Secondary batteries and electronic devices

Abstract

The secondary battery, among secondary batteries and electronic devices, includes an electrode assembly and an anode tab, the electrode assembly includes an anode sheet, the anode sheet includes an anode current collector and a first anode active layer provided on at least one surface of the anode current collector, the anode tab is provided integrally with the anode current collector and extends outward from the electrode assembly in a first direction, the first anode active layer includes a first region corresponding to the anode tab in the first direction, the first region is provided with a plurality of strip-like grooves, in the first direction, the anode current collector includes a first edge located on one side of the anode tab, the strip-like grooves include a first end located on one side of the anode tab, and the distance between the first end and the first edge of at least one strip-like groove located in the first region is 0 or greater.

Description

Technical Field

[0001] This application relates to the field of battery technology, and particularly to secondary batteries and electronic devices.

Background Art

[0002] Secondary batteries (such as lithium-ion batteries) have advantages such as high energy density, high output power, and long cycle life, and are thus widely applied in electric vehicles and consumer electronics products. During the use process of lithium-ion batteries, the electrolyte often has difficulty completely penetrating inside the membrane, and concentration changes of electrolyte particles occur inside the electrode, resulting in a concentration polarization phenomenon. The exchange reaction process between the electrode and electrolyte particles is restricted. Especially for batteries with high energy density requirements, this restrictive effect is more obvious because the thicker the membrane, the poorer the penetration ability of the electrolyte. Due to this restricted effect, lithium precipitation problems are likely to occur, affecting cycle performance.

Summary of the Invention

[0003] Through research by the inventors, it has been found that by etching grooves on the active layer, the penetration of the electrolyte into the active layer can be increased, and the cycle performance can be improved. However, when forming grooves by etching, there are limitations in the accuracy of the processing device, and there is a risk of etching up to the tab. On the one hand, the tab is damaged and the strength of the tab is reduced. On the other hand, copper particles are introduced to cause micro-short circuits and exacerbate self-discharge.

[0004] One object of this application is to provide a secondary battery and an electronic device that can reduce the risk of tab damage on the premise of improving cycle performance.

[0005] A first aspect of the present application provides a secondary battery comprising an electrode assembly and an anode tab, the electrode assembly comprising an anode sheet, the anode sheet comprising an anode current collector and a first anode active layer provided on at least one surface of the anode current collector, the anode tab comprising an anode current collector integrally with the anode current collector and extending outward from the electrode assembly in a first direction. The first anode active layer comprises a first region corresponding to the anode tab in a first direction, the first region comprising a plurality of strip-like grooves, the anode current collector comprising a first edge located on one side of the anode tab in a first direction, the strip-like grooves comprising a first end located on one side of the anode tab, and the distance between the first end and the first edge of at least one strip-like groove located in the first region being 0 or greater.

[0006] The secondary battery of this application accelerates electrolyte transport, increases the penetration of electrolyte into the first region, and enhances the electrolyte's storage capacity by providing a strip-like groove in the first region of the first anode active layer, thereby improving cycle performance. Furthermore, by setting the distance between the first end of the strip-like groove in the first region and the first edge of the anode current collector to 0 or more, the anode tab is not etched during the processing of the strip-like groove, reducing the risk of damage to the anode tab during the processing of the strip-like groove. Therefore, the secondary battery of this application improves cycle performance while simultaneously reducing the risk of damage to the anode tab.

[0007] According to some embodiments of this application, the distance between the first end and the first edge of the stripe groove in the first region is 0 to 3 mm, which effectively improves the lithium deposition problem, enhances cycle performance, and reduces the risk of tab damage.

[0008] According to some embodiments of this application, the distance between the first end and the first edge of each groove is 0.2 to 1.5 mm, which results in a better effect in improving cycle performance and reducing the risk of tab damage.

[0009] According to some embodiments of this application, the first anode active layer further includes a second region offset from the anode tab in a first direction, and the stripe grooves are further provided in the second region. Providing the stripe grooves in the second region of the first anode active layer increases the penetration of the electrolyte into the second region, enhances the electrolyte storage capacity, and further improves the cycle performance.

[0010] According to some embodiments of this application, the anode current collector further includes a third and fourth edge portion that are opposite in a second direction perpendicular to the first direction, and the plurality of striped grooves are arranged from the third edge to the fourth edge. The distribution of the plurality of striped grooves throughout the anode current collector in the second direction results in a better improvement in cycle performance.

[0011] According to some embodiments of this application, the anode current collector further includes a second edge opposite the first edge in a first direction, and a striped groove located in the second region is arranged from the first edge to the second edge, and the striped groove penetrates the first anode active layer along the first direction X, thereby rapidly transporting the electrolyte from the first edge to the second edge via the striped groove, improving the electrolyte transport capacity and providing an advantage in improving cycle performance.

[0012] According to some embodiments of this application, the anode sheet further includes a second anode active layer, the second anode active layer covering a portion of the anode tab and being integrally provided with the first anode active layer. The second anode active layer protects the anode tab and further reduces the risk of the anode tab being etched and damaged.

[0013] According to some embodiments of this application, at least one stripe groove located in the first region extends to the second anodic active layer. By providing the second anodic active layer covering the anode tab, the stripe groove located in the first region can extend to the location where the anode tab is present without damaging the anode tab, further reducing the risk of etching the anode tab when machining the stripe groove.

[0014] According to some embodiments of this application, in the first direction, the width of the second anodic active layer is 0.5 to 1.0 mm, which effectively prevents etching of the anodic tab and suppresses an increase in the cost of the anodic active layer.

[0015] According to some embodiments of this application, the strip-like grooves are provided perpendicular or inclined to the first edge.

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

[0017] According to some embodiments of this application, the first ends of a plurality of stripe-like grooves located in a first region are offset from each other in a second direction perpendicular to the first direction.

[0018] According to some embodiments of this application, the electrode assembly further includes a cathode sheet and a separator, and the anode sheet, separator and cathode sheet are stacked in order to form a laminated structure.

[0019] A second aspect of this application provides an electronic device which includes any of the above-mentioned secondary batteries. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic diagram showing a secondary battery provided by one embodiment of this application, observed along a third direction. [Figure 2] This is a schematic diagram showing an electrode assembly provided by one embodiment of the present application, observed along a first direction. [Figure 3] This is a schematic diagram showing an anode sheet provided by one embodiment of this application, observed along a third direction. [Figure 4] This is a schematic diagram showing an anode sheet provided by another embodiment of the present application, observed along a third direction. [Figure 5]A schematic diagram of the anode sheet provided by yet another embodiment of the present application as observed along the third direction. [Figure 6] A schematic diagram of the anode sheet provided by yet another embodiment of the present application as observed along the third direction.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, the technical solutions in the embodiments of the present application will be described clearly and in detail. As is clear, the described embodiments are some embodiments of the present application, not all embodiments. Unless otherwise defined, all technical terms and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only used for the purpose of explaining specific embodiments and are not intended to limit the present application.

[0022] Hereinafter, the embodiments of the present application will be described in detail. However, the present application can be realized in many different forms and should not be construed as being limited to the exemplary embodiments described herein. Instead, by providing these exemplary embodiments, the present application is fully and detailedly conveyed to those skilled in the art.

[0023] Also, for the sake of brevity and clarity, the size or thickness of each component and layer in the drawings can be enlarged. Throughout the text, the same numerical values refer to the same elements. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items. Also, when element A is referred to as being "connected" to element B, or element A is referred to as "connected" to element B, it should be understood that element A can be directly connected to element B, or there may be an intermediate element C, and element A and element B can be indirectly connected to each other.

[0024] Furthermore, the use of "may" when describing the embodiments of the present application means "one or more embodiments of the present application".

[0025] The terminology used in this specification is for the purpose of describing particular embodiments and is not intended to limit the present application. The singular forms used in this specification are intended to include the plural forms as well, unless the context clearly dictates otherwise. Further, the term "comprising" when used in this specification, refers to the presence of the recited features, numerical values, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, numerical values, steps, operations, elements, components, and / or combinations thereof.

[0026] Terms such as first, second, or third can be used in this specification to describe various elements, components, regions, layers, and / or parts, but 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. Thus, a first element, component, region, layer, or part described below may be referred to as a second element, component, region, layer, or part without departing from the teachings of exemplary embodiments.

[0027] Referring to FIG. 1, an embodiment of the present application provides a secondary battery 100, which includes a case 10, an electrode assembly 20, an electrolyte, and electrode terminals 30. The electrode assembly 20 and the electrolyte are housed within the case 10. The electrode terminals 30 are connected to the electrode assembly 20, extend along the first direction X from one side of the case 10, and are connected to external components. In the present application, the first direction X refers to the length direction of the secondary battery 100. In this embodiment, the number of electrode terminals 30 is two, which are a cathode terminal and an anode terminal respectively, and the two electrode terminals 30 are located on the same side of the secondary battery 100.

[0028] When observed 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 it may have an irregular shape such as a T-shape or an L-shape. In this embodiment, when observed 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.

[0029] The case 10 may be a packaging bag obtained by sealing with a sealing film (for example, an aluminum laminate film or a steel laminate film), that is, the secondary battery 100 is a soft pack battery. Specifically, the case 10 includes a main body 11 and a sealing part 12, the main body 11 is provided with a housing cavity for housing the electrode assembly 20, and the sealing part 12 is formed extending from the edge of the main body 11 and is used to seal the main body 11. The electrode terminals 30 extend through the sealing part 12 along the first direction X. In other embodiments, the case 10 is a metal case, for example, a steel case or an aluminum case.

[0030] Referring to Figures 1 and 2, the electrode assembly 20 includes a cathode sheet 21, an anode sheet 22, and a separator 23 positioned between the cathode sheet 21 and the anode sheet 22. The cathode sheet 21, the separator 23, and the anode sheet 22 are stacked sequentially along a third direction Z to form a stacked structure. In other embodiments, the cathode sheet 21, the separator 23, and the anode sheet 22 are stacked along the third direction Z and then wound to form a wound structure.

[0031] The cathode sheet 21 includes a cathode current collector 211 and a cathode active layer 212 provided 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 compositions 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 vanadate phosphate, lithium-rich manganese matrix material, lithium nickel cobalt aluminate, and compositions thereof. In some embodiments, the cathode active layer 212 may further include an adhesive and optionally include a conductive agent. The adhesive can enhance the bonding between active material particles and enhance the bonding between the active material and the current collector. The adhesive includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, etc. The conductive agent can improve the conductivity of the electrode sheet. The conductive agent includes, but is not limited to, graphite, carbon black, acetylene black, metal powder, etc.

[0032] The anode sheet 22 includes an anode current collector 221 and a first anode active layer 222 provided on at least one surface of the anode current collector 221. The anode current collector 221 each includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Al, and compositions thereof. The first anode active layer 222 includes an anode active material, which includes one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide, silicon-carbon composite material, lithium titanate, and metals capable of forming alloys with lithium. In some embodiments, the first anode active layer 222 may further include an adhesive and optionally include a conductive agent. The adhesive can enhance the bonding between active material particles and enhance the bonding between the active material and the current collector. The adhesive includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, etc. Conductive agents can improve the conductivity of electrode sheets. Conductive agents include, but are not limited to, graphite, carbon black, acetylene black, and metal powders.

[0033] The secondary battery 100 further includes a cathode tab 31 and an anode tab 32. The cathode tab 31 is connected to a cathode current collector 211 and extends the electrode assembly 20 along a first direction X so as to be welded to the corresponding electrode terminal 30. The anode tab 32 is connected to an anode current collector 221 and extends the electrode assembly 20 along a first direction X so as to be welded 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.

[0034] 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 to the anode tab 32 in the first direction X. The first region 220 forms a first projection figure on the plane where the anode current collector 221 is located along the third direction Z, and the anode tab 32 forms a second projection figure on the plane where the anode current collector 221 is located along the third direction Z. Along the first direction X, two opposing sides of the first projection figure in the second direction Y and two opposing sides of the second projection figure in the second direction Y are aligned. The second region 230 forms a third projection figure on the plane where the anode current collector 221 is located along the third direction Z, and in the first direction X, the third projection figure and the second projection figure are offset and do not overlap.

[0035] The first region 220 is provided with a plurality of strip-like grooves 22a. The strip-like grooves 22a are formed by removing a portion of the first anode active layer 222. Any known technique can be employed to remove a portion of the first anode active layer 222. In this embodiment, the strip-like grooves 22a are formed by removing a portion of the first anode active layer 222 by a laser etching process. The strip-like grooves 22a provided in the first region 220 accelerate the transport of the electrolyte, increase the penetration of the electrolyte into the first region 220 of the first anode active layer 222, improve the electrolyte infiltration effect, enhance the electrolyte storage capacity, and are advantageous for improving the lithium deposition problem and cycle performance of the first region 220. The anode current collector 221 includes a first edge portion 221a located on one side of the anode tab 32 and a second edge portion 221b opposite to the first edge portion 221a in a first direction X. The striation groove 22a includes a first end 22a1 located on one side of the first edge 221a and a second end 22a2 located on one side of the second edge 221b in the first direction X. In the first direction X, the distance between the first end 22a1 and the first edge 221a of at least one striation groove 22a located in the first region 220 is 0 or greater. If the distance between the first end 22a1 and the first edge 221a is less than 0, for example, if the distance is -1 mm, the striation groove 22a extends to the anode tab 32, damaging the anode tab 32. On the one hand, this reduces the strength of the anode tab 32 and affects the weld strength of the tab. On the other hand, when forming the striation groove 22a extending to the anode tab 32 by etching, metal particles may be introduced onto the anode tab 32, potentially causing a micro-short circuit and increasing self-discharge. Furthermore, if the distance between the first end 22a1 and the first edge 221a is less than 0, it indicates that the strip-like groove 22a extends beyond the first edge 221a along the first direction X, and if the distance between the first end 22a1 and the first edge 221a is 0 or greater, it indicates that the strip-like groove 22a does not extend beyond the first edge 221a along the first direction X.

[0036] The strip-shaped grooves 22a are provided parallel, perpendicular, or inclined to the first edge 221a. Figure 3 shows the case where the strip-shaped grooves 22a are provided perpendicular to the first edge 221a. Figure 4 shows the case where the strip-shaped grooves 22a are provided parallel to the first edge 221a. In some embodiments, multiple strip-shaped grooves 22a are provided parallel to each other, and multiple strip-shaped grooves 22a are provided at uniform intervals in the first region 220.

[0037] As shown in Figure 5, in some embodiments, the first ends 22a1 of a plurality of striped grooves 22a located in the first region 220 are provided substantially aligned in the second direction Y. In this application, "provided substantially aligned" means that the alignment error between the first ends 22a1 is small, for example, the deviation distance of the projection of the first ends 22a1 onto the anode current collector 221 does not exceed 0.5 mm. In some other embodiments, the first ends 22a1 of a plurality of striped grooves 22a located in the first region 220 are provided offset from each other in the second direction Y.

[0038] In some embodiments, the distance between the first end 22a1 and the first edge 221a of the striped groove 22a in the first region 220 is 0 to 3 mm. A larger distance between the first end 22a1 and the first edge 221a reduces the risk of damage to the anode tab 32 when the striped groove 22a is formed by etching, but it may reduce the effectiveness of improving lithium deposition at the first edge 221a of the first region 220. 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 can be effectively improved, cycle performance can be enhanced, and the risk of damage to the anode tab 32 when the striped groove 22a is formed by etching can be reduced.

[0039] In some embodiments, the second end 22a2 of the strip-like groove 22a overlaps with the second edge 221b, which is advantageous in improving the lithium deposition problem at the second edge 221b of the first region 220.

[0040] Referring to Figure 4, the striped grooves 22a are also provided in the second region 230. The striped grooves 22a provided in the second region 230 increase the penetration of the electrolyte from the first anode active layer 222 into the second region 230, improving the electrolyte's immersion effect and enhancing the electrolyte's storage capacity, which is advantageous for improving the lithium deposition problem and cycle performance of the second region 230. In some embodiments, the striped grooves 22a located in the second region 230 are arranged from the first edge 221a to the second edge 221b, that is, the striped grooves 22a located in the second region 230 penetrate the first anode active layer 222 along the first direction X, thereby rapidly transporting the electrolyte from the first edge 221a to the second edge 221b via the striped grooves, improving the electrolyte's transport capacity, which is advantageous for improving the lithium deposition problem and cycle performance of the second region 230.

[0041] The anode current collector 221 further includes a third edge portion 221c and a fourth edge portion 221d that are opposite each other in the second direction Y. In some embodiments, the plurality of striation grooves 22a are arranged from the third edge portion 221c to the fourth edge portion 221d, i.e., the plurality of striation grooves 22a are distributed throughout the anode current collector 221 along the second direction Y. In some embodiments, the plurality of striation grooves 22a are provided uniformly spaced on the anode current collector 221.

[0042] Referring to Figure 6, in some embodiments, the anode sheet 22 further includes a second anode active layer 223, which is integrally provided with the first anode active layer 222. Observed 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-like groove 22a located in the first region 220 extends from the first anode active layer 222 to the second anode active layer 223. By arranging the second anode active layer 223 covering the anode tab 32, the strip-like groove 22a located in the first region 220 does not damage the anode tab 32 even if it extends to the location where the anode tab 32 is located, further reducing the risk of etching the anode tab 32 during processing of the strip-like groove 22a.

[0043] In some embodiments, the width of the second anodic active layer 223 in the first direction X is 0.5 to 1.0 mm. For example, the width of the second anodic active layer 223 is in the range of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, or any two of these numerical compositions.

[0044] One embodiment of this application further provides an electronic device which includes any of the above secondary batteries 100. The electronic device of this application may be, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-reader, a mobile phone, a portable facsimile, a portable copier, a portable printer, a headphone stereo, a video recorder, an LCD television, a portable cleaner, a portable CD player, a MiniDisc player, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric assist bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a strobe, a camera, a large household storage battery, a lithium-ion capacitor, and the like.

[0045] The performance of the secondary battery provided in this application will be explained below through specific examples and comparative examples.

[0046] Example 1

[0047] Cathode Sheet Preparation: Cathode active material (lithium cobalt oxide), conductive agent (conductive carbon black), and adhesive (polyvinylidene fluoride) were dissolved in an N-methylpyrrolidone solution in a weight ratio of 97.5:1:1.5 to form a cathode slurry with a solid content of 75%. Aluminum foil was used as a current collector, and the cathode slurry was applied to the surface of the cathode current collector to obtain a cathode active layer. Subsequently, the anode sheet was obtained by cold pressing and cutting.

[0048] Preparation of the anode sheet: Anode active material (graphite), conductive agent (conductive carbon black), thickener (carboxymethylcellulose sodium), and adhesive (styrene-butadiene rubber) were mixed in a mass ratio of 97.5:1:0.5:1. Deionized water was then added as a solvent, and the mixture was uniformly stirred to obtain an anode slurry with a solid content of 50 wt%. Copper foil was used as a current collector, and the anode slurry was applied to the surface of the anode current collector to obtain the first anode active layer. A laser etching process was used to etch multiple strip-like grooves onto the first anode active layer. These strip-like grooves were distributed throughout the entire first anode active layer and were arranged parallel to the first edge of the anode current collector. Subsequently, the anode sheet was obtained by cold pressing and cutting. The structure of the anode sheet is shown in Figure 4.

[0049] Separator fabrication: A polyethylene membrane was selected as the separator.

[0050] Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), and vinylene carbonate (VC) were mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent. Then, the lithium salt LiPF6, which was thoroughly dried, was mixed with the organic solvent in a weight ratio of 8:92 to obtain the electrolyte.

[0051] Lithium-ion battery fabrication: A cathode sheet, separator, and anode sheet were stacked in order, with the separator positioned between the cathode and anode sheets to obtain an electrode assembly. The electrode assembly was then placed in an aluminum laminate film packaging bag, heat-sealed at a predetermined pressure, injected with electrolyte, and chemically converted to obtain a lithium-ion battery.

[0052] Examples 2-10, Comparative Example 2

[0053] The difference from Example 1 is that the distance between the first end and the first edge of the strip-like groove located in the first region is different. Refer to Table 1 for specific parameters.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that no strip-like grooves are etched onto the first anodic active layer.

[0056] The following describes the testing methods for each parameter of this application.

[0057] Volume retention rate test after cycling:

[0058] The secondary battery was charged in a 25°C environment according to the following charging steps. S1, the secondary battery is charged with a constant current at a charging rate of 1.65C until the secondary battery voltage reaches 4.5V. S2, the secondary battery is charged at a constant voltage of 4.5V until the charge rate reaches 0.025C. S3, Allow the secondary battery to stand for 5 minutes. S4, Discharge the secondary battery at a constant current at a discharge rate of 0.5C until the secondary battery voltage reaches 3.2V. S5. Allow the secondary battery to stand for 5 minutes.

[0059] The above charge-discharge process constitutes one cycle. After the initial charge-discharge is complete, the battery is discharged at a discharge rate of 0.2C until the voltage reaches 3.0V, and the discharged capacity is recorded as the battery's initial capacity. After repeating this 1000 times, the battery is discharged at a discharge rate of 0.2C until the voltage reaches 3.0V, and the discharged capacity is recorded as the battery's recovered capacity. Capacity retention rate = recovered capacity / initial capacity × 100%.

[0060] Lithium deposition test:

[0061] After repeating the above charge-discharge process 1000 times, the battery was disassembled in a fully charged state, and the anode sheet was obtained. The ratio of the area where lithium deposition occurred on the anode sheet to the total area of ​​the anode sheet was observed.

[0062] Anode tab connection strength test:

[0063] In this application, the connection strength between the anode tab and the electrode terminal is expressed by the connection strength between the anode tab and the anode current collector.

[0064] The test procedure was as follows: After discharging the secondary battery to 3.0V, the packaging bag was removed. The electrode assembly was positioned horizontally and secured with a jig. The electrode terminals connected to the anode tab were folded upward, and the electrode terminals were then clamped in a tensile testing machine and pulled vertically upward until the tab broke. The tensile curve was recorded, and the maximum tensile force was set to the tab connection strength.

[0065] Table 1 shows the parameters and evaluation results for each example and comparative example.

[0066] [Table 1]

[0067] Comparing Examples 1-10 with Comparative Examples 1-2, it can be seen that when multiple strip-like grooves are provided on the first anode active layer, and the distance between the first end and the first edge of the strip-like grooves located in the first region is 0 or greater, both high cycle capacity retention and tab connection strength are achieved simultaneously. In Comparative Example 1, since the strip-like grooves are not etched, the tab connection strength is high, but the cycle capacity retention is the worst. In Comparative Example 2, the distance between the first end and the first edge of the strip-like grooves located in the first region is less than 0, the strip-like grooves extend to the anode tab, and the anode tab is etched, resulting in the worst tab connection strength.

[0068] Comparing Examples 1-10, it can be seen that when the distance between the first end of the striped groove in the first region and the first edge of the anode current collector is 0-3 mm, the lithium deposition area ratio is reduced to 1% or less, indicating good lithium deposition improvement ability and high tab connection strength. In Examples 9-10, the distance between the first end of the striped groove in the first region and the first edge of the anode current collector is greater than 3 mm, and the tab is not thermally damaged when forming the striped groove by laser etching, and the tab connection strength is almost the same as that of a battery without striped grooves. However, because the effect of the striped groove on increasing electrolyte transport capacity is limited, the lithium deposition area increases, the lithium deposition improvement effect is reduced, and the cycle capacity retention rate becomes smaller. In Examples 4-6, the distance between the first end of the striped groove in the first region and the first edge of the anode current collector is 0.2-1.5 mm, and lithium deposition does not occur, and the tab connection strength is high.

[0069] The above disclosures represent only preferred embodiments of the present application and, naturally, do not limit the scope of the rights of the present application; therefore, equivalent modifications based on the claims of the present application are still included within the scope of protection of the present application. [Explanation of Symbols]

[0070] 100 Secondary battery 10 cases 20 Electrode Assembly 30 electrode terminal 31 Cathode Tab 32 Anode Tabs 21 Cathode Sheet 22 Anode Sheet 23 Separator 211 Cathode current collector 212 Cathode active layer 221 Anode current collector 222 1st anode active layer 220 1st area 230 Second area 22a Striped grooves 221a 1st edge 221b 2nd edge 221c 3rd edge 221d Part 4 22a1 First end 22a2 End 2 223 Second Anode Active Layer X, first direction Y 2nd direction Z, direction 3

Claims

1. Includes electrode assembly and anode tab, The electrode assembly includes an anode sheet, the anode sheet includes an anode current collector and a first anode active layer provided on at least one surface of the anode current collector. The anode tab is integrally provided with the anode current collector and extends outward from the electrode assembly in a first direction in a secondary battery, 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-like 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. A secondary battery characterized in that the distance between the first end and the first edge of at least one of the strip-shaped grooves located in the first region is 0 or more.

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

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

4. The first anode active layer further includes a second region offset from the anode tab in the first direction, The secondary battery according to any one of claims 1 to 3, characterized in that the aforementioned strip-shaped grooves are further provided in the second region.

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

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

7. The anode sheet further comprises a second anode active layer, The secondary battery according to any one of claims 1 to 6, characterized in that the second anode active layer covers a portion of the anode tab and is provided integrally with the first anode active layer.

8. The secondary battery according to claim 7, characterized in that at least one strip-like groove located in the first region extends to the second anode active layer.

9. The secondary battery according to claim 7, characterized in that, in the first direction, the width of the second anode active layer is 0.5 to 1.0 mm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that the strip-shaped grooves are provided perpendicular or inclined with respect to the first edge.

11. The secondary battery according to claim 10, characterized in that 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, characterized in that the first ends of the plurality of strip-shaped grooves located in the first region are offset from each other in a second direction perpendicular to the first direction.

13. The secondary battery according to any one of claims 1 to 12, wherein the electrode assembly further includes a cathode sheet and a separator, and the anode sheet, the separator, and the cathode sheet are stacked in order to form a stacked structure.

14. The anode current collector further includes a second edge portion provided opposite the first edge portion in the first direction, The aforementioned groove-like structure further includes a second end located on one side of the second edge in the first direction, The secondary battery according to any one of claims 1 to 13, characterized in that the second end overlaps with the second edge.

15. An electronic device characterized by including a secondary battery as described in any one of claims 1 to 14.

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