Battery cell and battery

Abstract

The utility model provides a battery cell and a battery, the battery cell comprises a shell, and the shell is provided with an accommodating cavity; the roll core is positioned in the accommodating cavity, the roll core comprises a first pole piece, a diaphragm and a second pole piece which are wound, the diaphragm is positioned between the adjacent first pole piece and second pole piece, and the polarities of the first pole piece and the second pole piece are opposite; the first pole piece is provided with a thinned part, the thickness of the thinned part is smaller than that of other positions of the first pole piece in the second direction, and the thinned part is opposite to the end corner position of the shell. According to the utility model, the problem that the high-energy-density battery cell is easy to generate corner cracks during long circulation can be obviously improved, the circulation times of corner cracks at four corners can be effectively prolonged, and even corner cracks do not occur during long-circulation use, so that the overall service life of the battery cell is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to an electrode core and a battery. Background Art

[0002] With the advent of the 5G era and the rapid development of lithium-ion battery technology, people have put forward higher requirements for the energy density, fast charging ability, and charge-discharge rate of lithium-ion batteries. However, with the improvement of living quality, while pursuing high energy density and long cycle life, the safety issues of lithium-ion batteries have also become the focus of people's attention.

[0003] Currently, due to the more extreme size design of high-energy-density batteries, during long-term cycling, the expansion of the wound core repeatedly squeezes and stretches the aluminum-plastic film, and the four corners of the electrode core are prone to corner cracking, resulting in problems such as excessive deep expansion, increased internal resistance, bulging, and liquid leakage, leading to battery cycle failure, and even causing combustion and explosion.

[0004] The foregoing description is provided to give general background information and does not necessarily constitute prior art. Summary of the Utility Model

[0005] The embodiments of the utility model provide an electrode core and a battery, which can significantly improve the corner cracking problem that is prone to occur during long-term cycling of high-energy-density electrode cores, and even no corner cracking occurs during long-term cycling use, thereby improving the overall service life of the electrode core.

[0006] The utility model provides an electrode core, including:

[0007] A housing having a receiving cavity;

[0008] A wound core located in the receiving cavity, the wound core includes a wound first electrode sheet, a separator, and a second electrode sheet, the separator is located between the adjacent first electrode sheet and the second electrode sheet, and the first electrode sheet and the second electrode sheet have opposite polarities;

[0009] The first electrode sheet has a thinning portion, along the second direction, the thickness of the thinning portion is less than the thickness of the rest of the first electrode sheet, and the thinning portion is opposite to the end corner position of the housing.

[0010] Through the above settings, that is, through the setting of the thinning part, the depth of the four corners of the corresponding core is reduced. During the long cycle process, there is a larger space reserved between the core corners of this special battery cell and the housing, and the expansion of the core corners is smaller than that of the core corners of a battery cell with a normal structure, resulting in a smaller extrusion stress on the corners. Due to the reduction of the extrusion stress, the problem of corner cracking that easily occurs in high-energy-density battery cells during long-cycle use has been significantly improved, effectively extending the number of cycles before the battery cell shows corner cracking at the four corners. In fact, corner cracking may not occur even during long-cycle use, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the expansion stress but also may optimize the internal structure of the battery cell, improving the cycle stability and safety performance of the battery.

[0011] In some alternative embodiments, along the first direction, the orthogonal projection of the end corner of the housing on the plane where the first pole piece with the thinning part is located is within the projection of the thinning part.

[0012] In some alternative embodiments, the core has a flat area and an arc area. The arc area is located on one side of the flat area. The thinning part is located in the arc area and extends towards the flat area, covering at least part of the flat area.

[0013] In some alternative embodiments, the length of the thinning part covering the flat area is greater than or equal to 1 mm and less than or equal to 3 mm.

[0014] In some alternative embodiments, the first pole piece is located on the outermost layer of the core;

[0015] The thinning part includes a plurality of first grooves formed in the first pole piece. The plurality of first grooves are located on opposite sides of the first pole piece along the second direction, and there is an included angle between the first direction and the second direction.

[0016] In some alternative embodiments, the thinning part includes through holes that penetrate through opposite sides of the first pole piece along the third direction.

[0017] In some alternative embodiments, the first pole piece is provided with a first current collector and a first active material layer, and the first active material layer is formed on at least one surface in the thickness direction of the first current collector;

[0018] The first grooves are formed in the first active material layer.

[0019] In some alternative embodiments, a protective layer is further included. The protective layer is attached to the inside of the first grooves and covers at least part of the bottoms of the first grooves.

[0020] In some alternative embodiments, it includes at least one of the following:

[0021] The thickness of the protective layer is less than the thickness of the first grooves;

[0022] Along the second direction, the edge of the protective layer extends beyond the edge of the first groove, and the distance between the edge of the protective layer and the edge of the first groove is greater than or equal to 0.2 mm and less than or equal to 2 mm.

[0023] In some alternative embodiments, the protective layer is an adhesive layer or a ceramic layer.

[0024] In some alternative embodiments, the ceramic layer includes a ceramic slurry layer or a ceramic adhesive layer;

[0025] The adhesive layer is one of a rubber adhesive tape, an acrylic adhesive tape, a polypropylene adhesive tape, and a styrene-isoprene-styrene adhesive tape.

[0026] In some alternative embodiments, the second pole piece has a thinning portion; the thinning portion further includes a plurality of second grooves formed in the second pole piece, and the plurality of second grooves are located on opposite sides of the second pole piece along the second direction.

[0027] In some alternative embodiments, the area of the second groove is smaller than the area of the first groove;

[0028] The second pole piece covers the first groove, and the distance between the width edges of the second pole piece and the first pole piece is greater than or equal to 1 mm.

[0029] In some alternative embodiments, the ratio of the notch area of the first groove to the notch area of the second groove is greater than or equal to 105% and less than or equal to 200%;

[0030] The distance between the edge of the second pole piece and the edge of the first pole piece is greater than or equal to 2 mm.

[0031] In some alternative embodiments, the inner wall surface of the thinning portion includes at least one of an arc surface and a flat surface.

[0032] In some alternative embodiments, along the winding direction of the core, both the first pole piece and the second pole piece have a starting end and a finishing end, and the thinning portion is located at the finishing end of at least one of the first pole piece and the second pole piece.

[0033] In some alternative embodiments, the ratio of the width of the thinning portion to the width of the core is greater than or equal to 1% and less than or equal to 30%.

[0034] In some alternative embodiments, the core has multiple layers, at least two layers of the first pole pieces are provided with thinning portions, and the positions of the thinning portions in at least two layers of the first pole pieces correspond to each other; and / or,

[0035] At least two layers of the second pole pieces are provided with thinning portions, and the positions of the thinning portions in at least two layers of the second pole pieces correspond to each other.

[0036] The present utility model also provides a battery, which includes the battery cell as described above.

[0037] The battery cell and the battery provided by the present utility model, the battery includes the battery cell; the battery cell includes a housing having an accommodation cavity; a wound core located in the accommodation cavity, the wound core includes a wound first pole piece, a separator and a second pole piece, the separator is located between adjacent first and second pole pieces, and the first and second pole pieces have opposite polarities; the first pole piece has a thinning portion, along the second direction, the thickness of the thinning portion is less than the thickness of the rest of the first pole piece, and the thinning portion is opposite to the end corner position of the housing.

[0038] Through the arrangement of the thinning portion, the depth of the four corners of the corresponding wound core becomes smaller. During long-term cycling, there is a larger space reserved between the wound core corners of this special battery cell and the housing, and the swelling of the corners is smaller than that of the wound core corners of a normal structure battery cell, and the extrusion stress on the corners is smaller. Due to the reduction of the extrusion stress, the problem of corner cracking that easily occurs in high energy density battery cells during long-term cycling has been significantly improved, effectively extending the number of cycles before the battery cell shows corner cracking at the four corners, and even not showing corner cracking during long-term cycling, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the swelling stress, but also may optimize the internal structure of the battery cell, improving the cycling stability and safety performance of the battery. Description of the Drawings

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 Structural schematic diagram of a battery cell provided by the prior art;

[0041] Figure 2 Cross-sectional view of a battery cell provided by the prior art;

[0042] Figure 3 Structural schematic diagram of a battery cell provided by an embodiment of the present utility model from a second perspective;

[0043] Figure 4 For Figure 3 Cross-sectional view of the wound core with a groove at A - A' in

[0044] Figure 5 For Figure 3 Cross-sectional view of the wound core with another groove at A - A' in

[0045] Figure 6 For Figure 3Cross-sectional view of a core with another type of groove along A-A';

[0046] Figure 7 Structural schematic diagram of the first type of first pole piece provided by an embodiment of the present utility model;

[0047] Figure 8 Structural schematic diagram of the second type of first pole piece provided by an embodiment of the present utility model;

[0048] Figure 9 Structural schematic diagram of the third type of first pole piece provided by an embodiment of the present utility model;

[0049] Figure 10 Cross-sectional view of the third type of first pole piece provided by an embodiment of the present utility model;

[0050] Figure 11 Structural schematic diagram of another type of battery cell provided by an embodiment of the present utility model;

[0051] Figure 12 Cross-sectional view of the core in another type of battery cell provided by an embodiment of the present utility model;

[0052] Figure 13 Structural schematic diagram of the fourth type of first pole piece provided by an embodiment of the present utility model;

[0053] Figure 14 Structural schematic diagram of the fifth type of first pole piece provided by an embodiment of the present utility model;

[0054] Figure 15 Structural schematic diagram of the sixth type of first pole piece provided by an embodiment of the present utility model;

[0055] Figure 16 Structural schematic diagram of the seventh type of first pole piece provided by an embodiment of the present utility model.

[0056] Description of reference numerals:

[0057] 100 - Battery cell;

[0058] 110 - Housing;

[0059] 120 - Core;

[0060] 121 - First pole piece;

[0061] 1211 - First current collector;

[0062] 1212 - First active material layer;

[0063] 122 - Second pole piece;

[0064] 1221 - Second current collector;

[0065] 1222 - The second active material layer;

[0066] 123 - Straight section;

[0067] 124 - Arc section;

[0068] 125 - Starting end;

[0069] 126 - Ending end;

[0070] 127 - Diaphragm;

[0071] 130 - First groove;

[0072] 140 - Second groove;

[0073] 150 - Protective layer. Detailed implementation manners

[0074] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are partial embodiments of the present utility model, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts belong to the scope of protection of the present utility model. All other embodiments obtained belong to the scope of protection of the present utility model. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0075] In the description of the present utility model, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "depth", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model.

[0076] In the present utility model, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a direct connection, or an indirect connection through an intermediate medium, and may be the communication of the inner cavities of 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 the present utility model can be understood according to specific circumstances.

[0077] It should be noted that in the description of the present utility model, the terms "first", "second", "third" are only used for conveniently describing different cavity components, and cannot be understood as indicating or implying an order relationship, relative importance, or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include at least one such feature.

[0078] Currently, Figure 1 FIG. is a schematic structural diagram of a battery cell provided by the prior art. Figure 2 FIG. is a sectional view of a battery cell provided by the prior art, as Figure 1 and Figure 2 shown, the battery cell includes a wound first pole piece 121, a separator, and a second pole piece 122. For high-energy-density batteries, due to more extreme size designs, during long cycling, the swelling of the wound core repeatedly squeezes and stretches the aluminum plastic film, and the four corners of the battery cell are prone to corner cracking, resulting in excessive depth swelling, increased internal resistance, bulging and liquid leakage, etc., leading to battery cycling failure, and even causing combustion and explosion.

[0079] In order to overcome the defects in the prior art, the battery cell and battery provided by the present utility model, through the setting of the thinning part, reduce the depth of the corresponding four corners of the wound core. During long cycling, there is a larger space reserved between the wound core corner position of this special battery cell and the housing, and the swelling of the corner position is smaller than that of the normal-structured battery cell, and the extrusion stress on the corner position is smaller. Due to the reduction of the extrusion stress, the corner cracking problem that easily occurs in high-energy-density battery cells during long cycling use has been significantly improved, effectively extending the number of cycles before the four corners of the battery cell crack, and even not cracking during long cycling use, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the swelling stress, but also may optimize the internal structure of the battery cell, improving the cycling stability and safety performance of the battery.

[0080] The following will describe the content of the present utility model in detail with reference to the accompanying drawings, so that those skilled in the art can understand the content of the present utility model more clearly and in detail.

[0081] Figure 3 FIG. is a schematic structural diagram of a battery cell from a second perspective provided by an embodiment of the present utility model. Figure 4 is Figure 3The sectional view of a core with a groove along A-A' Figure 5 is Figure 3 The sectional view of another core with a groove along A-A' Figure 6 is Figure 3 The sectional view of yet another core with a groove along A-A' Figure 7 This is the schematic structural view of the first first pole piece provided by the embodiment of the present utility model.

[0082] As Figures 3 to 7 shown, the embodiment of the present utility model provides a battery cell 100, including:

[0083] A housing 110, the housing 110 having a receiving cavity;

[0084] In the present utility model, the housing 110 is generally of a structure such as an aluminum-plastic film, a transparent packaging film, etc., which can encapsulate the core 120 to form a soft-pack lithium-ion battery.

[0085] Among them, in some embodiments, the depth of the aluminum-plastic film housing 110 is 70μm - 200μm.

[0086] A core 120, the core 120 being located in the receiving cavity, the core 120 including a wound first pole piece 121, a separator 127, and a second pole piece 122, the separator 127 being located between adjacent first pole piece 121 and second pole piece 122, and the first pole piece 121 and the second pole piece 122 having opposite polarities;

[0087] The first pole piece 121 has a thinning portion, along the second direction, the thickness of the thinning portion is less than the thickness of the rest of the first pole piece 121, and the thinning portion is opposite to the end corner position of the housing 110.

[0088] It should be noted that the housing 110 is generally in a rectangular structure, and its end corners are specifically the positions of the corners in the rectangular structure. The core 120 is placed into the housing 110, and the corners of the core 120 correspond to the corners of the housing 110.

[0089] The core 120 includes a first pole piece 121, a second pole piece 122, and a separator 127. After stacking the first pole piece 121, the separator 127, and the second pole piece 122 together in sequence, they are wound from the starting end 125 to the ending end 126 to form the battery cell 100 of the lithium-ion battery.

[0090] The first pole piece 121 is located on the outermost side of the battery cell 100. The first pole piece 121 can be a positive electrode piece or a negative electrode piece. It can be understood that when the first pole piece 121 is a positive electrode piece, the second pole piece 122 is a negative electrode piece, and when the first pole piece 121 is a negative electrode piece, the second pole piece 122 is a positive electrode piece. In this embodiment, the first pole piece 121 is a positive electrode piece and the second pole piece 122 is a negative electrode piece.

[0091] It should be noted that a thinning portion can be provided on the first electrode tab 121, a thinning portion can be provided on the second electrode tab 122, or thinning portions can be provided on both the first electrode tab 121 and the second electrode tab 122. When the first electrode tab 121 is the positive electrode tab, the present invention mainly provides a thinning portion on the first electrode tab 121. Of course, according to actual conditions, a thinning portion can also be provided on the second electrode tab 122. For specific details, reference can be made to the following content, and no further elaboration will be provided here.

[0092] It should be noted that the position of the thinning portion is to match the end corner position of the housing 110, so that the depth at at least four end corners of the winding core 120 in the accommodation cavity is reduced, a part of the first electrode tab 121 is missing, or the first electrode tab 121 cannot exert or can only exert part of its capacity, and thus the corresponding second electrode tab 122 expands and becomes smaller during cycling.

[0093] Through the above settings, that is, through the setting of the thinning portion, the depth of the four corners of the corresponding winding core 120 becomes smaller. During long-term cycling, there is a larger space reserved between the corner positions of the winding core 120 of this special battery cell and the housing 110, and the expansion of the corner positions is smaller than that of a battery cell with a normal structure. The extrusion stress on the corner positions is smaller. Due to the reduction of the extrusion stress, the problem of corner cracking that easily occurs in high-energy-density battery cells during long-term cycling is significantly improved, effectively extending the number of cycles before the battery cell shows corner cracking at the four corners, and even not showing corner cracking during long-term cycling, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the expansion stress, but also may optimize the internal structure of the battery cell, improving the cycle stability and safety performance of the battery.

[0094] In addition, compared with the use of thick copper foil and increasing the P-A GAP (the difference between the punch length and the width of the second electrode tab 122) in the prior art, using the present invention can reduce the energy density loss of the lithium-ion battery by 0.3% - 1.2% on the premise of ensuring that the battery cell does not undergo corner breakage.

[0095] In addition, by manufacturing a thinning portion at the edge of at least one of the first electrode tab 121 and the second electrode tab 122, the time when the lithium-ion battery undergoes corner breakage (or bulging and leakage) during cycling can be delayed by 300T - 1000T, or even no breakage occurs. This method can reduce the energy density loss of the lithium-ion battery by 0.3% - 1.2%.

[0096] In some alternative embodiments, along the first direction, the orthographic projection of the end corner of the housing 110 on the plane where the first electrode tab 121 and / or the second electrode tab 122 with the thinning portion is located is within the projection of the thinning portion.

[0097] It should be noted that such a setting ensures that the area of the thinning part is larger than the area of the four end corners, thereby reducing the depth of the four corners of the corresponding core 120. During long cycling, there is a larger space reserved between the corner positions of the core 120 of this special battery cell and the housing 110, and the expansion of the corner positions is smaller than that of the corner positions of a battery cell with a normal structure, resulting in a smaller extrusion stress on the corner positions.

[0098] In addition, it should be noted that X represents the first direction, and the first direction X can be the thickness direction of the core 120.

[0099] In some alternative embodiments, the core 120 has a flat region 123 and a curved region 124. The curved region 124 is located on one side of the flat region 123. The thinning part is located in the curved region 124 and extends towards the flat region 123, covering at least part of the flat region 123.

[0100] It should be noted that the core 120 has a flat region 123 and a curved region 124. In the winding direction of the core 120, the flat part is the flat region 123, and the curved part is the curved region 124. This means that after the first pole piece 121 and the second pole piece 122 are wound, their flat parts are the flat region 123, and their curved parts are the curved region 124.

[0101] Specifically, taking the first pole piece 121 as an example, after the first pole piece 121 is wound, the thinning part covers at least part of the flat region 123. It can be understood that the thinning part can extend to the flat region 123 to increase the area of the thinning part, thereby reducing the depth of the four corners of the corresponding core 120.

[0102] In some alternative embodiments, the length of the thinning part covering the flat region 123 is greater than or equal to 1 mm and less than or equal to 3 mm.

[0103] It should be noted that only such a setting can ensure that the thinning part can cover the entire arc region of the corner position. This slot is located at the tail part of the first pole piece 121 and is located at the arc of the battery cell 100 after winding.

[0104] In some embodiments, the length of the thinning part (in the length direction of the first pole piece 121) needs to be greater than or equal to one-fourth of the arc circumference.

[0105] Exemplarily, the length range of the thinning part is: half of the arc circumference to half of the arc circumference + 3 mm.

[0106] In some alternative embodiments, the thinning part includes a plurality of first grooves 130 formed in the first pole piece 121. The plurality of first grooves 130 are located on opposite sides of the first pole piece 121 along the second direction, and there is an included angle between the first direction and the second direction.

[0107] It should be noted that Y represents the second direction, where the second direction can be the width direction of the first pole piece 121, or of course, the width direction of the housing 110.

[0108] In some embodiments, the first groove 130 is symmetrically arranged along the second direction at the edge of the first pole piece 121 and is spaced along the winding direction of the core. The winding direction of the core can be the length direction of the first pole piece 121, where Z represents the winding direction of the core.

[0109] As Figure 4 and Figure 7 shown, in some alternative embodiments, the thinning portion includes a through hole that penetrates through opposite sides of the first pole piece 121 along the third direction.

[0110] It should be noted that the groove can be formed by punching or cutting at specific positions on both side edges of the first pole piece 121.

[0111] Among them, the third direction is the thickness direction of the first pole piece 121, or it can be understood that the thickness direction of the core 120 in the flat area 123 is the same as the thickness direction of the first pole piece 121.

[0112] This means that the first pole piece 121 forms a notch along the third direction by punching or cutting, and this notch can be a kind of first groove 130.

[0113] In some embodiments, as Figure 4 shown, the first groove 130 is punched at the corner arc of the first pole piece 121.

[0114] Figure 8 This is the structural schematic diagram of the second first pole piece provided by the embodiment of the present invention. As Figure 5 and Figure 8 shown, in some alternative embodiments, the first pole piece 121 is provided with a first current collector 1211 and a first active material layer 1212, and the first active material layer 1212 is formed on at least one surface in the thickness direction of the first current collector 1211;

[0115] The first groove 130 is opened on the first active material layer 1212.

[0116] It should be noted that at specific positions on both side edges of the first pole piece 121, part of the coating paste is removed by laser cleaning (but it is necessary to ensure that the light aluminum foil is not exposed, that is, the first current collector 1211 is not exposed).

[0117] As Figure 3 and Figure 6 shown, the first groove 130 is only punched at the corner arc of the deep pit surface of the first pole piece 121, where the first groove 130 faces the film shell pit of the housing 110 when it enters the housing 110.

[0118] In some embodiments, if the depth of the single-sided first active material layer 1212 in the first electrode tab 121 is T / μm, the depth of cleaning the first active material layer 1212 can be 0.25*T to (T - 5)μm. Since the contact between the aluminum foil of the positive electrode and the negative electrode paste is the most dangerous short-circuit mode (direct ignition), it is necessary to ensure that the aluminum foil is not exposed to eliminate this most dangerous short-circuit mode.

[0119] It should be noted that the first electrode tab 121 includes a first current collector 1211 and first active material layers 1212 coated on opposite sides of the first current collector 1211.

[0120] In some examples, an aluminum foil or a composite current collector can be used as the first current collector 1211, and the composite current collector can include a polymer layer and two aluminum layers respectively located on opposite sides of the polymer layer.

[0121] Among them, the active material of the first active material layer 1212 includes one or more of lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium-rich manganese-based lithium.

[0122] Figure 9 This is a schematic structural diagram of the third first electrode tab provided by the embodiment of the present invention. Figure 10 This is a cross-sectional view of the third first electrode tab provided by the embodiment of the present invention.

[0123] As Figure 9 and Figure 10 shown, in some alternative embodiments, a protective layer 150 is further included. The protective layer 150 is attached to the first groove 130 and covers at least part of the bottom of the first groove 130.

[0124] It should be noted that covering the uncleaned paste with the protective layer 150 can limit the lithium-ion transport of the positive electrode in the covered area, reduce the swelling of the corresponding negative electrode, reduce the swelling at the corner position, and improve corner cracking.

[0125] In some embodiments, at specific positions on both sides of the first electrode tab 121, part of the depth of the first active material layer 1212 is removed by laser cleaning. The cleaned groove part is covered with the protective layer 150, and it is ensured that the thickness direction of the protective layer 150 does not exceed the first active material layer 1212 so as not to affect the depth of the first electrode tab 121.

[0126] In some alternative embodiments, it includes at least one of the following:

[0127] The thickness of the protective layer 150 is less than the thickness of the first groove 130;

[0128] Along the second direction, the edge of the protective layer 150 extends beyond the edge of the first groove 130, and the distance between the edge of the protective layer 150 and the edge of the first groove 130 is greater than or equal to 0.2 mm and less than or equal to 2 mm.

[0129] It should be noted that, as Figure 10 shown, H1 represents the thickness of the protective layer 150, and H2 represents the thickness of the first groove 130.

[0130] It should be noted that the depth of the first active material layer 1212 to be cleaned needs to be greater than the depth of the protective layer 150. The protective layer 150 needs to fall inside the first groove 130 and not exceed the paste coating in the normal area, but the edge of the protective layer 150 needs to extend 0.2 mm to 2 mm beyond the width direction of the first pole piece 121 (so as to detect whether the adhesive tape is missed by CCD). Such a setting can avoid the risk that the first pole piece 121 expands too much and the protective layer 150 cannot cover the edge of the first current collector 1211.

[0131] In some alternative embodiments, the protective layer 150 is an adhesive layer or a ceramic layer.

[0132] In some embodiments, at specific positions on both side edges of the first pole piece 121, part of the depth of the first active material layer 1212 is removed by laser cleaning. An adhesive solution (PVDF adhesive solution or others) is sprayed on the area where the first active material layer 1212 is cleaned. The sprayed adhesive solution adheres to the surface of the first active material layer 1212. After drying after spraying, a glue film is formed to inhibit and block the extraction and diffusion of positive lithium ions in this area. The total depth of the surface glue layer and the bottom first active material layer 1212 in the sprayed area shall not exceed the depth of the other double-sided first active material layer 1212 area so as not to affect the depth of the first pole piece 121.

[0133] In some other embodiments, the ceramic layer can be a ceramic slurry layer or a ceramic adhesive solution layer.

[0134] Specifically, the spraying of the adhesive solution can be changed to the spraying of ceramic slurry or ceramic adhesive solution, and the others are the same as above.

[0135] It should be noted that for small-area adhesive pasting, higher requirements are imposed on the adhesive pasting equipment. During mass production, the production efficiency is higher and the cost is lower when using sprayed adhesive solution or ceramic slurry. The spraying area needs to be limited within the first groove 130, and the distance from each side to the edge of the first groove 130 is 0 mm to 2 mm, and it cannot reach the paste coating in the normal area.

[0136] Among them, the protective layer 150 can be a rubber adhesive tape, an acrylic adhesive tape, a polypropylene adhesive tape or an SIS (Styrene-Isoprene-Styrene) adhesive tape, etc., and is not limited uniquely here.

[0137] In other embodiments, the protective layer 150 can also be an adhesive layer, for example, a rubber adhesive layer, an acrylic adhesive layer, a polypropylene adhesive layer, or a styrene-isoprene-styrene (SIS) adhesive layer, etc., which is not uniquely limited herein.

[0138] Figure 11 FIG. is a schematic structural diagram of another battery cell provided by an embodiment of the present invention. Figure 12 FIG. is a cross-sectional view of a winding core in another battery cell provided by an embodiment of the present invention.

[0139] As Figure 11 and Figure 12 shown, in some alternative embodiments, the thinning portion further includes a plurality of second grooves 140 formed in the second pole piece 122, and the plurality of second grooves 140 are located on opposite sides of the second pole piece 122 along the second direction.

[0140] It should be noted that the second grooves 140 are symmetrically arranged along the second direction at the edge of the second pole piece 122 and are spaced along the winding direction of the winding core. The winding direction of the winding core can be the length direction of the second pole piece 122. Among them, Z represents the winding direction of the winding core.

[0141] In some embodiments, the second grooves 140 penetrate through opposite sides of the second pole piece 122 along the third direction, and the arrangement manner of the first grooves 130 can be referred to.

[0142] In some other embodiments, the second pole piece 122 is provided with a second current collector 1221 and a second active material layer 1222 formed on at least one surface of the second current collector 1221; the second grooves 140 are formed in the second active material layer 1222, and the arrangement manner of the first grooves 130 in this embodiment can also be referred to.

[0143] Among them, the second active material layer 1222 includes, but is not limited to, one or more of natural graphite, artificial graphite, mesophase carbon microspheres, lithium titanate, silicon negative electrode, silicon-carbon negative electrode, and alloy negative electrode.

[0144] It should be noted that the second current collector 1221 is a high-strength copper foil current collector, and its tensile strength is 300 MPa - 700 MPa, elongation is 2.0% - 11%, and surface density is 30 g / m2 - 65 g / m2. The purpose can effectively improve the problem that the second current collector 1221 breaks due to the stress difference generated during welding melting during the welding process; at the same time, it can also effectively reduce the burrs at the welding points, reduce the piercing risk, and at the same time increase the tensile force value at the welding point, reduce the contact impedance, and reduce the internal resistance of the winding core.

[0145] In some other embodiments, the positive electrode binder is mainly a polyvinylidene fluoride (PVDF) - based binder, and the negative electrode binder is mainly styrene-butadiene rubber.

[0146] Among them, the conductive agent includes at least one of conductive carbon black, Ketjen black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0147] In some alternative embodiments, the area of the second groove 140 is smaller than the area of the first groove 130;

[0148] When the first pole piece 121 and the second pole piece 122 are wound, the second pole piece 122 covers the first groove 130, and the distance between the width edges of the second pole piece 122 and the width edges of the first pole piece 121 is greater than or equal to 1 mm.

[0149] It should be noted that the second groove 140 may or may not be provided on the second pole piece 122. When it is provided, the position and the setting method of the second groove 140 may refer to the first groove 130, which will not be elaborated here too much. However, it is necessary to ensure that the area of the second groove 140 is smaller than the area of the first groove 130, and the distance between the edges of the second pole piece 122 and the edges of the first pole piece 121 after winding is greater than or equal to 1 mm to avoid lithium plating.

[0150] In some alternative embodiments, the ratio of the notch area of the first groove 130 to the notch area of the second groove 140 is greater than or equal to 105% and less than or equal to 200%;

[0151] The distance between the edge of the second pole piece 122 and the edge of the first pole piece 121 is greater than or equal to 2 mm.

[0152] It should be noted that the specific value can be adjusted according to the actual situation. To avoid lithium plating, the ratio of the area of the first groove 130 to the area of the second groove 140 is greater than or equal to 105%.

[0153] Figure 13 This is the structural schematic diagram of the fourth first pole piece provided by the embodiment of the present invention, Figure 14 This is the structural schematic diagram of the fifth first pole piece provided by the embodiment of the present invention, Figure 15 This is the structural schematic diagram of the sixth first pole piece provided by the embodiment of the present invention, Figure 16 This is the structural schematic diagram of the seventh first pole piece provided by the embodiment of the present invention.

[0154] As Figures 13 to 16 shown, in some alternative embodiments, the inner wall surface of the thinning portion includes at least one of an arc surface and a flat surface.

[0155] It should be noted that the edge of the thinning portion can be arc-shaped. Compared with a right-angle edge, the burr of the punching section is smaller for the arc-shaped edge, and it is not easy to pierce the separator 127, reducing the short-circuit rate of the wound core.

[0156] In some embodiments, the thinning portion may be formed by an arc segment, a straight segment, or a combination of an arc segment and a straight segment.

[0157] Exemplarily, the cross-section of the thinning portion is one of a semi-circular corner rectangle, a semi-circle, a sector, an ellipse, a basin shape, and a rectangle. As long as the thinning portion can prevent the first pole piece 121 from piercing the end corner of the housing 110 after expansion, protecting the end corner of the housing 110 is achieved.

[0158] As Figures 3 to 16 shown, in some alternative embodiments, along the winding direction of the core, both the first pole piece 121 and the second pole piece 122 have a starting end 125 and a terminating end 126, and the thinning portion is located at the terminating end 126 of at least one of the first pole piece 121 and the second pole piece 122.

[0159] It should be noted that the starting end 125 of the first pole piece 121 and the second pole piece 122 is the starting end 125 of the battery cell 100, and the starting end 125 of the battery cell 100 is located inside the lithium-ion battery. The terminating end 126 of the first pole piece 121 and the second pole piece 122 is the terminating end 126 of the battery cell 100 and is located outside the lithium-ion battery. Among them, the winding direction of the battery cell 100 is the extending direction from the starting end 125 to the terminating end 126 of the battery cell 100.

[0160] In addition, the present utility model can be applied to wound square battery cells and multi-tab wound square battery cells. Whether it is conventional winding or multi-tab winding, the thinning portion is located at the arc of the core after winding, and the tabs are generally wound near the middle of the core.

[0161] In some alternative embodiments, along the second direction, the ratio of the width of the thinning portion to the width of the core 120 is greater than or equal to 1% and less than or equal to 30%.

[0162] It should be noted that the ratio of the width of the single-sided first groove 130 to the width of the first pole piece 121 is 1%-30%. Exemplarily, the width range of the first groove 130 to the width of the first pole piece 121 is 2-10%.

[0163] In some alternative embodiments, when the first pole piece 121 and the second pole piece 122 are wound, the core has multiple layers, at least two layers of the first pole piece 121 are provided with a thinning portion, and the positions of the thinning portions in at least two layers of the first pole piece 121 correspond to each other; and / or,

[0164] At least two layers of the second pole piece 122 are provided with a thinning portion, and the positions of the thinning portions in at least two layers of the second pole piece 122 correspond to each other.

[0165] It should be noted that for the wound cell 100, the minimum number of layers with thinning parts provided in the first electrode sheet 121 is two layers to ensure that there is at least one missing layer at the four corners.

[0166] Among them, the ratio of the number of layers with thinning parts to the total number of layers is 5%-50%, and the preferred range is 5%-20%.

[0167] It should be noted that the thinning part can be a groove, and thus the thinning part can include the first groove 130 and the second groove 140.

[0168] It should be noted that the following will be described through several embodiments and comparative examples.

[0169] Example 1:

[0170] The first step: Prepare the positive electrode active material slurry, coat the positive electrode active material on the surface of the aluminum foil, and obtain the positive electrode sheet through baking, rolling, and slitting.

[0171] The preparation method of the positive electrode active material coating provided in this embodiment is as follows: After uniformly mixing the conductive agent and the PVDF solution, then add lithium cobaltate and stir evenly to obtain the positive electrode active material layer slurry.

[0172] The above positive electrode active material layer is composed of 97.6 parts by mass of lithium cobaltate, 1.05 parts by mass of PVDF, and 1.35 parts by mass of the conductive agent. Among them, the conductive agent is composed of conductive carbon black, single-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0173] The second step: Prepare the negative electrode slurry, coat the negative electrode slurry on the copper foil with carbon coating, and obtain the negative electrode sheet through baking, rolling, and slitting.

[0174] Among them, the preparation method of the negative electrode active material coating is as follows: After uniformly mixing 0.5% by mass of the conductive agent and 97% by mass of the graphite powder, then add deionized water, 1.3% by mass of carboxymethyl cellulose, and 1.2% by mass of styrene-butadiene rubber binder and stir evenly to obtain the negative electrode active material layer slurry.

[0175] The third step: Make thinning parts on both sides of the positive electrode sheet. The positions of the thinning parts are all at the last few folds of the tail of the electrode sheet and corresponding to the arc of the winding core. The shape of the first groove 130 is a semi-circular rectangle, with a length of 10 mm and a width of 5 mm. The number of the first grooves 130 accounts for 10% of the total number of folds of the cell; there is no groove on the negative electrode sheet (the manufacturing method of the second groove 140 can refer to the first groove 130).

[0176] The fourth step: The positive and negative electrode sheets are made into a winding core through sheet making and winding. The winding core is encapsulated, baked, injected with electrolyte, formed, second-sealed, sorted, OCV tested, and packaged to obtain a lithium-ion battery.

[0177] Step 5: Conduct a cycling test on the lithium-ion battery. During the cycling test, pay attention to observing the appearance of the battery, such as the cracking situation at the four corners and the bulging and leakage of liquid.

[0178] Example 2

[0179] In this example, only the folding ratio of the first groove 130 is changed from 10% to 5%, and the others are the same as in Example 1.

[0180] Example 3

[0181] In this example, only the folding ratio of the first groove 130 is changed from 10% to 20%, and the others are the same as in Example 1.

[0182] Example 4

[0183] In this example, only the length and width of the semi-circular corner rectangle of the first groove 130 are changed to: 12mm * 4mm, and the others are the same as in Example 1.

[0184] Example 5

[0185] In this example, only the shape of the first groove 130 is changed to a quarter-round rectangle, length * width: 5mm * 5mm. After winding, there are only grooves at the four corners of the deep pit surface of the wound core, and the others are the same as in Example 1.

[0186] Example 6

[0187] In this example, only the shape of the first groove 130 is changed to a semi-circular shape with a radius of 10mm, and the others are the same as in Example 1.

[0188] Example 7

[0189] In this example, only the shape of the first groove 130 is changed to a semi-circular shape with a radius of 13mm, and the others are the same as in Example 1.

[0190] Example 8

[0191] In this example, a semi-circular corner rectangle groove is also made on the negative electrode sheet, length * width: 8mm * 3mm, and the others are the same as in Example 1.

[0192] Comparative Example 1

[0193] In this comparative example, neither the first electrode sheet 121 nor the second electrode sheet 122 has a groove, and the others are the same as in Example 1.

[0194] Comparative Example 2

[0195] In this comparative example, neither the first electrode sheet 121 nor the second electrode sheet 122 has a groove, and the P-A GAP is increased from 1.2mm in Comparative Example 1 to 1.5mm, and the others are the same as in Comparative Example 1.

[0196] Comparative Example 3

[0197] In this comparative example, neither the first electrode tab 121 nor the second electrode tab 122 is die-cut, and the depth of the copper foil is increased from 4 μm to 6 μm. Other conditions are the same as those in Comparative Example 1.

[0198] Table 1 Comparison of Performance Data of Each Example and Comparative Example

[0199]

[0200] As can be seen from the above examples, making grooves on the edge of the first electrode tab can effectively improve the problem of corner cracking during the cycling of the battery cell (Examples 1 - 8 vs. Comparative Example 1); increasing the groove area and the proportion of the number of groove folds in the total number of folds can also effectively improve the problem of corner cracking during the cycling of the battery cell, but it will result in a certain loss of ED (Examples 6 - 7 vs. Example 4, Examples 1 and 3 vs. Example 2); using the method of making grooves on the edge of the first electrode tab to improve the corner breakage effect is significantly better than increasing the P - A GAP and using thick copper foil to improve the corner breakage, and the ED loss is smaller (Examples 1 - 5, 8 vs. Comparative Example 2 and Comparative Example 3).

[0201] The battery cell provided by the embodiment of the present invention includes a housing having an accommodation cavity; a wound core located in the accommodation cavity, the wound core including a wound first electrode tab, a separator, and a second electrode tab, the separator being located between adjacent first and second electrode tabs, and the first and second electrode tabs having opposite polarities; the first electrode tab has a thinning portion, and along the second direction, the thickness of the thinning portion is less than the thickness of the rest of the first electrode tab, and the thinning portion is opposite to the end corner position of the housing.

[0202] Through the setting of the thinning portion, the depth of the four corners of the corresponding wound core becomes smaller. During long - term cycling, there is a larger space reserved between the corner positions of the wound core of this special battery cell and the housing, and the expansion of the corner positions is smaller than that of the corner positions of a battery cell with a normal structure, and the extrusion stress on the corner positions is smaller. Due to the reduction of the extrusion stress, the problem of corner cracking that easily occurs in high - energy - density battery cells during long - term cycling is significantly improved, effectively extending the number of cycles before the battery cell shows corner cracking at the four corners, and even not showing corner cracking during long - term cycling, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the expansion stress but also can optimize the internal structure of the battery cell, improving the cycle stability and safety performance of the battery.

[0203] In addition, the embodiment of the present invention also provides a battery including the battery cell 100.

[0204] Among them, the specific structure, working principle, and function of the battery cell 100 have been described in detail in the foregoing embodiments, and will not be elaborated herein.

[0205] The battery provided by the embodiment of the present utility model, through the setting of the thinning part, makes the depth of the four corners of the corresponding core smaller. During long-term cycling, there is a larger space reserved between the core corners of this special battery cell and the housing, and the swelling of the core corners is smaller than that of the core corners of a battery cell with a normal structure, resulting in a smaller extrusion stress on the corners. Due to the reduction of the extrusion stress, the problem of corner cracking that easily occurs in high-energy-density battery cells during long-term cycling has been significantly improved, effectively extending the number of cycles before the battery cell shows corner cracking at the four corners. In fact, corner cracking may not occur even during long-term cycling, thereby improving the overall service life of the battery cell. The larger reserved space not only reduces the swelling stress but also may optimize the internal structure of the battery cell, improving the cycling stability and safety performance of the battery.

[0206] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit them. Although the present utility model 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 for some or all of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A battery cell, characterized in that: include: A housing having a receiving cavity; A winding core, the winding core is located in the accommodating cavity, the winding core comprises a wound first pole piece, a diaphragm and a second pole piece, the diaphragm is located between the adjacent first pole piece and the second pole piece, and the first pole piece and the second pole piece have opposite polarities; The first pole piece has a thinned portion, and along the second direction, the thickness of the thinned portion is smaller than the thickness of the remaining position of the first pole piece, and the thinned portion is opposite to the end angle position of the shell.

2. The battery cell according to claim 1, characterized in that: Along the first direction, the orthographic projection of the end angle of the shell on the surface where the first pole piece provided with the thinned portion is located is located within the projection of the thinned portion.

3. The battery cell according to claim 2, characterized in that: The winding core has a straight area and a curved area, the curved area is located on one side of the straight area, the thinning portion is located in the curved area and extends toward the straight area, and the thinning portion covers at least a portion of the straight area.

4. The battery cell according to claim 3, characterized in that: The length of the thinned portion covering the straight area is greater than or equal to 1 mm and less than or equal to 3 mm.

5. The battery cell according to any one of claims 2 to 4, characterized in that: The first pole piece is located at the outermost layer of the winding core; The thinning portion includes a plurality of first grooves formed on the first pole piece, the plurality of first grooves being located on opposite sides of the first pole piece along a second direction, and an angle being formed between the first direction and the second direction.

6. The battery cell according to claim 5, characterized in that: The thinned portion includes a through hole, and the through hole penetrates two opposite sides of the first pole piece along a third direction.

7. The battery cell according to claim 5, characterized in that: The first pole piece is provided with a first current collector and a first active material layer, and the first active material layer is formed on at least one surface of the first current collector in a thickness direction; The first groove is opened on the first active material layer.

8. The battery cell according to claim 7, characterized in that: It also includes a protective layer, which is attached to the first groove and covers at least a portion of the bottom of the first groove.

9. The battery cell according to claim 8, characterized in that: Include at least one of the following: The thickness of the protective layer is smaller than the thickness of the first groove; Along the second direction, the edge of the protective layer exceeds the edge of the first groove, and the distance between the edge of the protective layer and the edge of the first groove is greater than or equal to 0.2 mm and less than or equal to 2 mm.

10. The battery cell according to claim 8, characterized in that: The protective layer includes a glue layer or a ceramic layer.

11. The battery cell according to claim 10, characterized in that: The ceramic layer includes a ceramic slurry layer or a ceramic glue layer; The adhesive layer is one of rubber adhesive tape, acrylic adhesive tape, polypropylene adhesive tape and styrene-isoprene-styrene adhesive tape.

12. The battery cell according to claim 5, characterized in that: The second pole piece has a thinned portion; The thinned portion further includes a plurality of second grooves formed on the second pole piece, and the plurality of second grooves are located on opposite sides of the second pole piece along a second direction.

13. The battery cell according to claim 12, characterized in that: The area of ​​the second groove is smaller than the area of ​​the first groove; The second pole piece covers the first groove, and a distance between a width edge of the second pole piece and a width edge of the first pole piece is greater than or equal to 1 mm.

14. The battery cell according to claim 13, characterized in that: The ratio of the notch area of ​​the first groove to the notch area of ​​the second groove is greater than or equal to 105% and less than or equal to 200%; A distance between an edge of the second pole piece and an edge of the first pole piece is greater than or equal to 2 mm.

15. The battery cell according to any one of claims 1 to 4, characterized in that: The inner wall surface of the thinned portion includes at least one of a curved surface and a flat surface.

16. The battery cell according to any one of claims 1 to 4, characterized in that: Along the winding direction of the winding core, the first pole piece and the second pole piece each have a starting end and a tail end, and the thinned portion is located at the tail end of at least one of the first pole piece and the second pole piece.

17. The battery cell according to any one of claims 1 to 4, characterized in that: A ratio between a width of the thinned portion and a width of the winding core is greater than or equal to 1% and less than or equal to 30%.

18. The battery cell according to claim 3 or 4, characterized in that: The winding core has multiple layers, the first pole pieces of at least two layers have the thinning portions, and the positions of the thinning portions in the first pole pieces of at least two layers correspond to each other; and / or, At least two layers of the second pole piece are provided with the thinning portion, and positions of the thinning portions of at least two layers correspond to each other.

19. A battery, characterized in that: Comprising the battery cell as described in any one of claims 1 to 18.

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