Secondary battery and electronic apparatus

Abstract

A secondary battery and an electronic apparatus. The secondary battery (100) comprises an electrode assembly (20) and a tab (30), the electrode assembly (20) comprising an anode piece (22), and the anode piece (22) comprising a current collector (221) and an active layer (222). The secondary battery (100) is provided with a notch. The electrode assembly (20) further comprises a first end face (201), a first side face (202), a second side face (203), a third side face (204), a second end face (205), and a fourth side face (206), which are connected in sequence. The tab (30) protrudes from the first end face (201) along a first direction. The first end face (201) and the second end face (205) are oppositely arranged in the first direction, the third side face (204) and the fourth side face (206) are oppositely arranged in a second direction, and the first side face (202), the second side face (203) and the third side face (204) are located on the same side of the electrode assembly (20) in the second direction. The first side face (202) and the second side face (203) surroundingly form the notch. The current collector (221) comprises a first edge (221a) located at the third side face (204), and a second edge (221b) located at the fourth side face (206). The active layer (222) comprises a first area (220) provided with multiple strip-shaped grooves (22a). The first area (220) covers the first edge (221a) and extends towards the second edge (221b), and the width of the first area (220) in the second direction is greater than or equal to 3 mm.

Description

Secondary batteries and electronic devices Technical Field

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

[0002] During the design process of electronic products, after completing the layout of electronic components, the space left for the battery may not be a regular shape, but rather an irregular shape such as an L or T. This requires the development of specially shaped batteries to match the space to improve the space utilization of the electronic product. Secondary batteries are widely used in electric vehicles and consumer electronics due to their advantages such as high energy density, high output power, and long cycle life. However, irregularly shaped lithium-ion batteries are prone to lithium deposition during use, which affects their cycle performance.

[0003] Summary of the Invention

[0004] The inventors discovered that when vacuuming a special-shaped lithium-ion battery to remove excess electrolyte in the packaging bag, the tail on the narrower side in the length direction is far away from the vacuum position, and the electrolyte at the tail is not easily extracted, causing the tail to become an electrolyte accumulation area, which easily causes the impedance of the local area of ​​the tail to increase, resulting in lithium deposition at the tail, and affecting the cycle performance.

[0005] One purpose of the present application is to provide a special-shaped secondary battery and an electronic device that can improve cycle performance.

[0006] In a first aspect, the present application provides a secondary battery, comprising a packaging bag, an electrode assembly, and a tab. The electrode assembly is contained within the packaging bag and includes an anode electrode sheet. The anode electrode sheet includes a current collector and an active layer disposed on at least one surface of the current collector. The packaging bag has a first recess. The electrode assembly further includes a first end face, a first side face, a second side face, a third side face, a second end face, and a fourth side face connected in sequence. The tab protrudes from the first end face along a first direction and extends outside the packaging bag. The first end face and the second end face are disposed opposite each other in the first direction. The third side face and the fourth side face are disposed opposite each other in a second direction perpendicular to the first direction. The first side face, the second side face, and the third side face are located on the same side of the electrode assembly in the second direction. The first side face and the second side face enclose a second recess, the second recess is disposed around the first recess, and the shape of the second recess matches the shape of the first recess. In the second direction, the anode electrode includes a first part and a second part arranged in sequence, the first part is connected to the second part and is surrounded to form a second recess, the first part includes a first edge located on the third side, and the second part includes a second edge located on the fourth side; the active layer includes a first area provided with a plurality of strip grooves, the first area covers the first edge and extends toward the second edge, at least one strip groove is located in the first part, and the width of the first area in the second direction is greater than or equal to 3 mm.

[0007] The present application provides a special-shaped secondary battery with a notch, in which a plurality of strip-shaped grooves are arranged in a first area covering a first edge on the active layer, and at least one strip-shaped groove is located on a first portion of the anode electrode close to the first edge. The strip-shaped grooves reserve space for electrolyte transmission, thereby improving the transmission capacity of the electrolyte at the location of the first edge, improving the lithium plating phenomenon caused by electrolyte enrichment at the location of the first edge, and improving the cycle performance.

[0008] According to some embodiments of the present application, in the second direction, the distance between the third side surface and the fourth side surface is L1; in the first direction, the distance between the first end surface and the second end surface is L2, and 1.0≤L1 / L2≤3.0. When L1 / L2 < 1, L1 is small. When the air bag is evacuated from the side of the packaging bag close to the fourth side surface, the path between the air bag and the first edge is small, the electrolyte is not easy to accumulate at the location of the first edge, and lithium precipitation caused by electrolyte enrichment is not easy to occur. When L1 / L2 > 3, L1 is too large, resulting in a large path between the air bag and the first edge. Although the provision of strip grooves in the first area can improve the cycle performance, the cycle performance is still poor and cannot meet the higher requirements of the secondary battery for cycle performance.

[0009] According to some embodiments of the present application, the spacing between two adjacent strip grooves is D1, and the depth of the strip grooves is D2, 50μm≤D1≤3000μm; and / or, 1μm≤D2≤40μm. When D1 is less than 50μm, D1 is too small and difficult to process; when D1 is greater than 3000μm, under the condition of a certain electrode area, the number of strip grooves is small, and the improvement effect on the electrolyte transmission capacity is limited, and the improvement effect on the lithium plating problem is limited. When D2 is less than 1μm, the depth of the strip grooves is too small, and when etching to form the strip grooves, it is easy to cause etching to not penetrate, affecting the electrolyte transmission performance and the cycle performance, and the too small D2 has a limited effect on improving the cycle performance; when D2 is greater than 40μm, the depth of the strip grooves is too large, and it is easy to cause excessive etching, resulting in the anode capacity being less than the cathode capacity, causing the lithium plating problem at the location of the strip grooves, and the effect of improving the cycle performance is limited.

[0010] According to some embodiments of the present application, 200 μm≤D1≤1700 μm; and / or 5 μm≤D2≤25 μm.

[0011] According to some embodiments of the present application, the strip-shaped groove is arranged perpendicularly, parallel to, or obliquely relative to the first edge.

[0012] According to some embodiments of the present application, the included angle between the strip-shaped groove and the first edge is θ, 0°<θ<90°.

[0013] According to some embodiments of the present application, the pole tab is integrally arranged with the current collector, the second part includes a third edge located on the first end face, the strip-shaped groove includes a first end located on one side of the pole tab in the first direction, and along the first direction, the minimum distance between the third edge and the first end is 0 to 3 mm, thereby reducing damage to the pole tab when processing to form the strip-shaped groove.

[0014] According to some embodiments of the present application, a plurality of strip-shaped grooves are evenly spaced apart in the first region.

[0015] According to some embodiments of the present application, the packaging bag includes a first packaging part and a second packaging part that are integrally arranged. The first packaging part and the second packaging part are interconnected to form a main body part for accommodating the electrode assembly and a sealing part that seals the main body part, and extends from the inside of the main body part through the sealing part.

[0016] According to some embodiments of the present application, the active layer includes an anode active material, and the anode active material includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxides, silicon-carbon composites, lithium titanate, and metals that can form alloys with lithium.

[0017] According to some embodiments of the present application, the electrode assembly further includes a cathode electrode sheet and a separator, and the anode electrode sheet, the separator and the cathode electrode sheet are stacked in sequence to form a laminate structure.

[0018] According to some embodiments of the present application, the secondary battery is L-shaped.

[0019] A second aspect of the present application provides an electronic device comprising any of the above-mentioned secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG1 is a schematic diagram of a secondary battery provided in one embodiment of the present application viewed along a third direction.

[0021] FIG2 is a schematic diagram of a secondary battery before assembly provided in one embodiment of the present application.

[0022] FIG3 is a schematic diagram of an electrode assembly provided in accordance with an embodiment of the present application.

[0023] FIG4 is a schematic diagram of an anode electrode provided by one embodiment of the present application observed along a third direction.

[0024] FIG5 is a schematic diagram of an anode electrode provided in one embodiment of the present application.

[0025] FIG6 is a schematic diagram of an anode electrode provided in another embodiment of the present application observed along a third direction.

[0026] FIG7 is a schematic diagram of an anode electrode provided in another embodiment of the present application observed along a third direction.

[0027] FIG8 is a schematic diagram of an anode electrode provided in another embodiment of the present application observed along a third direction.

[0028] Description of Main Component Symbols Secondary Battery 100 Packaging Bag 10 First Packaging Portion 10a First Region 10a1 Second Region 10a2 Second Packaging Portion 10b Third Region 10b1 Fourth Region 10b2 First Recess S1 Second Recess S2 Electrode Assembly 20 Tab 30 First Recess 101 Second Recess 210 First End Wall 11 First Side Wall 12 Second Side Wall 13 Third Side Wall 14 Second End Wall 15 Fourth Side Wall 16 Cathode Pole Sheet 21 Anode Pole Sheet 22 Separator 23 Cathode Current Collector 211 Cathode Active Layer 212 Current Collector 221 Active Layer 222 First End Surface 201 First Side Surface 202 Second Side Surface 203 Third Side Surface 204 Second End Surface 205 Fourth Side Surface 206 First Edge 221a Second Edge 221b Strip-Shaped Groove 22a First Region220 Third edge 221c Fourth edge 221d First end 22a1 Second end 22a2 First direction X Second direction Y Third direction Z

[0029] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0031] Below, embodiments of the present application will be described in detail. However, the present application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments illustrated herein. Rather, these exemplary embodiments are provided to make the present application thorough and detailed for those skilled in the art.

[0032] In addition, for the sake of brevity and clarity, the size or thickness of various components, layers may be amplified in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, or when element A is referred to as "connecting" to element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0033] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0034] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0035] It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part without departing from the teachings of the exemplary embodiments.

[0036] Referring to FIG. 1 , one embodiment of the present application provides a secondary battery 100 comprising a packaging bag 10, an electrode assembly 20, an electrolyte, and a tab 30. The electrode assembly 20 and the electrolyte are contained in the packaging bag 10. The tab 30 is connected to the electrode assembly 20 and extends from one side of the packaging bag 10 along a first direction X for connection to external components. In this embodiment, there are two tabs 30, namely a cathode tab and an anode tab, and the two tabs 30 are located on the same side of the secondary battery 100. In this application, the first direction X is the width direction of the secondary battery 100.

[0037] The packaging bag 10 has a first recess 101. The first recess 101 is used to accommodate external components for the secondary battery 100, thereby improving space utilization. In this embodiment, the secondary battery 100 is L-shaped. In other embodiments, the secondary battery 100 can be a T-shaped or other special-shaped structure.

[0038] The packaging bag 10 includes a first end wall 11, a first side wall 12, a second side wall 13, a third side wall 14, a second end wall 15, and a fourth side wall 16, which are connected end to end in sequence. The tab protrudes from the first end wall 11 along a first direction X, and the second end wall 15 and the first end wall 11 are arranged opposite each other in the first direction. The first side wall 12, the second side wall 13, and the third side wall 14 are located on the same side of the packaging bag 10 in a second direction Y perpendicular to the first direction X, and the fourth side wall 16 and the third side wall 14 are arranged opposite each other in the second direction Y. The first side wall 12 and the second side wall 13 are arranged to form a first recess 101. In this application, the second direction Y is the longitudinal direction of the secondary battery.

[0039] Referring to Figure 2 , the packaging bag 10 includes an integrally formed first packaging portion 10a and a second packaging portion 10b, which are sealed together. For example, the first packaging portion 10a and the second packaging portion 10b are formed by folding a single piece of packaging film in half. The first packaging portion 10a includes a first region 10a1 and a second region 10a2 connected to each other. The first region 10a2 has three sides surrounded by the first region 10a1. The second packaging portion 10b includes a third region 10b1 and a fourth region 10b2 connected to each other. The third region 10b1 surrounds the fourth region 10b2 on three sides. The second region 10a2 of the first packaging portion 10a is provided with a first recess S1 for accommodating the electrode assembly 20, while the fourth region 10b2 of the second packaging portion 10b is provided with a second recess S2 for accommodating the electrode assembly 20. The first recess S1 and the second recess S2 together form the main body for accommodating the electrode assembly 20. The first area 10a1 and the third area 10b1 are connected to form a sealing portion. The tab 30 extends from the interior of the main body through the sealing portion. In another embodiment, the first packaging portion 10a and the second packaging portion 10b are provided separately.

[0040] Referring to FIG3 , the electrode assembly 20 includes a cathode electrode sheet 21, an anode electrode sheet 22, and a separator 23 disposed between the cathode electrode sheet 21 and the anode electrode sheet 22. The cathode electrode sheet 21, the separator 23, and the anode electrode sheet 22 are stacked in sequence along a third direction Z to form a laminate structure. The first direction X, the second direction Y, and the third direction Z are mutually perpendicular.

[0041] The cathode electrode 21 includes a cathode current collector 211 and a cathode active layer 212 disposed on at least one surface of the cathode current collector 211. In this embodiment, the cathode active layer 212 is disposed on two opposing surfaces of the cathode current collector 211. The cathode current collector 211 includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof. The cathode active layer 212 includes a cathode active material, which may include at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and combinations thereof.

[0042] The anode electrode 22 includes a current collector 221 and an active layer 222 disposed on at least one surface of the current collector 221. In this embodiment, the active layer 222 is disposed on two opposing surfaces of the current collector 221. The current collector 221 includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof. The active layer 222 includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxides, silicon-carbon composites, lithium titanate, and metals capable of forming alloys with lithium.

[0043] 1 and 2 , the electrode assembly 20 has a second recess 210. The second recess is arranged around the first recess 101, and the shape of the second recess 210 matches the shape of the first recess 101. In this embodiment, the shape of the second recess 210 is substantially the same as the shape of the first recess 101. When manufacturing the secondary battery 100, the first recess 101 of the packaging bag 10 is defined by the second recess 210 of the electrode assembly 20. In some embodiments, the electrode assembly 20 is L-shaped. In other embodiments, the electrode assembly 20 can be a T-shaped or other special-shaped structure.

[0044] The electrode assembly 20 includes a first end face 201, a first side face 202, a second side face 203, a third side face 204, a second end face 205, and a fourth side face 206, which are connected end to end. The tab protrudes from the first end face 201 along a first direction X, and the second end face 205 and the first end face 201 are arranged opposite each other in the first direction. The first side face 202, the second side face 203, and the third side face 204 are located on the same side of the electrode assembly 20 in a second direction Y perpendicular to the first direction X, and the fourth side face 206 and the third side face 204 are arranged opposite each other in the second direction Y. The first end surface 201 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the first end wall 11 in the first direction X. The first side surface 202 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the first side wall 12 in the second direction Y. The second side surface 203 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the second side wall 13 in the second direction Y. The third side surface 204 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the third side wall 14 in the second direction Y. The second end surface 205 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the second end wall 15 in the first direction X. The fourth side surface 206 is formed by the edge of the cathode electrode piece 21, the anode electrode piece 22, and the diaphragm 23 located on the side of the fourth side wall 16 in the second direction Y. The first side surface 202 and the second side surface 203 enclose a second recess 210.

[0045] Referring to Figure 4 , in the second direction Y, the anode plate 22 includes a first portion 223 and a second portion 224 arranged sequentially. The first portion 223 extends from one side of the second portion 224 and surrounds the second portion 224 to form a second recess 210. The first portion 223 includes a first edge 221a located on the third side 204. The second portion 224 includes a second edge 221b located on the fourth side 206. The active layer 222 includes a first region 220 having a plurality of strip-shaped grooves 22a. The first region 220 covers the first edge 221a and extends along the second direction Y toward the second edge 221b. In this application, the end of the plurality of strip-shaped grooves 22a farthest from the first edge 221a in the second direction Y serves as the boundary extending from the first region 220 toward the second edge 221b. In the second direction Y, the width of the first region 220 is greater than or equal to 3 mm. At least one strip-shaped groove 22a is located in the first portion 223. When the air bag is vacuumed from the side of the packaging bag close to the fourth side 206, the strip groove 22a reserves space for electrolyte transmission, thereby improving the transmission capacity of the electrolyte at the position of the first edge 221a to the air bag, improving the lithium deposition phenomenon at the position of the first edge 221a, and thus improving the cycle performance.

[0046] Referring to FIG4 , a plurality of strip-shaped grooves 22a are arranged parallel to each other. When viewed along the third direction Z, the distance between two adjacent strip-shaped grooves 22a is D1. In the present application, the distance D1 between two adjacent strip-shaped grooves 22a refers to the distance between the geometric center lines of the two adjacent strip-shaped grooves. In some embodiments, 50 μm ≤ D1 ≤ 3000 μm. The strip-shaped grooves 22a are formed by removing a portion of the active layer 222. Any conventional technique can be used to remove a portion of the active layer 222, such as by a laser etching process. When D1 is less than 50 μm, D1 is too small, which is difficult to achieve due to limitations in processing equipment (such as lasers) and has low production efficiency. In addition, when D1 is too small, the contact area between the electrode and the diaphragm is reduced, the bonding force is reduced, and the electrode-diaphragm delamination problem is caused. When D1 is greater than 3000 μm, given a certain electrode area, the number of strip-shaped grooves is small, and the effect of improving the electrolyte transport capacity is limited, the effect of improving the lithium plating problem is limited, and the effect of improving the cycle performance is limited. Preferably, 200 μm ≤ D1 ≤ 1700 μm, which is more conducive to improving the lithium plating problem and significantly improving the cycle performance.

[0047] Referring to FIG. 4 , in some embodiments, the plurality of strip-shaped grooves 22 a are evenly spaced in the first region 220. That is, the spacing D1 between any two adjacent strip-shaped grooves 22 a is equal. In other embodiments, the spacing D1 between any two adjacent strip-shaped grooves 22 a may be unequal, or the spacing D1 between some adjacent strip-shaped grooves 22 a may be equal, while the spacing D1 between other adjacent strip-shaped grooves 22 a may be unequal.

[0048] Referring to FIG. 4 , in the second direction Y, the distance between the third side surface 204 and the fourth side surface 206 is L1. In the first direction X, the distance between the first end surface 201 and the second end surface 205 is L2. In some embodiments, 1.0≤L1 / L2≤3.0. When L1 / L2>1, L1 is small, which is beneficial for the air bag to be vacuumed from the side of the packaging bag close to the fourth side surface 206. The path between the air bag and the first edge 221a is small, and the electrolyte is not easily accumulated at the location of the first edge 221a, and lithium precipitation caused by electrolyte enrichment is not easily caused. When L1 / L2>3, L1 is too large, resulting in an excessively large path between the air bag and the first edge 221a. Although the provision of the strip-shaped groove 22a in the first region 220 can improve the cycle performance, the cycle performance is still poor and cannot meet the cycle performance requirements of the secondary battery.

[0049] Referring to Figures 4 and 5 , the second portion 224 further includes a third edge 221c located on the first end surface 201 and a fourth edge 221d located on the second end surface 205. The strip-shaped groove 22a includes a first end 22a1 located on one side of the first end surface 201 and a second end 22a2 located on one side of the second end surface 205. In some embodiments, the tab 30 is integrally formed with the current collector 221. In the first direction X, the minimum distance between the third edge 221c and the first end 22a1 is 0 to 3 mm, reducing the risk of etching the tab 30 during machining of the strip-shaped groove 22a. In some embodiments, when the minimum distance between the third edge 221c and the first end 22a1 is 0, and the minimum distance between the fourth edge 221d and the second end 22a2 is 0, the strip-shaped groove 22a extends through the anode plate 22 in the first direction X.

[0050] Referring to Figure 5 , in the third direction Z, the depth of the strip groove 22a is D2, and the thickness of the active layer 222 is D3. In this application, the depth of the strip groove 22a refers to the distance between the deepest point of the strip groove 22a and the surface of the active layer 222. In some embodiments, D2 < D3. When D2 ≥ D3, excessive etching may cause damage to the current collector 221 and may also cause the anode capacity to be less than the cathode capacity, causing lithium deposition problems at the location of the strip groove 22a.

[0051] In some embodiments, 1μm≤D2≤40μm. When D2 is less than 1μm, the depth of the strip groove 22a is too small. When etching to form the strip groove 22a, it is easy to cause etching to not penetrate, affecting the transmission performance of the electrolyte and affecting the cycle performance. When D2 is greater than or equal to 40μm, the depth of the strip groove 22a is too large. When etching to form the strip groove 22a, it is easy to cause excessive etching, resulting in the anode capacity being less than the cathode capacity, causing lithium deposition problems at the location of the strip groove 22a. Preferably, 5μm<D2<25μm, which is more conducive to improving the lithium deposition problem and cycle performance. It should be noted that in this application, when the energy density remains unchanged, that is, when the mass loss of the active layer removed to form the strip groove is fixed, the conditions to be met for obtaining the depth D2 of the strip groove and the distance D1 between two adjacent strip grooves are obtained.

[0052] Referring to FIG. 4 , in the second direction Y, the distance between the third side surface 204 and the fourth side surface 206 is L1, and the width of the first region 220 is L3. In some embodiments, L3 / L1 is less than 1, meaning that the plurality of strip-shaped grooves 22a are distributed throughout a portion of the active layer 222. Referring to FIG. 6 , in another embodiment, L3 / L4 is equal to 1, meaning that the plurality of strip-shaped grooves 22a are distributed throughout the active layer 222. This further enhances electrolyte transport, improves lithium plating, and enhances cycle performance.

[0053] Referring to FIG4 , the strip-shaped groove 22a is disposed parallel to the first edge 221a. Referring to FIG7 , in another embodiment, the strip-shaped groove 22a is disposed perpendicular to the first edge 221a. Referring to FIG8 , in another embodiment, the strip-shaped groove 22a is disposed obliquely relative to the first edge 221a, and the angle θ between the strip-shaped groove 22a and the first edge 221a satisfies 0°<θ<90°. Preferably, θ=45°, which further improves the lithium deposition effect.

[0054] One embodiment of the present application further provides an electronic device comprising any of the above-described secondary batteries. The electronic device of the present application may include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0055] The performance of the secondary battery provided in this application is described below through specific examples and comparative examples.

[0056] Example 1

[0057] Preparation of the cathode electrode: The cathode active material (lithium cobalt oxide), conductive agent (conductive carbon black), and binder (polyvinylidene fluoride) are dissolved in N-methylpyrrolidone solution at a weight ratio of 97.5:1:1.5 to form a cathode slurry with a solid content of 75%. Using aluminum foil as a current collector, the cathode slurry is applied to the surface of the cathode current collector to form the cathode active layer. Anode electrodes are then cold pressed and cut.

[0058] Preparation of the anode electrode: The anode active material (graphite), conductive agent (conductive carbon black), thickener (sodium carboxymethyl cellulose), and binder (styrene-butadiene rubber) are mixed in a mass ratio of 97.5:1:0.5:1, and then deionized water is added as a solvent and stirred evenly to obtain an anode slurry with a solid content of 50wt%. Copper foil is used as a current collector, and the anode slurry is coated on the surface of the anode current collector to obtain an anode active layer. Subsequently, the anode electrode is obtained by cold pressing and cutting. A laser etching process is used to etch a plurality of strip grooves on the anode active layer. The plurality of strip grooves are distributed throughout the anode active layer, and the strip grooves are arranged parallel to the first edge of the anode current collector. The structure of the anode electrode is shown in Figure 3. The ratio of the length L1 to the width L2 of the anode electrode is 2.

[0059] Preparation of diaphragm: Polyethylene film is selected as the diaphragm.

[0060] Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) are mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 and the organic solvent are mixed in a weight ratio of 8:92 to obtain an electrolyte.

[0061] Preparation of lithium-ion batteries: The cathode electrode, polyethylene separator, and anode electrode are stacked in sequence, with the separator located between the cathode and anode electrodes to obtain an electrode assembly; the electrode assembly is placed in an aluminum-plastic film packaging bag, hot-pressed and bonded at a preset pressure, and a lithium-ion battery is obtained after liquid injection and formation.

[0062] Examples 2-21, Comparative Example 7

[0063] The difference from Example 1 is that at least one of the following parameters is different: the distance L1 between the third and fourth side surfaces of the electrode assembly, the distance L2 between the first and second end surfaces of the electrode assembly, the width L3 of the first region, the distance D1 between two adjacent strip-shaped grooves, or the depth D2 of the strip-shaped grooves. In each example, the mass loss of the active layer removed to form the strip-shaped grooves is fixed at 1.5 wt%. See Table 1 for specific parameters.

[0064] Comparative Examples 1-6

[0065] The difference from Example 1 is that the anode active layer is not etched to form a plurality of strip-shaped grooves.

[0066] The test methods for various parameters of this application are described below.

[0067] (1) Test of the depth D2 of the strip groove and the distance D1 between two adjacent strip grooves:

[0068] The cross section of the anode electrode is scanned using a CCD device to measure the depth of the strip grooves and the distance between two adjacent strip grooves.

[0069] (2) Cyclic capacity retention test:

[0070] Use the following charging process to charge:

[0071] (1) 2.2C constant current to 4.2V, constant voltage to 1.8C;

[0072] (2) 1.8C constant current to 4.22V, constant voltage to 1.4C;

[0073] (3) 1.4C constant current to 4.24V, constant voltage to 1.1C;

[0074] (4) 1.1C constant current to 4.27V, constant voltage to 0.7C;

[0075] (5) 0.7C constant current to 4.3V, constant voltage to 0.4C;

[0076] (6) 0.4C constant current to 4.5V, constant voltage to 0.025C.

[0077] The above charge-discharge process constitutes one cycle. Record the discharge capacity after the first cycle as the initial discharge capacity. Repeat the above charge-discharge process 1000 times, and record the discharge capacity after 1000 cycles as the final discharge capacity. Capacity retention = final discharge capacity / initial discharge capacity × 100%.

[0078] Lithium deposition test:

[0079] After 1000 cycles of the above charge and discharge process, the battery was disassembled in a fully charged state to obtain the anode electrode. The ratio of the area of ​​the anode electrode where lithium deposition occurred to the area of ​​the entire anode electrode was observed.

[0080] Table 1 lists the parameters and evaluation results of various embodiments and comparative examples.

[0081] Table 1

[0082] Comparing Examples 1-21 and Comparative Examples 1-7, it can be seen that by providing a plurality of strip-shaped grooves in the first region covering the first edge on the active layer, and adjusting the width of the first region to be greater than or equal to 3 mm, the lithium plating problem at the location of the first edge can be significantly improved, and the cycle capacity retention rate can be improved. This is because the strip-shaped grooves reserve space for electrolyte transmission, thereby improving the transmission capacity of the electrolyte at the location of the first edge. In Comparative Example 1, no strip-shaped grooves are provided on the active layer, the lithium plating area is the largest, and the cycle capacity retention rate is the lowest. In Comparative Example 2, the width of the first region is less than 3 mm, which is too small. Although the lithium plating problem and cycle performance can be improved compared to the case where no strip-shaped grooves are provided, the improvement effect is limited.

[0083] Comparing Examples 1-16, it can be seen that when 50μm≤D1≤3000μm, and / or 1μm≤D2≤40μm, the lithium deposition area is small, and the cycle retention rate is high, which significantly improves the cycle performance. In Example 1, D1<50μm, D2<1μm, the depth of the strip grooves is too small, and the effect of improving the cycle performance is limited. In Example 16, D1>300μm, D2>40μm, the spacing between the strip grooves is too large, the number of strip grooves is small, and the effect of improving the cycle performance is limited. In Examples 4-13, 200μm≤D1≤1700μm, and / or 5μm≤D2≤25μm, the lithium deposition area ratio is reduced to below 14%, the cycle capacity retention rate reaches more than 78%, and the effect of improving the cycle performance is better.

[0084] From Examples 10, 17-21, and Comparative Examples 1-6, it can be seen that when 1 ≤ L1 / L2 ≤ 3, the battery with stripe grooves has a slower increase in lithium deposition area and a slower decrease in cycle capacity retention rate as L1 / L2 increases compared to the battery without stripe grooves. Comparing Example 21 and Comparative Example 6, when L1 / L2 > 3, although the cycle performance of the battery with stripe grooves is improved compared to the battery without stripe grooves, the cycle performance of the battery with stripe grooves is still poor, and does not meet the higher cycle performance requirements of secondary batteries.

[0085] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the scope of rights of the present application. Therefore, equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A secondary battery comprising a packaging bag, an electrode assembly, and a tab, wherein the electrode assembly is contained in the packaging bag and includes an anode electrode sheet, the anode electrode sheet including a current collector and an active layer disposed on at least one surface of the current collector, characterized in that: The packaging bag has a first recess, the electrode assembly has a laminate structure, and the electrode assembly further includes a first end face, a first side face, a second side face, a third side face, a second end face, and a fourth side face connected in sequence. The electrode tab protrudes from the first end face along a first direction and extends out of the packaging bag. The first end face and the second end face are arranged opposite to each other in the first direction. The third side face and the fourth side face are arranged opposite to each other in a second direction perpendicular to the first direction. The first side face, the second side face, and the third side face are located on the same side of the electrode assembly in the second direction. The first side face and the second side face are surrounded by a second recess, the second recess is arranged around the first recess, and the shape of the second recess matches the shape of the first recess. In the second direction, the anode electrode includes a first part and a second part arranged in sequence, the first part is connected to the second part and is surrounded to form the second recess, the first part includes a first edge located on the third side, and the second part includes a second edge located on the fourth side; the active layer includes a first area provided with a plurality of strip grooves, the first area covers the first edge and extends toward the second edge, at least one of the strip grooves is located in the first part, and the width of the first area in the second direction is greater than or equal to 3 mm.

2. The secondary battery according to claim 1, wherein In the second direction, a distance between the third side surface and the fourth side surface is L1; in the first direction, a distance between the first end surface and the second end surface is L2, and 1.0≤L1 / L2≤3.

0.

3. The secondary battery according to claim 1, wherein The distance between two adjacent strip-shaped grooves is D1, the depth of the strip-shaped grooves is D2, 50 μm≤D1≤3000 μm; and / or, 1 μm≤D2≤40 μm.

4. The secondary battery according to claim 3, wherein 200 μm≤D1≤1700 μm; and / or, 5 μm≤D2≤25 μm.

5. The secondary battery according to claim 1, wherein The strip-shaped groove is arranged perpendicularly, parallel or obliquely relative to the first edge.

6. The secondary battery according to claim 5, wherein The included angle between the strip-shaped groove and the first edge is θ, 0°<θ<90°.

7. The secondary battery according to claim 1, wherein The electrode tab is integrally arranged with the current collector, the second portion includes a third edge located on the first end surface, the strip-shaped groove includes a first end located on one side of the electrode tab in the first direction, and along the first direction, the minimum distance between the third edge and the first end is 0 to 3 mm.

8. The secondary battery according to any one of claims 1 to 7, wherein: The plurality of strip-shaped grooves are evenly spaced apart and arranged in the first area.

9. The secondary battery according to any one of claims 1 to 7, wherein: The packaging bag includes a first packaging part and a second packaging part that are integrally arranged. The first packaging part and the second packaging part are interconnected to form a main body part for accommodating the electrode assembly and a sealing part for sealing the main body part. The electrode tab extends from the inside of the main body part through the sealing part.

10. The secondary battery according to any one of claims 1 to 7, wherein: The active layer includes an anode active material, and the anode active material includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide, silicon-carbon composite, lithium titanate, and a metal that can form an alloy with lithium.

11. The secondary battery according to any one of claims 1 to 7, wherein: The electrode assembly further includes a cathode electrode sheet and a separator. The anode electrode sheet, the separator and the cathode electrode sheet are stacked in sequence to form the laminate structure. 12 . The secondary battery according to claim 1 , wherein the secondary battery is L-shaped.

13. An electronic device, wherein: The secondary battery comprises the secondary battery according to any one of claims 1 to 12.

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