Battery cell and lithium ion battery

Abstract

The utility model relates to the field of lithium ion batteries, and discloses a battery cell and a lithium ion battery, the battery cell comprises a first pole piece, a diaphragm and a second pole piece which are stacked, the first pole piece comprises a current collector and an active material layer arranged on the current collector, and the first pole piece has a first surface and a second surface which are oppositely arranged along a first direction, the first surface is the surface of one side, close to the center of the battery cell, of the first pole piece, the second surface is the surface of one side, far away from the center of the battery cell, of the first pole piece, and at least one side surface of the first pole piece is provided with a non-concave area and a concave area comprising at least one concave part or groove; and in the first pole piece positioned on the outermost side of the battery cell, the length of the concave area of the active material layer positioned on the second surface along the second direction is smaller than that of the concave area of the active material layer positioned on the first surface. The non-sunken area is arranged on the first pole piece on the outermost side of the battery cell and on the second surface far away from the battery cell, the strength of a substance layer in the non-sunken area is higher, the capability of bearing external stress is enhanced, and the quality of the battery cell is improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a battery cell and a lithium-ion battery. Background Technology

[0002] A lithium-ion battery is a rechargeable battery that works by the movement of lithium ions between the positive and negative electrodes. During charging, lithium ions move from the positive electrode to the negative electrode, and during discharging, lithium ions move from the negative electrode to the positive electrode. Lithium-ion batteries are widely used in electronic products, automobiles, and other fields.

[0003] To improve lithium plating during battery cycling, laser wire bonding can be used to create lines in the active material layer of the electrode. This helps lithium ions diffuse rapidly within the electrode, reduces polarization, effectively suppresses lithium plating, and improves battery cycle performance. However, laser wire bonding also brings certain problems. After laser bonding, the surface structure of the electrode becomes more porous, and the electrode strength decreases. Under localized external forces, the stressed areas of the electrode may experience damage or collapse.

[0004] Therefore, how to solve the above-mentioned technical problems should be a key focus for those skilled in the art. Utility Model Content

[0005] The purpose of this application is to provide a cell and a lithium-ion battery to improve the strength of the electrode sheets.

[0006] To address the aforementioned technical problems, this application provides a battery cell, comprising: a first electrode, a separator, and a second electrode stacked together, wherein the first electrode includes a current collector and an active material layer disposed on the current collector.

[0007] Along a first direction, the first electrode has a first surface and a second surface disposed opposite to each other. The first surface is the surface of the first electrode close to the center of the battery cell, and the second surface is the surface of the first electrode away from the center of the battery cell. At least one side surface of the first electrode is provided with a non-recessed area and a recessed area including at least one recess or groove. At least a portion of the recessed area and the non-recessed area are disposed adjacent to each other along a second direction.

[0008] In the first electrode plate located on the outermost side of the battery cell, the length of the recessed area of ​​the active material layer on the second surface along the second direction is less than the length of the recessed area of ​​the active material layer on the first surface; the second direction is perpendicular to the first direction.

[0009] Optionally, the battery cell is a laminated battery cell, which includes at least two first electrodes stacked together, wherein the outermost first electrode is the electrode that is furthest from the center of the battery cell in the thickness direction.

[0010] Optionally, the battery cell is a wound battery cell.

[0011] Optionally, the battery cell includes a flat section and an arc section connected to the flat section. In the first electrode located on the outermost side of the battery cell, the length of the non-recessed area of ​​the active material layer on the second surface along the second direction is greater than the length of the non-recessed area of ​​the active material layer on the first surface along the second direction.

[0012] The first electrode located on the outermost side of the battery cell is formed from the winding end of the first electrode in the battery cell along a direction opposite to the winding direction, with the first straight area located in the straight section of the battery cell and the first arc area located in the arc section of the battery cell.

[0013] Optionally, the tail region of the first electrode includes the first to sixth half turns starting from the winding end of the first electrode of the battery cell, along the direction opposite to the winding direction of the wound battery cell, with each half turn including a straight area and an arc area.

[0014] Optionally, along the winding direction of the first electrode, the distance between the starting side of the recessed area on the first surface of the first electrode and the starting side of the active material layer on the first surface of the first electrode is greater than 2 mm along the winding direction of the first electrode.

[0015] And / or, along the winding direction of the battery cell, the distance between the starting side of the recessed area on the second surface of the first electrode and the starting side of the active material layer on the second surface of the first electrode is greater than 2 mm along the winding direction of the first electrode.

[0016] Optionally, in the third direction, the first electrode includes a first edge region and a second edge region; the first edge region is an edge region close to the tab, and the second edge region is an edge region away from the tab, and the second direction is perpendicular to the third direction.

[0017] The dimension of the recessed area along the third direction is less than or equal to the dimension of the first electrode along the third direction.

[0018] Optionally, in the third direction, the area between the side edge of the recessed area near the first edge area and the end of the first edge area is set as a non-recessed area, and the size of the non-recessed area near the first edge area is E1, which satisfies: 0.05 mm ≤ E1 ≤ 10 mm;

[0019] And / or,

[0020] In the three directions, the area between the edge of the recessed region near the second edge region and the end of the second edge region is set as a non-recessed region. The size of the non-recessed region near the second edge region is E2, which satisfies: 0.05 mm ≤ E2 ≤ 10 mm; the second direction and the third direction are perpendicular to each other.

[0021] Optionally, along the third direction, the dimension by which the edge of the first electrode near the first edge region extends beyond the edge of the second electrode constitutes a first overhang region; along the third direction, the dimension E1 of the non-recessed region near the first edge region is greater than or equal to the dimension of the first overhang region along the second direction; and / or,

[0022] Along the third direction, the edge of the first electrode near the second edge region extends beyond the edge of the second electrode region by a dimension that constitutes the second overhang region. Along the third direction, the dimension E2 of the non-recessed region near the second edge region is greater than or equal to the dimension of the second overhang region along the third direction.

[0023] Optionally, in the first electrode located on the outermost side of the battery cell, the length of the non-recessed region of the active material layer on the second surface of the first electrode located along the second direction ranges from 20 mm to 1000 mm; and / or,

[0024] The length of the non-recessed area of ​​the active material layer on the first surface of the first electrode along the second direction ranges from 2 mm to 1000 mm.

[0025] Optionally, the depth of each recess or groove in the recessed area along the first direction ranges from 10 μm to 30 μm; and / or,

[0026] The spacing between adjacent recesses or grooves along the second direction ranges from 0.2 mm to 10 mm; and / or,

[0027] The width of the recess or groove along the second direction ranges from 30μm to 250μm.

[0028] This application also provides a lithium-ion battery, including any of the cells described above.

[0029] This application provides a recessed area and a non-recessed area on at least one side surface of the first electrode of the battery cell.

[0030] After the electrode surface is recessed, the surface structure becomes more porous. This makes the electrode structure more prone to collapse under external stress or impact, leading to unevenness and other defects in the cell's appearance. Repairing cells with poor appearance can cause electrode powder to fall off, resulting in micro-open circuits or lithium plating problems. In this application, on the outermost first electrode, the length of the recessed area on the second surface of the active material layer is shorter than the length of the recessed area on the first surface; that is, the length of the non-recessed area on the second surface of the active material layer is longer. Furthermore, since the second surface of the first electrode is the surface of the first electrode away from the center of the cell, by reducing the length of the recessed area on the second surface of the outermost first electrode of the cell, on the one hand, the ability of the outermost electrode of the cell to withstand external stress can be improved, reducing the likelihood of powder shedding and collapse of the outer electrode under external force, thus improving the appearance quality of the cell and reducing powder shedding and lithium plating problems. On the other hand, during battery cycling, the surface of the electrode near the cell accumulates more heat, and setting a larger recessed area on the first surface of the first electrode near the outermost first electrode of the cell is equivalent to constructing a heat dissipation channel. This design helps to dissipate the heat generated during charging and discharging in a timely manner, reducing the risk of localized heat accumulation on the surface of the first electrode near the cell. Simultaneously, recessed areas are provided on both sides of the outermost first electrode of the cell, and along the second direction, the length of the recessed area on the first surface of the outermost first electrode is relatively large. This enhances the battery's electrolyte storage capacity and electrolyte flow during cycling, helping lithium ions diffuse rapidly within the first electrode, reducing voltage drop caused by lithium ion accumulation on the first electrode surface, lowering the risk of lithium plating, and improving the stability and reliability of the battery during charging and discharging.

[0031] In addition, this application also provides a lithium-ion battery with the above-mentioned advantages. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A schematic diagram of a wound battery cell provided in an embodiment of this application;

[0034] Figure 2 A schematic diagram of a stacked battery cell provided in an embodiment of this application;

[0035] Figure 3 A schematic cross-sectional view of a first electrode provided in an embodiment of this application;

[0036] Figure 4 Top view of the second surface of the first type of first electrode provided in the embodiments of this application. Figure 1 ;

[0037] Figure 5 Top view of the second surface of the second type of first electrode provided in the embodiments of this application. Figure 1 ;

[0038] Figure 6 Top view of the second surface of the third type of first electrode provided in the embodiments of this application. Figure 1 ;

[0039] Figure 7 Top view of the second surface of the first type of first electrode provided in the embodiments of this application. Figure 2 ;

[0040] Figure 8 Top view of the second surface of the second type of first electrode provided in the embodiments of this application. Figure 2 ;

[0041] Figure 9 Top view of the second surface of the third type of first electrode provided in the embodiments of this application. Figure 2 ;

[0042] Figure 10 Top view of the second surface of the first type of first electrode provided in the embodiments of this application. Figure 3 ;

[0043] Figure 11 Top view of the second surface of the second type of first electrode provided in the embodiments of this application. Figure 3 ;

[0044] Figure 12 Top view of the second surface of the third type of first electrode provided in the embodiments of this application. Figure 3 ;

[0045] Figure 13 Top view of the first surface of the first electrode provided in the embodiments of this application. Figure 1 ;

[0046] Figure 14 Top view of the first surface of the first electrode provided in the embodiments of this application. Figure 2 ;

[0047] In the figure, 100 is the first electrode, 200 is the second electrode, 300 is the diaphragm, 1 is the current collector, 2 is the active material layer, 3 is the tab, 11 is the tab groove, 21 is the recessed area, 22 is the non-recessed area, and 211 is the groove. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0049] Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0050] As described in the background section, laser wire bonding is currently used to bond all the active material layers on the electrode to suppress lithium plating. However, laser wire bonding also makes the surface structure of the electrode loose, which reduces the strength of the electrode. Under local external force, the stressed area of ​​the electrode may be damaged or collapse.

[0051] In view of this, this application provides a battery cell, please refer to... Figures 1 to 3 It can include:

[0052] A first electrode 100, a diaphragm 300, and a second electrode 200 are stacked together. The first electrode 100 includes a current collector 1 and an active material layer 2 disposed on the current collector 1.

[0053] Along the first direction, the first electrode 100 has a first surface and a second surface disposed opposite to each other. The first surface is the surface of the first electrode 100 close to the center of the cell, and the second surface is the surface of the first electrode 100 away from the center of the cell. At least one side surface of the first electrode 100 is provided with a non-recessed area 22 and a recessed area 21 including at least one recess or groove 211. At least a portion of the recessed area 21 and the non-recessed area 22 are disposed adjacent to each other along the second direction Y.

[0054] In the first electrode 100 located on the outermost side of the battery cell, the length of the recessed area 21 of the active material layer 2 on the second surface along the second direction Y is less than the length of the recessed area 21 of the active material layer 2 on the first surface; the second direction Y is perpendicular to the first direction Z.

[0055] It should be noted that the first direction refers to the direction of the thickness of the first electrode 100, for example... Figure 3 The Z direction is the first direction, and the second direction is the length direction of the first electrode 100, for example... Figure 3The Y direction is defined as the direction of width of the first electrode 100; the third direction is defined as the direction of width of the first electrode 100, for example... Figure 4 The X direction is defined in the diagram. The first direction Z, the second direction Y, and the third direction X are perpendicular to each other. It should be further noted that the length of the first electrode 100 is greater than its width, which is also greater than its thickness.

[0056] The first electrode 100 can be a negative electrode, and the second electrode 200 can be a positive electrode. Alternatively, the first electrode 100 can be a positive electrode, and the second electrode 200 can be a negative electrode.

[0057] For the negative electrode sheet, the negative electrode current collector can be copper foil, and the material of the negative electrode active material layer can be carbon material, such as natural graphite, artificial graphite, modified graphite, soft carbon, hard carbon, etc., or it can be non-carbon material, such as tin-based material, silicon-based material, etc., which is not limited in this embodiment.

[0058] For the positive electrode sheet, the positive current collector can be aluminum foil, and the material of the positive active material layer can be lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate, etc., which are not limited in this embodiment.

[0059] In the first electrode 100, a recessed area 21 and a non-recessed area 22 can be provided on both the first and second surfaces; or, a recessed area 21 and a non-recessed area 22 can be provided on the second surface, while only a recessed area 21 can be provided on the first surface.

[0060] The recessed area 21, or groove 211, can be formed by laser, scraper, or other mechanical means. The groove 211 can be linear and extends along a third direction X. The non-recessed area 22 does not have grooves 211 or recesses, that is, the active material layer 2 in the non-recessed area 22 is intact.

[0061] The "recessed area" mentioned in this application refers to a portion of the surface of the active material layer 2 coated on the side of the current collector 1 where holes or grooves are formed, reducing the amount of active material in that area. In other words, grooves and / or holes are formed in a portion of the surface of the active material layer 2, and obvious groove and / or hole structures can be observed on the surface of the first electrode 100 after disassembling the battery cell. The "non-recessed area" mentioned in this application refers to a portion of the surface of the active material layer 2 after it has been coated on the side of the current collector 1, where no holes or lines are formed. It does not include grooves, holes, or other recessed structures formed by unevenness on the surface of the active material layer 2 due to material particle size, electrode flatness, etc., after coating, nor does it include microscopic recessed structures. It is understood that, taking electrodes with the same area of ​​recessed area 21 and non-recessed area 22, the electrode with the non-recessed area 22 will weigh more than the electrode with the recessed area 21.

[0062] It should be noted that this application does not limit the type of battery cell; it depends on the circumstances.

[0063] As one possible implementation, the battery cell is a stacked battery cell, which includes at least two first electrode plates 100 stacked together, and the first electrode plate 100 located on the outermost side of the battery cell is the electrode plate that is away from the center of the battery cell thickness direction.

[0064] When the cell is a laminated cell, the second direction Y is the direction of the length of the first electrode 100 and the length of the second electrode 200.

[0065] As another possible implementation, the battery cell is a wound battery cell. In this case, the outermost first electrode 100 of the battery cell refers to the first electrode 100 located on the outermost ring of the wound battery cell.

[0066] When the battery cell is a wound cell, the wound cell includes a straight section and an arc section. The direction of the length of the first electrode 100 and the second electrode 200 is the winding direction. The second direction Y is also the length direction of the first electrode 100 and the second electrode 200 within the straight section region.

[0067] For wound battery cells, at least a portion of the recessed region 21 and the non-recessed region 22 are arranged adjacent to each other along the second direction, that is, at least a portion of the recessed region 21 and the non-recessed region 22 are arranged adjacent to each other along the winding direction. The length of the recessed region 21 of the active material layer 2 on the second surface along the second direction is also the length of the recessed region 21 of the active material layer 2 on the second surface along the winding direction.

[0068] It should be noted that when the recessed area 21 includes multiple hole structures and / or multiple groove structures, the length of the recessed area 21 of the active material layer 2 on the outermost first surface and / or second surface of the battery cell along the second direction Y does not refer to the length of a single hole structure or a single groove structure in the recessed area 21 along the second direction Y, but rather to the size of the overall recessed area 21 composed of multiple hole structures and / or multiple groove structures on the outermost first electrode 100 of the battery cell.

[0069] It should be noted that in this embodiment, the depth and width of the recess or groove 211 in the recessed area 21, as well as the spacing between adjacent recesses or grooves 211, are not limited and can be set by the user.

[0070] As one possible implementation, the depth h of each recess or groove 211 in the recessed area 21 along the first direction Z ranges from 10μm to 30μm, so as to simultaneously satisfy that the cell made of the first electrode 100 has good electrolyte storage and electrolyte flow during the cycle, improve the dynamic performance of the battery, and meet the requirements of high-rate charging and discharging.

[0071] For example, the depth h of the recess or groove 211 can be 10μm, 15μm, 20μm, 25μm, 30μm, etc.

[0072] As one possible implementation, the distance b between adjacent recesses or grooves 211 along the second direction Y is in the range of 0.2mm to 10mm, so as to simultaneously meet the requirements of the cell dynamic performance of the first electrode 100 and meet the requirements of high-rate charging and discharging.

[0073] For wound cells, the spacing between adjacent recesses or grooves 211 along the second direction Y is also the spacing between adjacent recesses or grooves 211 along the winding direction.

[0074] For example, the spacing b between adjacent recesses or grooves 211 can be 0.2μm, 0.5μm, 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.8μm, etc.

[0075] As one possible implementation, the width a of the recess or groove 211 along the second direction Y is in the range of 30μm~250μm, so as to simultaneously meet the requirements of the cell dynamic performance of the first electrode 100 and meet the requirements of high-rate charging and discharging.

[0076] For example, the width a of the recess or groove 211 along the second direction Y can be 30μm, 50μm, 100μm, 150μm, 200μm, 250μm, etc.

[0077] In this embodiment, on the outermost first electrode 100 of the battery cell, the length of the recessed area 21 on the second surface of the active material layer 2 is shorter than the length of the recessed area 21 on the first surface of the active material layer 2. Therefore, the length of the non-recessed area 22 on the second surface of the active material layer 2 is longer, thus increasing the strength of the active material layer 2 on the second surface. Furthermore, since the second surface of the first electrode 100 is the surface of the first electrode 100 away from the center of the battery cell, reducing the length of the recessed area 21 on the second surface of the outermost first electrode 100 can, on the one hand, improve the ability of the outermost first electrode 100 to withstand external stress, reducing the likelihood of powder shedding and collapse of the outer electrode under external force, improving the appearance quality of the battery cell, and reducing powder shedding and black spot lithium plating problems. On the other hand, during battery cycling, the surface of the first electrode 100 near the battery cell accumulates more heat. Therefore, setting a larger recessed area 21 on the first surface of the first electrode 100 near the outermost first electrode 100 is sufficient. Constructing heat dissipation channels helps to dissipate the heat generated by the battery during charging and discharging in a timely manner, reducing the risk of local heat accumulation on the surface of the first electrode 100 near the cell. At the same time, recessed areas 21 are provided on both sides of the outermost first electrode 100 of the cell, and the length of the first surface recessed area 21 of the outermost first electrode 100 of the cell is relatively large along the second direction Y. This can improve the battery's electrolyte storage capacity and electrolyte flow during cycling, help lithium ions diffuse quickly in the electrode, reduce the voltage drop caused by the accumulation of lithium ions on the electrode surface, reduce the risk of lithium plating in the battery, and improve the stability and reliability of the battery during charging and discharging.

[0078] In one embodiment of this application, please refer to Figures 4 to 14 When the battery cell is a wound battery cell, the battery cell includes a straight section and an arc section connected to the straight section. In the first electrode 100 located on the outermost side of the battery cell, the length L1 of the non-recessed area 22 of the active material layer 2 on the second surface along the second direction Y is greater than the length L2 of the non-recessed area 22 of the active material layer 2 on the first surface along the second direction Y. The first electrode 100 located on the outermost side of the battery cell is a first straight area and a first arc area formed from the winding end of the first electrode 100 of the battery cell along the opposite direction to the winding direction of the wound battery cell. The first straight area is located in the straight section of the battery cell, and the first arc area is located in the arc section of the battery cell.

[0079] The first electrode 100 located on the outermost side of the battery cell may have a non-recessed area 22 on both its first and second surfaces, or a non-recessed area 22 may be provided only on the second surface.

[0080] In a wound battery cell, the outermost ring is most susceptible to damage from external forces. In this embodiment, by setting a non-recessed area 22 in the first flat area and the first arc area corresponding to the outermost first electrode 100, the strength of the first flat area and the first arc area can be improved, reducing the problem of damage and collapse after being subjected to external forces.

[0081] If the first electrode plate located on the outermost side of the cell is less than the first flat area and the first arc area, it cannot protect the cell. Therefore, it needs to include at least the first flat area and the first arc area.

[0082] Based on the above embodiments, in one embodiment of this application, the tail region of the first electrode 100 includes the first half-turn to the sixth half-turn starting from the winding end of the first electrode of the battery cell, along the direction opposite to the winding direction, and each half-turn L4 includes a straight area and an arc area.

[0083] In this embodiment, the tail region of the first electrode 100 includes a first straight region, a first arc region, a second straight region, a second arc region, a third straight region, a third arc region, a fourth straight region, a fourth arc region, a fifth straight region, a fifth arc region, a sixth straight region, and a sixth arc region, starting from the winding end and extending in the opposite direction to the winding direction. Each straight region is located within a straight section of the wound cell, and each arc region is located within an arc section of the wound cell. It should be noted that in the wound cell, the first electrode located on the outermost side of the cell is part of the tail region of the first electrode 100.

[0084] Non-recessed areas 22 are provided in the region corresponding to the first half-turn to the sixth half-turn of the first electrode 100. That is, non-recessed areas 22 are provided in the three layers from the outside to the inside of the wound cell. If non-recessed areas 22 are provided on more half-turns corresponding to the first electrode 100, the non-recessed areas 22 will be located in the inner layer of the cell. After being subjected to stress, the inner layers will be less affected, and the non-recessed areas 22 will have limited effect in resisting external forces. In addition, it will also reduce the length of the recessed areas 21, affecting the improvement of cell performance.

[0085] In one possible implementation, the tail region of the first electrode 100 includes the second to fourth half-turns along the direction opposite to the winding direction, starting from the winding end of the cell. Specifically, starting from the winding end of the first electrode 100, this extends along a second straight area, a second arc area, a third straight area, a third arc area, a fourth straight area, and a fourth arc area, all in the opposite direction to the winding direction. The second to fourth half-turns are the areas most prone to damage. In this embodiment, by setting the range of the second to fourth half-turns as a non-recessed area 22, the probability of damage can be minimized.

[0086] Based on any of the above embodiments, in one embodiment of this application, when the battery cell is a wound battery cell, the distance between the starting side of the recessed area 21 on the first surface of the first electrode 100 and the starting side of the active material layer 2 on the first surface of the first electrode 100 along the winding direction of the first electrode 100 is greater than 2 mm.

[0087] Along the winding direction of the first electrode 100, the starting side of the recessed region 21, which is also the starting position of the recessed region 21, is the starting side of the active material layer 2, which is also the position where the active material layer 2 first appears along the winding direction.

[0088] In a wound battery cell, on the one hand, since the end of the active material layer 2 on the first surface of the first electrode 100 is close to the winding start end, there is a non-stacked area between the first electrode 100 and the second electrode 200 along the winding direction at this position. The length of this non-stacked area along the winding direction is generally greater than 2mm. Therefore, in this embodiment, the distance between the starting side of the recessed area 21 on the first electrode 100 and the starting side of the active material layer 2 is set to be greater than 2mm. On the other hand, since the active material layer 2 on the first surface of the first electrode 100 has a thinning phenomenon, the thickness of the active material layer 2 at this position is uneven, with some areas of smaller thickness. If a groove 211 or recess is set in this area, there is a risk of puncturing the first electrode 100. Setting the distance between the starting side of the recessed area 21 on the first surface of the first electrode 100 and the starting side of the active material layer 2 to be greater than 2mm can reduce the risk of burrs generated by the first electrode 100 puncturing the separator and causing a short circuit in the battery.

[0089] Based on any of the above embodiments, in one embodiment of this application, when the battery cell is a wound battery cell, the distance between the starting side of the recessed area 21 on the second surface of the first electrode 100 and the starting side of the active material layer 2 on the second surface of the first electrode 100 along the winding direction of the battery cell is greater than 2 mm.

[0090] Since the thickness of the active material layer 2 at the beginning of the second surface of the first electrode 100 is relatively thin, there is a risk of puncturing the first electrode 100 if a groove 211 or recess is set in this area. Setting the distance between the starting side of the recessed area 21 and the starting side of the active material layer 2 on the second surface of the first electrode 100 to be greater than 2 mm can reduce the risk of puncturing the first electrode 100.

[0091] like Figures 4 to 12As shown, based on any of the above embodiments, in one embodiment of this application, when the battery cell is a wound battery cell, in the third direction X, the first electrode 100 includes a first edge region S1 and a second edge region S2; the first edge region S1 is an edge region close to the tab 3, the second edge region S2 is an edge region away from the tab 3, and the second direction Y and the third direction X are perpendicular to each other; the size of the recessed area 21 along the third direction X is less than or equal to the size of the first electrode 100 along the third direction X.

[0092] The first electrode 100 can be of a conventional structure, such as... Figure 4 , Figure 7 and Figure 10 As shown, the tab 3 is located at the end of the first electrode 100; or the tab is centrally located, such as... Figure 5 , Figure 8 and Figure 11 As shown, the tab 3 is located in the middle of the length of the first electrode 100; or a multi-tab structure, such as... Figure 6 , Figure 9 and Figure 12 As shown, the first electrode 100 is provided with multiple tabs 3, and the tabs 3 can be integrated with the current collector 1.

[0093] Please refer to Figures 4 to 6 As shown, when the size of the recessed region 21 along the third direction X is equal to the size of the first electrode 100 along the third direction X, that is, when the recessed region 21 is located between the edge of the first edge region S1 and the end of the first edge region S1, and the recessed region 21 is located between the edge of the second edge region S2 and the end of the second edge region S2, the dynamic performance of the first edge region S1 and the second edge region S2 can be improved, meeting the requirements of high-rate charge and discharge. It should be noted that when the first edge S1 and the second edge region S2 are recessed regions, that is, when the size of the recessed region 21 along the third direction X is equal to the size of the first electrode 100 along the third direction X, the recessed region can penetrate the active material layer 2 along the third direction X of the first electrode 100.

[0094] When the size of the recessed region 21 along the third direction X is smaller than the size of the first electrode 100 along the third direction X, the area between the edge of the recessed region 21 near the first edge region S1 and the end of the first edge region S1, and the area between the edge of the recessed region near the second edge region S2 and the end of the second edge region S2, are both designated as non-recessed regions 22. Figures 7 to 9 As shown; or, either the side edge of the recessed area 21 near the first edge area S1 and the end of the first edge area S1, or the side edge of the recessed area near the second edge area S2 and the end of the second edge area S2, is set as a non-recessed area 22, and the other is set as a recessed area 21.

[0095] When the recessed region 21 is configured as a non-recessed region 22 between the edge of the recessed region 21 near the first edge region S1 and the end of the first edge region S1, and between the edge of the recessed region 21 near the second edge region S2 and the end of the second edge region S2, the area of ​​the non-recessed region 22 on the first electrode 100 is larger, which can further improve the strength of the first electrode 100. At the same time, the weight loss rate of the first electrode 100 is reduced, which can improve the energy density of the battery. It can also improve the strength of the first edge region S1 and the second edge region S2, effectively improving the lithium plating or short circuit caused by powder shedding in the first edge region S1 and the second edge region S2.

[0096] like Figures 10 to 12 As shown, the recessed region 21 is defined between the edge of the recessed region 21 near the first edge region S1 and the end of the first edge region S1, and the recessed region 21 is defined between the edge of the recessed region 21 near the second edge region S2 and the end of the second edge region S2. This can improve the strength of the second edge region S2, reduce the weight loss rate of the active material layer 2, and increase the energy density. In addition, it can improve the dynamic performance of the first edge region S1, so that the cell meets the requirements of dynamic performance.

[0097] When the first electrode 100 is a multi-tab electrode 3, the tabs 3 are close to the first edge region S1, where the current density is higher and heat generation is greater. The recessed region 21 is also set as a recessed region 21 between the edge of the first edge region S1 and the end of the first edge region S1. This can improve the heat accumulation caused by the higher current density in the first edge region S1 and improve the heat dissipation effect on the side close to the tab 3. The second edge region S2 is far from the tab 3 and has a relatively lower current density. Considering the battery energy density and the risk of powder shedding from the edge of the first electrode 100, the second edge region S2, which is far from the tab 3, can be set as a non-recessed region 22. This can improve the situation of powder shedding or electrode breakage caused by external force on the edge of the first electrode 100 and prevent the second edge region S2 from being damaged under external force.

[0098] For multi-tab electrode plates, the number of tabs 3 is not limited in this embodiment and can be set by the user.

[0099] When the first electrode 100 has a tab-centered structure, the tab 3 is located in the tab groove 11. There is no active material in the tab groove 11. The tab groove 11 can be formed by cleaning the active material layer 2 to expose the current collector 1. The tab groove 11 can be located in the middle of the active material layer 22.

[0100] In this embodiment, the size of the tab groove 11 is not limited and can be set by the user.

[0101] Please refer to Figure 5In one embodiment of this application, in order to match the width of different tabs 3 and meet welding requirements, the width W of the tab groove 11 along the second direction Y can be in the range of 6mm to 20mm; and / or, the length L3 of the tab groove 11 along the third direction X can be in the range of 8mm to 30mm.

[0102] For example, the width W of the tab groove 11 can be 6mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, etc.; the length L3 of the tab groove 11 can be 8mm, 10mm, 15mm, 20mm, 25mm, 28mm, 30mm, etc.

[0103] It should be noted that in this embodiment, the size of the non-recessed area 22 between the edge of the recessed area 21 near the first edge area S1 and the end of the first edge area S1 is not limited and can be set by the user.

[0104] As one possible implementation, in the third direction X, the recessed area 21 is configured as a non-recessed area 22 between the side edge of the first edge area S1 and the end of the first edge area S1. The size of the non-recessed area 22 near the first edge area S1 is E1, which satisfies: 0.05 mm ≤ E1 ≤ 10 mm.

[0105] For example, the size E1 of the non-recessed area 22 between the side edge of the recessed area 21 near the first edge area S1 and the end of the first edge area S1 can be 0.05mm, 0.1mm, 0.5mm, 1mm, 3mm, 5mm, 7mm, 9mm, 10mm, etc.

[0106] In the third direction X, there is an overhang region between the first electrode 100 and the second electrode 200, which is the first overhang region, i.e., the region where the negative electrode is wider than the positive electrode. In this embodiment, when the first electrode 100 is a negative electrode, if the size E1 of the non-recessed area 22 between the edge of the recessed area 21 near the first edge area S1 and the end of the first edge area S1 is less than 0.05mm, it cannot cover the first overhang region. If the size E1 of the non-recessed area 22 between the edge of the recessed area 21 near the first edge area S1 and the end of the first edge area S1 is greater than 10mm, it will cause a decrease in the dynamic performance of the battery cell, and thus may not be able to meet the requirements of high-rate charging and discharging.

[0107] It should be noted that in this embodiment, the size of the non-recessed area 22 between the edge of the recessed area 21 near the second edge area S2 and the end of the second edge area S2 is not limited and can be set by the user.

[0108] In the third direction X, the recessed area 21 is set as a non-recessed area 22 between the side edge of the second edge area S2 and the end of the second edge area S2. The size of the non-recessed area 22 near the second edge area S2 is E2, which satisfies: 0.05mm≤E2≤10 mm; the second direction Y and the third direction X are perpendicular to each other.

[0109] For example, the size E2 of the non-recessed area 22 between the side edge of the recessed area 21 near the second edge area S2 and the end of the second edge area S2 can be 0.05mm, 0.1mm, 0.5mm, 1mm, 3mm, 5mm, 7mm, 9mm, 10mm, etc.

[0110] In the third direction X, there is an overhang region between the first electrode 100 and the second electrode 200, which is the second overhang region, i.e., the region where the negative electrode is wider than the positive electrode. In this embodiment, when the first electrode 100 is a negative electrode, if the size E2 of the non-recessed area 22 between the edge of the recessed area 21 near the second edge area S2 and the end of the second edge area S2 is less than 0.05 mm, it cannot cover the second overhang region. If the size E2 of the non-recessed area 22 between the edge of the recessed area 21 near the second edge area S2 and the end of the second edge area S2 is greater than 10 mm, it will cause a decrease in the dynamic performance of the battery cell, and thus may not be able to meet the requirements of high-rate charging and discharging.

[0111] Based on any of the above embodiments, in one embodiment of this application, along the third direction X, the edge of the first electrode 100 near the first edge region S1 extends beyond the edge of the second electrode 200 by a dimension that constitutes the first overhang region. Along the third direction X, the dimension E1 of the non-recessed region 22 near the first edge region S1 is greater than the dimension of the first overhang region along the third direction X, so as to avoid the appearance of a recess or groove in the first overhang region, which would affect the strength of the first overhang region. At the same time, it also avoids the reduction of the active material layer 2 due to the presence of the recessed region 21 in the first overhang region, which would lead to edge lithium plating.

[0112] Based on any of the above embodiments, in one embodiment of this application, along the third direction X, the edge of the first electrode 100 near the second edge region S2 extends beyond the edge of the second electrode 200 to form the second overhang region. Along the third direction X, the size E2 of the non-recessed region 22 near the second edge region S2 is greater than the size of the second overhang region along the third direction X, so as to avoid the emergence of recesses or grooves in the second overhang region, which would affect the strength of the second overhang region. At the same time, it also avoids the reduction of the active material layer 2 due to the presence of the recessed region 21 in the second overhang region, which would lead to edge lithium plating.

[0113] Based on any of the above embodiments, in one embodiment of this application, when the battery cell is a wound battery cell, the length of the non-recessed area 22 of the active material layer 2 located on the second surface of the first electrode 100 on the outermost side of the battery cell along the second direction Y is 20mm to 1000mm.

[0114] For example, the length L1 of the non-recessed area 22 of the active material layer 22 on the second surface of the current collector 1 along the second direction Y can be 20mm, 50mm, 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm, etc.

[0115] In this embodiment, the length L1 of the recessed area 21 on the second surface of the first electrode 100 is set to 20mm~1000mm, which can keep the outermost surface of the cell flat, greatly improve the cell's resistance to external forces, and solve the problem of lithium plating caused by the destruction of the outer electrode surface structure after the cell is subjected to force.

[0116] like Figure 13 and Figure 14 As shown, based on any of the above embodiments, in one embodiment of this application, when the battery cell is a wound battery cell, the length L2 of the non-recessed area 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y ranges from 2mm to 1000mm.

[0117] It should be noted that, in this embodiment, the relationship between the length of the non-recessed region 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y and the length of the non-recessed region 22 of the active material layer 2 on the second surface of the first electrode 100 along the second direction Y is not limited.

[0118] like Figure 14As shown, in one possible implementation, the length L2 of the non-recessed region 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y can be less than the length L1 of the non-recessed region 22 of the active material layer 2 on the second surface of the first electrode 100 along the second direction Y. In this case, the length L2 of the non-recessed region 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y can be in the range of 2mm to 20mm, which can reduce the overall weight loss rate of the active material layer 2 and improve the energy density.

[0119] As another possible implementation, the length L2 of the non-recessed region 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y can be equal to the length L1 of the non-recessed region 22 of the active material layer 2 on the second surface of the first electrode 100 along the second direction Y. In this case, the length L2 of the non-recessed region 22 of the active material layer 2 on the first surface of the first electrode 100 along the second direction Y can be in the range of 20mm~1000mm. The active material layers 22 on the first and second surfaces of the first electrode 100 are more symmetrical, and the stress on both sides of the current collector 1 is consistent, which can avoid deformation on one side of the first electrode 100 and make it less likely to shed powder and deposit lithium.

[0120] Based on any of the above embodiments, in one embodiment of this application, the NP ratio between the first electrode 100 and the second electrode 200 is greater than 1.01 to ensure that the positive and negative electrode ratio is within a certain safe range and to avoid lithium deposition in the cell during cycling.

[0121] For example, the NP ratio between the first electrode 100 and the second electrode 200 can be 1.045, 1.065, etc.

[0122] This application also provides a lithium-ion battery, including the cell described in any of the above embodiments.

[0123] It should be noted that lithium-ion batteries also include a membrane casing for encapsulating the battery cells, which can be an aluminum-plastic film.

[0124] The manufacturing method of the wound battery cell in this application is described below.

[0125] The first electrode 100 is the negative electrode. The negative electrode current collector is a copper foil with a thickness of 5 micrometers, and the negative electrode active material is graphite. The negative electrode active material, binder SBR, dispersant CMC, conductive carbon black, and solvent water are mixed and stirred in a certain proportion to form a slurry. After being coated onto the copper foil, it is dried, rolled, and cut to form the negative electrode. The areas of the negative electrode active material layer that need to be grooved are processed by laser wire bonding to form grooves.

[0126] The second electrode 200 is the positive electrode. The positive electrode current collector is an aluminum foil with a thickness of 8 micrometers, and the positive electrode active material is lithium cobalt oxide. Lithium cobalt oxide, binder (polyvinylidene difluoride, PVDF), conductive agent (carbon black), and solvent (N-Methylpyrrolidone, NMP) are mixed and stirred in a certain proportion to form a slurry. The slurry is coated onto the aluminum foil and then baked, rolled, and slit to form the positive electrode.

[0127] The prepared negative electrode, separator and positive electrode are stacked and wound to form a wound battery cell.

[0128] The parameters involved in the above production process can be those shown in the examples below.

[0129] Example 1

[0130] (1) Negative electrode: The length of the negative electrode active material layer on the second surface is 1382 mm, and the length of the negative electrode active material layer on the first surface is 1269 mm; the width of the wound cell is 61.7 mm, and the thickness of the wound cell is 4.09 mm.

[0131] (2) Negative electrode: Laser wire bonding parameters: groove spacing is 10mm, groove depth is 10μm, groove width is 85μm;

[0132] (3) Negative electrode: The distance between the starting position of the recessed area on the negative electrode active material layer on the second surface and the starting position of the negative electrode active material layer is 5mm. In the outermost first electrode area of ​​the cell, the length of the recessed area on the first surface along the second direction is 59mm, and the length of the non-recessed area on the first surface is 5mm. In the outermost first electrode area of ​​the cell, the length of the recessed area on the second surface along the second direction is 0mm, and the length of the non-recessed area on the first surface is 64mm.

[0133] The tail region of the first electrode has a non-recessed area of ​​the negative electrode active material layer on the second surface with a length of 126.8 mm along the second direction; the distance between the starting position of the recessed area on the negative electrode active material layer on the first surface and the starting position of the negative electrode active material layer is 5 mm; the tail region of the first electrode has a non-recessed area of ​​the negative electrode active material layer on the first surface with a length of 5 mm along the second direction.

[0134] Example 2

[0135] (1) Negative electrode: The length of the negative electrode active material layer on the second surface is 1382 mm, and the length of the negative electrode active material layer on the first surface is 1269 mm; the width of the wound cell is 61.7 mm, and the thickness of the wound cell is 4.09 mm.

[0136] (2) Negative electrode: Laser wire bonding parameters: groove spacing is 3mm, groove depth is 25μm, groove width is 250μm;

[0137] (3) Negative electrode: The distance between the starting position of the recessed area on the negative electrode active material layer on the second surface and the starting position of the negative electrode active material layer is 5mm. In the outermost first electrode area of ​​the cell, the length of the recessed area on the first surface along the second direction is 50mm, and the length of the non-recessed area on the first surface is 14mm. In the outermost first electrode area of ​​the cell, the length of the recessed area on the second surface along the second direction is 0mm, and the length of the non-recessed area on the first surface is 64mm.

[0138] In the tail region of the first electrode, the non-recessed area of ​​the negative electrode active material layer on the second surface has a length of 126.8 mm along the second direction; the distance between the starting position of the recessed area on the negative electrode active material layer on the first surface and the starting position of the negative electrode active material layer is 5 mm. In the tail region of the first electrode, the non-recessed area of ​​the negative electrode active material layer on the first surface has a length of 126.8 mm along the second direction.

[0139] Example 3

[0140] The difference from Example 1 is that, on the second surface of the negative electrode, the size E1 of the non-recessed area near the first edge region is 0 mm, and the size E2 of the non-recessed area near the second edge region is 5 mm.

[0141] Example 4

[0142] The difference from Example 1 is that, on the second surface of the negative electrode, the size E1 of the non-recessed area near the first edge region is 5 mm, and the size E2 of the non-recessed area near the second edge region is 5 mm.

[0143] Comparative Example 1

[0144] The difference from Example 1 is that, in the tail region, the entire negative electrode active material layer on the second surface is set as a recessed area, and the entire negative electrode active material layer on the first surface is set as a recessed area.

[0145] The lithium deposition of batteries under cycling was tested after different types of wound cells were subjected to the same external force. The test results are shown in Table 1.

[0146] The testing process for lithium plating is as follows: After the wound cell is cycled for 500T at room temperature: ① Confirm whether the negative electrode sheet has thickened due to delamination and whether there is a shadow by CT (computed tomography); ② Disassemble the wound cell with full charge to confirm whether the negative electrode sheet has turned white and has lithium plating.

[0147] Table 1

[0148] Lithium plating Example 1 no Example 2 no Example 3 no Example 4 no Comparative Example 1 yes

[0149] As shown in Table 1, the batteries in the embodiments did not exhibit lithium plating after being subjected to external force during cycle testing, while the battery in Comparative Example 1 showed lithium plating. This indicates that the battery performance provided by this application can resist external force and the resulting lithium plating, ensuring the safe use performance of the battery cell.

[0150] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0151] The battery cell and lithium-ion battery provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the solution and core ideas of this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the principles of this application, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A battery cell, characterized in that, It includes a first electrode, a diaphragm and a second electrode stacked together, wherein the first electrode includes a current collector and an active material layer disposed on the current collector; Along a first direction, the first electrode has a first surface and a second surface disposed opposite to each other. The first surface is the surface of the first electrode close to the center of the battery cell, and the second surface is the surface of the first electrode away from the center of the battery cell. At least one side surface of the first electrode is provided with a non-recessed area and a recessed area including at least one recess or groove. At least a portion of the recessed area and the non-recessed area are disposed adjacent to each other along a second direction. In the first electrode plate located on the outermost side of the battery cell, the length of the recessed area of ​​the active material layer on the second surface along the second direction is less than the length of the recessed area of ​​the active material layer on the first surface; the second direction is perpendicular to the first direction.

2. The battery cell as described in claim 1, characterized in that, The battery cell is a laminated battery cell, which includes at least two first electrodes stacked together. The outermost first electrode of the battery cell is the electrode that is furthest from the center of the battery cell in the thickness direction.

3. The battery cell as described in claim 1, characterized in that, The battery cell is a wound battery cell.

4. The battery cell as described in claim 3, characterized in that, The battery cell includes a flat section and an arc section connected to the flat section. In the first electrode located on the outermost side of the battery cell, the length of the non-recessed area of ​​the active material layer on the second surface along the second direction is greater than the length of the non-recessed area of ​​the active material layer on the first surface along the second direction. The first electrode located on the outermost side of the battery cell consists of a first straight area and a first arc area formed from the winding end of the first electrode of the battery cell along the opposite direction to the winding direction of the wound battery cell. The first straight area is located in the straight section of the battery cell, and the first arc area is located in the arc section of the battery cell.

5. The battery cell as described in claim 3, characterized in that, The tail region of the first electrode includes the first to sixth half turns starting from the winding end of the first electrode of the cell, along the direction opposite to the winding direction, with each half turn including a straight area and an arc area.

6. The battery cell as described in claim 3, characterized in that, Along the winding direction of the first electrode, the distance between the starting side of the recessed area on the first surface of the first electrode and the starting side of the active material layer on the first surface of the first electrode is greater than 2 mm along the winding direction of the first electrode. And / or, along the winding direction of the battery cell, the distance between the starting side of the recessed area on the second surface of the first electrode and the starting side of the active material layer on the second surface of the first electrode is greater than 2 mm along the winding direction of the first electrode.

7. The battery cell as described in claim 3, characterized in that, In the third direction, the first electrode includes a first edge region and a second edge region; the first edge region is an edge region close to the electrode tab, and the second edge region is an edge region away from the electrode tab, and the second direction is perpendicular to the third direction. The dimension of the recessed area along the third direction is less than or equal to the dimension of the first electrode along the third direction.

8. The battery cell as described in claim 7, characterized in that, In the third direction, the area between the edge of the recessed area near the first edge area and the end of the first edge area is set as a non-recessed area, and the size of the non-recessed area near the first edge area is E1, which satisfies: 0.05 mm ≤ E1 ≤ 10 mm; And / or, In the third direction, a non-recessed area is set between the edge of the recessed area near the second edge area and the end of the second edge area. The size of the non-recessed area near the second edge area is E2, which satisfies: 0.05 mm ≤ E2 ≤ 10 mm; the second direction and the third direction are perpendicular to each other.

9. The battery cell as described in claim 7, characterized in that, Along the third direction, the edge of the first electrode near the first edge region extends beyond the edge of the second electrode by a dimension that constitutes the first overhang region; along the third direction, the dimension E1 of the non-recessed region near the first edge region is greater than or equal to the dimension of the first overhang region along the third direction; and / or, Along the third direction, the edge of the first electrode near the second edge region extends beyond the edge of the second electrode region by a dimension that constitutes the second overhang region. Along the third direction, the dimension E2 of the non-recessed region near the second edge region is greater than or equal to the dimension of the second overhang region along the third direction.

10. The battery cell as described in claim 3, characterized in that, In the first electrode located on the outermost side of the battery cell, the non-recessed region of the active material layer on the second surface of the first electrode has a length ranging from 20 mm to 1000 mm along the winding direction; and / or, The length of the non-recessed area of ​​the active material layer on the first surface of the first electrode along the winding direction ranges from 2 mm to 1000 mm.

11. The battery cell as described in claim 1, characterized in that, The depth range of each recess or groove in the recessed area along the first direction is 10μm~30μm; and / or, The spacing between adjacent recesses or grooves along the second direction ranges from 0.2 mm to 10 mm; and / or, The width of the recess or groove along the second direction ranges from 30μm to 250μm.

12. A lithium-ion battery, characterized in that, Includes the battery cell as described in any one of claims 1 to 11.

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