Secondary battery, preparation method thereof and electronic device

Abstract

A secondary battery, a method of manufacturing the same, and an electronic device, the secondary battery including an electrode assembly including a wound pole piece. The pole piece comprises a current collector and a plurality of tabs, and the tabs and the current collector are integrally arranged. The current collector comprises a first edge in a first direction, the first edge and the plurality of tabs are positioned on the same side, and the first direction is the width direction of the pole piece. At least part of the tabs comprise a first part and a second part which are sequentially connected along the extension direction of the tabs, the upper edge of the first part in the first direction is flush with the first edge and is connected with the second part, and the lower edge of the first part in the first direction is connected with the current collector. The first part is bent relative to the current collector, and the second part protrudes out of the first edge in the first direction. And in the winding direction of the pole piece, the first part is in contact with the current collectors on the two sides of the first part. The first edge is provided with a plurality of gaps, and the plurality of gaps and the plurality of tabs are alternately arranged at intervals along the winding direction of the pole piece.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a secondary battery, a preparation method thereof, and an electronic device. Background Art

[0002] Lithium-ion batteries have been widely used in mobile and portable electrical appliances due to their advantages such as high energy density, high average open-circuit voltage, and long cycle life. With the development of electronic products towards miniaturization and multi-functionality, the requirement for the energy density of lithium-ion batteries is also getting higher and higher, which requires the battery to contribute more capacity in the same space. The electrode tab of the battery is connected to the external circuit through the electrode ear. The electrode ear protrudes from the edge of the electrode tab, and there is a space between the top of the electrode ear and the edge of the electrode tab, which cannot be effectively utilized and is not conducive to improving the energy density of the battery. Summary of the Invention

[0003] An object of the present application is to provide a secondary battery, a preparation method thereof, and an electronic device that can improve the energy density.

[0004] In a first aspect of the present application, a secondary battery is provided, including an electrode assembly, and the electrode assembly includes wound electrode tabs. The electrode tab includes a current collector and a plurality of electrode ears, and the plurality of electrode ears are integrally provided with the current collector. The current collector includes a first edge in a first direction, and the first edge and the plurality of electrode ears are on the same side in the first direction, and the first direction is the width direction of the electrode tab. At least some of the plurality of electrode ears include a first portion and a second portion connected in sequence along the extending direction of the electrode ear. The first portion includes an upper edge and a lower edge oppositely arranged along the extending direction of the electrode ear. The upper edge is flush with the first edge in the first direction, and the upper edge is connected to the second portion. The lower edge is connected to the current collector. The first portion is bent relative to the current collector, and the second portion protrudes from the first edge in the first direction. In the winding direction of the electrode tab, the first portion is in contact with the current collectors on both sides of the first portion. The first edge is provided with a plurality of notches, and the plurality of notches and the plurality of electrode ears are alternately arranged at intervals along the winding direction of the electrode tab.

[0005] In the present application, by configuring the first portion with the upper edge flush with the first edge of the current collector and in contact with the current collectors on both sides of the first portion, without changing the volume, the length of the current collector that can be coated with the active material can be increased in the first direction, thereby increasing the coating amount of the active material, which is beneficial to improving the volume energy density of the secondary battery.

[0006] Based on the first aspect, in some embodiments, the electrode tab includes a positive electrode tab and a negative electrode tab. Along the second direction, multiple tabs of the positive electrode tab are stacked to form a positive tab group, and multiple notches of the positive electrode tab are stacked to form a first notch group. Along the second direction, multiple tabs of the negative electrode tab are stacked to form a negative tab group, and multiple notches of the negative electrode tab are stacked to form a second notch group. Part of the positive tab group is received in the second notch group, and part of the negative tab group is received in the first notch group. The second direction is the thickness direction of the electrode assembly, and the first direction and the second direction are perpendicular to each other. In this way, the length of the part of the tab group protruding from the edge of the current collector can be reduced, thereby improving the volumetric energy density of the secondary battery.

[0007] Based on the first aspect, in some embodiments, the secondary battery includes a first insulating member disposed on one side of the tab group. The first insulating member includes a first portion, and in the first direction, the first portion is disposed between the tab group and the current collector. The first portion is used to isolate the tab group and the current collector, reducing the risk of short circuit due to contact between the tab group and the current collector, thereby improving the safety performance of the secondary battery; and configuring the first portion can further reduce the distance between the tab group and the current collector, which is beneficial to improving the volumetric energy density of the secondary battery.

[0008] Based on the first aspect, in some embodiments, the first insulating member further includes a second portion. The tab group and the electrode terminal are connected by welding, and the second portion covers the connection between the tab group and the electrode terminal, so as to reduce the risk of short circuit caused by welding burrs.

[0009] Based on the first aspect, in some embodiments, the multiple notches include a first notch, and the depth of the first notch in the first direction is H 1 ; when the first portion is flattened in the first direction, the height of the part of the tab protruding from the first edge is H 2 ; 0.95 ≤ H 1 / H 2 ≤ 1.05. When H 1 / H 2 is within the above range, when preparing the electrode tab, the first notch and the positive tab can be formed in cooperation, simplifying the manufacturing process.

[0010] Based on the first aspect, in some embodiments, 2 mm ≤ H 1 ≤ 11 mm. When H 1 is within the above range, the secondary battery has a suitable volumetric energy density.

[0011] Based on the first aspect, in some embodiments, the secondary battery further includes a second insulating member. The second insulating member is disposed on at least one side of the positive tab group and covers at least part of the first portion. The second insulating member is used to isolate the positive tab and the negative electrode tab, reducing the risk of short circuit due to contact between the positive tab and the negative electrode tab.

[0012] Based on the first aspect, in some embodiments, the second insulating member includes a first region covering the positive electrode active material layer. Along the winding direction of the positive electrode tab, the width range of the first region is from 1 mm to 2 mm. When the width of the first region is within the above range, the risk of contact short circuit between the positive electrode tab and the negative electrode tab can be effectively reduced, and the second insulating member has a relatively small impact on the energy density.

[0013] Based on the first aspect, in some embodiments, along the first direction, the length range of the second insulating member is from 1.5 mm to 3 mm. When the length of the second insulating member is within the above range, the risk of contact short circuit between the positive electrode tab and the negative electrode tab can be effectively reduced, and the second insulating member has a relatively small impact on the energy density.

[0014] The second aspect of the present application provides a method for manufacturing any of the above secondary batteries, including: Providing a first current collector, the first current collector includes a first surface and a second surface oppositely arranged along the thickness direction of the first current collector. Continuously coating an active material on the first surface and drying and cold pressing to form a first active material layer, and continuously coating an active material on the second surface and drying and cold pressing to form a second active material layer; Along the length direction of the first current collector, removing a part of the active material at regular intervals to expose the first current collector, forming a plurality of first empty foil regions, and the plurality of first empty foil regions are located in the middle of the first current collector in the first direction; Cutting the first current collector along the length direction of the first current collector and the edges of the plurality of first empty foil regions, wherein the edges of the first empty foil regions in the length direction of the first current collector are disconnected from the first current collector, and after cutting, two electrode tabs are formed opposite to each other in the first direction, and the two electrode tabs include a first electrode tab and a second electrode tab; The edges of the first electrode tab and the second electrode tab both include a plurality of protrusions and a plurality of notches alternately arranged at intervals along the length direction of the electrode tab. Along the first direction, the plurality of protrusions on the first electrode tab correspond to the plurality of notches on the second electrode tab, and the plurality of notches on the first electrode tab correspond to the plurality of protrusions on the second electrode tab, wherein the plurality of protrusions are configured as a plurality of electrode tabs.

[0015] Based on the second aspect, in some embodiments, the distance between two adjacent ones of the plurality of first empty foil regions is W 1 , along the length direction of the first current collector, W 1 Increases in sequence.

[0016] Based on the second aspect, in some embodiments, along the first direction, the length range of the first empty foil region is from 9 mm to 13 mm.

[0017] Based on the second aspect, in some embodiments, the method for removing a part of the active material includes any one of the following: (1)Before coating the active material, adhesive parts are pasted at multiple positions of the first empty foil areas, and after coating the active material, the adhesive parts are torn off to remove part of the active material, thereby forming multiple first empty foil areas; (2)After coating the active material, part of the active material is removed by laser etching to form multiple first empty foil areas.

[0018] Based on the second aspect, in some embodiments, the adhesive part includes at least one of a single-sided adhesive or a foaming adhesive.

[0019] The third aspect of the present application provides an electronic device, which includes any one of the above secondary batteries, or includes a secondary battery prepared by using the preparation method of any one of the above secondary batteries. Description of the Drawings

[0020] Figure 1 It is a top view of a secondary battery in an embodiment.

[0021] Figure 2 It is a schematic diagram of an electrode assembly in an embodiment.

[0022] Figure 3 It is a cross-sectional view of a secondary battery in an embodiment.

[0023] Figure 4 It is a schematic diagram after the positive electrode tab is flattened and the positive electrode plate is unfolded in an embodiment.

[0024] Figure 5 It is a cross-sectional view of a secondary battery in another embodiment.

[0025] Figure 6 It is a schematic diagram after the negative electrode tab is flattened and the negative electrode plate is unfolded in an embodiment.

[0026] Figure 7 It is a cross-sectional view of a secondary battery in yet another embodiment.

[0027] Figure 8 It is a schematic diagram after coating the active material on the surface of the current collector and forming the first empty foil area in an embodiment.

[0028] Figure 9 For Figure 8 After the current collector shown is cut to form the first electrode plate and the second electrode plate.

[0029] Figure 10 It is a schematic diagram of an electronic device provided in an embodiment of the present application.

[0030] Description of the Main Component Symbols The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. Specific Embodiments

[0031] The following specific embodiments are exemplary rather than restrictive. They are intended to provide a basic understanding of the present application and are not intended to identify the key or decisive elements of the present application or to limit the scope to be protected. As long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way.

[0032] When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be an intermediate component at the same time. When a component is considered to be "connected to" another component, it can be directly connected to the other component or there may be an intermediate component at the same time.

[0033] Unless otherwise defined, the term "a plurality of" in this article, when used to describe the number of components, specifically means that the component is two or more.

[0034] Next, some embodiments of the present application will be described in conjunction with the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0035] Please refer to Figure 1 , an embodiment of the present application provides a secondary battery 100, including a housing 10, an electrode assembly 20 and electrode terminals. The electrode assembly 20 is accommodated in the housing 10, and the electrode terminals are connected to the electrode assembly 20 and extend out of the housing 10 to connect external components. In this example, the number of electrode terminals is two, namely a positive electrode terminal 31 and a negative electrode terminal 32, and the two electrode terminals extend out from the same side of the housing 10. In other embodiments, the number of electrode terminals can be greater than two, and multiple electrode terminals can extend out from different sides of the housing 10.

[0036] Please refer to Figure 2 , the electrode assembly 20 includes wound electrode sheets and a separator 23. The electrode sheets include a positive electrode sheet 21 and a negative electrode sheet 22, and the separator 23 is disposed between the positive electrode sheet 21 and the negative electrode sheet 22. The electrode assembly 20 is formed by winding the positive electrode sheet 21, the separator 23 and the negative electrode sheet 22 in sequence after stacking.

[0037] The positive electrode tab 21 includes a positive electrode current collector 211, a positive electrode active material layer 212, and a plurality of positive electrode tabs 213. The plurality of positive electrode tabs 213 are integrally provided with the positive electrode current collector 211 and are electrically connected to the positive electrode terminal 31. The positive electrode active material layer 212 covers the positive electrode current collector 211, and the positive electrode tabs 213 are exposed outside the positive electrode active material layer 212. The positive electrode active material layer 212 can be provided on one surface or two opposite surfaces of the positive electrode current collector 211 in the thickness direction of the positive electrode current collector 211, and this application does not make any restrictions. The positive electrode current collector 211 can be aluminum foil, aluminum alloy foil, composite current collector, etc. The positive electrode active material layer 212 includes a positive electrode active material, and the positive electrode active material can include one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based material, lithium nickel cobalt aluminate, and their combinations.

[0038] The negative electrode tab 22 includes a negative electrode current collector 221, a negative electrode active material layer 222, and a plurality of negative electrode tabs 223. The plurality of negative electrode tabs 223 are integrally provided with the negative electrode current collector 221 and are electrically connected to the negative electrode terminal 32. The negative electrode active material layer 222 covers the negative electrode current collector 221, and the negative electrode tabs 223 are exposed outside the negative electrode active material layer 222. The negative electrode active material layer 222 can be provided on one surface or two opposite surfaces of the negative electrode current collector 221, and this application does not make any restrictions. The negative electrode current collector 221 can be copper foil, copper alloy foil, composite current collector, etc. The negative electrode active material layer 222 includes a negative electrode active material, and the negative electrode active material can include one or more of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide, silicon-carbon composite, lithium titanate, or a metal that can form an alloy with lithium.

[0039] The separator 23 can be any known separator. For example, the separator 23 can be a thin film made of one or more materials selected from polyethylene, polypropylene, non-woven fabric, and polyfiber.

[0040] Please refer to Figure 3 and Figure 4, along the second direction Y, a plurality of positive electrode tabs 213 are stacked to form a positive electrode tab group 24. The positive electrode tab group 24 includes a first portion 241 and a second portion 242 arranged in sequence along the first direction X. The second direction Y is the thickness direction of the electrode assembly 20, the first direction X is the width direction of the positive electrode plate 21, and the first direction X and the second direction Y are perpendicular to each other. The positive current collector 211 includes a first edge 211A in the first direction X. The first edge 211A and the plurality of positive electrode tabs 213 are located on the same side of the positive current collector 211 in the first direction X. The first portion 241 is bent relative to the positive current collector 211. Along the first direction X, the first portion 241 includes an upper edge 241A and a lower edge 241B arranged oppositely. The first portion 241 is flush with the first edge 211A at the upper edge 241A and is connected to the second portion 242, and the first portion 241 is connected to the positive current collector 211 at the lower edge 241B. The second portion 242 protrudes from the first edge 211A. In the winding direction of the positive electrode plate 21, the first portion 241 is in contact with the positive current collectors 211 located on both sides of the first portion 241. In this application, the winding direction of the positive electrode plate 21 refers to the direction from the winding start end 21A to the winding end 21B of the positive electrode plate 21. The first edge 211A is provided with a plurality of first notches 211A1, and the plurality of first notches 211A1 and the plurality of positive electrode tabs 213 are alternately arranged at intervals along the winding direction of the positive electrode plate 21. When the volume of the secondary battery 100 is fixed, by configuring the first portion 241 with the upper edge 241 flush with the first edge 211A of the positive current collector 211 and in contact with the positive current collectors 211 located on both sides of the first portion 241, the length of the positive current collector 211 along the first direction X can be increased, and then the amount of the positive active material layer 212 covering the positive current collector 211 can be increased, which is beneficial to improving the volume energy density of the secondary battery 100.

[0041] Please refer to Figure 5 and Figure 6, along the second direction Y, a plurality of negative electrode tabs 223 are stacked to form a negative electrode tab group 25. The negative electrode tab group 25 includes a first part 251 and a second part 252 arranged in sequence along the first direction X. The negative electrode current collector 221 includes a first edge 221A in the first direction X. The first edge 221A and the plurality of negative electrode tabs 223 are located on the same side of the negative electrode current collector 221 in the first direction X. The first part 251 is bent relative to the negative electrode current collector 221. Along the first direction X, the first part 251 includes an upper edge 251A and a lower edge 251B arranged oppositely. The first part 251 is flush with the first edge 221A at the upper edge 251A and is connected to the second part 252, and the first part 251 is connected to the negative electrode current collector 221 at the lower edge 251B. The second part 252 protrudes from the first edge 221A. In the winding direction of the negative electrode plate 22, the first part 251 is in contact with the negative electrode current collector 221 located on both sides of the first part 251. In this application, the winding direction of the negative electrode plate 22 refers to the direction from the winding start end 22A to the winding end 22B of the negative electrode plate 22. A plurality of second notches 221A1 are provided on the first edge 221A, and the plurality of second notches 221A1 and the plurality of negative electrode tabs 223 are alternately arranged at intervals along the winding direction of the negative electrode plate 22. When the volume of the secondary battery 100 is fixed, by configuring the first part 251 with the upper edge 251 flush with the first edge 221A of the negative electrode current collector 221 and in contact with the negative electrode current collector 221 located on both sides of the first part 251, the length of the negative electrode current collector 221 along the first direction X can be increased, and further the amount of the negative electrode active material layer 222 covering the negative electrode current collector 221 can be increased, which is beneficial to improving the volume energy density of the secondary battery 100.

[0042] In some embodiments, along the second direction Y, a plurality of first notches 211A1 of the positive electrode plate 21 are stacked to form a first notch group, and a plurality of second notches 221A1 of the negative electrode plate 22 are stacked to form a second notch group. Part of the positive electrode tab group 24 is accommodated in the second notch group, and part of the negative electrode tab group 25 is accommodated in the first notch group, so that the length of the part of the tab group protruding from the edge of the current collector can be reduced, and further the volume energy density of the secondary battery 100 can be improved.

[0043] In some embodiments, please refer to Figure 3 and Figure 5The shell 10 includes a main body 11 and a packaging part. The main body 11 is provided with a accommodating cavity 11A, and the accommodating cavity 11A is used to accommodate the electrode assembly 20, part of the positive terminal 31 and part of the negative terminal 32. The packaging part extends from the main body 11 along at least one side away from the main body 11, and is used to seal the accommodating cavity 11A. The packaging part is a part that is sealed by a process such as hot pressing or bonding after the shell 10 accommodates the electrode assembly 20. Optionally, the shell 10 can adopt a flexible packaging film (such as an aluminum-plastic film, a steel-plastic film), or a hard plastic shell. The packaging part includes a top sealing edge 12, and the top sealing edge 12 extends from the main body 11 along the first direction X. The top sealing edge 12, the first edge 211A of the positive current collector 211 and the second edge 221A of the negative current collector 221 are located on the same side of the secondary battery 100 in the first direction X. The positive terminal 31 and the negative terminal 32 extend out of the shell 10 through the top sealing edge 12. In some embodiments, please refer to Figure 1 The packaging portion further includes a side seal 13 , which extends from the main body 11 and is connected to the top seal 12 . The side seal 13 and the top seal 12 are located on different sides of the main body 11 .

[0044] In some embodiments, see Figure 3 , the main body 11 includes a first surface 111 and a second surface 112 arranged opposite to each other along the second direction Y. The positive electrode tab group 24 includes a first connecting segment 243 and a second connecting segment 244 connected in sequence, and along the first direction X, the first connecting segment 243 is closer to the positive electrode collector 211 than the second connecting segment 244. The first connecting segment 243 extends toward the first surface 111, and the second connecting segment 244 extends toward the top sealing edge 12. One end of the positive terminal 31 is connected to an end of the second connecting segment 244 away from the first connecting segment 243, and the other end of the positive terminal 31 extends out of the shell 10 through the top sealing edge 12 and extends along the first direction X. In some embodiments, the structure of the negative electrode tab group 25 is the same as that of the positive electrode tab group 24, and the structure of the negative terminal 32 is the same as that of the positive terminal 31.

[0045] In some embodiments, see Figure 5 The negative electrode tab group 25 includes a first connecting segment 253, a second connecting segment 254 and a third connecting segment 255 connected in sequence. Along the first direction X, the first connecting segment 253 is closer to the negative electrode current collector 221 than the third connecting segment 255. The first connecting segment 253 extends toward the first surface 111, and the third connecting segment 255 extends toward the second surface 112. One end of the negative terminal 32 is connected to an end of the third connecting segment 255 away from the second connecting segment 254, and the other end of the negative terminal 32 passes through the top sealing edge 12 and extends out of the shell 10 and extends along the first direction X.

[0046] In some embodiments, see Figure 7, the positive electrode tab group 24 includes a first connection segment 243 and a second connection segment 244 connected in sequence. Along the first direction X, the first connection segment 243 is closer to the positive electrode current collector 211 than the second connection segment 244. The first connection segment 243 extends toward the first surface 111, and the second connection segment 244 extends toward the top sealing edge 12. One end of the positive electrode terminal 31 is connected to the end of the second connection segment 244 away from the first connection segment 243, and the other end of the positive electrode terminal 31 passes through the top sealing edge 12 and extends out of the housing 10 and bends toward the electrode assembly 20.

[0047] In some embodiments, referring to Figure 3 , the secondary battery 100 includes a first insulating member 30 disposed on one side of the positive electrode tab group 24. The first insulating member 30 includes a first portion 31. In the first direction X, the first portion 31 is disposed between the positive electrode tab group 24 and the negative electrode current collector 221. The first portion 31 is used to separate the positive electrode tab group 24 and the negative electrode current collector 221 in the first direction X, reducing the risk of short circuit due to contact between the positive electrode tab group 24 and the negative electrode current collector 221, thereby improving the safety performance of the secondary battery 100. In addition, by configuring the first portion 31, the distance between the positive electrode tab group 24 and the negative electrode current collector 221 can be further reduced, which is beneficial to improving the volumetric energy density of the secondary battery 100. In some embodiments, the first portion 31 is disposed between the positive electrode tab group 24 and the positive electrode current collector 211, which is beneficial to reducing the distance between the positive electrode tab group 24 and the positive electrode current collector 211, thereby improving the volumetric energy density of the secondary battery 100.

[0048] In some embodiments, referring to Figure 3 , the first insulating member 30 further includes a second portion 32. The positive electrode tab group 24 and the positive electrode terminal 31 are connected by welding. The second portion 32 covers the connection portion between the positive electrode tab group 24 and the positive electrode terminal 31, thus reducing the risk of short circuit caused by welding burrs.

[0049] In some embodiments, along the second direction Y, the first insulating member 30 overlaps with the positive electrode plate 21 and / or the negative electrode plate 22, so as to increase the contact area between the first insulating member 30 and the electrode assembly 20 and reduce the risk of the first insulating member 30 falling off from the tab group.

[0050] In some embodiments, the first insulating member 30 is further disposed on one side of the negative electrode tab group 25. In the first direction X, the first insulating member 30 is disposed between the negative electrode tab group 25 and the positive current collector 211 and / or the negative current collector 221, which can reduce the distance between the negative electrode tab group 25 and the positive current collector 211 and / or the negative current collector 221, and is beneficial to improving the volumetric energy density of the secondary battery 100. In some embodiments, the negative electrode tab group 25 and the negative terminal 32 are connected by welding, and the first insulating member 30 further covers the connection between the negative electrode tab group 25 and the negative terminal 32 to reduce the risk of short circuit caused by welding burrs.

[0051] In some embodiments, referring to Figure 7 , the secondary battery 100 further includes a second insulating member 40. The second insulating member 40 is disposed on at least one side of the positive electrode tab group 24 and covers at least a part of the first portion 241. In some embodiments, along the second direction Y, the second insulating member 40 is disposed on at least one surface of the positive electrode tab 213. The second insulating member 40 is used to isolate the positive electrode tab 213 and the negative electrode plate 22, and reduce the risk of contact short circuit between the positive electrode tab 213 and the negative electrode plate 22.

[0052] In some embodiments, referring to Figure 4 , the second insulating member 40 includes a first region 41 covering the positive electrode active material layer 212. Along the winding direction of the positive electrode plate 21, the first region 41 is located on both sides of the positive electrode tab 213. Along the winding direction of the positive electrode plate 21, the width range of the first region 41 is 1 mm to 2 mm. For example, the width of the first region 41 is 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm or a range composed of any two of these values. When the width of the first region 41 is within the above range, the risk of contact short circuit between the positive electrode tab 213 and the negative electrode plate 22 can be effectively reduced, and the influence of the second insulating member 40 on the energy density is small.

[0053] In some embodiments, along the first direction X, the length range of the second insulating member 40 is 1.5 mm to 3 mm. For example, the length of the second insulating member 40 is 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 2.8 mm, 3 mm or a range composed of any two of these values. When the length of the second insulating member 40 is within the above range, the risk of contact short circuit between the positive electrode tab 213 and the negative electrode plate 22 can be effectively reduced, and the influence of the second insulating member 40 on the energy density is small.

[0054] In some embodiments, the first insulating member 30 includes an insulating material, which may include at least one of polyethylene, polypropylene, phenolic resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, or polyurethane. In some embodiments, the first insulating member 30 further includes inorganic particles, which may include at least one of boehmite, alumina, silica, and zirconia. In some embodiments, the material of the second insulating member 40 is the same as that of the first insulating member 30.

[0055] In some embodiments, referring to Figure 4 , the depth of the first notch 211A1 in the first direction X is H 1 . In a state where the first portion 241 of the positive electrode tab group 24 is flattened in the first direction X, that is, in a state where the positive electrode tab 213 is flattened in the first direction X, the height of the portion of the positive electrode tab group 24 / positive electrode tab 213 protruding from the first edge 211A of the positive electrode current collector 211 is H 2 . In some embodiments, 0.95 ≤ H 1 / H 2 ≤ 1.05. For example, H 1 / H 2 is 0.95, 0.97, 0.99, 1, 1.02, 1.05, or a range composed of any two of these values. When H 1 / H 2 is within the above range, when preparing the positive electrode sheet 21, the first notch 211A1 and the positive electrode tab 213 can be formed in cooperation, simplifying the manufacturing process.

[0056] In some embodiments, 2 mm ≤ H 1 ≤ 11 mm. For example, H 1 is 2 mm, 4 mm, 6 mm, 8 mm, 11 mm, or a range composed of any two of these values. When the length of the positive electrode sheet 21 in the first direction X is fixed, when H 1 is within the above range, the influence of the reduction in the amount of the positive electrode active material layer 212 caused by the presence of the first notch 211A1 and the first portion 241 of the positive electrode tab group 24 can be made smaller, and the effect of improving the volumetric energy density due to the presence of the first portion 241 of the positive electrode tab group 24 is better. Therefore, the secondary battery 100 has an appropriate volumetric energy density.

[0057] In some embodiments, in a state where the first portion 251 of the negative electrode tab group 25 is flattened in the first direction X, that is, in a state where the negative electrode tab 223 is flattened in the first direction X, the ratio of the depth of the second notch 221A1 in the first direction X to the height of the portion of the negative electrode tab group 25 / negative electrode tab 223 protruding from the first edge 221A of the negative electrode current collector 221 is 0.95 to 1.05.

[0058] One embodiment of the present application provides a method for manufacturing the above secondary battery, including the following steps.

[0059] Step S1, referring to Figure 8 , provide a first current collector 311. The first current collector 311 includes a first surface and a second surface that are oppositely arranged along the thickness direction of the first current collector 311. Continuously coat the active material on the first surface and dry and cold press it to form a first active material layer 312. Continuously coat the active material on the second surface and dry and cold press it to form a second active material layer.

[0060] Step S2, referring to Figure 8 , along the length direction of the first current collector 311, remove a part of the active material at regular intervals to expose the first current collector 311, forming a plurality of first empty foil areas 313. The plurality of first empty foil areas 313 are located in the middle of the first current collector 311 in the first direction X.

[0061] Step S3, referring to Figure 8 and Figure 9 , cut the first current collector 311 along the length direction of the first current collector 311 and the edges of the plurality of first empty foil areas 313. Among them, the edges of the first empty foil areas 313 in the length direction of the first current collector are disconnected from the first current collector 311. After cutting, two pole pieces are formed that are opposite to each other in the first direction X. The two pole pieces include a first pole piece 316 and a second pole piece 317. The edges of the first pole piece 316 and the second pole piece 317 both include a plurality of protrusions 314 and a plurality of notches 315 that are alternately arranged at intervals along the length direction of the pole piece. Along the first direction X, the plurality of protrusions 314 on the first pole piece 316 correspond to the plurality of notches 315 on the second pole piece 317, and the plurality of notches 315 on the first pole piece 316 correspond to the plurality of protrusions 314 on the second pole piece 317. The plurality of protrusions 314 are configured as a plurality of pole ears.

[0062] It can be understood that when the active material coated in step S1 is a positive electrode active material, the first pole piece 316 and the second pole piece 317 obtained in step S3 are positive electrode pole pieces; when the active material coated in step S1 is a negative electrode active material, the first pole piece 316 and the second pole piece 317 obtained in step S3 are negative electrode pole pieces.

[0063] In some embodiments, referring to Figure 8 , the distance between two adjacent ones of the plurality of first empty foil areas 313 is W 1 , along the length direction of the first current collector 311, W 1 increases in sequence. In this way, when the first pole piece 316 or the second pole piece 317 is wound, the plurality of protrusions 314 configured as a plurality of pole ears can overlap in the thickness direction of the secondary battery.

[0064] In some embodiments, along the first direction X, the length of the first empty foil area 313 ranges from 9 mm to 13 mm. For example, the length of the first empty foil area 313 is 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, or a range composed of any two of these values. When the length of the first empty foil area 313 is within the above range, the resulting tab can have an appropriate length, and the resulting notch can have an appropriate depth.

[0065] In some embodiments, the method for removing the active material in step S2 includes: pasting adhesive members at the positions of the plurality of first empty foil areas 313 before coating the active material, and tearing off the adhesive members after coating the active material to remove part of the active material, thereby forming a plurality of first empty foil areas. In some embodiments, the adhesive member includes at least one of a single-sided adhesive or a foaming adhesive.

[0066] In some embodiments, the method for removing the active material in step S2 includes: using laser etching to remove part of the active material after coating the active material, thereby forming a plurality of first empty foil areas 313.

[0067] Please refer to Figure 10 , an embodiment of the present application further provides an electronic device 200, including any one of the above secondary batteries 100 or a secondary battery prepared by the above preparation method. The electronic device of the present application may be, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset stereo, a video recorder, a liquid crystal TV, a hand-held cleaner, a portable CD player, a minidisc, 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, etc.

[0068] The performance of the secondary battery provided by the present application will be described below through specific examples and comparative examples.

[0069] Example 1 Preparation of the positive electrode plate: The positive electrode active material (lithium cobaltate), conductive agent (conductive carbon black and carbon nanotubes), binder (polyvinylidene fluoride) are dissolved in N-methylpyrrolidone solution in a weight ratio of 97.5:1:1.5 to form a positive electrode slurry with a solid content of 75%. Aluminum foil is used as the positive electrode current collector, and the foam glue is bonded to the surface of the positive electrode current collector. The positive electrode slurry is coated on the surface of the positive electrode current collector and the surface of the foam glue by continuous coating, and a positive electrode active material layer with a single-side thickness of 50 μm is obtained after drying and cold pressing steps. Then, the foam glue is removed, and an empty foil area is formed at the position covered by the foam glue. The above steps are repeated on the other surface in the thickness direction of the positive electrode current collector, and the empty foil areas on the two surfaces of the positive electrode current collector overlap each other. After die-cutting, two positive electrode plates symmetrical along the first direction are formed, and each positive electrode plate includes a plurality of positive electrode tabs and a plurality of notches alternately arranged at intervals along the length direction of the positive electrode plate. The structure of each positive electrode plate is as shown in Figure 4 shown.

[0070] Preparation of the negative electrode plate: The negative electrode active material (graphite), conductive agent (conductive carbon black), thickening agent (sodium carboxymethyl cellulose), 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 a negative electrode slurry with a solid content of 50 wt%. Copper foil is used as the negative electrode current collector, and the negative electrode slurry is continuously coated on the surface of the negative electrode current collector, and a negative electrode active material layer with a single-side thickness of 75 μm is obtained after drying and cold pressing steps. The above steps are repeated on the other surface in the thickness direction of the negative electrode current collector. Part of the negative electrode active material is removed by laser etching to obtain an empty foil area, and the empty foil areas on the two surfaces of the negative electrode current collector overlap each other. After die-cutting, two negative electrode plates symmetrical along the first direction are formed, and each negative electrode plate includes a plurality of negative electrode tabs and a plurality of notches alternately arranged at intervals along the length direction of the negative electrode plate. The structure of each negative electrode plate is as shown in Figure 6 shown.

[0071] Preparation of the separator: A polyethylene film is selected as the separator.

[0072] Preparation of the electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), vinylene carbonate (VC) are mixed in a weight ratio of 20:30:20:28:2 to obtain an organic solvent. Then, the fully dried lithium salt LiPF 6 and the organic solvent are mixed in a weight ratio of 8:92 to obtain the electrolyte.

[0073] Preparation of Lithium-Ion Battery: Stack a positive electrode plate, a polyethylene separator, and a negative electrode plate in sequence, with the separator positioned between the positive and negative electrode plates, and wind them to obtain an electrode assembly; provide a positive electrode terminal and a negative electrode terminal, and weld the positive electrode terminal to the positive electrode tab group and the negative electrode terminal to the negative electrode tab group. Place the electrode assembly welded with the electrode terminals into an aluminum-plastic film packaging bag, and thermally press and bond the packaging edge of the bag at a preset pressure and temperature. After injecting electrolyte and forming, a lithium-ion battery is obtained.

[0074] The remaining examples and comparative examples are based on the steps of Example 1 with parameter changes. The specific changed parameters are shown in Table 1. In the comparative examples, the lower edge of the tab coincides with the first edge of the electrode plate, that is, no notch is provided at the edge of the electrode plate. Among them, in each example and comparative example, the length, width, and thickness of the battery are 19.255 mm, 11.9 mm, and 3.94 mm respectively, the width W of the positive electrode tab is 2.4 mm, and the width of the negative electrode tab is 2.4 mm.

[0075] The following describes the test methods for each parameter of this application.

[0076] (1)Volume Energy Density Test: 1) Under the environmental condition of 25 °C, let the secondary battery stand for 10 min, charge it at a constant current of 0.2C to 4.5V, then charge it at a constant voltage until the current is 0.02C, and let it stand for 5 min; then discharge it at a constant current of 0.2C to 3V and let it stand for 5 min, and record the discharge capacity C 0 ; 2) Measure the length, width, and thickness of the secondary battery with a PPG battery thickness measuring instrument, and calculate through the following formula: Volume Energy Density = Plateau Voltage × C 0 / (Length × Width × Thickness).

[0077] (2)High-Voltage Insulation Test (Hipot Test): The Hipot test (High Potential test) refers to an insulation resistance test that measures the resistance between the positive electrode tab and the negative electrode plate to determine whether there is a short circuit.

[0078] The test method is to detect the leakage current generated by the positive tab of the secondary battery under the test voltage of 100V output by the high-voltage machine, and then calculate the resistance value = test voltage / leakage current. Compare the calculated resistance value with the set determination resistance. If the detected resistance value is greater than or equal to the preset value, it is determined that the tested product passes the test (OK); if the detected resistance value is less than the preset value, the test voltage is instantly cut off and the tested product is determined to fail the test (NG). In this test, the preset value of the determination current is 5mΩ. When the resistance value is lower than 5mΩ, it means that it can conduct electricity but the resistance value is too small, there is a short circuit point, and it is determined as NG; when the resistance value is greater than or equal to 5mΩ, it is determined as OK. For each group of examples and comparative examples, 100 battery cells are tested, and the number of battery cells passing the test is X 1 pieces, and the passing rate of the Hipot test is recorded as X 1 / 100.

[0079] (3)Length or width test: Disassemble the lithium-ion battery, take out the electrode sheet, and use a charge-coupled device (CCD) or a ruler to measure the depth H of the notch 1 , the height H of the tab protruding from the first edge in the flattened state 2 , the width of the first area where the second insulating member covers the positive active material layer, and the length of the second insulating member.

[0080] Table 1 Compared with Comparative Example 1, Example 1 has a higher volume energy density by configuring the tab to be partially recessed in the current collector. This is because by recessing the tab in the current collector, the length of the current collector where the active material can be arranged can be increased, thereby increasing the amount of the active material and improving the volume energy density.

[0081] Compared with Example 1, Examples 2 to 10 can reduce the risk of contact short circuit between the positive tab and the negative electrode sheet by configuring the second insulating member, resulting in an increase in the passing rate of the Hipot test.

[0082] In Examples 3 to 5, the width range of the first area where the second insulating member covers the positive active material layer is 1mm to 2mm, having a higher volume energy density and a higher passing rate of the Hipot test. In Example 2, the width of the first area is less than 1mm, and the positive tab and the negative electrode sheet are prone to contact short circuit, resulting in a lower passing rate of the Hipot test. In Example 6, the width of the first area is greater than 2mm, and the second insulating member has a greater impact on the volume energy density, resulting in a smaller volume energy density.

[0083] In Embodiment 4, Embodiment 8, and Embodiment 9, the length of the second insulating member ranges from 1.5 mm to 3 mm, having a relatively high volume energy density and a relatively high passing rate of the Hipot test. In Embodiment 7, the length of the second insulating member is less than 1.5 mm, and the positive electrode tab and the negative electrode plate are likely to come into contact and cause a short circuit, resulting in a relatively low passing rate of the Hipot test. In Embodiment 10, the length of the second insulating member is greater than 3 mm, and the second insulating member has a greater impact on the volume energy density, resulting in a relatively small volume energy density.

[0084] Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to limit the present application. As long as appropriate changes and variations are made to the above embodiments within the scope of the spirit of the present application, they fall within the scope disclosed in the present application.

Claims

1. A secondary battery, comprising an electrode assembly, wherein the electrode assembly comprises a wound pole piece, the pole piece comprises a current collector and a plurality of pole tabs, the plurality of pole tabs are integrally arranged with the current collector, characterized in that: The current collector includes a first edge in a first direction, the first edge and the plurality of pole tabs are located on the same side in the first direction, and the first direction is the width direction of the pole piece; at least some of the plurality of pole tabs include a first portion and a second portion sequentially connected along the extension direction of the pole tab; the first portion includes an upper edge and a lower edge arranged opposite to each other along the extension direction of the pole tab; the upper edge is flush with the first edge in the first direction, and the upper edge is connected to the second portion; the lower edge is connected to the current collector; the first portion is bent relative to the current collector, and the second portion protrudes from the first edge in the first direction; In the winding direction of the pole piece, the first portion contacts the current collectors on both sides of the first portion; the first edge is provided with a plurality of notches, and the plurality of notches and the plurality of pole ears are alternately arranged in the winding direction of the pole piece.

2. The secondary battery according to claim 1, wherein: The electrode sheets include a positive electrode sheet and a negative electrode sheet. Along the second direction, the multiple electrode tabs of the positive electrode sheet are stacked to form a positive electrode tab group, and the multiple notches of the positive electrode sheet are stacked to form a first notch group; along the second direction, the multiple electrode tabs of the negative electrode sheet are stacked to form a negative electrode tab group, and the multiple notches of the negative electrode sheet are stacked to form a second notch group; part of the positive electrode tab group is accommodated in the second notch group, and part of the negative electrode tab group is accommodated in the first notch group; the second direction is the thickness direction of the electrode assembly, and the first direction and the second direction are perpendicular to each other.

3. The secondary battery according to claim 1, wherein: Along the second direction, the multiple tabs are stacked to form a tab group, the second direction is the thickness direction of the electrode assembly, and the first direction and the second direction are perpendicular to each other; the secondary battery includes a first insulating member arranged on one side of the tab group, the first insulating member includes a first part, and in the first direction, the first part is arranged between the tab group and the current collector.

4. The secondary battery according to claim 3, characterized in that: The first insulating member further includes a second portion, the tab group and the electrode terminal are connected by welding, and the second portion covers the connection between the tab group and the electrode terminal.

5. The secondary battery according to claim 1, wherein: The plurality of notches include a first notch, the depth of the first notch in the first direction is H1; when the first portion is flattened along the first direction, the height of the portion of the pole ear protruding from the first edge is H2; 0.95≤H1 / H2≤1.

05.

6. The secondary battery according to claim 5, characterized in that: 2mm≤H1≤11mm.

7. The secondary battery according to claim 2, characterized in that: The secondary battery further includes a second insulating member disposed on at least one side of the positive electrode tab group and covering at least a portion of the first portion.

8. The secondary battery according to claim 7, characterized in that The second insulating member includes a first region covering the positive electrode active material layer, and along the winding direction of the positive electrode sheet, the width of the first region ranges from 1 mm to 2 mm.

9. The secondary battery according to claim 7, characterized in that: Along the first direction, a length of the second insulating member ranges from 1.5 mm to 3 mm.

10. A method for preparing a secondary battery according to any one of claims 1 to 9, characterized in that: include: Providing a first current collector, the first current collector comprising a first surface and a second surface arranged opposite to each other along a thickness direction of the first current collector, continuously coating the first surface with active material, drying, and cold pressing to form a first active material layer, and continuously coating the second surface with active material, drying, and cold pressing to form a second active material layer; Along the length direction of the first current collector, a portion of the active material is removed at a certain interval to expose the first current collector, thereby forming a plurality of first empty foil areas, wherein the plurality of first empty foil areas are located in the middle of the first current collector in the first direction; Cutting the first current collector along the length direction of the first current collector and the edges of the plurality of first empty foil areas, wherein the edges of the first empty foil areas in the length direction of the first current collector are disconnected from the first current collector, and forming two pole pieces opposite to each other along the first direction after cutting, wherein the two pole pieces include a first pole piece and a second pole piece; The edges of the first pole piece and the second pole piece each include a plurality of protrusions and a plurality of notches alternately arranged along the length direction of the pole piece, and along the first direction, the plurality of protrusions on the first pole piece correspond to the plurality of notches on the second pole piece, and the plurality of notches on the first pole piece correspond to the plurality of protrusions on the second pole piece, wherein the plurality of protrusions are configured as the plurality of pole ears.

11. The method for preparing a secondary battery according to claim 10, characterized in that: The distance between two adjacent ones of the plurality of first empty foil areas is W1, and W1 increases sequentially along the length direction of the first current collector.

12. The method for preparing a secondary battery according to claim 10, characterized in that: Along the first direction, the length of the first empty foil area ranges from 9 mm to 13 mm.

13. The method for preparing a secondary battery according to claim 10, characterized in that: The method of removing part of the active material includes any one of the following: (1) before coating the active material, affixing an adhesive to the positions of the plurality of first empty foil areas, and after coating the active material, tearing off the adhesive to remove a portion of the active material, thereby forming the plurality of first empty foil areas; (2) After coating the active material, laser etching is used to remove part of the active material to form the plurality of first empty foil areas.

14. The method for preparing a secondary battery according to claim 13, characterized in that: The adhesive member includes at least one of a single-sided adhesive or a foam adhesive.

15. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 9.

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