Pole piece, laminated cell and battery

Abstract

The utility model relates to the field of batteries, in particular to a pole piece, a laminated battery cell and a battery. The pole piece comprises a current collector and an active substance layer located on at least one side of the surface of the current collector, a tab extending out of the current collector is arranged on the edge of one side of the current collector, a plurality of first concave parts are arranged on the active substance layer, a plurality of second concave parts are arranged on the tab, and the depth of the first concave parts is larger than that of the second concave parts. By arranging the first concave part on the active substance layer on the surface of the current collector, the infiltration speed of the electrolyte on the active substance on the pole piece can be improved, the wettability of the electrolyte on the active substance is improved, the transmission path of lithium ions is expanded, the liquid retention amount on the pole piece is increased, and the rate capability of the battery cell is improved. Moreover, the second concave parts are arranged on the tabs, and the surface roughness of the tabs is improved due to the existence of the second concave parts at the tabs, so that the friction force between the tabs in the pre-welding process is improved, the welding effect is improved, and the welding yield is improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and particularly to an electrode sheet, a laminated battery cell and a battery. Background Art

[0002] Lithium-ion batteries are widely used in fields such as mobile phones, laptop computers, and electric vehicles. With the gradual expansion of the application market demand, new requirements are also put forward for the energy density of lithium-ion batteries. Compared with traditional wound batteries, laminated batteries have lower internal resistance, better energy density, and more flexible size manufacturing. Therefore, combining thick electrode sheets with laminated battery technology is an important development direction for future high-energy density batteries.

[0003] However, a dense film is formed on the surface of the electrode sheet after rolling, and it is difficult for the electrolyte to penetrate into the active material near the current collector, resulting in an inability to carry out sufficient electrochemical reactions. Moreover, during the manufacturing process of the laminated battery, welding treatment needs to be performed at the tab of the electrode sheet. Since there are many tab positions on the laminated battery and the interaction force between them is weak, poor welding is likely to occur, affecting the performance of the obtained battery. Summary of the Utility Model

[0004] Based on this, the present application provides an electrode sheet, a laminated battery cell and a battery to solve the problems in the related art that the wetting performance of the electrolyte is poor and the welding yield is low, affecting the battery performance.

[0005] The present application provides an electrode sheet, including a current collector and an active material layer located on at least one side of the surface of the current collector. An electrode tab extending out of the current collector is provided at one side edge of the current collector. The active material layer is provided with a plurality of first recesses, and the electrode tab is provided with a plurality of second recesses. The depth of the first recesses is greater than the depth of the second recesses.

[0006] In a possible implementation manner, the first recesses include first grooves, and the included angle θ1 between the long axis direction of the first grooves and the extending direction of the electrode tab ranges from 30° to 60°; and / or,

[0007] The second recesses include second grooves, and the included angle θ2 between the long axis direction of the second grooves and the extending direction of the electrode tab ranges from 30° to 60°.

[0008] In a possible implementation manner, welding points are provided on the surface of the electrode tab, and some of the welding points are located in the second recesses.

[0009] In a possible implementation manner, the width of the welding points is a1, and the range of a1 is 0.2 mm - 1 mm; and / or,

[0010] The spacing between the welding points is L, and the range of L is 0.3 mm - 1.5 mm; and / or,

[0011] The coincidence rate of the solder joint and the second recess is 50%-100%.

[0012] In a possible implementation, the active material layer includes a first active material layer and a second active material layer, and the first active material layer and the second active material layer are respectively located on opposite sides in the thickness direction of the current collector;

[0013] On the surface of the current collector, the orthographic projection of the first recess on the first active material layer coincides with or is parallel to the orthographic projection of the first recess on the second active material layer; or

[0014] On the surface of the current collector, the orthographic projection of the first recess on the first active material layer intersects with the orthographic projection of the first recess on the second active material layer.

[0015] In a possible implementation, the depth of the first recess is h1, and the range of h1 is 5μm-40μm; and / or,

[0016] The width of the first recess is W1, and the range of W1 is 50μm-200μm; and / or,

[0017] The spacing between the first recesses is b1, and the range of b1 is 0.5mm-5mm.

[0018] In a possible implementation, the depth of the second recess is h2, and h2≤4μm; and / or,

[0019] The width of the second recess is W2, and the range of W2 is 50μm-200μm.

[0020] In a possible implementation, the depth h2 of the second recess ≤1μm.

[0021] In a possible implementation, the depth of the first recess is h1, and the depth of the second recess is h2, and h1 and h2 satisfy: h1 = k×h2 + b, where the value range of k is 20-50, and the value range of b is 5-10.

[0022] In a possible implementation, the active material layer extends to the surface of the tab.

[0023] In a possible implementation, along the extension direction of the tab, the width of the active material layer exceeding the edge of the current collector is b2, and the range of b2 is 0.1mm-1.5mm; and / or,

[0024] The thickness of the active material layer on the surface of the current collector is t1, and the range of t1 is 30μm-70μm; and / or,

[0025] The thickness of the active material layer on the surface of the tab is t2, and the range of t2 is 30μm-70μm.

[0026] In a possible implementation, the first recess extends to the tab, and the depth of the first recess extending to the tab is h3, where the range of h3 is 5 μm - 40 μm; and / or,

[0027] The ratio of the depth of the first recess extending to the tab to the thickness of the active material layer on the tab surface ranges from 0.1 to 0.8.

[0028] In a possible implementation, the active material layer has a normal region and a thinning region, the thickness of the thinning region is smaller than that of the normal region, and the thinning region is located at the edge of the current collector where the tab is provided and / or on the tab.

[0029] In a possible implementation, along the extending direction of the tab, the width of the thinning region is H1, and the range of H1 is 1 mm - 5 mm; and / or,

[0030] The range of the difference between the thickness of the normal region and the thickness of the thinning region is 2 μm - 8 μm; and / or,

[0031] Along the extending direction of the tab, the width of the thinning region on the tab surface is H2, and the range of H2 is 0.1 mm - 1.5 mm.

[0032] In a possible implementation, along the extending direction of the tab, the distance between the edge of the active material layer on the tab away from the current collector and the first recess on the adjacent side of this edge is H3, and H3 satisfies: 0.1 mm ≤ H3 ≤ 1.5 mm.

[0033] In a possible implementation, under the same area, the weight of the active material layer in the thinning region is G1, and the weight of the active material layer in the normal region is G2, and G1 and G2 satisfy: 0.5 ≤ G1 / G2 ≤ 1.

[0034] In a possible implementation, in the thinning region, the ratio of the depth of the first recess to the thickness of the active material layer ranges from 0.2 to 0.8; and / or,

[0035] In the normal region, the ratio of the depth of the first recess to the thickness of the active material layer ranges from 0.1 to 0.5.

[0036] In a possible implementation, the electrode sheet is a positive electrode sheet, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the surface of the positive electrode current collector, and in the thickness direction of the positive electrode active material layer, the sizes of the positive electrode active material layers on the same side of the positive electrode current collector are the same.

[0037] On the other hand, the present application provides a laminated battery cell, including a plurality of stacked positive electrode sheets, separator membranes, and negative electrode sheets, and the negative electrode sheet is the above-mentioned electrode sheet.

[0038] In a possible implementation, along the stacking direction, the width by which the projection of the edge of the active material layer on the negative electrode tab exceeds the projection of the edge of the positive electrode tab is OH, and the range of OH is 0.1 mm - 2 mm.

[0039] In a possible implementation, the thickness of the stacked cell is k, and the spacing between the first recesses is b1, and b1 and k satisfy: 0.4 ≤ b1 / k ≤ 2.5.

[0040] On the other hand, the present application provides a battery, including a battery housing and the above-mentioned stacked cell, and the stacked cell is located in the battery housing.

[0041] For the electrode tab, stacked cell and battery provided by the present application, by providing the first recesses on the active material layer on the surface of the current collector, the presence of the first recesses can improve the wetting speed of the electrolyte on the active material on the electrode tab, improve the wettability of the electrolyte on the active material, expand the transmission path of lithium ions, and at the same time increase the liquid retention amount on the electrode tab, thereby improving the rate performance of the cell. And, by providing the second recesses on the tab, the presence of the second recesses at the tab increases the surface roughness of the tab, thereby increasing the friction force between the tabs during the pre-welding process, improving the welding effect, and increasing the welding yield. Description of the Drawings

[0042] 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, other drawings can be obtained based on these drawings without creative efforts.

[0043] Figure 1 It is one of the schematic structural diagrams of the electrode tab provided in the embodiment of the present application;

[0044] Figure 2 It is Figure 1 the cross-sectional view of part A in

[0045] Figure 3 It is Figure 1 the cross-sectional view of part B in

[0046] Figure 4 It is another schematic structural diagram of the electrode tab provided in the embodiment of the present application;

[0047] Figure 5 It is the third schematic structural diagram of the electrode tab provided in the embodiment of the present application;

[0048] Figure 6 It is Figure 1 the side view of the shown electrode tab;

[0049] Figure 7 For Figure 1 A cross-sectional view of part C in it;

[0050] Figure 8 Figure 4 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application;

[0051] Figure 9 Figure 5 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application;

[0052] Figure 10 Figure of the schematic structural diagram of the stacked battery cell provided in the embodiment of the present application;

[0053] Figure 11 Figure 6 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application;

[0054] Figure 12 For Figure 11 The side view of the electrode sheet shown;

[0055] Figure 13 Figure 7 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application;

[0056] Figure 14 Figure 8 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application;

[0057] Figure 15 Figure 9 of the schematic structural diagram of the electrode sheet provided in the embodiment of the present application.

[0058] Explanation of reference numerals:

[0059] 100 - electrode sheet; 101 - positive electrode sheet; 102 - negative electrode sheet; 10 - current collector; 20 - active material layer; 21 - first groove; 22 - first active material layer; 23 - second active material layer; 24 - normal area; 25 - thinning area; 30 - tab; 31 - second groove; 32 - solder joint. Detailed implementation manners

[0060] To make the purpose, 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 from beginning to end. 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 a limitation to the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0061] In the description of the present application, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "linked" should be understood in a broad sense. For example, it can be a fixed connection, or an indirect connection through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0062] 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 the orientation or positional relationship based on 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 cannot be understood as a limitation to the present application.

[0063] The terms "first", "second", "third" (if any) in the specification, claims and the above drawings of the present application are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence.

[0064] 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 that includes a series of steps or units does not necessarily have to 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.

[0065] Lithium-ion batteries are widely used in fields such as mobile phones, laptops, and electric vehicles. With the gradual expansion of the application market demand, new requirements are also put forward for the energy density of lithium-ion batteries. Compared with traditional wound batteries, laminated batteries have lower internal resistance, better energy density, and more flexible size manufacturing. Therefore, the combination of thick electrode sheets and laminated battery technology is an important development direction for future high-energy density batteries.

[0066] However, a dense film is formed on the surface after the electrode sheet is roll-pressed, and it is difficult for the electrolyte to penetrate into the active material near the current collector, resulting in an inability to carry out sufficient electrochemical reactions. Moreover, during the manufacturing process of laminated batteries, welding treatment needs to be performed at the tabs on the electrode sheets. Since there are many tab positions on the laminated battery and the interaction force between them is weak, poor welding is likely to occur, affecting the performance of the manufactured battery.

[0067] After repeated thinking and verification, the inventor found that if grooves or holes are etched on the electrode sheet through laser or the like, the electrolyte can infiltrate the active material through the grooves, and the transmission path of lithium ions is also broadened, improving the rate performance of the battery cell. At the same time, grooves can also be etched on the tab of the electrode sheet through laser. The grooves at the tab can increase the surface roughness of the tab, thereby increasing the friction force between the tabs during the pre-welding process, improving the welding effect, and increasing the welding yield.

[0068] In view of this, the present application provides an electrode sheet, including a current collector and an active material layer located on at least one side of the surface of the current collector. A tab extending out of the current collector is provided at one side edge of the current collector. The active material layer contains a plurality of first recesses, and the tab contains a plurality of second recesses. The depth of the first recesses is greater than the depth of the second recesses.

[0069] By providing the first recesses on the active material layer on the surface of the current collector, the presence of the first recesses can increase the infiltration rate of the electrolyte into the active material on the electrode sheet, improve the wettability of the electrolyte to the active material, expand the transmission path of lithium ions, and at the same time increase the liquid retention amount on the electrode sheet, improving the rate performance of the battery cell. And, by providing the second recesses on the tab, the presence of the second recesses at the tab increases the surface roughness of the tab, thereby increasing the friction force between the tabs during the pre-welding process, improving the welding effect, and increasing the welding yield.

[0070] The content of the present application will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can understand the content of the present application more clearly and in detail.

[0071] Figure 1 It is one of the structural schematic diagrams of the electrode sheet provided in the embodiment of the present application. Figure 2 For Figure 1 The cross-sectional view of part A in Figure 3 For Figure 1 The cross-sectional view of part B in Figure 4 It is the second structural schematic diagram of the electrode sheet provided in the embodiment of the present application. Figure 5 It is the third structural schematic diagram of the electrode sheet provided in the embodiment of the present application. Figure 6 For Figure 1 The side view of the shown electrode sheet. Figure 7 For Figure 1 The cross-sectional view of part C in Figure 8 It is the fourth structural schematic diagram of the electrode sheet provided in the embodiment of the present application. Figure 9 It is the fifth structural schematic diagram of the electrode sheet provided in the embodiment of the present application. Figure 10 It is the structural schematic diagram of the stacked battery cell provided in the embodiment of the present application. Figure 11 It is the sixth structural schematic diagram of the electrode sheet provided in the embodiment of the present application. Figure 12 ForFigure 11 Side view of the electrode sheet shown Figure 13 It is the seventh structural schematic diagram of the electrode sheet provided in the embodiment of the present application Figure 14 It is the eighth structural schematic diagram of the electrode sheet provided in the embodiment of the present application Figure 15 It is the ninth structural schematic diagram of the electrode sheet provided in the embodiment of the present application

[0072] Refer to Figure 1 and Figure 2 In the embodiment of the present application, the provided electrode sheet 100 includes a current collector 10, an active material layer 20, and an electrode tab 30. The active material layer 20 is located on at least one side of the surface of the current collector 10. The electrode tab 30 is electrically connected to the current collector 10 and extends out of the current collector 10 from the edge on one side of the current collector 10

[0073] In the embodiment of the present application, the electrode sheet 100 can be a positive electrode sheet 101. Among them, the current collector 10 is a positive electrode current collector, the active material layer 20 is a positive electrode active material layer, and the electrode tab 30 is a positive electrode tab

[0074] The electrode sheet 100 can also be a negative electrode sheet 102. Among them, the current collector 10 is a negative electrode current collector, the active material layer 20 is a negative electrode active material layer, and the electrode tab 30 is a negative electrode tab

[0075] The polarities of the positive electrode sheet 101 and the negative electrode sheet 102 are opposite

[0076] In a possible implementation manner, the positive electrode sheet 101 uses aluminum foil as the positive electrode current collector, and the negative electrode sheet 102 uses copper foil as the negative electrode current collector

[0077] Among them, the provided battery cell of the present application is a stacked battery cell. After cutting the positive electrode sheet 101, the separator, and the negative electrode sheet 102 to a certain width, they are stacked in sequence

[0078] The separator is used to prevent contact short circuit between the positive electrode sheet 101 and the negative electrode sheet 102

[0079] As Figure 1 shown, the active material layer 20 is provided with a plurality of first recesses, and the electrode tab 30 is provided with a plurality of second recesses

[0080] The first recess can be a linear groove or a hole. In some embodiments, the first recess is a first groove 21

[0081] The second recess can be a linear groove or a hole. In some embodiments, the second recess is a second groove 31

[0082] A plurality of first grooves 21 are arranged at intervals. A plurality of second grooves 31 are arranged at intervals

[0083] The number of representations can be one, two, three or more than three. Therefore, the number of first grooves 21 means that there can be one, two, three or more than three first grooves 21. The number of second grooves 31 means that there can be one, two, three or more than three second grooves 31.

[0084] Preferably, the electrode sheet 100 is the negative electrode sheet 102. By providing the first grooves 21 on the negative electrode sheet 102, the flow of the electrolyte can be improved, the wetting ability of the electrolyte to the electrode sheet can be enhanced, the negative electrode surface density and negative electrode kinetics can be improved, and at the same time, the liquid storage capacity can be increased, and the lithium deposition on the negative electrode can be alleviated.

[0085] The first grooves 21 can be provided on the active material layer 20 on one side surface of the current collector 10, or can be provided on the active material layers 20 on both side surfaces of the current collector 10.

[0086] The first grooves 21 extend in a direction perpendicular to the thickness direction of the electrode sheet 100, that is, the first grooves 21 extend in the plane where the active material layer 20 is located.

[0087] Preferably, the first grooves 21 can be formed by laser, and the first grooves 21 can be continuously formed, so as to improve the flow of the electrolyte and enhance the wetting ability of the electrolyte to the electrode sheet 100.

[0088] Preferably, the electrode sheet 100 is the negative electrode sheet 102. The formation of the first grooves 21 can increase the liquid storage capacity and at the same time alleviate the lithium deposition on the negative electrode.

[0089] In a possible implementation manner, the distance between the first grooves 21 is b1, and the range of b1 is 0.5 mm - 5 mm.

[0090] It should be noted that the distance b1 can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, etc., and there is no specific limit.

[0091] The distance b1 between the first grooves 21 is greater than or equal to 0.5 mm and less than or equal to 5 mm. Such a setting mainly considers the performance of the battery. If the distance b1 between the first grooves 21 is less than 0.5 mm, the first grooves 21 are too dense, which is likely to cause powder falling, and more active material removed by forming the first grooves 21 will easily reduce the energy density of the battery and affect the charge and discharge performance of the battery. If the distance b1 between the first grooves 21 is greater than 5 mm, the first grooves 21 are too sparse, and there are fewer first grooves 21 in the battery, which has a weak improvement on the wetting of the electrolyte to the active material, cannot improve the wettability of the electrolyte to the active material, and is likely to cause problems such as lithium deposition. Therefore, the distance b1 between the first grooves 21 is in the range of 0.5 mm - 5 mm, so as to improve the charge and discharge performance of the battery.

[0092] In a possible implementation, a plurality of first grooves 21 are equally spaced.

[0093] In another possible implementation, a plurality of first grooves 21 are not equally spaced.

[0094] As Figure 2 shown, in a possible implementation, the depth of the first groove 21 is h1, and the range of h1 is 5 μm - 40 μm.

[0095] It should be noted that the depth h1 can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc.

[0096] The depth h1 of the first groove 21 is greater than or equal to 5 μm and less than or equal to 40 μm. Such a setting mainly considers the performance of the battery. If the depth h1 of the first groove 21 is less than 5 μm, the first groove 21 is relatively shallow, and in the battery, the improvement of the electrolyte wetting the active material is weak, and the wettability of the electrolyte to the active material cannot be improved, and problems such as lithium plating are likely to occur. If the depth h1 of the first groove 21 is greater than 40 μm, due to the excessive depth of the first groove 21, more active material is removed, which is likely to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the depth h1 of the first groove 21 is in the range of 5 μm - 40 μm, thereby improving the charge and discharge performance of the battery.

[0097] In a possible implementation, the width of the first groove 21 is W1, and the range of W1 is 50 μm - 200 μm.

[0098] It should be noted that the width W1 can be 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, etc., and there is no excessive limitation on the specific value.

[0099] The width W1 of the first groove 21 is greater than or equal to 50 μm and less than or equal to 200 μm. Such a setting mainly considers the performance of the battery. If the width W1 of the first groove 21 is less than 50 μm, the first groove 21 is relatively narrow, and in the battery, the improvement of the electrolyte wetting the active material is weak, and the wettability of the electrolyte to the active material cannot be improved, and problems such as lithium plating are likely to occur. If the width W1 of the first groove 21 is greater than 200 μm, due to the excessive width of the first groove 21, more active material is removed when the first groove 21 is opened, which is likely to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the width W1 of the first groove 21 is in the range of 50 μm - 200 μm, thereby improving the charge and discharge performance of the battery.

[0100] In a possible implementation, the direction in which the first groove 21 extends on the surface of the active material layer 20 is the major axis direction of the first groove 21. There is an included angle between the major axis direction of the first groove 21 and the extending direction of the tab 30, and the included angle is θ1. The range of θ1 is 30° - 60°.

[0101] It should be noted that the included angle θ1 can be 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc., and there are no specific limitations.

[0102] The pole piece of the stacked cell is etched with the first groove 21 on the pole piece tape by a laser, and then cut into small pieces by a hardware cutter or a laser. If the major axis direction of the first groove 21 is parallel to the extending direction of the tab 30, there will be a problem of powder falling during cutting due to stress, and even a phenomenon of local shedding of the active material layer 20 may occur.

[0103] When there is an included angle θ1, within the range of 30° - 60°, between the major axis direction of the first groove 21 and the extending direction of the tab 30, it can solve the problems of powder falling and even local paste shedding under the action of stress during the cutting or laser die-cutting process of the stack, improve the peeling force of the active material, and the peeling force can be increased by 5% - 10%. Thus, it ensures that the energy density of the battery is not lost and improves the cycle performance of the battery.

[0104] The presence of the second groove 31 at the tab 30 improves the surface roughness of the tab 30, thereby improving the friction force between the tabs 30 during the pre-welding process, improving the welding effect, ensuring no welding detachment, ensuring the stability of the connection during the use of the battery, and improving the safety performance of the battery.

[0105] The second groove 31 can be provided on one side surface of the tab 30, or can be provided on both side surfaces of the tab 30.

[0106] The second groove 31 extends in a direction perpendicular to the thickness direction of the pole piece 100, that is, the second groove 31 extends in the plane where the tab 30 is located.

[0107] Preferably, the second groove 31 can be opened by a laser, and the second groove 31 can be continuously opened.

[0108] The depth of the first groove 21 is greater than the depth of the second groove 31.

[0109] As Figure 3 shown, in a possible implementation, the depth of the second groove 31 is h2, and h2 satisfies: h2 ≤ 4μm.

[0110] It should be noted that the depth h2 can be 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, etc., and there are no specific limitations.

[0111] Preferably, h2 satisfies: h2 ≤ 1 μm.

[0112] The depth h2 of the second groove 31 is less than or equal to 4 μm. Such a setting mainly considers the safety performance of the battery. If the depth h2 of the second groove 31 is greater than 4 μm, since the second groove 31 is opened too deep, too many tab ears 30 are removed, which easily causes problems such as the tab ears 30 being torn or even ripped during the grooving process, affecting the yield of the electrode sheet 100. Therefore, the depth h2 of the second groove 31 ≤ 4 μm, thus ensuring the yield of the battery and improving the safety performance of the battery.

[0113] In a possible implementation, the depth of the first groove 21 is h1, and the depth of the second groove 31 is h2. h1 and h2 satisfy: h1 = k × h2 + b, where the value range of k is 20 - 50, and the value range of b is 5 - 10.

[0114] The depth of the second groove 31 at the tab ear position is much smaller than the depth of the first groove 21 on the active material layer 20.

[0115] In a possible implementation, the width of the second groove 31 is W2, and the range of W2 is 50 μm - 200 μm.

[0116] It should be noted that the width W2 can be 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, etc., without specific excessive restrictions.

[0117] The width W2 of the second groove 31 is greater than or equal to 50 μm and less than or equal to 200 μm. Such a setting mainly considers the safety performance of the battery. If the width W2 of the second groove 31 is less than 50 μm, the second groove 31 is relatively narrow, and in the battery, the improvement of the surface roughness of the tab ear is weak, and the friction between the tab ears during the pre-welding process cannot be improved, resulting in a low welding effect and welding yield. If the width W2 of the second groove 31 is greater than 200 μm, since the second groove 31 is too wide, too many tab ears 30 are removed, which easily causes the tab ears 30 to be thinner, and during welding, the tab ears 30 are easily welded through, affecting the yield of the electrode sheet 100. Therefore, the range of the width W2 of the second groove 31 is 50 μm - 200 μm, thus ensuring the yield of the battery and improving the safety performance of the battery.

[0118] In a possible implementation, the direction in which the second groove 31 extends on the tab ear 30 surface is the long axis direction of the second groove 31. There is an included angle between the long axis direction of the second groove 31 and the tab ear 30 extension direction, and the included angle is θ2, and the range of θ2 is 30° - 60°.

[0119] It should be noted that the included angle θ2 can be 30°, 35°, 40°, 45°, 50°, 55°, 60°, etc., and there is no excessive limitation on the specific value.

[0120] The pole piece of the laminated battery cell is etched with a second groove 31 on the tab 30 by a laser, and then cut into small pieces by a hardware cutter or a laser. If the long axis direction of the second groove 31 is parallel to the extension direction of the tab 30, there will be a problem that the tab 30 is torn due to stress during cutting, and even a phenomenon that the tab 30 is torn and the current collector 10 is torn and scrapped will occur.

[0121] When there is an included angle θ2, an angle of 30° - 60°, between the long axis direction of the second groove 31 and the extension direction of the tab 30, it can solve the problem that the tab 30 is torn under the action of stress during the cutting of the laminated battery cell by a hardware tool or laser die-cutting, and even the current collector 10 is torn and scrapped, improving the yield of the pole piece 100, thus ensuring the yield of the battery and improving the safety performance of the battery.

[0122] As Figure 4 and Figure 5 shown, in a possible implementation, the surface of the tab 30 is provided with welding points 32, and some of the welding points 32 are located in the second groove 31.

[0123] The welding head after welding the welding points 32 can be Figure 4 the straight-line welding head shown, or it can also be Figure 5 the diagonal-line welding head shown.

[0124] In a possible implementation, the width of the welding point 32 is a1, and the range of a1 is 0.2 mm - 1 mm.

[0125] It should be noted that the width a1 can be 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, etc., and there is no excessive limitation on the specific value.

[0126] The width a1 of the welding point 32 is greater than or equal to 0.2 mm and less than or equal to 1 mm. Such a setting mainly considers the welding quality. If the width a1 of the welding point 32 is less than 0.2 mm, the connection strength of the welding point 32 is insufficient, and the problem of insecure welding is likely to occur. If the width a1 of the welding point 32 is greater than 1 mm, due to the too large welding head, the problem of welding deviation is likely to occur, both of which will affect the welding yield and cause quality problems of the battery. Therefore, the width a1 of the welding point 32 is within the range of 0.2 mm - 1 mm, thereby improving the welding strength and yield and improving the quality of the battery.

[0127] In a possible implementation, the distance between the welding points 32 is L, and the range of L is 0.3 mm - 1.5 mm.

[0128] It should be noted that the spacing L can be 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, etc., and there is no excessive limitation on the specific value.

[0129] The spacing L of the solder joints 32 is greater than or equal to 0.3mm and less than or equal to 1.5mm. Such a setting mainly considers the welding quality. If the spacing L of the solder joints 32 is less than 0.3mm, it is easy to have heat concentration during welding due to the too small spacing, resulting in the problem of welding through. If the width a1 of the solder joints 32 is greater than 1.5mm, the number of solder joints 32 will decrease due to the reduced welding density, resulting in insufficient connection strength and easy occurrence of insecure welding problems, both of which will affect the welding yield and cause quality problems of the battery. Therefore, the spacing L of the solder joints 32 is within the range of 0.3mm - 1.5mm, so as to improve the welding strength and yield and improve the quality of the battery.

[0130] In a possible implementation, the coincidence rate of the solder joints 32 and the second groove 31, that is, the percentage of the number of solder joints 32 welded on the second groove 31 in the total number of solder joints 32, is 50% - 100%.

[0131] It should be noted that the coincidence rate can be 50%, 60%, 70%, 80%, 90%, 100%, etc., and there is no excessive limitation on the specific value.

[0132] The coincidence rate of the solder joints 32 is greater than or equal to 50%. Such a setting mainly considers the quality during welding. If the coincidence rate of the solder joints 32 is less than 50%, the second groove 31 cannot be fully utilized to improve the adhesion of the solder joints, and it is easy to have the problem of insecure welding, which will affect the welding yield and cause quality problems of the battery. Therefore, the coincidence rate of the solder joints 32 is within the range of 50% - 100%, so as to improve the welding strength and yield and improve the quality of the battery.

[0133] The existence of the second groove 31 at the tab 30 makes the surface of the second groove 31 area on the tab 30 rougher than the area without the second groove 31. During welding, the second groove 31 areas between adjacent tabs 30 come into contact first, and the solder joints 32 act on the second groove 31, which can improve the adhesion between adjacent tabs 30 after welding and at the same time improve the welding tensile force of the tab 30.

[0134] As Figure 6 and Figure 7 shown, in a possible implementation, the active material layer 20 extends to the surface of the tab 30.

[0135] In a possible implementation, along the extension direction of the tab 30, the width b2 of the active material layer 20 exceeding the edge of the current collector 10 ranges from 0.1mm to 1.5mm.

[0136] It should be noted that the width b2 can be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1.1 mm, 1.3 mm, 1.5 mm, etc., and there is no excessive limitation on the specific value.

[0137] The width b2 is greater than or equal to 0.1 mm and less than or equal to 1.5 mm. Such a setting mainly considers the quality of the battery. If the width b2 is less than 0.1 mm, it has no effect on improving the energy density and is prone to waste of raw materials. If the width b2 is greater than 1.5 mm, due to excessive coating of the active material layer 20, there is an easy problem of open circuit during use, causing safety problems of the battery. Therefore, the width b2 is in the range of 0.1 mm - 1.5 mm, thereby improving the safety performance of the battery.

[0138] In a possible implementation manner, the thickness of the active material layer 20 on one side of the surface of the current collector 10 is t1, and the range of t1 is 30 μm - 70 μm.

[0139] It should be noted that the thickness t1 can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, etc., and there is no excessive limitation on the specific value.

[0140] The thickness t1 is greater than or equal to 30 μm and less than or equal to 70 μm. Such a setting mainly considers the charge and discharge performance of the battery. If the thickness t1 is less than 30 μm, there is less active material and the energy density of the battery is low. If the thickness t1 is greater than 70 μm, due to excessive coating of the active material, there is an easy problem that the electrolyte cannot fully infiltrate the active material during use, affecting the charge and discharge of the battery. Therefore, the thickness t1 is in the range of 30 μm - 70 μm, thereby improving the charge and discharge performance of the battery.

[0141] In a possible implementation manner, the thickness of the active material layer 20 on the surface of the tab 30 is t2, and the range of t2 is 30 μm - 70 μm.

[0142] It should be noted that the thickness t2 can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, etc., and there is no excessive limitation on the specific value.

[0143] The thickness t2 is greater than or equal to 30 μm and less than or equal to 70 μm. Such a setting mainly considers the charge and discharge performance of the battery. If the thickness t2 is less than 30 μm, there will be less active material and the energy density of the battery will be lower. If the thickness t2 is greater than 70 μm, due to too much coated active material, it is easy to have the problem that the electrolyte cannot fully infiltrate the active material during use, affecting the charge and discharge performance of the battery. Therefore, the thickness t2 is in the range of 30 μm - 70 μm, thereby improving the charge and discharge performance of the battery.

[0144] The thickness of the active material layer 20 on the surface of the current collector 10 is the same as the thickness of the active material layer 20 on the surface of the tab 30, which is convenient for paste coating treatment.

[0145] In a possible implementation, the first groove 21 extends onto the tab 30, and the depth of the first groove 21 extending onto the tab 30 is h3, and the range of h3 is 5 μm - 40 μm.

[0146] It should be noted that the depth h3 can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc., and there is no excessive limitation on the specific value.

[0147] The depth h3 of the first groove 21 is greater than or equal to 5 μm and less than or equal to 40 μm. Such a setting mainly considers the performance of the battery. If the depth h3 of the first groove 21 is less than 5 μm, the first groove 21 is relatively shallow, and in the battery, the improvement of the electrolyte infiltrating the active material is weak, and the wettability of the electrolyte to the active material cannot be improved, and problems such as lithium plating are likely to occur. If the depth h3 of the first groove 21 is greater than 40 μm, due to the too large depth of the first groove 21, more active material is removed, which is likely to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the depth h3 of the first groove 21 is in the range of 5 μm - 40 μm, thereby improving the charge and discharge performance of the battery.

[0148] The depth of the first groove 21 on the tab 30 is the same as the depth of the first groove 21 on the current collector 10, which is convenient for etching treatment by a laser.

[0149] In a possible implementation, the ratio range of the depth of the first groove 21 extending onto the tab 30 to the thickness of the active material layer 20 on the surface of the tab 30 is 0.1 - 0.8.

[0150] It should be noted that the above ratio can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., and there is no excessive limitation on the specific value.

[0151] In a possible implementation, the width of the first groove 21 extending onto the tab 30 is W3, and the range of W3 is 50 μm - 200 μm.

[0152] It should be noted that the width W3 can be 50μm, 75μm, 100μm, 125μm, 150μm, 175μm, 200μm, etc., and there is no excessive limitation on the specific value.

[0153] When the laser acts on the active material layer 20 beyond the edge of the current collector 10, it can play a smoothing role and improve the anti-folding ability of the tab 30.

[0154] Please refer to Figure 8 and Figure 9 In a possible implementation, the active material layer 20 includes a first active material layer 22 and a second active material layer 23. The first active material layer 22 and the second active material layer 23 are respectively located on opposite sides of the current collector 10 in the thickness direction.

[0155] As Figure 8 shown, in a possible implementation, on the surface of the current collector 10, the orthographic projection of the first groove 21 on the first active material layer 22 coincides with or is parallel to the orthographic projection of the first groove 21 on the second active material layer 23.

[0156] As Figure 9 shown, in a possible implementation, on the surface of the current collector 10, the orthographic projection of the first groove 21 on the first active material layer 22 intersects with the orthographic projection of the first groove 21 on the second active material layer 23.

[0157] There is an included angle between the major axis directions of the first groove 21 on the first active material layer 22 and the first groove 21 on the second active material layer 23. The included angle is θ3, and the range of θ3 is 60° - 120°.

[0158] It should be noted that the included angle θ3 can be 60°, 70°, 80°, 90°, 100°, 110°, 120°, etc., and there is no excessive limitation on the specific value.

[0159] As Figure 10 shown, in a possible implementation, along the stacking direction (perpendicular to the Figure 10 direction shown), the width of the projection of the edge of the active material layer 20 on the negative electrode sheet 102 in the laminated battery cell exceeding the projection of the edge of the active material layer 20 on the positive electrode sheet 101 is OH, and the range of OH is 0.1mm - 2mm.

[0160] It should be noted that the width OH can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, etc., and there are no specific excessive restrictions.

[0161] The active material layer 20 on the negative electrode sheet 102 has a first groove 21, which is beneficial to the insertion and extraction of Li ions of the positive electrode corresponding to the edge part of the negative electrode, and is beneficial to improving the capacity retention rate after long-term cycling of the battery.

[0162] In a possible implementation, the thickness of each layer on the electrode sheet 100 is uniform, and the groove depth is consistent.

[0163] As Figures 11 to 15 shown, in a possible implementation, the active material layer 20 has a normal area 24 and a thinning area 25. The thickness of the normal area 24 is basically uniform. The thickness of the thinning area 25 is smaller than the thickness of the normal area 24.

[0164] The thinning area 25 is located at the edge of the current collector 10 where the tab 30 is provided and / or on the tab 30.

[0165] As Figure 11 and Figure 12 shown, in a possible implementation, along the extension direction of the tab 30, the width of the thinning area 25 is H1, and the range of H1 is 1mm - 5mm.

[0166] It should be noted that the width H1 can be 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc., and there are no specific excessive restrictions.

[0167] The width H1 is greater than or equal to 1mm and less than or equal to 5mm. Such a setting mainly considers the performance of the battery. If the width H1 is less than 1mm, the thinning is less, and in the battery, the impact on the battery thickness is weak, and the overall thickness of the battery cannot be reduced, and it is also easy to cause a decrease in energy density. If the width H1 is greater than 5mm, due to excessive thinning, more active material is removed, which is easy to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the width H1 is in the range of 1mm - 5mm, so as to improve the charge and discharge performance of the battery.

[0168] In a possible implementation, the range of the difference between the thickness of the normal area 24 and the thickness of the thinning area 25 is 2um - 8um.

[0169] It should be noted that the above thickness difference can be 2um, 3um, 4um, 5um, 6um, 7um, 8um, etc., and there is no excessive limitation on the specific value.

[0170] In a possible implementation manner, along the extending direction of the tab 30, the width of the thinning area 25 on the surface of the tab 30 is H2, and the range of H2 is 0.1mm - 1.5mm.

[0171] It should be noted that the width H2 can be 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, etc., and there is no excessive limitation on the specific value.

[0172] The width H2 is greater than or equal to 0.1mm and less than or equal to 1.5mm. Such a setting mainly considers the performance of the battery. If the width H2 is less than 0.1mm, the thinning is less, and in the battery, the influence on the battery thickness is weak, and the overall thickness of the battery cannot be reduced, and it is also easy to cause a decrease in energy density. If the width H1 is greater than 1.5mm, due to excessive thinning, more active materials are removed, which is easy to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the width H2 is within the range of 0.1mm - 1.5mm, so as to improve the charge and discharge performance of the battery.

[0173] As Figure 13 , Figure 14 and Figure 15 shown, in a possible implementation manner, along the extending direction of the tab 30, the distance between the edge of the active material layer 20 on the tab 30 away from the current collector 10 and the first groove 21 on the side adjacent to this edge is H3.

[0174] H3 satisfies: 0.1mm ≤ H3 ≤ 1.5mm.

[0175] It should be noted that the distance H3 can be 0.1mm, 0.3mm, 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm, 1.5mm, etc., and there is no excessive limitation on the specific value.

[0176] As Figure 13 shown, the position of the first groove 21 is separated from the active material layer 20 on the tab 30, that is, the first groove 21 does not extend to the edge of the current collector 10.

[0177] As Figure 14 shown, the position of the first groove 21 is in contact with the active material layer 20 on the tab 30, that is, the first groove 21 extends to the edge of the current collector 10.

[0178] As Figure 15 shown, the position of the first groove 21 is on the active material layer 20 on the tab 30, that is, the first groove 21 extends to the tab 30.

[0179] The local thinning area 25 and the first groove 21 structure of the thinning area 25 provide space for the electrolyte to flow in from the side, improving the local electrolyte infiltration speed.

[0180] In a possible implementation, under the same area, the weight of the active material layer 20 in the thinning area 25 is G1, and the weight of the active material layer 20 in the normal area 24 is G2.

[0181] G1 and G2 satisfy: 0.5 ≤ G1 / G2 ≤ 1.

[0182] It should be noted that G1 / G2 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc., without specific excessive restrictions.

[0183] In a possible implementation, in the thinning area 25, the ratio of the depth of the first groove 21 to the thickness of the active material layer 20 ranges from 0.2 to 0.8.

[0184] It should be noted that the above thickness ratio can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, etc., without specific excessive restrictions.

[0185] In the thinning area 25, the thickness ratio is greater than or equal to 0.2 and less than or equal to 0.8. Such a setting mainly considers the performance of the battery. If the thickness ratio is less than 0.2, the first groove 21 is shallower, and in the battery, the improvement of the electrolyte infiltration of the active material is weak, and the wettability of the electrolyte to the active material cannot be improved, and problems such as lithium deposition are likely to occur. If the thickness ratio is greater than 0.8, due to the excessive depth of the first groove 21, more active material is removed, which is likely to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the thickness ratio is in the range of 0.2 - 0.8, thereby improving the charge and discharge performance of the battery.

[0186] In a possible implementation, in the normal area 24, the ratio of the depth of the first groove 21 to the thickness of the active material layer 20 ranges from 0.1 to 0.5.

[0187] It should be noted that the above thickness ratio can be 0.1, 0.2, 0.3, 0.4, 0.5, etc., without specific excessive restrictions.

[0188] The thickness ratio is greater than or equal to 0.1 and less than or equal to 0.5. Such a setting mainly considers the performance of the battery. If the thickness ratio is less than 0.1, the first groove 21 is relatively shallow, and in the battery, the improvement of the electrolyte wetting the active material is weak, the wettability of the electrolyte to the active material cannot be improved, and problems such as lithium plating are likely to occur. If the thickness ratio is greater than 0.5, due to the excessive depth of the first groove 21, more active material is removed, which is likely to cause a decrease in the energy density of the battery and affect the charge and discharge performance of the battery. Therefore, the thickness ratio is in the range of 0.1-0.5, thereby improving the charge and discharge performance of the battery.

[0189] The depth ratio of the first groove 21 in the thinning area 25 is greater than the depth ratio of the first groove 21 in the normal area 24. This is beneficial to strengthening the kinetic performance of the thinning area 25 and alleviating the lithium plating phenomenon caused by poor kinetic performance.

[0190] In a possible implementation manner, the electrode sheet 100 is a positive electrode sheet 101, and the positive electrode sheet 101 includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the surface of the positive electrode current collector. In the thickness direction of the positive electrode active material layer, the sizes of the positive electrode active material layers on the same side of the positive electrode current collector are the same, that is, on the positive electrode sheet 101, the thinning area 25 is not provided in the positive electrode active layer.

[0191] The electrode sheet 100 provided by the embodiment of the present application includes a current collector 10 and an active material layer 20 located on at least one side of the surface of the current collector 10. A tab 30 extending out of the current collector 10 is provided at one side edge of the current collector 10. A plurality of first recesses are provided on the active material layer 20, and a plurality of second recesses are provided on the tab 30. The depth of the first recess is greater than the depth of the second recess.

[0192] By providing the first recesses on the active material layer 20 on the surface of the current collector 10, the presence of the first recesses can increase the wetting speed of the electrolyte to the active material on the electrode sheet 100, improve the wettability of the electrolyte to the active material, expand the transmission path of lithium ions, and at the same time increase the liquid retention amount on the electrode sheet 100 and improve the rate performance of the battery cell. Moreover, by providing the second recesses on the tab 30, the presence of the second recesses at the tab 30 increases the surface roughness of the tab 30, thereby increasing the friction force between the tabs 30 during the pre-welding process, improving the welding effect, and increasing the welding yield.

[0193] In addition, the embodiment of the present application also provides a stacked battery cell, which includes a plurality of stacked positive electrode sheets 101, separators, and negative electrode sheets 102, and the negative electrode sheet 102 is the above-mentioned electrode sheet 100.

[0194] Among them, the stacked battery cell is not limited to lithium secondary batteries, and in the future, this technology may be applied to sodium secondary batteries, etc. The embodiment of the present application preferably uses lithium ion batteries.

[0195] After the positive electrode sheet 101, the separator, and the negative electrode sheet 102 are cut to a certain width, they are sequentially stacked in the housing.

[0196] The separator is used to prevent contact short - circuit between the positive electrode sheet 101 and the negative electrode sheet 102.

[0197] Among them, the specific structure, working principle, and function of the electrode sheet 100 have been described in detail in the foregoing embodiments, and will not be elaborated here. It should be noted that the preparation process of the electrode sheet 100 is as follows:

[0198] 1. Electrode sheet slitting: Use a slitting knife or a laser to slit the electrode sheet strip with a width of 300 - 650 mm into narrow - width electrode sheet strips with a width of 60 - 150 mm.

[0199] 2. Laser scribing: Scribe on the surface of the electrode sheet strip, with a line spacing of 1 - 2 mm and a wire groove with an angle of 30° - 60°.

[0200] 3. Electrode sheet die - cutting: After scribing, use a metal cutting knife or a laser on the electrode sheet strip to cut the long electrode sheet strip into individual electrode sheets 100.

[0201] In a possible implementation, the thickness of the stacked - film battery cell is k, and the range of k is 2.0 mm - 2.5 mm.

[0202] The distance between the first grooves is b1, and b1 and k satisfy: 0.4 ≤ b1 / k ≤ 2.5.

[0203] It should be noted that b1 / k can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, etc., and there is no specific excessive limitation.

[0204] b1 / k is greater than or equal to 0.4 and less than or equal to 2.5. Such a setting mainly considers the performance of the battery. If b1 / k is less than 0.4, the first grooves 21 are too dense, which is likely to cause powder - falling phenomenon, and the active materials removed by opening the first grooves 21 will be more, which is likely to cause a decrease in the energy density of the battery and affect the charge - discharge performance of the battery. If b1 / k is greater than 2.5, due to the first grooves 21 being too sparse, there are fewer first grooves 21 in the battery, and the improvement of the electrolyte wetting the active materials is weak, and it is impossible to improve the wettability of the electrolyte to the active materials, and problems such as lithium deposition are likely to occur. Therefore, b1 / k is in the range of 0.4 - 2.5, so as to improve the charge - discharge performance of the battery.

[0205] For thin stacked - film battery cells, the smaller the ratio of b1 / k, the better the electrolyte wetting performance, and the fast - charging performance of the thin battery cell is further improved.

[0206] The laminated battery cell provided by the embodiment of the present application has a first recess provided on the active material layer 20 on the surface of the current collector 10. The presence of the first recess can improve the wetting speed of the electrolyte on the active material of the electrode sheet 100, improve the wettability of the electrolyte on the active material, expand the transmission path of lithium ions, and at the same time increase the liquid retention amount on the electrode sheet 100, thereby improving the rate performance of the battery cell. Moreover, by providing a second recess on the tab 30, the presence of the second recess at the tab 30 increases the surface roughness of the tab 30, thereby increasing the frictional force between the tabs 30 during the pre-welding process, improving the welding effect, and increasing the welding yield.

[0207] On the other hand, the present application provides a battery, including a battery housing and the above-mentioned laminated battery cell, and the laminated battery cell is located in the battery housing.

[0208] Among them, the specific structure, working principle, and functions of the electrode sheet 100 have been described in detail in the foregoing embodiments, and will not be elaborated here. It should be noted that the preparation process of the lithium-ion battery is as follows:

[0209] Embodiment 1

[0210] The first step is to prepare the positive electrode sheet 101: The positive electrode active material lithium cobaltate, binder PVDF, and conductive carbon black are dispersed in N-methylpyrrolidone to obtain a uniform positive electrode active material slurry; in the positive electrode active material layer slurry, the solid components include 97 wt% of lithium cobaltate, 2 wt% of binder PVDF, and 1 wt% of conductive agent. A coater is used to coat the active material layer, and the coating width direction includes a coated area and an uncoated area, and the coated area extends to the tab. After drying and rolling, a 300-mm-wide positive electrode sheet is slit into 60-mm-wide narrow positive electrode sheets using a slitter or a laser. Scoring is performed on the surface of the positive electrode sheet, with a line spacing of 0.5 mm, a wire groove with an angle of 30°, a wire groove width of 50 μm, a depth of 5 μm on the active material layer, and a depth of 1 μm at the tab. After scoring, the electrode sheet is die-cut to obtain positive electrode small pieces of a certain size and shape.

[0211] Step 2: Preparation of the negative electrode sheet 102: Graphite, binder styrene-butadiene rubber, thickener sodium carboxymethyl cellulose, and conductive agent conductive carbon black are mixed and dispersed in deionized water to obtain a negative electrode slurry; in the negative electrode slurry, the solid components include 97 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose, 0.5 wt% of conductive carbon black, and 1 wt% of styrene-butadiene rubber. The solid content in the negative electrode slurry is 40 - 45 wt%; the negative electrode slurry is evenly coated on both sides of the copper foil, and in the width direction of the coating, there are coating areas and uncoated areas, and the coating area extends to the tab. After drying and rolling, the rolled negative electrode sheet is obtained. The 300 mm wide negative electrode sheet strip is slit with a slitter or a laser into 60 mm wide narrow negative electrode sheet strips. Scoring is performed on the surface of the negative electrode sheet strip, the line spacing is 0.5 mm, the groove has an angle of 30°, the groove width is 50 μm, the depth in the active material layer is 5 μm, and the depth at the tab is 1 μm. The rolled negative electrode sheet is thinned by a laser method or other physical and mechanical methods, and a thinning area 25 is obtained on the negative electrode sheet. The thinning area 25 is located at the edge of the tab on the negative electrode sheet strip, the width of the thinning area 25 is 1 mm, and the width of the thinning area 25 at the tab is 0.1 mm. The electrode sheet is die-cut to obtain negative electrode small pieces of a certain size and shape.

[0212] Step 3: Preparation of the lithium-ion battery: The prepared positive electrode small pieces, separator, and negative electrode small pieces are stacked in sequence, and the tabs of the positive electrode sheet 101 and the negative electrode sheet 102 are welded separately to form solder joints. The width of the solder joints is 0.2 mm, and the spacing between the solder joints is 0.3 mm to obtain a stacked cell. It is encapsulated with an aluminum-plastic film, baked for 24 h in a vacuum state to remove moisture, then electrolyte is injected, and then the battery is formed, vacuum sealed, and sorted to obtain a soft-pack lithium-ion battery.

[0213] Among them, the electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0214] Example 2

[0215] The difference from Example 1 is that the scoring angle on the positive and negative electrode sheets is 60°, and the others are the same as in Example 1.

[0216] Example 3

[0217] The difference from Example 1 is that the width of the solder joints is 1 mm, and the spacing between the solder joints is 1.5 mm, and the others are the same as in Example 1.

[0218] Example 4

[0219] The difference from Example 1 is that for the scoring on the positive and negative electrode sheets, the line spacing is 5 mm, the groove width is 200 μm, the depth in the active material layer is 40 μm, and the depth at the tab is 4 μm, and the others are the same as in Example 1.

[0220] Example 5

[0221] It is different from Example 1 in that the coating area does not extend to the tab, and the rest is the same as Example 1.

[0222] Example 6

[0223] It is different from Example 1 in that the width of the thinning area 25 of the negative electrode sheet is 5 mm, and the width of the thinning area 25 at the tab is 1.5 mm, and the rest is the same as Example 1.

[0224] Example 7

[0225] It is different from Example 1 in that the negative electrode sheet is not thinned, and the rest is the same as Example 1.

[0226] Comparative Example 1

[0227] After rolling the positive and negative electrode sheets, neither scribing nor thinning treatment is carried out, that is, neither laser nor other physical and mechanical methods are used for treatment, and then directly cut and die-cut to obtain positive and negative small pieces of a certain size and shape. The rest is the same as Example 1.

[0228] It should be noted that the following is a table for comparing the data of the shedding test, cycle life and capacity retention rate of the batteries prepared in each example and comparative example.

[0229] Table 1 is the data table of each example and comparative example test

[0230]

[0231] Among them, the statistical method for the tab shedding ratio is as follows:

[0232] Take 1000 batteries. After disassembling, use a CCD microscope to observe and count the number n of tabs shed on each electrode sheet. The shedding ratio P is calculated by the formula P = n / 1000.

[0233] The test method for the cycle life is as follows:

[0234] Place the battery in an environment of (25 ± 3) °C and let it stand for 3 hours. When the cell body reaches (25 ± 3) °C, charge the battery at 2C to 4.25V, then charge it at 0.7C to 4.48V, then charge it at a constant voltage of 4.48V until the cut-off current of 0.05C, and then discharge it at 1C to 3V, and record the initial capacity Q0. When the cycle reaches the required number of times or the capacity attenuation rate is lower than 70%, use the previous discharge capacity as the capacity Q2 of the battery, and calculate the capacity retention rate (%):

[0235] Capacity retention rate (%) = Q2 / Q0 × 100%.

[0236] As shown in Table 1, the comparison between Comparative Example 1 and the Examples shows that scribing on the active material layer 20 can affect the cycle life and capacity retention rate of the battery. Moreover, by scribing on the tab 30, the proportion of the tabs falling off after welding is significantly reduced.

[0237] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than 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 cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A pole piece, characterized in that: It includes a current collector and an active material layer located on at least one side of the current collector surface, wherein an edge of one side of the current collector is provided with a pole ear extending from the current collector, the active material layer contains a plurality of first recesses, and the pole ear contains a plurality of second recesses, and the depth of the first recess is greater than the depth of the second recess.

2. The pole piece according to claim 1, characterized in that: The first recess comprises a first groove, the angle between the long axis direction of the first groove and the extension direction of the pole ear is θ1, and the range of θ1 is 30°-60°; and / or, The second recess includes a second groove, and an angle θ2 between a long axis direction of the second groove and an extending direction of the pole tab is in a range of 30°-60°.

3. The pole piece according to claim 1, characterized in that: The surface of the pole lug is provided with welding spots, and some of the welding spots are located in the second recess.

4. The pole piece according to claim 3, characterized in that: The width of the welding spot is a1, and the range of a1 is 0.2mm-1mm; and / or, The distance between the welding points is L, and the range of L is 0.3mm-1.5mm; and / or, The overlap rate between the welding point and the second concave portion is 50%-100%.

5. The pole piece according to claim 1, characterized in that: The active material layer includes a first active material layer and a second active material layer, wherein the first active material layer and the second active material layer are respectively located on two opposite sides of the current collector in a thickness direction; On the surface of the current collector, an orthographic projection of the first concave portion on the first active material layer coincides with or is parallel to an orthographic projection of the first concave portion on the second active material layer; or On the surface of the current collector, an orthographic projection of the first concave portion on the first active material layer intersects with an orthographic projection of the first concave portion on the second active material layer.

6. The pole piece according to claim 1, characterized in that: The depth of the first concave portion is h1, and the range of h1 is 5 μm-40 μm; and / or, The width of the first concave portion is W1, and the range of W1 is 50 μm-200 μm; and / or, The spacing between the first recesses is b1, and the range of b1 is 0.5 mm-5 mm.

7. The pole piece according to claim 1, characterized in that: The depth of the second concave portion is h2, h2≤4 μm; and / or, The width of the second concave portion is W2, and the range of W2 is 50 μm-200 μm.

8. The pole piece according to claim 1, characterized in that: The depth h2 of the second concave groove is ≤1 μm.

9. The pole piece according to claim 1, characterized in that: The depth of the first concave portion is h1, and the depth of the second concave portion is h2. h1 and h2 satisfy: h1=k×h2+b, the value range of k is 20-50, and the value range of b is 5-10.

10. The pole piece according to claim 1, characterized in that: The active material layer extends to the surface of the tab.

11. The pole piece according to claim 10, characterized in that: Along the extension direction of the electrode ear, the width of the active material layer beyond the edge of the current collector is b2, and the range of b2 is 0.1mm-1.5mm; and / or, The thickness of the active material layer on the surface of the current collector is t1, and the range of t1 is 30 μm-70 μm; and / or, The thickness of the active material layer on the surface of the electrode tab is t2, and the range of t2 is 30 μm-70 μm.

12. The pole piece according to claim 10, characterized in that: The first recessed portion extends to the pole lug, and the depth of the first recessed portion extending to the pole lug is h3, and the range of h3 is 5 μm-40 μm; and / or, The ratio of the depth of the first recess extending to the tab to the thickness of the active material layer on the surface of the tab is in the range of 0.1-0.

8.

13. The pole piece according to claim 10, characterized in that: The active material layer has a normal area and a thinned area, the thickness of the thinned area is smaller than the thickness of the normal area, and the thinned area is located at the edge of the current collector where the pole ear is provided and / or on the pole ear.

14. The pole piece according to claim 13, characterized in that: Along the extension direction of the tab, the width of the thinned area is H1, and the range of H1 is 1 mm-5 mm; and / or, The difference between the thickness of the normal area and the thickness of the thinned area is in the range of 2um-8um; and / or, Along the extension direction of the pole lug, the width of the thinned area on the surface of the pole lug is H2, and the range of H2 is 0.1mm-1.5mm.

15. The pole piece according to claim 13, characterized in that: Along the extension direction of the electrode tab, the distance between the edge of the active material layer on the electrode tab away from the current collector and the first recessed portion adjacent to the edge is H3, and H3 satisfies: 0.1 mm≤H3≤1.5 mm.

16. The pole piece according to claim 13, characterized in that: Under the same area, the weight of the active material layer in the thinned area is G1, and the weight of the active material layer in the normal area is G2, and G1 and G2 satisfy: 0.5≤G1 / G2≤1.

17. The pole piece according to claim 13, characterized in that: In the thinning area, the ratio of the depth of the first recess to the thickness of the active material layer is in the range of 0.2-0.8; and / or, In the normal region, a ratio of the depth of the first recess to the thickness of the active material layer is in a range of 0.1-0.

5.

18. The pole piece according to claim 1, characterized in that: The electrode sheet is a positive electrode sheet, which includes a positive electrode collector and a positive electrode active material layer located on at least one side of the surface of the positive electrode collector. In the thickness direction of the positive electrode active material layer, the positive electrode active material layers located on the same side of the positive electrode collector have the same size.

19. A laminated battery cell, characterized in that: It comprises a plurality of stacked positive electrode sheets, a separator and a negative electrode sheet, wherein the negative electrode sheet is the electrode sheet according to any one of claims 1 to 18.

20. The laminated battery cell according to claim 19, characterized in that: Along the stacking direction, the projection of the edge of the active material layer on the negative electrode sheet exceeds the projection of the edge of the positive electrode sheet by a width OH, and the range of OH is 0.1 mm-2 mm.

21. The laminated battery cell according to claim 19, characterized in that: The thickness of the laminated battery core is k, the spacing between the first recesses is b1, and b1 and k satisfy: 0.4≤b1 / k≤2.

5.

22. A battery, characterized in that: It comprises a battery casing and a laminated battery core as described in any one of claims 19 to 21, wherein the laminated battery core is located in the battery casing.

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