Secondary battery and electronic device

Abstract

A secondary battery and an electronic device. The secondary battery comprises an electrode assembly and an anode tab; the electrode assembly comprises an anode sheet; the anode sheet comprises an anode current collector and a first anode active layer arranged on at least one surface of the anode current collector; and the anode tab is integrally arranged with the anode current collector and extends out of the electrode assembly in a first direction. The first anode active layer comprises a first region corresponding to the anode tab in the first direction, and a plurality of strip-shaped grooves are formed in the first region; in the first direction, the anode current collector comprises a first edge located on the anode tab side, each strip-shaped groove comprises a first end located on the anode tab side, and the distance between a first end of at least one strip-shaped groove located in the first region and the first edge is greater than or equal to 0.

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] Secondary batteries (such as lithium-ion 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. During the use of lithium-ion batteries, the electrolyte often has difficulty completely penetrating the membrane, causing the concentration of electrolyte particles to fluctuate within the electrode, leading to concentration polarization. This limits the exchange reaction between the electrode and the electrolyte particles. This limitation is particularly pronounced for batteries with higher energy density requirements because the thicker the membrane, the poorer the electrolyte permeability. This limitation can easily lead to lithium precipitation, affecting cycle performance. Summary of the Invention

[0003] The inventors discovered that etching grooves into the active layer can enhance electrolyte penetration and improve cycling performance. However, due to the precision of processing equipment, there is a risk of etching into the tabs. This can damage the tabs, reducing their strength, and introduce copper particles, causing micro-shorts and exacerbating self-discharge.

[0004] One purpose of the present application is to provide a secondary battery and an electronic device that can reduce the risk of tab damage while improving cycle performance.

[0005] In a first aspect, the present application provides a secondary battery comprising an electrode assembly and an anode tab. The electrode assembly includes an anode plate, the anode plate includes an anode current collector and a first anode active layer disposed on at least one surface of the anode current collector. The anode tab and the anode current collector are integrally disposed and extend outside the electrode assembly along a first direction. The first anode active layer includes a first region corresponding to the anode tab in the first direction, the first region being provided with a plurality of strip-shaped grooves. In the first direction, the anode current collector includes a first edge located on one side of the anode tab, the strip-shaped groove includes a first end located on one side of the anode tab, and the distance between the first end of at least one strip-shaped groove located in the first region and the first edge is greater than or equal to zero.

[0006] The secondary battery of the present application is provided with a strip groove in the first region of the first anode active layer, which can accelerate the transmission of the electrolyte, is conducive to increasing the penetration of the electrolyte inside the first region, and at the same time increases the storage capacity of the electrolyte, which is conducive to improving the cycle performance. In addition, the distance between the first end of the strip groove in the first region and the first edge of the anode current collector is greater than or equal to 0, and the anode ear is not etched when the strip groove is formed, reducing the risk of the anode ear being damaged during the processing of the strip groove. Therefore, the secondary battery of the present application reduces the risk of the anode ear being damaged while improving the cycle performance.

[0007] According to some embodiments of the present application, the distance between the first end of the strip-shaped groove in the first region and the first edge is 0 to 3 mm. This can effectively improve the lithium plating problem and enhance the cycle performance while reducing the risk of damage to the tab.

[0008] According to some embodiments of the present application, the distance between the first end and the first edge of each strip-shaped groove is 0.2 to 1.5 mm, which can better improve the cycle performance and reduce the damage to the tab.

[0009] According to some embodiments of the present application, the first anode active layer further includes a second region offset from the anode tab in the first direction, and the strip-shaped groove is further provided in the second region. Providing the strip-shaped groove in the second region of the first anode active layer facilitates increased electrolyte penetration within the second region, while also increasing electrolyte storage capacity, further improving cycling performance.

[0010] According to some embodiments of the present application, the anode current collector further includes a third edge and a fourth edge that are opposite each other in a second direction perpendicular to the first direction, and the plurality of strip-shaped grooves are arranged from the third edge to the fourth edge. The plurality of strip-shaped grooves are distributed throughout the anode current collector in the second direction, thereby further improving the cycling performance.

[0011] According to some embodiments of the present application, the anode current collector also includes a second edge opposite to the first edge in the first direction, and the strip groove located in the second area is configured from the first edge to the second edge, so that the strip groove passes through the first anode active layer along the first direction X, so that the electrolyte is quickly transferred from the first edge to the second edge through the strip groove, thereby improving the transmission capacity of the electrolyte and further improving the cycle performance.

[0012] According to some embodiments of the present application, the anode electrode plate further includes a second anode active layer, which covers a portion of the anode tab and is integrally formed with the first anode active layer. The second anode active layer protects the anode tab, further reducing the risk of etching damage to the anode tab.

[0013] According to some embodiments of the present application, at least one strip-shaped groove located in the first region extends to the second anode active layer. By configuring the second anode active layer to cover the anode tab, the anode tab will not be damaged even if the strip-shaped groove located in the first region extends to the location of the anode tab, further reducing the risk of etching the anode tab when machining the strip-shaped groove.

[0014] According to some embodiments of the present application, in the first direction, the width of the second anode active layer is 0.5 to 1.0 mm, which can effectively protect the anode tab from being etched and control the increase in the cost of the anode active layer.

[0015] According to some embodiments of the present application, the strip-shaped groove is arranged perpendicularly or obliquely relative to the first edge.

[0016] According to some embodiments of the present application, first ends of the plurality of strip-shaped grooves located in the first region are substantially aligned in a second direction perpendicular to the first direction.

[0017] According to some embodiments of the present application, first ends of the plurality of strip-shaped grooves located in the first region are staggered in a second direction perpendicular to the first direction.

[0018] 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.

[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 an electrode assembly provided in one embodiment of the present application observed along a first direction.

[0022] FIG3 is a schematic diagram of an anode electrode provided by one embodiment of the present application observed along a third direction.

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

[0024] FIG5 is a schematic diagram of an anode electrode provided in another embodiment of the present application observed along a third direction.

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

[0026] Description of Main Component Symbols Secondary Battery 100 Housing 10 Electrode Assembly 20 Electrode Terminal 30 Cathode Tab 31 Anode Tab 32 Cathode Plate 21 Anode Plate 22 Separator 23 Cathode Current Collector 211 Cathode Active Layer 212 Anode Current Collector 221 First Anode Active Layer 222 First Region 220 Second Region 230 Strip-Shaped Groove 22a First Edge 221a Second Edge 221b Third Edge 221c Fourth Edge 221d First End 22a1 Second End 22a2 Second Anode Active Layer 223 First Direction X Second Direction Y Third Direction Z

[0027] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0032] 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.

[0033] 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.

[0034] Referring to Figure 1, an embodiment of the present application provides a secondary battery 100, comprising a housing 10, an electrode assembly 20, an electrolyte, and an electrode terminal 30. The electrode assembly 20 and the electrolyte are housed in the housing 10. The electrode terminal 30 is connected to the electrode assembly 20 and extends from one side of the housing 10 along a first direction X to connect to external components. In this application, the first direction X refers to the longitudinal direction of the secondary battery 100. In this embodiment, there are two electrode terminals 30, namely a cathode terminal and an anode terminal, and the two electrode terminals 30 are located on the same side of the secondary battery 100.

[0035] When viewed along a third direction Z perpendicular to the first direction X, the secondary battery 100 may have a regular shape, such as a rectangle or a circle, or an irregular shape, such as a T-shape or an L-shape. In this embodiment, when viewed along the third direction Z, the secondary battery 100 is rectangular. In this application, the third direction Z refers to the thickness direction of the secondary battery 100.

[0036] The housing 10 can be a packaging bag encapsulated with an encapsulating film (such as an aluminum-plastic film or a steel-plastic film), that is, the secondary battery 100 is a soft-pack battery. Specifically, the housing 10 includes a main body 11 and an encapsulating portion 12. The main body 11 is provided with a cavity for accommodating the electrode assembly 20. The encapsulating portion 12 extends from the edge of the main body 11 and is used to seal the main body 11. The electrode terminal 30 extends through the encapsulating portion 12 along the first direction X. In other embodiments, the housing 10 is a metal housing, such as a steel shell or an aluminum shell.

[0037] 1 and 2 , 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 laminated structure. In other embodiments, the cathode electrode sheet 21, the separator 23, and the anode electrode sheet 22 are stacked along the third direction Z and then wound to form a wound structure.

[0038] 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. 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 cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, and combinations thereof. In some embodiments, the cathode active layer 212 also includes a binder and, optionally, a conductive agent. The binder can improve the bonding between the active material particles and between the active material and the current collector. Examples of binders include, but are not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, and the like. The conductive agent can improve the conductivity of the electrode. Examples of conductive agents include, but are not limited to, graphite, carbon black, acetyl black, and metal powders.

[0039] The anode electrode 22 includes an anode current collector 221 and a first anode active layer 222 disposed on at least one surface of the anode current collector 221. The anode current collector 221 includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and combinations thereof. The first anode active layer 222 includes an anode active material, which may include 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. In some embodiments, the first anode active layer 222 also includes a binder and, optionally, a conductive agent. The binder can improve the bonding between the active material particles and between the active material and the current collector. Examples of binders include, but are not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, and polyvinyl fluoride. The conductive agent can improve the conductivity of the electrode. Examples of conductive agents include, but are not limited to, graphite, carbon black, acetylene black, and metal powders.

[0040] The secondary battery 100 further includes a cathode tab 31 and an anode tab 32. The cathode tab 31 is connected to the cathode current collector 211 and extends out of the electrode assembly 20 in the first direction X for welding to the corresponding electrode terminal 30. The anode tab 32 is connected to the anode current collector 221 and extends out of the electrode assembly 20 in the first direction X for welding to the corresponding electrode terminal 30. In this embodiment, the cathode tab 31 is integrally provided with the cathode current collector 211, and the anode tab 32 is integrally provided with the anode current collector 221.

[0041] Referring to Figure 3 , the first anode active layer 222 includes a first region 220 corresponding to the anode tab 32 in the first direction X, and a second region 230 offset from the anode tab 32 in the first direction X. The first region 220 forms a first projected pattern along the third direction Z on the plane of the anode current collector 221, while the anode tab 32 forms a second projected pattern along the third direction Z on the plane of the anode current collector 221. Along the first direction X, two opposing sides of the first projected pattern in the second direction Y are aligned with two opposing sides of the second projected pattern in the second direction Y. The second region 230 forms a third projected pattern along the third direction Z on the plane of the anode current collector 221. The third and second projected patterns are offset and do not overlap in the first direction X.

[0042] The first region 220 is provided with a plurality of strip-shaped grooves 22a. The strip-shaped grooves 22a are formed by removing a portion of the first anode active layer 222. Any conventional technique can be used to remove a portion of the first anode active layer 222. In this embodiment, the strip-shaped grooves 22a are formed by removing a portion of the first anode active layer 222 through a laser etching process. The strip-shaped grooves 22a provided in the first region 220 can accelerate the transmission of the electrolyte, thereby increasing the penetration of the electrolyte into the first region 220 of the first anode active layer 222, improving the electrolyte infiltration effect, and increasing the electrolyte storage capacity, thereby improving the lithium deposition problem in the first region 220 and improving the cycle performance. The anode current collector 221 includes a first edge 221a located on one side of the anode tab 32 and a second edge 221b opposite the first edge 221a in the first direction X. The strip-shaped grooves 22a include a first end 22a1 located on one side of the first edge 221a in the first direction X and a second end 22a2 located on one side of the second edge 221b. In the first direction X, the distance between the first end 22a1 of at least one strip-shaped groove 22a located in the first region 220 and the first edge 221a is greater than or equal to zero. When the distance between the first end 22a1 and the first edge 221a is less than zero, such as -1 mm, the strip-shaped groove 22a extends to the anode tab 32, damaging the anode tab 32. This reduces the strength of the anode tab 32 and affects the tab's welding tension. Furthermore, when etching the strip-shaped groove 22a extending to the anode tab 32, metal particles are introduced into the anode tab 32, potentially causing micro-shorts and exacerbating self-discharge. It should be noted that when the distance between the first end 22a1 and the first edge 221a is less than zero, it indicates that the strip-shaped groove 22a extends beyond the first edge 221a along the first direction X. When the distance between the first end 22a1 and the first edge 221a is greater than or equal to zero, it indicates that the strip-shaped groove 22a does not extend beyond the first edge 221a along the first direction X.

[0043] The strip groove 22a is arranged parallel to, perpendicular to, or obliquely relative to the first edge 221a. FIG3 illustrates a case where the strip groove 22a is arranged perpendicular to the first edge 221a. FIG4 illustrates a case where the strip groove 22a is arranged parallel to the first edge 221a. In some embodiments, multiple strip grooves 22a are arranged parallel to each other, and the multiple strip grooves 22a are evenly spaced in the first region 220.

[0044] As shown in FIG5 , in some embodiments, the first ends 22a1 of the plurality of strip-shaped grooves 22a located in the first region 220 are substantially aligned in the second direction Y. In this application, "substantially aligned" is intended to indicate that the deviation between the first ends 22a1 is relatively low, such as when the projection of the first end 22a1 on the anode current collector 221 deviates by no more than 0.5 mm. In other embodiments, the first ends 22a1 of the plurality of strip-shaped grooves 22a located in the first region 220 are staggered in the second direction Y.

[0045] In some embodiments, the distance between the first end 22a1 of the strip-shaped groove 22a of the first region 220 and the first edge 221a is 0 to 3 mm. When the distance between the first end 22a1 and the first edge 221a is larger, the risk of damage to the anode tab 32 when etching to form the strip-shaped groove 22a is reduced, but the effect of improving lithium deposition at the first edge 221a of the first region 220 may be worse. When the distance between the first end 22a1 and the first edge 221a is within the above range, the lithium deposition problem at the first edge 221a is effectively improved, the cycle performance is improved, and the risk of damage to the anode tab 32 when etching to form the strip-shaped groove 22a is reduced.

[0046] In some embodiments, the second end 22a2 of the strip-shaped groove 22a overlaps with the second edge 221b, which helps to improve the lithium deposition problem at the second edge 221b of the first region 220.

[0047] Please refer to Figure 4, the strip groove 22a is also provided in the second area 230. The strip groove 22a provided in the second area 230 is conducive to increasing the penetration of the electrolyte into the second area 230 of the first anode active layer 222, improving the electrolyte infiltration effect, and at the same time increasing the storage capacity of the electrolyte, which is conducive to improving the lithium plating problem in the second area 230 and improving the cycle performance. In some embodiments, the strip groove 22a located in the second area 230 is configured from the first edge 221a to the second edge 221b, that is, the strip groove 22a located in the second area 230 passes through the first anode active layer 222 along the first direction X. In this way, the electrolyte is quickly transferred from the first edge 221a to the second edge 221b through the strip groove, thereby improving the transmission capacity of the electrolyte, and is more conducive to improving the lithium plating problem in the second area 230 and improving the cycle performance.

[0048] The anode current collector 221 further includes a third edge 221c and a fourth edge 221d that are opposite to each other in the second direction Y. In some embodiments, the plurality of strip-shaped grooves 22a are arranged from the third edge 221c to the fourth edge 221d, that is, the plurality of strip-shaped grooves 22a are distributed throughout the anode current collector 221 along the second direction Y. In some embodiments, the plurality of strip-shaped grooves 22a are evenly spaced apart on the anode current collector 221.

[0049] Referring to FIG. 6 , in some embodiments, the anode electrode sheet 22 further includes a second anode active layer 223, which is integrally formed with the first anode active layer 222. Viewed along the third direction Z, the second anode active layer 223 covers a portion of the anode tab 32 and is located outside the anode current collector 221. At least one strip-shaped groove 22a located in the first region 220 extends from the first anode active layer 222 to the second anode active layer 223. By configuring the second anode active layer 223 to cover the anode tab 32, even if the strip-shaped groove 22a located in the first region 220 extends to the location of the anode tab 32, the anode tab 32 will not be damaged, further reducing the risk of etching the anode tab 32 when processing the strip-shaped groove 22a.

[0050] In some embodiments, the width of the second anode active layer 223 is 0.5-1.0 mm in the first direction X. For example, the width of the second anode active layer 223 is 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, or a range consisting of any two of these values.

[0051] One embodiment of the present application further provides an electronic device comprising any of the above-described secondary batteries 100. 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, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0052] The performance of the secondary battery provided in this application is described below through specific examples and comparative examples.

[0053] Example 1

[0054] 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.

[0055] 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 a first anode active layer. A laser etching process is used to etch a plurality of strip grooves on the first anode active layer. The plurality of strip grooves are distributed throughout the first anode active layer, and the strip grooves are arranged parallel to the first edge of the anode current collector. Subsequently, the anode electrode is obtained by cold pressing and cutting. The structure of the anode electrode is shown in Figure 4.

[0056] Preparation of diaphragm: Polyethylene film is selected as the diaphragm.

[0057] 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.

[0058] Preparation of lithium-ion batteries: The cathode electrode, 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.

[0059] Examples 2-10, Comparative Example 2

[0060] The difference from Example 1 is that the distance between the first end of the strip-shaped groove in the first region and the first edge is different. Specific parameters are shown in Table 1.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that no strip-shaped grooves are etched on the first anode active layer.

[0063] The test methods for various parameters of this application are described below.

[0064] Capacity retention test after cycling:

[0065] At 25°C, charge the secondary battery according to the following charging steps:

[0066] S1. Charge the secondary battery with a constant current at a charge rate of 1.65C until the voltage of the secondary battery reaches 4.5V;

[0067] S2, constant voltage charging the secondary battery at a charging voltage of 4.5V until the charging rate reaches 0.025C;

[0068] S3. Let the secondary battery stand for 5 minutes;

[0069] S4, discharging the secondary battery at a constant current at a discharge rate of 0.5C until the voltage of the secondary battery reaches 3.2V;

[0070] S5. Let the secondary battery stand for 5 minutes.

[0071] The above charge and discharge process is considered one cycle. After the initial charge and discharge cycle, perform cross-current discharge at a discharge rate of 0.2C until the voltage reaches 3.0V. Record the discharge capacity as the battery's initial capacity. Repeat 1000 cycles, then perform cross-current discharge at a discharge rate of 0.2C until the voltage reaches 3.0V. Record the discharge capacity as the battery's recovered capacity. Capacity retention = recovered capacity / initial capacity × 100%.

[0072] Lithium deposition test:

[0073] 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.

[0074] Anode tab connection strength test:

[0075] In the present application, the connection strength between the anode tab and the anode current collector is characterized by the connection strength between the anode tab and the electrode terminal.

[0076] The test procedure is as follows: Discharge the secondary battery to 3.0V, then remove the packaging bag. Lay the electrode assembly horizontally and secure it with a clamp. Fold the electrode terminal connected to the anode tab upward. Then, use a tensile testing machine to clamp the electrode terminal and pull it vertically upward until the tab breaks. Record the tensile force curve, and use the maximum tensile force as the tab connection strength.

[0077] Table 1 lists the parameters and evaluation results of various embodiments and comparative examples.

[0078] Table 1

[0079] Comparing Examples 1-10 and Comparative Examples 1-2, it can be seen that when multiple strip-shaped grooves are provided on the first anode active layer, and the distance between the first end and the first edge of the strip-shaped groove located in the first region is greater than or equal to 0, both the cycle capacity retention rate and the tab connection strength are high. In Comparative Example 1, no strip-shaped grooves are etched, and although the tab connection strength is high, the cycle capacity retention rate is the worst. In Comparative Example 2, the distance between the first end and the first edge of the strip-shaped groove located in the first region is less than 0, and the strip-shaped groove extends to the anode tab, causing the anode tab to be etched, resulting in the worst tab connection strength.

[0080] Comparing Examples 1-10, it can be seen that when the distance between the first end of the strip groove in the first region and the first edge of the anode current collector is 0-3 mm, the lithium deposition area accounts for less than 1%, the ability to improve lithium deposition is good, and the tab connection strength is relatively large. In Examples 9-10, the distance between the first end of the strip groove in the first region and the first edge of the anode current collector is greater than 3 mm. Although the laser etching does not cause thermal damage to the tab, making the tab connection strength roughly the same as the tab strength of the battery without the strip groove, the strip groove has a limited effect on increasing the electrolyte transmission capacity, resulting in an increase in the lithium deposition area, a decrease in the effect of improving lithium deposition, and a low cycle capacity retention rate. In Examples 4-6, the distance between the first end of the strip groove in the first region and the first edge of the anode current collector is 0.2-1.5 mm, no lithium deposition occurs, and the tab connection strength is relatively large.

[0081] 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 an electrode assembly and an anode tab, wherein the electrode assembly comprises an anode electrode sheet, the anode electrode sheet comprises an anode current collector and a first anode active layer disposed on at least one surface of the anode current collector, the anode tab being integrally disposed with the anode current collector and extending out of the electrode assembly along a first direction, wherein: The first anode active layer includes a first region corresponding to the anode tab in the first direction, and the first region is provided with a plurality of strip-shaped grooves; in the first direction, the anode current collector includes a first edge located on one side of the anode tab, and the strip-shaped groove includes a first end located on one side of the anode tab, and a distance between the first end and the first edge of at least one of the strip-shaped grooves located in the first region is greater than or equal to 0.

2. The secondary battery according to claim 1, wherein The distance between the first end of the strip-shaped groove located in the first area and the first edge is 0 to 3 mm.

3. The secondary battery according to claim 2, wherein The distance between the first end of the strip-shaped groove located in the first area and the first edge is 0.2-1.5 mm.

4. The secondary battery according to any one of claims 1 to 3, wherein: The first anode active layer further includes a second region staggered from the anode tab in the first direction, and the strip-shaped groove is also provided in the second region.

5. The secondary battery according to claim 4, wherein The anode current collector further includes a third edge and a fourth edge opposite to each other in a second direction perpendicular to the first direction, and the plurality of strip-shaped grooves are arranged from the third edge to the fourth edge.

6. The secondary battery according to claim 4, wherein The anode current collector further includes a second edge opposite to the first edge in the first direction, and the strip-shaped groove located in the second region is arranged from the first edge to the second edge.

7. The secondary battery according to any one of claims 1 to 6, wherein: The anode electrode plate further includes a second anode active layer, which covers a portion of the anode tab and is integrally provided with the first anode active layer.

8. The secondary battery according to claim 7, wherein At least one strip-shaped groove located in the first region extends to the second anode active layer.

9. The secondary battery according to claim 7, wherein In the first direction, the width of the second anode active layer is 0.5-1.0 mm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The strip-shaped groove is arranged perpendicularly or obliquely relative to the first edge.

11. The secondary battery according to claim 10, wherein The first ends of the plurality of strip-shaped grooves located in the first region are substantially aligned in a second direction perpendicular to the first direction.

12. The secondary battery according to claim 10, wherein The first ends of the plurality of strip-shaped grooves located in the first region are staggered in a second direction perpendicular to the first direction.

13. The secondary battery according to any one of claims 1 to 12, characterized in that: 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 a laminate structure.

14. The secondary battery according to any one of claims 1 to 13, characterized in that: The anode current collector further includes a second edge disposed opposite to the first edge in the first direction; the strip-shaped groove further includes a second end located on one side of the second edge in the first direction; and the second end overlaps with the second edge.

15. An electronic device, wherein: The invention comprises the secondary battery according to any one of claims 1 to 14.

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