Negative plate, battery cell and battery

Abstract

The utility model relates to the technical field of batteries, in particular to a negative plate, a battery cell and a battery. The negative plate comprises a negative current collector; the negative pole lug is electrically connected with the negative pole current collector, the negative pole paste is arranged on at least one side surface of the negative pole current collector, a wire slot is formed in one side, deviating from the negative pole current collector, of the negative pole paste, and a first included angle theta 2 is formed between the extension direction of the wire slot and the edge of the negative pole paste; wherein the theta 2 is larger than 0 and smaller than 90 degrees, or the theta 2 is larger than 90 degrees and smaller than 180 degrees. According to the negative plate provided by the invention, the force on the edge of the negative paste, which is vertical to the extension direction of the wire slot, is reduced during hot pressing, so that the negative plate is not easy to fall powder, and the performance and safety of the battery are ensured.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a negative electrode sheet, a battery cell, and a battery. Background Art

[0002] With the advent of the 5G era and the rapid development of battery technology, people have put forward higher requirements for battery energy density, fast charging ability, and charge and discharge rate. Fast-charging lithium batteries with high energy density are also the development trend of consumer batteries.

[0003] Currently, the electrode sheet of a battery includes a current collector and an active material layer coated on the current collector. In order to improve its electrolyte wettability and charging rate, some batteries are provided with wire grooves on the side of the active material layer of the electrode sheet facing away from the current collector through a laser scribing process. The wire grooves provide additional channels for the transmission of lithium ions and electrolyte in the active material layer, and at the same time, the wire grooves can also reduce the weight of the electrode sheet.

[0004] However, the problem of edge powder falling easily occurs during the lamination process of the electrode sheet, which will affect the performance and safety of the battery. Summary of the Utility Model

[0005] Based on this, this application provides a negative electrode sheet, a battery cell, and a battery to solve the problem that the electrode sheet is prone to edge powder falling during the lamination process in the related art.

[0006] In a first aspect, this application provides a negative electrode sheet, including:

[0007] A negative current collector;

[0008] A negative tab, the negative tab is electrically connected to the negative current collector,

[0009] Negative paste, the negative paste is disposed on at least one side surface of the negative current collector, and wire grooves are provided on the side of the negative paste facing away from the negative current collector, and the extending direction of the wire grooves has a first included angle θ2 with the edge of the negative paste;

[0010] Wherein, the magnitude of θ2 satisfies:

[0011] 0 < θ2 < 90°, or, 90° < θ2 < 180°.

[0012] In a possible implementation manner, negative pastes are respectively disposed on two opposite surfaces in the thickness direction of the negative current collector, wire grooves are provided on the negative pastes on both sides of the negative current collector, and a second included angle exists between the extending direction of the wire grooves on the negative paste on one side of the negative current collector and the extending direction of the wire grooves on the negative paste on the other side of the negative current collector.

[0013] In a possible implementation manner, the tensile strength of the negative current collector ≥ 400 MPa, and the thickness of the negative current collector is 4 μm - 10 μm.

[0014] In a possible implementation, in the width direction of the negative electrode sheet, the thickness of the edge of the negative electrode paste is the same as that of the middle region of the negative electrode paste.

[0015] In a possible implementation, the negative electrode sheet further includes a ceramic layer on the side of the negative electrode paste facing away from the negative electrode current collector.

[0016] In a possible implementation, the depth of the wire groove is 5 μm - 40 μm; and / or,

[0017] the width of the wire groove is 50 μm - 200 μm; and / or,

[0018] the thickness of the negative electrode paste is 30 μm - 80 μm.

[0019] In a possible implementation, each wire groove includes at least one segment groove.

[0020] In a possible implementation, the negative electrode paste has a first covering portion extending to the negative electrode tab;

[0021] The end of the projection of the wire groove in the thickness direction of the negative electrode sheet extends to the edge of the negative electrode current collector facing the negative electrode tab;

[0022] Or, there is a gap between the end of the projection of the wire groove in the thickness direction of the negative electrode sheet and the edge of the negative electrode current collector facing the negative electrode tab;

[0023] Or, the end of at least part of the wire groove extends to the first covering portion.

[0024] In a second aspect, the present application further provides an electric core, including a positive electrode sheet, a separator, and the above-mentioned negative electrode sheet which are stacked, and a separator is disposed between adjacent positive electrode sheets and negative electrode sheets.

[0025] In a possible implementation, the side of the separator corresponding to the negative electrode sheet contains indentations;

[0026] and / or, the position of the separator corresponding to the concave portion of the negative electrode sheet contains indentations.

[0027] In a possible implementation, the peeling force between the positive electrode sheet and the separator is 0.7 N / m - 9 N / m;

[0028] and / or, there is a first peeling force between the region of the negative electrode paste outside the wire groove and the separator, and there is a second peeling force between the region of the negative electrode paste in the wire groove and the separator. The first peeling force is 0.8 N / m - 6 N / m, and the ratio of the second peeling force to the first peeling force is 0.9 - 0.99.

[0029] In a possible implementation, the outermost layer of the battery cell is the positive electrode sheet, the outermost positive electrode sheet is a single-sided pasted positive electrode sheet, and the positive electrode paste of the outermost positive electrode sheet is located on the side of the positive electrode current collector facing the adjacent negative electrode sheet. The thickness of the positive electrode current collector of the outermost positive electrode sheet is 8 μm - 20 μm; or,

[0030] the outermost layer of the battery cell is the negative electrode sheet, and the outermost negative electrode sheet is a single-sided pasted negative electrode sheet or a double-sided pasted negative electrode sheet; or,

[0031] the outermost layer of the battery cell is the separator, the outermost separator is adjacent to the negative electrode sheet, and the negative electrode sheet adjacent to the outermost separator is a double-sided pasted negative electrode sheet.

[0032] In a possible implementation, the outermost layer of the battery cell is the negative electrode sheet, the outermost negative electrode sheet is a single-sided pasted negative electrode sheet, the negative electrode paste of the outermost negative electrode sheet is located on the side of the negative electrode current collector facing the adjacent positive electrode sheet, and the thickness of the negative electrode current collector of the outermost negative electrode sheet is 8 μm - 20 μm.

[0033] In a possible implementation, the thickness of the battery cell is 2 mm - 3 mm, the number of upper grooves of the negative electrode paste is at least 2, the distance between two adjacent grooves is 0.5 mm - 5 mm, and the ratio of the distance between two adjacent grooves on the negative electrode paste to the thickness of the battery cell is 0.4 - 2.5.

[0034] In a possible implementation, the positive electrode sheet further includes an insulating coating provided on the positive electrode current collector. The insulating coating is located at the edge of the positive electrode sheet and is in contact with the positive electrode paste. At least a part of the projection of the groove in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell have an overlapping area;

[0035] or, the positive electrode sheet further includes an insulating coating provided on the positive electrode tab. The insulating coating is in contact with the positive electrode paste. At least a part of the projection of the groove in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell have an overlapping area.

[0036] In a third aspect, the present application further provides a battery, including the above-mentioned battery cell.

[0037] The negative electrode sheet, battery cell and battery provided by the present application are such that a wire groove is provided on the side of the negative electrode paste facing away from the negative electrode current collector, and the wettability of the electrolyte and the charging rate are improved through the wire groove. The extending direction of the wire groove has a first included angle θ2 with the edge of the negative electrode paste; wherein, the magnitude of θ2 satisfies: 0 < θ2 < 90°, or 90° < θ2 < 180°. That is to say, the extending direction of the wire groove forms an acute angle or an obtuse angle with the edge of the negative electrode paste. When the negative electrode sheet is stacked with the positive electrode sheet and the separator to form a battery cell, the hot pressing device will apply an extension force to the negative electrode sheet from the center to the periphery, and this force can be divided into two forces perpendicular to the extending direction of the wire groove and parallel to the extending direction of the wire groove. Compared with the case where the wire groove extends along the length direction or the width direction of the electrode sheet, for the negative electrode sheet provided by the present application, the force perpendicular to the extending direction of the wire groove on the edge of the negative electrode paste during hot pressing is reduced, and the negative electrode sheet is not likely to have powder falling off, ensuring the performance and safety of the battery. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application 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 application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0039] Figure 1 Schematic diagram of the structure of the negative electrode sheet in the related art Figure 1 ;

[0040] Figure 2 Schematic diagram of the structure of the first negative electrode sheet provided by the embodiment of the present application;

[0041] Figure 3 For Figure 2 Partial enlarged schematic diagram;

[0042] Figure 4 Cross-sectional view of the negative electrode sheet provided by the embodiment of the present application;

[0043] Figure 5 Schematic diagram of the structure of the second negative electrode sheet provided by the embodiment of the present application;

[0044] Figure 6 Schematic diagram of the structure of the third negative electrode sheet provided by the embodiment of the present application;

[0045] Figure 7 Schematic diagram of the structure of the fourth negative electrode sheet provided by the embodiment of the present application;

[0046] Figure 8 Schematic diagram of the structure of the battery cell provided by the embodiment of the present application Figure 1 ;

[0047] Figure 9 Structural schematic of the battery cell provided by the embodiment of the present application Figure 2 ;

[0048] Figure 10 Structural schematic of the battery cell provided by the embodiment of the present application Figure 3 ;

[0049] Figure 11 Microscopic image of the separator provided by the embodiment of the present application.

[0050] Description of reference numerals:

[0051] 100 - positive electrode sheet;

[0052] 200 - negative electrode sheet; 210 - negative electrode tab; 220 - negative electrode paste; 221 - wire groove; 222 - first covering part; 230 - ceramic layer;

[0053] 300 - separator. Detailed implementation manners

[0054] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar components or components with the same or similar functions throughout. The described embodiments are some but not all of the embodiments of the present application. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0055] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it may be a fixed connection, or an indirect connection through an intermediate medium, or the internal connection or interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0056] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present application.

[0057] In the description and claims of this application and the above-mentioned drawings, the terms "first", "second", "third" (if any) are used to distinguish similar objects and do not necessarily describe a specific order or sequence.

[0058] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or display comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or displays.

[0059] In the prior art, as Figure 1 shown, in order to improve the electrolyte wettability and charge rate of some batteries, wire grooves 221 are provided on the side of the active material layer of the electrode plate facing away from the current collector through a laser scribing process. The wire grooves 221 extend along the length or width direction of the electrode plate, and the included angle θ1 between the extending direction of the wire grooves 221 and the paste edge is 90° or 180°. When laminating and hot pressing the electrode plate, the hot pressing equipment will apply an extension force from the center to the periphery to each electrode plate. This force can be divided into two forces perpendicular and parallel to the extending direction of the wire grooves 221. Among them, the force perpendicular to the extending direction of the wire grooves 221 is the main reason for the powder falling off of the electrode plate. Figure 1 It is shown that at the top or bottom edge of the electrode plate, the force received by the paste edge perpendicular to the extending direction of the wire grooves 221 is the nearly complete force F, which easily causes the powder to fall off the electrode plate and affects the performance and safety of the battery.

[0060] After repeated thinking and verification, the inventor found that if the wire grooves on the electrode plate are set to extend along a direction inclined to the paste edge, and the extending direction of the wire grooves is not perpendicular or parallel to the paste edge. When laminating the battery cells, the force perpendicular to the extending direction of the wire grooves received at the edge of the electrode plate is the component force F1 or F2 of the complete force F, and both F1 and F2 are smaller than F, that is, the magnitude of the force perpendicular to the extending direction of the wire grooves received at the edge of the electrode plate is reduced, making it not easy for the electrode plate to have powder falling off, thereby ensuring the performance and safety of the battery.

[0061] In view of this, the inventor designed a negative electrode plate, a battery cell and a battery. The negative electrode plate improves the electrolyte wettability and charge rate by providing wire grooves on the negative electrode paste. The extending direction of the wire grooves has a first included angle θ2 with the edge of the negative electrode paste, and the magnitude of θ2 satisfies: 0 < θ2 < 90°, or, 90° < θ2 < 180°. In this way, the extending direction of the wire grooves is inclined to the edge of the negative electrode paste and is not perpendicular to the edge of the negative electrode paste. The magnitude of the force perpendicular to the extending direction of the wire grooves received at the edge of the electrode plate is reduced, making it not easy for the electrode plate to have powder falling off, thereby ensuring the performance and safety of the battery.

[0062] The technical solutions of the negative electrode sheet, the battery cell, and the battery provided in the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0063] Referring to Figures 2 - 3 As shown, the negative electrode sheet 200 provided in the embodiments of the present application includes a negative electrode current collector, a negative electrode tab 210, and a negative electrode paste 220. The negative electrode tab 210 is electrically connected to the negative electrode current collector. The negative electrode paste 220 is disposed on at least one side of the negative electrode current collector, and a wire groove 221 is provided on the side of the negative electrode paste 220 facing away from the negative electrode current collector. There is a first included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220, where the magnitude of θ2 satisfies: 0 < θ2 < 90°, or 90° < θ2 < 180°.

[0064] For example, the magnitude of θ2 can be 10°, 25°, 45°, 65°, 80°, 100°, 120°, 150°, 170°, etc., which is not uniquely limited herein. Exemplarily, a copper foil or a composite current collector can be used as the negative electrode current collector. Optionally, the negative electrode tab 210 and the negative electrode current collector can be an integral part. During the processing of the negative electrode sheet 200, the foil material can be die-cut to form the negative electrode current collector and the negative electrode tab 210.

[0065] In this embodiment, the negative electrode sheet 200 can be a single-sided coated negative electrode sheet or a double-sided coated negative electrode sheet, that is, the negative electrode paste 220 can be provided only on one side of the negative electrode current collector, or the negative electrode paste 220 can be provided on both sides of the negative electrode current collector respectively, which is not uniquely limited herein.

[0066] In a possible implementation manner, the thickness of the negative electrode paste 220 is 30 μm - 80 μm.

[0067] Specifically, the thickness of the negative electrode paste 220 on one side of the negative electrode current collector is 30 μm - 80 μm. Exemplarily, the thickness of the negative electrode paste 220 can be 30 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, etc., which is not uniquely limited herein. When the thickness of the negative electrode paste 220 is less than 30 μm, the capacity of the battery is low; when the thickness of the negative electrode paste 220 is greater than 80 μm, the wettability of the electrolyte and the charging rate of the battery are low. That is, the thickness of the negative electrode paste 220 can ensure the battery capacity while also ensuring the wettability of the electrolyte and the charging rate of the battery.

[0068] Schematically, the wire groove 221 can be formed on the side of the negative electrode paste 220 facing away from the negative electrode current collector by means of laser scribing. Among them, the number of wire grooves 221 on the negative electrode paste 220 can be multiple to reliably improve the wettability of the electrolyte and the charging rate.

[0069] Among them, the cross section of the line groove 221 presents different shapes according to the different light sources during laser scribing. If the light source for laser scribing is a flat-top light, the cross section of the line groove 221 is a rectangle or a trapezoidal shape that is approximately rectangular; if the light source for laser scribing is a Gaussian light source with concentrated energy, the cross section of the line groove 221 presents a narrower "U" shape or an inverted trapezoid; if the light source for laser scribing is a Gaussian light source with more dispersed energy, the cross section of the line groove 221 presents a wider "U" shape or an inverted trapezoid. The line groove 221 is also conducive to the embedding and de-embedding of lithium ions, which is conducive to improving the capacity retention rate of the battery after long cycles.

[0070] The extension direction of the wire groove 221 is the length direction of the wire groove 221. It can be understood that the first angle between the extension direction of the wire groove 221 and the edge of the negative electrode paste 220 can be an obtuse angle or an acute angle. This embodiment does not limit the specific size of θ2, and those skilled in the art can set it as needed.

[0071] It should be noted that when the negative electrode sheet 200 is stacked with the positive electrode sheet 100 and the separator 300 to form a battery cell, the hot pressing equipment will give the negative electrode sheet 200 an extension force from the center to the surrounding area. This force can be divided into two forces, one perpendicular to the extension direction of the wire groove 221 and the other parallel to the extension direction of the wire groove 221. The force perpendicular to the extension direction of the wire groove 221 is the main reason for the powder falling off the edge of the electrode sheet. Figure 2 and Figure 3 It is shown that the extension force given to the negative electrode 200 by the hot pressing equipment is F. When the angle between the extension direction of the wire groove 221 and the edge of the electrode is an acute angle or an obtuse angle, when the battery cell is stacked, the force perpendicular to the extension direction of the wire groove 221 on the edge of the paste is the component force F1 or F2 of the complete force F. Both F1 and F2 are smaller than F, which means that the magnitude of the force perpendicular to the extension direction of the wire groove 221 on the edge of the electrode is reduced.

[0072] The negative electrode sheet 200 provided in this embodiment is provided with a wire groove 221 on the side of the negative electrode paste 220 facing away from the negative electrode current collector, and the wettability of the electrolyte and the charging rate are improved through the wire groove 221. There is a first included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220; wherein, the magnitude of θ2 satisfies: 0 < θ2 < 90°, or, 90° < θ2 < 180°. That is to say, the extending direction of the wire groove 221 forms an acute angle or an obtuse angle with the edge of the negative electrode paste 220. When the negative electrode sheet 200 is stacked with the positive electrode sheet 100 and the separator 300 to form an electric core, the hot pressing device will apply an extension force to the negative electrode sheet 200 from the center to the periphery, and this force can be divided into two forces perpendicular to the extending direction of the wire groove 221 and parallel to the extending direction of the wire groove 221. Compared with the case where the wire groove 221 extends along the length direction or the width direction of the electrode sheet, the negative electrode sheet 200 provided in this application reduces the force perpendicular to the extending direction of the wire groove 221 on the edge of the negative electrode paste 220 during hot pressing, so that the force perpendicular to the extending direction of the wire groove 221 is not likely to cause powder falling off of the negative electrode sheet 200, ensuring the performance of the battery and improving the safety of the battery at the same time.

[0073] Schematically, the depth of the wire groove 221 is 5 μm - 40 μm.

[0074] For example, the depth of the wire groove 221 can be 5 μm, 10 μm, 15 μm, 30 μm, 35 μm or 40 μm, etc., and those skilled in the art can set it according to needs. When the depth of the wire groove 221 is less than 5 μm, the improvement effect of the wire groove 221 on the wettability of the electrolyte and the charging rate is small; when the depth of the wire groove 221 is greater than 40 μm, the negative electrode paste 220 loses too much active material at the position of the wire groove 221, resulting in too much reduction in the battery capacity. That is to say, the above settings can ensure the improvement effect of the wire groove 221 on the wettability of the electrolyte and the charging rate, and can also ensure the battery capacity.

[0075] Optionally, the width of the wire groove 221 is 50 μm - 200 μm.

[0076] Among them, the width direction of the wire groove 221 is perpendicular to the extension direction of the wire groove 221, and the width of the wire groove 221 is the width at the widest position of the wire groove 221. For example, the width of the wire groove 221 can be 50μm, 80μm, 100μm, 120μm, 150μm, 180μm, 200μm, etc., and there is no unique limitation here. When the width of the wire groove 221 is less than 50μm, the wettability of the electrolyte by the wire groove 221 and the improvement effect on the charging rate are small; when the width of the wire groove 221 is greater than 200μm, the negative electrode paste 220 loses more active substances at the position of the wire groove 221, resulting in too much reduction in the battery capacity. That is, the width of the wire groove 221 can ensure the battery capacity while ensuring the wettability of the electrolyte by the wire groove 221 and the improvement effect on the charging rate.

[0077] Schematically, each wire groove 221 includes at least one segment groove.

[0078] Specifically, the wire groove 221 can be entirely composed of one segment groove, or the wire groove 221 can also include multiple segment grooves. When the wire groove 221 includes multiple segment grooves, the multiple segment grooves can be spliced together, that is, the connection points between adjacent two segment grooves can be continuous. Or, when the wire groove 221 includes multiple segment grooves, there can be discontinuous points between adjacent two segment grooves. Optionally, the distance between adjacent two segment grooves can be fixed.

[0079] With this structure, when it is necessary to set a short wire groove 221 on the negative electrode sheet 200 by means of laser scribing, it can be completed by one laser; when it is necessary to set a long wire groove 221 on the negative electrode sheet 200 by means of laser scribing, it can be completed jointly by multiple lasers. The compatibility of the processing of the wire groove 221 is relatively high.

[0080] In a possible implementation manner, the negative electrode current collector is provided with the negative electrode paste 220 on both sides in the thickness direction, and the wire grooves 221 are provided on the negative electrode paste 220 on both sides of the negative electrode current collector. There is a second included angle between the extension direction of the wire groove 221 on the negative electrode paste 220 on one side of the negative electrode current collector and the extension direction of the wire groove 221 on the negative electrode paste 220 on the other side of the negative electrode current collector.

[0081] That is to say, the negative electrode sheet 200 is a double-sided coated negative electrode sheet, and the extension directions of the wire grooves 221 on the two negative electrode pastes 220 of the negative electrode sheet 200 are different. Specifically, the projection of the wire groove 221 on one of the negative electrode pastes 220 of the negative electrode sheet 200 in the thickness direction of the negative electrode sheet 200 is inclined to the projection of the wire groove 221 on the other negative electrode paste 220 of the negative electrode sheet 200 in the thickness direction of the negative electrode sheet 200.

[0082] Through the above settings, it is possible to avoid the situation where the wire grooves 221 on the two negative electrode pastes 220 of the negative electrode sheet 200 completely overlap, resulting in an overall too thin thickness of the negative electrode sheet 200 at the position of the negative electrode paste 220 and affecting the tensile strength of the negative electrode sheet 200.

[0083] In a specific embodiment, the size of the second included angle is 90°. Exemplarily, the first included angles θ2 between the extending directions of the wire grooves 221 on the two negative electrode pastes 220 of the negative electrode sheet 200 and the edges of the negative electrode paste 220 can be 45° and 135° respectively. The above settings facilitate setting the extending direction of the wire grooves 221 while ensuring the tensile strength of the negative electrode sheet 200, and further facilitate setting the wire grooves 221 on the negative electrode paste 220, so as to improve the production efficiency of the negative electrode sheet 200.

[0084] In a possible implementation manner, the tensile strength of the negative electrode current collector > 400 MPa, and the thickness of the negative electrode current collector is 4 μm - 10 μm.

[0085] For example, when using copper foil as the negative electrode current collector, the copper foil used is a high-strength copper foil with a tensile strength > 400 MPa. Optionally, the tensile strength of the negative electrode current collector can be 450 MPa, 500 MPa, 600 MPa, 650 MPa or 700 MPa, etc., and can be specifically set according to needs. Among them, the thickness of the negative electrode current collector can be 4 μm, 5 μm, 6 μm, 8 μm, 9 μm or 10 μm, etc., and is not uniquely limited here. When the thickness of the negative electrode current collector is less than 4 μm, the tensile strength of the negative electrode current collector is small; when the thickness of the negative electrode current collector is greater than 10 μm, the negative electrode current collector is relatively thick, and the negative electrode current collector occupies a relatively large thickness of the battery core, resulting in a decrease in the energy density of the battery.

[0086] Through the above settings, the stability and strength of the internal structure of the battery can be increased, and the negative electrode sheet 200 can remain unchanged when experiencing a large mechanical force, protecting the battery structure from damage. At the same time, the negative electrode current collector does not occupy a relatively large thickness of the battery core, ensuring the energy density of the battery.

[0087] Schematically, after coating the negative electrode paste 220 on the negative electrode current collector and the negative electrode tab 210, the negative electrode paste 220 can be scored to form the wire grooves 221 first, and then the negative electrode paste 220 at the position of the negative electrode tab 210 can be cleaned, or the negative electrode paste 220 at the position of the negative electrode tab 210 can be cleaned first, and then the negative electrode paste 220 can be scored to form the wire grooves 221. If scoring is done first and then cleaning, there will be no scratches on the copper foil; if cleaning is done first and then scoring, there may be scoring marks on the copper foil.

[0088] In a specific embodiment, in the width direction of the negative electrode sheet 200, the thickness of the edge of the negative electrode paste 220 is the same as that of the middle region of the negative electrode paste 220.

[0089] In the related art, after the slurry of the negative electrode paste 220 is coated on the negative electrode current collector, under the action of the fluidity and surface tension of the slurry, at the edge in the width direction of the negative electrode sheet 200, the thickness of the negative electrode paste 220 will be thinner than that of other regions, forming a gradient distribution structure, that is, a flat region and a thinning region located on one side of the flat region facing the edge of the negative electrode sheet 200 are formed on the negative electrode sheet 200.

[0090] For the battery cell provided in this embodiment, its electrode sheet is continuously coated, and after coating, a laser cleaning method is adopted at the tab position, so that there is no gradient distribution thinning region at the tab position, that is, a nearly vertical zero-thinning structure. The thinning regions at other positions of the foil can be removed by die-cutting, so that there is no thinning region on the negative electrode current collector either. In this way, the thickness of the negative electrode paste 220 on the negative electrode current collector and the negative electrode tab 210 is consistent.

[0091] In this structure, the negative electrode paste 220 does not have a thinning region, which ensures the amount of negative electrode active material on the negative electrode current collector and is beneficial to ensuring the capacity of the battery. Since the negative electrode paste 220 on the negative electrode tab 210 does not play a role in charge and discharge, removing the thinning region on the negative electrode tab 210 can reduce the weight of the negative electrode sheet 200 and is beneficial to improving the energy density of the battery.

[0092] As Figure 4 shown, in one embodiment, the negative electrode sheet 200 further includes a ceramic layer 230 located on the side of the negative electrode paste 220 facing away from the negative electrode current collector.

[0093] Schematically, the projection of the ceramic layer 230 in the thickness direction of the negative electrode sheet 200 covers the projection of the negative electrode paste 220 in the thickness direction of the negative electrode sheet 200. Optionally, after a wire groove 221 is provided on the negative electrode paste 220, the ceramic layer 230 can be provided on the side of the negative electrode paste 220 facing away from the negative electrode current collector by coating. After the wire groove 221 is provided on the negative electrode paste 220, if the wire groove 221 is relatively shallow or the ceramic layer 230 is relatively thick, the trace of the wire groove 221 cannot be seen on the ceramic layer 230; if the wire groove 221 is relatively deep or the ceramic layer 230 is relatively thin, the trace of the wire groove 221 can be faintly seen on the ceramic layer 230. Exemplarily, as Figure 4 shown, when the negative electrode paste 220 is provided on both sides of the negative electrode current collector of the negative electrode sheet 200, that is, the negative electrode sheet 200 is a double-sided coated negative electrode sheet, ceramic layers 230 are respectively provided on the sides of the two negative electrode pastes 220 of the negative electrode sheet 200 facing away from the negative electrode current collector.

[0094] In this embodiment, the ceramic layer 230 on the negative electrode sheet 200 can isolate the positive electrode sheet 100 from the negative electrode sheet 200, that is, the ceramic layer 230 on the negative electrode sheet 200 can act as a separator. The ceramic layer 230 on the negative electrode sheet 200 can replace the separator, so that the battery cell can be without a separator, simplifying the structure of the battery cell, reducing the risk of the separator being corroded after long-term use, and improving the safety of the battery.

[0095] As Figures 5 - 7 shown, the negative electrode paste 220 has a first covering portion 222 extending to the negative electrode tab 210. Among them, the first covering portion 222 can prevent the current density at the position of the negative electrode tab 210 from being too high, thus avoiding the situation of local overheating.

[0096] In a possible implementation manner, as Figure 5 shown, the end of the projection of the wire groove 221 in the thickness direction of the negative electrode sheet 200 extends to the edge of the negative electrode current collector facing the negative electrode tab 210.

[0097] It can be understood that the wire groove 221 on the negative electrode paste 220 does not extend to the first covering portion 222, that is, the negative electrode paste 220 on the negative electrode tab 210 is not provided with a wire groove 221. During the process of laser scribing the negative electrode paste 220 to form the wire groove 221, the laser will not hit the empty foil area of the negative electrode tab 210, that is, the area where the negative electrode tab 210 is not covered by the negative electrode paste 220, avoiding damage to the empty foil area of the negative electrode tab 210.

[0098] In another possible implementation manner, as Figure 6 shown, there is a gap between the end of the projection of the wire groove 221 in the thickness direction of the negative electrode sheet 200 and the edge of the negative electrode current collector facing the negative electrode tab 210, and the width of this gap is h1. The above setting can also avoid the laser hitting the empty foil area of the negative electrode tab 210 and causing damage to the empty foil area of the negative electrode tab 210.

[0099] As Figure 7 shown, at least part of the end of the wire groove 221 extends to the first covering portion 222. Among them, the width of the area where the first covering portion 222 is provided with the wire groove 221 is h2. The above setting is beneficial to improving the electrolyte infiltration speed in the area around the electrode tab.

[0100] This application also provides a battery cell. As Figure 8 , Figure 9 and Figure 10 shown, this battery cell includes a positive electrode sheet 100, a separator 300 and the above-mentioned negative electrode sheet 200 which are stacked. A separator 300 is provided between adjacent positive electrode sheets 100 and negative electrode sheets 200.

[0101] Among them, the battery cell provided in this embodiment is a stacked cell, where the positive electrode sheets 100 and the negative electrode sheets 200 are stacked alternately, and a separator 300 is provided between adjacent positive electrode sheets 100 and negative electrode sheets 200. Those skilled in the art can set the specific number of positive electrode sheets 100 and negative electrode sheets 200 according to needs, and no unique limitation is made here.

[0102] It is worth mentioning that in the thickness direction of the battery cell, the edges of the separator 300 respectively exceed the edges of the positive electrode sheet 100 and the negative electrode sheet 200. That is to say, a separator 300 is provided between adjacent positive electrode sheets 100 and negative electrode sheets 200, and the projections of the separator 300 in the stacking direction of the battery cell respectively cover the projections of the positive electrode sheet 100 and the negative electrode sheet 200 in the stacking direction of the battery cell. The separator 300 can prevent conductive contact between the positive electrode sheet 100 and the negative electrode sheet 200, avoid short circuit of the battery cell, and ensure the safety of the battery cell.

[0103] For the battery cell provided in this application, due to the adoption of the above-mentioned negative electrode sheet 200, the grooves 221 on the negative electrode sheet 200 enable the electrolyte to reliably infiltrate the negative electrode paste 220, ensuring the charging rate of the battery cell. The extending direction of the grooves 221 on the negative electrode sheet 200 is inclined to the edge of the negative electrode paste 220. During the stacking process of the battery cell, the force perpendicular to the extending direction of the grooves 221 acting on the edge of the negative electrode paste 220 is reduced, and the force perpendicular to the extending direction of the grooves 221 is not likely to cause powder falling off of the negative electrode sheet 200, and the performance and safety of the battery cell can be ensured.

[0104] In one embodiment, as Figure 11 shown, the side of the separator 300 corresponding to the negative electrode sheet 200 contains indentations. And / or, the separator 300 contains indentations at the positions corresponding to the concave portions of the negative electrode sheet 200.

[0105] Schematically, the positive electrode sheet 100, the separator 300, and the negative electrode sheet 200 will be hot-pressed using a hot-pressing device during the stacking process, and the positions where the separator 300 and the negative electrode paste 220 are in contact with each other will be pressed against each other under the action of the hot-pressing device. Among them, the pressure received by the area corresponding to the grooves 221 on the separator 300 is less than the pressure received by the areas corresponding to the other positions of the separator 300 and the negative electrode paste 220, and the pressure difference received by different areas on the separator 300 forms indentations on the separator 300.

[0106] Exemplarily, the width of the indentations can be close to the width of the grooves 221. For example, the width of the indentations can be between 50 μm and 150 μm.

[0107] Through the above settings, between the separator 300 and the corresponding negative electrode sheet 200, the electrolyte is more likely to infiltrate into the middle of the battery cell through the indentations on the separator 300, which is beneficial to improving the wettability of the middle area of the negative electrode sheet 200 corresponding to the separator 300.

[0108] Schematically, the peeling force between the positive electrode sheet 100 and the separator 300 is 0.7 N / m - 9 N / m.

[0109] For example, the peeling force between the positive electrode sheet 100 and the separator 300 can be 0.7 N / m, 0.73 N / m, 2.73 N / m, 3.5 N / m, 5.83 N / m, 7.5 N / m, 8.83 N / m, or 9 N / m, etc., and is not uniquely limited herein. Among them, after the positive electrode sheet 100 and the separator 300 are stacked on each other, hot pressing is performed by a hot pressing device to fix the positive electrode sheet 100 and the separator 300, and the peeling force between the positive electrode sheet 100 and the separator 300 can be controlled by setting the pressure applied by the hot pressing device.

[0110] When the peeling force between the positive electrode sheet 100 and the separator 300 is less than 0.73 N / m, the connection strength between the positive electrode sheet 100 and the separator 300 is poor, and displacement is likely to occur between the separator 300 and the positive electrode sheet 100, so that the separator 300 cannot isolate the positive electrode sheet 100 and the negative electrode sheet 200, resulting in a short circuit in the battery cell. When the peeling force between the positive electrode sheet 100 and the separator 300 is greater than 8.83 N / m, it indicates that the pressure applied by the hot pressing device is large after the positive electrode sheet 100 and the separator 300 are stacked on each other, and the pressure applied by the hot pressing device makes the surface of the positive electrode paste denser, affecting the wettability of the electrolyte on the positive electrode paste.

[0111] That is to say, the peeling force between the positive electrode sheet 100 and the separator 300 can ensure both the reliability of the connection between the positive electrode sheet 100 and the separator 300 and the wettability of the electrolyte on the positive electrode paste.

[0112] Schematically, the first peeling force exists between the negative electrode paste 220 in the area outside the wire groove 221 and the separator 300, and the second peeling force exists between the negative electrode paste 220 in the area of the wire groove 221 and the separator 300. The first peeling force is 0.8 N / m - 6 N / m, and the ratio of the second peeling force to the first peeling force is 0.9 - 0.99.

[0113] Specifically, after the positive electrode sheet 100, the negative electrode sheet 200, and the separator 300 are stacked to form a battery cell, the area of the negative electrode paste 220 where the wire groove 221 is not provided, that is Figure 2 the position A in the figure has the first peeling force with the separator 300, and the area of the negative electrode paste 220 where the wire groove 221 is provided, that is Figure 2There is a second peeling force between the position B in the middle and the separator 300. After the negative electrode sheet 200 and the separator 300 are stacked on each other, hot pressing is performed through a hot pressing device to fix the negative electrode sheet 200 and the separator 300. By setting the pressure applied by the hot pressing device, the magnitude of the first peeling force can be controlled. For example, the magnitude of the first peeling force can be 0.8 N / m, 1.5 N / m, 2.4 N / m, 3.5 N / m, 4.8 N / m, or 6 N / m, etc., and it is not uniquely limited here. The magnitude of the first peeling force can not only ensure the reliability of the connection between the area of the negative electrode paste 220 without the wire groove 221 and the separator 300, but also ensure that the electrolyte can easily infiltrate the area of the negative electrode paste 220 without the wire groove 221.

[0114] Since the wire groove 221 is provided on the negative electrode paste 220, the second peeling force is smaller than the first peeling force. By setting the depth of the wire groove 221, the ratio of the second peeling force to the first peeling force can be controlled. When the depth of the wire groove 221 is larger, the ratio of the second peeling force to the first peeling force is smaller; when the depth of the wire groove 221 is smaller, the ratio of the second peeling force to the first peeling force is larger. Optionally, the ratio of the second peeling force to the first peeling force can be 0.9, 0.92, 0.95, 0.96, 0.97, or 0.99, and it is not uniquely limited here.

[0115] It is worth mentioning that in the related art, the peeling force between the negative electrode sheet 200 and the separator 300 fluctuates periodically. If the pulling direction of the peeling force between the negative electrode sheet 200 and the separator 300 is perpendicular or parallel to a certain edge of the negative electrode paste 220, when the peeling force test peels to the area outside the wire groove 221, the peeling force between the negative electrode sheet 200 and the separator 300 is the same as that of the battery cell without the wire groove 221. When peeling to the area corresponding to the wire groove 221, the peeling force between the negative electrode sheet 200 and the separator 300 will suddenly decrease. However, the peeling force between the negative electrode sheet 200 and the separator 300 of the battery cell provided in this embodiment is relatively stable and will not fluctuate greatly, ensuring the reliable connection between the negative electrode sheet 200 and the separator 300.

[0116] The above settings ensure the reliability of the connection between the negative electrode sheet 200 and the separator 300, making it not easy for the negative electrode sheet 200 and the separator 300 to have relative displacement, and ensuring the safety of the battery. In addition, the above settings can also ensure the wettability of the area of the negative electrode paste 220 without the wire groove 221.

[0117] In a possible implementation, as Figure 8 shown, the outermost layer of the battery cell is the positive electrode sheet 100. The outermost positive electrode sheet 100 is a single-sided coated positive electrode sheet, and the positive electrode paste of the outermost positive electrode sheet 100 is located on the side of the positive electrode current collector facing the adjacent negative electrode sheet 200. The thickness of the positive electrode current collector of the outermost positive electrode sheet 100 is 8 μm - 20 μm.

[0118] Among them, the single-sided pasted positive electrode sheet, that is, the positive electrode sheet 100, has a positive electrode paste provided only on one side of the positive electrode current collector. It can be understood that in the stacking direction of the positive electrode sheet 100, the separator 300, and the negative electrode sheet 200, the positive electrode paste of the outermost positive electrode sheet 100 faces the inside of the battery cell.

[0119] Through the above settings, the positive electrode paste of each positive electrode sheet 100 in the battery cell is opposite to the negative electrode paste 220 of the negative electrode sheet 200, avoiding the situation that the lithium ions released by the positive electrode sheet 100 during the charging process cannot be received, resulting in the formation of lithium deposition on the surface of the negative electrode sheet 200 by the excess lithium ions.

[0120] Exemplarily, the thickness of the positive electrode current collector of the outermost positive electrode sheet 100 can be 8μm, 10μm, 12μm, 16μm, 18μm, 20μm, etc., and there is no unique limitation here. When the thickness of the positive electrode current collector of the outermost positive electrode sheet 100 is less than 8μm, the strength of the positive electrode current collector of the outermost positive electrode sheet 100 is small, the tensile strength of the outermost positive electrode sheet 100 is small, the protection effect of the positive electrode current collector of the outermost positive electrode sheet 100 on the battery cell is weak, and the battery cell is prone to damage; when the thickness of the positive electrode current collector of the outermost positive electrode sheet 100 is greater than 20μm, the positive electrode current collector of the outermost positive electrode sheet 100 occupies a relatively large thickness of the battery cell, affecting the energy density of the battery. That is to say, the positive electrode current collector of the outermost positive electrode sheet 100 can effectively protect the battery cell and at the same time ensure the energy density of the battery.

[0121] As Figure 9 shown, in another possible implementation, the outermost layer of the battery cell is the negative electrode sheet 200, and the outermost negative electrode sheet 200 is a single-sided pasted negative electrode sheet or a double-sided pasted negative electrode sheet.

[0122] Among them, the single-sided pasted negative electrode sheet means that the negative electrode sheet 200 has a negative electrode paste 220 provided only on one side of the negative electrode current collector, and the double-sided pasted negative electrode sheet means that the negative electrode sheet 200 has negative electrode pastes 220 provided on opposite sides of the negative electrode current collector respectively. In one possible implementation, the negative electrode paste 220 on the outermost negative electrode sheet 200 is provided with wire grooves 221.

[0123] The above settings can prevent the positive electrode paste of the positive electrode sheet 100 from being located on the outermost side of the battery cell, thereby avoiding the situation that excess lithium ions cannot be received by the negative electrode sheet 200 during the charging process of the battery, resulting in lithium deposition on the negative electrode sheet 200.

[0124] As Figure 10 shown, in yet another possible implementation, the outermost layer of the battery cell is the separator 300, the outermost separator 300 is adjacent to the negative electrode sheet 200, and the negative electrode sheet 200 adjacent to the outermost separator 300 is a double-sided pasted negative electrode sheet.

[0125] That is to say, the outermost negative electrode sheet 200 is provided with negative electrode pastes 220 on opposite sides of the negative electrode current collector. The outermost separator 300 can also protect the battery cell. The above arrangement can also prevent the positive electrode paste of the positive electrode sheet 100 from not having a corresponding negative electrode paste 220, and avoid the appearance of excess lithium ions during the charging process of the battery. In addition, the negative electrode paste 220 on the outermost negative electrode sheet 200 facing the outside of the battery cell can receive the excess lithium ions, further preventing the deposition of lithium on the negative electrode sheet 200.

[0126] As Figure 9 shown, in a possible implementation, the outermost layer of the battery cell is a negative electrode sheet 200, the outermost negative electrode sheet 200 is a single-sided pasted negative electrode sheet 200, the negative electrode paste 220 of the outermost negative electrode sheet 200 is located on the side of the negative electrode current collector facing the adjacent positive electrode sheet 100, and the thickness of the negative electrode current collector of the outermost negative electrode sheet 200 is 8 μm - 20 μm.

[0127] That is to say, when the outermost layer of the battery cell is a negative electrode sheet 200, the outermost negative electrode sheet 200 is provided with a negative electrode paste 220 only on one side of the negative electrode current collector, and the negative electrode paste 220 of the outermost negative electrode sheet 200 faces the inside of the battery cell. Exemplarily, the thickness of the negative electrode current collector of the outermost negative electrode sheet 200 can be 8 μm, 12 μm, 15 μm, 16 μm, 18 μm or 20 μm, etc., which is not uniquely limited here. When the thickness of the negative electrode current collector of the outermost negative electrode sheet 200 is less than 8 μm, the strength of the negative electrode current collector of the outermost negative electrode sheet 200 is small, the tensile strength of the outermost negative electrode sheet 200 is small, the protection effect of the negative electrode current collector of the outermost negative electrode sheet 200 on the battery cell is weak, and the battery cell is prone to damage; when the thickness of the negative electrode current collector of the outermost negative electrode sheet 200 is greater than 20 μm, the negative electrode current collector of the outermost negative electrode sheet 200 occupies a relatively large thickness of the battery cell, affecting the energy density of the battery. The negative electrode current collector of the outermost negative electrode sheet 200 can effectively protect the battery cell while ensuring the energy density of the battery.

[0128] In a possible implementation, the thickness of the battery cell is 2 mm - 3 mm. The number of wire grooves 221 on the negative electrode paste 220 is at least 2, and the distance between two adjacent wire grooves 221 is 0.5 mm - 5 mm. The ratio of the distance between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness of the battery cell is 0.4 - 2.5.

[0129] Among them, the thickness of the battery cell is 2 mm - 3 mm, indicating that the battery cell is a thin battery cell. The number of the wire grooves 221 is more than two, and the multiple wire grooves 221 can be arranged in parallel and at equal intervals on the negative electrode paste 220. The number of the wire grooves 221 on the negative electrode paste 220 is not restrictive, and those skilled in the art can set it according to needs. The multiple wire grooves 221 are arranged in parallel and at equal intervals on the negative electrode paste 220, so that the multiple wire grooves 221 can reliably improve the electrolyte wettability and the charging rate. Among them, the distance between two adjacent wire grooves 221 can be 0.5 mm, 1.5 mm, 2 mm, 3.5 mm, 4.2 mm or 5 mm, etc., and no unique limitation is made here. When the distance between two adjacent wire grooves 221 is less than 0.5 mm, the wire grooves 221 on the negative electrode paste 220 are too dense, resulting in a lower battery capacity; when the distance between two adjacent wire grooves 221 is greater than 5 mm, the wire grooves 221 on the negative electrode paste 220 are too sparse, and the improvement effect of the wire grooves 221 on the electrolyte wettability and the charging rate is small.

[0130] Exemplarily, the ratio of the distance between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness of the battery cell can be 0.4, 1.1, 1.5, 1.8, 2.2 or 2.5, etc., and no unique limitation is made here. When the ratio of the distance between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness of the battery cell is less than 0.4, it indicates that the distribution of the wire grooves 221 on the negative electrode paste 220 is relatively dense, reducing the battery capacity; when the ratio of the distance between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness of the battery cell is greater than 2.5, the improvement effect of the wire grooves 221 on the electrolyte wetting performance and the fast charging performance of the thin battery cell is small.

[0131] Through the above settings, while ensuring the fast charging performance of the thin battery cell, the battery capacity can also be ensured.

[0132] In a possible implementation manner, the positive electrode sheet 100 further includes an insulating coating provided on the positive electrode current collector. The insulating coating is located at the edge of the positive electrode sheet 100 and is in contact with the positive electrode paste, and there is an overlapping area between the projection of at least part of the wire grooves 221 in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell.

[0133] Among them, a ceramic coating can be used as the insulating coating. Specifically, the insulating coating is provided on the side of the positive electrode paste facing the positive electrode tab and is in contact with the positive electrode paste. Optionally, part of the insulating coating extends to the positive electrode tab. Those skilled in the art can set the width of the insulating coating on the positive electrode current collector and the width of the insulating coating on the positive electrode tab according to needs, and no unique limitation is made here. It can be understood that at least part of the wire grooves 221 extends beyond the positive electrode paste towards the negative electrode tab 210.

[0134] In another possible implementation, the positive electrode sheet 100 further includes an insulating coating provided on the positive electrode tab, the insulating coating is in contact with the positive electrode paste, and there is an overlapping area between the projection of at least part of the wire grooves 221 in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell.

[0135] It can be understood that the end of at least part of the wire grooves 221 facing the negative electrode tab extends beyond the edge of the positive electrode current collector, and there is an overlapping area between the projection of the part of the wire grooves 221 extending beyond the edge of the positive electrode current collector in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell.

[0136] By providing an insulating coating on the positive electrode sheet 100, during the die-cutting process of the positive electrode sheet 100, the end of the positive electrode tab connected to the positive electrode current collector is not likely to have burrs resulting in a short circuit of the battery cell. In addition, the insulating coating can also ensure that the edge of the negative electrode paste 220 extends beyond the edge of the positive electrode paste, avoiding lithium deposition at the edge of the negative electrode paste 220. There is an overlapping area between the projection of at least part of the wire grooves 221 in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell, ensuring that the area of the negative electrode paste 220 corresponding to the positive electrode paste is provided with wire grooves 221, thereby ensuring that the electrolyte can more easily infiltrate the area of the negative electrode paste 220 corresponding to the positive electrode paste, and at the same time reliably improving the fast charging performance of the battery cell.

[0137] The present application also provides a battery, including the above-mentioned battery cell.

[0138] For the battery provided by the present application, due to adopting the above-mentioned battery cell, its electrolyte can reliably infiltrate the negative electrode paste 220 of the negative electrode sheet 200, and the charging rate of the battery is relatively high. The negative electrode sheet 200 is not likely to have powder falling off, and the safety of the battery is relatively high.

[0139] Hereinafter, the negative electrode sheet 200, the battery cell and the battery of the present application will be introduced in detail through specific embodiments. The battery cell parameters of the following embodiments and comparative examples are recorded in Table 1.

[0140] Example 1

[0141] 1. Preparation of the positive electrode sheet 100

[0142] Lithium cobaltate, carbon black, and polyvinylidene fluoride are respectively mixed with NMP solvent according to the mass percentage contents of 97.2%, 1.5%, and 1.3% to obtain a positive electrode slurry. The above positive electrode slurry is coated on the surface of an aluminum foil current collector with a thickness of 6 μm, and the coating thickness of the positive electrode slurry is 35 μm. After drying, rolling and slitting, the positive electrode sheet 100 is obtained.

[0143] 2. Preparation of the negative electrode sheet 200

[0144] Artificial graphite, conductive carbon black, binder, and thickener are mixed with deionized water according to the mass percentages of 97%, 1.0%, 1.0%, and 1.0% respectively to obtain a negative electrode paste. The negative electrode paste is coated on the surface of a copper foil current collector. The thickness h3 of the copper foil current collector is 8 μm, and the coating thickness is 45 μm. After drying, rolling, and slitting, the negative electrode paste forms a negative electrode coating paste 220. A wire groove 221 is provided on one side of the negative electrode coating paste 220 facing away from the copper foil current collector through a laser scribing process. The included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode coating paste 220 is 45°. The depth h of the wire groove 221 is 25 μm, and the width d1 of the wire groove 221 is 100 μm. The number of wire grooves 221 on the negative electrode coating paste 220 is multiple, and the multiple wire grooves 221 are arranged parallel to each other and at equal intervals. The distance d2 between two adjacent wire grooves 221 is 2 mm.

[0145] 3. Preparation of the separator 300

[0146] A layer of alumina with a thickness of 2 μm is coated on one side of a polyethylene separator 300 with a thickness of 5 μm, and a composite layer mixed with a polyvinylidene fluoride - hexafluoropropylene copolymer with a thickness of 1 μm is coated on both sides to obtain the separator 300.

[0147] 4. Assembly

[0148] The positive electrode sheet 100, the separator 300, and the negative electrode sheet 200 are stacked for lamination. The separator 300 is provided between every two adjacent positive electrode sheets 100 and negative electrode sheets 200. A hot pressing device is used to hot press the laminated positive electrode sheet 100, separator 300, and negative electrode sheet 200 to fix the positive electrode sheet 100 and the negative electrode sheet 200 to the separator 300 respectively. The thickness H of the assembled battery cell is 10 mm. The ratio of the distance between two adjacent wire grooves 221 on the negative electrode coating paste 220 to the thickness of the battery cell is 0.2.

[0149] The battery cell is encapsulated in an aluminum - plastic film bag, and processes such as injecting electrolyte, vacuum encapsulation, aging, formation, secondary sealing, and capacity sorting are carried out to obtain the corresponding battery. The composition of the electrolyte is: organic solvent, lithium salt, and additive. Among them, the organic solvent includes EC, PC, and EMC with a mass ratio of 1:1:1, the lithium salt is LiPF6 with a concentration of 1 mol / L, and the additives include FEC and PS with their respective mass percentages of 7% and 3% respectively.

[0150] Example 2

[0151] Example 2 is carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode coating paste 220 is 60°.

[0152] Example 3

[0153] Example 3 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220 is 75°.

[0154] Example 4

[0155] Example 4 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220 is 135°.

[0156] Example 5

[0157] Example 5 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the depth h of the wire groove 221 is 3 μm.

[0158] Example 6

[0159] Example 6 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the depth h of the wire groove 221 is 5 μm.

[0160] Example 7

[0161] Example 7 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the depth h of the wire groove 221 is 40 μm.

[0162] Example 8

[0163] Example 8 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the depth h of the wire groove 221 is 45 μm.

[0164] Example 9

[0165] Example 9 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the width d1 of the wire groove 221 is 30 μm.

[0166] Example 10

[0167] Example 10 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the width d1 of the wire groove 221 is 50 μm.

[0168] Example 11

[0169] Example 11 was carried out with reference to Example 1. The difference is that during the preparation of the negative electrode sheet 200, the width d1 of the wire groove 221 is 200 μm.

[0170] Example 12

[0171] Example 12 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the width d1 of the wire groove 221 was 230 μm.

[0172] Example 13

[0173] Example 13 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the thickness h3 of the copper foil current collector was 3 μm.

[0174] Example 14

[0175] Example 14 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the thickness h3 of the copper foil current collector was 10 μm.

[0176] Example 15

[0177] Example 15 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the thickness h3 of the copper foil current collector was 12 μm.

[0178] Example 16

[0179] Example 16 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the distance d2 between two adjacent wire grooves 221 was 0.4 mm.

[0180] The thickness H of the assembled battery cell was 2 mm, and the ratio of the distance d2 between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness H of the battery cell was 0.2.

[0181] Example 17

[0182] Example 17 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the distance d2 between two adjacent wire grooves 221 was 1 mm.

[0183] The thickness H of the assembled battery cell was 2 mm, and the ratio of the distance d2 between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness H of the battery cell was 0.5.

[0184] Example 18

[0185] Example 18 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the distance d2 between two adjacent wire grooves 221 was 2 mm.

[0186] The thickness H of the assembled battery cell was 2 mm, and the ratio of the distance d2 between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness H of the battery cell was 1.

[0187] Example 19

[0188] Example 19 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the distance d2 between two adjacent wire grooves 221 was 5 mm.

[0189] The thickness H of the assembled battery cell was 2 mm, and the ratio of the distance d2 between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness H of the battery cell was 2.5.

[0190] Example 20

[0191] Example 20 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the distance d2 between two adjacent wire grooves 221 was 6 mm.

[0192] The thickness H of the assembled battery cell was 2 mm, and the ratio of the distance d2 between two adjacent wire grooves 221 on the negative electrode paste 220 to the thickness H of the battery cell was 3.

[0193] Comparative Example 1

[0194] Comparative Example 1 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220 was 90°.

[0195] Comparative Example 2

[0196] Comparative Example 2 was carried out with reference to Example 1, except that during the preparation of the negative electrode sheet 200, the extending direction of the wire groove 221 was parallel to the edge of the negative electrode paste 220, that is, the included angle θ2 between the extending direction of the wire groove 221 and the edge of the negative electrode paste 220 was 0.

[0197] Table 1:

[0198]

[0199]

[0200] The relevant performances of the battery cells in the above examples and comparative examples were tested, and the test results were recorded in Table 2. The test methods were as follows:

[0201] 1. Powder dropping situation of the negative electrode sheet 200

[0202] The battery cells obtained in the above examples and comparative examples were disassembled in the environment of a drying room, and the powder dropping situation of the negative electrode sheet 200 was observed. The powder dropping degrees were no powder dropping, slight powder dropping, moderate powder dropping, and severe powder dropping respectively.

[0203] 2. Tensile strength of the negative electrode sheet 200

[0204] Using a vertical tensile testing machine, fix the negative electrode sheets 200 obtained from the above-mentioned examples and comparative examples on the clamping fixtures at both ends of the tensile testing machine. Align the two ends of the clamping fixtures, press the button of the tensile equipment, and the equipment moves at a speed of 10 mm / s until the negative electrode sheet 200 breaks, and then read the tensile data.

[0205] Test the relevant performances of the batteries made from the battery cells obtained from the above-mentioned examples and comparative examples. The test results are recorded in Table 2, and the test methods are as follows:

[0206] 3. Energy density

[0207] Using a battery charge and discharge tester, charge the batteries made from the battery cells obtained from the above-mentioned examples and comparative examples at a constant current of 0.5C to 4.45V at 25°C, and then charge at a constant voltage until the current drops to 0.02C. After standing for 5 minutes, discharge the battery at a constant current of 0.2C to 3.0V, record the first discharge energy of the battery, measure the thickness, width and length of the battery and calculate the product of the three to obtain the volume of the battery, and calculate the volume energy density of the battery = the first discharge energy of the battery * voltage platform / volume of the battery.

[0208] 4. Capacity and capacity retention rate

[0209] Charge the batteries made from the battery cells obtained from the above-mentioned examples and comparative examples at 25°C at a constant current of 1.2C to 4.3V, then charge at 0.7C to 4.45V, and then charge at a constant voltage to 0.05C. After standing for 10 minutes, discharge at 0.5C to 3V, stand for 10 minutes, discharge at 0.5C to 3V, stand for 10 minutes, and perform cyclic testing 800 times according to this charge and discharge procedure, and measure the initial capacity at the first cycle and the capacity after cycling at the 800th cycle.

[0210] Capacity retention rate = initial capacity / capacity after cycling * 100%.

[0211] Table 2:

[0212]

[0213]

[0214]

[0215] As can be seen from Table 2, for the battery cells provided in Examples 1 - 20, compared with the battery cells provided in Comparative Example 1 and Comparative Example 2, the powder dropping situation of the negative electrode sheet 200 has been effectively improved, and the performance and safety of the battery have been improved.

[0216] As can be seen from Table 2, as the depth h of the wire groove 221 increases, the initial capacity of the battery gradually decreases, and the capacity retention rate of the battery gradually increases. As can be seen from Table 2, as the width d1 of the wire groove 221 increases, the initial capacity of the battery gradually decreases, and the capacity retention rate of the battery gradually increases.

[0217] As can be seen from Table 2, as the thickness of the copper foil current collector increases, the tensile strength of the negative electrode sheet 200 gradually increases, and the energy density of the battery gradually decreases.

[0218] As can be seen from Table 2, as the distance d2 between two adjacent wire grooves 221 increases, the initial capacity of the battery gradually increases, and the capacity retention rate of the battery gradually decreases. When the battery cell is a thin battery cell, as d2 / H increases, the initial capacity of the battery gradually increases, and the capacity retention rate of the battery gradually decreases.

[0219] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A negative electrode sheet (200), characterized in that: include: Anode current collector; A negative electrode ear (210), wherein the negative electrode ear (210) is electrically connected to the negative electrode current collector, A negative electrode paste (220), the negative electrode paste (220) being arranged on at least one side of the negative electrode current collector, a wire groove (221) being arranged on a side of the negative electrode paste (220) away from the negative electrode current collector, and a first angle θ2 being formed between an extension direction of the wire groove (221) and an edge of the negative electrode paste (220); Among them, the size of θ2 satisfies: 0<θ2<90°, or, 90°<θ2<180°.

2. The negative electrode sheet (200) according to claim 1, characterized in that: The negative electrode paste (220) is respectively arranged on two opposite sides of the negative electrode current collector in the thickness direction, and the line groove (221) is arranged on the negative electrode paste (220) on both sides of the negative electrode current collector, and there is a second angle between the extension direction of the line groove (221) on the negative electrode paste (220) on one side of the negative electrode current collector and the extension direction of the line groove (221) on the negative electrode paste (220) on the other side of the negative electrode current collector.

3. The negative electrode sheet (200) according to claim 1, characterized in that: The tensile strength of the negative electrode current collector is ≥400 MPa, and the thickness of the negative electrode current collector is 4 μm-10 μm.

4. The negative electrode sheet (200) according to claim 1, characterized in that: In the width direction of the negative electrode sheet (200), the edge of the negative electrode paste (220) and the middle area of ​​the negative electrode paste (220) have the same thickness.

5. The negative electrode sheet (200) according to claim 1, characterized in that: The negative electrode sheet (200) further comprises a ceramic layer (230) located on a side of the negative electrode paste (220) away from the negative electrode current collector.

6. The negative electrode sheet (200) according to claim 1, characterized in that: The depth of the wire groove (221) is 5 μm-40 μm; and / or, The width of the wire groove (221) is 50 μm-200 μm; and / or, The thickness of the negative electrode paste (220) is 30 μm-80 μm.

7. The negative electrode sheet (200) according to claim 1, characterized in that: Each of the wire grooves (221) includes at least one wire segment groove.

8. The negative electrode sheet (200) according to claim 1, characterized in that: The negative electrode paste (220) has a first covering portion (222) extending onto the negative electrode ear (210); The end of the projection of the wire groove (221) in the thickness direction of the negative electrode sheet (200) extends to the edge of the negative electrode current collector facing the negative electrode ear (210); Alternatively, there is a gap between the end of the projection of the line groove (221) in the thickness direction of the negative electrode sheet (200) and the edge of the negative electrode current collector facing the negative electrode ear (210); Alternatively, at least part of the end of the wire groove (221) extends onto the first covering portion (222).

9. A battery cell, characterized in that: The invention comprises a stacked positive electrode sheet (100), a separator (300) and a negative electrode sheet (200) according to any one of claims 1 to 8, wherein the separator (300) is arranged between adjacent positive electrode sheets (100) and negative electrode sheets (200).

10. The battery cell according to claim 9, characterized in that: The separator (300) has a dent on a side facing the negative electrode sheet (200); And / or, the separator (300) contains a dent at a position corresponding to the concave portion of the negative electrode sheet (200).

11. The battery cell according to claim 9, characterized in that: The peeling force between the positive electrode sheet (100) and the separator (300) is 0.7 N / m-9 N / m; And / or, the negative electrode paste (220) has a first peeling force between an area outside the wire groove (221) and the diaphragm (300), and the negative electrode paste (220) has a second peeling force between an area inside the wire groove (221) and the diaphragm (300), the first peeling force is 0.8 N / m-6 N / m, and the ratio of the second peeling force to the first peeling force is 0.9-0.

99.

12. The battery cell according to claim 9, characterized in that: The outermost layer of the battery cell is a positive electrode sheet (100), the outermost positive electrode sheet (100) is a single-sided paste-coated positive electrode sheet, and the positive electrode paste of the outermost positive electrode sheet (100) is located on the side of the positive electrode collector facing the adjacent negative electrode sheet (200), and the thickness of the positive electrode collector of the outermost positive electrode sheet (100) is 8 μm-20 μm; or, The outermost layer of the battery cell is a negative electrode sheet (200), and the outermost negative electrode sheet (200) is a single-sided pasted negative electrode sheet or a double-sided pasted negative electrode sheet; or, The outermost layer of the battery cell is a separator (300), the outermost separator (300) is adjacent to the negative electrode sheet (200), and the negative electrode sheet (200) adjacent to the outermost separator (300) is a double-sided pasted negative electrode sheet.

13. The battery cell according to claim 9, characterized in that: The outermost layer of the battery cell is a negative electrode sheet (200), the outermost negative electrode sheet (200) is a single-sided pasted negative electrode sheet, the negative electrode paste (220) of the outermost negative electrode sheet (200) is located on the side of the negative electrode collector facing the adjacent positive electrode sheet (100), and the thickness of the negative electrode collector of the outermost negative electrode sheet (200) is 8 μm-20 μm.

14. The battery cell according to claim 9, characterized in that: The thickness of the battery cell is 2 mm-3 mm, the number of the wire grooves (221) on the negative electrode paste (220) is at least 2, the distance between two adjacent wire grooves (221) is 0.5 mm-5 mm, and the ratio between the distance between two adjacent wire grooves (221) on the negative electrode paste (220) and the thickness of the battery cell is 0.4-2.

5.

15. The battery cell according to claim 9, characterized in that: The positive electrode sheet (100) further comprises an insulating coating disposed on the positive electrode current collector, the insulating coating being located at the edge of the positive electrode sheet (100), and the insulating coating being in contact with the positive electrode paste, and at least a portion of the projection of the wire groove (221) in the thickness direction of the battery cell and the projection of the insulating coating in the thickness direction of the battery cell having an overlapping area; Alternatively, the positive electrode sheet (100) further comprises an insulating coating disposed on the positive electrode ear, the insulating coating being in contact with the positive electrode paste, and at least a portion of the projection of the wire groove (221) in the direction of the thickness of the battery cell and the projection of the insulating coating in the direction of the thickness of the battery cell having an overlapping area.

16. A battery, characterized in that: A battery cell comprising any one of claims 9 to 15.

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