121. Exemplarily, as Figure 3 and Figure 4 shown, the multiple first wire grooves 121 on the first wire bonding area 170 can be arranged in parallel at intervals. The extending direction of each first wire groove 121 can be parallel to the direction indicated by the X-axis or parallel to the direction indicated by the Y-axis. Alternatively, the extending directions of each first wire groove 121 can be inclined to the direction indicated by the X-axis and the direction indicated by the Y-axis respectively. In a possible implementation manner, the included angle between the extending direction of each first wire groove 121 and the direction indicated by the Y-axis is less than 15°, to prevent the edge powder loss of the first pole piece 100 in the Y direction. As Figure 5 shown, the multiple first wire grooves 121 on the first wire bonding area 170 can also form a mesh structure.

[0103] A plurality of through holes 140 are provided on the arc segment 151, and the plurality of through holes 140 on the arc segment 151 define a punching area 160.

[0104] There is a first distance d between the first wire bonding area 170 and the adjacent punching area 160, and the first distance d is greater than or equal to 1 mm. Among them, the first distance d is the distance between the first wire groove 121 adjacent to the first area 131 and the through hole 140 adjacent to the second area 132. For example, the size of the first distance d can be 1 mm, 1.5 mm, 2 mm, etc., and it is not uniquely limited here.

[0105] Through the above settings, it is possible to avoid the overlap of the first wire bonding area 170 and the punching area 160, resulting in too little active material in the overlapping area of the first active material layer, so that the local CB value of the battery in the overlapping area is too small, leading to lithium plating.

[0106] In a specific embodiment, as Figure 6As shown, there is a second spacing between one end of the second region 132 far from the first region 131 and the first wire bonding area 170. Exemplarily, the extending direction of the first wire groove 121 can be parallel to the direction indicated by the Y-axis. The wire bonding starting point of the first wire groove 121 starts from the second region 132, and there is a second spacing between the wire bonding starting point and one end of the second region 132 far from the first region 131. The above second spacing can play a role in reducing edge powder loss.

[0107] The second spacing is d1, and d1 satisfies: 3mm ≤ d1 ≤ 10mm. For example, the size of d1 can be 3mm, 5mm, 8mm, 10mm, etc., and is not uniquely limited here. When d1 < 3mm, it may be due to processing tolerance that the end of the first wire groove 121 extends to the edge of the second region 132 far from the first region 131, making the first pole piece 100 prone to edge powder loss; when d1 > 10mm, the length of the first wire groove 121 is smaller, the electrolyte stored in the first wire groove 121 is less, and the effect of the first wire groove 121 on increasing the wetting effect of the electrolyte on the first pole piece 100 is smaller. That is to say, the above setting can reliably reduce the edge powder loss of the first pole piece 100 and at the same time reliably increase the wetting effect of the electrolyte on the first pole piece 100.

[0108] As Figures 3 - 6 shown, one end of the first wire bonding area 170 facing the first region 131 extends to the edge where the second region 132 is connected to the first region 131. The above setting can ensure the length of the first wire groove 121 and ensure the wetting effect of the electrolyte on the first pole piece 100.

[0109] In a possible implementation, as Figures 3 - 6 shown, at least part of the first wire grooves 121 are arranged in parallel at intervals. The interval between two adjacent and parallel first wire grooves 121 is D3, and D3 satisfies: 300μm ≤ D3 ≤ 3000μm.

[0110] Exemplarily, the size of D3 can be 300μm, 500μm, 1000μm, 2000μm, 3000μm, etc., and is not uniquely limited here. When D3 is less than 300μm, the arrangement of the first wire grooves 121 is too dense, and the first active material layer 120 loses more active materials in the second region 132, which may cause lithium deposition in the second region 132 of the first pole piece 100; when D3 is greater than 3000μm, the improvement effect of multiple first wire grooves 121 of the first active material layer 120 on the wetting of the electrolyte in the second region 132 is smaller. That is to say, the above setting ensures that the first active material layer 120 does not damage too many active materials in the second region 132 and at the same time ensures the wetting effect of the electrolyte on the first active material layer 120 in the second region 132.

[0111] Preferably, 500μm ≤ D3 ≤ 2000μm, which further ensures that the first active material layer 120 will not damage too much active material in the second region 132 and further ensures the wetting effect of the electrolyte on the first active material layer 120 in the second region 132.

[0112] In a possible implementation, the width of the first wire groove 121 is D4, and D4 satisfies: 10μm ≤ D4 ≤ 200μm. Exemplarily, the width D4 of the first wire groove 121 can be 10μm, 50μm, 100μm, 150μm, 200μm, etc., and is not uniquely limited here. When the width D4 of the first wire groove 121 is less than 10μm, the width of the first wire groove 121 is relatively narrow, and the amount of electrolyte stored in the first wire groove 121 is small, so the improvement effect of the first wire groove 121 on the wetting of the electrolyte is small; when the width D4 of the first wire groove 121 is greater than 200μm, the width of the first wire groove 121 is relatively large, and the first active material layer 120 loses too much active material in the second region 132. The above settings ensure that the first active material layer 120 will not damage too much active material in the second region 132 and at the same time ensure the wetting effect of the electrolyte on the first active material layer 120 in the second region 132.

[0113] In a possible implementation, the ratio range of the depth of the first wire groove 121 to the thickness of the first active material layer 120 is 0.15 - 0.5.

[0114] Exemplarily, the ratio of the depth of the first wire groove 121 to the thickness of the first active material layer 120 can be 0.15, 0.2, 0.3, 0.4, 0.5, etc., and is not uniquely limited here. When the ratio of the depth of the first wire groove 121 to the thickness of the first active material layer 120 is less than 0.15, the improvement effect of the first wire groove 121 on the wetting of the electrolyte is small; when the ratio of the depth of the first wire groove 121 to the thickness of the first active material layer 120 is greater than 0.5, the setting of the first wire groove 121 is likely to cause powder shedding and damage to the first current collector 110. If the depth of the first wire groove 121 is too deep, it will also cause the first active material layer 120 to damage too much active material in the second region 132. That is, the above settings ensure the improvement effect of the first wire groove 121 on the wetting of the electrolyte and at the same time avoid powder shedding of the first electrode sheet 100 and damage to the first current collector 110 caused by the first wire groove 121.

[0115] In an embodiment, the total area of the through holes 140 on a single arc segment 151 in the first region 131 is m, and the area of the first wire grooves 121 on the arc segment 151 in the second region 132 is n, and m and n satisfy: 1:6 ≤ m:n ≤ 1:2.

[0116] Among them, the total area of the through holes 140 on the single arc segment 151 of the first region 131 is smaller than the area of the first wire grooves 121 on the arc segment 151 of the second region 132. This is mainly because the winding stress of the first pole piece 100 at the position of the second region 132 is relatively large, and the electrolyte is often extruded. The larger area of the first wire grooves 121 on the arc segment 151 can increase the retention amount of the electrolyte and enhance the wetting ability. In addition, the above setting can also prevent the area of the through holes 140 from being too large, so that during the winding process, fractures may occur at the position of the arc segment 151 of the second region 132 due to the winding stress.

[0117] For example, the ratio between m and n can be 1:6, 1:5, 1:4, 1:3 or 1:2, which is not uniquely defined here. When the ratio between m and n is less than 1:6, it indicates that the total area of the through holes 140 on the same arc segment 151 is too small or the area of the first wire grooves 121 on the arc segment 151 of the second region 132 is too large, and the improvement effect of the through holes 140 on the electrolyte reflux is small or the first active material layer 120 loses more active materials at the second region 132; when the ratio between m and n is greater than 1:2, it indicates that the total area of the through holes 140 on the same arc segment 151 is too large or the area of the first wire grooves 121 on the arc segment 151 of the second region 132 is too small, and fractures are likely to occur at the position of the arc segment 151 of the second region 132 or the improvement effect on the electrolyte wetting ability is small. That is to say, the above setting can ensure the improvement effect of the through holes 140 on the electrolyte reflux and wetting, the tensile strength of the first pole piece 100, and that the first active material layer 120 does not lose too many active materials.

[0118] In a possible implementation manner, at least one row of concave-convex structures is formed on the first pole piece 100 in the second region 132. Each row of concave-convex structures is arranged at intervals along the width direction of the first pole piece 100. A concave portion is formed on one side of the concave-convex structure in the thickness direction of the first pole piece 100, and a convex portion is formed on the other side of the concave-convex structure in the thickness direction of the first pole piece 100.

[0119] Among them, the thickness direction of the first pole piece 100 is the Figure 2 direction indicated by the Z axis in the [description]. The cross-sectional shape of each concave-convex structure can be a suitable shape such as a circle or a square. Schematically, the concave-convex structures can be formed on the first pole piece 100 by embossing. Specifically, a roller or a mold with a specific pattern can be used to press the second region 132 of the first pole piece 100, and the part of the first pole piece 100 corresponding to the pattern in the second region 132 is deformed relative to the main body part of the first pole piece 100 to form the concave-convex structures. Those skilled in the art can set the number of rows of the concave-convex structures and the specific number of each row of the concave-convex structures according to needs, which is not uniquely defined here.

[0120] In this embodiment, the concave portion formed by the concave-convex structure on one side of the electrode tab can be used to store the electrolyte. After the first electrode tab 100, the separator 300, and the second electrode tab 200 are stacked and wound to form an electrode core, the convex portion formed by the concave-convex structure on the other side of the electrode tab can form a micro-gap between the electrode tabs, and this micro-gap can also be used to store the electrolyte. Each row of the concave-convex structure can form a channel for the electrolyte to flow between the electrode tabs. The above reasons enable the concave-convex structure to increase the wetting of the first electrode tab 100 by the electrolyte. In addition, the concave-convex structure can reserve some space for the expansion of the first electrode tab 100, thereby alleviating the problem of the electrode core bulging.

[0121] It should be noted that after the first electrode tab 100, the separator 300, and the second electrode tab 200 are stacked and wound to form an electrode core, since the first electrode tab 100 is wound along the length direction, and each row of the concave-convex structure is arranged along the width direction of the first electrode tab 100, it is more conducive to the flow of the electrolyte in the channels defined by each row of the concave-convex structure to increase the wetting of the first electrode tab 100 by the electrolyte. If each row of the concave-convex structure is arranged along the length direction of the first electrode tab 100, the channels formed by each row of the concave-convex structure may be distorted, which is not conducive to the flow of the electrolyte. The arrangement of each row of the concave-convex structure along the width direction of the first electrode tab 100 ensures the uniformity of the interface contact and the electrolyte wetting, thereby improving the diffusion path of lithium ions.

[0122] In a specific embodiment, the concave-convex structure forms a concave portion on the side of the first active material layer 120 facing away from the first current collector 110, and the concave-convex structure forms a convex portion on the side of the first current collector 110 facing away from the first active material layer 120.

[0123] Specifically, the concave-convex structure in the second region 132 protrudes toward the side of the first current collector 110 facing away from the first active material layer 120. During the production of the first electrode tab 100, the roller or the mold can contact the side of the first active material layer 120 facing away from the first current collector 110 and press the first electrode tab 100 to form the concave-convex structure. The above setting can prevent the first current collector 110 from directly contacting the roller or the mold and being damaged, which is beneficial to ensuring the tensile strength of the first electrode tab 100 at the position of the second region 132.

[0124] Schematically, the depth of the concave portion is 5 μm - 50 μm. Among them, the height of the convex portion is comparable to the depth of the concave portion. For example, the depth of the concave portion can specifically be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm, etc., and there is no unique limitation here. When the depth of the concave portion is less than 5 μm, the amount of electrolyte stored by the first pole piece 100 through the provision of the concavo-convex structure is small, and the effect of enhancing the wetting of the first pole piece 100 by the electrolyte is small; when the depth of the concave portion is greater than 50 μm, the first pole piece 100 may be damaged due to the provision of the concavo-convex structure, and the first pole piece 100 is prone to stress fracture at the position of the second region 132. Through the above settings, the wetting effect of the electrolyte on the first pole piece 100 is reliably enhanced, and at the same time, the tensile strength of the first pole piece 100 at the position of the second region 132 is ensured.

[0125] Schematically, the distance between two adjacent concavo-convex structures is 50 μm - 5000 μm. For example, the distance between two adjacent concavo-convex structures can be 50 μm, 500 μm, 1000 μm, 2000 μm, 4000 μm, or 5000 μm, etc., and there is no unique limitation here. When the distance between two adjacent concavo-convex structures is less than 50 μm, the first pole piece 100 may be damaged, and the first pole piece 100 is prone to stress fracture at the position of the second region 132; when the distance between two adjacent concavo-convex structures is greater than 5000 μm, the effect of enhancing the wetting of the first pole piece 100 by the electrolyte is small. The above settings reliably enhance the wetting effect of the electrolyte on the first pole piece 100 and at the same time make the first pole piece 100 not easily undergo stress fracture at the position of the second region 132.

[0126] In one embodiment, as Figure 7 shown, along the width direction of the first pole piece 100, the edge of the first pole piece 100 has a second wire bonding area 180. Among them, the second wire bonding area 180 can be provided only on one side edge of the first pole piece 100 or the second wire bonding area 180 can be provided on both side edges of the first pole piece 100 respectively. The length direction of the second wire bonding area 180 can extend along the length direction of the first pole piece 100.

[0127] The first active material layer 120 is provided with a plurality of second groove lines 122 on the second wire bonding area 180. The second groove lines 122 are located on the side of the first active material layer 120 facing away from the first current collector 110, and the depth of the second groove lines 122 is less than the thickness of the first active material layer 120. Among them, the second groove lines 122 can also be provided on the first active material layer 120 by laser scribing, and the setting of the second groove lines 122 will not cause damage to the first current collector 110. The plurality of second groove lines 122 on the second wire bonding area 180 can be arranged in parallel at intervals, and the extending direction of the second groove lines 122 can be parallel to the direction indicated by the X-axis or parallel to the direction indicated by the Y-axis. Or, the extending directions of the second groove lines 122 can be inclined to the direction indicated by the X-axis and the direction indicated by the Y-axis respectively. The extending direction of the second groove lines 122 can be the same as or different from the extending direction of the first groove lines 121.

[0128] Those skilled in the art can understand that there will be a problem of edge lithium deposition at the edges of the first electrode tab 100 in the width direction, especially in the area near the tab position, where the current density is relatively large and edge lithium deposition is more likely to occur. In this embodiment, the plurality of second groove lines 122 on the second wire bonding area 180 of the first electrode tab 100 can play a role in storing the electrolyte and increasing the wetting of the edge portion of the first electrode tab 100 in the width direction by the electrolyte.

[0129] As Figure 7 shown, the interval between two adjacent second groove lines 122 is D5, and D5 satisfies: 500μm ≤ D5 ≤ 2000μm.

[0130] Exemplarily, the size of D5 can be 500μm, 1000μm, 1500μm or 2000μm, etc., and is not uniquely limited here. When D5 is less than 500μm, the arrangement of the second groove lines 122 is too dense, and the first active material layer 120 loses more active material at the edges in the width direction, which may cause edge lithium deposition on the first electrode tab 100; when D5 is greater than 2000μm, the arrangement of the second groove lines 122 is too sparse, and the improvement effect of the plurality of second groove lines 122 on electrolyte wetting is small. That is to say, the above settings can not only ensure that the first active material layer 120 does not lose too much active material at the edges in the width direction, but also ensure the improvement effect of the plurality of second groove lines 122 on electrolyte wetting.

[0131] As Figure 7As shown, the width of the second groove 122 is D6, and D6 satisfies: 10 μm ≤ D6 ≤ 200 μm. Exemplarily, the width D6 of the second groove 122 can be 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, etc., which is not uniquely limited herein. The above setting ensures that the edges of the first active material layer 120 in the width direction will not damage too much active material, and at the same time ensures the improvement effect of the plurality of second grooves 122 on the electrolyte infiltration.

[0132] In a possible implementation manner, the ratio range of the depth of the second groove 122 to the thickness of the first active material layer 120 is 0.15 - 0.6. Exemplarily, the ratio of the depth of the second groove 122 to the thickness of the first active material layer 120 can be 0.15, 0.3, 0.4, 0.5, 0.6, etc., which is not uniquely limited herein. The above setting ensures the improvement effect of the second groove 122 on the electrolyte infiltration, and at the same time avoids the powder falling of the first electrode sheet 100 and the damage of the first current collector 110 caused by the second groove 122.

[0133] In a possible implementation manner, the size D7 of the second wire bonding area 180 in the width direction of the first electrode sheet 100 is 10 mm - 35 mm. Exemplarily, D7 can be 10 mm, 15 mm, 20 mm, 35 mm, etc., which is not uniquely limited herein. When D7 is less than 10 mm, the width of the second wire bonding area 180 is small, and lithium deposition may occur at the edge position of the first electrode sheet 100 in the second wire bonding area 180; when D7 is greater than 35 mm, the plurality of second grooves 122 on the second wire bonding area 180 will cause the first active material layer 120 to lose too much active material. That is, the above setting ensures that the first electrode sheet 100 will not have lithium deposition at the edge position of the second wire bonding area 180, and at the same time avoids the first active material layer 120 from losing too much active material.

[0134] This application also provides a battery, including the above-mentioned battery cell. For the battery provided by this application, due to the use of the above-mentioned battery cell, the internal resistance and expansion rate of the battery are low, and the safety and service life are high.

[0135] Hereinafter, the battery cell and battery provided by this application will be introduced in detail through specific embodiments, and the specific differences of the following batteries are shown in Table 1.

[0136] Example 1

[0137] The preparation of the battery in this example includes the following steps:

[0138] 1. Preparation of the positive electrode sheet:

[0139] Lithium cobaltate, a conductive agent (a mixture of conductive carbon black and carbon nanotubes), and PVDF (polyvinylidene fluoride) are placed in NMP (N-methylpyrrolidone) according to a mass ratio of 98.20:1:0.8, and stirred evenly to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on both the front and back sides of an aluminum foil with a thickness of 10 μm, and is successively dried, roll-pressed, and slit to obtain a positive electrode sheet. The positive electrode slurry forms a positive electrode active material layer with a thickness of 45 μm.

[0140] 2. Preparation of the negative electrode sheet:

[0141] Artificial graphite (graphite doped with 10% silicon carbide), conductive carbon black, and a binder are placed in deionized water according to a mass ratio of 96.1:0.5:5.4, and stirred evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on a copper foil with a thickness of 10 μm, and is successively dried, roll-pressed, and slit to obtain a negative electrode sheet. The negative electrode slurry forms a negative electrode active material layer with a thickness of 50 μm. The negative electrode sheet includes a first region 131 where negative electrode active material layers are respectively provided on both sides of the copper foil and a second region 132 where a negative electrode active material layer is provided only on one side of the copper foil.

[0142] Determine the position of the arc segment 151 of the second region 132 after the negative electrode sheet is wound, and a plurality of through holes 140 are provided at the position of the arc segment 151 of the first region 131 by means of laser drilling. The large-diameter end aperture D1 of each through hole 140 is 100 μm, the small-diameter end aperture is one-half of the large-diameter end aperture D1, and the distance D2 between two adjacent through holes 140 on the same arc segment 151 is 1000 μm.

[0143] The negative electrode sheet is provided with a plurality of wire grooves in the part of the negative electrode active material layer located in the second region 132 by means of laser scribing. Each wire groove extends along the length direction of the negative electrode sheet, and the part of the negative electrode active material layer located in the second region 132 is a wire-drawing area. The interval D3 between two adjacent wire grooves is 1000 μm, and the width D4 of the wire groove is 100 μm. The depth of the wire groove is 15 μm, and the ratio of the depth of the wire groove to the thickness of the negative electrode active material layer is 0.3.

[0144] 3. Preparation of the separator 300:

[0145] The separator 300 adopts a substrate + ceramic + coated separator 300, and the thickness of the separator 300 is 6.5 μm.

[0146] 4. Assembly:

[0147] The above-mentioned slit and fabricated positive electrode sheet, negative electrode sheet and separator 300 are wound into a wound-type structure battery cell, and after processes such as hot pressing, encapsulation, liquid injection, formation, and secondary sealing are performed on the battery cell, a lithium-ion battery is obtained. Among them, the electrolyte includes a lithium salt LiPF6 and a solvent, and the solvent includes ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), and the molar ratio of the three is DEC:EC:EMC = 1:1:1. The electrolyte also includes 1,3-propane sultone, and the content range of 1,3-propane sultone is 5%.

[0148] Examples 2 to 12

[0149] The difference from Example 1 lies in that conditions such as the large-end aperture D1 and the distance D2 between two adjacent through holes 140 on the same arc segment 151 are different. Specifically, see Table 1. Except for the differences shown in Table 1, the remaining conditions are the same as those in Example 1.

[0150] Examples 13 to 26

[0151] The difference from Example 13 lies in that conditions such as the interval D3 between two adjacent wire grooves, the width D4 of the wire groove, the depth of the wire groove, and the ratio between the depth of the wire groove and the thickness of the negative active material layer are different. Specifically, see Table 1. Except for the differences shown in Table 1, the remaining conditions are the same as those in Example 13.

[0152] Comparative Example 1

[0153] The difference from Example 1 lies in that no through hole 140 is provided at the position of the arc segment 151 of the negative electrode sheet.

[0154] Comparative Example 2

[0155] The difference from Example 1 lies in that no wire groove is provided in the part of the negative active material layer located in the second region 132.

[0156] Comparative Example 3

[0157] The difference from Example 1 lies in that no through hole 140 is provided at the position of the arc segment 151 of the negative electrode sheet, and no wire groove is provided in the part of the negative active material layer located in the second region 132.

[0158] Table 1:

[0159]

[0160]

[0161]

[0162] The relevant performances of the batteries in the above examples and comparative examples were tested, and the test results were recorded in Table 3. The test method is as follows:

[0163] 1. Capacity Test: Discharge the battery at 0.2C until the lower limit voltage of 3.0V, then let it stand for 10 minutes. After that, charge it at 1C until the upper limit voltage of 4.55V, with a cut-off current of 0.05C. At this time, the battery is in a fully charged state. Then discharge the battery at 0.2C until the lower limit voltage of 3.0V. The capacity discharged at this time is the battery capacity.

[0164] 2. Internal Resistance Test: Charge the lithium-ion battery to 50% SOC at 25°C, and use an internal resistance tester to measure the internal resistance of the battery.

[0165] 3. Capacity Retention Rate Test: At 25°C, charge the battery at a constant current of 1C to 4.45V, then charge it at a constant voltage until the cut-off current of 0.05C, let it stand for 5 minutes, and discharge it at a constant current of 1C to 3.0V. This is the first cycle. Repeat the above process 600 times. Calculate the capacity retention rate according to the formula: Capacity Retention Rate (%) after 600 cycles of the battery = Discharge capacity after 600 cycles / Discharge capacity after the first cycle × 100%.

[0166] 4. Swelling Rate Test: Record the initial thickness of the battery at 50% SOC before the cycle as P1. After 600 cycles, record the thickness of the battery at 100% SOC as P2. Then the swelling rate = (P2 - P1) / P1 × 100%.

[0167] 5. Lithium Deposition Test: After 400 cycles of the batteries obtained in the above examples and comparative examples respectively, fully charge the batteries obtained in the above examples and comparative examples respectively, disassemble the batteries in the environment of a drying room, and observe the lithium deposition situation of the negative electrode sheets.

[0168] 6. Tensile Strength Test of Negative Electrode Sheet: Use a vertical tensile machine for testing. Fix the negative electrode sheets obtained in the above examples and comparative examples on the clamps at both ends of the tensile machine, align the two ends of the clamps, start the button of the tensile device, and the device moves at a speed of 10 mm / s until the negative electrode sheet breaks, and read out the tensile force data.

[0169] Table 2

[0170]

[0171]

[0172] Compared with Comparative Example 1 and Comparative Example 3, in Examples 1 to 26, both the internal resistance and cycle performance of the battery are improved, the cycle expansion is reduced, and the lithium plating is significantly improved. It shows that setting a plurality of through holes 140 at the arc segment 151 position of the first region 131 of the negative electrode sheet can promote the reflux of the electrolyte, which is beneficial to improving the internal resistance and cycle performance of the battery. Lithium plating is not likely to occur at the arc segment 151 position of the first region 131 of the negative electrode sheet and at the inner fold of the battery cell. The through holes 140 reserve space for the expansion of the electrode sheet, which is beneficial to alleviating the expansion of the battery cell. Compared with Comparative Example 2 and Comparative Example 3, in Examples 1 to 26, both the internal resistance and cycle performance of the battery are improved, the cycle expansion is reduced, indicating that setting a plurality of wire grooves in the part of the negative electrode active material layer located in the second region 132 of the negative electrode sheet is beneficial to the infiltration of the electrolyte, which is beneficial to improving the internal resistance and cycle performance of the battery, and the lithium plating situation is improved. Lithium plating is not likely to occur at the inner fold of the negative electrode sheet in the battery cell. The wire grooves reserve space for the expansion of the electrode sheet, which is beneficial to alleviating the expansion of the battery cell.

[0173] Further, compared with Example 2 and Example 6, in Example 1 and Examples 3 to 5, by controlling the major diameter end D1 of the through hole 140 within the range of 30 μm to 200 μm, both the tensile strength of the negative electrode sheet can be ensured and the reflux effect of the electrolyte at the position of the through hole 140 can be ensured. Compared with Example 5, in Example 1, Example 3 and Example 4, by controlling the major diameter end D1 of the through hole 140 within the range of 30 μm to 180 μm, the tensile strength of the negative electrode sheet can be further ensured.

[0174] Further, compared with Example 7 and Example 12, in Example 1 and Examples 8 to 11, by controlling the distance D2 between two adjacent through holes 140 within the range of 100 μm to 5000 μm, both the tensile strength of the negative electrode sheet can be ensured and the reflux effect of the electrolyte at the position of the through hole 140 can be ensured. Compared with Example 8 and Example 11, in Example 1, Example 9 and Example 10, by controlling the distance D2 between two adjacent through holes 140 within the range of 200 μm to 1500 μm, the tensile strength of the negative electrode sheet can be further ensured and the reflux effect of the electrolyte at the position of the through hole 140 can be further ensured.

[0175] Further, compared with Embodiment 13 and Embodiment 18, in Embodiment 1 and Embodiments 14-17, by controlling the interval D3 between two adjacent wire grooves within the range of 300 μm - 3000 μm, it is ensured that the negative active material layer in the second region 132 will not damage too much active material, and at the same time, the wetting effect of the electrolyte on the negative active material layer in the second region 132 is ensured. Compared with Embodiment 14 and Embodiment 17, in Embodiment 1, Embodiment 15 and Embodiment 16, by controlling the interval D3 between two adjacent wire grooves within the range of 500 μm - 2000 μm, it can be further ensured that the negative active material layer in the second region 132 will not damage too much active material, and at the same time, the wetting effect of the electrolyte on the negative active material layer in the second region 132 is ensured.

[0176] Further, compared with Embodiment 19 and Embodiment 22, in Embodiment 1, Embodiment 20 and Embodiment 21, by controlling the width D4 of the wire groove within the range of 10 μm - 200 μm, it is ensured that the negative active material layer in the second region 132 will not damage too much active material, and at the same time, the wetting effect of the electrolyte on the negative active material layer in the second region 132 is ensured.

[0177] Further, compared with Embodiment 23 and Embodiment 26, in Embodiment 1, Embodiment 24 and Embodiment 25, by controlling the ratio of the depth of the wire groove to the thickness of the negative active material layer on this side within the range of 0.15 - 0.5, it is ensured that the first wire groove 121 has an improved effect on the wetting of the electrolyte, and at the same time, it is avoided that the first wire groove 121 causes powder falling off of the negative electrode sheet and damage to the copper foil.

[0178] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery cell, characterized in that, The battery cell comprises a first pole piece, a second pole piece and a diaphragm located between the first pole piece and the second pole piece, wherein the first pole piece, the diaphragm and the second pole piece are stacked and wound to form the battery cell; The first pole piece includes a first current collector and a first active material layer located on both sides of the first current collector; the first active material layer includes a silicon-carbon composite material; The first pole sheet comprises a first region where the first active material layer is respectively arranged on both sides of the first current collector and a second region where the first active material layer is arranged only on one side of the first current collector, and the second region is located on a side of the first region facing the inside of the battery cell; the first pole sheet has an arc segment located at the end of the battery cell and a straight segment located in the middle of the battery cell in both the first region and the second region; A through hole penetrating the first pole piece is provided on the arc segment of the first region, and the through hole avoids the second region; The first active material layer is provided with a first wire groove on the second region, the first wire groove is located on a side of the first active material layer away from the first current collector, and the depth of the first wire groove is less than the thickness of the first active material layer; The battery cell includes an electrolyte, the electrolyte includes a sulfur-containing additive, the sulfur-containing additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone or vinyl sulfate, and the content of the sulfur-containing additive ranges from 0.1% to 6%; The small diameter end of the through hole faces the inner side of the battery core, and the large diameter end of the through hole faces the outer side of the battery core; The aperture of the large warp end is D1, and D1 satisfies: 30μm≤D1≤200μm.

2. The battery cell according to claim 1, wherein, Along the winding direction of the first pole piece, there is a gap between the edge where the first region and the second region meet and the through hole.

3. The battery cell according to claim 2, wherein, The first pole piece has a plurality of arc segments in the first region; Among the plurality of arc segments of the first pole piece in the first region, the through hole avoids the arc segment adjacent to the second region.

4. The battery cell according to claim 1, characterized in that, The first pole piece is provided with a plurality of through holes on the arc segment of the first region; Among the plurality of through holes on the same arc segment, the distance between two adjacent through holes is D2, and D2 satisfies: 100 μm ≤ D2 ≤ 5000 μm; and / or, The first pole piece is provided with a plurality of through holes on the arc segment of the first region, and the plurality of through holes on the arc segment define a perforated area; Along the winding direction of the first pole piece, the size of the arc segment is less than or equal to the size of the corresponding punching area; and / or, Along the winding direction of the first pole piece, from the inner side of the battery core to the outer side of the battery core, the total area of the through holes at different arc segment positions gradually increases.

5. The battery cell according to claim 1, characterized in that, There are multiple first wire slots, and the multiple first wire slots define a first wiring area; A plurality of through holes are provided on the arc segment, and the plurality of through holes on the arc segment define a punching area; There is a first distance between the first wiring area and the adjacent punching area, and the first distance is greater than or equal to 1 mm.

6. The battery cell according to claim 5, wherein One end of the second region far from the first region has a second spacing from the first wire bonding region, the second spacing is d1, and d1 satisfies: 3 mm ≤ d1 ≤ 10 mm; and / or, One end of the first wire bonding region extending towards the first region extends to the edge where the second region and the first region are joined; and / or, At least some of the first wire grooves are arranged in parallel at intervals, and the interval between two adjacent and parallel first wire grooves is D3, and D3 satisfies: 300 μm ≤ D3 ≤ 3000 μm; and / or, The width of the first wire groove is D4, and D4 satisfies: 10 μm ≤ D4 ≤ 200 μm; and / or, The ratio range between the depth of the first wire groove and the thickness of the first active material layer is 0.15 - 0.

5.

7. The battery cell according to any one of claims 1-6, characterized in that, The first pole piece forms at least one row of concave and convex structures on the second region, and each row of the concave and convex structures is arranged at intervals along the width direction of the first pole piece. A concave portion is formed on one side of the concave and convex structure in the thickness direction of the first pole piece, and a convex portion is formed on the other side of the concave and convex structure in the thickness direction of the first pole piece.

8. The battery cell according to any one of claims 1-6, characterized in that, Along the width direction of the first pole piece, the edge of the first pole piece has a second wire bonding region. A plurality of second wire grooves are arranged on the first active material layer in the second wire bonding region. The second wire grooves are located on the side of the first active material layer facing away from the first current collector, and the depth of the second wire grooves is less than the thickness of the first active material layer.

9. The battery cell according to claim 8, wherein The interval between two adjacent second wire grooves is D5, and D5 satisfies: 500 μm ≤ D5 ≤ 2000 μm; and / or, The width of the second wire groove is D6, and D6 satisfies: 10 μm ≤ D6 ≤ 200 μm; and / or, The ratio range between the depth of the second wire groove and the thickness of the first active material layer is 0.15 - 0.6; and / or, The size of the second wire bonding region in the width direction of the first pole piece is 10 mm - 35 mm.

10. A battery, characterized in that, Including the battery cell according to any one of claims 1 - 9.

Images